Principles of HeatingVentilating

and Air Conditioning

7th Edition

Based on the 2013 ASHRAE HandbookFundamentals

Ronald H. Howell William J. Coad Harry J. Sauer, Jr.

9 781936 50457 2

ISBN: 978-1-936504-57-2

Product Code: 90557 9/13

Principles of H

VA

C 7th E

dition

Principles of Heating, Ventilating, and Air Conditioning is a textbook based on the 2013 ASHRAE HandbookFundamentals. It contains the most current ASHRAE procedures and definitive, yet easy to understand, treatment of building HVAC systems, from basic principles through design and operation.

It is suitable both as a textbook and as a reference book for undergraduate engineering courses in the field of air conditioning, heating, and ventilation; for similar courses at technical and vocational schools; for continuing education and refresher short courses for engineers; and for adult education courses for professionals other than engineers, especially when combined with ASHRAE HandbookFundamentals.

The material is divided into three major sections: general concepts, chapters 110; air-conditioning systems, chapters 1116; and HVAC&R equipment, Chapters 1719. There are several significant changes in this revised edition. Chapter 4 has a new format as well as new values for climatic design information. Chapter 5 has a new table for typical thermal properties (resistance and thermal conductivity) of common building and insulating materials. This includes new values of heating, wind, cooling, and dehumidifying design conditions. Chapter 7 has been extensively revised with new design data. In addition, the chapters on system design and equipment have been significantly revised to reflect recent changes and concepts in modern heating and air-conditioning system practices.

This book includes access to a web site containing the Radiant Time Series (RTS) Method Load Calculation Spreadsheets, which are intended as an educational tool both for the student and for the experienced engineer wishing to explore the RTS method. These spreadsheets allow the user to perform RTS cooling load calculations for lights, people, equipment, walls/roofs, and fenestration components using design day weather profiles for any month. Cooling and heating loads can be calculated for individual rooms or block load zones. Twelve-month cooling calculations can be done to determine the month and time of peak cooling load for each room or block load zone. In addition, room/zone worksheets can be copied and modified within the spreadsheet to analyze as many rooms or zones as desired; the number of rooms/zones is limited only by the available computer memory.

ASHRAE1791 Tullie CircleAtlanta, GA 30329-2305404-636-8400 (worldwide)www.ashrae.org

PHVAC TEXT_cover.indd 1 9/10/2013 9:08:33 AM

PRINCIPLESOF HEATING

VENTILATINGAND

AIR CONDITIONING

ABOUT THE AUTHORS

Ronald H. Howell, PhD, PE, Fellow ASHRAE, retired as professor and chair of mechanical engineering at the Univer-sity of South Florida and is also professor emeritus of the University of Missouri-Rolla. For 45 years he taught coursesin refrigeration, heating and air conditioning, thermal analysis, and related areas. He has been the principal or co-prin-cipal investigator of 12ASHRAE-funded research projects. His industrial and consulting engineering experience rangesfrom ventilation and condensation problems to the development and implementation of a complete air curtain testprogram.

William J. Coad, PE, FellowASHRAE, wasASHRAE president in 2001-2002. He has been withMcClure EngineeringAssociates, St. Louis, Mo., for 45 years and is currently a consulting principal. He is also president of Coad EngineeringEnterprises. He has served as a consultant to theMissouri state government andwas a lecturer inmechanical engineeringfor 12 years and an affiliate professor in the graduate program for 17 years at Washington University, St. Louis. He isthe author of Energy Engineering and Management for Building Systems (Van Nostrand Reinhold).

Harry J. Sauer, Jr., PhD, PE,FellowASHRAE, was a professor ofmechanical and aerospace engineering at theUniver-sity of Missouri-Rolla. He taught courses in air conditioning, refrigeration, environmental quality analysis and control,and related areas. His research ranged from experimental boiling/condensing heat transfer and energy recovery equip-ment for HVAC systems to computer simulations of building energy use and actual monitoring of residential energy use.He served as an advisor to the Missouri state government and has conducted energy auditor training programs for theUS Department of Energy. Dr. Sauer passed away in June 2008.

PRINCIPLESOF HEATING

VENTILATINGAND

AIR CONDITIONING7th Edition

A Textbook with Design Data Based on the2013 ASHRAE HandbookFundamentals

Ronald H. Howell William J. Coad Harry J. Sauer, Jr.

ISBN 978-1-936504-57-2

2013 ASHRAE1791 Tullie Circle, N.E.

Atlanta, GA 30329www.ashrae.org

All rights reserved.

Printed in the United States of America

ASHRAE is a registered trademark in the U.S. Patent and Trademark Office, owned by the American Society of Heating, Refriger-ating and Air-Conditioning Engineers, Inc.

ASHRAE has compiled this publication with care, but ASHRAE has not investigated, and ASHRAE expressly disclaims any dutyto investigate, any product, service, process, procedure, design, or the like that may be described herein. The appearance of anytechnical data or editorial material in this publication does not constitute endorsement, warranty, or guaranty by ASHRAE of anyproduct, service, process, procedure, design, or the like. ASHRAE does not warrant that the information in the publication is freeof errors, and ASHRAE does not necessarily agree with any statement or opinion in this publication. The entire risk of the use ofany information in this publication is assumed by the user.

No part of this book may be reproduced without permission in writing from ASHRAE, except by a reviewer who may quote briefpassages or reproduce illustrations in a review with appropriate credit; nor may any part of this book be reproduced, stored in aretrieval system, or transmitted in any way or by any meanselectronic, photocopying, recording, or otherwithout permission inwriting fromASHRAE.

Howell, Ronald H. (Ronald Hunter), 1935-Principles of heating ventilating and air conditioning : a textbook with design data based on the 2013 ASHRAE handbook

fundamentals / Ronald H. Howell, William J. Coad, Harry J. Sauer, Jr. -- 7th edition.pages cm

Some editions have Sauer's name first.Includes bibliographical references and index.Summary: "A textbook with design data based on the 2013 ASHRAE handbook of fundamentals"-- Provided by publisher.ISBN 978-1-936504-57-2 (hardcover : alk. paper)1. Heating--Textbooks. 2. Ventilation--Textbooks. 3. Air conditioning--Textbooks. I. Coad, William J. II. Sauer, Harry J., Jr.,1935- III. Title.

TH7012.H73 2013697--dc23

2013036759

ASHRAE Staff Special Publications Mark S. Owen, Editor/Group Manager of Handbook and Special PublicationsCindy Sheffield Michaels, Managing EditorJames Madison Walker, Associate EditorRoberta Hirschbuehler, Assistant EditorSarah Boyle, Editorial AssistantMichshell Phillips, Editorial Coordinator

Publishing Services David Soltis, Group Manager of Publishing Services andElectronic CommunicationsJayne Jackson, Publication Traffic AdministratorTracy Becker, Graphics Specialist

Publisher W. Stephen Comstock

CONTENTS

Part I General Concepts

Chapter 1 BackgroundIntroduction........................................................................................................... 1Historical Notes .................................................................................................... 2Building Energy Use............................................................................................. 5Conceptualizing an HVAC System ...................................................................... 7Sustainability and Green Buildings ...................................................................... 7Problems ............................................................................................................... 8Bibliography ......................................................................................................... 9

