The influence of types of radiation terminals on indoor temperature and velocity distribution

Radiation cooling belongs to a new air conditioning method, which transfers heat mainly by radiation than by convection. Because of this, radiation cooling system is believed to create an improved thermal comfort environment than the conventional all-air system. In addition, it has the advantages of reduced energy consumption, shifted peak point of electricity, decreased air duct size, etc. Combined radiant cooling and displacement ventilation air conditioning systems has been successfully used in many projects as a dedicated outdoor air system (DOAS) with parallel sensible cooling air conditioning system and many literatures have been published on these systems. However, many of these researches focused on system modelling, performance evaluation, thermal comfort assessment, condensation issues or the control methods of the radiant cooling system. The influence of radiant cooling terminal types to the corresponding indoor microenvironments such as air temperature and velocity distribution has not been reported. The aim of this paper is to investigates the characteristics and performance of different radiant cooling terminals and provide guidelines for practical engineering. Using a typical office room as the simulation object, three radiant cooling air conditioning systems with different radiant terminals are designed respectively, that is, the floor radiant cooling system (system 1), the metal radiant chilled ceiling system (system 2), and capillary tube chilled ceiling system (system 3). Simulation models were developed to study the influence of radiant cooling terminal types to indoor temperature and velocity distribution. The simulation results show that the indoor temperatures of these three systems are satisfied with the designed temperature requirements. The temperature differences between z=0.1m and z=1.1m of system 1 is slightly higher than 3°C, while that of the system 2 and system 3 is less than 3°C, which is satisfied with the ISO7730 comfort requirements. The supply air velocities of the three systems are far less than 0.3m/s, which meet the comfort requirements. The temperature gradient of system 3 is the smallest and its velocity distribution is the most uniform among these three radiation cooling systems.