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Permissable approach temperature limit PCHE for nucleate boiling

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frogcurry

Chemical
Feb 17, 2005
23
I have another obscure enquiry:

I have a natural gas compressor with a PCHE discharge cooler, which in some situations may for a while be called on to pressurise 45 barg gas to 160 barg. I have found that discharge temperatures for this operation are close to the cooling medium boiling point in the discharge due to the high head.

Cooling medium (mix of 20% MEG and water) boils at 156 Celcius, and can't be increased (its already at the maximum pressure it can be raised to now). Compressed gas discharge temp is 152 C. My concern is that if the gas inlet cooling is impaired or there is an upset then discharge temp may rise > 156C and so begin boiling cooling medium.

So, my question is this:
Does anyone know of a standard, or have experience, of any sort of guideline temperature margin that should be aimed for? And although I know that PCHEs are susceptible to hot spots, how much so can I reasonably expect this - how much danger/ possibility is there that the cooling medium will reach the gas inlet temp?

Fluid flow is cross current, and normal discharge temp of cooling medium (measured downstream of the cooler discharge) is approx 50 Celcius.

Thanks in advance for any help rendered.

 
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hello,

there are many cases where cooling water are used to cool fluids with very high inlet temperature (over the boiling point of the cooling water), so the flow of your cooling medium should be calculated so you dont approach the boiling point for the worst case you are describing, i would take ~20 deg C approach.

regards,
roker
 
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