# Pressure drops and Temperature changes

1. Oct 14, 2011

### hpcycling2010

Hello,

I have a fluid that is going through a pressure drop (3500psi down to atmospheric) and its around 120C at the upstream temp.
The fluid can be either methanol or oil.
What kind of temperature change will I see? I am assuming it will cool down, but by how much?

Help! and Thanks ahead of time!

2. Oct 14, 2011

### dacruick

I have no idea. However, I know that pressure vs. temperature charts for water are quite common and that you might be able to make some meaningful comparisons between them. I would assume that water is harder to heat up than both methanol or oil.

3. Oct 15, 2011

### bbbeard

By "going through a pressure drop" do you mean a pressure drop like in a turbine, like in a nozzle, or like in a throttle? Turbines and nozzles are thermodynamically similar, but throttles are different.

If you throttle an incompressible fluid, the temperature will rise as the pressure energy converts to internal energy. You can find the temperature rise in a throttle by noting that the fluid passing through the throttle maintains its total enthalpy, h=u+P/ρ. The internal energy u=cT for an incompressible fluid, where c is the specific heat.

BBB