An experimental and numerical analysis of the thermal performance of double-layer Trombe walls

In this paper, we propose a new intelligent temperature-controlled ventilated double-layer Trombe wall system for cold climate zones. This system consists of an insulation layer, an inner air channel, a massive wall, an outer air channel and a glazing plate. By changing the ventilated condition of inner and outer air layers, this system further contains three types of Trombe wall structures: inner ventilated (type 1), double ventilated (type 2) and outer ventilated (type 3). This system can automatically control the heat convection between rooms and Trombe walls, according to changes of air channel temperature that is affected by the local weather condition. Thereby, this system can avoid the problem of indoor heat loss at night and indoor overheating during the day. The main objectives of this paper are: 1) to compare the energy consumption of different types with the same thickness of inner and outer air layers; 2) to compare the thermal energy performance of the same type with different thickness of inner and outer air layers; and 3) to optimize the thickness of the inner and outer air layers of the three types of Trombe wall. Long-term experiments were conducted to investigate the heating potential of ventilated Trombe walls in Qingdao (cold climate zone), China. The thermal energy efficiency of three types of Trombe walls was compared and calculated using THERB for HAM software. The measured results demonstrated that the room temperature is always lower than the outer air channel temperature of the Trombe wall, and the heat of the Trombe wall is not fully utilized. Type 2 presents the best energy efficiency, followed by type 3 and type 1. For all types, when the outer air channel depth is greater than the inner air channel depth, the energy efficiency is improved. Affected by dry-bulb temperature and global horizontal irradiation, the monthly heating load of three types of Trombe walls in ascending order are April, November, March, February, December and January. Compared with a house without a ventilated Trombe wall, the heating efficiency of type 2, type 3 and type 1 is 32.6%, 30.5%, and 23.8%, respectively.