Theory 87/Energy Limits/Heat exchangers
Exchangers Pay for Approach
The claim
Heat exchanger area is set by the reciprocal of the approach temperature, so halving the approach doubles the area and roughly doubles the cost.
01Mechanism
Heat transfer is proportional to the temperature difference; a smaller difference requires proportionally more area for the same duty.
02Prediction
Area should scale inversely with approach.
03Refutation
Area independent of approach would remove the limit.