Numerical Study of Emission Control of Urban and Rural Kitchens for Healthy Environment

Abstract

Lack of proper ventilation of exhaust fumes from gas and biomass fired stoves in both urban and rural residential kitchens are a major health concern for majority populations. It could even cause destruction of property, reduced quality of life and lifespan. In this research, a typical urban kitchen with a standard dimension of 2.13m × 2.43m × 3.05m was modeled with single open door exit. Two heat sources were used to resemble the double burner gas stove of an urban residential kitchen. On the other hand, a single burner traditional soil stove was used for the model of a rural kitchen with dimension of 3.50 m × 2.20 m × 1.85 m. In both cases, steady state simulations were performed using a three dimensional CFD code with appropriate boundary conditions. The present numerical method for urban kitchen was validated by comparing with the experimental data and showed very reasonable agreement. A grid independence test was also performed to determine the optimum grid resolution reflecting the accuracy of the numerical solution. For urban kitchen, the results are presented for temperature field and velocity field, and CO2 concentration and discussed under both natural forced ventilation systems. For the gas stoves located in the kitchen corner, the flow tends to shift towards the corner side wall and exhibits high temperature zone all above the burners. A comparative analysis between the ventilation (natural and forced) and no ventilation conditions are reported. Very high concentration (above 5000 PPM) of carbon dioxide gas was observed at the plane passing the breathing zone. Exposure to this environment for longer time may cause serious health damage of the occupants. A kitchen hood system has been simulated for both thermal comfort and carbon dioxide gas emission for the kitchen. It has been observed that the carbon dioxide gas concentration significantly reduced within the breathing zone due to use of kitchen hood system. In the breathing zone, the CO2 concentration is only about 500 PPM which is 10 times lower than the close vent case. Two other positions of the kitchen hood suction have been studied for the effect of thermal distribution and emission rate. It has been observed that both front and base extraction method 19 reduces the emissions significantly to well below the safe limit. They also can maintain thermal comfort quite well inside the kitchen space. For the rural kitchen study, varying intensity of emissions of CO, CO2 and Particulate Matter (PM) from different kinds of Bio-fuels burning have been investigated. Dispersions of these pollutants in the kitchen space have been investigated for without ventilation and natural ventilation without hood and with hood systems. It has been observed that at unventilated condition, CO, CO2 and PM concentration exceeds safe standard value. Even the natural ventilation condition fails to keep the concentration below the safe limit. However, a significant improvement can be observed for the kitchen with hood under natural ventilation.