Natural convection regime in a small cavity

AntonioDesah · April 29, 2020, 11:21

Hi all.

Trying to study the behavior of a fridge in natural convection regime. I have simplified a lot the problem, to understand if my model works but it seems not to. The cavity is very small 60cmx100cm and the flow is steady. I set up a density based model, activated the energy equation and set up the gravity along the y axes with negative value. I have used a laminar model and a k-omega standard but the results are very poor, although my mesh quality is correct. I am pretty sure that I am missing something in the B.C or reference value. The rear vertical is set with 277 K and zero heat flux. The other three walls are at the same temperature of 300K and thermal insulated as well. I would expect a contour of temperature as evidence of natural convection motion but none of this happened. The model has converged on 10E-5 values of the residuals after 10k iterations. Any help? Thanks in advance for any reply.

[IMG] https://ibb.co/Fz6NVLV [/IMG] mesh

[IMG] https://ibb.co/gyLbw6y [/IMG] Velocity contours for K-omega standard

[IMG] https://ibb.co/Pg5Tp2G [/IMG] Static temperature

duri · April 29, 2020, 14:45

Density based approach are good for very low speed flows better use pressure based solver with density as function of temperature (not ideal gas).

April 29, 2020, 11:21	Natural convection regime in a small cavity	#1
AntonioDesah Member Antonio Join Date: Nov 2016 Posts: 36 Rep Power: 10	Hi all. Trying to study the behavior of a fridge in natural convection regime. I have simplified a lot the problem, to understand if my model works but it seems not to. The cavity is very small 60cmx100cm and the flow is steady. I set up a density based model, activated the energy equation and set up the gravity along the y axes with negative value. I have used a laminar model and a k-omega standard but the results are very poor, although my mesh quality is correct. I am pretty sure that I am missing something in the B.C or reference value. The rear vertical is set with 277 K and zero heat flux. The other three walls are at the same temperature of 300K and thermal insulated as well. I would expect a contour of temperature as evidence of natural convection motion but none of this happened. The model has converged on 10E-5 values of the residuals after 10k iterations. Any help? Thanks in advance for any reply. [IMG] https://ibb.co/Fz6NVLV [/IMG] mesh [IMG] https://ibb.co/gyLbw6y [/IMG] Velocity contours for K-omega standard [IMG] https://ibb.co/Pg5Tp2G [/IMG] Static temperature

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April 29, 2020, 14:45		#2
duri Senior Member duri Join Date: May 2010 Posts: 245 Rep Power: 17	Density based approach are good for very low speed flows better use pressure based solver with density as function of temperature (not ideal gas).