Heating system

3 Heating Systems Over the years, three methods of heating the susceptor but not the tube walls have been used. For one, the susceptor can be made of an electrically conducting material (i.e., graphite) and used as a resistor with an electrical power supply. Joule heating will then heat it readily. 

Finally, heating can be done by irradiating the susceptor with high intensity lamps that will transmit readily through the fused quartz. 

The life of a container depends to a very appreciable extent on the type of heating employed. During the first decades rod and tube extrusion presses were mainly used for the working of heavy metals, for which it is necessary to heat the container to a temperature of 300 to 400 °C. Once in operation the container is warmed by the passage through it of 

A substantial improvement was obtained by mounting gas- or oil burners in the container-holder. The heating cycle could thus be sped up and controlled, having on the other hand the disadvantage that the heating of the container was not very uniform and that the hot gases escaping from the slits of the bore of the holder, obstructed the operation of the press. 

In order to render the heating system more efficient, the heat source was no longer placed in the container-holder, but in the jacket proper. 

The jacket heating is of the resistance- or induction type. In either case longitudinal holes to accommodate the heaters are drilled in the container jacket, as shown in Fig. 144. 

With the induction type of heating insulated copper rods are mounted 

Standard industrial heaters with water or oil have been used extensively with good result. Water-based heaters are available with or without pressurization. With pressurized systems, temperatures up to about 140°C are possible. With pressurized systems, however, special hoses and tubes are necessary, and this will increase the costs for the heating system significantly. 

The advantage of water versus oil is that the leakage of heater fluid that always occur during tool change will evaporate or can easily be wiped up with water, but it must be disposed of using absorbents with oil. 

Blanket-type electrical heaters are often used in combination with low thermal mass GRP tools (e.g., in the tooling concept advocated by Plastech TT, UK). The drawback with electrical heaters is that locally very high temperatures can occur. This can damage the tool and give an unacceptable variation in the curing process. 

When convective heating is used it is important to localize the heating channels on an appropriate distance from the tool surface. The part can be damaged by print-through if the distance between the surface and the channels is too small. The surface temperature may vary and give rise to unacceptable cure variations if the distance is too large. As a rule of thumb the distance to the surface in mass cast tools from aluminum-filled methacrylic resin should be 

C Model constant in Gebart s permeability model and in Equation 12.10 [dimensionless] Fmax Model constant in Gebart s permeability model [dimensionless] 

In chemical plants, in steam and gas turbine powered compressor and power stations and pressure control facilities for natural gas, combustible fluids and gases need to be preheated in order to comply with the process parameters, 

Lamp power rating 250 W Lamp type HIT-DE, HST-DE Rated luminous flux of lamps  

IP protection code IP 65 Diameter, max. 320 mm Height 325 mm Weight 25 kg Type of protection EEx de 11C T3 (terminal compartment in e ) Certificate INIEX 85.103.431 (former name ofISSeP)  

Lamp rating up to 1000 W for halogen lamps, up to 600 W for discharge lamps Lamp type QT, HME, HIT, HST IP protection code IP 67  

Flash energy 5 J Flashing rate 1 pulse per second Cyclic duration factor 100% Supply voltage 24/42/110/230/240 V AC 12/24/48/60/80 V DC Overall height 305 mm Protective cage diameter 75 mm Weight 1.3 kg Type of protection EEx d IICT6 Certificate PTB Ex-86.2028. 

There are several suitable energy sources to heat CVD reaction chambers which mainly include  

Material Density (g-cnC) Resistivity at 20°C Coefficient of thermal resistivity (°C) Melting temperature (°C) Max service temperature (°C) Service Environment 

ISA Type Positive Wire Negative Wire Service atmosphere Temperature range (°C) Tolerance 

B Pt70- Rh30 Pt94-Rli6 Inert or Slow oxidizing 200-1700 600-1700°C, 0.0025T 

K Chromel Ni90Crl 0 Alumel Ni95Mn2A12S il oxidizing 0-1100 0-333°C, 2.5°C 333-1100°C, 0.0075T 

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When an atom or molecule receives sufficient thermal energy to escape from a Hquid surface, it carries with it the heat of vaporization at the temperature at which evaporation took place. Condensation (return to the Hquid state accompanied by the release of the latent heat of vaporization) occurs upon contact with any surface that is at a temperature below the evaporation temperature. Condensation occurs preferentially at all poiats that are at temperatures below that of the evaporator, and the temperatures of the condenser areas iacrease until they approach the evaporator temperature. There is a tendency for isothermal operation and a high effective thermal conductance. The steam-heating system for a building is an example of this widely employed process. 

The alternative of lower cost r-f systems, ie, induction and r-f heating systems at 40 MH2 and below, should be considered (96) (see also Furnaces, electric). More extensive discussions of the economic aspects of microwave systems and payback calculations are available (97,98). 

M. J. Heim rich, S. Albu, and J. Osborne, Electrically Heated System Conversion on Two Current Technology Vehicles, SAE 910612, Society of Automotive Engineers, Warrendale, Pa., 1991. 

Tyj)e of heating system External External External External... 

Figure 27-37 shows the chief operating characteristics of a range of boilers, from small-scale heating systems to large-scale utility boilers. 

Utilities or municipal power systems supplying electric power and low-grade heat (e.g., 422 K [300°F]) for local distric t heating systems... 

Provide postventilation interlocks and/or operating procedures to keep fans running for a sufficient time after shutdown of heating system... 

Use external heating system with process recirculation... 

Figure 4-25. Nitric acid plant at Fredericia (Denmark) with a four-machine turbogroup and generator. Power output to district heating system = 0-27 MW Power output to electric grid = 0-5.8 MW Steam turbine = 10.8 MW Axial compressor = 8.2 MW Centrifugal compressor = 4.1 MW Expander = 7.4 MW Nitric acid production = 650 t/d.

Glass-reinforced grades have widely replaced metals in pumps and other functional parts in washing equipment and central heating systems. In the manufacture of business machine and computer housings structural foam materials have found some use. Mouldings weighing as much as 50 kg have been reported. 

By computing values from the above equations, a curve of T versus time may be plotted. This information may be used to design heating systems or evaluate the performance of existing ones. The input parameters required for the analysis are T, U, A, W, Cp, and T,. 

Legionella 0 Tt3 Legionnaire s Disease, commonly known as pneumonia Found naturally in water multiplies in heating systems... 

The energy balance from Equation 6-39 yields a heating system... 

The maximum or minimum temperature attainable in a vessel can be limited by properly designed jacket heating systems. If steam heating is used, maximum temperatures can be limited by controlling steam pressure. A steam desuperheater may be needed to avoid excessive temperature of superheated steam from a pressure letdown station. 

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