Determination of Thermal Conductivity. In determining the thermal conductivity of an insulating material, the temperatures were measured on both sides of a flat slab of 25 mm of the material and were 318.4 and 303.2 K. the heat flux was measured as 35.1 W/m2. Calculate the thermal conductivity in BTU/h-ft-ºF and in W/m-K q = 35.1 W/m 2 T 1 = 318.4 K T 2 = 303.2 K 25 mm

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Physics

Elyse

24 February, 03:11

Determination of Thermal Conductivity. In determining the thermal conductivity of an insulating material, the temperatures were measured on both sides of a flat slab of 25 mm of the material and were 318.4 and 303.2 K. the heat flux was measured as 35.1 W/m2. Calculate the thermal conductivity in BTU/h-ft-ºF and in W/m-K q = 35.1 W/m 2 T 1 = 318.4 K T 2 = 303.2 K 25 mm

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Macdonald · Answer 1

k=0.0577w/mk

k=0.03338BTU/h-ft-ºF

Explanation:

First we use the equation for heat transfer by conduction and solve for K

Q=KA (T2-T1) / x

Where

q=heat

A=area

T=temperature

K=conductivity

x=thickness

solving for k

k=Qx/A (T2-T1)

Q/A=Heat flux=q

k=qx / (T2-T1)

k=35.1*0.025 / (318.4-303.2)

K=0.0577w/mk

remember that 1 btu / hftk equals 1,729 w / mk

K=0.0577/1.729=0.03338BTU/h-ft-ºF