Publication: Diseño y simulación de torres de refrigeración húmedas
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2013-10
Defense date
2013-10-30
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Abstract
El proyecto fin de carrera aborda el proceso de diseño y simulación de torres de
refrigeración húmedas, planteando la falta de exactitud y rigurosidad de los métodos
generalizados de cálculo de la transferencia de calor y masa.
La problemática relativa a la representación de la transferencia de calor y masa se
resuelve mediante la aplicación del método de Poppe, que calcula la transferencia de
calor y masa sin llevar a cabo las suposiciones críticas utilizadas por los métodos
tradicionales (método de Merkel y método ε-NTU) para simplificar el cálculo. Estas
suposiciones críticas consisten en considerar el factor de Lewis igual a la unidad,
considerar el aire a la salida de la torre saturado y caracterizado únicamente por su
entalpía y despreciar el caudal de agua evaporado en el balance energético.
Aplicando el método de Poppe se obtienen resultados con mayor grado de precisión,
solventado el principal problema de los métodos de Merkel y ε-NTU, la correcta
caracterización del aire a la salida de la torre de refrigeración.
Una vez resuelto el problema de transferencia, se analiza el diseño y simulación de
torres de refrigeración húmedas desde un punto de vista teórico y práctico. Se describen
los elementos que forman la torre, los parámetros de diseño, las consideraciones de
operación y las herramientas comúnmente utilizadas en el proceso de diseño y
simulación, con el objetivo de analizar el proceso de cálculo del performance o
funcionamiento de una torre de refrigeración.
Finalmente, se implementa el conocimiento desarrollado sobre el performance y la
transferencia de calor y masa en aplicaciones en Matlab, para asistir al proceso de
diseño y simulación de torres de refrigeración húmedas.
The Project looks into the design and simulation of the wet cooling tower taking into account the inaccuracy carried out by the most commonly used methods to calculate the mass and heat transfer. The issue regarding the heat and mass transfer is solved by the implementation of the Poppe method, which calculates the heat and mass transfer without making the critical assumption used in traditional methods (Merkel method and ε-NTU method) to simplify the calculation. The simplifying assumptions of the Merkel theory are; assumption l, the Lewis factor is equal to one; assumption 2, the air exiting the cooling tower is saturated with water vapor and it is characterized only by its enthalpy; assumption 3, the reduction of water flow rate by evaporation is neglected in the energy balance. More precise results are achieved by the implementation of Poppe method and the main issue of the Merkel and ε-NTU method, the correct characterization of the exit air, is solved. Once the heat and mass transfer issue is solved, the project analyzes the wet cooling tower design and simulation from a theoretical and practical point of view. The tower components, the design parameters, the performance considerations and the general tools used to design and simulate the towers are described in order to analyze the performance calculation of the wet cooling towers. Finally, the project develops some applications created in Matlab, based on the performance information to support the design and simulation process of wet cooling towers.
The Project looks into the design and simulation of the wet cooling tower taking into account the inaccuracy carried out by the most commonly used methods to calculate the mass and heat transfer. The issue regarding the heat and mass transfer is solved by the implementation of the Poppe method, which calculates the heat and mass transfer without making the critical assumption used in traditional methods (Merkel method and ε-NTU method) to simplify the calculation. The simplifying assumptions of the Merkel theory are; assumption l, the Lewis factor is equal to one; assumption 2, the air exiting the cooling tower is saturated with water vapor and it is characterized only by its enthalpy; assumption 3, the reduction of water flow rate by evaporation is neglected in the energy balance. More precise results are achieved by the implementation of Poppe method and the main issue of the Merkel and ε-NTU method, the correct characterization of the exit air, is solved. Once the heat and mass transfer issue is solved, the project analyzes the wet cooling tower design and simulation from a theoretical and practical point of view. The tower components, the design parameters, the performance considerations and the general tools used to design and simulate the towers are described in order to analyze the performance calculation of the wet cooling towers. Finally, the project develops some applications created in Matlab, based on the performance information to support the design and simulation process of wet cooling towers.
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Keywords
Refrigeración, Transferencia de calor, Torres de refrigeración, Método de Poppe, Método de Merkel