Quantifying Thermoelectric System C/W

koslov · 04-26-2003, 03:45 AM

I have been playing around with the Kryotherm app, just experimenting and seeing which factors can improve peltier performance. I have been using totally arbitrary(ly low) values, and I was wondering what are some rough values I can use to get reasonable results. There are two params for Kryotherm °C/W: hotside and coldside. Maybe you can help me come up with some fairly accurate numbers.

The way I see it is there are 7 gradients above the CPU alone:

1. TIM gradient 1: The die-to-coldplate resistance (100mm² area to >1600m² area)

2. Coldplate gradient: Resistance going from one side of cold plate to other

3. TIM gradient 2: From coldplate through goop to TEC

4. TEC gradient: ??? Who knows, let Kryotherm do the work

5. TIM gradient 3: From TEC through goop to wb (same as 2?)

6. Baseplate gradient: From bottom to 'furniture' (hehe, did you coin that yourself BillA?)

7. WB to coolant: What everyone is so focused on improving

On top of that, you can add radiator resistance too.

Coldside would include 1 - 3, hotside, 5 - 7 plus radiator.

On an OCAU thread, Bill suggested 0.04 for a good TIM joint (on a CPU). This would correspond to my TIM gradient 1.

Can we use .04, and just multiply by the ratio of the areas of the CPU to the TEC to get TIM gradient 3 and 5? So for a 40 x 40mm pelt, 0.003?

Do we know 2? I guess it depends on base thickness.

6 and 7 are specific to the wb, but can we at least estimate a range of values?

I am just looking for some rough values, so maybe my totals for hotside and coldside are +/- .05, but that would at least give pelt users a good idea of temps to expect when using Kryotherm.

Les · 04-26-2003, 04:13 AM

A repost*:- "Peltier Calculations - Am I mistaken?
Posted elsewhere - http://forums.procooling.com/vbb/sho...5&pagenumber=1

"I am not actively engaged in playing with Peltiers at the moment.
However my currently favored Kryotherm parameters may interest :-
Rc=0.19 - 0.26 (for 40x40x6 mm Cold plate with a 10x10mm heatsource)
Based on:
1) C/W(TIM,Die/coldplate) ~0.1 - from Bill Adams work(e.g http://www.overclockers.com/articles654/index02.asp ) ,making an allowance of 0.05c/w for die thermocouple offset.
2) C/W(Coldplate) ~ 0.09 to ~ 0.16 -- from Waterloo calculations using,possibly mistakenly, an h=10,000 - 100,000W/m*m*c as corresponding to the conditions for a 172W Pelt cooled by a wb with a C/W=0.00625 - 0.0625(cooling a 40x40mm heat source).

Ri=1
Based on my current attemps to cross-correlate Bill Adams data with CPU(Diode)/"Radiate calculated Watts"

All are very iffy and only the thoughts of a dilettante." "

* http://forum.oc-forums.com/vb/showth...hreadid=150430

EDIT: Corrected links.

koslov · 04-26-2003, 04:15 AM

Ah, thanks very much, this is exactly what I was looking for.

04-26-2003, 03:45 AM	#1
koslov Cooling Savant Join Date: Jul 2002 Location: Posts: 264	Quantifying Thermoelectric System C/W I have been playing around with the Kryotherm app, just experimenting and seeing which factors can improve peltier performance. I have been using totally arbitrary(ly low) values, and I was wondering what are some rough values I can use to get reasonable results. There are two params for Kryotherm °C/W: hotside and coldside. Maybe you can help me come up with some fairly accurate numbers. The way I see it is there are 7 gradients above the CPU alone: 1. TIM gradient 1: The die-to-coldplate resistance (100mm² area to >1600m² area) 2. Coldplate gradient: Resistance going from one side of cold plate to other 3. TIM gradient 2: From coldplate through goop to TEC 4. TEC gradient: ??? Who knows, let Kryotherm do the work 5. TIM gradient 3: From TEC through goop to wb (same as 2?) 6. Baseplate gradient: From bottom to 'furniture' (hehe, did you coin that yourself BillA?) 7. WB to coolant: What everyone is so focused on improving On top of that, you can add radiator resistance too. Coldside would include 1 - 3, hotside, 5 - 7 plus radiator. On an OCAU thread, Bill suggested 0.04 for a good TIM joint (on a CPU). This would correspond to my TIM gradient 1. Can we use .04, and just multiply by the ratio of the areas of the CPU to the TEC to get TIM gradient 3 and 5? So for a 40 x 40mm pelt, 0.003? Do we know 2? I guess it depends on base thickness. 6 and 7 are specific to the wb, but can we at least estimate a range of values? I am just looking for some rough values, so maybe my totals for hotside and coldside are +/- .05, but that would at least give pelt users a good idea of temps to expect when using Kryotherm.

04-26-2003, 04:13 AM	#2
Les Cooling Savant Join Date: Oct 2001 Location: Wigan UK Posts: 929	A repost:- "Peltier Calculations - Am I mistaken? Posted elsewhere - http://forums.procooling.com/vbb/sho...5&pagenumber=1 "I am not actively engaged in playing with Peltiers at the moment. However my currently favored Kryotherm parameters may interest :- Rc=0.19 - 0.26 (for 40x40x6 mm Cold plate with a 10x10mm heatsource) Based on: 1) C/W(TIM,Die/coldplate) ~0.1 - from Bill Adams work(e.g http://www.overclockers.com/articles654/index02.asp ) ,making an allowance of 0.05c/w for die thermocouple offset. 2) C/W(Coldplate) ~ 0.09 to ~ 0.16 -- from Waterloo calculations using,possibly mistakenly, an h=10,000 - 100,000W/mmc as corresponding to the conditions for a 172W Pelt cooled by a wb with a C/W=0.00625 - 0.0625(cooling a 40x40mm heat source). Ri=1 Based on my current attemps to cross-correlate Bill Adams data with CPU(Diode)/"Radiate calculated Watts" All are very iffy and only the thoughts of a dilettante." " http://forum.oc-forums.com/vb/showth...hreadid=150430 EDIT: Corrected links. Last edited by Les; 04-26-2003 at 04:43 AM.

04-26-2003, 04:15 AM	#3
koslov Cooling Savant Join Date: Jul 2002 Location: Posts: 264	Ah, thanks very much, this is exactly what I was looking for.

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