increased flowrate decreased in heat rejection?

mactech001 · April 7, 2010, 21:03

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?

dvolkind · April 7, 2010, 23:34

Send me Your .def-file, I'll try to run it and see what's wrong. dvolkind@hotmail.com

mactech001 · April 8, 2010, 07:14

There's one other enquiry:

taking my 1st example in CHT analysis. How can i evaluate the cooling efficiency of my model please?

mactech001 · April 12, 2010, 09:34

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?

dvolkind · April 12, 2010, 13:08

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)

April 7, 2010, 21:03		#21
mactech001 Senior Member Join Date: Nov 2009 Posts: 125 Rep Power: 16	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? __________________ Thank you for your kind attention. Kind regards, mactech001 Currently using: ANSYS v13

April 8, 2010, 07:14		#23
mactech001 Senior Member Join Date: Nov 2009 Posts: 125 Rep Power: 16	There's one other enquiry: taking my 1st example in CHT analysis. How can i evaluate the cooling efficiency of my model please? __________________ Thank you for your kind attention. Kind regards, mactech001 Currently using: ANSYS v13

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April 7, 2010, 23:34		#22
dvolkind Member Dmitry Volkind Join Date: Jan 2010 Location: Ekaterinburg, Russia Posts: 64 Rep Power: 16	Send me Your .def-file, I'll try to run it and see what's wrong. dvolkind@hotmail.com

April 12, 2010, 13:08		#25
dvolkind Member Dmitry Volkind Join Date: Jan 2010 Location: Ekaterinburg, Russia Posts: 64 Rep Power: 16	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)