| Due to high comfort,health,safety,energy saving potential,using low grade energy and many other advantages of radiant cooling,domestic and foreign scholars have carried out a lot of theoretical and experimental investigations on its different system forms about system performance,design control method,the cooling of the indoor thermal environment characteristics and personnel comfort.As a new type of cooling terminals,the radiant cooling system will be widely used in the future.At present,there are a lot of researches on thermal comfort of cooling terminals at home and abroad,but there are few researches on the human thermal comfort of the capillary radiant cooling.Based on this,the author thinks that it is necessary to conduct the thermal comfort of capillary radiant cooling research in summer,to find out the different effects of terminals on human thermal comfort,and also research the indoor thermal environment and comfort,to provide a basis for the study of radiation cooling of the Yangtze River Basin region.First of all,through the human thermal comfort experiment,the capillary radiation cooling had been proven that it has better comfort performance in the paper.Based on the experimental platform of capillary radiation cooling/heating in Chongqing University,the human thermal comfort experiments were carried out in summer,to analyse the indoor thermal environment and thermal comfort of side wall and ceiling capillary radiant cooling,and also study the applicability of PMV-PPD index to evaluate the thermal comfort under the radiant cooling condition.20 college students were chosen as subjects(10 men and 10 women),took part in the two teriminals radiation experiment(capillary wall and ceiling)under 26? indoor air temperature respectively.The experiment lasted for 120 min,during which the subjects were in a sedentary state,the clothing insulation was about 0.4clo and the metabolic rate level was 1.1met.The result shows that when the room condition reached steady,the relative humidity,air velocity,vertical temperature difference,asymmetric radiation,thermal sensation and thermal comfort of two terminals can meet the requirements of thermal comfort,indicating that two terminals of radiation cooling end can provide satisfying thermal comfort environment;there is not much difference between the mean radiant temperature and air temperature for the two teriminals;fot the ceiling radiation,the vertical temperature difference is smaller,thermal sensation vote is closer to neutral,and the thermal comfort vote is higher,at the same time,the expected vote of the environment and overall acceptability also showed that subjects preferred ceiling radiation than wall radiation;Under the steady and uniform indoor thermal environment,the difference between PMV value of the wall radiation and the ceiling radiation cooling and the thermal sensation vote(TSV)of the subject is less than 0.5,so in the neutral comfort zone that the average radiation temperature and the air temperature are almost uniform and stable environment,PMV can be used to predict the thermal comfort of radiation environment.Secondly,based on the results that the thermal environment of radiation cooling is uniform and PMV index has a better prediction accuracy,the indoor thermal environment characteristic of different radiation cooling terminals is studied in this paper.Taking the water supply temperature of 18 ? as an example,the indoor thermal environment of the radiant cooling system of the capillary network was tested without human interference,the envelope temperature,radiation temperature,indoor temperature field,velocity field of the side wall and the ceiling capillary cooling are analyzed and compared.On this basis,the CFD model is established under the capillary radiation cooling environment,and the accuracy and reliability of the CFD model are verified according to the experimental data.The result shows that the space temperature field,wall temperature and thermal comfort of the results of CFD simulation and experiment are in good agreement,indicating that the established model can reflect the indoor thermal environment characteristicIn the end,on the basis of verifying the accuracy of the model that is verified by the system experiment,the model is used to predict and extend in this paper,and the thermal comfort under different radiant cooling is compared and analyzed.Through changing the initial wall temperature of radiation plates,the different indoor air temperature under different initial wall temperature can be obtained(29 ?,26 ? and 24 ? conditions).The result shows that,with the decrease of indoor temperature,the PMV change rate of decreasing becomes larger.The predicted value of PMV under the 26 ? condition is the closest to 0,which indicates that the thermal environment has the best comfort performance.Under the condition of 24 ?,the predicted value of PMV is much lower than the recommended value of ISO7730 standard,which indicates that the thermal environment of this condition can't be satisified by the requirement of comfort.At the same time,the numerical simulation of the capillary radiant cooling of the three terminals of the wall,the ceiling and the floor is carried out.The result shows that the vertical temperature difference of the floor radiation is the largest and and the average air temperature on the vertical height is the highest under the indoor air temperature of 29 ?.There is no much difference in the PMV-PPD of the three terminals and they all can meet the requirements of the ISO7730 standard,which indicates that the floor capillary radiation cooling can satisfy the requirement of thermal comfort.This paper provides a research base for the development and application of the unified terminal of radiant cooling and heating in the Yangtze River basin. |
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