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increased flowrate decreased in heat rejection?

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Old   April 7, 2010, 21:03
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  #21
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Hi guys, how are you?

This time, i used the model shown in 'pipeTH3.jpg', and only used water to perform CHT. No other temperature BC or convection BC applied.

with 3kW heat source, using the heat taken away expression, water is calculated to take away 3315.93W.

so, i think i'm still facing the problem of clarification of the results. RMS residuals are below 1e-5, and Domain imbalances are <1%. why is the heat taken away by water still larger than the heat source applied please?
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Old   April 7, 2010, 23:34
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Send me Your .def-file, I'll try to run it and see what's wrong. dvolkind@hotmail.com
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Old   April 8, 2010, 07:14
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There's one other enquiry:

taking my 1st example in CHT analysis. How can i evaluate the cooling efficiency of my model please?
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Old   April 12, 2010, 09:34
Default fluid flow cylindrically=rotating fluid?
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Hi guys,

in this attached picture, cfxOutput.jpg, a simple model that represents the eventual complex geometry. It is a cylindrical model that can accommodate an electrical machine in the inner space. In this cylindrical housing, there is an internal cooling channel with ribs to increase the effective surface area for heat convection. The electrical machine in the housing will have losses. Losses are applied to the model as heat flux. I am trying to obtain a design that is to use water that flows in the channel to take away all the losses. Outer surfaces of the cylindrical housing is air.

Does this fluid that flows in a cylindrical path considered a rotating fluid please?
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Old   April 12, 2010, 13:08
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No it's not a rotating fluid. Why do you ask?

By the way, I'll try to make your model work soon. Had no time since your last letter. You also asked about how you should estimate cooling efficiency: in your case I would measure the ratio of electric power needed to pump the cooling water (W) and heat power (kW). For example, 100 W/kW, not 10 %. That's what we usually do in Russia)
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