Research PaperResearch on the heat and mass transfer characteristics of fin-tube exchanger under low pressure environment

- The mass transfer process is greatly infected by low pressure in wet condition.
- The performance parameters have different variation in low-pressure environment.
- The boundary layer is the main cause for the change of evaporator performance.
- The main forms of heat transfer in different fin sections are different.

China has rapidly developed in recent years, with highlands (for example, the Qinghai-Tibet Plateau, with average altitude over 4000 m, the environmental pressure is less than 60 kPa) being increasingly utilized; leading to a greater application of the heat exchanger due to the need to deal with low pressure environments of the higher altitudes. This paper focuses on the heat transfer and flow characteristics of a plate-fin heat exchanger under low pressure environment and wet condition. By means of theoretical analysis, the main performance parameters changing with the environmental pressure in the air side of heat exchanger were derived, and the performance of a plate fin heat exchanger was tested under low pressure and humidity conditions on the test bench. The results indicate that the heat transfer performance of heat exchanger decreased with the decrease of environmental pressure under wet condition. Compared with that under the atmospheric pressure condition, the latent heat transfer and mass exchange of the plate-fin heat exchanger had reduced by about 65.1% and 65.6% respectively at 61 kPa condition. To explore the mechanism of how low-pressure working on the latent heat transfer and flow characteristics of heat exchangers, the heat transfer and flow process of heat exchanger under low pressure and humidity conditions were simulated. The results showed that the performance decline of heat exchanger was closely related to the dramatic changes of mass transfer process and concentration boundary layer under low pressure environment.