The wall of an industrial furnace is constructed from 0.15-m-thick, fireclay brick having a thermal conductivity of LZ W/m.K. Measurements made during steady state operation reveal temperatures of 1400 and 1150 K at the inner and outer sur- faces, respectively. What is the rate of Teat loss through a wall that is 0.5 m by 1.2 m on a side?

Respuesta :

Answer:

The rate of heat loss through the wall is 1700 watts.

Explanation:

The complete statement of the problem is:

The wall of an industrial furnace is constructed from 0.15-m-thick, fireclay brick having a thermal conductivity of 1.7 W/m·K. Measurements made during steady state operation reveal temperatures of 1400 and 1150 K at the inner and outer sur- faces, respectively. What is the rate of heat loss through a wall that is 0.5 m by 1.2 m on a side?

Given that wall of the industrial furnace is under steady conditions of heat transfer and whose configuration is a flat element, we use the equation of conductive heat transfer rate ([tex]\dot Q[/tex]), measured in watts:

[tex]\dot Q = \frac{k\cdot w\cdot h}{l}\cdot (T_{i}-T_{o})[/tex]

Where:

[tex]k[/tex] - Thermal conductivity, measured in watts per meter-Kelvin.

[tex]w[/tex] - Width of the wall, measured in meters.

[tex]h[/tex] - Height of the wall, measured in meters.

[tex]l[/tex] - Thickness of the wall, measured in meters.

[tex]T_{i}[/tex] - Inner surface temperature, measured in Kelvin.

[tex]T_{o}[/tex] - Outer surface temperature, measured in Kelvin.

If we know that [tex]k = 1.7 \,\frac{W}{m\cdot K}[/tex], [tex]w = 1.2\,m[/tex], [tex]h = 0.5\,m[/tex], [tex]l = 0.15\,m[/tex], [tex]T_{i} = 1400\,K[/tex] and [tex]T_{o} = 1150\,K[/tex], the steady state heat transfer is:

[tex]\dot Q = \left[\frac{\left(1.7\,\frac{W}{m\cdot K} \right)\cdot (1.2\,m)\cdot (0.5\,m)}{0.15\,m} \right]\cdot (1400\,K-1150\,K)[/tex]

[tex]\dot Q = 1700\,W[/tex]

The rate of heat loss through the wall is 1700 watts.

The rate of heat transfer is 1700 W

Heat Transfer:

Given that the wall of the industrial furnace is under steady conditions of heat transfer.

The conductive heat transfer rate is given by:

[tex]\frac{Q}{t}=\frac{kA\Delta T}{d}[/tex]

here Q/t is the rate of heat transfer

A is the area,

d is the thickness of the wall here,

ΔT is the temperature difference, and

k is the thermal conductivity

Now,

area of the wall A = 0.5×1.2 = 0.6 m²

d = 0.15 m

k = 1.7 W/mk

and ΔT = 1400 - 1150 = 250K

So,

[tex]\frac{Q}{t}=\frac{1.7\times0.6\times250}{0.15}\\\\\frac{Q}{t}=1700\;W[/tex]

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