Thermodynamics

Thermal conductivity

Thermal conductivity is a fundamental concept in heat transfer and is crucial in multiple industries and scientific disciplines. It refers to the ability of a material to conduct heat or the rate at which heat transfers through a substance. Understanding heat and its relationship to thermal conductivity is essential for designing efficient thermal systems, optimizing energy usage, and ensuring the safety and performance of various materials and products. Thermal conductivity is determined by various physical factors that govern the flow of heat energy.

The thermal conductivity of a material is a measure of its ability to conduct heat. It is commonly measured in W·m⁻¹·K⁻¹.

The defining equation for thermal conductivity is calculated by known as Fourier's Law for heat conduction.

This Youtube video explains the equation for better understanding

Thermal resistance

Thermal resistance is a quantification of how difficult it is for heat to be conduct. The higher the thermal resistance, the more difficult it is for heat to be conducted, and vice vers.

The thermal resistance can be considered in the same way as the electric resistance. The basic formulas of thermal calculation can be treated in the same way as Ohm's raw. R is used as the symbol for the electric resistance, while θ (theta) is used for the thermal resistence.

Electric		Thermal
Voltage difference ΔV (V)	∆𝑉 = 𝑅 × 𝐼	Temperature difference ΔT (°C)	∆𝑇 = 𝑅𝑡ℎ × 𝑃
Electric resistance R (Ω)	𝑅 = ∆𝑉 / 𝐼	Thermal resistance Rth (°C/W)	𝑅𝑡ℎ = ∆𝑇 / 𝑃
Current I (A)	𝐼 = ∆𝑉 / 𝑅	Heat flow P (W)	𝑃 = ∆𝑇 / 𝑅𝑡ℎ

Measurement thermal conductivity

• Experimental methods
  • Steady-State Heat Flow
  • Transient Hot Wire Method
  • Laser Flash Analysis

• Non-Destructive methods
  • infrared thermography, ultrasound, and thermal wave analysis

Temperature gradient

A temperature gradient refers to the difference in temperature between two points in a material or between two adjacent materials. Heat transfer occurs when there is a temperature gradient, with heat flowing from regions of higher temperature to regions of lower temperature. When there is a temperature difference, the system will naturally attempt to balance the temperatures, leading to heat transfer and thermal conductivity