Thermal Design And Optimization Bejan Pdf Download Zip ((EXCLUSIVE)) ➡️

In the simplest terms, the direction of a thermal flow is always in the direction of increasing temperature, because this is the only direction of motion that does not violate the second law of thermodynamics. In no case does heat ever flow backwards, in the direction of decreasing temperature.

Thermal conductivity is the physical property of a material that can pass thermal energy, in the form of heat, to a colder material (in the natural world, that colder material is the environment) and thus become hotter, the opposite action being known as heat capacity. The thermal conductivity of materials (and fluids) is closely related to their viscosity, and this relationship is shown graphically in figure2. Thus, the lower the viscosity, the higher the thermal conductivity. This property can be used to help make a material with high thermal conductivity that also has low viscosity. The more viscous a material is, the more difficult it is to move and cool. For this reason, materials with a low thermal conductivity are often used in insulators. The thermal conductivity of a solid material is a function of the thermal conductivity of its component substances. If two substances have the same thermal conductivity, they tend to be combined in random fashion, forming a solid substance with the composite’s thermal conductivity being a linear combination of the constituent substances. In insulating materials, the thermal conductivity is often low because the insulator is usually made up of glass fibers with small thermal conductivity.