Study On The Coupling Effect Of Building Thermal Mass And Solar Air Heating System

Conventional heating and cooling system will not only consume large amounts of non-renewable energy sources in building, but also produces environmental pollution and a variety of human health problems. So, based on the fully utilization of renewable energy, exploring the building's thermal regulation performance of itself is very significant to indoor thermal environment. Solar energy can be collected and stored in the building integrated with the Wall-mounted solar air collector to solve the problem, but the indoor air temperature fluctuations are very large in the heating period and also the problem of overheating in summer is existed. Research shows that the indoor thermal environment can be regulated by building thermal mass. Hence, the reasonable utilization of thermal mass is very important in low (zero) energy consumption and solar air heating buildings.First, "temperature variation coefficient" was firstly defined and used by applying the concept of variation coefficient in statistics to quantitatively evaluate the indoor thermal environment stability. From the experimental data, the indoor thermal environment is more stable with the greater total building heat capacity, and the relative fluctuation degree of different building can only be determined by its total building heat capacity with same outdoor environment. By analyzing the data from the simulation software of EnergyPlus, when the total heat capacity of the experimental room decreases to half and increase to double, the level of the indoor temperature fluctuation was reduced by only 17% and increased by 12% with the constant building heat loss coefficient. The maximum and minimum total heat capacity can be determined to utilizing the thermal mass reasonably when indoor air temperature variation coefficient does not vary with the increase of total heat capacity and the indoor air temperature variation coefficient equals to that of outdoor air, respectively, at last, the fitting formulas of temperature variation coefficient as a function of the building total heat capacity and heat loss coefficient were obtained.Second, the features of heat supply of the solar air collector were experimentally studied. For the purpose of the performance of heat storage and releasing in thermal mass, the conclusions can be obtained as follows:The concrete slab for storing heat has effect of stabilizing indoor air temperature fluctuation, but this effect was weakened for the roof's huge heat loss. And the cooling effect of the concrete slab in summer is obvious by storing cold energy in night. After the proper design of orthogonal simulation experiment, the conclusion can be obtained as follow:The best capacity ratio of external thermal mass to internal thermal mass is 5:1; the heat transfer coefficient of internal thermal mass is the bigger, the better.Finally, to explore the effect and mechanism of the thermal mass'heat capacity and heat transfer coefficient, the mathematical model of solar air heating building were established. The thermal diffusion number is defined, which represent the ratio of heat transfer velocity to heat capacity per unit area. As the increase of internal and external thermal diffusion number of thermal mass or the thermal diffusion number of solar air collector, the delay of the indoor air temperature decreases; the day air temperature is a superposition of three waves with different amplitude and phase, the internal and external thermal diffusion number of thermal mass are main factors that influence the wave's amplitude of indoor air temperature by analyzing the waves'decline factor, and as the increase of internal thermal diffusion number, the amplitude decrease, the external thermal diffusion number has opposite effect. When the heat transfer coefficient is constant, the smaller the time constant of thermal mass, the smaller the total heat load is, but the greater the heat load changes throughout the day. With the increase of the internal convective heat transfer number, night heat load and its amplitude increase gradually and delay time decrease, the delay time of day heat load decrease and amplitude increase; With the increase of the external convective heat transfer number, the delay times of heat load in day and night decrease, the amplitude increase.