Effect of ambient pressure on air side heat transfer and flow characteristics of plain finned tube heat exchanger

Abstract

Ambient pressure influences on air side heat transfer and flow characteristics of plain finned tube heat exchangers are systematically estimated. Theoretical analysis showed that ambient pressure had impact on the development and separation of boundary layer while air flowed around tubes. Under the experimental conditions, air side heat transfer coefficient dropped by 38.46%–44.12% and jh factor rose by 35.66%–51.89% when the ambient pressure reduced from 100 kPa to 40 kPa. Both row number and fin pitch effect existed at lower ambient pressure, only being less pronounced. Air side heat transfer coefficient corresponding to the same Re decreased as ambient air pressure reduced. The ambient pressure ratio correction index is between 0.27 and 0.49 when the Re is the same.