4.   Thermal case.

    It seems interesting for us to see how to simulate a case taking into account thermal transfer. So two cases were considered:
                - the first one assumes that the wall is at a given temperature 100 degC and the fluid enters at 20 degC.
                - the second case assumes that the wall is at a given temperature 20 degC and the fluid enters at 100 degC.

    It was quite easy to add the thermal aspect in our previous case. Indeed, we have just had to highlight the option "Thermal" and added the thermal initial (for the fluid) and boundary (for the wall) conditions.

First case:    Inlet temperature of the fluid:    20C
                                Wall temperature:                        100C

    Here are the temperature profiles in laminar and turbulent conditions:

Laminar case:

Turbulent case:

    The outlet temperature of the fluid is, for the laminar case, 95-100C and for the turbulent case, 30-35C.
 

Second case:    Inlet temperature of the fluid:    100C
                                     Wall temperature:                         20C

Laminar case:

Turbulent case:

    The outlet temperature of the fluid is, for the laminar case, 20-25C and for the turbulent case, 75C.

Comments

    Summary of the results: Outlet temperature of the fluid
 

 
Tw = 100C, inlet Tf = 20C
Tw = 20C, inlet Tf = 100C
Laminar
95-100C
20-25C
Turbulent
30-35C
75C

    In laminar, the outlet temperature of the fluid is quite equal to the wall temperature whereas in the turbulent case, the outlet temperature of the fluid does not reach the wall temperature.
     From the outlet temperature, it seems that the heat transfer is higher in the laminar case than in the turbulent one. Indeed. the time spent by the fluid in the labyrinth is more important in laminar conditions than in turbulent ones. In fact, by looking at the velocity profile, we can notice that the fluid even in turbulent, does not pass through the whole labyrinth. There is a preferencial way. Besides, the inlet velocity in the turbulent case is 100 times higher than for the laminar case.  So the fluid passing through the labyrinth has not enough time to be heated or cooled by the wall.
    In the other hand, we can notice, from the temperature profiles, that the heat transfer between walls and the fluid in the "dead zones" is better in the turbulent case than in the laminar one.  The convective effect of the turbulence plays an important role in the homogeneisation of the temperature in the labyrinth.
 

   Go to next page
   Go to previous page