Project 01
Cooling Load Estimation
Course No.: ME 4112
Course Title: Refrigeration and Mechanical Equipment in Buildings Sessional
Submitted by: (Group No. 02 of C Section, ME’17, Roll Nos. 1702136 to 1702150, Total 15)
S.N Name Roll No. S.N Name Roll No.
1 Tanmoy Chandra 1702136 9 G. M. Saad 1702144
2 Md. Shariar Al-Hasib 1702137 10 Supratik Bhowmik Showdho 1702145
3 Md. Arifuzzaman 1702138 11 Md. Hasibul Hasan 1702146
4 Ahnaf Hossain 1702139 12 Md. Aslam Hossain 1702147
5 Md. Sadnab Taqi Meah 1702140 13 Md. Hossain 1702148
6 Md. Taufiqul Islam Tamim 1702141 14 Md. Samiul Hasan 1702149
7 Shadad Chowdhury Rafi 1702142 15 Md. Atiqur Rahman 1702150
8 Noshin Tarannum Ahona 1702143
Submitted to:
Durjoy Kumar Paul
Lecturer
Department of Mechanical Engineering,
Rajshahi University of Engineering and Technology, Rajshahi-6204, Bangladesh
Date of Submission: December 27, 2022
⮚ Calculate the sensible, latent and total heat gains on the room, room
sensible heat factor from the following information. What is the required
cooling capacity?
Time: 3:00 PM
Date: 30 November, 2022
Location: Heat engine, Room no. 204
Room dimensions and orientation:
Room dimensions: Length:15.5 m
Weight=5.9m,Height=3.2m
Door:
Height=2.02m, Weight=1.05m
Window: Height=1.36m, Weight=1.51m
West side :room no 203,
East side seminar room,
South side corridor,
North side sunlight
Inside design conditions: Tdb = 250C and RH = 50%
Outside conditions: Tdb = 280C and Twb = 240C
U value for glass: 2.5 W/m2K
U value for door: 2.3 W/m2K
Shading co-efficient (SC) for glass: 0.86
Lighting load: 30 W/m2 of floor area
Infiltration: 1 air change per hour
Solution:
Heat transfer through external loads:
a) Heat transfer rate through walls:
Cooling Load Temperature Difference (CLTD) for sunlit wall:
CLTDadjusted = CLTDtable + (250C - Tin) + (Tout, avg - 290C)
CLTDwall,north = 5 + (250C – 250C) + (26.6670C – 290C) = 2.6670C
CLTDwall ,south = 8 + (250C – 250C) + (28.330C – 290C) = 7.33°C
Effective Temperature Difference (ETD) for wall:
ETD = Toutside – Tinside
ETDwall,west = 27.770C – 250C
=2.770C
ETDwall,east = 26.110C – 250C
=1.110C
Area of walls:
Awest = L*H = 15.5m*3.2m = 49.6m2
Aeast = L*H = 15.5m*3.2m = 49.6m2
Anorth = (W*H) – area of windows = (5.9m*3.2m) – 2(1.36m*1.51m) = 14.773m2
Asouth = (W*H) – area of door = (5.9m*3.2m) – (2.02m*1.05m) = 16.759m2
U value for wall:
Construction code – A0, A1, C5, B2, E1, E0
Uwall = 1/ (0.059+0.037+0.117+0.587+0.026+0.121) = 1.056 W/ m2
Heat transfer rate:
Qwall,north = Uwall Anorth CLTDwall,north = 1.056*14.77*2.667 = 41.597 W
Qwall,south = Uwall Asouth CLTDwall,south = 1.056*16.759*7.33=129.722W
Qwall,east = Uwall Aeast ETDwall,east= 1.056*49.6*1.1 = 58.14 W
Qwall,north = Uwall *Anorth* CLTDwall,north = 1.056*49.6*2.77 = 145.085W
Qwall,total = 374.544W
b) Heat transfer rate through roof:
U value for roof:
