Thread: 100 sq mm Fluxdie worklog. View Single Post
10-11-2005, 11:05 AM   #55
Incoherent
Cooling Savant

Join Date: Sep 2003
Location: Vallentuna, Sweden
Posts: 410

1. @FLUX=393*0.00010*(@LOW4 + @TOP3*-1)/0.005077
2. @CU=(@LOW4 + @TOP3*-1)/5.077
3. @TI=((@CU*1.988 + @FB2)*-1 + (@TOP3 + @CU*-2.081))/@FLUX
4. @CW=(@FB2 + @CU*-2.017 + @WIN5*-1)/@FLUX + @TI*-1
5. @FLOW=60*(@FLUX/(4186*(@WOT6 +@WIN5*-1)))
6. @SYS=(@FB2 + @CU*-2.017 + @AIR1*-1)/@FLUX + @TI*-1

These are cut and pasted directly from my DAQ monitoring script. Translated into readable equations as follows:

1. Heat flux = k x A x (Tdie_low - Tdie_top)/L (heat in watts, Fourier, q=k.A.dT/L, k=393W/m°C, A=0.0001m^2, L=0.005077m, [nominally 5mm])

2. Cu dT = (Tdie_low - Tdie_top)/L (Temperature gradient in °C/mm)

3. TIM C/W = ((Tdie_top - Cu dT x 2.081) - (Cu dT x 1.988 + Tfluxblock))/Heat flux
or: (Extrapolated die top surface temp minus extrapolated FB lower surface temp, i.e Interface dT) divided by watts

4. C/W waterblock = (Tfluxblock - Cu dT* x 2.017 -Twater_in )/Heat flux -TIM C/W
or: (Extrapolated FB top surface temp minus Water in temp) divided by watts minusTIM i.e Air to WB base C/W

5. Flowrate (lpm) = 60 x (watts/(Cp x (Twater_out - Twater_in))

6. System Cw = (Extrapolated FB top surface temp minus Air temp) ...Not very useful, air is too variable

I realise I have named these very badly, particularly Die Top, sounds like die top surface, actually Die upper (top!?) sensor and Die low, = lower die sensor. I will rename them for future logs.
One thing I have noticed, different k here (393) than model (392). won't make any observable difference but shows I am making mistakes. Note the scripts inability to deal with the minus operation, I have to use + xx*-1.