The Theory Behind Heat Exchanger

The Heat Exchanger Theory article provides you with an introduction to the fundamentals of a heat exchanger and will be useful to understand the concept of heat exchanger inspection. To describe this Theory, you may know we need to heat or to cool process fluids in industrial plants to facilitate process reactions.So we need to use heat exchangers either to reduce the temperature or increase the temperature.

This article provides you a simple explanation about heat exchangers working mechanisms and applications.Our process temperature needs to be at a certain value and to be stable.

For process requirements sometimes, we need to increase fluid temperature and sometimes reduce it. For temperature reducing purposes, an intermediate fluid such as cooling water, chilled water, a refrigerant and air are used.

Air-cooled heat exchangers are the same, but they use air as the intermediate fluid. In heat exchanger theory, we need to define Indirect Heat Transfer.

In most heat exchangers, two fluids are exchanging their heat without direct physical contact to avoid mixing. This is called indirect heat transfer. Cooling water temperature in a hot area is normally above 25 degrees centigrade, and it depends on the atmospheric and climate conditions. 

Sensible Heat:

Sensible heat is the amount of heat that a material can exchange without changing its phase. For example, water at 25 degrees centigrade enters the heat exchanger and absorbs the process fluid heat and exits from the heat exchanger at 35 degrees centigrade.

What is latent Heat?

The latent heat is the amount of heat transfer that a material exchanges during the change from the liquid phase to the vapor phase. Referring to the above definition we are using saturated steam in heat exchangers, the saturated steam is converted to liquid and the released heat will heat our process fluid. Indirect heat transfers are done in different heat exchangers such as coolers, heaters, reboilers and condensers.

In all of them, we are using an intermediate fluid for heat transfer. For the condenser, it is cooling water, and in the reboiler, it is steam. For cooler heat exchanger cooling water, refrigerants such as R-11, Propylene and propane are used. For heater heat exchangers, steam with different pressures are used. In heat exchanger theory for reducing energy consumption, sometimes process fluids are used for heat transfer themselves.