Simplified Prediction Method of Vertical Temperature Distribution for Impinging Jet Ventilation System

Tomohiro Kobayashi,Noriko Umemiya,Toshiya Nishiumi,S.I Tanabe,G Cao,L Mazzarela,P Wargocki,I Nastase,H Zhang,M.C Gameiro Da Silva,J Kurnitski,C Inard

doi:10.1051/e3sconf/201911101097

Abstract

The impinging jet ventilation (IJV) system is an air-distributing strategy to generate a thermal stratification in a room by supplying the air vertically toward the floor, which provides higher ventilation effectiveness than mixing ventilation. To date, however, no simplified prediction model of indoor thermal environment for an impinging jet ventilated room has been established. Therefore, this study aims to propose a simplified calculation model based on “Block Model”. This paper first presents a parametric study using Computational Fluid Dynamics (CFD), where total supply airflow rate of a test room is changed as a parameter. The number of terminal is also changed. Secondly, the paper presents the simplified calculation model of vertical temperature distribution based on block model that solves heat flow by advection and diffusion. Here, in this prediction model, the most important parameter is the turbulent thermal diffusivity between two room-space blocks in vertical direction. The room-space blocks are classified into two types, i.e., lower and upper part of a room. Based on parametric study using CFD, turbulent thermal diffusivity is arranged for lower and upper block respectively, and it is finally shown that the vertical temperature distribution from block model well agrees with CFD result.

Highlights

The air distribution system inside a room is of great importance because it has a significant impact on the indoor thermal environment
It is generally known that the impinging jet ventilation (IJV) can combine both advantages of the displacement ventilation (DV) and mixing ventilation (MV) due to a medium momentum supply [1]
This paper presented the parametric study of a room with IJV system by using Computational Fluid Dynamics (CFD) where total supply airflow rate and number of inlet terminal were changed, and 12 cases were analysed in total

Summary

Introduction

The air distribution system inside a room is of great importance because it has a significant impact on the indoor thermal environment. In addition to providing thermal comfort, energy efficiency of air-conditioning system needs to be carefully considered as well. In this viewpoint, the air distribution system for occupied zone has attracted many interests. The impinging jet ventilation (IJV) system, which is relatively new air distribution system has been attracting increasing attention during these last two decades. In this system, the air is supplied downwards onto the floor and spreads over a room as a layer with its momentum decreasing gradually. The IJV system has a possibility to be applied as heating system as well

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Conclusion