Investigation of pot-skirts, loading heights and finned pot arrangements for improved thermal efficiency of gas cooking system

Abstract

In Bangladesh, the natural gas (NG) consumption in cooking is a significant portion of total NG consumption. The socio-economic status of the people and the price of electricity hinder the adoption of clean and efficient electric cookers in Bangladesh. Therefore, techniques for increasing the efficiency of existing NG cooking systems are vital to reduce NG consumption. In this study, several configurations of pot-skirts (e.g., single layer and double layer metallic pot-skirts with and without rockwool insulation), and pots (standard flat bottom pot and modified finned pot) were experimented with conventional partially premixed radial port household NG burner for better thermal and emission performances. To optimize the operating conditions thermal performances, e.g., thermal efficiency, modified combustion efficiency (MCE), and heat transfer efficiency (HTE), and environmental performances (CO/CO2 ratio and CO emission) of the designed configurations were carried out at different NG supply pressures (4 to 18 mbar) using the standard water boiling test (WBT) protocol. The pot-only configurations (standard flat bottom pot and modified finned pot) were tested for different pot loading heights (PLHs) at different NG supply pressure from 4 to 18 mbar whereas; those pots with pot-skirt configurations were tested at a fixed PLH for different flue or channel gaps varied from 3 to 15 mm. The environmental performances e.g., CO/CO2 ratio and CO emission, were studied to determine the in-depth environmental feasibility of the cooking system. The modified finned pot with rockwool insulated double-layer pot-skirt performed the best among all configurations. Thermal efficiency of 66% with a 6 mm channel gap at 10 mbar NG supply pressure was obtained for this configuration, which was 32% higher than the maximum baseline efficiency (50%) of the NG burner for pot-only configuration with ordinary flat bottom pot. The simple addition of pot bottom fins with insulated double layer pot-skirt significantly contributed to the energy conservation of NG cooking system. However, the experimented NG burner with modified finned pot and insulated double layer pot-skirt can be operated safely at the highest efficiency both in vented and unvented kitchens without stretching the environment as per WHO guideline value. Thus, the modified cooking system can be an efficient approach for saving a huge amount of cooking NG in Bangladesh without hampering the environment.