| Solar space heating is more and more widely used in building heating in China.How to maximize the use of solar energy to heat buildings is one of the most popular topics at the moment.Due to the abundant solar radiation resources in Kunming and the space heating demand in winter,a low temperature solar hot water floor radiant heating system is designed and built in a test room.The indoor temperature under different parameters(set heating temperature,inlet water temperature,flow rate,pipe spacing,and ambient temperature)were analyzed experimentally and numerically.The analysis results can provide design reference for the application of floor radiant space heating in Kunming are.In this paper,the solar test room was tested continuously for two months under different weather,setting heating temperatures,and inlet water temperatures of the radiating coil.The influence of different inlet water temperature,flow rate and pipe spacing of cooling coil were simulated by ANSYS Fluent.The following conclusions were obtained from the test and analysis:(1)The average indoor temperature and standard effective temperature of with 24m~2 test room were compared and analyzed while the typical sunny weather at Kunming in winter and the average ambient temperature at night is about 10℃.The results show that when the indoor heating temperature is set to 16°C or the inlet water temperature is 40°C,it can basically meet the thermal comfort needs of some people in the test room.When the heating temperature is 18°C or the inlet water temperature is above 45°C,it can meet everyone’s needs of indoor thermal environment.(2)The indoor temperature distribution is uniform in the vertical direction of the room,and the maximum temperature difference in the vertical direction is only 0.865°C.(3)The indoor and outdoor temperature difference is large,the heat exchange is increased in cloudy days while the ambient temperature is about 5°C.The indoor heating temperature is set at20°C or the water temperature is above 50°C can ensure the indoor thermal comfort.Conclusions can be drawn through simulation analysis:(1)The heating effect of the radiator coil at different inlet water temperatures(40℃,45℃,50℃,55℃,60℃)was compared,and the results show that:the higher the water inlet temperature is,the higher the average temperature of the floor surface is,and the shorter the time to reach the preset temperature is.However,the higher the water inlet temperature is,the bigger the nonuniformity of the floor surface temperature distribution is.Through the simulation analysis,the most suitable water inlet temperature is between 45℃and 55℃when using the low temperature hot water floor radiant heating system in Kunming.(2)After the heat effect of the radiating coil with different water inlet speeds(0.3 m/s,0.4m/s,0.5 m/s)were compered,the results show that the floor surface average temperature can be improved appropriately when the water inlet speed was increased.The average floor surface temperature only increased by 0.068℃when the speed increased from 0.3 m/s to 0.4 m/s;the temperature increased by 0.038℃when the speed increased from 0.4 m/s to 0.5 m/s.(3)The non-uniformity of the floor surface temperature distribution is 0.2058,0.2091,0.2102,respectively,and the difference is very small.The water inlet speed in the cooling coil has little effect on the non-uniformity of the floor surface temperature distribution.(4)The heating effect of five different radiating coil pipe spacings(100 mm,120 mm,150 mm,180 mm,200 mm)was compared.The results show that:in the low-temperature hot water floor radiant heating system,the pipe spacing of the radiating coil has a greater effect on floor radiant heating.The larger the pipe spacing,the lower the average floor surface temperature,the longer time to reach the preset heating temperature,and the bigger the non-uniformity of the floor surface temperature distribution is.The spacing between the radiating heating coils of low-temperature hot water floor radiant heating should not be greater than 150 mm.(5)It was found that:the temperature change of the ambient affects the indoor temperature.In the typical sunny days in Kunming,it can guarantee indoor temperature comfort while the indoor heating temperature is set at 18℃～20℃or the inlet temperature is greater than 45℃.In low temperature weather condition,indoor heating temperature should be greater than 20℃or the inlet water temperature should be higher than 50℃to meet the indoor heating demand. |
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