Reator de Agitação Aquecimento com Vapor Calculo de Comprimento e Vazão - Problema Resolvido

PROBLEM 519 KNOWN Volume density and specific heat of chemical in a stirred reactor Temperature and convection coefficient associated with saturated steam flowing through submerged coil Tube diameter and outer convection coefficient of coil Initial and final temperatures of chemical and time span of heating process FIND Required length of submerged tubing Minimum allowable steam flowrate SCHEMATIC ASSUMPTIONS 1 Constant properties 2 Negligible heat loss from vessel to surroundings 3 Chemical is isothermal 4 Negligible work due to stirring 5 Negligible thermal energy generation or absorption due to chemical reactions associated with the batch process 6 Negligible tube wall conduction resistance 7 Negligible kinetic energy potential energy and flow work changes for steam ANALYSIS Heating of the chemical can be treated as a transient lumped capacitance problem wherein heat transfer from the coil is balanced by the increase in thermal energy of the chemical Hence conservation of energy yields s h dU Vc dT UA T T dt dt ρ Integrating i T t s T o h UA dT dt T T ρVc s h h i UA t T T ln T T ρVc h s h i Vc T T A Ut ln T T ρ 1 1 1 1 1 2 o i U h h 110000 1 2000 W m K 2 U 1670W m K 3 3 2 s 2 1200kg m 225m 2200J kg K 500 450 A ln 137m 500 300 1670W m K 3600s 2 As 137m L 218m D 002m π π COMMENTS Eq 1 could also have been obtained by adapting Eq 55 to the conditions of this problem with T and h replaced by Th and U respectively