Simulation of a radiation-enhanced thermal diode tank (RTDT) assisted refrigeration and air-conditioning (RAC) system using TRNSYS

Abstract

The increasing demands for refrigeration and cooling have led to higher energy consumption and greenhouse gas emissions of Refrigeration and Air-conditioning (RAC) systems. To tackle this global challenge, a Radiation-enhanced Thermal Diode Tank (RTDT) has been proposed as an innovative and sustainable condenser-cooling approach to assist the RAC system to save energy. The RTDT is a passive cooling device that utilises a Radiation-enhanced Heat Pipe (RHP) to discharge heat in one direction, i.e., from the interior of a heat-insulated water tank to the surrounding area. In this paper, TRNSYS simulation was used to conduct a case study comparing the performance of the RTDT assisted RAC (RTDT-RAC) system with a reference Air-cooled RAC system under identical ambient conditions in Adelaide, Australia. The findings show that the RTDT-RAC system can save up to 40 % energy compared with the reference RAC system, with an increased Coefficient of Performance (COP) of 5.34. Moreover, a parametric analysis has also been conducted to study the impacts of weather conditions or regions, room temperature setpoints and RHP radiative surface areas on the RTDT-RAC system's performance. The results of the parametric analysis indicate that the regions with larger day and night ambient temperature differences demonstrate better energy-savings. Both a higher room temperature setpoint and an increased RHP radiative surface area can increase the energy-savings effectively. For a 50 m3 RTDT, to achieve energy-savings, the RHP radiative surface area is found to be at least 2.2 m2, while the optimal value is about 5 m2.