ch01 introduction design of thermal system

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Modeling Simulation and

Optimization

Prof. Suhil Kiwan

Jordan University of Science and TechnologyIrbid, Jordan, 2013

Introduction

Based on Stoecker Text Book

MAster oN SUstainable development and Renewable energy



Engineering Design

• The immediate product of the design process is a report, aset of calculations, and/or a drawing that are abstractionsof hardware.

• The subject of the design may be a process, an element or

component of a larger assembly, or an entire system.• system design: a system is defined as a collection of

components with interrelated performance.

• Thermal systems, where fluids and energy in the form ofheat and work are conveyed and converted. Renewable

Energy thermal Systems are part of thermal systems• The technical engineering activity blends in an engineering

undertakeing



Decisions in an Engineering

Undertaking • Methodology or morphology of engineering undertakings: analyze

the steps and procedures used in reaching decisions.

• Since the starting point, the goal, and the side conditions differfrom one undertaking to the next, the procedures must vary

• The advantage of analyzing the decision process, especially in

complex undertakings, is that it leads to a more logical coordinationof the many individual efforts constituting the entire venture.

• The flow diagram in Fig. 1-1 shows typical steps followed in theconception, evaluation, and execution of the plan.

• The flow diagram shows only how this design procedure fits into

the larger pattern of the undertaking. – rectangular boxes represent considerable effort and expenditures on

large projects.

– Diamond boxes represent decisions



• NEED OR OPPORTUNITY

• The word "opportunity" haspositive connotations,whereas "need“ suggests adefensive action.

• For example, an industrialfirm may recognize a newproduct as an opportunity,but if the company does notthen expand its line ofproducts, business is likely

to decline.• Thus "the introduction of a

new product is also a need.

• typical needs oropportunities lie in therenovation or expansion offacilities to manufacture ordistribute a currentproduct.



CRITERIA OF SUCCESS (STEP 2)

• Possible Criteria of Success

– Showing a profit

– The degree to which the need is satisfied in

relation to the cost (reduce dependence on

imported fuel at comparative price)

– Atmospheric pollution



PROBABILITY OF SUCCESS (STEP 3)

• Plans and designs are always directed toward thefuture, for which only probability, not certainty, isapplicable.

• For expressing uncertainty in the decision makingprocess, the normal distribution curve (Fig. 2) is a goodstarting point to measure the probability of success.

• The equation of normal distribution is

• The area under the curve between X 1 and X 2 , forexample, represents the probability P of the event'soccurring between values x 1 and x 2.



• Example

• suppose that a new product or' facilityis proposed and that the criterion forsuccess is a 10 percent rate of returnon the investment for a 5-year life ofthe plant. (In RE systems 20-25 years)

• After a preliminary design, theprobability distribution curve is lowbut attractive enough to proceed to acomplete design, including cost

estimates• If the most probable return on

investment after this complete designwere 16 percent, for example, theconfidence in this figure would begreater than the confidence in the 18

percent figure after the preliminarydesign because costs have now beenestimated based on the design.



PROBABILITY OF SUCCESS (STEP 3)

• The probability distribution curves at twoother stages, after construction and after 1year of operation, show progressively greater

degrees of confidence in the rate of returnafter a 5-year life. After 5 years, the rate ofreturn is known exactly, and the probabilitydistribution curve degenerates into a curve

that is infinitesimally thin and infinitely high.(one should distinguish between the RR andconfidence level)



MARKET ANALYSIS (STEP 4)

• To get an indication of favorable reaction by thepotential consumer, we do market analysis

• An ideal form of the information provided by a marketanalysis would be a set of curves like those in Fig. 1-5.

• With an increase in price, the potential volume of salesdecreases until such a high price is reached that nosales can be made.

• The sales-volume to price relationship affects the size

of the plant or process because the unit price is oftenlower in a large plant.

• For this reason, the marketing and plant capabilitiesmust be evaluated in conjunction with each other.



FEASIBILITY (STEP 6)

• The feasibility study and the subsequent feasibilitydecision refer to whether the project is even possible.

• A project may be feasible, or possible, but noteconomical. Infeasibility may result from unavailability

of investment capital, land, labor, or favorable zoningregulations

• Safety codes or other regulatory laws may prohibit theenterprise ((Example; In Jordan: Energy law 2010,actions 2013 (lack of regulations)

• If an undertaking is shown to be infeasible, eitheralternatives must be found or the project must bedropped.



RESEARCH AND DEVELOPMENT (STEP 7)

• The results from research and development

(R&D) is important input to the decision process.

• Research efforts may provide the origin or

improvement of the basic idea, and developmentwork may supply' working models or a pilot plant,

depending upon the nature of the undertaking.

• The possibility of the idea's originating in theresearch group should also be exploited and is

indicated by the dashed line in Fig .1-1.



ITERATIONS and OPTIMIZATION OF

OPERATION

• The decision-making process involves manyiterations, Each pass through the loop improvesthe amount and the quality of information and

data.• Optimization of operation: The challenge to

operate the facility in the best possible manner inthe light of factors as actual costs and prices.

• A challenging activity occurs when the project isnot profitable and the objective becomes that ofminimizing the loss.



