1. Not finding help here? Sign up for a free 30min 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!

Heat pumps and coeffiecent of performance

  1. Feb 24, 2007 #1
    Hi everyone, I was hoping to ask a thermodynamics problem, specificially one about heat pumps and coeffiecent of performance. I am wondering if I am missing something.

    I am given that heat pump is heat a building. Inside temperature is to be maintained at 22 degree celcius, outside is -5.0 celcius. The coefficent of performance is 3.8, and the the pump delivers 7.6MJ of heat each hour to the building. I need to find out at what rate work needs to be applied to run the pump.

    2. Relevant equations

    Now I believe the equation of the the coeffiecient of performance (CP) is equal to:

    cp = |Q|/W

    Now this is where I am confused, as I don't understand what (if anything) I am supposed to do with the temperatures given. I know cp, and I know Q, so I can solve for W needed to run the pump can't I? I would need to convert the heat produced to be in SI in order to get Watts as a result of course.

    thanks for your help!
  2. jcsd
  3. Feb 25, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    If we treat the heat pump as a Carnot heat pump we can say that;

    [tex]\frac{Q_2}{Q_1} = \frac{T_2}{T_2}[/tex]


    [tex]\eta^{HP}_{C} = \frac{Q_1}{W} = \frac{Q_1}{Q_1-Q_2} = \frac{T_1}{T_1-T_2}[/tex]

    Where T1 and T2 are the temperatures of the hot and cold reservoirs respectively.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Heat pumps and coeffiecent of performance
  1. Heat Pump (Replies: 3)

  2. Heat Pumps (Replies: 3)

  3. Heat Pump (Replies: 6)

  4. Heat Pump performance (Replies: 7)

  5. Heat Pump (Replies: 3)