Heat conduction in the context of "Drying"

The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by ${\displaystyle k}$, ${\displaystyle \lambda }$, or ${\displaystyle \kappa }$ and in SI units is measured in W·m·K. In such units, it is the amount of thermal energy in watts (joules per second) that flows from a hotter region to a colder region per Kelvin (or degree Celsius) difference in temperature per meter of separation.

Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials such as mineral wool or Styrofoam. Metals have this high thermal conductivity due to free electrons facilitating heat transfer. Correspondingly, materials of high thermal conductivity are widely used in heat sink applications, and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is called thermal resistivity.

The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly denoted by ${\displaystyle k}$, ${\displaystyle \lambda }$, or ${\displaystyle \kappa }$ and in SI units is measured in W·m·K. In such units, it is the amount of thermal power in watts (joules per second) that flows from a hotter region to a colder region per Kelvin (or degree Celsius) difference in temperature per meter of separation.

Heat transfer occurs at a lower rate in materials of low thermal conductivity than in materials of high thermal conductivity. For instance, metals typically have high thermal conductivity and are very efficient at conducting heat, while the opposite is true for insulating materials such as mineral wool or Styrofoam. Metals have this high thermal conductivity due to free electrons facilitating heat transfer. Correspondingly, materials of high thermal conductivity are widely used in heat sink applications, and materials of low thermal conductivity are used as thermal insulation. The reciprocal of thermal conductivity is called thermal resistivity.

In physics and engineering, heat flux or thermal flux, sometimes also referred to as heat flux density, heat-flow density or heat-flow rate intensity, is a flow of energy per unit area per unit time. Its SI units are watts per square metre (W/m). It has both a direction and a magnitude, and so it is a vector quantity. To define the heat flux at a certain point in space, one takes the limiting case where the size of the surface becomes infinitesimally small.

Heat flux is often denoted ${\displaystyle {\vec {\phi }}_{\mathrm {q} }}$, the subscript q specifying heat flux, as opposed to mass or momentum flux. Fourier's law is an important application of these concepts.

In the study of heat transfer, fins are surfaces that extend from an object to increase the rate of heat transfer to or from the environment by increasing convection. The amount of conduction, convection, or radiation of an object determines the amount of heat it transfers. Increasing the temperature gradient between the object and the environment, increasing the convection heat transfer coefficient, or increasing the surface area of the object increases the heat transfer. Sometimes it is not feasible or economical to change the first two options. Thus, adding a fin to an object, increases the surface area and can sometimes be an economical solution to heat transfer problems.

One-piece finned heat sinks are produced by extrusion, casting, skiving, or milling.

In physics, a perfect fluid or ideal fluid is a fluid that can be completely characterized by its rest frame mass density ${\displaystyle \rho _{m}}$ and isotropic pressure ⁠${\displaystyle p}$⁠. Real fluids are viscous ("sticky") and contain (and conduct) heat. Perfect fluids are idealized models in which these possibilities are ignored. Specifically, perfect fluids have no shear stresses, viscosity, or heat conduction. A quark–gluon plasmaand graphene are examples of nearly perfect fluids that could be studied in a laboratory.

A vacuum flask (also known as a Dewar flask, Dewar bottle or thermos) is an insulating storage vessel that slows the speed at which its contents change in temperature. It greatly lengthens the time over which its contents remain hotter or cooler than the flask's surroundings by trying to be as adiabatic as possible. Invented by James Dewar in 1892, the vacuum flask consists of two flasks, placed one within the other and joined at the neck. The gap between the two flasks is partially evacuated of air, creating a near-vacuum which significantly reduces heat transfer by conduction or convection. When used to hold cold liquids, this also virtually eliminates condensation on the outside of the flask.

Vacuum flasks are used domestically to keep contents inside hot or cold for extended periods of time. They are also used for thermal cooking. Vacuum flasks are also used for many purposes in industry.