sinan ozbolgili

sorry to ask some easy questions but tring to learn and solve the problem .

If I had solved the problem in 3D, I would not have given inlet and outlet for, do we need give for 2D ? 
Also in attached picture, I think reseracher did not give inlet and outlet for ethanol .

IN second picture you specfy convection outer heat transfer coeff, which is unknown actually, so cant spacfy this value.  I just know ethanol tempeature is 5° and water inlet temparature is 20°- outlet temp is 7°C. 


Another question is, still cold not understand  how to cinnect these circles in 2D ? How or what kind of boundry conditions do I need to give these circles. Even how software will understand these are contuniues circles and water passing through them.