Investigation On Performance Of Radiant Cooling Combined With Wall-attached-jet System

As a new type of air conditioning in recent years,ceiling radiant cooling panels has been widely used in China.It has many advantages, such as energy efficiency,high comfort, small pollution and so on,which are particularly relevant to today's problems that people closely watched—environmental protection,energy efficiency and indoor environmental quality.But at the same time,we have noticed that it is easy to condensation, limited in cooling capacity, and lack of fresh air and other shortages which restrict its popularization and application.Research emphasis of this paper is to study the effect of the radiant cooling combined with DOAS wall-attached-jet system on preventing condensation on the ceiling radiant cooling panel,along with the impact on indoor thermal environment when the settings of this combined system's performance parameters changed.Firstly, this paper examines the effect on preventing condensation on the ceiling of radiant cooling panel by using the wall-attached-jet system as the way of dedicated outdoor air supply.By constructing the test bench,we compounded ceiling radiant cooling panels and DOAS wall-attached-jet system,then conducted a simple comparative experiment between the combined system and ceiling radiant cooling panels+dedicated outdoor air system which using another air supply way.It was found that, compared to the latter, using the wall-attached-jet system supply air indeed can effectively prevent the occurrence of ceiling radiant cooling panels condensation phenomena.At the same time,due to the presence of convection brought by the wall-attached-jet system, the cooling capacity of the radiation cooling ceiling system was enhanced.After that, this paper also studied the CFD simulation on the application of this combined system in an actual room by using Fluent software.Through the analysis of indoor air temperature distribution, velocity distribution and relative humidity distribution near ceiling radiant cooling panel, we found that:although in this case the ceiling radiant cooling panel will not occur condensation, and the indoor thermal environment meet human needs, but there are limitations.In fact, this situation is the result of the dedicated outdoor air system,and the wall-attached-jet is failed to form due to the small volume of outdoor air and the low wind speed.Therefore,if the cooling load demand increases, the temperature of ceiling radiant cooling paneldecreases,then there is still the risk of condensation.The simulation results explain the causes of the comparative experiments' situation,also reflect the importance of using wall-attached-jet system on preventing condensation on the ceiling of radiant cooling panel.Thus, in view of the results of the experiments and simulations,this article continues on the case of CFD simulation research.By presenting a variety of wall-attached-jet system's setting conditions, comparing and analyzing the Jet attached conditions,the condensation of ceiling radiant cooling panel and the indoor thermal environment under different setting conditions of wall-attached-jet system,a setting condition was presented finally.This setting condition can guarantee the forming of wall attached jet under a limited amount of ventilation,prevent effectively condensation on the ceiling radiant cooling panel,and meet the requirements of indoor thermal comfort at the same time.The results provide some reference for the application of the combined air conditioning system in practical engineering.