Heat Transfer

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Heat transfer

Heat, a form of kinetic energy, is transferred in three ways: conduction, convection, and radiation. Heat transfer (also called thermal transfer) can occur only if a temperature difference exists, and then only in the direction of decreasing temperature. Beyond this, the mechanisms and laws governing each of these ways are quite different. See Conduction (heat), Convection (heat), Heat radiation

By utilizing a knowledge of the principles governing the three methods of heat transfer and by a proper selection and fabrication of materials, the designer attempts to obtain the required heat flow. This may involve the flow of large amounts of heat to some point in a process or the reduction in flow in others. All three methods operate in processes that are commonplace.

In industry, for example, it is generally desired to extract heat from one fluid stream and add it to another. Devices used for this purpose have passages for each of the two streams separated by a heat-exchange surface in the form of plates or tubes and are known as heat exchangers. The automobile radiator, the hot-water heater, the steam or hot-water radiator in a house, the steam boiler, the condenser and evaporator on the household refrigerator or air conditioner, and even the ordinary cooking utensils in everyday use are all heat exchangers. See Heat

Heat transfer

A generic term for thermal conduction, convection, and radiation.

Heat Transfer

 

the spontaneous irreversible movement of heat in space owing to a nonuniform temperature field. In the general case, heat transfer may also result from the nonuniformity of the fields of other physical quantities; an example is a difference in concentrations. Heat is transferred in three ways: conduction, convection, and radiation. In practice, heat transfer usually occurs through all three mechanisms at the same time.

Heat transfer determines or accompanies many processes in daily life, in technology, and in nature—for example, meteorological processes at the earth’s surface and the evolution of stars and planets. In many cases, such as in the study of dehydration, evaporative cooling, and diffusion, heat transfer is considered together with mass transfer. A special case of heat transfer is the flow of heat from one heat-transfer fluid to another through a solid wall separating the fluids or through an interface between the fluids.

heat transfer

[′hēt ¦tranz·fər]
(thermodynamics)
The movement of heat from one body to another (gas, liquid, solid, or combinations thereof) by means of radiation, convection, or conduction.

Heat transfer

Heat, a form of kinetic energy, is transferred in three ways: conduction, convection, and radiation. Heat transfer (also called thermal transfer) can occur only if a temperature difference exists, and then only in the direction of decreasing temperature. Beyond this, the mechanisms and laws governing each of these ways are quite different. See Conduction (heat), Convection (heat)

By utilizing a knowledge of the principles governing the three methods of heat transfer and by a proper selection and fabrication of materials, the designer attempts to obtain the required heat flow. This may involve the flow of large amounts of heat to some point in a process or the reduction in flow in others. All three methods operate in processes that are commonplace.

In industry, for example, it is generally desired to extract heat from one fluid stream and add it to another. Devices used for this purpose have passages for each of the two streams separated by a heat-exchange surface in the form of plates or tubes and are known as heat exchangers. The automobile radiator, the hot-water heater, the steam or hot-water radiator in a house, the steam boiler, the condenser and evaporator on the household refrigerator or air conditioner, and even the ordinary cooking utensils in everyday use are all heat exchangers. See Heat exchanger

heat transfer

The flow of heat from one body at higher temperature to another body at a lower temperature, until the two temperatures are equal.
References in periodicals archive ?
Enhancement of pool boiling heat transfer in a horizontal water layer through surface roughness and screen coverage, Heat and Mass Transfer 32(1-2): 17-26.
The majority of the research in nanofluids for heat transfer applications has been around boiling heat transfer.
Nucleate pool boiling heat transfer characteristics of refrigerant/oil mixtures on metal foam covers were experimentally investigated at a wide range of oil concentrations.
Chen, A correlation for boiling heat transfer to boiling fluids in convective flow.
Nanotube and nanowire arrays are another effective way to enhance pool boiling heat transfer.
Electric Field Effects on Pool Boiling Heat Transfer experiments from the University of Maryland and University of Pisa, Italy; Jungho Kim and Paolo DiMarco, co-PIs.
The convective boiling heat transfer correlation is given by Ming-huei Yu et al.
1976, A Comprehensive Model for Nucleate Boiling Heat Transfer Including Microlayer Evaporation.
Topics include micro and meso scale compact heat exchangers in electronics thermal management, high temperature heat exchangers, design considerations for compact ceramic offset strip-fin high temperature heat exchanges, compact heat exchangers for microturbines, R134a flow boiling heat transfer in small diameter tubes, entrace and wall conduction efforts in parallel flow heat exchangers, effects of flow channel variations due to manufacturing and fouling on hear exchanger performance, aspects of two-phase flow distribution at the header-channels assembly, and power spectra and Strouhal number distributions for turbulent full-developed flows in rectangular ducts with spatially-periodic plate inserts.
Unfortunately, there is no information available in the open literature on flow boiling heat transfer of [CO.
Although these two correlations are well known and often used to predict pool boiling heat transfer coefficients, care is required to define the constants associated with each correlation.