Performance Research And Application Of Modular Metal Radiant Cooling Panels

The modular metal radiant cooling panels has the advantages of good thermal comfort and sanitary conditions,low operating energy consumption and saving construction space of the radiant roof.It also has the advantages of simple construction,flexible installation and less cold loss.At present,in actual engineering,multiple blocks are connected in series according to the layout of the room to form a plurality of cold radiation modules,thereby forming a complete parallel water loop.However,with the number of series connected,the cooling capacity of the radiant cooling panels,the temperature difference between the water inlet and outlet of module,and the uniformity of the surface temperature distribution will change accordingly,and the pipe network resistance of the whole water system will also vary greatly.In this paper,the requirements and test principles of German EN 14240,American ASHRAE 138 and JG/T 403-2013 are compared,and the standard EN 14240 is selected as a reference to build a cold radiation roof test laboratory.The laboratory uses three blocks to form the basic module,according to the experimental conditions,and the connection mode can be freely converted into a single block connection and two series connection.At the same time,the model of metal cold radiant panel is established by CFD software.The error is compared with the CFD simulation results from three aspects of cooling capacity,surface temperature and cooling capacity attenuation ratio,and the CFD model is corrected until the error is within the allowable range.On the basis of experimental test analysis,in order to further improve the operation characteristics of different connection modes,the extended research is carried out through the verified CFD model,the operation characteristics be simulated under the conditions of single block connection,two blocks,three blocks,four blocks and five blocks in series.The main analysis contents include the following five aspects:(1)the influence of the connection mode on the cooling capacity.(2)the correlation between the average temperature of the inlet and outlet of radiant cooling panels and the surface temperature.(3)the impaction of the connection mode to the uniformity of the surface temperature distribution.(4)Temperature rise of the serial module surface and temperature difference of the chilled water inlet and outlet during multiple series connection.(5)Analysis of pipe network resistance and water supply flow in different connection modes.The results show that,with different water supply temperature,as the water supply flowrate increases,the cooling capacity per unit area of the radiant cooling panels gradually increases,and then tends to be stable.When the water supply flow rate reaches 0.35 m/s,the maximum value is reached.At this time,the two units are connected in series,three in series,four in series,and five in series,the unit area cooling capacity is compared with the single block.Show that,the average percentage reduction under the three conditions is5.84%,11.46%,16.90%,22.13%.Under the recommended flow rate(0.35m/s),as the number of series increases,the cooling capacity per unit area of the radiant cooling panels decreases gradually.The average temperature of the inlet and outlet of the cold radiant panel is inextricably correlated with the surface temperature,and the water supply temperature is in the range of 16~20?,the average surface temperature of the metal cold radiant panel is 1.504? higher than the average temperature of the chilled water inlet and outlet.The average surface temperature of the panels will increase gradually with the increase of water temperature in the tube,and the average surface temperature of the fifth block under the condition of 1(16±0.3?),2(18±0.3?),3(20±0.3?),rise relative to the first block is 7.33%,5.29%,and 3.73% respectively.Under the same working condition,the temperature rise value of the adjacent radiant cooling panels increases with the number of series,and the relative temperature rise value decreases gradually,and the temperature difference of the copper tube unit tube in the radiant cooling panels decreases with the increase of the series number.Because the higher the water supply temperature,the smaller the heat transfer temperature difference,the smaller temperature difference between the inlet and outlet of the series module,and the smaller temperature difference of the unit tube.The higher the water supply temperature in the copper pipe,the more uniform the surface temperature distribution,and the more the series connection of the radiant cooling panels,the more uniform the surface temperature distribution.When multiple series connections are used,the local resistance of the water system and the resistance along the path can be greatly reduced.Therefore,considering the cooling capacity,pipe network resistance,system complexity and cost,the energy saving effect can be achieved to a certain extent in terms of water system material consumption,operating energy consumption,and high-temperature chiller equipment input and operation energy consumption.