Find the heat flow from the composite wall as shown in figure. Assume one dimensional flow KA=150 W/m°C , KB=25 W/m°C, KC=60 W/m°C , KD=60 W/m°C

The heat flow from the composite wall is 1283.263 watts.

Explanation:

The conductive heat flow through a material, measured in watts, is represented by the following expression:

Where:

- Equivalent thermal resistance, measured in Celsius degrees per watt.

- Temperature gradient, measured in Celsius degress.

First, the equivalent thermal resistance needs to be determined after considering the characteristics described below:

1) B and C are configurated in parallel and in series with A and D. (Section II)

2) A and D are configurated in series. (Sections I and III)

Section II

Section I

Section III

The equivalent thermal resistance is:

The thermal of each component is modelled by this:

Where:

- Thickness of the brick, measured in meters.

- Cross-section area, measured in square meters.

- Thermal conductivity, measured in watts per meter-Celsius degree.

If , , , , , , , , , , and , then:

Now, if and , the heat flow is:

The heat flow from the composite wall is 1283.263 watts.