Optimal insulation’s thickness of pipes in Variable Refrigerant Flow (VRF) system—An-Najah Child Institute as a case study

Abstract

Buildings use a significant amount of the world’s total primary energy, particularly in heating and cooling systems. Energy consumption of air conditioning systems can be lowered by installing energy-efficient systems that take into account piping thermal insulation. The objective of this research is to calculate the optimal thickness of insulation for piping networks with variable refrigerant flow and to investigate the environmental and economic impacts of using the optimal insulation thickness. The case study of this research is An-Najah Child Institute. The research is based on the current cost over the life cycle of the insulation, which is assumed to be 15 years, to determine the optimal thickness of the common insulation types (rock wool, extruded polystyrene, and flexible foam) for different pipe diameters and different refrigerant flow rates. The research results show that the optimum insulation thicknesses for pipe diameters from 12.7 to 50.8 mm using Rockwool are 32 to 44 mm, 28 to 38 mm for extruded polystyrene, and 11to 13 mm for flexible foam insulation. The reduction in energy losses from the optimal Rockwool insulation thickness in the case study piping system ranges from 78.5% to 81.6% compared to the uninsulated insulated piping system. In addition, the carbon emission saving by the optimal Rockwool insulation thickness is 1737, 1541, 1033, and 1160 kg CO2 for coal, oil, natural gas, and LPG fuel used in electricity generation, respectively. In addition, the study found that the physical parameters of the refrigerant, such as quality and flow rate, do not affect the optimal insulation thickness for all insulation types studied. And the thermal power saved corresponds to only 1.2% of the total system capacity