Equal amounts of a liquid metal at the same temperature are poured into three moulds made of steel, copper and aluminium. The shape of the cavity is a cylinder with 15 mm diameter. The size of the moulds are such that the outside temperature of the moulds do not increase appreciably beyond the atmospheric temperature during solidification. The sequence of solidification in the mould from the fastest to slowest is (Thermal conductivities of steel, copper and aluminium are 60.5, 401 and 237 W/m-K, respectively. Specific heats of steel, copper and aluminium are 434, 385 and 903 J/kg-K, respectively.
Copper – Aluminium - Steel
For a large mould, heat extraction increases with thermal effusivity \(\sqrt{k\rho c}\). The supplied values rank copper above aluminium above steel. Solidification is therefore fastest to slowest: Copper – Aluminium – Steel.
Important Questions from Fourier Law and Thermal Conductivity
Which of the following substances has the minimum value of thermal conductivity ?
- The rate of flow of heat through a simple homogeneous solid is directly proportional to the area of the section at right angles to the direction of heat flow, and _______.
The SI unit of Thermal Conductivity is
Which of the following has max. value of thermal conductivity?
- A steam pipe is to be insulated by two insulating materials put over each other. For best result
