Hello. I am writing a relatively simple simulation code for looking at transient temperatures in a surge tank, which reflects a real-world system. The tank is hooked up to a recirculation loop with a pump and a heat exchanger. The pump has an average flowrate of 500 GPM. Despite the temperature therefore density of the water it is pumping, the pump moves "500 GPM". So my question is: When a centrifugal pump has a set flowrate of 500 GPM, is that equivalent to the conservation of mass or conservation of volume? No amount of Googling seems to have brought me any conclusions, though I have come to understand that positive displacement pumps are different than centrifugal pumps when it comes to this particular topic.