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

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.

Automated summary

This study proposes an innovative and sustainable condenser-cooling approach called Radiation-enhanced Thermal Diode Tank (RTDT) to assist in energy-saving for Refrigeration and Air-conditioning (RAC) systems. The research finds that the RTDT-RAC system can save up to 40% energy compared to the reference RAC system, with a higher Coefficient of Performance (COP) of 5.34. Additionally, the parametric analysis shows that regions with larger day and night ambient temperature differences, higher room temperature setpoints, and increased RHP radiative surface areas can effectively increase energy savings.