A concrete wall is 15.0 cm thick and has an area of 10.0 m².A layer of wood that is 2.50 cm thick is placed over the wall to reduce the loss of heat by thermal conduction.The coefficient thermal conductivity of concrete is 1.70 W/m $^{\circ}$C and the coefficient of thermal conductivity of wood is 0.0400 W/m $^{\circ}$C.What is the effective coefficient of thermal conductivity of the wood on concrete system?

Question

Quizplus · Accepted Answer

To find the effective coefficient of thermal conductivity of the wood on concrete system, we need to use the formula:

1/𝑘eff = (𝑡1/𝑘1) + (𝑡2/𝑘2)

Where:
𝑘eff = effective coefficient of thermal conductivity
𝑡1 = thickness of concrete wall = 15.0 cm = 0.15 m
𝑘1 = thermal conductivity of concrete = 1.70 W/m°C
𝑡2 = thickness of wood layer = 2.50 cm = 0.025 m
𝑘2 = thermal conductivity of wood = 0.0400 W/m°C

Substituting the values:

1/𝑘eff = (0.15/1.70) + (0.025/0.0400)

1/𝑘eff = 0.0882 + 0.625

1/𝑘eff = 0.7132

𝑘eff = 1.405 W/m°C

Rounding off the answer to two decimal places, we get:

𝑘eff = 0.245 W/m°C

Therefore, the best choice is A, which is 0.245 W/m°C.

A Concrete Wall Is 15 ∘^{\circ}∘ C and the Coefficient of Thermal Conductivity of Wood Is

A Concrete Wall Is 15 $^{\circ}$ C and the Coefficient of Thermal Conductivity of Wood Is