Heat Transfer - Engineering

Q1:

__________ equation relates the thermal conductivity of a solid to its temperature.

A Antonie

B Kopp's

C Lee's

D Kistyakowski

ANS:C - Lee's

Kopp's equation is an empirical relationship that describes the temperature dependence of thermal conductivity in solids. It is named after the German physicist August Kopp, who proposed it in the 19th century. The general form of Kopp's equation is: 0))k(T)=k0​(1+α(T−T0​)) Where:

  • k(T) is the thermal conductivity of the material at temperature T.
  • 0k0​ is the thermal conductivity of the material at a reference temperature 0T0​.
  • α is the temperature coefficient of thermal conductivity.
  • T is the temperature at which the thermal conductivity is being evaluated.
Kopp's equation suggests that the thermal conductivity of a material changes linearly with temperature. The term 0)α(T−T0​) represents this linear change, where α is the temperature coefficient of thermal conductivity. The reference temperature 0T0​ is usually chosen as a standard temperature at which the thermal conductivity is known or measured. It's important to note that Kopp's equation is an empirical model and may not accurately represent the behavior of all materials over all temperature ranges. However, it provides a simple and useful approximation for describing the temperature dependence of thermal conductivity in many solids. Additionally, more sophisticated models, such as those based on quantum mechanics or experimental data, may be used for more accurate predictions in specific cases.