26 - Air-conditioning load estimation

Abstract

The cooling load to maintain steady temperature and humidity in a conditioned space will have four components. Heat leakage through the fabric by conduction from warmer surroundings. Heat gain by radiation through transparent surfaces – usually solar but occasionally by other means (radiant heat from a process, such as furnaces). Heat gain by forced or natural convection – air infiltration and fresh air supply – sensible and latent heat. Internal heat sources – lights, people, machines, etc. – sensible and latent heat. Examination of the items which comprise the total cooling load may throw up peak loads which can be reduced by localized treatment such as shading, modification of lighting, removal of machines, etc. A detailed analysis of this sort can result in substantial savings in plant size and future running costs. A careful site survey should be carried out if the building is already erected, to verify the given data and search for load factors, which may not be apparent from the available information. Since the estimation will be based on a desired indoor condition at all times, it may not be readily seen how the plant size can be reduced at the expense of some temporary relaxation of the standard specified. Some of the programs available can be used to indicate possible savings both in capital cost and running energy under such conditions.