Difference Between Heat Flow and Heat Flux

Thekey differencebetween heat flow and heat flux is thatheat flow refers to theexchange ofthermal energybetween physical systems,whereas heat flux refers to物理系统每单位每单位时间面积之间的能量流量.

术语热流和热通量是物理化学方面的重要概念，这些概念在物理系统之间的热能的行为和互换。

CONTENTS

1.Overview and Key Difference
2.What is Heat Flow
3.What is Heat Flux
4.并排比较——热流与热通量n Tabular Form
5.概括

What is Heat Flow?

热流或传热是物理系统之间的热能的产生，使用，转换和交换。我们可以将此概念分为各种机制热传导，热对流, thermal radiation and heat flow through phase changes. These mechanisms have different characteristic features, and they often occur simultaneously in the same system. Let us understand some of these mechanisms in detail.

Heat conduction is the most common type of heat flow that involves a direct microscopic interchange of the kinetic energy of particles via the boundary between two systems. It is also called diffusion. In this type of heat flow, when a body is in a different temperature from another body or from the surrounding, heat flows from high temperature to low temperature until a thermal equilibrium occurs.

Heat convection is the other common type of heat flow where a bulk flow of a fluid carries heat along with the mass flow of the fluid. Sometimes, the flow of the fluid occurs due to an external process or due tobuoyancy forcesthat are caused due to the thermal energy expansion of the fluid.

Thermal radiation, on the other hand, is a type of heat flow that occurs through a vacuum or any transparent medium. This transfer of energy occurs by means of photons in EMR waves that are governed by the same law.

What is Heat Flux?

Heat flux is a flow of energy per unit of area per unit of time. This term is also given as thermal flux, heat flux density, heat flow density, and heat flow rate intensity. We can use the SI units for the measurement of the heat flux; Watts per square meter (W/m2). This property has both magnitude and direction. Therefore, we can name it as avector quantity.

We can use Fourier’s law for most solids in usual conditions where heat is transported mainly by conduction and heat flux. There are few ways of measuring the heat flux, but the most common but impractical method is the measurement of temperature difference over a piece of material with a known thermal conductivity.

What is the Difference Between Heat Flow and Heat Flux?

术语热流和热通量是物理化学方面的重要概念，这些概念在物理系统之间的热能的行为和互换。The key difference between heat flow and heat flux is that heat flow refers to the mass flow of the fluid, whereas heat flux refers to the flow of energy per unit of area per unit of time.

Below is a summary of the difference between heat flow and heat flux in tabular form.

摘要 - 热流与热通量

热流和热通量是物理化学中相关的术语。热流和热通量之间的关键区别在于，热流是指物理系统之间的热能，使用，转换和交换热能，而热通量是指每单位时间单位面积的能量流动。

Reference:

1. “Heat Flux.” Science Direct,Available here.

Image Courtesy:

1. “Convection-snapshot” – original uploader was Harroschmeling at German Wikipedia. – Transferred from de.wikipedia to Commons.(CC BY-SA 3.0)viaCommons Wikimedia
2. “Heatflux” By Hukseflux at English Wikipedia(CC BY 3.0)viaCommons Wikimedia