Nozzles pressure drop, heat exchanger

Nozzles. minimum area of flow 1M. pressure drop, heat exchanger 528... 

Calculate the pressure drop for the water flowing through the air-cooled heat exchanger designed in Example 7.37 if the number of tube-side passes is 10. The density of the water is 60 lb/ft3 (961.1 kg/ m3), and the viscosity is 0.74 lb/(ft)(h) (0.31 cP). Assume that the velocity in the nozzles is 10 ft/s (3.05 m/s) and that the viscosity change with temperature is negligible. 

Chapter 7, Reactor Design, discusses continuous and batch stirred-tank reactors and die packed-bed catalytic reactor, which are frequently used. Heat exchangers for stirred-tank reactors described are the simple jacket, simple jacket with a spiral baffle, simple jacket with agitation nozzles, partial pipe-coil jacket, dimple jacket, and the internal pipe coil. The amount of heat removed or added determines what jacket is selected. Other topics discussed are jacket pressure drop and mechanical considerations. Chapter 7 also describes methods for removing or adding heat in packed-bed catalytic reactors. Also considered are flow distribution methods to approach plug flow in packed beds. 

Disc- and doughnut-type heat exchangers for gases have lesser pressure drops and do not have idle gas pockets (which may occur in conventional shell- and tube-type heat exchangers with segmental baffles), and the orientations of inlet and exit nozzles for the process streams can he made to suit the ducts (routes of gas duct can also be shortened which is helpful to reduce the pressure drops) without generally affecting plant performance. 

Major pressure drops occur in forcing the plastie melt through the injection nozzle and hence through the mold feed system and cavities. These pressure losses cannot be quantified by simple rules. They are a fime-tion of the physical form of the flow path, the condition of the plastic melts, the rate of heat exchange, the type of polymer, and the rate and pressure of injeetion. Specific figures can be calculated with adequate aeeu-racy by computer simulations of the molding process. 

Friction factor values are normally plotted as a function of the Reynolds number and can be obtained from manufacturers for their various fin geometries. Proprietary methods for determining the pressure drop in inlet and exit nozzles, distributors, and headers can also be obtained from these vendors. Table 5.4 provides examples of heat transfer and corresponding pressure drop correlations for three typical fin configurations used in plate-fin exchangers. 

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