Study On The Influence Of Variable Operating Condition Of Water System In Cold Radiation Air Condition

The Metal radiant panel has the advantages of easy installation,low maintenance cost,uniform temperature distribution and high comfort.It is a widely used radiant panel.However,its performance is affected by many factors,such as chilled water temperature,chilled water flow velocity and indoor thermal environment.In this paper,experimental and simulation methods are used to explore the optimal regulation mode of the radiant panel chilled water valve under extreme operating conditions(the radiant panel surface temperature is equal to the indoor air dew point temperature),and the influence of the chilled water flow rate on the radiant panel performance(anti condensation characteristics,refrigeration effect,surface temperature uniformity and indoor air temperature)under normal operating conditions(the chilled water temperature is 2℃ higher than the indoor air dew point temperature)The optimal flow rate range of chilled water was obtained.The performance test platform of radiant panel is built.Based on en14240 standard,the radiant panel performance test platform is built,which is composed of chilled water system and cabin.The heat transfer mathematical model of metal radiant panel is established,and the simulation results are compared with the experimental data,the results can better reflect the heat transfer process of cold radiant panel.Under the extreme operating conditions(the surface temperature of radiant panel is equal to the dew point temperature of indoor air)and the indoor cooling load of180 W / m2,the effects of chilled water valve on the performance of metal radiant panel are compared through experimental tests.The results show that in the on-off mode of the chilled water valve,the condensation problem on the surface of the metal radiant panel will be significantly improved,but the cooling effect of the metal radiant panel will be greatly reduced,and the indoor thermal comfort will also be significantly reduced.Under the PID control mode of chilled water valve,when the chilled water flow rate is controlled between 0.3 m/s and 0.45 m/s,the condensation phenomenon on the surface of cold radiant panel can be effectively reduced,and good refrigeration effect and indoor thermal comfort can be maintained.Under the normal operation condition(the temperature of chilled water is 2℃higher than the dew point temperature of air),the influence of chilled water flow rate on the performance of radiant panel under the determined cooling load is explored,and the optimal flow rate range under different cooling load conditions is obtained.The results show that: under a certain indoor cooling load,the anti condensation performance of the radiant panel will gradually deteriorate with the increase of the chilled water flow rate,but as long as the chilled water flow rate is less than or equal to the upper limit flow rate,the surface of the radiant panel will not condense;at the same time,when the chilled water flow rate increases,the cooling effect of the radiant panel will be strengthened,and the surface temperature uniformity will be increased Through the analysis of the experimental data,it can be seen that when the freezing water flow rate is maintained in a certain range,the indoor thermal comfort will be higher.The effects of the flow rate of chilled water,the temperature of water supply and the indoor cooling load on the surface temperature of the cold radiation plate were compared by simulation method.The results show that the three factors all have an influence on the surface temperature of the cold radiation plate.The smaller the flow rate of chilled water is,the more obvious the influence on the surface temperature of the cold radiation plate will be.Similarly,the lower the temperature of frozen water,the greater the impact of freezing water temperature on the surface temperature of the cold radiation plate,the higher the temperature of frozen water,the impact on the surface temperature of the metal cold radiation plate will be small;On the contrary,when the indoor cooling load is small,the influence of the indoor cooling load on the surface temperature of the cold radiation plate will be small,but the greater the indoor cooling load is,the more significant the influence of the cooling load on the surface temperature of the cold radiation plate will be.