Parallel flow and counterflow heat exchangers are often compared. Can you remove (transfer) the same amount of heat from both heat exchangers? If not, explain why not. If so, explain how.
Why does the cold fluid temperature decrease in a counter flow where as, in a parallel flow, it increases in heat exchangers? - Quora
Countercurrent exchange - Wikipedia
What is Double Pipe Heat Exchanger - Definition
How to decide whether the given shell and tube heat exchanger is a counter flow or parallel flow - Quora