| Radiant air conditioning is gaining wider and wider attention because of its advantages of energy saving and comfort,economy and environmental protection.At a time when the"carbon-neutrality goals"is being promoted,the promotion and application of radiant air conditioning is of great significance in reducing carbon emissions.However,the problem of insufficient cooling capacity due to dew condensation on the surface of the radiant cooling panel and limited by the dew point temperature is also obvious due to the direct contact between the radiant cooling panel and indoor hot and humid air.However,the radiant cooling plate is in direct contact with the hot and humid air in the room,causing the surface of the plate to condense easily,and the problem of insufficient cooling capacity due to the dew point temperature limitation is also very serious.To address this problem,a model for radiant air conditioning with an infrared-transparent membrane has been developed which installs an infrared-transparent membrane vertically below the radiant cooling plate of a radiant air conditioner to form a closed gas interlayer between them.The electromagnetic waves in the8-14μm band emitted from the cold and heat sources can penetrate the membrane for radiant heat transfer,while the indoor wet air cannot penetrate the membrane to generate condensation on the radiatnt cooling plate,which fundamentally solves the problem of easy condensation on the surface of the radiant cooling plate and the problem that the cooling capacity is limited by the dew point temperature.The thermal resistance layer not only reduces the influence of indoor temperature on the surface temperature of the radiant cooling plate and increases the radiant heat etransfer between the hot and cold sources,but also makes the surface temperature of the infrared-transparent membrane much higher than that of the radiant cooling plate,which enhances the anti-condensation ability.In this paper,we hope to improve the anti-condensation and cooling capacity by optimizing the structure of radiant air conditioning with an infrared-transparent membrane and increasing the thermal resistance of the thermal resistance layer.Based on this,we studied the thickness of the thermal resistance layer,the type of gas in the thermal resistance layer(vacuum,argon,nitrogen,air,carbon dioxide),and the relative air humidity in the thermal resistance layer on the cooling performance of radiatnt air conditioning,the results show that:the thickness of the thermal resistance layer is 20mm is the critical point of thermal conductivity and convective heat transfer in the thermal resistance layer,at this time,the thermal resistance is the largest,the best operation performance of radiant air conditioning;When the thermal resistance layer for the vacuum thermal resistance layer,the surface temperature radiant cooling plate is the lowest,the surface temperature of membrane is close to the indoor air temperature,the best cooling performance,argon second;thermal resistance layer in the relative air humidity on the heat transfer between the cold and hot sources is very small,as long as the relative air humidity does not exceed 80%,the surface of the radiant cooling plate does not have the risk of condensation.On this basis,this paper compares the cooling performance of traditional radiant air conditioning and radiant air conditioning with an infrared-transparent membrane.The results show that:under the same water-supply condition and indoor environment,the air-contact surface temperature of radiant air conditioning with an infrared-transparent membrane is7.32°C higher than that of traditional one,the surface temperature of radiant cooling plate is0.1°C lower than that of traditional one,the average airflow velocity near human body is more than 0.03 m/s lower than that of traditional one,and the average airflow velocity of indoor activity area is more than 0.05 m/s lower than that of traditional one.This paper further investigates the effects of water-supply temperature and water supply-velocity on the operating characteristics of radiant air conditioning with an infrared-transparent membrane.The results show that for every 1°C decrease in water-supply temperature,the cooling capacity increases by 8.92 W/m~2and the surface temperature of the membrane decreases by 0.47°C.When the water-supply temperature is lowered to 8°C,the radiant air conditioning not only has no condensation,but also increases the cooling capacity by 65.03%compared to the water-supply temperature of 16°C.When the water-supply velocity is lower than 0.3 m/s,increasing the water-supply velocity can significantly increase the cooling capacity,and when the water-supply velocity is higher than 0.3 m/s,the rate of cooling capacity increase becomes lower.In addition,the functions of water-supply temperature,water-supply velocity and the surface temperature of membrane are identified separately in this paper.Finally,this paper investigates the effect of indoor relative humidity on the operation performance of radiation air conditioning with an infrared-transparent membrane.The results show that the cooling capacity is not affected by the indoor relative humidity,but the indoor relative humidity affects whether the surface of membrane condensation.When the indoor relative humidity does not exceed 70%,there is no risk of condensation. |
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