Chapter 2 Thermodynamics and PsychrometricsFundamental Concepts and Principles................................................................ 11Properties of a Substance .................................................................................... 13Forms of Energy ................................................................................................. 36First Law of Thermodynamics............................................................................ 40Second Law of Thermodynamics ....................................................................... 42Third Law of Thermodynamics .......................................................................... 44Basic Equations of Thermodynamics ................................................................. 44Thermodynamics Applied to Refrigeration ........................................................ 44Applying Thermodynamics to Heat Pumps........................................................ 49Absorption Refrigeration Cycle.......................................................................... 49Problems ............................................................................................................. 50Bibliography ....................................................................................................... 55SI Tables and Figures.......................................................................................... 55

Chapter 3 Basic HVAC System CalculationsApplying Thermodynamics to HVAC Processes ............................................... 67Single-Path Systems ........................................................................................... 72Air-Volume Equations for Single-Path Systems ................................................ 72Psychrometric Representation of Single-Path Systems ...................................... 74Sensible Heat Factor (Sensible Heat Ratio)........................................................ 74Problems ............................................................................................................. 76Bibliography ....................................................................................................... 80

Chapter 4 Design ConditionsIndoor Design Conditions ................................................................................... 81Outdoor Design Conditions: Weather Data ........................................................ 89Other Factors Affecting Design ........................................................................ 136Temperatures in Adjacent Unconditioned Spaces ............................................ 140Problems ........................................................................................................... 141Bibliography ..................................................................................................... 142SI Tables and Figures........................................................................................ 143

Chapter 5 Load Estimating FundamentalsGeneral Considerations..................................................................................... 145Outdoor Air Load Components ........................................................................ 146Heat-Transfer Coefficients................................................................................ 158Calculating Surface Temperatures.................................................................... 169Problems ........................................................................................................... 173

Bibliography ..................................................................................................... 176SI Figures and Tables........................................................................................ 177

Chapter 6 Residential Cooling and Heating Load CalculationsBackground ....................................................................................................... 189General Guidelines............................................................................................ 190Cooling Load Methodology.............................................................................. 195Heating Load Methodology .............................................................................. 198Nomenclature.................................................................................................... 204Load Calculation Example................................................................................ 205Problems ........................................................................................................... 207Bibliography ..................................................................................................... 210SI Figures and Tables........................................................................................ 211

Chapter 7 Nonresidential Cooling and Heating Load CalculationsPrinciples........................................................................................................... 217Initial Design Considerations............................................................................ 221Heat Gain Calculation Concepts....................................................................... 221Description of Radiant Time Series (RTS)....................................................... 247Cooling Load Calculation Using RTS .............................................................. 249Heating Load Calculations................................................................................ 250Design Loads Calculation Example.................................................................. 252Problems ........................................................................................................... 266Bibliography ..................................................................................................... 269SI Figures and Tables........................................................................................ 274

Chapter 8 Energy Estimating MethodsGeneral Considerations..................................................................................... 289Component Modeling and Loads...................................................................... 290Overall Modeling Strategies ............................................................................. 291Integration of System Models........................................................................... 292Degree-Day Methods ........................................................................................ 293Bin Method (Heating and Cooling) .................................................................. 302Problems ........................................................................................................... 304Bibliography ..................................................................................................... 308

Chapter 9 Duct and Pipe SizingDuct Systems .................................................................................................... 309Fans ................................................................................................................... 346Air-Diffusing Equipment .................................................................................. 354Pipe, Tube, and Fittings .................................................................................... 356Pumps................................................................................................................ 361Problems ........................................................................................................... 363References......................................................................................................... 367SI Figures and Tables........................................................................................ 369

Chapter 10 Economic Analyses and Life-Cycle CostsIntroduction....................................................................................................... 377Owning Costs.................................................................................................... 377Service Life....................................................................................................... 377Depreciation...................................................................................................... 380Interest or Discount Rate .................................................................................. 380Periodic Costs ................................................................................................... 380Operating Costs................................................................................................. 381

Economic Analysis Techniques........................................................................ 385Reference Equations ......................................................................................... 388Problems ........................................................................................................... 388Symbols ............................................................................................................ 389References......................................................................................................... 390Bibliography ..................................................................................................... 390

Part II HVAC Systems

Chapter 11 Air-Conditioning System ConceptsSystem Objectives and Categories.................................................................... 391System Selection and Design............................................................................ 392Design Parameters ............................................................................................ 392Performance Requirements............................................................................... 393Focusing on System Options ............................................................................ 393Narrowing the Choice ....................................................................................... 394Energy Considerations of Air Systems ............................................................. 395Basic Central Air-Conditioning and Distribution System ................................ 396Smoke Management.......................................................................................... 398Components ...................................................................................................... 398Air Distribution................................................................................................. 401Space Heating ................................................................................................... 403Primary Systems ............................................................................................... 403Space Requirements.......................................................................................... 405Problems ........................................................................................................... 408Bibliography ..................................................................................................... 410

Chapter 12 System ConfigurationsIntroduction....................................................................................................... 411Selecting the System......................................................................................... 412Multiple-Zone Control Systems........................................................................ 412Ventilation and Dedicated Outdoor Air Systems (DOAS) ............................... 415All-Air System with DOAS Unit...................................................................... 416Air-and-Water Systems with DOAS Unit......................................................... 416In-Space Temperature Control Systems ........................................................... 416Problems ........................................................................................................... 422Bibliography ..................................................................................................... 425

Chapter 13 Hydronic Heating and Cooling System DesignIntroduction....................................................................................................... 427Closed Water Systems ...................................................................................... 428Design Considerations ...................................................................................... 436Design Procedures ............................................................................................ 444Problems ........................................................................................................... 447Bibliography ..................................................................................................... 448

Chapter 14 Unitary and Room Air ConditionersUnitary Air Conditioners .................................................................................. 449Combined Unitary and Dedicated Outdoor Air Systems.................................. 451Window Air Conditioners................................................................................. 451Through-the-Wall Conditioner System............................................................. 452Typical Performance......................................................................................... 453Minisplits, Multisplits, and Variable-Refrigerant-Flow (VRF) Systems.......... 453Water-Source Heat Pumps................................................................................ 454

Problems ........................................................................................................... 455Bibliography ..................................................................................................... 455

Chapter 15 Panel Heating and Cooling SystemsGeneral.............................................................................................................. 457Types................................................................................................................. 458Design Steps...................................................................................................... 460Problems ........................................................................................................... 461Bibliography ..................................................................................................... 461

Chapter 16 Heat Pump, Cogeneration, and Heat Recovery SystemsGeneral.............................................................................................................. 463Types of Heat Pumps ........................................................................................ 463Heat Sources and Sinks..................................................................................... 465Cogeneration ..................................................................................................... 468Heat Recovery Terminology and Concepts ...................................................... 469Heat Recovery Systems .................................................................................... 471Problems ........................................................................................................... 474Bibliography ..................................................................................................... 474SI Figures .......................................................................................................... 474

Part III HVAC Equipment

Chapter 17 Air-Processing EquipmentAir-Handling Equipment .................................................................................. 477Cooling Coils .................................................................................................... 477Heating Coils .................................................................................................... 482Evaporative Air-Cooling Equipment ................................................................ 483Air Washers ...................................................................................................... 484Dehumidification .............................................................................................. 484Humidification .................................................................................................. 486Sprayed Coil Humidifiers/Dehumidifiers ......................................................... 488Air Cleaners ...................................................................................................... 488Air-to-Air Energy Recovery Equipment........................................................... 493Economizers...................................................................................................... 500Problems ........................................................................................................... 500Bibliography ..................................................................................................... 502SI Table............................................................................................................. 503

Chapter 18 Refrigeration EquipmentMechanical Vapor Compression....................................................................... 505Absorption Air-Conditioning and Refrigeration Equipment ............................ 523Cooling Towers................................................................................................. 529Problems ........................................................................................................... 532Bibliography ..................................................................................................... 533SI Tables ........................................................................................................... 534

Chapter 19 Heating EquipmentFuels and Combustion ...................................................................................... 537Burners.............................................................................................................. 540Residential Furnaces ......................................................................................... 541Commercial Furnaces ....................................................................................... 543Boilers ............................................................................................................... 546Terminal Units .................................................................................................. 548

PREFACEPrinciples of Heating, Ventilating, and Air Conditioning, a textbook based on the 2013

ASHRAE HandbookFundamentals, should provide an attractive text for air-conditioningcourses at engineering colleges and technical institutes. The text has been developed to give broadand current coverage of the heating, ventilation, and air-conditioning field when combined withthe 2013 ASHRAE HandbookFundamentals.

