# Homework Help: Heat Transfer Question

1. Feb 26, 2012

### bmcgann

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

Consider a brick wall, 4.0 m high, 6.0 m wide and 300
mm thick, where the thermal conductivity of the brick
is 0.8 W.m-1.K-1. During a particular one-hour period,
the temperatures of the inner and outer surfaces were
measured to be T1 14oC and T2 6oC respectively. The average
rate of heat transfer

Q*=Rate of heat tranfer (i think)

2. Relevant equations

The equation that I am trying to use is Q* = (T1-T2)*(k)*(A)/^X not sure if correct.

3. The attempt at a solution

^X is just the thickness of material
A is 4*6=24m^2
k = 0.8W/mK

so i filled in and the divided by 3600s to get an answer in joules, i know i have can wrong can someone help me out with what formulae to use for this question?

2. Feb 26, 2012

### LawrenceC

You are using the correct formula. A watt is 1 joule/second so you should not divide by 3600. To get joules/hr, multiply by 3600.

Last edited: Feb 26, 2012
3. Feb 26, 2012

### LawrenceC

Careful with the use of ^. It means exponentiation to most people.