Construction code – A0, E2, E3, B5, C13, E0
Uroof = 1/ (0.059+0.099+0.050+0.029+0.122+0.587) = 1.058 W/m2K
Area of roof:
Aroof = L*W = 15.5m*5.9m = 91.45m2
Cooling Load Temperature Difference (CLTD) for roof:
CLTDroof = 220C (with suspended ceiling)
Heat transfer rate:
Qroof = Uroof Aroof CLTDroof = 0.996*91.45*16 = 2128.59W
c) Heat transfer rate through floor:
U value for floor:
Construction code – E0, E2, E3, B5, C13, E0
Ufloor = 1/ (0.121+0.037+0.117+0.587+0.026+0.121) = 0.99 W/m2K
Area of floor:
Afloor = L*W = 15.5m*5.9m = 91.45m2
Effective Temperature Difference (ETD) for floor:
Dry bulb temperature of heat engine = 280C
ETDfloor = 280C – 250C = 30C
Heat transfer rate:
Qfloor = Ufloor Afloor ETDfloor = 0.99*91.54*3 = 271.60 W
d) Heat transfer rate through glass:
For sunlit glass at north,
Solar heat gain factor (SHGF) = 85
Shading co-efficient (SC) = 0.87
Area of the glass = 2(1.36m*1.51m) = 4.11m2
Heat transfer rate:
Qglass = Aglass [Uglass (To - Ti) + SHGFmax*SC]
= 4.11[2.5(28-25) + 85*0.87]
= 334.759 W
e) Infiltration:
Volume of the room = 15.5m*5.9m*3.2m = 292.64 m3
Volumetric flow rate = 292.64/3600 = 0.08129 kg/s
From Heat and Mass Transfer Data Book (C. P. KOTHANDARAMAN) page 33,
Density of air= 1.174 𝑘𝑔/m3
ṁinf = 1.174×1×292.64 = 0.0956 kg/s
3600
Sensible heat
transfer rate:
Qs.inf = ṁinf Cp (To-Ti) = 0.0956*1055*(28-25) = 287.79 W
Latent heat transfer rate:
For barometric pressure = 1.015 bar
hfg = 2255.25 kj/kg
From psychrometric chart
For inside condition, 250C DBT and 50% RH, wi = 0.01 kg H2O/ Kg of air
For outside condition, 240C WBT and 280C DBT, wo = 0.0172 kg H2O/ kg of air
Ql,inf = ṁinf hfg (wo-wi) = 0.0956*2255.25*(0.0172-0.01) = 1552.33 W
Heat transfer through internal loads:
a) Load due to occupants:
Condition: Seated, quiet
Sensible heat transfer rate
Qs,occ = no. of occupants*SHG = 99*100*0.60 = 5940 W
Latent heat transfer rate
Ql,occ = no. of occupants*LHG = 99*100*0.40 = 3960 W
Condition: Teaching
Sensible heat transfer rate
Qs,occ = no. of occupants*SHG = 1*175*0.50 = 87.5 W
Latent heat transfer rate
Ql,occ = no. of occupants*LHG = 1*175*0.50 = 87.5 W
b) Load due to lighting:
Heat transfer rate due to lighting
Qlighting = (40*11)+(23*4)+(5*23) =647W
c) Load due to appliances:
Qs,appliances = Qfan + QPC + Qprojector = (11*75)+70+50 = 945 W
Total sensible and latent heat gains:
Qs,total = Qwall + Qroof + Qfloor + Qglass + Qs,inf + Qs,occ + Qlighting + Qs,appliances
= 374.544+2128.59+271.60+334.759+287.79+5940+87.5+647+945W
= 11016.783 W
Ql,total = Ql,inf + Ql,occ = 538.07+3960+87.5 = 4586.57 W
The total load of the room, Qtotal = Qs,total + Ql,total = 11016.783W+4586.57W = 15603.353 W
Room Sensible Heat Factor (RSHF) is given by:
RSHF = Qs,total / Qtotal = 11016.783W/15603.353W = 0.7061
Required cooling capacity = Qtotal*Safety factor = 15603.353**1.5= 23405.0295W
= 6.66 TR
≈ 7TR
