Thermal performance of a directional heat radiation device utilizing the Monte Carlo ray tracing method

•We introduced a directional heat radiation device with a rotatable reflecting cover.•Directional heat radiation can improve the local thermal environment of the space.•A computational model was developed by the Monte Carlo ray tracing method.•Tube spacing has the greatest influence on the thermal radiation of the device.•The directional heat radiation device can increase energy efficiency. Conventional air conditioning systems heat and cool an entire space for the total volume but are deficient in terms of energy efficiency. Partial and personalized devices rarely take into account moving occupants and are deficient in terms of flexibility. To address these problems, a directional heat radiation (DHR) device was introduced. The effectiveness of the DHR device under heating conditions was verified by experiments and the thermal performance of the DHR device under three different arrangements was analyzed. Based on energy balance, the radiation distribution factor calculation model and the heat transfer model of the DHR device were established by combining the Monte Carlo ray tracing method and the thermal network method. The results showed that the thermal performance of the DHR device arranged level downward was best and twice that of the level upward arrangement. The mathematical model of the heat transfer process was verified by experimental data, and the relative error was within 2 %. The simulation results showed that the radiation temperature at different positions θdprt in the center of the room increased with increasing tube diameter and reflecting cover opening width and decreased with increasing tube spacing. Under simulated heating conditions, the optimal structure of the DHR device has a tube diameter of 16 mm, reflecting cover opening width of 60 mm, and tube spacing of 80 mm. The heat flux per unit floor area of the DHR device was approximately 56 W/m2, which reduced the heating capacity by 20 % compared to that without the reflector cover, while improving the local thermal environment of the space and increasing energy efficiency.