You have just completed the syllabus of the Heat transfer subject for the Mechanical Engineering Branch. Here you will find all the IMPORTANT FORMULAS Of Heat transfer subject. Formulas of the first chapter have displayed for your illustration
CHAPTER-1: FUNDAMENTALS OF CONDUCTION:
- Modes of Heat Transfer:
- Conduction is a mode of heat transfer that generally occurs in solids and static fluids by molecular lattice vibration energy transfer (30%) & also by free-electron transfer (70%).
- The highest conductivity (2100 W/m-K) of a diamond is due to its perfect crystalline molecular lattice arrangement.
- The thermal conductivity of gases increases with the increase of their temperature.
- The thermal conductivity of liquids decreases with increasing temperature as the liquid expands and the molecules move apart.
- In the case of solids, because of lattice distortions, higher temperatures make it difficult for electrons to flow, hence the thermal conductivity of metals decreases with an increase in temperature.
Exception – Aluminium & Uranium
- Convection is a mode of heat transfer that generally occurs between a solid & a fluid due to temperature difference associated with macroscopic bulk displacement of the fluid transporting thermal energy (heat energy).
- In the case of forced convection heat transfer, this macroscopic bulk motion of the fluid is provided by an external agency like a far or a blower or a pump.
- In the case of free convection heat transfer, this motion is provided by buoyancy forces arising out of density changes of fluid due to its temperature change.
- Radiation is a mode of heat transfer which do not require any material medium for its propagation & hence occurs by electromagnetic waves.
- All bodies emit radiation above the 0K.
- Governing Laws of Heat Transfer:
5.1. Fourier’s Law of Conduction:
The law states that “the rate of heat transfer by conduction in a given direction is directly proportional to the temperature gradient along that direction & the area of heat transfer lying perpendicular to the direction of heat transfer”.
It is given as
‘k’ is the thermal conductivity (thermophysical property) of the material of the slab.
A is the area perpendicular to the direction of the heat flow.
Thermal conductivity - It is a thermophysical property of the material that tells about its ability to allow the heat energy to get conducted through the material more rapidly.
Here are the list of some material and its thermal conductivity:
NOTE- Conductivity of Pure metal is higher than the conductivity of Alloy.
Conductivity in Gases - Conductivity in Gases is due to molecular momentum transfer.
NOTE- The conductivity of gases increases with the increase in temperature.
You can find the formula notes for the rest of the chapters of Heat transfer from below Link
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