Numerical Simulation Study Of Displacement Ventilation In Catering Kitchen

The China catering kitchen environment is featured with high temperature, severe oil smoke pollution and unreasonable air distribution. The abominable indoor in kitchen can affect staff's health and decrease working efficiency. Displacement ventilation, which can supply favorable air distribution and increase air quality and thermal comfortableness, has been applied in designs of office and industry buildings. The displacement ventilation is firstly used in the design of China catering kitchen in this paper. The physical model for a model kitchen is established. The calculation method is proved accurate by comparing between numerical results and experimental results of velocity fields and temperature fields of model kitchen. Different ventilation parameters are designed for a practical project kitchen. Numerical simulation of the kitchen is established by using Airpark. The velocity fields, temperature fields and CO₂ distributions in different positions are analyzed, and the laws of air age and PPD-PMV values are also studied. The results of this paper are provided beneficial exploration for the using of displacement ventilation system in catering kitchen. The main work and achievements are outlined as follows:1. The indoor environmental features of catering kitchens in China are summarized, and evaluation indicators of indoor environment in kitchen are analyzed. Development situations of displacement ventilation are briefly introduced, and by comparing the design features of displacement ventilation and mix ventilation, it is found that the displacement ventilation can increase indoor air quality and ventilation efficiency.2. Numerical simulation of model kitchen is established using Airpark with zero equation models. The kitchen is supposed to be a closed space. The model and calculation method is proved accurate, fast and concise by comparing between numerical results and experimental results of velocity and temperature fields of model kitchen.3. The physical model is simplified by using condition of a practical project kitchen. 16 different ventilation programs are designed for simulations through changing ventilation conditions including ventilation velocity and temperature. Velocity fields, temperature fields, CO₂ concentration distributions and air age features are analyzed, and PMV-PPD indicators are also compared. The applicability of displacement ventilation using in catering kitchen and the effects of different ventilation parameters on indoor environment are finally analyzed. The main conclusions are as follows:(1) The integrated air flow distributions are stable, and air in human breathing area is fresh by displacement ventilation. The working area temperature is decreased and the vertical temperature gradient is increased with the decreasing air supply temperature under the same air supply velocity. The vertical temperature gradient is increased with the decreasing air supply velocity under the same air supply temperature. And designed air supply velocity should be less than 0.25m/s to avoid cold blow feeling for most of people. Air supply temperature should also be not less than 20℃for decreasing vertical temperature difference and increasing comfortableness.(2) The ventilation temperature has little effect on CO₂ concentration distribution by using displacement ventilation. Pollutant distribution is controllable and CO₂ discharging is contributed by increasing ventilation velocity. In addition, increasing velocity and decreasing temperature will decrease PMV values and increase PPD values.(3) The results, obtained by comparing the simulation results, show that the indoor air flow distribution of kitchen is reasonable, and pollutants of cross-inflections are decreased by using displacement ventilation method. In addition, air exchange efficiency of displacement ventilation is higher than 100%, which is obviously higher than that of mix ventilation.The catering kitchen is a special construction. The advantages of displacement ventilation are fully reflected in catering kitchen. Residual heat is effectively removed, and temperature distribution and air quality are also improved by using displacement ventilation. Ventilation parameters must be strictly controlled to avoid excessive high velocity and sharply low temperature.