heatload calculation 2
Post on 14-Jul-2015
338 Views
Preview:
TRANSCRIPT
HEAT LOAD CALCULATION 2
HEAT LOAD 2 1home back next
TOPICS COVEREDLOAD CALCULATIONS FORMS FORMULAS TABLES FACTORS AIR SIDE PSYCHROMETRY2home back next
HEAT LOAD 2
HEAT LOAD 2
3
HEAT LOAD FORMSEE TRANSPARENCY
HEAT LOAD 2 4home back next
HEAT LOAD ESTIMATE PROBLEM
HEAT LOAD 2
General office Ceiling 10 Wall 4 brick, plastered both side Window- ordinary single glass internal shade Door- plywood sandwich air space Occupants - 35 person Lighting - Fluorescent 5home back next
DESIGN CONDITIONS
Outdoor design conditions 92F db / 80F wb or 95db/83wb Overestimating effect Night time temp. & rh different 76F db/ 75F wb / 95% rh
HEAT LOAD 2 6home back next
DESIGN CONDITIONS
Indoor design conditions Base on requirement and standards
75F db / 55% rh 72F db / 55% rh 71F db / 50% rh Peak time at 4.00 pm
HEAT LOAD 2 7home back next
CURRENT AIR-CONDITIONING DESIGN DATA COMPARISONJKR INDOOR TEMP.(o C) LIGHTING LOAD (w/ft2) OFFICE EQUIP. (w/ft2) OUTLET VELOCITY (ft/min.) FRESH AIR (cfm/person) 24 4-6 (2) 25-50* 20 ASHRAE 95 23-26 1.85-4.65 0.8-2 40-150 20 CIBSE 22+/-2 1.4 1.4 20
*-Carrier HandbookHEAT LOAD 2 8
QUESTIONFill in the table other information for the following conditions Outdoor air 92db/80wb Indoor 75db/55%rh
HEAT LOAD 2 9home back next
SOLAR GAIN THROUGH GLASS
Cooling Load = Window Area x Peak solar heat gain (Table 4) x Storage Factor (Table 5) x Shade Factor (Table 6) Refer to Table 4, Table 5 and Table 610home back next
HEAT LOAD 2
SOLAR AND TRANSMISSION GAIN
Heat Gain Through Walls & Roofs = Area x Equivalent Temp. Difference (Table 7 for wall & Table 8 for roof) x Transmission Coefficient (U) (Table 9)
HEAT LOAD 2 11home back next
TRANSMISSION GAIN (EXCEPT WALLS AND ROOFS)
Heat gain through all glass = Area x Temp. Difference (OA - RA) x Transmission coefficient (U) (Table 9) Heat gain through shade wall, partition = Area x Temp. Difference (OA - RA - 5F) x Transmission coefficient (U) (Table 9)
HEAT LOAD 2 12home back next
TRANSMISSION GAIN (EXCEPT WALLS AND ROOFS) (2)
Heat gain through wall, partition (adjacent to Kitchen,Boiler Room) = Area x Temp. Difference (OA - RA + 15F to 25F) x Transmission coefficient (U) (Table 9)
HEAT LOAD 2 13home back next
INFILTRATIONWhen ventilation exceeds infiltration (+ve pressure), then infiltration = 0 When rooms are design at -ve pressure, have to consider
HEAT LOAD 2 14home back next
INTERNAL LOADSPeople No. of people from no. of chairs or base on per floor area Table 10 - Heat gain from people
No. of people x Table 10 Activity, Sensible & Latent
HEAT LOAD 2 15home back next
INTERNAL LOADSPower Table 53 - Heat gain from electric motors Electric motors contribute only sensible heat to space
HEAT LOAD 2 16home back next
INTERNAL LOADSLights - Estimate (w/ft2) Lights - Type Incandescentrated lamp watt x 3.413
Fluorescent lamprated lamp watt x 1.25 x 3.413
HEAT LOAD 2 17home back next
INTERNAL LOADSAppliances most appliances contributes both sensible and latent heat load. They contribute latent heat by virtue of their function ex. drying, cooking Hood to remove this is most effective Table 50 & 51- Heat Gain from RestaurantHEAT LOAD 2 18home back next
SAFETY FACTORSafety factor added for possible error in the survey Over estimating safety factor will cause oversized air conditioning equipment - difficult to maintain space conditions < 5%19home back next
HEAT LOAD 2
ROOM SENSIBLE HEAT (RSH)Now all the load components contributing to sensible load can be added
HEAT LOAD 2 20home back next
SUPPLY AIR DUCT LOSSESIn transferring air from system cooling coil to space, four losses must be considered; HEAT LOAD 2 21home back next
Supply duct heat gain supply duct leakage loss fan heat bypassed outdoor air
SUPPLY DUCT HEAT GAINSupply air in the duct at 50F to 60F passes through surrounding environment above 90F - potential heat gain to supply air Insulation reduces this gain Typical figure < 2% of RSH
HEAT LOAD 2 22home back next
SUPPLY DUCT LEAKGE LOSSLost capacity in the supply air duct depends on duct shape, duct pressure and workmanship. Low pressure (0 - 2s.p) :
top related