Question

which materials are best for heat exchangers.
I want to know everything that heat exchanger depends on like reynolds no., thermal conductivity, friction factor, etc.,
please explain everything of dependency of heat exchanger.

Answer 1

I hope this will help you out. Please do give a thumbs up.


The best material for heat exchangers --  The best material for heat exchangers tubes is the one with high thermal conductivity. So that Heat from the hot fluid to the cold fluid can easily be transferred. Aluminum and copper are the preferred ones as they have high thermal conductivity as well as they are corrosion resistant also.


Factors on which heat exchanger depends --

Net heat transfer between hot and cold fluid in the heat exchanger

Q = U *A *LMTD

LMTD = logarithmic mean temperature difference
A = Surface area
U = Overall heat transfer coefficient

So it is clear that heat transfer depends upon these three terms. Since area and logarithmic mean temperature difference depends upon a fluid and our consideration. But the overall heat transfer coefficient depends upon many factors. Those factors
are -

Fouling factor - Fouling factor is the factor that is taken into consideration because of the thermal resistance offered by any chemical scaling or deposits that are formed on the heat transfer surfaces on both and a hot side. Overall heat transfer coefficient is inversely proportional to the inside and outside fouling factor.

Friction factor - The friction factor is taken into consideration as a resistance to the flow of fluid inside a tube. The overall heat transfer coefficient is inversely proportional to the resistance to the flow of fluid inside a tube.

Thermal conductivity - Overall heat transfer coefficient is inversely proportional to the resistance to heat flow through the walls of the tube.

Reynolds number -  As Nusselt number   
h depends upon Reynolds's number and the overall heat transfer coefficient is directly proportional to the heat transfer coefficient (h).