Book - School of Science and Technology

Application 519ApplicationHaving arrived at the maximum hourly heat gain for the space or spaces to be served,probably the most searching of the seasonal conditions to be met, it is necessary tocalculate the conditions to be maintained in the plant and the capacity of the variouscomponents (fans, cooling coils, heater batteries, water chillers, and so on).The routine calculations necessary are best illustrated by application to an examplesuch as the all-purpose hall, in use for concerts and other activities, as shown in Figure 3.13.This is repeated here for convenience of reference as Figure 18.3. The building characteristicsand the bases for the design of the system are:BuildingSeating capacity ˆ 500 personsLighting load ˆ 20 kWVolume of hall ˆ 6000 m 3External conditions Summer WinterTemperature ˆ 28 CDB 4 C saturatedˆ 18:5 CWBEnthalpy ˆ 51:95 kJ/kg 16:70 kJ/kgInternal conditions Summer WinterTemperature ˆ 21 CDB 20 CDB50% saturation ˆ 14:8 CWB60% saturation ˆ 15:3 CWBEnthalpy ˆ 41:08 kJ/kg 42:58 kJ/kgOutside air per occupant, year roundTable 1:6 ˆ 8 litre/sSummer cooling and dehumidificationThe orientation of the example building presents two faces to solar heat gain and it wasmade clear in Chapter 3 (p. 87) that the peak gain occurred at 15.30 hours BST in June.Building fabric heat gainThe scope of the calculations set out in the earlier chapter was restricted to an analysis ofthe heat gains arising from conduction through the structural elements and from solarglazing. The criteria were the outside and inside air temperatures noted above and theresults were as follows:GlazingSolar radiationˆ 18 kWConduction ˆ 2:8kWWallsSolar radiation and conduction ˆ 1:6kWRoofSolar radiation and conduction ˆ 1:5kW ˆ 23:9kW* Dry bulb temperature is used here in preference to resultant temperature. See Chapter 3, p. 93.