A space to be air conditioned at 25 C, 50% RH has the following peal load data R

Question

A space to be air conditioned at 25 C, 50% RH has the following peal load data Room size: 20 m wide, 20 m long and 4 m high North glass: 4 windows of 2m times 1.5 each with solar heat gain factor = 50 W/m^2 East glass 4 windows of 1m times 0.75 m each with SHGF = 60 W/m^2 East wall and North wall have two doors 2.5 times 3m Overall heat transfer coefficient in W/m^2: roof =2, glass = 6, Door = 1.5, and floor = 3 delta T_QQ for east wall = 10 k, west wall = 15 K, North wall = 10 k, South wall = 13 K, roof = 18 k floor is on ground level No infiltration Occupancy: 100 persons, 75 W sensible, and 65 w latent Lighting: 10 W/m^2 Ventilation: 0.3 m^3/min per person Outdoor: 43 C and 30 % RH Indoor: 25 C and 50 % RH Determine the room sensible and latent heat

Explanation / Answer

solution:

1)for given room condition heat loads are either sensible or latent and they are as follows

2)sensible heat gain through glass

from north window

Hsn=n*SHGF*A=4*50*2*1.5=600 watt

from east window

Hse=n*SHGF*A=4*60*1*.75=180 watt

3)heat gain from opaque surfaces

Hs=U*A*dT

from roof,HSr=2*400*18=14400 watt

from glass,Hsg=6*{4*2*1.5+4*1*.75}*10=900 watt

from door,Hsd=1.5*2*2.5*3*2*10=450watt

from just wall assuming wall and floor overall heat transfer coefficient is ssame

Hsw=3{(20*4)*15+(20*4)*13+[20*4-4*2*1.5-2*2.5*3]*10+[20*4-4*1*.75-2*2.5*3]*10}=10170 watt

4)heat load due to occupancy

sensible load=Hso=100*75=7500 watt

latent load=Hlo=100*65=6500 watt

5)heat load due tolightning

Hsl=10*whole surface area of room=10*[20*20*2+20*4*4]=11200 watt

6)heat load due to outside air as ventilation

Q=ventilation=.3*100=30 m3/min

OASH=.0204*Q*(To-Ti)=.0204*30*(43-25)=11016 watt

OALH=50*Q*(wo-wi)

from psychrometric chart, we get

wo=.0166 kg/kg of dry air

wi=.0098 kg/kg of dry air

OALH=50*30*(.0166-0.0098)=10200 watt

7)hence room overall sensible and latent heat load is sum as follows

sensible heat load=Hsn+Hse+Hsr+Hsg+Hsd+Hsw+Hso+Hsl+OASH=56416 watt

latent heat load=Hlo+OALH=16700 watt

so room sensible heat load is

SH=56.416 KW

LH=16.7 KW

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