sinan ozbolgili


 thaks for reply, 

Actually the tank is filled with ethanol and  water is passing through the helical tube.
The temperature of  inlet water is 20° and  ethanol temperature  is 5°C. i need to check when the outlet temperarure of water will be 7°C. 

For this one I think ( I am not sure ) 2-D  axisymmetric will be better to analyze.  When I checked the picture that I shared before I can see many circles .So I can define first circle as inlet and the last one as otutley. The issue is  I dont know to how connect other ones to eact other.