1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Minimum capacity rate ratio of a heat exchanger

  1. Apr 11, 2014 #1
    1. The problem statement, all variables and given/known data
    Here is the question:

    I am confused about the solution. In the solution they found that the minimum capacity rate ratio R = C_min/C_max was zero. This is because of the term I circled in the red which I do not understand why it goes towards infinity.

    Here is the solution:

    Could someone please explain why that term goes to infinity?
  2. jcsd
  3. Apr 11, 2014 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Not a subject I know anything about, but it seems to me that ch represents the specific heat of the condensing steam. Where the steam is condensing but not changing in temperature, specific heat = ΔQ/Δθ = ΔQ/0. That said, I'm sure some of the steam would be hotter than its condensate.
  4. Apr 11, 2014 #3
    The problem statement (and the way they solve the problem) implies that not all the steam condenses. So the inlet and outlet temperatures on the steam side are supposed to be taken as 125 C. Regarding the line involving the red encircled portion, I have no idea what the max and min on (mc) or the parameter R are supposed to be used for. Anyway, the rest of the development makes perfect sense.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted