study on dew condensation risk for commercial building … · study on dew condensation risk for...

Study on dew condensation risk

for commercial building with the

Liquid cooling air conditioning

system

Speaker Dr. Shizuo Iwamoto, Kanagawa University, Japan

Wanghee Cho, IIS., the University of Tokyo, Japan

Hitoshi Kono, ASAHI KOGYOSHA CO.,LTD.,Japan

Shinsuke Kato, IIS., the University of Tokyo, Japan

Kanagawa UniversityKUCLIMA2016, WS14

24 May 2016

Aalborg, Denmark

・reduction of dew condensation (D.C.

hereafter) in rooms and air handling

units

・indoor air quality and thermal comfort

Introduction

Background

Kanagawa UniversityKU

Patation

Radiant cooling

panel

Lighting

Chilledbeams

Dry air from the

desiccant AHU

liquid cooling pipes

Liquid cooling pipes

liquid cooling unit

The summary of the Liquid Cooling

Air-conditioning System

Desiccant air-conditioning system

D.C. in FCUs, AHUs,

liquid cooling panels and /or pipes ?

D.C.risks with the Liquid

cooling system and

conventional air-conditioning

system should be evaluated.

ConclusionCalculation condition Calculation results

事務室階段室廊下

事務室

事務室

1F

2F

5F

6F

RF

地下ピット

Introduction

Background

Health and

Comfort…


D.C. causes the growth of molds, so we

must consider a method for reduction of

D.C.

Water vapor tends to spread throughout

the whole building, thus reduction of

D.C. must be considered in the whole

building and air-conditioning units.


office

office

Underground pit

Introduction

The purpose of this study

• D.C. risks by TRNSYS and TRNFLOW simulation

• Comparison between conventional and the Liquid cooling air-

conditioning system

• Modeling of desiccant air-conditioning unit for dedicated outdoor air

system



Calculation condition


The building for simulation and the setting condition

事務室廊下トイレ


2,400




G.L

4,000

4,000

4,000

4,000

4,000

4,000

1F▽

2F▽

3F▽

4F▽

5F▽

6F▽

1,500

800

2,600

1,500

800

2,600

1,500

800

2,600

1,500

800

2,600

1,500

800

2,600

1,500

800

2,600

2,400

2,400

2,400

2,400

2,400


G.L

District ：Tokyo, Japan

Purpose of use : office

Total floor area：3,525 m2

Occupant rate:0.1 person/m2

Number of stories：6

Internal heat generation :

Human ：121 W/person

Lighting ：14 W/m2

Office application：15 W/m2

Ventilation rate :

Office：30 m3/h/person

WC ：5 ACH

The summary of the building and setting condition

The section of the building The floor plan of the standard floor

Time 0~9 9~12 12~13 13~17 17~19 19~21 21~24

[%] 0 100 50 100 70 50 0

The internal heat generation rate of occupants, lighting and OAs

Introduction ConclusionCalculation results

office

office

office

office

office

office

office WC

WC

WC

WC

WC

WC

N

UPDN

UPDNEV

EV

事務室

トイレ×2、倉庫・湯沸室

(1室とする)

廊下+

エレベータ

ホールDS

+

機械室

3,600 3,600 3,600 3,600 3,600 4,800 2,400 3,600

28,800

3,6

00

3,6

00

3,6

00

3,6

00

2,0

00

4,0

00

20,4

00

corridor

EV hallWC and storageDS

M.R.

office

Calculation condition


Setting condition for air flow network in the building

N

UPDN

UPDNEV

EV

事務室

トイレ×2、倉庫・湯沸室

(1室とする)

廊下+

エレベータ

ホールDS

+

機械室

3,600 3,600 3,600 3,600 3,600 4,800 2,400 3,600

28,800

3,6

00

3,6

00

3,6

00

3,6

00

2,0

00

4,0

00

20,4

00

The floor plan and air flow network setting

Crack

Large Opening

supply

return

Under cut

10 mm

Grille in a door

600 mm×300 mm

Room and

openings

Crack length

[m]

Crack coefficient

[kg/(s・m@1Pa)]

Window in the

office1.0×2＋1.5×2 0.000033

Window in the

corridor2.4×2+0.8×2 0.000067

Doors against

outside air2.4×2+2.0×2 0.0001

Doors in stairs 1.8×2+2.0×2 0.0013

Doors of EVs 0.9×2+2.4×2 0.0013

Air leakage for windows and doors

Inlets and outlets in the ceiling of offices

Outlets in WC and storage

Consideration on over all ar flow

calculation in the building with one

hour time-step

Introduction ConclusionCalculation results

office

exhaust

corridor

EV hallWC and storageDS

M.R.

The method on evaluation of dew condensation risk in buildings

①D.C. rate=𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑠𝑢𝑟𝑓𝑎𝑐𝑒𝑠 𝑤ℎ𝑒𝑟𝑒 𝐷. 𝐶. 𝑜𝑐𝑐𝑢𝑟𝑠 𝑎𝑡 𝑒𝑎𝑐ℎ 𝑜′𝑐𝑙𝑜𝑐𝑘

𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑠𝑢𝑟𝑓𝑎𝑐𝑒𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑏𝑢𝑖𝑙𝑑𝑖𝑛𝑔×100 [%]

②D.C. frequency=𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 ℎ𝑜𝑢𝑟𝑠 𝑤ℎ𝑒𝑛 𝐷. 𝐶. 𝑜𝑐𝑐𝑢𝑒𝑟𝑠 𝑎𝑡 𝑒𝑎𝑐ℎ 𝑠𝑢𝑟𝑔𝑎𝑐𝑒

8,760×100 [%]

