Research On Heat Transfer Characteristics Of Prefabricated Ceiling Radiant Cooling

Cooling radiant ceiling panel has been gaining high attention by researchers.However,the non-uniformity of cooling radiant ceiling panel surfaces cause the condensation problem in the low temperature regions,which limit more extensive development of radiant cooling panels in hot and humid areas of china.The radiant ceiling cooling system types like the pipes in the concrete or capillary have the disadvantage of post-maintenance difficulties if the tubes of panels occur leakage.Based on above problems,this paper presents a mathematical calculation model for prefabricated ceiling radiant cooling panels with air layer and straight tube arrangement,as it is satisfied with the demand of modern assembly market and beneficial to solve local condensation caused by non-uniform surface temperature distribution of panels.In order to more accurate analyze the influence of different factors on the performance of prefabricated ceiling radiant cooling panel,the index of temperature non-uniformity coefficient as well as cooling capacity are introduced to comprehensively evaluate the structure and chilled inlet water parameters of radiant panels on the the effects of surface temperature distribution and cooling characteristics under the conditions of considering the tube thickness and plate thickness.A computational fluid dynamics(CFD) is used to calculate the heat transfer models,which was verified by experimental data.The specific research contents were divided into the following aspects.(1)This paper reviewed the structural characteristics of prefabricated ceiling radiant cooling panels with air layer and straight tube arrangement for heat exchange.Considering conductive heat transfer inside panels and convective and radiant heat transfer inside air layer.Moreover,the heat transfer process in the radiant panel was analyzed theoretically.The convective heat transfer coefficient between panel surface and indoor environment was obtained by theoretical calculation.(2)The experiment was conducted in the radiant air-conditioning laboratory platform.To test metal panel surfaces temperature,there were 12 measuring points in the ceiling panel under different supply chilled water parameter.On the basis of the structure of experimental model,a simplified physical model was established and the experimental inlet water parameters were used as simulated boundary conditions.The relative error between the measured results and simulation data was within the region of 15%.Then,Heat transfer models of prefabricated ceiling radiant cooling panels with different structures was established.This paper tried to explore the influence of chilled inlet water parameters(temperature,velocity) and structural parameters(tube distance,plate thickness,air layer thickness,tube thickness) on surface temperature of ceiling panel and its cooling capacity.(3)Comparing to uniformity of the surface temperature distribution between the prefabricated ceiling radiant cooling panel and the original radiant ceiling panel(concrete or capillary ceiling radiant cooling panel) under the same cooling capacity.