Intercooler configuration

bigpete638

Hello,
I’m working on a high pressure high temperature hot water system. They have two intercoolers piped together with tees going to each on the pumps. They are still having overheating issues. Max temp is 350 degrees. They have 1/2” cold water supply running through the intercoolers to cool the pumps. Should we pipe through one intercooler than directly to the next before returning to the pump or have them go through both at same time? Any and all information is greatly appreciated. The high temperature is being used to create steam so I’m putting it under that category. Hope that is ok.

Jamie Hall

Could you post a sketch of the piping and pumps? As a sort of general thing, you want a counterflow arrangement -- that is, the cooling water inlet at the cooled medium outlet. This will allow you to still have a decent temperature difference across the heat exchangers at the outlet of the cooled medium, and provide (usually) better overall cooling performance.

bigpete638

I’ll try to post a sketch later. Thank you!

bigpete638

bigpete638

This is the setup currently. They installed one aluminum bodied intercooler which will more than likely warp.

bigpete638

Would it be better to pipe into one and it’s return pipes into the second as if working in stages before returning to the pump?

Jamie Hall

bigpete638 said:

Would it be better to pipe into one and it’s return pipes into the second as if working in stages before returning to the pump?

That's kind of what I'm thinking -- with the cold water coolant going to the second intercooler (the one feeding presumably cool cooling medium back to the pump) and the cooling water output of that going to the first intercooler -- the one taking the cooling medium output from the pump. So you are getting counterflow -- cooling water going one way, pump cooling medium going in the opposite direction.

bigpete638

Great! Thank you for the input!

mikeg2015

Running them in series however might reduce your total flow and total heat removal. 2nd heat exchanger will have less capacity since the heat transfer fluid (tower water?) will be the same either way. The capacity of a heat exchanger is proportional to the delta T of the fluids being cooled.

I think you need ot look at flow rates, pump sizes and consider going with a larger heat exchanger.

bigpete638

I’ll look into that tomorrow. That’s a good idea. Thank you.

bigpete638

What would be the ideal temperature of medium to cool off a pump coming from the intercooler? The water is going to the intercooler at 320 degrees F and returning to the pump at 250.

Jamie Hall

bigpete638 said:

What would be the ideal temperature of medium to cool off a pump coming from the intercooler? The water is going to the intercooler at 320 degrees F and returning to the pump at 250.

That's really an impossible question -- sorry. There are too many variables. As @mikeg2015 noted, the heat transfer capacity of a heat exchanger ("intercooler" in this discussion) depends on two factors: the design of the heat exchanger, obviously, and the difference in temperature between the two flows as they pass through the heat exchanger. Clearly, if your cooling medium flow is at a lower temperature, you can transfer more heat, which basically means that you can get away with a lower flow rate for the cooling medium (obviously, within limits!). (It should be noted in passing that there may be reasons related to thermal physical stress on the maximum delta T). Other questions which need to be posed and answered include, for example, can you do anything useful with the heat in the exiting cooling flow? What temperature would that require? Are there limits on the maximum or minimum temperatures of the cooling flow (for instance, water at atmospheric pressure can't go below 32 F or above 212 F).

In your situation, given no use for the heat in the exiting flow and the likely availability of single pass water and no limits on the outlet temperature, I might start penciling with a counterflow design, starting with incoming water at about 80 F, giving me a delta T at that point of 170 F, and going for a flow rate great enough to limit the outlet temperature of the coolant to 180 F -- giving me a delta T at that end of the system of 140 F. But... suppose I want that outlet water for domestic hot water? OK -- change the flow rate to limit to 140 at the outlet. Suppose I want a closed system, and dump the heat to a radiator? Suppose...

Too dang many variables...

mikeg2015

Some heat exchangers have limits in delta T due to thermal shock. Boilers included. Brazed plate and coaxial I don’t think care, but some tube and shell’s heat exchangers may.

Weakly née to pull up mfg specs. Too much flow and too little flow can be an issue too.

bigpete638

Thanks again for all the information. This site is really great.