Solve for Cold Surface Temp. of Slab with Heat Flow Rate 240 W

Click For Summary

Homework Help Overview

The problem involves calculating the temperature of the cold surface of a slab given a heat flow rate of 240 W, the area of the slab, its thickness, and thermal conductivity. The hot surface temperature is provided as 40°C.

Discussion Character

  • Exploratory, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the relevant equations for heat flow and attempt to manipulate them to find the temperature difference. There are questions about the correct application of the equations and the values used in calculations.

Discussion Status

Some participants are exploring the calculations for temperature difference and questioning the results obtained, noting discrepancies that suggest further investigation is needed. There is no explicit consensus on the approach or results yet.

Contextual Notes

Participants are working with specific values for area, thickness, and thermal conductivity, but there seems to be confusion regarding the units and the application of the equations. The thickness is noted in meters, and there is a concern about the accuracy of the temperature difference calculated.

yankees26an
Messages
36
Reaction score
0

Homework Statement


The absolute value of the heat flow rate through a slab of area 0.83 m2 is 240 W. The
thickness of the slab is 1.4 cm and its thermal conductivity is 0.6 W/(m·K). If the hot surface of the slab is at 40°C find the temperature of the cold surface.


Homework Equations



H = -kA(\DeltaT/\Deltax)

H = Q/t?

The Attempt at a Solution



A = 0.83 m^2; \Deltax = 1.4; k = 0.6 W/(m·K); Thot = 40°C;

Missing H?
 
Physics news on Phys.org
yankees26an said:

Homework Equations



H = -kA(\DeltaT/\Deltax)

H = Q/t?

this should be

\frac{dQ}{dt}=-kA \frac{d\theta}{dx}

or

ΔQ/Δt=-kA(Δθ/Δt)

you were given ΔQ/Δt as 240 W
 
ok so

\DeltaT = (\Deltax*H)/(kA)

\DeltaT = 1.2*240/0.6*0.83


\DeltaT = 578 K = 305 C ?? That's way above any answer options
 
yankees26an said:
\DeltaT = 1.2*240/0.6*0.83

this should be 0.014m
 

Similar threads

  • · Replies 14 ·
Replies
14
Views
7K
  • · Replies 12 ·
Replies
12
Views
2K
Replies
1
Views
2K
  • · Replies 5 ·
Replies
5
Views
3K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 3 ·
Replies
3
Views
3K
  • · Replies 1 ·
Replies
1
Views
2K