Conductive heat transfer

Physical terms

synonym heat conduction (Heat conduction) generally refers to conductive heat transfer

This entry is made by Compilation and application of scientific encyclopedia entries of "Science Popularization China" to examine.

Chinese name: Conductive heat transfer
Foreign name: heat conduction
Category: Physical definition

Mathematical expression: Fourier’s law
Application examples: Heat treatment of steel forgings
Abbreviation: heat conduction

catalog

▪ Heat conduction of fin
▪ Other applications

definition

Announce

edit

When there is no relative displacement between parts of the object molecule 、 atom , and free electron etc. Microparticle Of Thermal movement The generated heat transfer is called heat conduction, or heat conduction for short. For example, the transfer of heat inside a solid from a part with higher temperature to a part with lower temperature, and the transfer of heat from a solid with higher temperature to another solid with lower temperature are both heat conduction phenomena.^[1]

Conductive heat transfer is one of the three basic ways of heat transfer, and the other two ways are Convective heat transfer 、 Radiant heat transfer 。

nature

Announce

edit

Fourier's law

Based on the experience of a large number of actual heat conduction problems, the law of heat conduction phenomenon has been summarized as Fourier (Fourier) law.

Figure 1-2^[1]

The heat conduction of two flat plates with uniform surface temperature as shown in Fig. 1-2 is investigated. This is a one-dimensional heat conduction problem, that is, the temperature is only in the x direction for any infinitesimal layer with a thickness of dx, according to Fourier's law , heat conduction through the layer in unit time quantity of heat It is proportional to the local temperature change rate and plate area A, that is

, where,

Is the conduction of heat, α Is the proportional coefficient, called thermal conductivity, also called thermal conductivity The negative sign indicates that the direction of heat transfer is opposite to the direction of temperature rise.

thermal conductivity

Heat conduction of different substances coefficient Different; The thermal conductivity of the same material is related to its structure, density, humidity, temperature, pressure and other factors.^[1] When the water content of the same substance is low and the temperature is low, heat conduction The coefficient is small. Generally speaking, the thermal conductivity of solid is greater than that of liquid, while that of liquid is greater than that of gas. This difference is largely due to the different molecular spacing between the two states. The coefficient value used in engineering calculation is determined by special tests.

thermal resistance

The resistance encountered by the heat on the heat flow path reflects the heat transfer capacity of the medium or between the mediums, indicating that the resistance caused by 1W heat temperature rise Size in ℃/W or K/W. The temperature rise on the heat transfer path can be obtained by multiplying the thermal power consumption by the thermal resistance. A simple analogy can be used to explain the meaning of thermal resistance. The heat exchange is equivalent to current, and the temperature difference is equivalent to voltage thermal resistance amount to resistance 。

application

Announce

edit

Heat conduction of fin

Rib Also known as fins or fins, they are commonly used in heat exchange equipment. The use of fins can increase the heat transfer area and reduce the convection heat transfer thermal resistance Enhance heat transfer capacity of equipment, such as condenser 、 radiator 、 Air heater wait.

The heat conduction through the fin has a feature that there is a surface in the direction of the fin extension Convective heat transfer and Radiant heat transfer Therefore, in the direction of heat conduction heat flow transmission Heat flow It is constantly changing.^[1]

Other applications

In industry, there are many Heat transfer process , such as heating of rubber products vulcanization , heat treatment of steel forgings, etc. The law of heat conduction plays an important role in the design and calculation of kilns, heat transfer equipment, thermal insulation and the analysis of temperature distribution of catalyst particles. In high-temperature and high-pressure equipment (such as Ammonia converter And large ethylene In device Waste heat boiler In the design of), the heat conduction law shall also be used to calculate the temperature distribution For thermal stress analysis.

Novice on the road

Growth task Getting Started with Editing Edit Rule Edit by myself

I have questions

Content query Online Service Official post bar Feedback

Complaints and suggestions

Report bad information Failed to appeal through entries Complaint of infringement information Blocking query and unblocking

Jinggong Network Anbei No. 1100000200001