Radiation-convection

The most widely used and best known resistance furnaces are iadirect-heat resistance furnaces or electric resistor furnaces. They are categorized by a combination of four factors batch or continuous protective atmosphere or air atmosphere method of heat transfer and operating temperature. The primary method of heat transfer ia an electric furnace is usually a function of the operating temperature range. The three methods of heat transfer are radiation, convection, and conduction. Radiation and convection apply to all of the furnaces described. Conductive heat transfer is limited to special types of furnaces. 

If heat is transferred solely by convection and in the absence of other heat effects, the surface temperature approaches the wet-bulb temperature. However, when heat is transferred by radiation, convection, or a combination of these and convection, the temperature at the saturated surface is between the wet-bulb temperature and the boiling point of water. Under these conditions, the rate of heat transfer is increased and a higher drying rate results. 

The subject of heat transfer refers to the process by which energy in the form of heat is exchanged between objects, or parts of the same object, at different temperatures. Heat is generally transferred by radiation, convection, or conduction, processes that may occur simultaneously. 

Thermal discomfort Discomfort experienced due to excessive heat loss or gain from or to the human body due to radiation, convection, conduction, evaporation, or air movement. 

Passive movement detection senses radiated heat, such as that from a human body. These units are also sensitive to heat emitted by radiator, convection heaters and direct sunlight, so careful siting is required. 

When the turbulence in the atmospheric boundary layer is maintained largely by buoyant production, the boundary layer is said to be in a convective state. The source of buoyancy is the upward heat flux originating from the ground heated by solar radiation. Convective turbulence is relatively vigorous and causes rapid vertical mixing in the atmospheric boundary layer. 

Steel, aluminum, concrete, and other materials that form part of a process or building frame are subject to structural failure when exposed to fire. Bare metal elements are particularly susceptible to damage. A structural member undergoes any combination of three basic types of stress compression, tension, and shear. The time to failure of the structural member will depend on the amount and type of heat flux (i.e., radiation, convection, or conduction), and the nature of the exposure (one-sided flame impingement, flame immersion, etc.). Cooling effects from suppression systems and effects of passive fire protection will reduce the impact. 

The heat transfer to the immersed tubes is by a combination of radiation, convection from gases flowing past the tube, and transfer from particles in the vicinity of the tube surface. 

P is the energy transmitted by the flame toward the surface of the fuel. This energy includes convection, conduction, and radiation. Convection and conduction will be positive inputs toward the fuel, but convection will vary depending on the temperature of the gases over the material at a specific location within the surface. 

Usually experimental methods are used to measure heat transfer. Basic transfer mechanisms commonly recognized are conduction and radiation. Convection is often used as a third classification. The convection classification is also used in the current work. 

From this energy balance we see that the temperature indicated by the thermometer is not the true gas temperature but some radiation-convection equilibrium temperature. Very large errors can result in temperature measurements if this energy balance is not properly taken into account. Radiation shields are frequently employed to alleviate this difficulty. 

For this edition examples and problems oriented toward numerical (computer-generated) solutions have been expanded for both steady state and transient conduction in Chapters 3 and 4. New convection correlations have been added in Chapters 5, 6, and 7, and summary tables have been provided for convenience of the reader. New examples have also been provided in the radiation, convection, and heat exchanger material and over 250 new problems have been added throughout the book. Over 200 of the previous problems have been restated so that they are new for student work. In addition, all problems have been reorganized to follow the sequence of chapter topics. A total of over 850 problems is provided. 

Thermal injuries to skin are assessed by measuring the amount of energy transferred to the skin by radiation, convection, and conduction. 

Practically all p3n ometric installations are designed as an aid in furnace or oven operation. Some of the factors which work difficulty in the regulation of furnaces, ovens, kilns, tanks, etc., are (1) Inconstancy of heat supply. (2) Variation of internal absorption or generation of heat. (3) Variation of heat lost by radiation, convection, etc. (4) Unsteady supply or composition of material to be heat treated. 

Standard scaling Keep some groups constant. Usually Froude number and mass burning rate are chosen which leads to distortions in radiation, convection, turbulence and fuel bed geometry. Basically one is just looking at a buoyant plume. 

In order to avoid geometrical difficulties an ideal model of the packed bed will be employed to evaluate the heat transfer through the particle. The methods by which heat can enter a particle from its inner side are radiation, convection from the gas stream, and conduction through point contacts and stagnant fillets, as indicated in Fig. 13-8. Heat is transferred Through the particle and leaves the other side by the same three mechanisms. The three processes are in series, and the whole will be designated as the series mechanism. Hence... 

It is possible, indeed desirable in some cases, to use combined heat transfer modes, e.g., convection and conduction, convection and radiation, convection and dielectric fields, etc., to reduce the need for increased gas flow that results in lower thermal efficiencies. Use of such combinations increases the capital costs, but these may be offset by reduced energy costs and enhanced product quality. No generalization can be made a priori without tests and economic evaluation. Finally, the heat input may be steady (continuous) or time-varying also, different heat transfer modes may be deployed simultaneously or consecutively depending on the individual application. In view of the significant increase in the number of design and operational parameters resulting from such complex operations, it is desirable to select the optimal conditions via a mathematical model. 

Owens, A. J., C. H. Hales, D. L. Filkin, C. Miller, J. M. Steed, and J. P. Jesson (1985). A coupled one-dimensional radiation-convective chemistry transport model of the atmosphere. 1. Model structure and steady-state perturbation calculations. J. Geophys. Res. 90, 2283-2311. 

The contribution of radiative heat transfer becomes significant at temperatures above 600°C. The radiative component of heat transfer is accounted for by linear addition to the conductive and convective heat transfer components. The interactive effects between radiation-conduction and radiation-convection are discussed elsewhere [23,24]. 

When using thermocouples to measure high temperatures, the measurements must be corrected for the errors due to radiation, convection, and wire conduction. Sato et al. [57] present a calculation procedure for making these corrections. Moffat [58] notes the general equations for estimating these types of errors ... 

Autoignition A process in which a material ignites without any apparent outside ignition source. In the process, the temperamre of the material is raised to its ignition temperature by heat transferred by radiation, convection, combustion, or some combination of all three. 

The statistical collection and representation of the weather conditions for a specified area during a specified time interval, usually decades, together with a description of the state of the external system or boundary conditions. The properties that characterize the climate are thermal (temperatures of the surface air, water, land, and ice), kinetic (wind and ocean currents, together with associated vertical motions and the motions of air masses, aqueous humidity, cloudiness and cloud water content, groundwater, lake lands, and water content of snow on land and sea ice), nd static (pressure and density of the atmosphere and ocean, composition of the dry ir, salinity of the oceans, and the geometric boundaries and physical constants of the system). These properties are interconnected by the various physical processes such as precipitation, evaporation, infrared radiation, convection, advection, and turbulence, climate change... 

Isotherms for steady one-dimensional heat flow through a plastic, due to a heat flow Q onto the surface area A, from either radiation, convection or conduction from a metal. 

Akron coating gun distributes powder onto an earthed carbon fiber tow radiation/ convection oven... 

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