The book should prove most suitable as a textbook and subsequent reference book for (a)undergraduate engineering courses in the general field of HVAC, (b) similar courses at technicalinstitutes, (c) continuing education and refresher short courses for engineers, and (d) adult educa-tion courses for nonengineers. It contains more material than can normally be covered in a one-semester course. However, several different single-semester or shorter courses can be easilyplanned by merely eliminating the chapters and/or parts that are least applicable to the objectivesof the particular course. This text will also readily aid in self-instruction of the 2013 ASHRAEHandbookFundamentals by engineers wishing to develop their competence in the HVAC&Rfield.

Although numerous references are made to the other ASHRAE Handbook volumes, sufficientmaterial has been included from these to make this text complete enough for various courses inthe HVAC&R field. The material covered for various audiences in regular university courses,technical institute courses, and short courses can and will vary greatly. This textbook needed to becomplete to satisfy all of these anticipated uses and needs. Toward this end, the following majorsections are included:

Part I General Concepts, Chapters 110

Part II Air-Conditioning Systems, Chapters 1116

Part III HVAC&R Equipment, Chapters 1720

Although the 2013 ASHRAE HandbookFundamentals is published in an SI edition, whichuses international units, and an inch-pound (I-P) edition, this single version of Principles of Heat-ing, Ventilating, and Air Conditioning is designed to serve the I-P edition with some SI inter-spersed throughout.

There are several significant changes in this edition. Chapter 4 has a new format as well as newvalues for climatic design information. Chapter 7 has been extensively revised with new designdata. These changes make Principles compatible with the 2013 ASHRAE HandbookFundamen-tals. In addition, the chapters on system design and equipment have been significantly revised toreflect recent changes and concepts in contemporary heating and air-conditioning system prac-tices, and Chapter 10 has been significantly rewritten to reflect methodologies, techniques, andanalyses as presented in the current Chapter 37 of the 2011 ASHRAE HandbookApplications.Also, the Solutions Manual has been extensively edited.

A particular point of confusion must be pointed out. Because this book was developed to beused with the ASHRAE Handbooks Fundamentals volume, a number of tables and figures havebeen reproduced in the original form, complete with references to material elsewhere in Funda-mentals (not in this book). Thus, if the subheading in the table or figure indicates that it is a Fun-damentals table or figure, then all references to other locations, equations, tables, etc., refer tothose in Fundamentals, not in Principles.

Dr. Harry Sauer, Jr., one of the co-authors of this textbook, passed away in June 2008. Dr.Sauers name still appears as a co-author, because he made significant contributions to Principles.

September 2013 Ronald H. HowellWilliam J. Coad

Chapter 1

BACKGROUND

This chapter provides a brief background on the heating, ventilating, air-conditioning, and refrigeration (HVAC&R)field and industry, including the early history and some significant developments.An introduction to a few basic conceptsis included along with suggestions for further reading.

1.1 Introduction

On the National Academy of Engineerings list of engi-neering achievements that had the greatest impact on thequality of life in the 20th century, air conditioning andrefrigeration came in tenth, indicating the great significanceof this field in the world. With many people in the UnitedStates spending nearly 90% of their time indoors, it is hardlysurprising that providing a comfortable and healthy indoorenvironment is a major factor in life today. In fact, over $33billion of air-conditioning equipment was sold in the US dur-ing the year 2010 alone.

Air-conditioning systems usually provide year-roundcontrol of several air conditions, namely, temperature,humidity, cleanliness, and air motion. These systems mayalso be referred to as environmental control systems,although today they are usually called heating, ventilating,and air-conditioning (HVAC) systems.

The primary function of an HVAC system is either (1) thegeneration and maintenance of comfort for occupants in aconditioned space; or (2) the supplying of a set of environ-mental conditions (high temperature and high humidity, lowtemperature and high humidity, etc.) for a process or productwithin a space. Human comfort design conditions are quitedifferent from conditions required in textile mills or for grainstorage and vary with factors such as time of year and theactivity and clothing levels of the occupants.

If improperly sized equipment or the wrong type of equip-ment is used, the desired environmental conditions usuallywill not be met. Furthermore, improperly selected and/orsized equipment normally requires excess power and/orenergy and may have a higher initial cost. The design of anHVAC system includes calculation of the maximum heatingand cooling loads for the spaces to be served, selection of thetype of system to be used, calculation of piping and/or ductsizes, selection of the type and size of equipment (heatexchangers, boilers, chillers, fans, etc.), and a layout of thesystem, with cost, indoor air quality, and energy conservationbeing considered along the way. Some criteria to be consid-ered are

Temperature, humidity, and space pressure requirements Capacity requirements Equipment redundancy

Spatial requirements First cost Operating cost Maintenance cost Reliability Flexibility Life-cycle cost analysis

The following details should be considered to properlydesign an air-conditioning system:

1. The location, elevation, and orientation of the structureso that the effects of the weather (wind, sun, and precip-itation) on the building heating and cooling loads can beanticipated.

2. The building size (wall area, roof area, glass area, floorarea, and so forth).

3. The building shape (L-shaped, A-shaped, rectangular,etc.), which influences equipment location, type of heat-ing and cooling system used, and duct or piping loca-tions.

4. The space use characteristics. Will there be differentusers (office, bank, school, dance studios, etc.) of thespace from year to year? Will there be different concur-rent requirements from the tenants? Will there be nightsetback of the temperature controller or intermittent useof the buildings facilities?

5. The type of material (wood, masonry, metal, and so forth)used in the construction of the building. What is theexpected quality of the construction?

6. The type of fenestration (light transmitting partition)used, its location in the building, and how it might beshaded. Is glass heat absorbing, reflective, colored, etc.?

7. The types of doors (sliding, swinging, revolving) andwindows (sealed, wood or metal frames, etc.) used.Whatis their expected use? This will affect the amount of infil-tration air.

8. The expected occupancy for the space and the timeschedule of this occupancy.

9. Type and location of lighting. Types of appliances andelectrical machinery in the space and their expected use.

10. Location of electric, gas, and water services. These ser-vices should be integrated with the locations of the heat-ing and air-conditioning duct, piping, and equipment.

2 Principles of HVAC

11. Ventilation requirements for the structure. Does it require100% outdoor air, a given number of CFM per person, ora given number of CFM per square foot of floor area?

