Cross flow heat exchangers are used in many different applications. Mixed and unmixed cross flow exchangers can be named as the types of cross flow heat exchangers based on the fins used in the system. The other names for them are finned and unfinned. The figure below shows these types.
Mixed Cross Flow Heat Exchangers
In this type, the fluid passes over the pipes in the shell side, and the flow is perpendicular to the pipes. The heat exchanger does not have any fins, as is shown in the figure. We can have turbulent flow in this type, and the pressure drop is less than the other one. Turbulent flow can significantly increase the heat transfer rate.
Unmixed Cross Flow Heat Exchangers
In the unmixed cross flow heat exchangers, we have fins around the pipes or separate channels for the flow to pass over the pipes. Using fins can increase the heat transfer due to the increase in the effective surface area of heat transfer. On the contrary, we have a larger pressure drop in the system. Also, the weight and the cost of these types increase because of adding fins to the exchanger.