Power Plant Cooling Technologies

By Mir Akbar Hessami

Hybrid cooling systems could potentially save water. Water shortage is a major problem facing the power industry in many nations around the world. The largest consumer of water in most power plants is the wet cooling tower. To assist water and energy saving for thermal power stations using conventional evaporative wet cooling towers, a novel hybrid cooling system is investigated in this book.
Research on cooling systems to date has focussed on the individual components of cooling systems, not the system as a whole. Most of this research has been dedicated to cooling tower design and the optimisation of cooling tower characteristics. The issue of conserving water due to evaporation from existing operations has not been highly considered in the past. The major drawback in most of the previously conducted research in this field is the gap between maintaining energy efficiency whilst trying to reduce water consumption.
A hybrid cooling system consisting of a metal hydride heat pump and an existing cooling tower is described in this book. In addition to water saving, the hybrid cooling concept presented in this book also has the potential to improve energy efficiency and possibly reduce CO2 emission by recovering and upgrading the “waste” energy from the cooling water stream. This is therefore a win-win technology, producing both water and energy savings of significant quantities.

• Language: English
• Publisher: Mir Akbar Hessami
• Release date: May 2, 2011
• ISBN: 9781458173782

Mir Akbar Hessami

Dr. Mir-Akbar Hessami received his BSc in Mechanical Engineering in 1976 from Kabul University, Afghanistan before going to North America. He completed his MSc/MEng degree in 1979 at the University of Hawaii, USA and his PhD in 1983 at the University of Calgary, Canada. He moved to Australia in 1983, and started working in the School of Mechanical and Manufacturing Engineering at the University of New South Wales. He then worked for BHP Research and Technology Centre between 1985 and 1987 before taking up an academic position at the Victoria University in 1987. In 1991, he started working at Monash University as a Senior Lecturer in the area of Energy Conversion and Heat Transfer. His research specialty in the mainstream engineering field is in the area of energy technology production, utilisation and conservation. Dr. Hessami has written many journal and conference papers on this topic. His recent research project has dealt with the performance of compact heat exchangers with specific focus on cross-corrugated plate heat exchangers. He is currently working on an experimental study of heat transfer enhancement in pipes caused by fluid pulsation. Dr. Hessami's area of teaching is in Heat Transfer, Thermodynamics, and Refrigeration and Air-conditioning. He has authored a textbook entitled Applied Thermodynamics: Power Production from Conventional and Renewable Sources.

Book preview

Power plant cooling technologies

Hybrid cooling systems can save water

Authors:

Ferdi Yilmaz, Deakin University, Geelong

Mir-Akbar Hessami, Monash University, Clayton

Abbas Kouzani, Deakin University, Geelong

Eric Hu, The University of Adelaide, Adelaide

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COPYRIGHT

Power plant cooling technologies

Publication date February 2011.

Copyright © 2011

Ferdi Yilmaz, Mir-Akbar Hessami, Abbas Kouzani and Eric Hu (the authors) have asserted their right under the Copyright Act 1968 to be identified as the authors of this work.

All rights reserved. Without limiting the rights under copyright reserved above, no part of this publication may be reproduced, stored in or introduced into a retrieval system, or transmitted, in any form, or by any means (electronic, mechanical, photocopying, recording, or otherwise) without the prior written permission of both the copyright owner and the above publisher of this book.

Photographs and images are the copyright of the authors unless otherwise identified.

ISBN 978-1-4581-7378-2

Synopsis

Hybrid cooling systems could potentially save water…

Water shortage is a major problem facing the power industry in many nations around the world. The largest consumer of water in most power plants is the wet cooling tower. To assist water and energy saving for thermal power stations using conventional evaporative wet cooling towers, a novel hybrid cooling system is investigated in this book.