12. Local and/or national codes relating to ventilation, gas,and/or electric piping.

13. Outside design temperatures and wind velocities for thelocation.

14. The environmental conditions that are maintained. Willfluctuations of these conditions with load be detrimentalto the purpose served by the structure?

15. The heating and cooling loads (also consider themoistureload, air contaminants, and noise).

16. The type of heating and cooling system to be used in thestructure. Is it forced air, circulated water, or directexpansion? Will it be a multizone, single zone, reheat,variable air volume, or another type of system? Whatmethod of control will be used?Will a dedicated outdoorair system be considered?

17. The heating and cooling equipment size that will main-tain the inside design conditions for the selected outsidedesign condition. Electric heat or fossil fuel? Mechanicalvapor compression or absorption chiller?

18. The advantages and disadvantages of oversizing andundersizing the equipment as applied to the structure.Survey any economic tradeoffs to be made. Should a dif-ferent type of unit be installed in order to reduce operat-ing costs? Should a more sophisticated control system beused to give more exact control of humidity and temper-ature or should an on-off cycle be used? Fuel economy asrelated to design will become an even more importantfactor in system selection and operation.

19. What is the estimated annual energy usage?

In general, no absolute rules dictate correct selections orspecifications for each of the above items, so only engineeringestimates or educated guesses can be made. However, esti-mates must be based on sound fundamental principles andconcepts. This book presents a basic philosophy of environ-mental control as well as the basic concepts of design. Theseideas relate directly to the ASHRAE Handbook series: 2010Refrigeration, 2011HVACApplications, 2012HVAC Systemsand Equipment, and most directly to 2013 Fundamentals.

1.2 Historical Notes

Knowing something of the past helps in understanding cur-rent design criteria and trends.As in other fields of technology,the accomplishments and failures of the past affect current andfuture design concepts. The following paragraphs consistmainly of edited excerpts from ASHRAE Journal articles: AHistory of Heating by John W. James, The History ofRefrigeration by Willis R. Woolrich, and Milestones in AirConditioning by Walter A. Grant, with additional informa-tion obtained from ASHRAEs Historical Committee. Theseexcerpts provide a synopsis of the history of environmentalcontrol.

Obviously, the earliest form of heating was the openfire. The addition of a chimney to carry away combustionbyproducts was the first important step in the evolution ofheating systems. By the time of the Romans, there wassufficient knowledge of ventilation to allow for the instal-lation of ventilating and panel heating in baths. Leonardoda Vinci had invented a ventilating fan by the end of the15th century. Robert Boyles law was established in 1659;John Daltons in 1800. In 1775, Dr. William Cullen madeice by pumping a vacuum in a vessel of water. A few yearslater, Benjamin Franklin wrote his treatise on Pennsylva-nia fireplaces, detailing their construction, installation, andoperation.

Although warming and ventilating techniques had greatlyimproved by the 19th century, manufacturers were unable toexploit these techniques because

Data available on such subjects as transmission coeffi-cients, air and water friction in pipes, and brine and ammo-nia properties were sparse and unreliable.

Neither set design conditions nor reliable psychrometriccharts existed.

A definitive rational theory that would permit performancecalculation and prediction of results had not yet been devel-oped.

Little was known about physical, thermodynamic, and fluiddynamic properties of air, water, brines, and refrigerants.

No authoritative information existed on heat transmissioninvolving combustion, conduction, convection, radiation,evaporation, and condensation.

No credible performance information for manufacturedequipment was available.

Thanks to Thomas Edison, the first electric power plantopened in NewYork in 1882, making it possible for the firsttime to have an inexpensive source of energy for residentialand commercial buildings.

1.2.1 Furnaces

By 1894, the year the American Society of Heating andVentilating Engineers (ASH&VE) was born, central heatingwas fairly well developed. The basic heat sources were warmair furnaces and boilers. The combustion chambers of the firstwarm air furnaces were made of cast iron. Circulation in agravity warm air furnace system is caused by the difference inair density in the many parts of the system. As the force ofcombustion is small, the system was designed to allow air tocirculate freely. The addition of fans (circa 1899) to furnacesystems provided a mechanical means of air circulation.Other additions to the modern furnace include cooling sys-tems, humidification apparatuses, air distributors, and air fil-ters. Another important step for the modern heating industrywas the conversion of furnaces from coal to oil and gas, andfrom manual to automatic firing.

Background 3

1.2.2 Steam SystemsJames Watt developed the first steam heating system in

1770. However, the first real breakthrough in design did notoccur until the early 1900s when circulation problems inthese systems were improved with the introduction of a fluid-operated thermostatic trap.

From 1900 to 1925, two-pipe steam systems with thermo-static traps at the outlet of each radiator and at drip points in thepiping gained wide acceptance. In smaller buildings, gravitysystems were commonly installed to remove condensate. Forlarger systems, boiler return traps and condensate pumps withreceivers were used. By 1926, the vacuum return line systemwas perfected for installation in large and moderate-sizedbuildings.

Hot water heating systems were developed in parallelwith steam systems. As mentioned before, the first hot waterheating system was the gravity system. In 1927, the circula-tor, which forced water through the system, was added totwo-pipe heating systems. A few years later, a diverting teewas added to the one-pipe system, allowing for forced circu-lation.

During the 1930s, radiators and convectors were com-monly concealed by enclosures, shields, and cabinets. In 1944,the baseboard radiator was developed. Baseboard heatingimproved comfort conditions as it reduced floor-to-ceilingtemperature stratification.

Unit heaters and unit ventilators are two other forms ofconvection heating developed in the 1920s. Unit heaterswere available in suspended and floor types and were clas-sified according to the heating medium used (e.g., steam,hot water, electricity, gas, oil, or coal combustion). In addi-tion to the heating element and fan, unit ventilators wereoften equipped with an air filter. Many designs provided airrecirculation and were equipped with a separate outdoor airconnection.

Panel heating, another form of heat distribution, wasdeveloped in the 1920s. In panel heating, a fluid such as hotwater, steam, air, or electricity, circulates through distribu-tion units embedded in the building components.

1.2.3 Early RefrigerationEarly forms of refrigeration included the use of snow, pond

and lake ice, chemical mixture cooling to form freezing baths,and the manufacture of ice by evaporative and radiation cool-ing of water on clear nights.

By the 18th century, certain mixtures were known to lowertemperatures. One such mixture, calcium chloride and snow,was introduced for commercial use. This particular mixturemade possible a temperature down to 27F (33C). In GreatBritain, machines using chemical mixtures to produce lowtemperatures were introduced. However, by the time thesemachines were ready for commercial exploitation, mechani-cal ice-making processes had been perfected to such an extentthat chemical mixture freezing was rendered obsolete exceptfor such batch processes as ice cream making.

1.2.4 Mechanical and Chemical RefrigerationIn 1748, in Scotland, Dr.William Cullen and Joseph Black

lectured on the latent heat of fusion and evaporation andfixed air (later identified as carbon dioxide). These discov-eries served as the foundation on which modern refrigerationis based.

In 1851, Dr. John Gorrie, was granted US Patent No. 8080for a refrigeration machine that produced ice and refrigeratedair with compressed air in an open cycle. Also in 1851, Fer-dinand Carre designed the first ammonia absorption unit.

In 1853, Professor Alexander Twining of New Haven,Connecticut, produced 1600 lb of ice a day with a doubleact-ing vacuum and compression pump that used sulfuric ether asthe refrigerant.

