Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I How do I find an enthalpy value if my temp. is below 50 deg. celcius?

  1. Jun 29, 2018 #1
    I wanna design a curding machine (Milk to Cheese) with an open system that operate at isobaric process (contant pressure),
    P = 1 atm = 1,... bar
    the range of temperature is = 25-75 0C
    can i find an enthalpy of water from Mollier Diagram if my temp. is 25 to 75 degree celcius ? how ?

    from my view, i must seperates water properties from milk to make curds.
    so i use mollier diagram but still confuse about it.

  2. jcsd
  3. Jun 29, 2018 #2
    What is the heat capacity of water?
  4. Jun 29, 2018 #3
    the amount of heat needed to raise its temperature a certain amount. One of water's most significant properties is that it takes a lot of heat to it to make it get hot. Precisely, water has to absorb 4,184 Joules of heat for the temperature of one kilogram of water to increase 1 degree celsius (°C)
  5. Jun 29, 2018 #4
    So, why can't you use this to get the enthalpy of water at 50 C (consistent with the Mollier diagram reference state)?
  6. Jun 29, 2018 #5
    is there any equation to help me maybe ? still confuse to use this diagram :H
  7. Jun 29, 2018 #6
    Why are you using a Mollier diagram? Why aren't you using the Steam Tables? The change in enthalpy with respect to temperature is $$\Delta H=mC_p\Delta t$$assuming no change of phase.
  8. Jun 29, 2018 #7
    because from mollier diagram there is an x value which is a moisture of water parameter, and i think is a must factor to include.
    am i wrong ? or is it more simple using steam table to get the enthalpy ?
  9. Jun 29, 2018 #8
    The moisture parameter gives the fraction that’s vapor, but, in your case, you have purely a liquid stream, right? It is, of course, simpler to use the steam tables(or even the equation), and it’s more accurate than reading off a graph. You seem to need to review thetmo to get the basic concepts down pat.
  10. Jun 29, 2018 #9
    Okay ill try it using the steam table.
    Thanks you sir, i really appreciate that. glad someone can help here :smile::smile::smile::smile::smile:
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?