Large heat exchangers are used in downstream petrochemical processing, for example to recover heat from a fluid that would either be cooled for its next process, or would release the heat to atmosphere as waste energy.
This heat can be used to pre-heat another fluid as part of its own process. Such an application would be the pre-heating of hydrocarbon feed stock in another process.
A variation on the shell and tube exchanger is its use as a condenser at the outlet of a steam turbine. In this case steam at near vacuum in the pressure vessel flows over cooling water in the tube bank to condense and be returned to the process.
Shell and Tube
Shell and Tube Heat Exchangers are the most commonly used method of transferring heat between two fluids at different temperatures in a pressurised flow. A large pressure vessel carrying one fluid contains a bundle of tubes carrying the other fluid. As they flow past each other, the thermal transfer occurs in a controlled way
When one of the fluids is at atmospheric pressure, and often using air as that fluid, heat transfer occurs across a large surface area with the unpressurised fluid flowing over it.
Extended surface exchangers are often used in dryers where air is heated using steam in order to dry a wet product in a another downstream process. Ambient air is filtered and then heated through our system.
An alternative in refining industries is to accelerate cooling of hot fluids to prepare them for the next stage of their process. Hot air can be vented to atmosphere without any environmental impact.