Heat Transfer and Thermal Equilibrium

Heat Transfer Basics

In thermodynamics, heat transfer refers to the process of thermal energy moved from a hotter object to a cooler one.
Heat transfer can take place through three main modes: conduction, convection, and radiation.

Conduction is the process of heat transfer between substance particles via direct contact.
It often happens in solids as the molecules remain close to each other and transfer energy via vibrations.
Metals are great conductors due to the abundance of free-moving electrons that can quickly transfer thermal energy.

Convection, unlike conduction, relies on the movement of particles within fluids (liquids and gases).
This flow helps distribute heat throughout a fluid, with warmer, less dense parts rising and cooler, denser parts falling.
This cyclic movement is known as a convection current.

Radiation is a unique form of heat transfer that does not require a medium and can occur through empty space.
It involves the transfer of energy through electromagnetic waves. The Sun, for instance, warms the Earth’s surface through radiation.

Thermal equilibrium occurs when the transfer of heat between systems is stopped due to identical temperatures across the systems.
This represents the second law of thermodynamics which states that energy will naturally flow from regions of higher energy (hotter areas) to regions of lower energy (cooler areas) until equilibrium is achieved.
A common example is stirring a hot drink; after a while, the drink and the surrounding air reach the same temperature, achieving thermal equilibrium.

The heat transferred to or from a substance can be calculated with the equation Q=mcΔT.
‘Q’ stands for the heat transferred, ‘m’ for the mass of the substance, ‘c’ for the substance’s specific heat capacity, and ‘ΔT’ for change in temperature.

Heat transfer plays a crucial role in many sectors: household appliances, industrial processes, environmental science, meteorology, and even healthcare.
For instance, understanding conductive heat transfer is crucial in insulator design, while convection helps predict weather changes, and radiation informs us about solar panel efficiency and sunscreen use.