Learning Forum

[juju]

Greetings,  I hope you guys are doing well.

I am using Ansys cfx. I have modeled a coaxial pipe (inner pipe length 78 m , outer pipe length 80 m) used as a borehole heat exchanger (BHE) ,where the fluid (water) enters the inner pipe at 30 deg C and travels to the end of  the inner pipe then circulates and exists the outer pipe leaving the heat exchanger at a cooler temperature. The pipes act as a heat exchanger because the fluid that is circulating looses its heat to the soil that surrounds the outer pipe. The solution isn't right because the temperature of outlet water is 30 deg C which means there wasn’t any heat transferred due to conduction or convection. Your help will be extremely appreciated, thank you in advance.

This is the geometry:

1- Inner pipe

[Rob]

Check the interface/wall settings and also outer (soil) temperature. n

[juju]

These are the interfaces/wall settings. Is there any error you could please point out, would be appreciated. n1- Domain interface 1:n2- Domain interface 2:n3- Domain interface 3:n4- Domain interface 4: nThis is the soil settings:n nThis is the inlet water settings:nThis is the outlet water settings:nn

[juju]

Update, I have tried to change properties of water and pipe material (steel) and the temperature at outlet is very unrealistic. The surrounding soil temperature is 23 deg C and the water inlet is 30 deg C so at most the water outlet temperature should be 23 deg C (same temperature as soil) but it comes out as 7 deg C! Not only that but when I check the soil temperature in results it says undefined. Any advice would be helpful! Thank you.n

[DrAmine]

Please make a better summary of your case and better screenshots to understand what is going on. I do not understand how many domain you havenn1/You have two fluid domains? Both fluid domains are using Water as working medium?n2/The large body surrounding both fluid domains is the solid soil? Right? At first stage I would not model it: I will just assume its presence by adjusting the boundary condition of the outer fluid domainnn3/Please copy paste the first part of the outfile till Mesh Statistics here.n