③Annual D.C. risk=∑D.C.rate 𝑖𝑛 𝑡ℎ𝑒 𝑏𝑢𝑖𝑙𝑑𝑖𝑛𝑔

𝑡ℎ𝑒 𝑛𝑢𝑚𝑏𝑒𝑟 𝑜𝑓 𝑡𝑜𝑡𝑎𝑙 𝑠𝑢𝑟𝑎𝑓𝑎𝑐𝑒𝑠 𝑖𝑛 𝑡ℎ𝑒 𝑏𝑢𝑖𝑙𝑑𝑖𝑛𝑔×100 [%]

Index of D.C. risk


Calculation conditionIntroduction ConclusionCalculation results

The setting condition for conventional air-conditioning system

Period Air temperature [deg. C] Relative humidity [%] Humidity ratio [kg/kg’]

Cooling period

(May~Octber)26 50 0.0105

Intermediate period

(April and November)24 50 0.0093

Heating period

(December ~ March)22 40 0.0066

Indoor set point within air-conditioning in the conventional condition


Annual air-conditioning heat load is calculated at set point shown in above table.

The inlet condition such as inlet air temperature, humidity and air volume is

controlled form calculation result of heat load every hour.

In the conventional condition, VAV duct system is adapted in the building.

Calculation conditionIntroduction ConclusionCalculation results

まとめ

The setting condition for the Liquid cooling system

The condition for the Liquid cooling system

Cooling period (May~October) Heating period(November~April)

Desiccant

AHU

①when outside air temp. > 25.5 deg.C

inlet air temp. 25.5 deg.C

inlet air humidity 11.3 g/kg’

②when outside air temp. <25.5 deg.C

if relative humidity of outside air

within 40 – 70 %

→ inlet air is outside air without heat

exchanger

if not above

→ inlet air is outside air with heat

exchanger

①when xOA≦{xMAX・(1‐η)

‐⊿x}/(1‐η)

inlet air is outside air with heat

exchanger

②when xOA>{xMAX・(1‐η)‐⊿x}/(1‐η)

all outside air

③when xOA>xMAX‐⊿x

inlet volume is maximum

V’=⊿x・V/(xMAX‐xOA)

The

Liquid

cooling

system

When PMV>0.5, the Liquid cooling system works and supplies cooling water at 21

deg. C to radiant cooling panels, chilled beams and liquid cooling units.


●In PMV calculation, metabolic rate, air velocity and clothing are set to 1.2 Met，0.1 m/s and 0.58

(summer)/0.7(winter) clo respectively.

● xMAX is the humidity ratio where PMV is equal to 0.5 in relative humidity is 70%.

Calculation conditionIntroduction Calculation results

For -0.5 < PMV < +0.5

Liquid cooling system : calculation results of indoor air


温度 [℃] 温度 [℃]

30

40

50

60

70

80

20 22 24 26 28 30

1F

2～6F

30

40

50

60

70

80

20 22 24 26 28 30

1F

2～6F

In heating and cooling period , relative humidity varies from 40 to70 %.

At 1st floor (black plot), the Liquid cooling system sometime doesn’t work because of PMV < 0.5.

At 2-6 floor, in heating period, Liquid cooling system sometimes works against PMV>0.5.

Indoor air temperatures and

humidity in heating period

Introduction Conclusion

Indoor air temperatures and

humidity in cooling period

Indoor air temperatures [degree C] Indoor air temperatures [degree C]

Ind

oo

r a

ir r

ela

tive

hu

mid

ity [%

]

Ind

oo

r a

ir r

ela

tive

hu

mid

ity [%

]

Calculation resultsCalculation condition

Calculation results

Calculation results on D.C. risk in the building


Annual D.C. risk 0.012%

The maximum D.C. rate at 30th March 20:00

・There is no D.C. in office rooms and radiant cooling panels.

・There is D.C. sometimes in core section such as corridor and stairs.

・Dew condensation occurs most frequently at the windows at 6th floor in stairs and D.C. frequency is 1.23%.

・In the Liquid cooling system, relative humidity is not controlled well in winter.

D.C. rate at the Liquid cooling system

Introduction ConclusionCalculation condition

0

1

2

3

4

5

6

結露比率[%]

1 2 3 4 5 6 7 8 9 10 11 12

時間 [月]

The maximum D.C.rate is 5.3%

D.C

.rat

e[%

]

Month

There is no D.C. in the building at conventional condition.

34

5

20

8

5 6

0

5

10

15

20

25

30

35

40

除湿による結露加湿による結露合計

一般空調機内デシカント空調機内

空調機内結露頻度

[%]

Calculation results of D.C. risk in the AHU


1/4

1/3

D.C. Frequency in the AHU

Overall annual D.C. risk (building and AHU) Conventional : 0.043%

Liquid cooling : 0.027%

Calculation resultsIntroduction ConclusionCalculation condition

Conventional

D.C. by dehumidification

Desiccant

D.C. by humidification total

D.C

. F

req

uen

cy i

n A

HU

[%

]

Conclusion

Conclusion


1. In this presentation, the D.C. risk is estimated in commercial

building with the Liquid cooling air-conditioning system or

conventional air- conditioning system by TRNSYS and TRNFLOW

simulation.

2. There is no D.C. in office rooms. There is no D.C. on radiant

cooling panels in the Liquid cooling system.

3. As result, it is confirmed that the D.C. risk in the building and

air-conditioning system is less than 1 %.

4. In addition, it is confirmed that desiccant air-conditioning

system is effective for D.C. risk reduction by compared with the

result of conventional air-conditioning system.

Introduction Calculation condition Calculation results

Thank you for your attention


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