Development of an HVAC design model for commercial buildings in Kampala city, Uganda.

Abstract

One of the most important decisions to be made during energy efficient building design is the type of heating, ventilation and air conditioning (HVAC) system. Improper design and installation of an HVAC system has negative effects on thermal comfort and energy bills. This study developed procedures for proper HVAC design and customized these procedures to suit the local building environment in Uganda. A demonstration of the results was done, with a case study of a commercial office building within the Kampala region, i.e., Uganda Revenue Authority (URA) conference centre at the URA headquarters. This study examined the available methods of HVAC design to determine their applicability to Uganda’s case by evaluating the design factors and considerations being made and their relationship to Uganda’s environment and thermal comfort requirements. Building data including, building dimensions, indoor temperature, relative humidity, air quality, CO2 concentration, and particulate matter were measured for the case study building. The outdoor temperature data was obtained from Uganda National Meteorological Authority (UNMA). With the use of engineering equation solver (EES), an HVAC design model was developed from the standard HVAC equations, with the measured data used as inputs, to generate a model, for the total building cooling load prediction. Existing HVAC design methods currently used in Uganda were evaluated and found to be based on data for locations outside Uganda. Cooling loads and heat gain simulations were performed using EES in the developed HVAC model. Using the building energy simulation test and diagnostic method (BESTEST) method, verification and validation of the model was done by comparing the model results of a sample building envelope (test cell), to the results of other energy simulation models of that test cell. Considering Uganda’s average outdoor temperatures of a 10-year period, the minimum and maximum temperatures ranged between 15.3 – 20 °C and 25.6 - 30.7 °C, respectively. The indoor temperatures for thermal comfort were calculated to be 20.2 to 21oC, at the maximum outdoor temperatures. Comparing the calculated indoor temperatures and the measured field indoor temperatures, there was a variation in the results. This was as a result over and under design leading to installation of HVAC equipment with lower cooling load capacities (44.8 kW) in comparison to the calculated load (316.65 kW) for the multimedia conference room, and higher capacities for conference room 02. The results of the developed model agreed with the results of other simulation models for cooling load calculations and falling within a range of 6.4 to 7.9 MWh/a. Thus, the developed model correctly predicts the cooling loads for commercial buildings in Kampala.