Research On Unsteady Characteristics Of Capillary Ceiling Radiant Cooling Systems

Capillary ceiling radiation cooling panels(C-CRCP)is a new terminal device of air conditioning,which has been gaining much popularity because of high efficiency energy saving and high thermal comfort.Currently,the research on C-CRCP systems mostly focused on optimizing heat transfer model,analyzing heat exchange performance and heat comfort under the conditions of steady state.As well as some research on energy-saving and control of C-CRCP systems were introduced.In fact,there is a dynamic heat transfer process of C-CRCP systems due to the influence of panel structure parameters,chilled water parameters and supply air conditions.The research on unsteady cooling characteristics of C-CRCP systems is deficient in present.The research works of this paper are used by the methods of theoretical analysis,experimental study and numerical simulation.The main contents of this paper as following:(1)The heat transfer process inside capillary radiant panel and between panel and indoor environment were analyzed theoretically based on the heat transfer characteristics of C-CRCP systems.The index of effective utilization rate of cooling capacity was proposed to evaluate the contribution of ceiling cooling capacity to the room.The distributions of temperature in workspace were analyzed by temperature non-uniformity coefficient.(2)Experimental measurements of the C-CRCP system were accomplished in a test room.Five inlet water temperature(15.3??16.2??17.2??18.3??19.5?)and four supply air conditions(two supply air temperature 20.3??22.7?and two supply air velocity0.86m/s?1.36m/s)were measured used by SWEMA Y-BOAT-100multi-function measurement system.The time variations of ceiling surface temperature and indoor air temperature with different conditions were obtained by the measurements.(3)A room model by reference to test room of C-CRCP with the size of 4m×3.8m×3m(length×width×height)was established by the method of CFD numerical simulation.Multiple impact parameters,including gypsum plaster thickness(10mm?20mm?30mm)and thermal conductivity(0.75?1.0?1.25?1.5?1.75 W/(m~2.K)),inlet water temperature and inlet water velocity(0.15m/s?0.55m/s?0.95m/s),supply air temperature(17.9??19.1??20.3??21.5??22.7?)and supply air velocity(0.56m/s?0.86m/s?1.16m/s?1.36m/s?1.56m/s),were considered by unsteady numerical simulation to explore the dynamic variation rules of C-CRCP systems.The relative error between the experimental data and simulation results with inlet water temperature and supply air conditions were less than 10%.