Daniel L. Holden improved the Carre machine by design-ing and building reciprocating compressors. These compres-sors were applied to ice making, brewing, and meat packing.In 1872, David Boyle developed an ammonia compressionmachine that produced ice.

Until 1880, mechanical refrigeration was primarily used tomake ice and preserve meat and fish. Notable exceptions werethe use of these machines in the United States, Europe, andAustralia for beer making, oil dewaxing, and wine cooling.Atthis time, comfort air cooling was obtained by ice or by chill-ing machines that used either lake or manufactured ice.

1.2.5 History of ASHRAETheAmerican Society of Heating andVentilating Engineers

(ASHVE) was formed in NewYork City in 1894 to conduct re-search, develop standards, hold technical meetings, and publishtechnical articles in journals and handbooks. Its scope was lim-ited to the fields of heating and ventilating for commercial andindustrial applications, with secondary emphasis on residentialheating. Years later the Societys name was changed to theAmerican Society of Heating and Air-Conditioning Engineers(ASHAE) to recognize the increasing importance of air condi-tioning.

In 1904, the American Society of Refrigerating Engineers(ASRE) was organized and headquartered at the AmericanSociety of Mechanical Engineers (ASME). The new Societyhad 70 charter members and was the only engineering groupin the world that confined its activities to refrigeration, whichat that time consisted mainly of ammonia systems.

In 1905, ASME established 288,000 Btu in 24 hrs as thecommercial ton of refrigeration (within the United States). Inthe same year, the NewYork Stock Exchange was cooled byrefrigeration. In 1906, Stuart W. Cramer coined the term airconditioning.

The First International Congress on Refrigeration wasorganized in Paris in 1908 and a delegation of 26 was sentfrom the United States. Most of the participants were mem-bers of ASRE.

ASHAE and ASRE merged in 1959, creating the Ameri-can Society of Heating, Refrigerating and Air-ConditioningEngineers.

4 Principles of HVAC

Figure 1-1 depicts ASHRAEs history. ASHRAE cele-brated its Centennial Year during society year 1994-1995. Incommemoration of the centennial, two books on the history ofASHRAE and of the HVAC industry were published, Pro-claiming the Truth and Heat and Cold: Mastering the GreatIndoors.

Figure 1-1 Background of ASHRAE

1.2.6 Willis H. CarrierWillis H. Carrier (1876-1950) has often been referred to as

the Father of Air Conditioning. His analytical and practicalaccomplishments contributed greatly to the development ofthe refrigeration industry.

Carrier graduated fromCornell University in 1901 andwasemployed by the Buffalo Forge Company. He realized thatsatisfactory refrigeration could not be installed due to theinaccurate data that were available. By 1902, he developedformulas to optimize forced-draft boiler fans, conducted testsand developed multirating performance tables on indirectpipe coil heaters, and set up the first research laboratory in theheating and ventilating industry.

In 1902, Carrier was asked to solve the problem faced by thelithographic industry of poor color register caused by weatherchanges. Carriers solution was to design, test, and install at theSackett-Wilhelms Lithographing Company of Brooklyn a sci-entifically engineered, year-round air-conditioning system thatprovided heating, cooling, humidifying, and dehumidifying.

By 1904, Carrier had adapted atomizing nozzles and devel-oped eliminators for air washers to control dew-point temper-ature by heating or cooling a systems recirculated water.Soon after this development, over 200 industries were usingyear-round air conditioning.

At the 1911 ASME meeting, Carrier presented his paper,Rational Psychrometric Formulae, which related dry-bulb,wet-bulb, and dew-point temperatures of air, as well as its

sensible, latent, and total heat load, and set forth the theory ofadiabatic saturation. The formulas and psychrometric chartpresented in this paper became the basis for all fundamentalcalculations used by the air-conditioning industry.

By 1922, Carriers centrifugal refrigeration machine,together with the development of nonhazardous, low-pressurerefrigerants, made water chilling for large and medium-sizecommercial and industrial applications both economical andpractical. A conduit induction system for multiroom build-ings, was invented in 1937 by Carrier and his associate, Car-lyle Ashley.

1.2.7 Comfort Cooling

Although comfort air-cooling systems had been built as ofthe 1890s, no real progress was made in mechanical air cool-ing until after the turn of the century. At that time, several sci-entifically designed air-conditioning plants were installed inbuildings. One such installation included a theater in Cologne,Germany. In 1902, Alfred Wolff designed a 400-ton systemfor the NewYork Stock Exchange. Installed in 1902, this sys-tem was in operation for 20 years. The Boston Floating Hos-pital, in 1908, was the first hospital to be equipped withmodern air conditioning. Mechanical air cooling was installedin a Texas church in 1914. In 1922, Graumans MetropolitanTheater, the first air-conditioned movie theater, opened in LosAngeles. The first office building designed with and built forcomfort air-conditioning specifications was the Milam Build-ing, in San Antonio, Texas, which was completed in 1928.Also in 1928, the Chamber of the House of Representativesbecame air conditioned. The Senate became air conditionedthe following year and in 1930, theWhite House and the Exec-utive Office Building were air-conditioned.

The system of air bypass control, invented in 1924 by L.Logan Lewis, solved the difficult problem of humidity controlunder varying load. By the end of the 1920s, the first room airconditioner was introduced by Frigidaire. Other importantinventions of the 1920s include lightweight extended surfacecoils and the first unit heater and cold diffuser.

ThomasMidgley, Jr. developed the halocarbon refrigerantsin 1930. These refrigerants were found to be safe and eco-nomical for the small reciprocating compressors used in com-mercial and residential markets. Manufacturers were soonproducing mass market room air conditioners that usedRefrigerant 12.

Fluorinated refrigerants were also applied to centrifugalcompression, which required only half the number of impel-lers for the same head as chlorinated hydrocarbons. Space andmaterials were saved when pressure-formed extended-surfacetubes in shell-and-tube exchangers were introduced byWalterJones. This invention was an important advance for centrifu-gal and reciprocating equipment.

Other achievements of the 1930s included

The first residential lithium bromide absorption machinewas introduced in 1931 by Servel.

Background 5

In 1931, Carrier marketed steam ejector cooling units forrailroad passenger cars.

As of the mid-1930s, General Electric introduced the heatpump; the electrostatic air cleaner was put out by Westing-house; Charles Neeson of Airtemp invented the high-speedradial compressor; and W.B. Connor discovered that odorscould be removed by using activated carbon.

With the end ofWorldWar II, air-conditioning technologyadvanced rapidly. Among the advances were air-source heatpumps, large lithium-bromide water chillers, automobile airconditioners, rooftop heating and cooling units, small, out-door-installed ammonia absorption chillers, air purifiers, avapor cycle aircraft cabin cooling unit, and a large-capacityLysholm rotary compressor.

Improvements on and expansions of products that alreadyexisted include

Dual-duct central systems for office buildings Change from open to hermetic compressors from the small-est reciprocating units to large-capacity centrifugals

Resurgence of electric heating in all kinds of applications Use of heat pumps to reclaim heat in large buildings Application of electrostatic cleaners to residences Self-contained variable volume air terminals for multipleinterior rooms

Increasing use of total energy systems for large buildingsand clusters of buildings

Larger sizes of centrifugals, now over 5000 tons in a singleunit

Central heating and cooling plants for shopping centers,colleges, and apartment and office building complexes

In the late 1940s and into the early 1950s, developmentwork continued on unitary heat pumps for residential andsmall commercial installations. These factory-engineered andassembled units, like conventional domestic boilers, could beeasily and cheaply installed in the home or small commercialbusinesses by engineers. In 1952, heat pumps were placed onthe market for mass consumption. Early heat pumps lackedthe durability needed to withstand winter temperatures. Lowwinter temperatures placed severe stress on the componentsof these heat pumps (compressors, outdoor fans, reversingvalves, and control hardware). Improvements in the design ofheat pumps has continued, resulting in more-reliable com-pressors and lubricating systems, improved reversing valves,and refined control systems.

