The center of gravity is the point at which the entire weight of a body may be considered to act. In agricultural engineering, understanding the center of gravity is crucial for the stability of tractors and farm machinery, especially when operating on uneven terrain or slopes to prevent tipping.

The radiator cap is designed to maintain a specific pressure within the cooling system to raise the boiling point of the coolant, thereby increasing cooling efficiency. A pressure range of approximately 0.35 to 0.40 kg/cm² is standard for many agricultural tractor cooling systems to prevent cavitation and boiling under heavy operational loads.

The heat of vaporization, or latent heat of vaporization, is the specific amount of energy required to overcome the intermolecular forces of a liquid to transform it into a gas without changing its temperature. This concept is fundamental in agricultural engineering, particularly in drying processes and refrigeration systems.

For long-term storage of paddy (up to one year), a moisture content of 12% on a wet basis is considered safe. This level inhibits the growth of storage fungi and reduces the rate of respiration, thereby preserving grain quality and preventing significant dry matter loss.

The angle of repose is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. For granular agricultural materials, the angle of repose is generally higher than the angle of internal friction due to the interlocking nature of the particles.

The bulk density of agricultural commodities is essential for designing storage structures and handling equipment. The ASAE standard for rough rice (paddy) specifies a bulk density of approximately 576 kg/m³. This value is used by agricultural engineers to calculate the capacity of silos, bins, and transport vehicles, ensuring that structural loads are properly accounted for during the post-harvest storage phase of rice production.

Sphericity is a measure of how closely the shape of a grain approaches that of a perfect sphere. For most agricultural grains, such as wheat, rice, or maize, the sphericity value falls between 0.32 and 1.0, as these grains are rarely perfectly spherical but exhibit varying degrees of roundness.

The angle of repose is the steepest angle of descent or dip of the slope relative to the horizontal plane when material on the slope face is on the verge of sliding. For wheat, due to its shape and surface friction characteristics, the angle of repose generally falls within the range of 23 to 28 degrees, depending on moisture content and variety.

Thin layer drying is defined by a grain bed depth where all grains are exposed to the same drying air conditions. A thickness of up to 20 cm is generally considered the limit to ensure uniform moisture removal without creating significant gradients.

The psychrometric chart is a fundamental tool in agricultural engineering for analyzing the thermodynamic properties of moist air. It plots variables such as dry-bulb temperature, wet-bulb temperature, dew point, humidity ratio, relative humidity, and enthalpy, allowing engineers to calculate the energy changes involved in drying and storage processes.