Numerical Models for Condenser and Evaporator Components of Fuel Cells
Numerical Models for Condenser and Evaporator Components of Fuel Cells

Author:

Publisher:

Published: 2002

Total Pages: 0

ISBN-13:

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The objective of this project was to develop analytical models and computer programs for the design and analysis of evaporator and condenser components of modern fuel cells. Mechanistic models were developed for boiling and two-phase flow phenomena in Microchannel-based boilers. The modeled systems included straight Microchannel with known inlet/exit boundary conditions; helicoidally micro-channels with known inlet/exit boundary conditions; straight, parallel micro-channels connected to common inlet and exit plena; and straight, parallel micro-channels connected to common inlet and exit manifolds. Models were also developed for fog formation/droplet growth resulting from the depressurization of a vapor-non-condensable mixture in an expander, and for droplet removal due to droplet-wall impaction when the aforementioned vapor-non-condensable-droplet mixture flows through a cyclone-type separator. Based on these models, computer programs suitable for design and analysis applications were developed.

A Computational Model of Steam Surface Condenser Performance
A Computational Model of Steam Surface Condenser Performance

Author: Richard Edward Pearce

Publisher:

Published: 2005

Total Pages: 442

ISBN-13:

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The objective of this project was to provide a useful computational tool for assessing the impact of condenser modifications on power operating cost, condenser modification capital cost, condenser pressure and heat rate (Btu/k W-H). To achieve this, a methodology was developed to evaluate the economics of condenser modification based upon design and economic information as well as actual operating date. A numerical model of condenser performance was also developed based upon the ASME resistance method and the Heat Exchanger Institute factorial/resistance model. The ASME resistance method was applied twice: once, using Nusselt's shell side natural convection heat transfer coefficient and second, using Rose's shell side heat transfer coefficient correlation for forced convection. The station L Unit 2 condenser bundle replacement and the station M Unit 2 condenser tube replacement projects were analyzed as test cases to validate the computational model. Since condenser performance has a direct impact upon fuel costs, heat rate and power production, this computational model can be used to assess the economic impact of a proposed condenser improvement. This computational model will also facilitate the study of the effects of condenser tube cleanliness upon condenser performance, thus allowing for efficient scheduling of tube maintenance.

Evaporator Performance Investigation for Residential Air-conditioning Application Using Mixed Refrigerants
Evaporator Performance Investigation for Residential Air-conditioning Application Using Mixed Refrigerants

Author: Maciej Chwalowski

Publisher:

Published: 1991

Total Pages: 146

ISBN-13:

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The design of the heat exchanger utilizing nonazeotropic refrigerant in an air conditioning application presents unique problems due to the phase change of the moist air and the variable specific heat of the evaporating refrigerant mixture. This study discusses the performance analysis and the design procedure of a cross counterflow heat exchanger working as an evaporator in an experimental system which simulated a residential air conditioning application. The design of the heat exchanger, used for the experimental testing, consisted of several depth rows. Separated banks permitted the determination of the sensible and the latent heat loads for each bank and the heat profiles across the heat exchanger. The interaction between the refrigerant mixture and the moist air was quantified by determining the temperature profiles of both media and the moisture removal rate. The overall heat transfer coefficient for each bank of the heat exchanger was determined from the measured quantities. The effect of the change of the mixture composition on heat exchanger performance was evaluated. The focus of the theoretical study was the development of the effectiveness/NTU (epsilon/NTU) relationships with the use of the experimentally derived quantities for moist air flowing across the heat exchanger. For moist air, the variable mixture specific heat, air and heat profiles obtained from the experimental results were utilized to obtain the expression for epsilon/NTU. The derived epsilon/NTU relations were verified and found to be in good agreement with dry and moist air test results. This study resulted an understanding of an application of a refrigerant mixture working fluid in an evaporator and provided tools to design such a heat exchanger.