In the 1950s came the rooftop unit for commercial build-ings. Multizone packaged rooftop units were popular duringthe 1960s; however, most were very energy inefficient andlost favor during the 1970s. Beginning with the oil embargo of1973, the air-conditioning field could no longer conductbusiness as usual, with concern mainly for the initial cost ofthe building and its conditioning equipment. The use of cruderules of thumb, which significantly oversized equipment andwasted energy, was largely replaced with reliance upon morescientifically sound, and often computer-assisted, design,

sizing, and selection procedures. Variable air volume (VAV)designs rapidly became the most popular type of HVACsystem for offices, hospitals, and some school buildings.Although energy-efficient, VAV systems proved to have theirown set of problems related to indoor air quality (IAQ), sickbuilding syndrome (SBS), and building related illness (BRI).Solutions to these problems are only now being realized.

In 1987, the United Nations Montreal Protocol for protect-ing the earths ozone layer was signed, establishing the phase-out schedule for the production of chlorofluorocarbon (CFC)and hydrochlorofluorocarbon (HCFC) refrigerants. Contem-porary buildings and their air-conditioning equipment mustnow provide improved indoor air quality as well as comfort,while consuming less energy and using alternative refriger-ants.

1.3 Building Energy Use

Energy is generally used in buildings to perform functionsof heating, lighting, mechanical drives, cooling, and specialapplications. A typical breakdown of the relative energy usein a commercial building is given as Figure 1-2.

Figure 1-2 Energy Use in a Commercial Building

Energy is available in limited forms, such as electricity,fossil fuels, and solar energy, and these energy forms must beconverted within a building to serve the end use of the variousfunctions.A degradation of energy is associated with any con-version process. In energy conservation efforts, two avenuesof approach were taken: (1) reducing the amount of use and/or (2) reducing conversion losses. For example, the furnacethat heats a building produces unusable and toxic flue gas thatmust be vented to the outside and in this process some of theenergy is lost. Table 1-1 presents typical values for buildingheat losses and gains at design conditions for a mid-Americaclimate.Actual values will vary significantly with climate andbuilding construction.

The projected total U.S. energy consumption by end-usersector: transportation, industrial, commercial, and residentialis shown in Figure 1-3. The per capita energy consumption forthe U.S. and the world is shown in Figure 1-4, showing that in

6 Principles of HVAC

2007 the U.S. consumption was the same as in 1965. This hasbeen achieved through application of energy conservationprinciples as well as increased energy costs and changes in theeconomy.

The efficient use of energy in buildings can be achieved byimplementing (1) optimum energy designs, (2) well-developedenergy use policies, and (3) dedicated management backed upby a properly trained and motivated operating staff. Optimumenergy conservation is attained when the least amount ofenergy is used to achieve a desired result. If this is not fullyrealizable, the next best method is to move excess energy fromwhere it is not wanted to where it can be used or stored forfuture use, which generally results in a minimum expenditureof new energy. A system should be designed so that it cannotheat and cool the same locations simultaneously.

ASHRAE Standard 90.1, Energy Standard for BuildingsExcept Low-Rise Residential Buildings, and the 100 seriesstandards, Energy Conservation in Existing Buildings, pro-vide minimum guidelines for energy conservation design andoperation. They incorporate

Table 1.1 Typical Building Design Heat Losses or Gains

Building Type

Air Conditioning Heating

ft2/ton m2/kW Btu/hft3 W/m3

Apartment 450 12 4.5 45Bank 250 7 3.0 30Department Store 250 7 1.0 10Dormitories 450 12 4.5 45House 700 18 3.0 30Medical Center 300 8 4.5 45Night Club 250 7 3.0 30Office Interior 350 9 3.0 30Exterior 275 7 3.0 30Post Office 250 7 3.0 30Restaurant 250 7 3.0 30Schools 275 7 3.0 30Shopping Center 250 7 3.0 30

these types of energy standards:

(1) prescriptive, which specifies thematerials andmethods fordesign and construction of buildings; (2) system performance,which sets requirements for each component, system, or sub-system within a building; and (3) building energy, which con-siders the performance of the building as a whole. In this lasttype, a design goal is set for the annual energy requirements ofthe entire building on basis such as Btu/ft2 per year (GJ/m2 peryear). Any combination of materials, systems, and operatingprocedures can be applied, as long as design energy usagedoes not exceed the buildings annual energy budget goal.Standard 90.1-2010 Users Manual is extremely helpful inunderstanding and applying the requirements of ASHRAEStandard 90.1

This approach allows greater flexibility while promotingthe goals of energy efficiency. It also allows and encouragesthe use of innovative techniques and the development of newmethods for saving energy. Means for its implementation arestill being developed. They are different for new and forexisting buildings; in both cases, an accurate data base isrequired as well as an accurate, verifiable means of measur-ing consumption.

As energy prices have risen, more sophisticated schemesfor reducing energy consumption

Figure 1-4 U.S Per Capita Energy Consumption(BP 2012)

have been conceived.Included in such schemes are cogeneration, energy manage-ment systems (EMS), direct digital control (DDS), daylight-ing, closed water-loop heat pumps, variable air volume (VAV)systems, variable frequency drives, thermal storage, dessicantdehumidication, and heat recovery in commercial and institu-tional buildings and industrial plants.

As detailed in a 1992 Department of Energy Report, Com-mercial Buildings Consumption and Expenditures, 1989,more than seventy percent of the commercial-industrial-institutional (C-I-I) buildings recently built in the United Statesmade use of energy conservation measures for heating andcooling.

The type of building and its use strongly affects the energyuse as shown in Table 1-2.

Figure 1-3 Projected total U.S. Energy Consumption byEnd-User Sector

(EIA 2011)

Background 7

Heating and air-conditioning systems that are simple indesign and of the proper size for a given building generallyhave relatively lowmaintenance and operating costs. For opti-mum results, as much inherent thermal control as is econom-ically possible should be built into the basic structure. Suchcontrol might include materials with high thermal properties,insulation, and multiple or special glazing and shadingdevices. The relationship between the shape, orientation, andair-conditioning requirement of a building should also be con-sidered. Since the exterior load may vary from 30 to 60% ofthe total air-conditioning load when the fenestration (lighttransmitting) area ranges from 25 to 75% of the floor area, itmay be desirable to minimize the perimeter area. For exam-ple, a rectangular building with a 4-to-1 aspect ratio requiressubstantially more refrigeration than a square building withthe same floor area.

When a structure is characterized by several exposures andmultipurpose use, especially with wide load swings and non-coincident energy use in certain areas, multiunit or unitary sys-tems may be considered for such areas, but not necessarily forthe entire building. The benefits of transferring heat absorbedby cooling from one area to other areas, processes, or servicesthat require heat may enhance the selection of such systems.

