Is the cross flow heat exchanger co-current or counter-current?

Cross-flow heat exchanger is neither a downstream heat exchanger nor a counter-flow heat exchanger. It is a third flow mode, characterized by the flow directions of the two fluids being perpendicular to each other. The following is a detailed description:

1. ​​Characteristics of downstream and upstream flow​​

• ​​Go with the flow​: Two fluids flow in parallel in the same direction (e.g. both flow from left to right).
  • Features: large inlet temperature difference, small outlet temperature difference, relatively low heat transfer efficiency, but simple structure.
• ​​Backflow​: Two fluids flow in parallel in opposite directions (e.g. one from left to right and the other from right to left).
  • Features: Large outlet temperature difference, higher heat transfer efficiency, and is a more commonly used design in industry.

2. ​​The uniqueness of cross-flow heat exchangers​​

• Flow direction: The flow directions of the two fluids are perpendicular to each other (for example, one flows horizontally and the other flows vertically).
• Typical applications: compact equipment such as automotive radiators, air conditioning condensers, electronic equipment cooling, etc.
• Advantages: Compact structure, high heat transfer efficiency, suitable for high heat load scenarios.

3. ​Why is cross-flow independent classification?​

• The definitions of co-current and counter-current are based on the directional relationship of the fluids flowing in parallel, while cross-flow flows in perpendicular directions and cannot be classified as either.
• In heat transfer, cross flow is usually analyzed as a separate object, and its heat transfer calculation model (such as ε-NTU method) is also different from that of co-current/countercurrent flow.

Summarize:

Cross-flow heat exchanger is an independent flow type, neither co-current nor counter-current. Its design maximizes heat transfer efficiency through vertical flow direction while reducing space occupation, so it is widely used in engineering.