Pro/Forums - View Single Post - can we agree on the basis of "C" in C/W ?

bobo5195 · 10-23-2005, 11:59 AM

I'm sorry if this old news but:

The more I think about it the more for radiators I move towards effectiveness as a way to measure radiator performance. For a customer it has the obvious problem that it is not compatible with C/W used by blocks. However if you say to your average joe that your rad is 40% he can understand that easily. Its less abstract.

Effectiveness is also quite easily measurable for the DIY crowd. Taken from the paper I linked to above

E =( Mflow,water*Cp,water*(Twater,in-Twater,out) ) / (Mflow,air * Cp,air * (Twater,in – T air,in)

If I am reading my notes and the paper right it can be then said that

Q= E* Mflow,air * Cp,air *(Twater,in-Tair,in).

As an side note that gives, so C/W is still valid. Its just a different form

SD = 1/bill C/W = E * Cp,air.

And if I am reading this right. My uni notes use a different approach and are tests for different applications. I believe the same method works.

All of these with the exception of Cp air, Cp water and Mflow,air are easy for the hobbyist. Cp’s can be roughly calculate from standard measurements. Measurement of the water vapor content of air might be troublesome but its do able. Mass flow of air is also quite inferable with some work. Either way flow does not need to be characterized on both sides.

More advanced users can easily convert effectiveness into more useful data with a set fan and such. Fan type might be problematic as it influences cooling performance but numbers are roughly constant.

I have a dislike of LMTD for radiators as it doesn’t really work LMTD needs to be corrected for the radiator geometry and temperature amounts.

10-23-2005, 11:59 AM	#36
bobo5195 Cooling Savant Join Date: Aug 2005 Location: uk Posts: 400	I'm sorry if this old news but: The more I think about it the more for radiators I move towards effectiveness as a way to measure radiator performance. For a customer it has the obvious problem that it is not compatible with C/W used by blocks. However if you say to your average joe that your rad is 40% he can understand that easily. Its less abstract. Effectiveness is also quite easily measurable for the DIY crowd. Taken from the paper I linked to above E =( Mflow,waterCp,water(Twater,in-Twater,out) ) / (Mflow,air * Cp,air * (Twater,in – T air,in) If I am reading my notes and the paper right it can be then said that Q= E* Mflow,air * Cp,air (Twater,in-Tair,in). As an side note that gives, so C/W is still valid. Its just a different form SD = 1/bill C/W = E Cp,air. And if I am reading this right. My uni notes use a different approach and are tests for different applications. I believe the same method works. All of these with the exception of Cp air, Cp water and Mflow,air are easy for the hobbyist. Cp’s can be roughly calculate from standard measurements. Measurement of the water vapor content of air might be troublesome but its do able. Mass flow of air is also quite inferable with some work. Either way flow does not need to be characterized on both sides. More advanced users can easily convert effectiveness into more useful data with a set fan and such. Fan type might be problematic as it influences cooling performance but numbers are roughly constant. I have a dislike of LMTD for radiators as it doesn’t really work LMTD needs to be corrected for the radiator geometry and temperature amounts.