Hello, I am trying to figure out how to calculate the diameter of an orifice for a pill loop in an oil heater and pump. The hot oil is used to heat fuel in a heat exchanger, and is driven by a positive displacement pump. There is a spill loop with an orifice plate, and the requirement is that the orifice must spill a specific flow when the oil is at 200C and 25psig. the pipework either side of the orifice plate is 2", and the kinematic viscosity of the oil at 200C is 1.2 cSt. I think this is all the info that is needed? How do I calculate what orifice size will give me what flow?