For heat exchangers, is it better for the hot and cold fluids to flow counterflow or co-current? Why?
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For heat exchangers, is it better for the hot and cold fluids to flow counterflow or co-current? Why?
The temperature difference at the end of heat exchange in counterflow is large, resulting in a high driving force for heat exchange.
Of course, counterflow is better; with counterflow, the temperature difference at the end of heat exchange is larger, resulting in a greater driving force for heat exchange.
The heat transfer temperature difference is large in counterflow, which is why counterflow is generally used in heat exchangers. However, if there are requirements regarding the outlet temperature – for example, it must not be higher or lower than a certain value after heating or cooling – then co-current flow should be used.
In practical applications, co-current flow is rarely seen. After all, it reduces the heat exchange area in the counterflow direction. There are requirements regarding the outlet temperature; counterflow can also be adjusted, while co-flow is relatively easier. There is a situation in which co-current flow is advantageous: when dealing with high-viscosity fluids, co-current flow allows for rapid heating, which reduces viscosity and increases the heat transfer coefficient.
Accumulate points; just do the calculation and you’ll know the answer