# Carnot Engine Problem

1. Oct 10, 2009

### tresehulyo

1. The problem statement, all variables and given/known data

A Carnot Engine operating between 900 Fahrenheit and 90 Fahrenheit produces 40,000 ft-lb of work. Determine (a) the heat supplied, (b) the change in entropy during heat rejection and (c) the thermal efficiency of engine. (answers should be in BTU)

2. Relevant equations

What formula for Change in S Entropy do i need to use in here

3. The attempt at a solution

(a) 22.74 BTU
W=NQH
=.60(40000 ft-lb * (9.478* 10-4 BTU / 1 ft-lb)
= 22.74 BTU

(c) 60%
Nth = 1 - (TL/TH)
= 1 - ((90+460)/(900+460))
=.59 = 60%

2. Oct 12, 2009

### gabbagabbahey

Look up "Entropy in the Carnot Cycle".

Again, you can get a more accurate answer if you use $T_{\text{abs}}=T_{\text{Ferenheit}}+459.67$ instead.