What method yields the best heat exchange efficiency for heat exchangers?
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Why is counterflow commonly used in heat exchangers?
This question needs to be considered from multiple perspectives; the advantage of counterflow heat exchange is relative to crossflow, as it allows for a longer contact time and a larger temperature difference
What about the cross-flow? What are the heat exchange effects of cross-flow, co-current, and counter-current flow respectively?
Counterflow is commonly used in heat exchangers because it results in the greatest logarithmic temperature difference for heat transfer, thereby allowing the heat exchange area to be minimized. However, in some cases the temperature difference should not be too large; in such situations, traveling with the current can be an option. The flow direction is generally determined by the design of the equipment; for example, in a economizer, flow is from left to right on one side, and from top to bottom on the other side
In the same situation, counterflow > co-flow. For cross-flow, it depends on the specific circumstances when comparing it with co-flow and counterflow.
The local temperature difference in the co-current flow is greater than that in the counter-current flow; the counter-current flow has a larger average temperature difference, resulting in better heat exchange efficiency. Cross-flow prevents excessive local temperature differences.