The tubeside mean metal temperature is determined for the calculation of the differential thermal expansion.
There are various published methods that determine Outside Film Heat Transfer Coefficients. The effects of the baffles, lane and window leakages are used to correct the heat transfer...
The designs of the kind are carried out in sophisticated softwares like HTRI and HTFS.
This is a typical air cooled heat exchanger, wherein the air is being heated with hot water.
The coil configuration is the most important aspect. Depending on the flow of the hot water, you could have...
Heat transfer to the ambient air is through natural convection. You could read the articles and the procedure to calculate natural convection coefficient for your application.
You could refer to any heat transfer calculation book or Perry's handbook.