Experimental Study On Condensation Heat Transfer Of R290 In Small Tube

With the aggravation of greenhouse effect,limiting the use of high GWP refrigerants has become a trend.It has become an urgent problem to search out environmental-friendly alternative refrigerants of R22.R290 has been treated as ideal alternative refrigerants due to their favourable environmental and thermo-physical properties.However,the flammability hindered its use.In order to reduce this risk,the charge amount of R290 in the refrigeration system should be reduced,while the outdoor unit of household air conditioner composed of condenser and compressor is prone to the risk of hazard.Therefore,the condensation heat transfer of R290 in the small diameter horizontal tube should be studied.The main works are as follows:The experimental platform of R290 flow condensation heat transfer was designed and built,and the experimental of condensation heat transfer of R290 in small tube was studied.The experiments were performed at smooth tube and micro-fin tube withthe diameters of 6mm and 4mm.Data are presented for the following range of variables: saturation temperature(40?,50? and 55?),mass flux(100–300 kg/m2s),vapor quality(0–1)and heat flux(3–10 kW/m2).By the experiment,the influence of vapor quality,mass flux,saturation temperature and heat flux were analyzed.The results show that the condensation heat transfer coefficient of R290 will be increased by the increasing mass flux and vapor quality under certain conditions.Under the same conditions,the condensation heat transfer coefficient increases with the increase of heat flux and the decrease of the tube diameter,but decreases with the increase of saturation temperature.The condensation heat transfer coefficient in micro-fin tube is greater than that in smooth tube,but the enhanced heat transfer performance of micro-fin tube would be reduced at high vapor quality region.The results also show that the influences of mass flux and saturation temperature in different type tubes are not the same.It is suggested that have an optimum heat flux in the condenser design of R290 makes the designed condenser have the best heat transfer performance under the general conditions and consumption less.By comparing the prediction data of Chang,Cavallini,Thome,Yu,Kedzierski correlations and the experimental data,the advantages and disadvantages of existing correlation are analyzed.It is pointed out that optimization by using the flow pattern and fitting the data by specialized study can improve the prediction accuracy of correlations.In the existing correlations,Cavallini correlation predicts best,Thome correlation predicts better of smooth tube,and Chang,Thome,Yu and Kedzierski correlations predict poor of micro-fin tube.