Experimental Study On Combustion And Heat Transfer Characteristics Of Porous Midea Gas Water Heater And Prototype Design

Nowadays, the shortage of global energy resource and the problem of climate change, energy conservation and pollution reduction has become a central theme of economic development in our country. Porous media using to increase the heat transfer performance is a new material, which applied to the gas water heater, the thermal efficiency of gas water heater will be increased, the amount of pollutant emissions and the size of gas water heater will be reduced.With the application of the porous media in the combustor, the temperature of combustor is improved greatly, thus the material's life has been reduced. Not only control the temperature of combustor, but also improve the thermal efficiency of gas water heater effectively has become a key technology of the porous medium application in gas water heater.First, in this thesis, the influence of the cooling conditions on the combustion and heat transfer characteristic of porous medium combustor was studied, the curve of the combustor's temperature and pollutant emission was obtained. In the certain conditions of chamber area and fire rating, the greater the water flow rate, the better the cooling was. In this paper, the absorption heat of water is defined ciritical heat when the combustion chamber temperature is a certain value. According to energy conservation, the critical heat transfer equation is derived and calculated based on this formula, compared with the experimental value, experimental and theoretical values can fit well. And consequently, the heat exchanger surface heat transfer coefficient and heat transfer relationship is obtained to guide the design of porous media gas water heater. Cooling conditions have a great impact on the combustion temperature of porous media and its burning emissions. In the certain burning intensity and combustion chamber size, the better the cooling conditions, the lower the combustion temperature is, the higher levels of CO in the combustion pollutants and the lower NOx emissions are。 Second, according to national standard, the helical coiled porus media gas water heater is designed, and there performances are validated. Experimental results showed: the thermal efficiency of porous medium gas water heater is far higher than the requirements of national standard. In some conditions, the thermal efficiency is more than 100%, the pollutant emission and the temperature of fume are lower than the requirements of national standard. These studies show that the development of porous media gas water heater is necessary. However, there need a few improvements on his type of gas water heater for some deficiencies. A long circular coiled tube porous gas water heater is brought in, and then the correctness is verified by the experiments. The result is, smoke enter from nozzle, and come from under the nozzle, which can effectively reduce the content of CO and NOx in the flue gas, also, the thermal efficiency and other indicators of tests are far higher than the requirements of national standard.The results of this thesis provide the experiment date and theoretical basis for the research and development of porous media gas water heater.