Answer to Question #227670 in Chemical Engineering for Lokika

Question

Comparing the flow arrangement in a heat exchnager, LMTD in parallel flow is (greater than/less than/equal to) LMTD in counter-flow?

Answer 1

less than

For counter flow HEX: the temperature difference between the hot & cold fluids is relatively constant across the HEX ( from inlet to outlet ) . which means that the rate of heat transfer is constant across the HEX pass.

For Parallel flow HEX: the temperature difference is high at the HEX inlet while it decrease gradually across the HEX pass. which mean the rate of heat transfer decrease through the HEX.