2 replies to this topic

[Eric L]

So I am supposed to cool water from a tank (open to the atmosphere) to a process 200 feet past the HE that's at 10 psig.. I need to size the Heat Exchanger and a pump to make this happen. My question is how do I go about finding the maximum allowable pressure drop across the exchanger?

[ankur2061]

Eric L,

 

You don't find or calculate the maximum allowable pressure drop across your exchanger. You specify this value and design your exchanger such that the actual pressure drop does not exceed the maximum allowable pressure drop.

 

The methodology of specifying this pressure drop is simply to ensure that with all the system dynamic losses including the maximum allowable pressure drop across the heat exchanger you have the desired pressure at the terminal or destination end of your flow. Also note that more the pressure drop you allow the more energy is spent in moving the fluid from the source end to the destination end. The flip side for heat exchangers is that if the pressure drop is too low, there isn't enough turbulence to provide effective heat transfer in a heat exchanger. Another negative aspect of too low a pressure drop is that it can cause fouling due to low velocities at low pressure drops. Hence some amount of trial and error gets involved in specifying the maximum allowable pressure drop, wherein the desired heat transfer is not sacrificed as well as the energy consumed in transporting the fluid from the source and destination is not too excessive.

 

Since you have not furnished more details such as what quantity are you pumping, what is the cooling medium in your exchanger, what is the destination pressure this is the best approximate answer that can be furnished.

 

Regards,

Ankur.

[Eric L]

Ankur,

 

Appreciate the quick response!

 

Thanks,

Eric