Research On Phase Change Hot And Cold Wall Radiation Air Conditioning System In Zero Energy Building

The development of zero-energy buildings has become a trend nowadays with the widespread concern of increasing building energy consumption and building energysaving technology.High-performance enclosures,low-energy air-conditioning systems,and the rational use of renewable energy are key to achieving "zero energy" consumption in buildings.The air conditioner terminal is the main component of the air conditioning system which affects the system energy consumption directly.Radiation ends are commonly used because of comfort and energy saving.The property of energy storage of phase change materials is often applied to air conditioning systems,which is an effective way to build energy conservation and load regulation.Based on this,this paper proposes a two-layer phase-change cold-heat wall radiant air-conditioning system for zero-energy buildings.The properties of system storage,discharge and application effects were studied in this paper with the combination of numerical simulation and experimental testing.First of all,the enclosure structure was optimized by theoretical calculation.The economic benefits were analyzed under the premise of ensuring excellent insulation effect.The most economical insulation layer thickness in Wuhan was determined to be 40 mm,and the physical model had constructed accordingly.The properties of storage and discharge of the system were simulated and calculated using the Fluent calculation software at different operating conditions.The results indicate that different supply temperatures and flow rates of water have an effect on winter and summer conditions when it storage the energy,and the influence of water supply temperature was more significant than water flow rates.The better parameter of water supply temperature and flow rate in winter and summer are 45℃,0.5m/s and 16℃,0.5m/s respectively after analyzing the phase transition time and wall temperature,the phase change material has a better storage capacity as well.When the energy is released,the energy storage material can effectively slow down the wall temperature fluctuation in order to improve the indoor thermal comfort.The PHOENICS calculation software was used to simulate the indoor thermal environment in winter and summer conditions,in addition,the temperature field of the radiant air conditioning system in the phase change of hot and cold wall was analyzed.The results show that during the discharge process,the overall temperature distribution in the room is uniform,and the summer is 26℃,20℃in winter.However,the temperature near the radiation surface is slightly different than the other areas.In the end,a zero-energy-saving and energy-saving renovation of a building in Wuhan were carried out,and an experimental platform was set up to test the winter working condition of the phase-change hot and cold wall air-conditioning system.The experimental results show that the room temperature can rise rapidly after the system is turned on,and the room temperature will be maintained at 14~19℃to meet people’s thermal comfort during the whole process of storage and release heat energy.The results of the winter test and the simulation were compared that there are no significant differences between the results,which in an accepted range.It is further feasible to demonstrate that the phase change of hot and cold wall radiant air conditioning system can meet the building’s heat and cold load.