Methods of heating

The HR systems that are on the market may be divided into two groups  

Since an HR system essentially comprises two functional parts, the distributor with sprue bushing and the nozzles mixed systems can also be found, i.e., a distributor with external heating or nozzles with internal heating. 

1 - with heated nozzle 2 - with conducting nozzle - injection temperature Tgki - temperature fluctuations of plastic at nozzle with independent heating  

An HR system without heating (insulated) is rarely encountered nowadays although sometimes a combination of an unheated channel with a heated torpedo is found. 

Heating by conduction only occurs as part of a system, e.g., in the form of a heat-conducting nozzle. 

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It is believed that the red phosphorus is the true reducing agent and the iodine (or iodide) functions as a hydrogen carrier. This proc ure replaces the obsolete method of heating with red phosphorus and concentrated hydriodic acid in a sealed tube. 

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. 

Fig. 9. Methods of heating tanks (a) external heat exchanger (b) serpentine steam cods and (c) plate cods.

Commercial dryers differ fundamentally by the methods of heat transfer employed (see classification of diyers, Fig. 12-45). These industrial-diyer operations may utihze heat transfer by convection, conduction, radiation, or a combination of these. In each case, however, heat must flow to the outer surface and then into the interior of the solid. The single exception is dielectric and microwave diying, in which high-frequency electricity generates heat internally and produces a high temperature within the material and on its surface. 

When heat is transferred to a wet sohd by convection to hot surfaces and heat transfer by convection is negligible, the solids approach the boiling-point temperature rather than the wet-bulb temperature. This method of heat transfer is utilized in indirect diyers (see classification... 

Rotaiy diyers have been classified as direct, indirect-direct, indirect, and special types. The terms refer to the method of heat transfer, being direct wnen heat is added to or removed from the sohds by direct exchange between flowing gas and solids and being indirect when the heating medium is separated from physical contact with the solids by a metal wall or tube. 

Some of the most common methods of heat transfer with catalytic reaction will be briefly reviewed. 

For any method of heat transfer to take place, a temperature difference is necessary between two faces of a solid body, or at the boundaries of a gas or vapor. Flear transfer will take place only from a high-temperature source to a lower-temperature sink and is an irreversible process unless acted upon by another agency, as is the case with the refrigeration process. 

Many different methods of heating the air for industrial ventilation purposes are possible. 

The methods of heating TLC/HPTLC plates described above depend on thermal conduction, convection or radiation. Microwave heating involves a special form... 

In order to perform effectively as an insulant a material must restrict heat flow by any (and preferably) all three methods of heat transfer. Most insulating materials adequately reduce conduction and convection elements by the cellular structure of the material. The radiation component is decreased by absorption into the body of the insulant and is further reduced by the application of bright foil outer facing to the product. 

Method of heating and type or disposition of heaters Percentage addition for following heights of heated space (m) 5 5-10 >10 ... 

Abstract book of VIII Russian conference on optical methods of heating and high purity materials analysis, Gorikiy, 1988, p. 252. 

Various methods of heating are required in the analytical laboratory ranging from gas burners, electric hot plates and ovens to muffle furnaces. 

We note that different methods of heating are used by various researchers, as shown in Fig. 4.1. 

It is clear that many of the chemical metallurgy processes must be carried out at high temperatures. In this respect, it is necessary to be acquainted not only with the process reactors but also with the methods of heat generation and with the refractories that are needed in the reactors to cope up with the high temperatures attained. 

Do not use with heating pads or other methods of heat application because burning or blistering may occur. 

Linnhoff B and Hindmarsh E (1983) The Pinch Design Method of Heat Exchanger Networks, Chem Eng Sci, 38 745. 

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