Please tell me about both parallel flow and counter flow .
Concentric tube heat exchangers are the simplest type of heat exchanger. Essentially its a tube inside of a tube (or outer jacket if you like). In one part a hot fluid flows and transfers its heat through the wall of a metal (usually copper/stainless steel) to another cold fluid. Parallel flow and counter flow refer to the fluid flow directions relative to each other. If both inlets are on the same side and flow in the same direction then this is known as parallel flow. The opposite is known as counter flow. Both flows are used common but the most common configuration is counter flow as it allows the most temperature differental possible as you are presumably heating or cooling a liquid. You would use parallel flow if you want to generate a common temperature between the two fluids.
