Simplified procedure for estimating air conditioning cooling loads in Ghana

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Undersized or oversized air conditioning equipment leads to high operational cost, frequent breakdown and accelerated wear of equipment. Wrong sizing of equipment is often the result of inaccurate procedures employed to estimate the cooling load of the air conditioned space. Air conditioning cooling load of buildings have been extensively researched. Today, computer programs are available on the market for more accurate estimation of cooling load. All the same, what appears to be the established practice among equipment suppliers and service providers in the air conditioning industry in Ghana is to size air conditioners for all applications by multiplying the net floor area by the same cooling load factor to arrive at space cooling load. Estimating the load by use of computer program or other accurate procedure is hardly the practice. Availability of cooling load factors that take into account the building glazing, orientation, ventilation requirements, usage pattern, among other factors, will be a more accurate and user-friendly tool that air conditioning service providers could employ to estimate cooling load of buildings to reasonable accuracy and thereby size or select the required equipment correctly. The transfer function method (TFM), which is a well-known cooling or heating load estimation procedure that has been adopted by ASHRAE, was programmed in this thesis to predict the hourly and daily average cooling load due to different types of walls, roofs and fenestration that are typically found in building construction in Ghana today. This has been used to develop cooling load factors that simplify load estimation using a worksheet. Sample calculations of cooling load estimated using the worksheet were compared with the result of cooling load estimated using a computer program and the agreement was found to be satisfactory.
A thesis submitted to the Graduate School of Kwame Nkrumah University of Science and Technology in partial fulfilment of the requirements for the degree of Master of Science in Mechanical Engineering