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15 March 2011

Sizing Air-Conditioning Units



PAUL HAY Capital Projects

Topic:            Sizing Air-Conditioning Units
Author:          Paul Hay
e-mail:            paul.hay@phcjam.com
profile:           www.linkedin.com/in/phcjam


SAMPLE PROBLEM

Assuming negligible infiltration, calculate the size air-conditioning system required for an office building constructed as follows:

Location:            Kingston, Jamaica                           Orientation    = North
Dimensions:        18 m x 18 m x 7.2 m high                Stories            = 2
OTTVr           = 18.2 W/m2                                      Occupancy    = 10 m2/person
OTTVw          = 113.8 W/m2                                    Lighting         = 15 W/m2
Misc. Power   = 25 W/m2


SOLUTION

(A)         For internal heat-gain,

Total floor area                                 = 2 (18 x 18)            = 648 m2
No. occupants                                  = 648/10                  = 65 persons (approx)
Heat from occupants    = 100 x No. occupants                                                           [1.1]
= 100 x 65   =  6,500 W
Heat from lighting                                = 15 x 648             =  9,720 W
Heat from power                                 = 25 x 648            = 16,200 W
Internal heat-gain                                 =                              32,420 W

(B)         For external heat-gain,

Roof  area                                           = 18 x 18       
                                                           = 324 m2
Heat-gain from roof                             = 18.2 x 324         =   5,896.8 W
Total wall area              = 4 (18 x 7.2)  = 518.4 m2
Heat from walls            = 113.8 x 518.4                           =  58,993.92 W
External heat-gain         =                                                      64,890.72 W

(C)         For A/C size,

Total heat-gain              = 32,420 + 64,890.72                =  97,310.72 W
A/C size                       = Total heat-gain                                                                      [1.2]
   3,516.85 W/Tr
= 97,310.72                               = 27.67           =  30 T (approx.)
   3,516.85

1 comment:

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