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 ?
* Hot and cold water pipes should be laid a sufficient distance apart to prevent temperature transfer.
Since the mold is clamped directly on the magnetic clamping plate on the full surface, without any isolating T-slots, temperature transfer is very homogeneous and not subject to variations.
A relationship can be drawn between heat and temperature transfer in regard to the quantity and the concentration of the fluid.
The cycler also utilizes ultra-thin walled (UTW) vessels for better temperature transfer, which enables protocols to be completed more quickly.
Researchers at NASA Langley Research Center, Hampton, VA, in a joint effort with Ube America Inc., NY, NY, AON Explorer, Ottawa, Ontario, and M&P Technologies, Marietta, Georgia, have developed PETI-330, High Temperature Transfer Molding Resin, a high temperature resin designed for RI, RTM, and VARTM.
These uncertainty components consist of the uncertainty of the temperature transfer standard (1.2 mK), uniformity of the temperature bath (1 mK), calibration fit residuals (10 mK), manufacturer-specified drift limit (10 mK), heat transfer effects attributed to self heating, stem conduction, and radiation (5 mK), spatial sampling error (50 mK), and the temperature adjustment to account for the moving gas stagnating against the probe (1 mK).
Under normal circumstances, only a small portion of the patient's back was in contact with the mattress, minimizing temperature transfer, and if the front of the patient was exposed to provide access for the surgeon, what heat was transferred to the patient was lost through the exposed area.
When the pads are mounted on substrates or at heat sink junctions, thermal impedance can be virtually eliminated, yielding higher temperature transfer gradients.
The final conditions to obtain the specific melting curve were 95[degrees]C for 20 s, 72[degrees]C for 25 s, 70[degrees]C for 25 s, 50[degrees]C for 0 s, and 95[degrees]C for 0 s [with a temperature-transfer speed of 0.5[degrees]C/s in each step, except the first step (20[degrees]C/s) and the last step, in which the speed of temperature transfer was 0.4[degrees]C/s].
Vacuum processing in these same vessels can provide additional efficiencies in temperature transfer from jacket to batch.
Temperature transfer treatments consisted of moving three pots from the 18 to the 26[degrees]C growth chamber and three pots from the 26 to the 18[degrees]C growth chamber at 418, and 12 d after seedling emergence.

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