Why is it a Heat Exchanger with a 20 F delta T (inlet=200F outlet=180F) is more expensive than a Heat Exchanger with a 40 F delta T (inlet = 240F outlet = 200F)?
Wait, no... the greater the temperature change (assuming all other things are equal), the more exchanger you'll need, and the more you'll pay. [edit] Sorry kids... looks like a few people here missed Heat Transfer class. The greater the temperature change, the GREATER the surface area required, and the more expensive the exchanger. This is 101 stuff, guys. [edit] Imagine a heat exchanger that had a delta-T of zero... that's no heat exchanger (free).... now imagine a heat exchanger of infinite delta-T.... that's going to be a heat exchanger of infinite duty, and infinite surface area!!!
The 20delta T heat exhanger will need to be much bigger that a delta 40 heat exchanger in the case they are required to remove the same amount of heat in a given time.It's something like heating a meal at boiling temperature (big delta) or at 80C(smaller delta,where the delta is the difference between the food to be heated and the heating medium.
Q= (m) (c) (delta t) Q is the heat m is the mass c is the specific heat..(depend on the material)
