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The second law of thermodynamics is a physical law based on universal empirical observation concerning heat and energy interconversions.A simple statement of the law is that heat always flows spontaneously from hotter to colder regions of matter (or 'downhill' in terms of the temperature gradient).
Such spontaneous heat transfer always occurs from a region of high temperature to another region of lower temperature, as described in the second law of thermodynamics. Heat convection occurs when the bulk flow of a fluid (gas or liquid) carries its heat through the fluid. All convective processes also move heat partly by diffusion, as well.
A transport equation, usually of heat (sometimes of light element concentration): = + where T is temperature, = / is the thermal diffusivity with k thermal conductivity, heat capacity, and density, and is an optional heat source. Often the pressure is the dynamic pressure, with the hydrostatic pressure and centripetal potential removed.
A prime example of this irreversibility is the transfer of heat by conduction or radiation. It was known long before the discovery of the notion of entropy that when two bodies, initially of different temperatures, come into direct thermal connection, then heat immediately and spontaneously flows from the hotter body to the colder one.
“If you were going to the moon, you’d expect the journey to be uncomfortable but it’d be worth it,” she says. “You just have to think, ‘This is what I need to get from one world to ...
"The Moon dances with me the way the sun never will." —S.B. "The moon stared at me through sprinkled nighttime stardust and I alone smile." —Jay Long "The sun watches what I do, but the moon ...
Electrons are affected by two thermodynamic forces [from the charge, ∇(E F /e c) where E F is the Fermi level and e c is the electron charge and temperature gradient, ∇(1/T)] because they carry both charge and thermal energy, and thus electric current j e and heat flow q are described with the thermoelectric tensors (A ee, A et, A te, and A ...
Yalda Night, or Shab-e Yalda (also spelled Shabe Yalda), marks the longest night of the year in Iran and in many other Central Asian and Middle Eastern countries. On the winter solstice, in a ...