Heat source

1 Heat source Fuels used Heat transfer 1 Heat-saving appliances Charging system Mode of operation Draught Shape Purpose Charge handling 

Combustion/ Solid fuel-fired furnaces Fuel in direct contact Recuperative Manual and Batch, periodic Natural/self, Crucible, shaft Melting roasting Shaft, muffle 

Fuels are of three types solid, liquid, and gaseous. Each category has been further classified into natural, manufactured, or by-product. Natural fuels are called primary fuels, while artificially produced fuels for a purpose or market, together with the products which are unavoidable by-product of some regular manufacturing process, are called secondary fuels. The main raw materials for secondary fuel are generally primary fuels. A list of the important fuels is shown in Table 1.22. 

Some general comments may be made of some of the different types of fuels. The use of coal has been on the decline, and there has been an increase in petroleum and natural gas 

Solid Anthracite coal bituminous coal lignite peat wood Coke charcoal petroleum coke breeze semi-coke (low-temperature coal distillate) pulverized coal 

5 BIOLOGICAL UNITS NEED HEAT SOURCES AND SINKS 

The reward of a thing well done is to have done it. 

What a dreadful hot weather we have It keeps one in a continued state of inelegance. 

The sun is the ultimate heat source for most BU. The sun bathes the Earth in an average of MOON m/(s m ), which is a lot of energy. Some of this is absorbed in the atmosphere, some is reflected, and some is absorbed by plants to drive the chemical conversion of carbon dioxide into organic sugars. Much of the sun s energy is used to maintain the Earth at a temperature necessary for life. 

The coating material in the form of powder is metered into a compressed-gas stream and fed into the heat source where it is heated to its melting point and projected onto the substrate. Refractory carbides and nitrides have very high melting points and, at these temperatures, they are extremely reactive and must be sprayed in an inert atmosphere to avoid detrimental chemical reactions such as oxidation. 

The properties of thermal-sprayed coatings vary as a function of processing parameters such as temperature and particle velocity. Generally, such coatings have greater porosity than CVD or PVD coatings and thickness control is more difficult to achieve. 

Because of the refractory nature of carbides and nitrides, equipment capable of providing high temperatures is required. These include  

It operates at high pressure (10 MPa) and high particle velocity (-315 m/s) 

Detonation gun (D-gun) which uses the energy of continuous, controlled explosions of oxyacetylene mixtures to obtain the necessary kinetic energy. 

Plasma spray using a dc-plasma torch or aRF inductively coupled torch. 

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The analysis of the heat exchanger network first identifies sources of heat (termed hot streams) and sinks (termed cold streams) from the material and energy balance. Consider first a very simple problem with just one hot stream (heat source) and one cold stream (heat sink). The initial temperature (termed supply temperature), final temperature (termed target temperature), and enthalpy change of both streams are given in Table 6.1. 

Fig. 6.7a. Above the pinch (in temperature terms), the process is in heat balance with the minimum hot utility Qnmin- Heat is received from hot utility, and no heat is rejected. The process acts as a heat sink. Below the pinch (in temperature terms), the process is in heat balance with the minimum cold utility Qcmin- No heat is received, but heat is rejected to cold utility. The process acts as a heat source.

The point of zero heat flow in the grand composite curve in Fig. 6.24 is the pinch. The open jaws at the top and bottom represent Hmin and Qcmin, respectively. Thus the heat sink above the pinch and heat source below the pinch can be identified as shown in Fig. 

Fundamentally, there are two possible ways to integrate a heat engine exhaust. In Fig. 6.31 the process is represented as a heat sink and heat source separated hy the pinch. Integration of the heat engine across the pinch as shown in Fig. 6.31a is coimterproductive. The process still requires QHmm, and the heat engine performs no... 

In this context, the points correspond to process and utility streams and the lines to heat exchange matches between the heat sources and heat sinks. 

Figure 13.3 shows a process represented simply as a heat sink and heat source divided hy the pinch. Figure 13.3a shows the process with an exothermic reactor integrated above the pinch. The minimum hot utility can be reduced by the heat released by reaction, Qreact-... 

By comparison, Fig. 13.36 shows an exothermic reactor integrated below the pinch. Although heat is being recovered, it is being recovered into part of the process which is a heat source. The hot utility requirement cannot be reduced because the process above the pinch needs at least Q//m-,n to satisfy its enthalpy imbalance. 

Fig. 14.1a. The background process (which does not include the reboiler and condenser) is represented simply as a heat sink and heat source divided by the pinch. Heat Qreb is taken into the reboiler above pinch temperature and rejected from the condenser at a lower temperature, which is in this case below pinch temperature. Because the process sink above the pinch requires at least Q min to satisfy its...

Generai principies, representative appiications, fluctuations and irreversibie thermodynamics. Chapter 4 discusses quasistatic processes, reversibie work and heat sources, and thermodynamic engines. 

Because almost all alpha radiation is stopped within the solid source and its container, giving up its energy, polonium has attracted attention for uses as a lightweight heat source for thermoelectric power in space satellites. 

Sometimes, in FD, the emitter electrode is heated gently either directly by an electrode current or indirectly by a radiant heat source to aid desorption of ions from its surface. 

The various heating methods produce a vapor that is a mixture of gas, very small droplets, and small particles of solid matter (particulates). Before droplets or particulates can coalesce, the whole vapor is swept into the plasma flame for analysis. Clearly, the closer the heating source is... 

Solidification. The heat of the electric arc melts a portion of the base metal and any added filler metal. The force of the arc produces localized flows within the weld pools, thus providing a stirring effect, which mixes the filler metal and that portion of the melted base metal into a fairly homogeneous weld metal. There is a very rapid transfer of heat away from the weld to the adjacent, low temperature base metal, and solidification begins nearly instantaneously as the welding heat source moves past a given location. 

The third characteristic of interest grows directly from the first, ie, the high thermal conductance of the heat pipe can make possible the physical separation of the heat source and the heat consumer (heat sink). Heat pipes >100 m in length have been constmcted and shown to behave predictably (3). Separation of source and sink is especially important in those appHcations in which chemical incompatibilities exist. For example, it may be necessary to inject heat into a reaction vessel. The lowest cost source of heat may be combustion of hydrocarbon fuels. However, contact with an open flame or with the combustion products might jeopardize the desired reaction process. In such a case it might be feasible to carry heat from the flame through the wall of the reaction vessel by use of a heat pipe. 

The vessel, as weU as the wick, must be compatible with the working fluid. Where possible, the wick and vessel are made of the same material to avoid the formation of galvanic corrosion ceUs in which the working fluid can serve as the electrolyte. In addition to its role within the heat pipe, the vessel also serves as the interface with the heat source and the heat sink. 

There is assumed to be no interaction between the superfluid and normal components, thus the superfluid component can diffuse very rapidly to a heat source where it absorbs energy by reverting to the normal state. It thereby produces the very high effective thermal conductivity observed in helium II. 

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