How to Perform Analysis of Flow through a Pipe
 

My project is where there will be a heating element in the form of a rod inside the pipe. Now I will give internet heat generation to the rod and I want to flow the water through the pipe so that it may take away heat.

Actually in my design, I have nozzles at the ends of water, how can I tell ANSYS Mechanical that water enters from one nozzle and leaves from other and takes away heat?

There are various ways you could do this, depending on the degree of accuracy you are looking for...

If you primarily want to study the flow, you could run an actual CFD simulation of the flow. This could be done as just a CFD solution with temperature boundary conditions, or you could get more accurate with a 1 way coupling or even two way coupling in Workbench. If you are planning on solving the fluid volume, the first thing you need to do is extract that fluid volume from the mechanical model. If you are using DM, look up "enclosure" in the help. Once you have that fluid region, you could choose the inlets and outlets, flow rates, etc. I am sure there are tutorials that cover how to extract the fluid model from the mechanical one.

If you are primarily interested in the mechanical side and would prefer to avoid CFD, you can get a rough idea of the behavior with various boundary conditions applied to the FE model. For instance, you could apply a convection coefficient. I am sure you can find more info on how to do this also.

I am able to do the analysis using convection coefficient but the thing I want to go in detail and want to study the water flow patterns plus temperature variations. Also I want to perform the analysis on workbench using Stead-State Thermal and Transient Thermal.

I have already read about enclosures but I don't exactly get how to extract t his fluid volume from the body. Could you please tell me in detail?

This can help http://www.youtube.com/watch?v=Bb8Tsd9eGe4

the first tutorials in designmodeler will walk you through how to generate a fluid domain...
Good luck

But it will just cut out material while in my case I want that water flows through rods which are heating.