TECHNICAL DESIGN (STEP 5)

• Design may be applied to the act of selecting a single member orpart, e.g., the size of a tube in a heat exchanger; to a largercomponent, e.g., the entire shell-and-tube heat exchanger; or tothe design of the system in which the heat exchanger is only onecomponent.

•

IN RE systems: Selecting PV modules or Complete system withinvertors, cables, mounting structure, and PV modules

• Design activities can be directed toward mechanical devices whichincorporate linkages, gears, and other moving solid members,electrical or electronic systems, thermal systems, and a multitudeof others.

• This step is where the largest portion of engineering time is spent.• System design as an activity lies somewhere between the study and

analysis of individual processes or components and the largerdecisions, which are heavily economic.



WORKABLE AND OPTIMUM SYSTEMS

•The distinction between designing a workable system and anoptimum system is very important step in Designing any system.

• It is so often said that "there are many possible answers to a designproblem" that the idea is sometimes conveyed that all solutions areequally desirable.

• Actually only one solution is the optimum, where the optimum isbased on some defined criterion, e.g., cost, size, or weight.

• A workable system is infinitely preferable to a nonworkable system.

• Important: extensive effort in progressing from a workable towardan optimum system may not be justified because of limitations incalendar time, cost of engineering time, or even the reliability of

the fundamental data on which the design is based.• Sometimes, superior solutions may also be precluded by fixing

interconnecting parameters between components and selecting thecomponents based on these parameters instead of letting theparameters float until the optimum total system emerges.(selecting PV modules and look for optimum orientation angle)



A WORKABLE SYSTEM

• A workable system is one that system which performsthe assigned task within the imposed constraints, i.e.,

1. Meets the requirements of the purposes of thesystem, e.g., providing the required amount of power,

heating, cooling, or fluid flow, or surrounding a spacewith a specified environment so that people will becomfortable or a chemical process will proceed or notproceed

2. Will have satisfactory life and maintenance costs

3. Abides by all constraints, such as size, weight,temperatures, pressure, material properties, noise,pollution, etc.



STEPS IN ARRIVING AT

A WORKABLE SYSTEM

• The two major steps in achieving a workable

system are

(1) to select the concept to be used and

(2) to fix whatever parameters are necessary to

select the components of the system. These

parameters must be chosen so that the design

requirements and constraints are satisfied.



STEPS IN THE DESIGN PROCESS



WORKABLE VS. OPTIMUM SYSTEM

• Example: Suppose that the pump and piping are to beselected to convey 3 kg/s from one location to another 250m away from the original position and 8 m higher

• Workable design procedure:

•

The elevation of 8 m imposes a pressure difference of (8m)(1000 kg/m3)(9.807 m/s2) = 78.5 kPa

• Arbitrarily choose an additional 100 kPa to compensate forfriction in the 250 m of pipe.

• 2. Select a pump which delivers 3 kg/s against a pressure

difference of 178.5 kPa.• Finally, select a pipe size from a handbook such that the

pressure drop in 250 m of length is 100 kPa or less.

• A pipe size of 50 mm (2 in) satisfies the requirement.



WORKABLE VS. OPTIMUM SYSTEM

• Optimum Design Procedure: (set a criterion “minimumlife time cost”

• Three major contributors to life time cost – First cost of pump

– First cost of pipe and – Running cost of pumping (pumping cost)

• All three costs depend on the outlet pressure of thepump. So “float” pump pressure

•

Establish cost pressure relation and draw as in thefigure below

• Choose the pump pressure which gives minimum totalcost.



Steps involved in the design and optimization of a thermal

system and in the implementation of the design.

E l



ExampleLocation S in Fig. 2-3 is an adequatesource of water, and location A, B, and Care points at which water must beprovided at the following rates of

flow:

Points S , A, B, and C are all at the sameelevation. The demands for water at Aand C occur intermittently and onlyduring the working day, and they maycoincide. The demand for water at Boccurs only during nonworking hoursand is also intermittent. Ground-levelaccess exists in a 3-m bordersurrounding the building. Access is notpermitted over, through, or under thebuilding.



Example

1. Describe all the concepts of workable methods you can devise tofulfill the assignment.

2. The influence of such factors as the expected life of the systemhas resulted in the decision to use a system in which a pump

delivers water into an elevated storage tank, which supplies thepiping system. A water level switch starts and stops the pump.Design the system; this includes sketching the pipe networkchosen, listing all the pipe sizes, selecting the pump, andspecifying the elevation of the storage tank. Use pressure dropdata from Fig. 2-4 and pump performance from Fig. 2-5. (Neglect

the pressure drop in the pipe fittings and pressure conversionsdue to kinetic energy.) Fill out Table 2.2.

3. Review the design and list the decisions that preclude possibleoptimization later in the design



Pump performance curve



End of this Chapter

Additional References

• Alger, J. R. M., and C. V. Hays: Creative

Synthesis in Design, Prentice-Hall, Englewood

Cliffs, N. J., 1964.

• Asimow, M.: Introduction to Design, Prentice-

Hall, Englewood Cliffs, N. J., 1962.

• Beakley, G. c., and H. V. Leach: Engineering, An

Introduction to a Creative Profession,

Macmillan, New York, 1967.

ch01 introduction design of thermal system

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