Minimizing the Gaseous Component of Thermal Conductivity
A typical silica aerogel has a total thermal conductivity of ~0.017 W/mK (~R10/inch). A major portion of this energy transport results from the gases contained within the aerogel. This is the transport mode that is most easily controllable. As a consequence of their fine pore structure, the mean pore diameter of an aerogel is similar in magnitude to the mean free path of nitrogen (and oxygen) molecules at standard temperatures and pressures. If the mean free path of a particular gas were longer than the pore diameter of an aerogel, the gas molecules would collide more frequently with the pore walls than with each other. If this were the case, the thermal energy of the gas would be transferred to the solid portion of the aerogel (with its low intrinsic conductivity). Lengthening the mean free path relative to the mean pore diameter can be accomplished in three ways: by filling the aerogel with a gas with a lower molecular mass (and a longer mean free path) than air, by reducing the pore diameter of the aerogel, and by lowering the gas pressure within the aerogel.
Young Learner said:My main objective of the question was, when I have simultaneous heating and cooling on either junction a of a material as in Peltier effect, I need to extract the heat and cold temperatures separately for further use. The problem here is very quickly the hot and cold temperatures cancel out each other.
Is there anyway I can successfully transfer the heat?
Young Learner said:Yes, Peltier effect produces heats one side and cools other side.
But, when I remove the supply, The temperature from the hot side heats the cold side.
To explain it numerically, When I apply a voltage V to a Peltier module, heat is dissipated at one side and absorbed on the other. Let us say that the temperature at one side is 200 C and temperature at the other side is -200 C.
When I remove the supply, the temperature at both the sides become 0. I need to separate 200 C and -200 C for further use.
A heat conductor is a material that allows heat to easily pass through it. This means that when one end of a conductor is heated, the other end will also become hot. Some common examples of heat conductors are metals, such as copper, aluminum, and iron.
A good heat conductor is typically a solid material that is dense, has a high thermal conductivity, and is able to transfer heat quickly and efficiently. It should also have a low specific heat capacity, meaning it can absorb and release heat quickly, and be able to maintain its shape and structure when heated.
As mentioned earlier, some common examples of heat conductors are metals, such as copper, aluminum, and iron. Other examples include water, air, and some non-metallic materials like graphite and diamond. In general, materials that are good conductors of electricity are also good conductors of heat.
In a conductor, heat transfer occurs through a process called conduction. This is when heat energy is transferred from one molecule to another through direct contact. When one end of a conductor is heated, the molecules in that end start to vibrate more, and this vibration is passed on to the neighboring molecules, causing them to also vibrate and transfer the heat energy along the material.
Yes, there are materials that are poor heat conductors, also known as insulators. These materials have low thermal conductivity and are not able to transfer heat easily. Examples of heat insulators include wood, plastic, rubber, and air. These materials are often used to prevent heat loss or transfer, such as in the insulation of buildings or in the handles of cooking utensils.