Experimental And Numerical Investigation On Cooling Performance Of Capillary Ceiling Radiant Cooling Panel

Chilled water is supplied to capillary ceiling radiant cooling system at a higher temperature, which is available to achieve its specialty advantages for the perception of human thermal comfort and handle sensible heat load.Radiation heat exchange between radiant ceiling panel and indoor elements is the dominating way to cool thermal environment. And heat transfer process has relationship with the structure of radiant ceiling panel, supply water conditions and indoor environments. For traditional convection air conditioning system,capillary ceiling radiant cooling system is considered as an efficient way to deliver cold to a zone with smaller temperature gradient inside the room and decrease local thermal discomfort. The index of temperature non-uniformity coefficient was proposed to evaluate the uniformity of temperature distribution for ceiling panel surface in this paper. According to different panel structure,chilled water parameters and heat gain conditions, the methods of numerical simulation and experimental measurement in a test room with a radiant cooled ceiling panel were used to explore cooling performance of capillary heat transfer panel and temperature variation characteristics of indoor environment. The main contents were shown in the following aspects:(1) Considering the conductive heat transfer inside the radiant ceiling and convective and radiation heat transfer between ceiling surface and indoor environment, the heat transfer model of capillary ceiling radiant cooling panel was established. Chilled inlet water conditions(inlet water temperature andwater velocity), structural parameters(pipe diameter and tube spacing) and conditions of gypsum plaster(covering thickness and thermal conductivity)were presented as factors to influence the cooling capacity and surface temperature of heat transfer panel. The results of the simulation were compared with the values depicted in ASHRAE Handbook and the average difference was within the region of 15%. The capillary pipe diameter was determined to attain preferable value for capillary radiant panel.(2) The room model of capillary ceiling radiant cooling panel was based upon the dimensions of the test room and capillary tubes installed inside the ceiling. The experimental data was boundary conditions of modeling calculation.The temperature difference between simulation and experimental data was in range of 10%. The model presented in paper was used to explore the effect of chilled water flow and heat source intensity to radiant indoor environment.(3) The experimental systems of capillary ceiling radiant cooling panel were set up and measurements in a test room were conducted in paper. Chilled water temperatures and supply air conditions were considered as influencing factors to affect the temperature uniformity and variation characteristics of ceiling surface and indoor air temperature distributions at different vertical and horizontal levels.