Experimental Study Of Pool Boiling Heat Transfer Characteristics And Heat Transfer Enhancement Of R245fa On Horizontal Tube

With the development of economy and society,people pursue higher quality of life and fresher food To achieve these goal,refrigeration technology is developed rapidly.Evaporator plays an important role in the refrigeration system.Flooded evaporator is one of the type of evaporators,which has many irreplaceable advantages.It is of great significance to study the flooded evaporator.Nowadays,there are many problems in the environment.More attention should be paid to environmental performance of refrigerant.To solve these problems,new refrigerant should be found.Therefore,the boiling heat transfer characteristics on horizontal tube with R245fa is studied.The experiment is carried on the smooth tube and reinforced tube.The diameter of the smooth tube is 20mm and the diameter of the reinforced tube is 18.9mm.They are both1000mm in length.The boiling heat transfer coefficients are got with thermal resistance analysis and the law of change with heat flux and pressure are also got.Moreover,the experimental correlation is calculated.The main results are as follows:1.When the evaporation pressure is 200kPa and the heat flux increases from 1×10⁴W/?m²?K?to 2.5×10⁴W/?m²?K?.The boiling heat transfer coefficient of R245fa on the smooth horizontal tube shows an upward trend.Especially,in this condition,when the heat flux goes to 2.5×10⁴W/m²,the boiling heat transfer coefficient reaches 4×10³W/?m²?K?.2.When the heat flux is under the same condition.The boiling heat transfer coefficient on the smooth tube under the pressure of 140kPa,160 kPa,180kPa and 200kPa.The data shows that the boiling heat transfer coefficient on the smooth tube increase with the growth of presue.3.The experimental data of boiling heat transfer of R245fa outside the tube are fitted using least square method and the following experimental heat transfer correlation is obtained:h?28?1.184357 p^0.2841q ^0.6343.The error analysis reveals that the experimental correlation has a deviation of 8%with experimental data,when the pressure in the range from 120kPa to 250kPa and the heat flux from 4×10³ W/m² to 1×10⁴ W/m².4.When the heat flux is under the same conditions,the boiling heat transfer coefficients on the reinforced tube increase with the growth of pressure when the pressure is under the same condition,the boiling heat transfer coefficients of R245fa on the reinforced tube increase with the growth of heat flux.5.Comparing to the test data of smooth tube,the study shows that the heat transfer enhancement ratio of R245fa boiling outside the enhanced tube is bigger than 4.