Numerical Analysis of Two Phase Flow and Heat Transfer in Condensers
Numerical Analysis of Two Phase Flow and Heat Transfer in Condensers

Author: Pooya Mirzabeygi

Publisher:

Published: 2014

Total Pages: 228

ISBN-13:

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Steam surface condensers are commonly used in the power generation industry and their performance significantly affects the efficiency of the power plant. Therefore, it is vital to acquire a better understanding of the complex phenomena occurring inside condensers. A general three-dimensional numerical model is developed in this study to simulate the two-phase flow and heat transfer inside full-scale industrial condensers with irregular tube bundle shapes. The Eulerian-Eulerian two-phase model is selected to simulate gas and liquid flows and the interaction between them. A porous media approach is adopted to model the presence of large number of tubes in the condenser. The effect of the turbulence on the primary phase is accounted for by solving the transport equations for turbulent kinetic energy and dissipation rate. Various types of turbulence models are evaluated to select the best model for the condenser analysis. Also, the modified k- and RNG k- models are proposed to model the flow and heat transfer in condensers by adding the corresponding terms to the transport equations of the turbulence model to account for the effects of the tube bundle and condensate droplets on the primary phase turbulence, momentum and heat transfer. The proposed model provides excellent match with the experimental data and a significant improvement over the previous models. Furthermore, the proposed numerical model is coupled with a novel swarm intelligence multi-objective optimization algorithm to evaluate the performance of the new design candidates and introduce a set of condenser designs based on various input parameters and objective functions.

Evaporators
Evaporators

Author: American Institute of Chemical Engineers. Equipment Testing Procedures Committee

Publisher:

Published: 1979

Total Pages: 48

ISBN-13:

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Effect of Uneven Cooling on Performance of Air-Cooled Condenser
Effect of Uneven Cooling on Performance of Air-Cooled Condenser

Author: Hans Georg Schrey

Publisher: GRIN Verlag

Published: 2018-04-04

Total Pages: 27

ISBN-13: 366867616X

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Scientific Essay from the year 2017 in the subject Physics - Thermodynamics, , course: Heat transfer engineering, language: English, abstract: Air-cooled condensers (“ACC”) operating in vacuum are widely used at the cold end of contemporary thermal power plants. Proper functioning of the condenser is paramount for power plant efficiency. To adapt to changing process conditions because of changed ambient air temperature or power station load ACC streets are either taken out of or into service or, module fan speed settings are selected appropriately. Even if all fans are running at same speed local variations of cooling air flow may arise as a consequence of e.g. fan location or local wind impact. The designer must ensure that no negative effect (i.e. no cold spot) may evolve at the steam side of the ACC caused by uneven air side cooling or fan control. The following note describes a theoretical method to assess the effect of air flow variations on ACC performance and provides simple rules to avoid potentially risky situations. An important role for safe operation plays the size of the secondary condenser. The procedure may be used as a guideline for proper sizing of the secondary condenser with respect to airflow maldistribution.

Evaporating, Condensing and Cooling Apparatus
Evaporating, Condensing and Cooling Apparatus

Author: Eugen Hausbrand

Publisher: Legare Street Press

Published: 2023-07-18

Total Pages: 0

ISBN-13: 9781022854277

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This book provides a comprehensive guide to the design and operation of cooling and heating systems. With in-depth explanations, formulae, and tables of practical use, it is an essential resource for engineers, technicians, and students in the field. Whether you are working on a large-scale industrial project or a small residential installation, this book will help you optimize your system for maximum efficiency and cost-effectiveness. This work has been selected by scholars as being culturally important, and is part of the knowledge base of civilization as we know it. This work is in the "public domain in the United States of America, and possibly other nations. Within the United States, you may freely copy and distribute this work, as no entity (individual or corporate) has a copyright on the body of the work. Scholars believe, and we concur, that this work is important enough to be preserved, reproduced, and made generally available to the public. We appreciate your support of the preservation process, and thank you for being an important part of keeping this knowledge alive and relevant.