Mechanisms of Heat Transfer - Vocabulary Flashcards

Vocabulary flashcards covering the three mechanisms of heat transfer (conduction, convection, radiation) and key related concepts from the lecture notes.

Conduction

Heat transfer through a solid via collisions/energy transfer between neighboring particles; driven by a temperature difference; rate given by Q̇ = kA(TH − TC)/L.

Convection

Heat transfer by the movement of a fluid (liquid or gas); involves convection currents; can be natural (due to density differences) or forced (aided by external means).

Radiation

Heat transfer by electromagnetic waves; can occur in a vacuum; all objects above 0 K emit radiation.

Heat transfer rate (Power)

The amount of thermal energy transferred per unit time; SI unit is the Watt (W).

Temperature

A measure of the average kinetic energy of particles in an object; differences in temperature drive heat transfer.

Internal energy

The total energy of a system, the sum of the energies of all its particles.

Specific heat

The amount of heat required to raise the temperature of a given mass by a certain amount.

Latent heat

Heat required to change the phase of a substance without changing its temperature.

Thermal conductivity (k)

Material property that determines how easily heat is conducted; high k = good conductor, low k = insulator.

Cross-sectional area (A)

Area perpendicular to the direction of heat flow in conduction.

Distance (L)

Separation between hot and cold regions affecting conduction rate.

TH and TC

Temperatures at the hot end (TH) and cold end (TC) in conduction.

Emissivity (e)

Factor between 0 and 1 describing how efficiently a surface emits/absorbs radiation; darker surfaces near 1, shiny surfaces near 0.

Stefan-Boltzmann constant (σ)

Constant σ = 5.6704×10^−8 W m^−2 K^−4 used in radiation calculations.

Stefan-Boltzmann law

Radiated heat rate from a surface: Q̇ = εσA T^4 (T in Kelvin).

Net radiative heat transfer (Q_net)

Difference between emitted and absorbed radiation: Qnet = εσA(T^4 − Ts^4) (T and T_s in Kelvin).

Black body

Idealized surface with emissivity e ≈ 1; absorbs and emits radiation perfectly.

Vacuum bottle

Insulation device with a vacuum to minimize conduction and convection; silvered surfaces reduce radiation.

Thermal paste

High-k material placed between CPU and heatsink to fill air gaps and improve conduction.

Natural convection

Convection driven by natural density differences due to temperature variation, without external forcing.

Forced convection

Convection aided by external forces (fans, pumps).

Greenhouse effect

Atmospheric CO₂ and other gases absorb infrared radiation and re-radiate it, warming the surface.

Global warming

Long-term increase in Earth's average surface temperature due to enhanced greenhouse effect and related factors; affects climate systems.

Kelvin temperature (T in radiative laws)

Temperature must be in Kelvins for radiation formulas; absolute scale starting at 0 K.

Dark vs. bright surface emissivity

Dark surfaces tend to have higher emissivity (closer to 1) than bright/shiny surfaces (closer to 0).

Conduction heat transfer equation (conduction-focused)

Q̇ = kA(TH − TC)/L, showing how material properties and geometry set the rate of conduction.