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As a heating technology, Joule heating has a coefficient of performance of 1.0, meaning that every joule of electrical energy supplied produces one joule of heat. In contrast, a heat pump can have a coefficient of more than 1.0 since it moves additional thermal energy from the environment to the heated item.
The law holds well for forced air and pumped liquid cooling, where the fluid velocity does not rise with increasing temperature difference. Newton's law is most closely obeyed in purely conduction-type cooling. However, the heat transfer coefficient is a function of the temperature difference in natural convective (buoyancy driven) heat transfer.
The cooling produced in the Joule–Thomson expansion makes it a valuable tool in refrigeration. [ 8 ] [ 20 ] The effect is applied in the Linde technique as a standard process in the petrochemical industry , where the cooling effect is used to liquefy gases , and in many cryogenic applications (e.g. for the production of liquid oxygen ...
Between 1840 and 1843, Joule carefully studied the heat produced by an electric current. From this study, he developed Joule's laws of heating, the first of which is commonly referred to as the Joule effect. Joule's first law expresses the relationship between heat generated in a conductor and current flow, resistance, and time. [1]
The laws of thermodynamics are a set of scientific laws which define a group of physical quantities, such as temperature, energy, and entropy, that characterize thermodynamic systems in thermodynamic equilibrium.
Energy may be transferred into a system by heating, compression, or addition of matter, and extracted from a system by cooling, expansion, or extraction of matter. In mechanics , for example, energy transfer equals the product of the force applied to a body and the resulting displacement.
For real gasses, the molecules do interact via attraction or repulsion depending on temperature and pressure, and heating or cooling does occur. This is known as the Joule–Thomson effect. For reference, the Joule–Thomson coefficient μ JT for air at room temperature and sea level is 0.22 °C/bar. [7]
The middle term is the Joule heating, and the last term includes both Peltier (at junction) and Thomson (in thermal gradient) effects. Combined with the Seebeck equation for J {\displaystyle \mathbf {J} } , this can be used to solve for the steady-state voltage and temperature profiles in a complicated system.