Under normal conditions, what most greatly affects the rate of heat transfer in a feedwater heater?

The rate of heat transfer in a feedwater heater is primarily influenced by the temperature differential between the steam and the feedwater. This temperature difference drives the heat transfer process; the greater the difference, the more effective the heat transfer will be. In thermodynamics, this principle is related to the concept of thermal gradients – heat naturally flows from a higher temperature area to a lower temperature area, and the rate of flow increases with a larger temperature difference.

While factors like the size of the heater, type of fuel used, and pressure in the boiler can play roles in the overall efficiency and operation of the heating system, they do not have the direct and immediate impact on heat transfer rates that the temperature differential does. The heater's size can influence capacity or overall efficiency, fuel type can affect combustion efficiency, and boiler pressure can impact boiling points, but it is the temperature difference that fundamentally drives the heat exchange process in the feedwater heater. This is why understanding and optimizing the temperature differential is crucial in enhancing the effectiveness of heat transfer in these systems.