Quantitative investigations on setting parameters of air conditioning (air-supply speed and temperature) in ventilated cooling rooms

Abstract

Rational and scientific design of indoor air conditioning is essential. In the design of Heating, Ventilating and Air Conditioning system, air-supply speed (ventilation rate) and air-supply temperature are the two most important parameters. In the current study, numerical simulations and experimental measurements were adopted to investigate the influences of ventilation mode, air-supply velocity and air-supply temperature on indoor thermal comfort as well as building energy consumption in summer. Different ventilation modes (up supply and down exit, ceiling supply and ceiling exit) were considered in modelling. Based on the simulation and experimental results, dimensionless index $Gr/{Re}^2$ is proposed, which represents the ratio of buoyancy weighting force to inertial force. This index can be used as a pre-evaluation index of indoor thermal comfort in preliminary design of air conditioning. It is an indicator to judge the working conditions in cooling-ventilated rooms. When ${10}^{-6}<\frac{\mathrm{Gr}}{{Re}^2}<{10}^{-5}$ , the settlement and diffusion effects of indoor airflow reach a good level, which means that the parameter setting could provide a comfortable indoor thermal environment. The dimensionless number $Gr/{Re}^2$ is a theoretically based tool in the pre-evaluation of indoor thermal environment, providing guidance for setting of ventilation design parameters.