Total heat transfer through pressure inlet

Naher · June 8, 2011, 01:40

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?
Please help me to understand this.
Thanks...

June 8, 2011, 01:40	Total heat transfer through pressure inlet	#1
Naher New Member Naher Join Date: Mar 2011 Posts: 7 Rep Power: 15	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

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
total pressure boundary problem ==> flow from outlet to inlet!!	mrshb4	OpenFOAM	0	November 20, 2010 12:41
pressure inlet & outlet. help ASAP Plz	engahmed	Main CFD Forum	0	June 13, 2010 15:34
Concentric tube heat exchanger (Air-Water)	Young	CFX	5	October 6, 2008 23:17
Total pressure exceeds inlet value	Tom	CFX	1	September 9, 2008 22:02
Setting dynamic pressure as the inlet BC	ruined	FLUENT	1	March 26, 2008 05:30

June 8, 2011, 17:31		#2
xrs333 Senior Member xrs333 Join Date: Aug 2010 Posts: 125 Rep Power: 16	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.

June 9, 2011, 00:45		#3
Naher New Member Naher Join Date: Mar 2011 Posts: 7 Rep Power: 15	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…

June 9, 2011, 10:24		#4
xrs333 Senior Member xrs333 Join Date: Aug 2010 Posts: 125 Rep Power: 16	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.

June 13, 2011, 10:22		#5
Naher New Member Naher Join Date: Mar 2011 Posts: 7 Rep Power: 15	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? Please help me to understand this. Thanks...