Heat And Mass Transfer MCQ Questions & Answers | Mechanical Engineering

The process of heat transfer from one particle of the fluid to another by the actual movement of the fluid particles caused by some mechanical means, is known as Forced convection
Forced convection is a special type of heat transfer in which fluids are forced to move, in order to increase the heat transfer.
This forcing can be done with a ceiling fan, a pump, suction device,

Planck's constant, symbolized h, relates the energy in one quantum (photon) of electromagnetic radiation to the frequency of that radiation. In the International System of units (SI), the constant is equal to approximately 6.626176 x 10-34 joule-seconds.

A blackbody allows all incident radiation to pass into it (no reflected energy) and internally absorbs all the incident radiation (no energy transmitted through the body).
Absorptive power is a measure of heat absorbed by an object. When heat is incident on the surface an object, a part of it is absorbed and the remaining part is reflected. Usually the absorbed radiation is converted to thermal energy, increasing the object's temperature.

Kirchhoff's law states that the emissivity and the absorptivity of a surface at a given temperature and wavelength are equal.
The ratio of the emissive power and absorptive power of all bodies is the same and is equal to the emissive power of a perfectly black body. This statement is known as Kirchhoff's law

In free convection heat transfer, Nusselt number is function of Grashoff number and Prandtl number the Nusselt number (Nu) is the ratio of convective to conductive heat transfer at a boundary in a fluid.

A regenerative heat exchanger, or more commonly a regenerator, is a type of heat exchanger where heat from the hot fluid is intermittently stored in a thermal storage medium before it is transferred to the cold fluid.

Heat Flow occurs when two object at different temperatures are in contact with each other. Heat flows from the warmer to the cooler object until they are both at the same temperature.

The ratio of the thickness of thermal boundary layer to the thickness of hydrodynamic boundary layer is equal to $$ - \frac{1}{3}.$$

Following Steps are use to reduce the thermal resistance:
In conduction, reduction in the thickness of the material and an increase in thermal conductivity.
In convection, stirring of the fluid and cleaning the heating surface.
In radiation, increasing the temperature and reducing the emissivity.

When a fluid, such as air or a liquid, is heated and then travels away from the source, it carries the thermal energy along. This type of heat transfer is called convection.