Simulation model for a fuel system and water supply system for a gas turbine

I am creating a simulation model for a fuel system and water supply system for a gas turbine. I am new to modelling. So how should I approach the modelling. There are all things like pipes, pumps, valves, leakage valves etc. So how should I model the system. Is it like model the efficiency of each by creating mathematical formulas on paper and combine.If yes what kind of mathematical formulas should I look into, to model the system. I am not sure. Please let me know. Thanking You.