Evaluation of commercial software to compute the cooling load for buildings in Saudi Arabia

This study is conducted & submitted in partial fulfillment of the requirement for the Degree of Master of Science in Mechanical Engineering, College of Engineering, King Saud University, Riyadh, Kingdom of Saudi Arbia, 1429H - 2008GAir conditioning equipment has become increasingly widespread in the Kingdom of Saudi Arabia due to the extreme climatic conditions and due to the fast population and economic growth. In such a large air conditioning market, energy conservation through accurate sizing of AC equipment becomes a high priority. Sizing of AC equipment depends on the accurate calculation of the cooling load for the targeted building. The objective of the present work is to compare the results of the cooling and heating loads computed by the LOADSOFT program which is based on the radiant time series method (RTSM) with three other commercial programs: HAP, ELITE and TRACE which are based on the transfer function method (TFM) when applied to a construction taken from ASHRAE Standard 140. It was shown that LOADSOFT produces the optimum results when compared to eight well known cases recommended by ASHRAE and is able to calculate the cooling loads for air-conditioning of any building. Such results have been published in ASHRAE Standard 140-2004: "Standard Method of Test for the Evaluation of Building Energy Analysis Computer Programs". This standard provides a method of test that can be used for identifying and diagnosing differences in predictions for whole building energy software that may possibly be caused by software errors. The current set of tests include a zone consisting of simple rectangular sections that are used to examine the effects of the basic set of wall, roof, and window loads, the effect of windows on different exposures and the use of external shading devices. Also, it contains heating and cooling systems in all cases. Then the model is applied to a number of cities in the Kingdom of Saudi Arabia, namely, Riyadh, Jeddah and Abha. Taking LOADSOFT results as a reference, it was shown that HAP provides the closest results to the reference program, whereas the other two programs, ELITE and TRACE, have shown less accurate results. In general, total cooling loads calculated using RTSM closely agreed with or were slightly less than those of the TFM with the same inputs. Greater differences occurred in heavyweight cases, with TFM generally predicting slightly higher peak cooling loads than RTSM. Greater differences also were observed in zones with extremely high internal radiant loads and large glazing areas. This study has demonstrated that the radiant time series method provides the best and most reliable results for calculating loads when compared to other older methods. Given the results obtained during the course of this work, where inconsistencies were observed in a few instances, it is important to note that further work in this direction needs to focus on resolving those inconsistencies and ensuring that input parameters reflect actual conditions as closely as possible so that more concrete conclusions can be obtained.King Saud Universit