Buildings in the US consume significant quantities ofenergy each year. According to the US Department of Energy(DOE), buildings account for 36% of all the energy used in theUS, and 66% of all the electricity used. Beyond economics,energy use in the buildings sector has significant implicationsfor our environment. Emissions related to building energy useaccount for 35% of carbon dioxide emissions, 47% of sulfurdioxide emissions, and 22% of nitrogen oxide emissions.

1.4 Conceptualizing an HVAC System

An important tool for the HVAC design engineer is theability to develop a quick overview or concept of the mag-nitude of the project at hand. Toward this goal, the industryhas developed a number of rules of thumb, somemore accu-rate than others. As handy as they might be, these approxima-tions must be treated as just thatapproximations. Dont usethem as rules of dumb.

Table 1.2 Annual Energy Use Per Unit Floor Area

Building Type Annual Energy Use kWh/ft2

Assembly 18.7Education 25.5Food Sales 51.5Health Care 64.0Lodging 38.8Mercantile 24.8Office 30.5Warehouse 16.9Vacant 6.9All Buildings 26.7

Tables 1-1 and 1-2 are examples of such rules-of-thumb,providing data for a quick estimate of heating and coolingequipment sizes and of building energy use, requiring knowl-edge only of the size and intended use of the building. Otherrules-of-thumb include using a face velocity of 500 fpm indetermining the face area for a cooling coil, the use of400 cfm/ton for estimating the required cooling airflow rate,the use of 2.5 gpm/ton for determining the water flow ratethrough the cooling coil and chiller unit, using 1.2 cfm/sq ft ofgross floor area for estimating the required conditioned air-flow rate for comfort cooling, and the estimation of 0.6 kW/ton as the power requirement for air conditioning. Table 1-3provides very approximate data related to the cost of HVACequipment and systems.

Table 1.4 provides approximate energy costs for commer-cial consumers in the United States for 2013. Keep in mindthat these energy costs are very volatile at this time.

Table 1.5 gives approximate total building costs for officesandmedical offices averaged for twenty U.S. locations in 2007.

The material presented in this book will enable the readerto validate appropriate rules as well as to improve upon theseapproximations for the final design.

1.5 Sustainability and Green Buildings

The following discussion concerning sustainable designand green buildings has been extracted from Chapters 34 and35 of the 2013 ASHRAE HandbookFundamentals.

Pollution, toxic waste creation, waste disposal, global cli-mate change, ozone depletion, deforestation, and resourcedepletion are recognized as results of uncontrolled technolog-ical and

Table 1.3 Capital Cost Estimating Factors

Cooling Systems $1,600/installed ton of cooling

Heating Systems $2.65/cfm of installed heating

Fans/Ducting/Coils/Dampers/Filters $7.60/cfm all-system

population

Table 1.4 Approximate Energy Coststo Commercial Consumers (2009)

Electricity ($/kWh) 0.088Natural Gas ($/therm) 0.85LPG ($/gal) 2.90No. 2 Fuel Oil ($/gas) 3.40

growth.

Table 1.5 Approximate Total Building Costs ($/sq. ft.)(Adapted from RSMeans Costs Comparisons 2007)

24-StoryOffice

Building

510-StoryOffice

Building

1120-StoryOffice

Building

MedicalOffice

BuildingHigh 194 181 167 219

Average 149 130 121 169Low 117 110 98 132

Without mitigation, current

8 Principles of HVAC

trends will adversely affect the ability of the earths ecosystemto regenerate and remain viable for future generations.

The built environment contributes significantly to theseeffects, accounting for one-sixth of the worlds fresh wateruse, one-quarter of its wood harvest, and two-fifths of itsmaterial and energy flows. Air quality, transportation pat-terns, and watersheds are also affected. The resourcesrequired to serve this sector are considerable and many ofthem are diminishing.

Recognition of how the building industry affects the environ-ment is changing the approach to design, construction, operation,maintenance, reuse, and demolition of buildings and focusing onenvironmental and long-term economic consequences.Althoughthis sustainable design ethicsustainabilitycovers thingsbeyond the HVAC industry alone, efficient use of energyresources is certainly a key element of any sustainable design andis very much under the control of the HVAC designer.

Research over the years has shown that new commercialconstruction can reduce annual energy consumption by about50% using integrated design procedures and energy conserva-tion techniques. In the past few years several programs pro-moting energy efficiency in building design and operationhave been developed. One of these is Energy Star Label(www.energystar.gov) and another one, which is becomingwell known, is Leadership in Energy and EnvironmentalDesign (LEED) (www.usbc.org/leed).

In 1999 the Environmental Protection Agency of the USgovernment introduced the Energy Star Label for buildings.This is a set of performance standards that compare a build-ings adjusted energy use to that of similar buildings nation-wide. The buildings that perform in the top 25%, whileconforming to standards for temperature, humidity, illumina-tion, outdoor air requirements, and air cleanliness, earn theEnergy Star Label.

LEED is a voluntary points-based national standard fordeveloping a high-performance building using an integrateddesign process. LEED evaluates greenness in five catego-ries: sustainable sites, water efficiency, energy and atmo-sphere, materials and resources, and the indoor airenvironmental quality.

In the energy and atmosphere category, building systemscommissioning and minimum energy usages are necessaryrequirements. The latter requires meeting the requirementsANSI/ASHRAE/IESNA Standard 90.1-2010, Energy Standardfor Buildings Except Low-Rise Residential Buildings, or thelocal energy code, whichever is more stringent.

BasicallyLEEDdefineswhatmakes a building greenwhilethe Energy Star Label is concerned only with energy perfor-mance. Both of these programs require adherence to ASHRAEstandards. Chapter 35 of the 2009ASHRAEHandbookFunda-mentals provides guidance in achieving sustainable designs.

The basic approach to energy-efficient design is reducingloads (power), improving transport systems, and providingefficient components and intelligent controls. Importantdesign concepts include understanding the relationship

between energy and power, maintaining simplicity, using self-imposed budgets, and applying energy-smart design practices.

Just as an engineer must work to a cost budget with mostdesigns, self-imposed power budgets can be similarly helpfulin achieving energy-efficient design. For example, the follow-ing are possible goals for mid-rise to high-rise office buildingsin a typical midwestern or northeastern temperature climate:

Installed lighting (overall) 0.8 W/ft2

Space sensible cooling 15 Btu/hft2

Space heating load 10 Btu/hft2

Electric power (overall) 3 W/ft2

Thermal power (overall) 20 Btu/hft2

Hydronic system head 70 ft of water Water chiller (water-cooled) 0.5 kW/ton Chilled-water system auxiliaries 0.15 kW/ton Unitary air-conditioning systems 1.0 kW/ton Annual electric energy 15 kWh/ft2yr Annual thermal energy 5 Btu/ft2yrFday

These goals, however, may not be realistic for all projects.As the building and systems are designed, all decisions

become interactive as the result of each subsystems power orenergy performance being continually compared to the budget.

Energy efficiency should be considered at the beginning ofbuilding design because energy-efficient features are mosteasily and effectively incorporated at that time. Active partic-ipation of all members of the design team (including owner,architect, engineer, and often the contractor) should be soughtearly. Consider building attributes such as building function,form, orientation, window/wall ratio, and HVAC system typesearly because each has major energy implications.

