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: The motor that drives a reversible refrigerator produced 142 W

  1. Dec 12, 2011 #1
    1. The problem statement, all variables and given/known data

    The motor that drives a reversible refrigerator produced 142 W of useful power. The hot and cold temperatures of the heat reservoirs are 20°C and -6.1°C. What is the maximum amount of ice that can produce in 2.2 hours from water that is initially at 6.0°C?

    2. Relevant equations

    ΔS= Q/T

    3. The attempt at a solution

    I converted the temperatures into K, so 20°C= 293 K and -6.1°C= 266.9 K.
    I found the efficiency using e=1- Tc/Th= 1- (266.9/293)= 0.089

    after this, I am unsure how to solve the problem. Please help!! thank-you :)
  2. jcsd
  3. Dec 13, 2011 #2

    Andrew Mason

    User Avatar
    Science Advisor
    Homework Helper

    Re: Entropy

    You don't have to worry about entropy at this stage. You have to determine the maximum amount of heat flow from the cold reservoir in 2.2 hours and relate that to the amount of heat flow that must be removed from the water to make a unit (eg a gram or kg) of ice to determine the units of ice made.

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