Research Of The Thermal Response Of Night Ventilation In Exterior Walls Of Phase Change Energy Storage Block

Rapid economic development has brought a lot of energy consumption and a large number of energy-saving technology come with it like the mushrooms. In which the phase change mate-rials used in the structure of the building envelope is the one. However, phase change materials in the study and application existing heat accumulation. Namely, endothermic and exothermic is unblance in day and night. This result in the storage capacity of phase change materials greatly reduced in second day.The south wall of Nanjing area is studied in this paper. The solar-air temperatures of July 20th to July 24th of the " dog days " in Nanjing, a total of 5 days, are selected as outdoor cal-culated temperature. Take outdoor solar-air temperature of these 5 days as a period and three periods as a group. Initially, the software-Matlab is used to programmed simulate the heat trans-fer process of phase change ventilation wall (Structure A-the phase change gypsum is placed at the inner hole of the three row holes of hollow block and the air is in the outer hole; Structure B-the phase change gypsum is placed at the outer hole and the air is in the inner hole) under different ventilation velocities by finite volume method based on the model of the sensible heat capacity. This do some guidance on after experimental process.Experiments were carried out using hot box method. The outdoor environment is simulat-ed by programmable controller and other indoor surfaces are heat insulation. The phase change ventilation wall is piled on the specimen holder and its top and bottom have inlet and outlet. The inlet is connected to the centrifugal electrodeless frequency conversion fan. The thermocouples are arranged at the inside and outside surface of the phase change ventilation wall and real-time monitor with heat flow meter. The experiment studies and analyzes the effects of night ventila-tion velocity variation on thermal response under different structures (Structure A and Structure B) of the south wall that is phase change ventilation energy storage brickwork. The results show:The phase change material placed at the inside of the hollow block is superior to that placed at outside, the maximum amplitude of the wall internal surface temperature fluctuations when placed at the inside is only 55.9% of that placed at the outside; The optimal flow veloci-ties of Structure A and Structure B are both 2m/s, the minimum amplitude of the wall internal surface temperature fluctuations and the maximum delay coefficient are respectively 1.74℃,8h and 3.72℃,7h; Compared with the no ventilation, when the thermal resistance is respectively increased 115.8% and 88.6%, the heat enter into the indoor is respectively reduced 38.2% and 29.3%. After the experiment, the correctness of the program can also be verified. The relative errors of the wall internal surface temperature of Structure A and Structure B under 2m/s are respectively 3.9% and 4.5% through the calculation and both less than the standard error that is 5%.Meanwhile, Structure C (the phase change material is placed at the inner hole of the three row holes of hollow block and the expanded polystyrene is in the outer hole) and Structure D (the phase change material is placed at the outer hole of the three row holes of hollow block and the expanded polystyrene is in the inner hole) are simulated and analyzed respectively by this procedure. The conclusions are:The optimal flow velocities of Structure C and Structure D are also 2m/s, the minimum amplitude of the wall internal surface temperature fluctuations and the maximum delay coefficient are respectively 1.91℃,8h and 4.07℃,7h at this time; The max-imum amplitude of the wall internal surface temperature fluctuations of Structure C is 3.94℃, only 55.9% of Structure D; Compared with the no ventilation, when the thermal resistance is respectively increased 93.2% and 79.6%, the heat enter into the indoor is respectively reduced 35.6% and 23.7%.Finally, the indoor thermal comfort and energy saving rate of the four Structures under different ventilation velocity are also analyzed. The indoor thermal comfort evaluation borrow the "Predicted Mean Vote (PMV)" and " Percentage of the Person Dissatisfied (PPD)". The study of energy conservation can come down to the power consumption. The required power consumption that is under Om/s of the ventilation flow velocity and 24℃ of air conditioning refrigeration is seen as the comparative object of the energy saving rate. The study found that the phase change gypsum placed in the internal is better than that in the external under the same ventilation flow velocity and climate conditions, namely Structure A is superior to Structure B and Structure C is superior to Structure D. The four Structures under the optimal flow velocity not only have better indoor thermal comfort, but also have small the total power consumption. 29.5%、27.1%、27.2% and 24.6% of the power consumption is saved respectively.