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Temperature Rise due to Increase in Pressure (Liquid)

  1. Jul 3, 2014 #1
    I need help finding the temperature rise of a liquid (specifically diesel) due to a pressure increase. The system contains a pump at 500 hp and runs at 524 gpm. The inlet temperature is 75 F and the pressure is 150 psi. The exit pressure is about 1155 psi. I have the specific gravity as 0.841. I've reduced my formula to -W=m(h1-h2) where W is the work of a pump, m is the mass flow rate, and h1 and h2 are the enthalpies. I've calculated the mass flow rate to be 3688 lb/min and the work as 21,204 Btu/min. Now, I'm stuck because I can't find the enthalpy for h1 to solve for h2. When I have h2, I was going to use that and the exit pressure to find the final temperature.

    So, am I doing this correctly? And if so, how can I determine h1? I can't find any enthalpy/pressure/temperature tables for diesel.
     
    Last edited: Jul 3, 2014
  2. jcsd
  3. Jul 3, 2014 #2

    SteamKing

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    The specific heat of No. 2 Diesel is about 0.43 BTU/lb-F:

    http://www.methanol.org/energy/resources/alternative-fuel/alt-fuel-properties.aspx [Broken]

    This should allow you to calculate a temperature rise due to the fuel absorbing the pump work.
     
    Last edited by a moderator: May 6, 2017
  4. Jul 3, 2014 #3
    OH! So, if the pump is working at maybe 70% efficiency, it's safe to assume that 30% of the horsepower isn't moving the fluid and is converted into heat? Then, I'd just take that number and find the temperature rise?

    Thanks a lot by the way!
     
  5. Jul 3, 2014 #4

    SteamKing

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    Pretty much.
     
  6. Jul 3, 2014 #5
    Strictly speaking the fluid temperature will rise with pressure increase, even if no irreversible work is applied. But that increase is very small.
     
  7. Jul 3, 2014 #6
    Well, I think I have an appropriate number. Thank you both so much!
     
  8. Jul 4, 2014 #7
    No. If the pump is working at 70% efficiency, then 70% of the supplied electrical power translates into enthalpy change. Since diesel fuel is nearly incompressible,

    h2-h1=Cp(T2-T1)+V(P2-P1),

    where V is the specific volume of the diesel fuel (the reciprocal of the density).

    Chet
     
  9. Jul 7, 2014 #8
    Oh, I see! Thanks a lot! Using your formula and a different method, I was able to come out with similar answers! I normally use tables so that formula helped me immensely!
     
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