6 replies to this topic

[panoska]

Hello everyone,

 

Is it acceptable to have crossover temperature in a countercurrent heat exchanger?

 

Or we need to change the design of the heat exchanger?

 

 

 

[Pilesar]

The cold side outlet temperature can be above the hot side outlet temperature in a countercurrent heat exchanger. Is that what you mean by a crossover temperature? When designing, choose the most economical design that meets all the requirements.

[breizh]

Hi,

Consider this link:

https://www.cheresou...eat-exchangers/

 

Breizh

[panoska]

Pilezar, this is what I mean.
Breizh, I read the discussion. But, I do not agree that temperature cross is desirable.

[breizh]

hi,

Nobody says it's desirable, just a matter of fact and cost.

https://www.pdhonlin...m371content.pdf

EDIT :

Others posts on the same subject:

https://www.cheresou...eat-exchangers/

in particular the last comment from srfish , the "god" of Heat transfer with a lot of publications

good luck

Breizh

[Falah]

Hello everyone,

Is it acceptable to have crossover temperature in a countercurrent heat exchanger?

Or we need to change the design of the heat exchanger?

Do you mean temperature cross?

[_1angelia23]

Hello everyone,

Is it acceptable to have crossover temperature in a countercurrent heat exchanger?

Or we need to change the design of the heat exchanger?

The temperature cross is undesirable, particularly for shell and tube exchangers, because the tube surface area is not utilized effectively and hence there is wastage of capital cost. If outlet temperatures form a temperature cross in a multiple tube pass heat exchanger, a lower than desirable LMTD correction factor will occur. A simple way to avoid this is to use more exchanger shells in series. Other engineers suggest that a small temperature cross may be acceptable and may provide a less expensive design than the more complex alternatives. For a E1–2 heat exchanger, the temperature cross occurs around a relatively narrow range of F value about 0.78–0.82. Lower values of F may be taken as an indication that temperature cross will occur.