Florencio Sanchez Silva

Dispersed bubble flow in horizontal pipes

Abstract A set of experiments has been performed to analyse gas-phase distribution in horizontal bubble flow. The experimental data have been obtained by means of conductance probes and include measurements of the local void fraction and the bubble diameter and velocity. Present observations show large variations of the local void fraction and the bubble size moving from the top to the bottom of the pipe, with local maxima located close to the upper pipe wall. Measurements also show that, at the boundary of the dispersed bubble flow regime, the bubble size, and therefore the surface available for heat and mass transfer, changes abruptly for small variations of the liquid or gas flowrate. This change allows the transition between the dispersed and the elongated bubble regimes to be identified with good precision. Present data make it possible to develop a new correlation for the maximum bubble size in dispersed bubble flow.

CARACTERIZACIÓN EXPERIMENTAL DE UNA SUPERFICIE EXTENDIDA CON ALETAS TIPO ESPINA Y CONFIGURACIÓN DE TUBOS EN V INVERTIDA

The heat transfer and pressure drop results of an extended surface with spine-type fins and inverted V tube arrangement, are presented in this paper. The extended surface is composed of an aluminum tube and a ribbon with cuts, of the same material, that forms spine-type fins when the tube is rolled. The tube forms a coil with an inverted V type array of tubes according to the direction of the air flow. The experimental characterization of the surface was performed in a wind tunnel for an air flow velocity from 0.5 to 5 m / s for a constant flow of hot water with a temperature of 40 °C circulating inside the coil. Based on the experimental results, the correlations for the calculation of heat transfer and pressure drop on the extended surface with spine type fins and the arrangement of inverted V tubes were obtained. Heat transfer results were compared with those presented by other authors who have tested extended surfaces with spine type fins but with an in line array of tubes. It was found that the extended surface with spine type fins and inverted V type array of tubes showed a greater intensity in the heat transfer process by forced convection at flow speeds lower than 1 m / s. Key Words: extended surface, spine-type fins, inverted V tube array, heat transfer, pressure drop.

ANÁLISIS DEL COMPORTAMIENTO TÉRMICO EN LA PLANTA TERMOELÉCTRICA VALLE DE MÉXICO MEDIANTE PRUEBAS DE EVALUACIÓN EN TURBINAS DE GAS

RESUMEN: Las pruebas de evaluacion en turbinas de gas permiten determinar el comportamiento termico de los ciclos termodinamicos con los que opera el paquete 4 de la CTVM. El cual esta constituido por una unidad de vapor de 300 MW y ha sido repotenciado con tres unidades de gas de 83 MW. En su conjunto generan hasta 550 MW a una capacidad maxima. En este trabajo se utiliza el diseno de la tecnologia de turbinas de gas GT11N2 ALSTOM. A partir de los datos reales de operacion a una carga regulada, se realiza un analisis termodinamico aplicando la metodologia de ciclo real turbina de gas. Y se hace una comparacion con los datos de diseno mediante el uso de la herramienta GTPRO de termoflow 23.0 Se calcula la eficiencia termica de la turbina de vapor de alta, media y baja presion; eficiencia isoentropica de las turbinas de gas y compresores. Asi como la eficiencia termica del ciclo convencional, ciclo combinado, ciclo hibrido y ciclo abierto. Parametros que permiten determinar el estado actual de las unidades para una nueva disposicion de repotenciacion. Palabras clave: repotenciacion, turbina de gas, turbina de vapor, planta termoelectrica, eficiencia.