Heat Transfer Fundamentals and Engineering Science

Comprehensive practice flashcards defining core heat transfer concepts, laws, dimensionless numbers, and thermal engineering equipment covered across Chapter 13.

Conduction

The transfer of heat energy from molecule to molecule through a substance, occurring in solids, liquids, and gases in the direction of decreasing temperature.

Convection

The transmission of heat from one place to another by fluid circulation or actual movement of substance between spots of different temperatures or due to density differentials.

Radiation

The mode of heat transfer wherein energy is transferred by wave motion (electromagnetic radiation) without requiring a physical intervening medium.

Emissivity

The measure of the effectiveness of a body as a thermal radiator at a given temperature, expressed as the ratio of radiation emitted by an actual body to that of a black body.

Latent Heat of Fusion

The amount of heat required to change a substance from a solid to a liquid state without a change in temperature.

Sublimation

The phase change involving the vaporization of a solid directly into vapor without first becoming a liquid.

Deposition

The direct change of phase from vapor to solid without passing through the intermediate liquid state.

Black Body

An ideal body that absorbs all incident radiant energy that intrudes on it and emits the maximum possible energy when acting as a radiation source, having an emissivity and view factor equal to $1$.

Gray Body

A real or theoretical body whose emissivity is less than $1$ (e.g., $0.7$) and whose absorptivity and emissivity are independent of wavelength over the spectral region.

White Body

A theoretical body that reflects all radiant energy and possesses an emissivity equal to zero.

Fourier's Law

The governing physical law that provides the theoretical basis for conduction heat transfer.

Stefan-Boltzmann Law

The fundamental law that provides the basis for radiation heat transfer from bodies above absolute zero.

Stefan-Boltzmann Constant

The proportionality constant in radiation heat transfer, with an accepted value of $5.67 \times 10^{-8}\,\text{W/m}^2\text{K}^4$.

Kirchhoff's Law of Radiation

The law stating that the ratio of emissive powers to absorptivities are equal for all bodies in thermal equilibrium.

Newton's Law of Cooling

The fundamental governing principle providing the mathematical basis for convection heat transfer.

Prevost Theory of Heat Exchange

The thermodynamic theory stating that all bodies at temperatures above absolute zero ($0\,\text{K}$) continuously emit radiant energy.

Biot Number

The dimensionless ratio of the internal conductive thermal resistance of a solid to the external boundary layer convective thermal resistance.

Fourier Number

The dimensionless ratio of the rate of heat conduction to the rate of thermal energy storage within a body.

Prandtl Number

A dimensionless parameter that measures the relative effectiveness of momentum transport versus energy transport by diffusion within velocity and thermal boundary layers.

Thermal Diffusivity

The physical property of a solid that measures the rate of heat transfer relative to its energy storage capacity, measured in units such as $\text{m}^2/\text{hr}$.

Thermal Conductivity

The material property indicating the ability of a substance to conduct heat, expressed in SI units of $\text{W/m}\cdot\text{K}$, which depends on chemical composition, physical state, temperature, and pressure, but not gravitational pull.

Temperature Gradient

The primary driving force that governs the rate and direction of heat transfer between systems.

Absolute Zero

The theoretical thermodynamic state ($0\,\text{K}$) at which no further heat can be extracted from a substance and its temperature cannot be lowered further.

Heat Exchanger

A mechanical device engineered to facilitate the transfer of heat from one fluid to another.

Logarithmic Mean Temperature Difference (LMTD)

The true effective mean temperature potential between the two terminal ends of a heat exchanger.

Deaerator

A specialized heat exchanger in which water is heated to its boiling point to liberate and expel dissolved non-condensable gases.

Regenerator

A heat exchange device utilized to transfer waste heat from exhaust gases to combustion air prior to its entry into a combustor.

Parallel Flow Heat Exchanger

A flow configuration in heat exchangers where both the hot and cold fluids enter at the same end and travel in the same direction with changing temperatures.

Natural Convection

Heat transfer occurring through buoyant fluid motion induced purely by density differentials caused by temperature gradients.

Forced Convection

Heat transfer wherein fluid motion across a heat exchange surface is driven artificially by an external mechanical apparatus such as a fan or pump.

Fire Wall

A fire-resistant structural partition designed to prevent the propagation of fire, certified with a fire resistance rating of at least four hours.

Cryogenics

The scientific discipline and technology branch dedicated to the production and effects of materials at ultra-low temperatures.

Dry Ice

The solid phase of carbon dioxide ($\text{CO}_2$) that sublimates directly into gas at standard atmospheric conditions.

Thermograph

An instrument designed to detect and record the quantity of infrared radiation emitted across surface regions of human skin.

Sutherland Equation

An empirical formula utilized to calculate and predict the variation of the thermal conductivity of gases with respect to temperature.

85% Magnesia

A composite thermal insulating material composed of 85% basic magnesium carbonate (magnesia) and 15% asbestos fibers.

Heat Sink

A low-temperature thermal reservoir that absorbs and dissipates thermal energy without undergoing a substantial change in temperature.

Absorbent

A substance possessing the physical or chemical capacity to assimilate liquids or gases, commonly employed for extracting moisture or gas from a given system.