How can I properly include the effect of wall thermal in the geometry based Condenser Evaporator (2P-MA) block?

Hi, I want to include the effect of wall thermal mass in the geometry based Condenser Evaporator (2P-MA) block. The documentation suggested to use a pipe block with a thermal mass downstream, but I cannot understand how to avoid the pressure drops caused by this last block (they are already considered in the evap cond block), and also how to properly set the length and the hydraulic diameter for the pipe block... Have you suggestions?

Answer 1

[Balavignesh]

Hi Roberto,

It is my understanding that you would like to include the effect of wall thermal mass in the "2P-MA" block, and to properly set the length and hydraulic diameter for the pipe block.

In order to avoid counting the pressure drops twice, you could set the friction factor of the pipe block to zero, so that the pipe block will only contribute to thermal mass and not to pressure drop. In Simulink, this can be achieved by setting the 'Specify friction as' parameter to 'Friction factor' and then setting 'Friction factor' to zero.

The length of the pipe block should be set to the length of the pipe you're modeling, and the hydraulic diameter should be set based on the cross-sectional area and wetted perimeter of the pipe.For a circular pipe, the hydraulic diameter is simply the inner diameter of the pipe. For non-circular pipes, the hydraulic diameter can be calculated as '4*Area/Wetted_Perimeter'. It is important to note that the accuracy of your simulation results will depend on the accuracy of these parameters.

Kindly refer to the below documentation links to have more information on the following:

• '2P-MA' block: https://www.mathworks.com/help/hydro/ref/condenserevaporator2pma.html
• 'hydraulic pipe' block: https://www.mathworks.com/help/hydro/ug/model-a-thermal-liquid-pipeline.html

Hope that helps!

Balavignesh

[ROBERTO]

Hi Balavignesh thank you for the answer, but in the parameters dialog box of the pipe block 2P I cannot see the possibility to change the turbolent Darcy friction factor as you mentioned...