Scientific Basis of Air Conditioning

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3 Scientific Basis of Air Conditioning -Second Edition - by KEN-ICHI KIMURA Professor Emeritus of Architectural Science, Waseda University, Tokyo, Japan INTERNATIONAL RESEARCH INSTITUTE ON HUMAN ENVIRONMENT TOKOROZAWA, JAPAN

4 INTERNATIONAL RESEARCH INSTITUTE ON HUMAN ENVIRONMENT ISBN: Copyright Ken-ichi Kimura Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled GNU Free Documentation License. ii

5 Preface to the second edition This book was initially published by Applied Science Publishers, London in 1977 and ceased to be published in 1990s. As described in the Foreword to the Revised Edition written by Dr. S. Murakami, then Chief Executive of Building Research Institute (BRI), Japan, the revised edition with some modification in B5 size was used as the text for the international seminar under the sponsorship of Japan International Cooperation Agency (JAICA) held in Owing to the courtesy of JAICA and BRI, this book has been open to the public domain thereafter. Several years later the contract between JACA and BRI was terminated. Then, since the entire copyright was kept by the author, another revision work was made as requested by international audience and the second edition has been determined to be published by International Research Institute on Human Environment, Tokorozawa, Japan. The contents stay almost the same as the first edition, sticking to fundamentals in different subjects from solar radiation, various phases of heat transfer in buildings including heat from lights and stack effects to dynamic heat load calculation, simulation and computer control of air conditioning system. Although new trends have been attempted in these days, scientific basis would not change so much. Researchers and students in environmental science worldwide have used this book as a convenient reference for years. For practitioners when an unexperienced project comes in, they should not fail to refer to fundamentals for actual planning work in consultation of this book. It would be a great pleasure for the author that this book would be used hereafter as well as in the past without being obsolete too much. October 2016 Ken-ichi Kimura Professor Emeritus, Waseda University, Tokyo, Japan Principal, International Research Institute on Human Environment, Tokorozawa, Japan iii

6 Foreword to the Revised Edition This book was originally written by Professor Ken-ichi Kimura and published by Applied Science Publishers, London in 1977 as one of the Architectural Science Series edited by Late Professor Emeritus Henry J. Cowan, University of Sydney. Unfortunately the publisher decided to discontinue publication sometime in the 1990s and no more printing could not be envisaged ever since. According to the Agreement between Professor Kimura and Applied Science Publishers signed in 1974, the entire copyright of this book is now possessed by Professor Kimura. In spite of such an unfortunate situation, revised publication of this book has long been requested worldwide by academic staffs and building scientists, as this book has been used for a long time as an advanced text book in various universities and colleges as well as practicing engineers and scientists all over the world. In fact the fundamental theories described in this book have never become obsolete. Under such difficult circumstances, a new possibility of revival of this book has arisen. In 2009 Building Research Institute (BRI) initiated a new project of educating capable government officers of developing countries in Asia under the sponsorship of Japan International Cooperation Agency (JICA), a subsidiary organization of Ministry of International Trade and Industry. Two months course of seminar was projected for this purpose with a generous assistance by special authorities of architectural scientists. Then suitable text books written in English by Japanese scientists were sought for this course with the result that this book was selected. As the original edition is out of print, it was decided to have the whole book electronically scanned for the seminar text. Dr. Takao Sawachi of BRI, project manager of this international seminar requested Professor Kimura to create a revised edition of this book on this occasion. Professor Kimura agreed with his proposal to have it published by BRI and worked in making some corrections, modifications and additions for this revised editions. Without their valuable efforts this publication would not have been possible. It is hoped that this book will be widely in service again in the world for the effective use of energy in air conditioning as well as for the betterment of architectural environment in the future. August 2010 Shuzo Murakami Chief Executive, Building Research Institute, Tsukuba, Japan iv

