Analysis for optimal positioning of kitchen ventilation fan

This aim of the study is to determine the optimal position of ventilating fan in a kitchen. Experiments were conducted in a kitchen of a double-storey house at Subang Jaya and a constructed chamber inside Thermodynamics Laboratory, Universiti Putra Malaysia. The purpose of this study was to determine the best location for a kitchen exhaust fan and to prove the effectiveness of the use of fan. The experiment in Subang Jaya was based on the CFD (Computational Fluid Dynamic) result and the fan was moved to the midway above the window. The chamber at UPM had seven position of fan frames hence the fan could be removed from one frame to another to determine the optimum position to install the fan. Both experiments used CO2 as tracer gas to measure the air exchange rate. CO2 was injected into space in excess of 1000 ppm, and advanced to mixed with the air with the help of fan for ten minutes, before determining the value of air exchange rate. The data was taken every 5 minutes within 30 minutes to one hour. The Location of ventilating fan is crucial for effectiveness of contamination removal in kitchen. From CFD and experiments, it is concluded that the best location for ventilating fan in the kitchen is mid-way above the window on external wall. The result of the chamber at the lab showed that at height 3.6m the air exchange rate ranged from between 2.3 – 2.0 h-1for door fully opened and 2.1 -1.8 h-1 for door closed. At height 3.0m the air exchange rate ranged from between 2.3 – 2.0 h-1 for door fully opened and 1.9 – 1.7 h-1for door closed. And at height 2.5m the air exchange rate ranged from between 1.8 – 1.6 h-1 for door fully opened and 1.6 – 1.5 h-1for door closed. Use of extract fan could increase the air exchange rate from 0.3, which was the obtained result from the measurement of the chamber in its original condition, when the fan off and the door is closed to 1.5 h-1 which was the worst result obtained with the fan on when the measurement was taken with the door closed and at lowest height of the wall. That was an increase of 4 – 5 times. The best fan position is on the highest mid point for all wall height of 3.6m, 3.0m and 2.5m. The CFD trend and result for chamber at different heights showed that the best fan location is at the highest mid point of the wall. Those experiments proved that the result is consistent for both laboratory and site experiments.

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