Heat Flow Through Composite Slab

What factors determine the rate of heat flow through a composite slab?

A. Material's thermal conductivity, slab's thickness, and temperature difference
B. Surface area and material's color
C. Volume and weight of the slab

Answer:

A. Material's thermal conductivity, slab's thickness, and temperature difference

Heat flow through a slab is determined by several factors, including the material's thermal conductivity, the slab's thickness, and the temperature difference across the slab. In essence, the flow of heat through the slab is described by the formula KA(T₂ – T₁), where K is the thermal conductivity, A is the surface area, and (T₂ – T₁) is the temperature difference across the slab.

Thermal resistance or 'R factor', provides a measure of insulation by accounting for the thermal conductivity and material's thickness. It is calculated as the ratio of d/k, with 'd' being the thickness and 'k' being the thermal conductivity of the material. The larger the R factor, the better the insulation.

For example, if we consider a pan with a thickness (d) = 0.800 cm and a thermal conductivity (k) = 220 J/s · m·°C, the R factor is simply d/k. Manipulating these factors allows for the development of insulators that optimize heat retention or dissipation depending on the circumstance.