Study On Start-up And Heat Transfer Performance Of Pulsating Heat Pipe With Refrigerants

Pulsating heat pipe (PHP) belongs to new-type heat pipe, and it’s regarded as a very promising and potential heat transfer component. Relatively, PHP with refrigerant belongs to a low-temperature and high-pressure system, and it has a great difference between PHP with conventional working fluid. The investigation about PHP with refrigerant is still very little, and its heat transferring mechanism and performance are still not clear. Through many experiments of PHP with different refrigerants, this paper investigates the startup and heat transfer performance. After that, the results are contrasted to that of PHP with conventional working fluids.Different refrigerants are chosen as the working fluid of PHP and different inner diameters of PHP are chosen. Many factors influencing the startup and heat transfer performances of PHP were studied. The non-dimensional correlations predicting thermal resistant and startup time were suggested and verified. Also, the model of Mass-Momentum-Energy for PHP was improved in this paper.A PHP experimental system has been constructed for the study of heat transfer performance of PHPs with different working fluids and different IDs. The results indicate that the startup time can be kept in 2 minutes in all working conditions for the PHP with R134a when filling ratio is 49.89%. The shortest startup time is 11s in this paper’s experiments under the working condition of 49.89% and 100W. The thermal resistant for low filling ratio lies in a higher level in contrast with other working conditions. The startup performance of R600a is better than that of R134a and R404A, but the thermal resistant has the largest value, and R134a’s thermal resistant is the smallest. R404A is the best refrigerant to work under relatively lower temperature range. The PHP whose ID is 2mm has the shortest startup time, lowest startup temperature and smallest thermal resistant.In the method of fitting, the two non-dimensional correlations predicting thermal resistant and startup time were attained. After being checked out, it’s ensured that these two non-dimensional correlations are effective. In the theoretical study aspect, a simplified meniscus model was introduced in this paper, and is put into the theoretical PHP model for improving old model. Also, the improving model has taken account the surface tension and the contact angle drag resistance, and the numerical simulative results show that the amplitude and frequency for mass and pressure of vapor slugs change a lot in contrast with the existed model which has not been improved.