What Is the Definition of Thermal Energy Transfer

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Thompson and Joule showed that this calorie theory was wrong. Heat is not a substance as assumed, but a movement at the molecular level (so-called kinetic theory). A good example is rubbing your hands together. Both hands get warmer, although initially they had the same cooler temperatures. If the cause of the heat had been a liquid, then it would have flowed from one body (warmer) with more energy to another with less energy (colder). Instead, the hands are heated because kinetic energy (friction) has been converted into heat in a process called “friction.” The thermal conductivity of gases can be understood with the imagination of molecules. These molecules move from one position to another by thermal motion, as can be seen in the image below: Efficient use of energy is the goal of reducing the amount of energy needed for heating or cooling. In architecture, condensation and airflow can cause aesthetic or structural damage. An energy audit can help assess the implementation of recommended remediation procedures. For example, improving insulation, airtightness of structural leaks or adding energy-efficient windows and doors.

[31] Radiation is the transfer of heat by electromagnetic waves. When you stand in the sun, you are warmed by electromagnetic waves, mainly infrared radiation (and to a lesser extent visible light) that travel from the sun to Earth. In addition to the sun, light bulbs, irons and toasters also transmit heat by radiation. Note that unlike conduction or convection, heat transfer by radiation does not require material to assist in transmission. Convection heat transfer, or simply convection, is the transfer of heat from one place to another through the movement of liquids, a process that is essentially the transfer of heat by mass transfer. The mass movement of the liquid improves heat transfer in many physical situations, such as (for example) between a solid surface and the liquid. [10] Convection is generally the dominant form of heat transfer in liquids and gases. Although sometimes considered the third method of heat transfer, convection is generally used to describe the combined effects of thermal conduction in the liquid (diffusion) and heat transfer by bulk fluid flow. [11] The process of fluid flow transport is called advection, but pure advection is a term generally associated only with mass transport in liquids, such as.B. the advection of pebbles in a river.

In the case of heat transfer in liquids, where advection transport in a liquid is always accompanied by heat diffusion transport (also called thermal conduction), the heat convection process is understood as the sum of heat transport by advection and diffusion/conduction. Heat transfer is a process function (or path function), as opposed to state functions; Therefore, the amount of heat transferred into a thermodynamic process that changes the state of a system depends on how that process unfolds, not just the clear difference between the beginning state and the end state of the process. Heat transfer takes into account the energy balance of the systems studied. When studying thermomechanical components, structural deformations caused by the effects of thermal stress on solids can also be included. Simulation of stress response to heat loads and failures is essential for many industrial applications. An example application is a thermal stress analysis of a printed circuit board. However, scientists around the world use the Kelvin scale (K without degree sign), named after William Thomson, 1st Baron Kelvin, because it works in calculations. This scale uses the same increment as the Celsius scale, i.e. a temperature change of 1°C corresponds to 1 K.

However, the Kelvin scale starts at absolute zero, the temperature at which there is a complete absence of thermal energy and all molecular movements stop. A temperature of 0 K is equivalent to minus 459.67°F or minus 273.15°C. Our ocean currents also move in the same way, so in the Gulf of Mexico the water becomes very hot, this warm air expands, moves and sticks what we call the Gulf Stream. These are two good examples of convection, the movement of hot particles from warmer places to colder places. The third form of radiation notes that both involve particle movement or direct contact of particles or molecules. The third type of radiation involves the movement of electromagnetic waves and these do not need matter to pass, so the sun sends us these electromagnetic waves directly. What are some of these waves? Highly visible light is an electromagnetic wave, microwaves, gamma waves, X-rays, infrared and UV rays, these are all different types of radiation or electromagnetic waves. These are therefore the three important means of thermal energy transfer, how energy is transferred from one source to another. Conduction is the transfer of energy from one molecule to another by direct contact.

This transfer occurs when the molecules hit each other, like a game of billiards where one moving ball hits another, causing the second to move. Conduction takes place in solids, liquids, and gases, but works best in materials that have simple molecules that are close to each other. For example, metal is a better conductor than wood or plastic. The temperature achievable at the target is limited by the temperature of the hot radiation source. (Law T4 causes radiation to return to the source.) The sun (on its surface) a little 4000 K hot makes it possible to reach a rough 3000 K (or 3000 ° C, which corresponds to about 3273 K) on a small probe at the focal point of a large concave and concentrated mirror of the solar furnace of Mont-Louis in France. [18] Heat convection occurs when the mass flow of a liquid (gas or liquid) carries its heat through the liquid. All convective processes also displace heat in part by diffusion. The flow of liquid can be forced by external processes or sometimes (in gravitational fields) by buoyancy forces caused when thermal energy expands the liquid (for example, in a fire plume), affecting its own transfer.

The latter is often called “natural convection”. The first process is often referred to as “forced convection.” In this case, the liquid is forced to drain with a pump, fan or other mechanical means. The electromagnetic spectrum (EM): This spectrum is the range of all types of electromagnetic radiation. Simply put, radiation is an energy that propagates and propagates like photons emitted by a lamp or radio waves. Other known types of electromagnetic radiation are X-rays, gamma rays, microwaves, infrared light, etc. (^7). The third law states that the entropy of a pure crystal at absolute zero is zero. As explained above, entropy is sometimes called “lost energy”, i.e. energy that is not able to work, and since there is no thermal energy at all at absolute zero, there can be no energy lost. .

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