Heat systems

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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