Hey,
Your question isn't very specific, so I will give you only a general answer: Just describe all Components that you have in your System like: Condenser, Compressor and so on. Describe each Component with all the physicial equations that belong to it like p * V = m * R * T, and so on.
But I actually think that there are allready libraries for calculation of cooling Systems. You should do a little google search.

Hi,
     Thanks for your reply.
     But I am new to this equation based modeling. I am confused about the exact equations required. For example motor drives the compressor. Then for motor, I need current supply and then this drive is given to compressor in terms of torque. But how to get those equations to capture the physics. And if I want to generalize the compressor componenet. I want to drive the compressor by turbine. Actually I am confused. I am not getting where to start. My aim is to find the motor power required for compressor in compression.
     I think my reply is not to the point. This may be because I am not aware of the modeling in modelica.
     

Thanks and regards,
Yoga

Okay, first of all, there are components in the modelica standard library (MSL) that you can use. You don't need to model the engine that drives compressor yourself. At first i would make it constant anyway.
Maybe you should read some Tutorials first.
First you need to create your connector. Think about which Variables you need to communicate between the components. I think you need massflow, pressure as well as temperature and enthalpie is sufficient. The connector Model would look like this

connector Con;
flow Real mFlow;
Real Pressure;
flow Real Enthalpie;
Real Temperature;
end Con;

Then you start with your first component, for example the compressor. For the first model I wouldnt bother with a connection to a motor, just put a constant mass flow rate. You also need two connectors (of type Con). I call them a and b.

model Compressor;
Con a;
Con b;
Real delta_p;
Real VolFlow;
Real T = Temperature;
constant Real R = 287;

equation
a.mFlow = - b.mFlow "What goes in goes out again";
a.mFlow = 5 "your constant flow, you can later set this by an external connector";
a.Pressure - b.Pressure = delta_p;
delta_p * VolFlow = a.mFlow * R * T;

// and so on, actually I don't know alot about thermodynamics myself, so you need to figure out the rest yourself. Hope it helps you to find a first start, though.

end Compressor;

Hi,
    Thank you very much for your instant reply. I will start working on compressor thing first. I think, your reply is very helpfull to go further in the modeling these components.
     Thank you very much......

regards,
yoga