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: Heat Engines and Work

  1. Aug 16, 2012 #1
    1. The problem statement, all variables and given/known data

    There is a heat engine with Th on top at 100 J pointing down, Tc on bottom pointing down with 50 J and the work output is 50 J pointing right out of the engine. (ENGINE 1)

    a) Draw the diagram for a carnot refrigerator which draws 100 J of heat from the hot reservoir (Th = 450 K and Tc = 270 K). we have to find the work output and the heat dumped to the cold reservoir. Using this information, make a new heat engine. (ENGINE 2)

    b) what is the engine that results when you combine the two engines. (#1 and 2)

    c) what is interesting about this combination?

    2. Relevant equations

    efficiency = 1 - QL/QH
    ideal efficiency = 1 - TL/TH

    3. The attempt at a solution

    A carnot engine is basically one in which everything is perfect. This can never exist in reality. In the refrigerator heat engine, the arrow for TH should point up, the arrow for TL(TC) should point up and the energy should point in. However, I am not able to figure out the values for them besides the fact that TH is 100 J since that is given. Without this information, I can't do part B and C
  2. jcsd
  3. Aug 17, 2012 #2
    Why does no one know this? Please ask me if you are having trouble understanding the problem.

  4. Aug 17, 2012 #3

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    A refrigerator moves heat from the cold reservoir to the hot reservoir. What you are describing is a heat engine, not a refrigerator.

    The reason no one has responded so far may be because the question makes no sense. Please give us the exact wording.

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