7 Preface to the first edition This book is written as an advanced text for graduate students in architectural science, building science, building engineering, architectural engineering and mechanical engineering, as well as a reference book for practising air conditioning engineers. It deals with the scientific nature of air conditioning, from the basic theories to the applied technology as it is generally accepted today. The purpose of air conditioning is to create comfortable conditions in the building environment. However, air conditioning ought to be blamed as it consumes an excessive amount of primary energy. It is therefore important to learn both the scientific basis of air conditioning and the principles of energy conservation to ensure that air conditioning is designed in the most efficient manner. The performance of air conditioning depends on various parameters and it is related to many different aspects of science. For example, solar radiation incident on building surfaces and transmitted through windows has an important influence on the thermal environment of the occupied space, while the basic theories of solar radiation belong to physics and environmental science. Heat transfer is taught in the departments of mechanical engineering and chemical engineering; however, unsteady-state condition and non-linear heat transfer occur everywhere in a building and heat transfer in buildings entails somewhat different features from those governing heat transfer in mechanical systems. Heat conduction within the building structure, heat convection along the interior and exterior surfaces of building components, and radiation exchange between the surfaces of enclosed spaces may sometimes give rise to quite complicated problems. In the past, teachers of air conditioning have had to collect the information applicable to air conditioning practice from different fields of science and no systematic theory seems to have been established in the realm of air conditioning. On the other hand, it is often claimed that architects do not understand environmental problems, such as air conditioning, and this is accounted for by the insufficient teaching of its scientific basis in architecture schools. Looking at all the scientific aspects of air conditioning, it is quite difficult to organise them into a systematically routine course. The contents of this book are mainly focused on the thermal behavior of the environmental space. The first six chapters describe the basis for the heat load estimation of air conditioning, which is summarised in Chapter 7. Chapters 8 and 9 deal with engineering features and review the basic theories to be applied to engineering practice. Part of this book is derived from a volume written by myself in Japanese entitled Fundamental Theories of Building Services, and I am obliged to the publisher for permission to reproduce these articles. The manuscript of this book is v

8 not a direct translation from the articles in Japanese and later developments in various research results are, of course, included. After visiting Japan in 1972, Professor Henry J. Cowan suggested that I should write this book. Professor Cowan and his colleagues, Professor P. Smith and Dr Valerie Havyatt, were kind enough to review the first draft of the manuscript and to correct the English to a considerable extent. I would like to express my sincere thanks to them. I feel much indebted to Professor U. Inoue, Department of Architecture, Waseda University, for his advice and encouragement in writing this book and to Dr. D. G. Stephenson and Mr. G. P. Mitalas, Division of Building Research, National Research Council of Canada, for their kind guidance in the study, on which a considerable portion of this book is based, undertaken during my stay in Ottawa from 1967 to Without their valuable help this publication would not have been possible. Acknowledgements are also due to the ten graduate students in my laboratory at Waseda University for preparing the line drawings for the illustrations. Mrach 1977 KEN-ICHI KIMURA Waseda University, Japan vi

9 Contents Preface v Introduction 1 Chapter 1. Solar radiation Solar constant and solar spectrum Solar position Direct solar radiation Diffuse solar radiation Breaking-down of global radiation into direct and diffuse components Solar radiation on cloudy days 20 Chapter 2. Unsteady State Heat Conduction through Walls and Slabs Fundamental equation of unsteady state heat conduction Finite difference method Periodic steady heat conduction Indicial response Impulse response and convolution Solution by Laplace transformation Matrix expression of surface temperature and surface heat flow Response factors definition and usage Derivation of response factors Practical application of response factors Z-transform 57 Chapter 3. Radiative and Convective Heat Transfer in Buildings Film coefficient Radiative heat transfer coefficient Convective heat transfer coefficient Radiation from the atmosphere Heat balance at the Outside surface of buildings Determination of the convective heat transfer coefficient of an outside surface of a building by field experiment Radiation and convection heat exchange inside the room 81 Chapter 4. Solar Heat Gain from Windows Absorption, reflection and transmission of solar radiation for sheet glass Solar heat gain from glass windows of different orientation Experimental determination of cooling load associated with solar heat gain Cooling load weighting factors for solar heat gain Solar heat gain from windows with inside venetian binds Experimental determination of thermal characteristics of vii

10 venetian blinds Experimental determination of the effect of re-radiation from external shading Simplified calculation procedure of solar heat gain from glass windows with external shading using a weighting factor technique 117 Chapter 5. Effect on Air Conditioning of Heat from Lights Illumination level and heat generated by lights Integrated lighting-air conditioning system Experimental determination of heat removal efficiency of troffers with return air intake Theory of cooling load caused by lights Cooling load weighting factors for power input to lights 140 Chapter 6. Infiltration and Exfiltration Caused by Wind and Stack Effects Air leakage characteristics of openings and cracks Infiltration by wind Principle of stack effect Infiltration by stack effect Combination of wind and stack effects 156 Chapter 7. Heat Load of Air Conditioning Heat gain and cooling load Components of space cooling load Algorithm of calculating space cooling load Heat extraction and room air temperature variation Preconditioning load and Preconditioning period 173 Chapter 8. System Simulation of Air Conditioning System model of air conditioning Simulation of dual duct system An example of component simulation Part-load performance of air conditioning components Simulation of heat storage system Simulation of heat recovery system Simulation of solar heat collector Simulation of solar heating system 205 Chapter 9. Computer Control of Air Conditioning A system model for computer control of air conditioning Method of optimisation in the control Control of start and stop of air conditioning components Control of outside air intake Prediction control 215 References 221 Index 226 viii