In the design of finned tube heat exchangers, the installation position of the fins directly affects the heat transfer efficiency, and the fins should be installed on the side with a smaller convective heat transfer coefficient (α). The thermal resistance on this side is relatively high, and increasing the surface area of the fins can significantly reduce the overall thermal resistance and balance the difference in heat transfer capacity on both sides; On the contrary, the side with a larger alpha has lower thermal resistance, and the effect of adding fins is limited.
Example:
Boiler economizer: The flue gas side alpha (about 50 W/(m ² · K)) is much smaller than the water side alpha (>5000 W/(m ² · K)), and fins need to be added to the flue gas side.
Air cooler: The air side alpha (about 100 W/(m ² · K)) is lower than the liquid alpha inside the tube (>1000 W/(m ² · K)), and the fins should be placed on the air side.