地板送风系统的人体活动区域冷负荷计算的一种数值方法

A Numerical Method to Predict Cooling Load in Occupied Zone for Floor Level Supply Air-distribution System

地板送风系统的室内空气分层现象对准确预测系统能耗非常重要。对该系统,本文提出了一种冷负荷减少系数方法来简单而快速的计算人体活动区域的冷负荷大小。首先,把室内热源类型分为墙体、人体、电器设备和照明四种,以定热流作为边界条件,利用计算流体动态(CFD)模拟方法可以获得人体活动区域的冷负荷Qoccupied。其次,基于同样的边界条件,对上述四种不同热源单独进行数值模拟,得到人体活动区域四个不同的冷负荷减小系数α,从而得到加和冷负荷Q′occupied。本文分析了一种回风口与排风口分别位于房间中部和天花板上的地板送风系统,通过数值模拟发现Qoccupied与Q′occupied的偏差在10%以内。由于模拟计算单一热源的冷负荷减小系数非常简单,所需时间也远小于前者(Qoccupied计算),采用加和计算冷负荷的方法在工程上是切实可行的。对该地板送风系统,作者的最终目的是要建立一个冷负荷减小系数数据库,以简化整个人体活动区域冷负荷的预测方法,从而为工程设计应用提供一种实际可行的冷负荷估算方法。

In the underfloor air distribution （UFAD） system, the indoor air stratification plays an important role for the accurate prediction of system energy consumption. How to easily and quickly quantify the cooling load in the occupied zone is significant for practical design of engineers. In this article, the authors proposed a CFD （Computational Fluid Dynamic） simulation method to generate the reduction factor for the cooling load estimation in the occupied zone. In this method, the sources of indoor heat gains are classified as wall, occupant, electrical equipment and lighting. Based on the heat flux from heat sources as boundary conditions, CFD simulation is firstly employed for the UFAD system to obtain the total cooling load Q occupied in the occupied zone. Secondly, CFD simulation is individually used for four different heat sources based on the same inlet and outlet conditions as the above simulation. After this step, the individual cooling load reduction factor in the occupied zone can be obtained. Then, the sum of cooling load from different heat sources can be defined as Q＇occupied With the simulation work on a small office room with ceiling exhaust and mid-level return air, it is found that the discrepancy between Qoccupied and Q＇occupied is less than 10% . Due to the simple and easy simulation for individual heat source, the eventual effort is to develop a database for the cooling load reduction factors in order to reduce the design cost for the UFAD system with ceiling-level exhaust and mid-level return configuration. With this database, engineers can easily estimate the cooling load in the occupied zone for HVAC system design.