Experimental Study Of Pool Boiling Heat Transfer Characteristics Of R22 On Horizontal Tube

The boiling heat transfer outside the horizontal tube bundle is widely used in the full liquid evaporator in the refrigeration industry.Study on the boiling heat transfer characteristics of refrigerant R22 in the form of R22 is a tube boiling fluid and water internal heating.The diameter of copper 20 mm as the boiling surface,by changing the tube with hot water inlet temperature and flow rate to change the boiling heat flux heat transfer process,obtained the experimental phenomena of pipe boiling and tube boiling heat transfer performance.1 The difference between the inlet temperature of the heating water and the saturation temperature of the refrigerant is 4.5 °C and the flow rate is 0.35 m3/h,the outer tube will have a small amount of bubbles;When the heating water inlet temperature and the refrigerant saturation temperature difference of 8.5 °C and the flow rate is 0.49 m3/h,the boiling heat transfer coefficient outside the tube is much smaller than that of Ribatsk correlation,boiling state has not reached nucleate boiling;the heating water inlet temperature and the refrigerant saturation temperature difference of 12 °C and the size of the flow is 0.73 m3/h,boiling heat transfer coefficient and smaller deviation of Cooper,then boiling in nucleate boiling state.2 Making the pressure of refrigerator R22 is in the range of 0.84 MPa,0.86 MPa,0.88 MPa,regulating hot water inlet temperature of the tube and heating water flow to change the size of the heat flux,the heat flux density var iation range was4000~45000 W/m2.The maximum deviation of the boiling heat transfer coefficient outside the tube with the theoretical formula calculated by Ribatski formula is no more than ± 20%,which is in great deviation from the theoretical value of Cooper.It is found that the heat transfer coefficient increases linearly with the increase of heat flux at the same saturation pressure.3 Contrast the relationship between the heat transfer coefficient inside and outside the tube,The refrigerant of R22 saturation pressure is controlled in the range of 0.81~0.82 MPa,0.84~0.85 MPa,the heat flux density in 6000~12000 W/m2.Conclusion that the heat transfer coefficient is small,but the heat flux reached 12000 W/m2,tube refrigerant boiling heat transfer coefficient is much higher than convection heat transfer in tube.