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Long Haired Git · 02-18-2005, 12:37 AM

Uggg, still can't get it.
Yes, I could use pressure drop, but I want my spreadsheet to do the calcs as then I don't need the app, and I can also include my own stuff.
Cross referencing the application (not reverse engineering) I have all the same numbers for dyn viscosity, density and I have triple-checked my conversion from Pascal to mH20.
Still not right.
The app takes friction into consideration, whereas my spreadsheet doesn't, but the spreadsheet is returning numbers 1/10th mine.

I mean, the equation is:
delta Pressure = ( Density/2 ) * ( v2^2 - v1^2 )
Me and the app agree density = 998.2 kg/m3
Me and the app agree dyn viscosity = 0.001002
Me and the app agree v2 = say, 9m/s

I thus get 40427.1 pascals.
Conversion factor is 0.000102 mH20 per Pascal
Hence 4.12 m of head.

The application (with zero roughness) gets 0.05 "bar", which converts to 0.5m of head using the apps own calculator. Obviously I'm wrong as none of these blocks could work if they were as restrictive as my calcs, but I am blind to my mistake....

Uggg, where am I going wrong?

02-18-2005, 12:37 AM	#18
Long Haired Git Cooling Savant Join Date: Jan 2003 Location: Sydney, Oz Posts: 336	Uggg, still can't get it. Yes, I could use pressure drop, but I want my spreadsheet to do the calcs as then I don't need the app, and I can also include my own stuff. Cross referencing the application (not reverse engineering) I have all the same numbers for dyn viscosity, density and I have triple-checked my conversion from Pascal to mH20. Still not right. The app takes friction into consideration, whereas my spreadsheet doesn't, but the spreadsheet is returning numbers 1/10th mine. I mean, the equation is: delta Pressure = ( Density/2 ) * ( v2^2 - v1^2 ) Me and the app agree density = 998.2 kg/m3 Me and the app agree dyn viscosity = 0.001002 Me and the app agree v2 = say, 9m/s I thus get 40427.1 pascals. Conversion factor is 0.000102 mH20 per Pascal Hence 4.12 m of head. The application (with zero roughness) gets 0.05 "bar", which converts to 0.5m of head using the apps own calculator. Obviously I'm wrong as none of these blocks could work if they were as restrictive as my calcs, but I am blind to my mistake.... Uggg, where am I going wrong? __________________ Long Haired Git "Securing an environment of Windows platforms from abuse - external or internal - is akin to trying to install sprinklers in a fireworks factory where smoking on the job is permitted." (Prof. Gene Spafford) My Rig, in all its glory, can be seen best here AMD XP1600 @ 1530 Mhz \| Soyo Dragon + \| 256 Mb PC2700 DDRAM \| 2 x 40 Gb 7200rpm in Raid-0 \| Maze 2, eheim 1250, dual heater cores! \| Full specifications (PCDB)