Research on cooling systems to date has focussed on the individual components of cooling systems, not the system as a whole. Most of this research has been dedicated to cooling tower design and the optimisation of cooling tower characteristics. The issue of conserving water due to evaporation from existing operations has not been highly considered in the past. The major drawback in most of the previously conducted research in this field is the gap between maintaining energy efficiency whilst trying to reduce water consumption.

A hybrid cooling system consisting of a metal hydride heat pump and an existing cooling tower is described in this book. In addition to water saving, the hybrid cooling concept presented in this book also has the potential to improve energy efficiency and possibly reduce CO2 emission by recovering and upgrading the waste energy from the cooling water stream. This is therefore a win-win technology, producing both water and energy savings of significant quantities.

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CONTENTS

Preface

List of symbols

List of abbreviations

Acknowledgements

Chapter 1: introduction

Chapter 2: power plant cooling systems

Chapter 3: mathematical model of cooling towers

Chapter 4: metal hydride heat pumps

Chapter 5: conclusions

References

Authors’ biographies

Preface

The material presented in this book is based on the results of a joint research project undertaken at both Deakin University (Geelong) and Monash University (Clayton). Most of the content of this book is derived from a MEng thesis submitted by the first author to Deakin University.

The book starts with a general introduction to power generation in Chapter 1 and it highlights the need for an efficient cooling system which can reduce water losses in conventional power plant cooling towers. In Chapter 2, conventional cooling systems employing dry and wet cooling towers are described, and the existing methods used to reduce water losses are explained. The concept of a hybrid cooling system and its potential to reduce water consumption is introduced. A mathematical description of conventional dry and wet cooling towers is provided in Chapter 3 which also includes a comparison between the simulation results and actual data obtained from local power plants. Chapter 4 is dedicated to the full description of the hybrid cooling system which is the main focus of this study. It is illustrated that this novel cooling system is based on the use of a metal hydride heat pump which can be used to pre-cool the water before it enters the cooling tower. It includes a detailed mathematical model of the processes involved with the heat pump component, and a comparison of the results obtained from the model with such data from the open literature. The effect of this pre-cooling process is shown to be a reduction in the evaporation rate of water as it flows through the tower. The findings of this research are summarised in Chapter 5.

Water shortage is a major problem facing the power industry in many nations around the world. The largest consumer of water in most power plants is the wet cooling tower. To assist water and energy saving for thermal power stations using conventional evaporative wet cooling towers, a novel hybrid cooling system is investigated in this book. Hybrid cooling systems may consist of all or some of an air pre-cooler, a heat pump, heat exchangers, and adsorption chillers together with the existing cooling tower. The hybrid cooling system described in this book, consisting of a metal hydride heat pump operating in conjunction with the existing wet cooling tower, is capable of achieving water saving by reducing the temperature of warm water entering the cooling tower. Cooler inlet water temperatures effectively reduce the cooling load on existing towers. This will ultimately reduce the amount of water lost to the air by evaporation whilst still achieving the same cooling output. At the same time, the low grade waste energy upgraded by the metal hydride heat pump, in the process of cooling the water, can be used to replace the bled-off steam for the lower stage feed heaters which will increase overall cycle efficiency.

The book is expected to be of interest to:

(a) engineering students who study power generation and related technologies used in the cooling of the working fluid,

(b) practicing engineers who are employed in the power industry, and

(c) academics and researchers who work in this area of engineering.

The material presented herein is written in a self-explanatory style and it does not require a high level of understanding and knowledge of thermodynamics and/or engineering practice. If more in depth knowledge in this area of engineering technology and research is required, the extensive list of references at the end of the book can be consulted.

Mir-Akbar Hessami

November 2010, Melbourne, Australia

List of Symbols

Roman symbols

A Area m2

C_p Specific heat capacity J/kg K

COP Co-efficient of performance dimensionless

D Diameter mm, m

F Correction factor dimensionless

h Specific enthalpy kJ/kg

H Height m

∆H Heat of formation kJ/kmolH2

H_2 Hydrogen dimensionless

k Thermal conductivity W/m K

L Length m

m ̇ Mass