Metal Jacket Wall

In some cases, where the wall of the reactor has an appreciable thermal capacity, the dynamics of the wall can be of importance (Luyben, 1973). The simplest approach is to assume the whole wall material has a uniform temperature and therefore can be treated as a single lumped parameter system or, in effect, as a single well-stirred tank. The heat flow through the jacket wall is represented in 

The nomenclature is as follows Qm is the rate of heat transfer from the reactor to the reactor wall, Qj is the rate of heat transfer from the reactor wall to the jacket, and 

Um is the film heat transfer coefficient between the reactor and the reactor wall. Uj is the film heat transfer coefficient between the reactor wall and the jacket. Am is the area for heat transfer between the reactor and the wall. Aj is the area for heat transfer between the wall and the jacket. 

In some cases, it may be of interest to model the temperature distribution through the wall. 

This might be done by considering the metal wall and perhaps also the jacket as consisting of a series of separate regions of uniform temperature, as shown in Fig. 3.7. The balances for each region of metal wall and cooling water volume then become for any region, n 

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A thick-walled kettle of mass temperature T, and specific heat Cj, is filled with a perfectly mixed process liquid of mass M, temperature T, and specific heat C. A heating fluid at temperature Tj is circulated in a jacket around the kettle wall. The heat transfer coeffldent between the process fluid and the metal wall is U and between the metal outside wall and the heating fluid is Inside and outside heat transfer areas A are approximately the same. Neglecting any radial temperature gradients through the metal wall, show that the transfer function between T and T, is two first-order lags. 

Another modification includes replacing the outer glass vacuum jacket with a metal jacket. Evacuation is not necessary if the jacket is spaced about 2 cm from the walls of the mixing vessel since a time constant of about 1 h can be achieved by filling the jacket with argon at atmospheric pressure. 

For primary insulation or cable jackets, high production rates are achieved by extmding a tube of resin with a larger internal diameter than the base wke and a thicker wall than the final insulation. The tube is then drawn down to the desked size. An operating temperature of 315—400°C is preferred, depending on holdup time. The surface roughness caused by melt fracture determines the upper limit of production rates under specific extmsion conditions (76). Corrosion-resistant metals should be used for all parts of the extmsion equipment that come in contact with the molten polymer (77). 

Belt Typ es The patented metal-belt type (Fig. ll-53a), termed the water-bed conveyor, features a thin wall, a well-agitated fluid side for a thin water film (there are no rigid welded jackets to fail), a stainless-steel or Swedish-iron conveyor belt floated on the water... 

Fig. 5.4-23 shows a sketch drawing of a BSC (Brogli et al., 1981). The stirred-tank reactor made of glass (a metal version is also available) is surrounded by a jacket through which a heat-transfer fluid flows at a very high rate the jacket is not insulated. The temperature of the circulation loop is regulated by a cascaded controller so that the heat evolution in the reactor is equilibrated by heat transfer through the reactor wall. The temperature in the loop is adjusted by injection of thermostatted hot or cold fluid. 

The heat transfer area between the reactor and jacket is 140 The overall heat transfer coefficient is 70 Btu/h °F ft. Mass of the metal walls can be negleaed. Heal losses are negligible. 

Let us assume that an irreversible exothermic reaction A B takes place in a CSTR, as shown in Figure 1. The cooling jacket surrounding the reactor removes the reaction heat. Perfectly mixed and negligible heat losses are assumed. The jacket is assumed to be perfectly mixed and the mass of the metal walls is considered negligible. 

Jacket, Coolant. The metal enclosure that consists of an inner wall (liner) and an outer metal wall (outer case), with a coolant passage between them, occasionally held apart by spacers or coolant helices. Term also applied to the double metal walls of a regeneratively-cooled thrust-chamber assembly... 

Two runs at high CO2 concentrations (9.8 mole percent CO2/ N2/5A 1/4" and 13.2 mole percent C02/air/5A 1/8" LMS pellets), for which it was determined that effects of heat transfer could be very important, were run in a special column designed by F. W. Leavitt (developer of the MASC program) to simulate essentially adiabatic behavior. The column was constructed of thin-walled sheet metal and was 24.8 cm in diameter. Electric heating jackets placed in sections along the wall of the column and controlled by thermocouples placed at corresponding intervals along the centerline of the bed were used to maintain the wall at essentially the same temperature as the bed interior. 

There are three resistances/coefhcients that must be considered in a jacket-cooled CSTR. There is a film coefficient hin at the inside wall of the vessel, a thermal conductivity km of the metal walls and a him coefficient hout at the outside surface of the wall ... 

The equivalent diameter of the annular jacket geometry is the jacket clearance. If the wall thickness is 0.003 m and the thermal conductivity of the metal is 45 J s 1 K-1 m-2, the overall heat transfer coefficient for the circulating water system is U = 700 J s 1 K 1 m-2. 

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