1.6 Problems

1.1 Estimate whether ice will form on a clear night whenambient air temperature is 45F (7.2C), if the water isplaced in a shallow pan in a sheltered location where theconvective heat transfer coefficient is 0.5 Btu/hft2F[2.8 W/(m2K)].1.2 Obtain a sketch or drawing of Gorries refrigerationmachine and describe its operation.1.3 Plot the history of the annual energy use per square footof floor space for nonresidential buildings and predict thevalues for the years 2014 and 2015.1.4 Estimate the size of cooling and heating equipment thatis needed for a new bank building in middle America that is140 ft by 220 ft by 12 ft high (42.7 m by 67 m by 3.7 mhigh). [Answer: 123 tons cooling, 11,109,000 Btu/h heating]1.5 Estimate the size of heating and cooling equipment thatwill be needed for a residence in middle America that is 28 ftby 78 ft by 8 ft high (8.5 m by 23.8 m by 2.4 m high).1.6 Estimate the initial cost of the complete HVAC system(heating, cooling, and air moving) for an office building, 40 ftby 150 ft by 10 ft high (12.2 m by 45.7 m by 3.1 m high).

Background 9

1.7 Estimate the annual operating cost for the building inProblem 1.6 if it is all-electric. [Answer: $14,640]1.8 Conceptualize, as completely as possible, using infor-mation only from Sections 1.3, 1.4, and 1.5, the building ofProject 8 Two-Story Building, Appendix B, SYSTEMSDESIGN PROBLEMS.

1.7 Bibliography

ASHRAE. 2010. 2010 ASHRAE HandbookRefrigeration.ASHRAE. 2011. 2011 ASHRAE HandbookHVAC Applica-

tions.ASHRAE. 2012. 2012 ASHRAE HandbookHVAC Systems

and Equipment.ASHRAE. 2013. 2013 ASHRAE HandbookFundamentals.ASHRAE. 1995. Proclaiming the Truth.BP. 2012. Statistical review of world energy 2012.

http://www.bp.com/sectionbodycopy.do?categoryId=7500&contentId=7068481.

EIA. 2001. Annual energy review 2000. DOE/EIA-0384(2000). Energy Information Administration, U.S.Department of Energy, Washington, D.C.

EIA. 2011. International energy statistics. U.S. Energy Infor-mation Administration, Washington, D.C. http://www.eia.gov/cfapps/ipdbproject/IED Index3.cfm.

EIA. 2012. Annual energy outlook 2012 with projects to 2035.http://www.eia.gov/oiaf/aeo/tablebrowser/#release=AEO2012&subject=0-AEO2012&table=1-AEO2012&region+0-0&cases=ref2012=d020112c.

Coad, W.J. 1997. Designing for Tomorrow, Heating/Piping/Air Conditioning, February.

Donaldson, B. and B. Nagengast. 1995. Heat and Cold: Mas-tering the Great Indoors. ASHRAE.

Downing, R. 1984. Development of ChlorofluorocarbonRefrigerants. ASHRAE Transactions 90(2).

Faust, F.H. 1992. The Merger of ASHAE and ASRE: TheAuthor Presents An Overview on Events Leading up toASHRAEs Founding. ASHRAE Insights 7(5).

Ivanovich, M.G. 1997. HVAC&R and the Internet: Where toGo, Heating/Piping/Air Conditioning, May.

Nagengast, B.A. 1988. A historical look at CFC refrigerants.ASHRAE Journal 30(11).

Nagengast, B.A. 1993. The 1920s: The first realization ofpublic air conditioning. ASHRAE Journal 35(1).

Nelson, L.W. 1989. Residential comfort: A historical look atearly residential HVAC systems. ASHRAE Journal 31(1).

Woolrich, W.R. 1969. The History of Refrigeration; 220Years of Mechanical and Chemical Cold: 1748-1968.ASHRAE Journal 33(7).

Chapter 2

THERMODYNAMICS AND PSYCHROMETRICS

This chapter reviews the principles of thermodynamics, evaluates thermodynamic properties, and applies thermody-namics andpsychrometrics to air-conditioning and refrigeration processes and systems.Greater detail on thermodynamics,particularly relating to the Second Law and irreversibility, is found in Chapter 2, 2013 ASHRAE HandbookFundamen-tals. Details on psychrometric properties can be found in Chapter 1 of the 2013ASHRAE HandbookFundamentals.

2.1 Fundamental Concepts andPrinciples

2.1.1 ThermodynamicsThermodynamics is the science devoted to the study of

energy, its transformations, and its relation to status of matter.Since every engineering operation involves an interactionbetween energy and materials, the principles of thermody-namics can be found in all engineering activities.

Thermodynamics may be considered the description of thebehavior of matter in equilibrium and its changes from oneequilibrium state to another. The important concepts of ther-modynamics are energy and entropy; the twomajor principlesof thermodynamics are called the first and second laws ofthermodynamics. The first law of thermodynamics deals withenergy. The idea of energy represents the attempt to find aninvariant in the physical universe, something that remainsconstant in the midst of change. The second law of thermody-namics explains the concept of entropy; e.g., every naturallyoccurring transformation of energy is accompanied some-where by a loss in the availability of energy for future perfor-mance of work.

The German physicist, Rudolf Clausius (18221888),devised the concept of entropy to quantitatively describe theloss of available energy in all naturally occurring transforma-tions. Although the natural tendency is for heat to flow froma hot to a colder body with which it is in contact, correspond-ing to an increase in entropy, it is possible to make heat flowfrom a colder body to a hot body, as is done every day in arefrigerator. However, this does not take place naturally orwithout effort exerted somewhere.

According to the fundamental principles of thermodynam-ics, the energy of the world stays constant and the entropy ofthe world increases without limit. If the essence of the firstprinciple in everyday life is that one cannot get something fornothing, the second principle emphasizes that every time onedoes get something, the opportunity to get that something inthe future is reduced by a measurable amount, until ulti-mately, there will be no more getting. This heat death,envisioned by Clausius, will be a time when the universereaches a level temperature; and though the total amount ofenergy will be the same as ever, there will be no means of

making it available, as entropy will have reached its maxi-mum value.

Like all sciences, the basis of thermodynamics is experi-mental observation. Findings from these experimental obser-vations have been formalized into basic laws. In the sectionsthat follow, these laws and their related thermodynamic prop-erties will be presented and applied to various examples.These examples should give the student an understanding ofthe basic concepts and an ability to apply these fundamentalsto thermodynamic problems. It is not necessary to memorizenumerous equations, for problems are best solved by applyingthe definitions and laws of thermodynamics.

Thermodynamic reasoning is always from the general lawto the specific case; that is, the reasoning is deductive ratherthan inductive. To illustrate the elements of thermodynamicreasoning, the analytical processes may be divided into twosteps:

1. The idealization or substitution of an analytical model fora real system. This step is taken in all engineering sciences.Therefore, skill in making idealizations is an essential partof the engineering art.

2. The second step, unique to thermodynamics, is thedeductive reasoning from the first and second laws ofthermodynamics.

These steps involve (a) an energy balance, (b) a suitableproperties relation, and (c) accounting for entropy changes.

2.1.2 System and SurroundingsMost applications of thermodynamics require the defini-

tion of a system and its surroundings. A system can be anobject, any quantity of matter, or any region of space selectedfor study and set apart (mentally) from everything else, whichthen becomes the surroundings. The systems of interest inthermodynamics are finite, and the point of view taken is mac-roscopic rather than microscopic. No account is taken of thedetailed structure of matter, and only the coarse characteris-tics of the system, such as its temperature and pressure, areregarded as thermodynamic coordinates.

Everything external to the system is the surroundings, andthe system is separated from the surroundings by the systemboundaries. These boundaries may be either movable or fixed;either real or imaginary.