How to simulate valves and fittings?

I was planning to use a coefficient. Is there a guide for coefficients for different fittings (valves, elbows, tees)?
I was also planning to use equivalent length (EL) and to add the additional length. However, I got a doubt. The equivalent length for valves have a wide range. Globe valve EL is much higher than EL of gate valve. Why is that? What is the difference between the valves?