Heat Exhchanger Selection (what is kw/C)

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Discussion Overview

The discussion revolves around the selection of a suitable heat exchanger for cooling water from 70°C to 25°C at a flow rate of 28 liters per minute. Participants explore the concept of "kw/C" as a performance specification relevant to this application.

Discussion Character

  • Technical explanation
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant seeks assistance in understanding how to apply the "kw/C" specification to their heat exchanger selection problem.
  • Another participant explains that "kw/C" indicates the power a heatsink can remove per degree Celsius of temperature rise, noting that this measure is only accurate within certain energy input ranges.
  • A further contribution attempts to calculate the required "kw/C" by determining the energy to be extracted to cool the water and suggests that a radiator with a cooling effect of 2.04 kw/C is needed at the specified flow rate.
  • One participant questions the flow rate, suggesting a need for clarification on the volume of water to be cooled.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the application of "kw/C" and its implications for heat exchanger selection. There is no consensus on the calculations or the specifics of the heat exchanger requirements.

Contextual Notes

Some assumptions regarding the accuracy of "kw/C" under different energy inputs remain unresolved, and the calculations presented depend on specific definitions of energy extraction and flow rates.

Su Solberg
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Hello, everyone.

I have a problem in finding a suitable heat exchanger for cooling coils.
I would like to cool down 28 lier/min; from 70 Celsius to at least 25 Celsius.

I wonder how to fit "kw/C"(performance spec.) to my case so that i can find a suitable heat exchanger.

Thanks for your help.
 
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kw/C is a measure of how much power (kw) the heatsink can remove for each degree C temperature it rises.
Once the heat sink reaches the temperature of the incoming hot fluid it is obviously not going to remove any more heat.

You can work out the amount of energy to be extracted each second to cool 28/60 litres of water by 45 C and then from the kw/c work out how much this will heat the heatsink.

Note - this is just an approximation - the kw/c is only correct for a certain amount of power. At very high or very low energy inputs it might not be accurate..
 
mgb_phys said:
kw/C is a measure of how much power (kw) the heatsink can remove for each degree C temperature it rises.
Once the heat sink reaches the temperature of the incoming hot fluid it is obviously not going to remove any more heat.

You can work out the amount of energy to be extracted each second to cool 28/60 litres of water by 45 C and then from the kw/c work out how much this will heat the heatsink.

Note - this is just an approximation - the kw/c is only correct for a certain amount of power. At very high or very low energy inputs it might not be accurate..

Thanks for your reply.

To confirm your meaning, is that mean suppose the water will reject heat 92kw/s (from 70->25;Q=M*Cp*(T1-T2) ) then the kw/C required is 92kw/45C=2.04kw/c.

That's mean I have to find a radiator that can achieve 2.04kw/c cooling effect at 28l/min?

Thanks for your help.
 
LEt see, you need 60 liters per minute of Water to drop from 70 down to 25 C?
 

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