JAUE2024-025: Comparison of Pressure Loss Calculations in Cold-Water Systems Using the Equivalent Length Method and Local Coefficient Method

Abstract

The equivalent length method for pressure loss calculation in water systems is suggested by the Standard of Building Equipment Design, while the local coefficient method is adopted by BIM software Revit. In this study, we focus on comparing the pressure losses calculated by these two methods. Firstly, a cold-water system for air conditioning units is illustrated. Then, we calculate the pressure losses for pipes, fittings, and other equipment using the two methods mentioned above. Additionally, the local pressure coefficients provided by the Society of Heating, Air-Conditioning and Sanitary Engineers of Japan (SHASE) and the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) are used in our calculations. The differences in pressure loss, especially in pipe fittings, are detailed, as well as the differences in the total pressure loss. Finally, the impact of the size of the cold-water system on pressure loss calculation is predicted, showing that the differences will be significant in larger systems. With the increasing popularity of BIM software, the pressure loss calculation standards in Japan should be revised in the future.