天花板辐射供冷系统的性能研究

Research on the Performance of Chilled-Ceiling Radiant System

冷天花板辐射供冷系统是一种舒适、节能的新型空调型式。系统的供冷能力和天花板表面温度及系统运行达到稳态所需的时间是系统设计、运行的关键参数,揭示各因素对它们的影响规律是十分必要和重要的。本文建立了顶部保温时的天花板辐射供冷系统的动态传热数学模型,应用有限单元法进行求解,分析了埋管深度、间距、管材以及供冷水温、水量等因素对天花板表面温度、系统供冷能力和达到稳态所需的时间的影响规律。结果表明:埋管深度越大,埋管间距越大,天花板表面温度越高,供冷能力越小;管材对系统的供冷性能影响不大;系统的供水温度越低,天花板表面温度越低,系统提供的冷量就越大。冷水温度宜取16～20℃之间;埋管越深,埋管间距越大,系统达到稳态时间越长;初始温度越高,供水温度越低,系统达到稳态的时间越长。

Chilled-ceiling radiant cooling system is a new type of air-conditioning systems, which can provide more comfortable indoor environment efficiently. Cooling capacity and surface temperature of the chilled ceiling and the time of the system reaching steady-state are very important parameters for system design and operation. Therefore, it is necessary to reveal the relationships between the parameters and their influential factors. To this end, a transient heat transfer mathematical model of the chilled ceiling with insulation above was developed, and Finite element method was used to solve the problem. The influence of tube buried depth, tube space, tube material and supply chilled water temperature and flow rate on the surface temperature and cooling capacity and the time of reaching steady state are analyzed. It is found that increase in tube buried depth and tube space lead to the rise in surface temperature of the chilled ceiling, cooling capacity drops as well. Tube material has little influence on the system performance. It is also shown that lower chilled water supply temperature may cause surface temperature to drop and cooling capacity to increase. It is suggested that chilled water supply temperature be between 16-20℃. However, the increase in tube buried depth and tube space may lengthen the time of system reaching steady state. It takes longer time for the system to achieve steady as initial temperature is higher or the chilled water supply temperature is lower.