What is Heat Flux?

First we need to know the basics.

So what is heat flux?

What are the three types of heat transfer?

Heat transfer is the transfer of thermal energy from one body to another. This can happen through three primary mechanisms: conduction, convection, and radiation. The rate of heat transfer, represented by the symbol Q, is the amount of heat that flows per unit of time. This flow of heat can be measured in various units, but one common unit is Btu/hr. This unit is often used in industrial applications where heat transfer rates are critical to the operation of machinery and systems.

• Conduction is the transfer of heat through a material by the collision of atoms and molecules. The atoms and molecules in a material can absorb and transfer heat energy through collisions with neighboring atoms and molecules.
• Convection is the transfer of heat through a fluid, such as a liquid or gas. Heat is transferred through the fluid by the movement of the fluid itself.
• Radiation is the transfer of heat through electromagnetic waves. This is the mechanism by which heat is transferred through space, such as from the sun to the earth.

The heat flux formula is best described as Fourier’s Law: q = -λΔT/Δx = -0.8 * 20 / 0.35

The rate of heat transfer, represented by the symbol Q, is the amount of heat that flows per unit of time. This flow of heat can be measured in various units. This unit is often used in industrial applications where heat transfer rates are critical to the operation of machinery and systems.

The difference between heat flow and heat flux

Heat flow is the generation and exchange of thermal energy between physical systems. Heat flux is the flow of energy per unit of area, per unit of time.

The difference between heat flux and convection

Heat flux is a measure of the rate of heat transfer per unit area, while convection is a mode of heat transfer that occurs when a fluid is heated and rises, and as it cools, it sinks, leading to a continuous transfer of heat. In other words, heat flux is a scalar quantity that describes the flow of heat through a material, while convection refers to the movement of heat in a fluid, typically caused by differences in density.

Flux units refer to the units used to measure the rate at which heat energy is transferred through a surface per unit area. The most common units of heat flux include watts per square meter (W/m2) and British thermal units per square foot per hour (Btu/ft2-hr).

So how do we measure heat flux?

Heat flux can be measured using a variety of methods, depending on the specific application. Some common methods include:

• Thermocouples are devices that measure the temperature difference between two points. They can be used to measure heat flux by placing a thermocouple on one side of a material and measuring the temperature difference between the thermocouple and the other side of the material.
• Heat flux sensors are specialized devices that are designed specifically to measure heat flux. They typically include a heat-sensitive element, such as a thermocouple or thermistor, that is in contact with the material or system being measured.
• Infrared imaging can also be used to measure heat flux. Infrared cameras can detect the temperature of a material or system and can be used to create a thermal map that shows the distribution of heat.

Heat flux can be used in a variety of applications. Some common applications include:

• HVAC Systems
• Energy conservation and management in buildings
• Automotive thermal management
• How Heat Flux Measurement Helps us Understand Batteries
• Thermal insulation and building envelope performance
• Quality control in manufacturing and materials testing
• Biomedical research and medical device development