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-   -   Total heat transfer through pressure inlet (http://www.cfd-online.com/Forums/fluent/89230-total-heat-transfer-through-pressure-inlet.html)

 Naher June 8, 2011 01:40

Total heat transfer through pressure inlet

Dear all,
I am simulating Natural convection for a domain which has pressure inlet, pressure outlet and the wall has constant heat flux. At pressure inlet the total temperature is 300 K and the reference temperature is also 300 K. However, at the end of the simulation, there is a value for total heat transfer through inlet. But the temperature is 300 K as expected. Can anybody please explain me, why there is a heat transfer through the inlet although there is no temperature difference?
Thanks,
Naher

 xrs333 June 8, 2011 17:31

Hi, Naher,
The temperature gradient is not zero at inlet, although you specify a constant temperature for the inlet. In another word, not no temperature difference there.

 Naher June 9, 2011 00:45

Dear xrs333,
Thank you very much for your reply. Can you please explain it little bit more? I am not clear. My inlet temperature and reference temperature are same then how come there is a temperature difference.
I look forward to hear from you…

 xrs333 June 9, 2011 10:24

Hi, Naher,
The temperature gradient, which is the cause of energy diffusion at inlet, is not determined by the difference of reference temperature and imposed inlet temperature. The reference value is just for use in calculating non-dimensional number, such as Nusselt number.

 Naher June 13, 2011 10:22

Dear xrs333,
Thank you very much for your help.
I have another question. The Area-weighted average enthalpy at temperature 300 K is 1861.89 j/kg. I got this value for enthalpy at inlets, wall and even at interior, where ever the temperature is 300 K. But I do not understand how did fluent calculate this enthalpy?