Heat transfer characteristics of parallel and counter flow micro-channel heat exchangers with varying wall resistance

摘要

Thermal behaviours of parallel and counter flow micro-heat exchanger are investigated numerically, with emphasis on the role of wall resistance and thermal entry effects. The influence of different parameters, such as, thermal resistance (/?), Knudsen number (Kn), effectiveness (e) and Number of Transfer Units (NTU) are investigated. It is found that the temperature jump at the walls increases with increasing R and Kn. On the other hand, the NTU increases with decreasing R and Kn. Furthermore, for counter flow, thermally fully developed flow may not exist over a large section of the heat exchanger due to the heat conduction in the separating wall and the entrance region.