ASHRAE 90304-2017 Design Guide for Dedicated Outdoor Air Systems.pdf

1、ASHRAE Design Guide forDedicatedOutdoorAirSystemsThis publication was supported by ASHRAE Research Project RP-1712 under the auspices ofTC 8.10, Mechanical Dehumidification Equipment and Heat Pipes. Updates and errata for this publication will be posted on the ASHRAE website at www.ashrae.org/public

2、ationupdates. ASHRAE Design Guide forDedicatedOutdoorAirSystemsAtlantaRP-1712ASHRAE Staff Special PublicationsMark S. Owen, Editor/Group Manager of Handbook and Special PublicationsCindy Sheffield Michaels, Managing EditorJames Madison Walker, Managing Editor of StandardsSarah Boyle, Assistant Edito

3、rLauren Ramsdell, Assistant EditorMichshell Phillips, Editorial CoordinatorPublishing ServicesDavid Soltis, Group Manager of Publishing ServicesJayne Jackson, Publication Traffic AdministratorPublisherW. Stephen ComstockISBN 978-1-939200-71-6 (paperback)ISBN 978-1-939200-72-3 (PDF) 2017 ASHRAE1791 T

4、ullie Circle, NEAtlanta, GA 30329www.ashrae.orgAll rights reservedCover design by Laura HaassASHRAE is a registered trademark in the U.S. Patent and Trademark Office, owned by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc.ASHRAE has compiled this publication with

5、 care, but ASHRAE has not investigated, and ASHRAE expressly disclaims any duty to investigate, any product, service, process, procedure, design, or the like that may be described herein. The appearance of any technical data or editorial material in this publi-cation does not constitute endorsement,

6、 warranty, or guaranty by ASHRAE of any product, service, process, procedure, design, or the like. ASHRAE does not warrant that the information in the publi-cation is free of errors, and ASHRAE does not necessarily agree with any statement or opinion in this publication. The entire risk of the use o

7、f any information in this publication is assumed by the user.No part of this book may be reproduced without permission in writing from ASHRAE, except by a reviewer who may quote brief passages or reproduce illustrations in a review with appropriate credit, nor may any part of this book be reproduced

8、, stored in a retrieval system, or transmitted in any way or by any meanselectronic, photocopying, recording, or otherwithout permission in writing from ASHRAE. Requests for permission should be submitted at www.ashrae.org/permissions._Library of Congress Cataloging-in-Publication DataLibrary of Con

9、gress Cataloging in Publication Control Number: 2017017812CONTENTSvPreface ixChapter 1: Introduction . . . . . . . . . . . . . . . . . . . . . . . . 1Definition 1Reasons for Using DOAS 2Applications 7Role of the Designer 7Chapter 2: Outdoor Air and Load Requirements . . . 9Introduction 9Outdoor Air

10、Requirements 10Outdoor Air Design Conditions 16Outdoor Air Loads 22Summary 27Chapter 3: System Selection . . . . . . . . . . . . . . . . . . . 29Introduction 29Common Approaches to Air Distribution 30DOAS Equipment Configurations 37System Selection Considerations 43Chapter 4: Detailed Design Conside

11、rations . . . . . . . 49Introduction 49Codes and Standards 50Air Distribution 52viDampers 57Dehumidification and Cooling 58Heating 59Air-to-Air Energy Recovery 62Energy Recovery Effectiveness 67Humidification 71Filtration/Air Cleaning 72Summary 76Chapter 5: Controls . . . . . . . . . . . . . . . . .

12、 . . . . . . . . . 77Introduction 77Control of the DOAS Unit 78Humidity Control 81Temperature Control 83Energy Recovery Control 89Frost Control 98Outdoor Airflow Control 100Building Pressurization Control 101Sensors and Instrumentation 102Building Automation 104Sequence of Operations 104Summary 104C

13、hapter 6: Construction . . . . . . . . . . . . . . . . . . . . . 107Introduction 107Construction Phase Process 108Summary 117Chapter 7: Operation and Maintenance. . . . . . . . . 119Introduction 119Documentation 120Operation and Maintenance of DOAS Equipment 121Case Study 123Summary 123viiAppendix A

14、:Sample DOAS Installation Checklist . . . . . . . . . . . 127Appendix B:Sample DOAS Operational Checklist. . . . . . . . . . . 135References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137PREFACEixPURPOSEThe purpose of this book is to help technical professionals design dedicat

15、ed outdoor air systems (DOAS) for commercial and institutional buildings. If you are interested mostly in residential or industrial buildings, this book may not meet all of your needs. Additionally, this book is focused on design considerations that are specifi-cally relevant to DOAS. It is not inte

16、nded to be a general guide for designing any HVAC system. Rather, its intent is to highlight issues that should be considered when incorporating DOAS into your overall HVAC design.ASSUMPTIONSWe assume the reader is an HVAC designer, although not necessarily one with an engineering degree, and has a

17、basic understanding of HVAC systems, ter-minology, psychrometry, and the common variables of equations used in design-ing HVAC systems.As an overall focus, we write for the system designer who “has to get it done by Friday.” We expect that the guide may also be useful to others, such as archi-tectur

18、al designers, building developers and owners, maintenance professionals, students, teachers, and researchers. However, where decisions have been made about technical depth and detail, we have tried to meet the needs of the HVAC designer first.ORGANIZATION OF THE GUIDEThis book has been organized int

19、o seven main chapters. Chapter 1 is designed to give the reader some background on DOAS as well as describe the primary motivations behind developing this Guide. Chapters 2 through 5 contain the core guidance for designing a successful DOAS. These chapters cover outdoor air and load requirements, sy

20、stem selection, detailed design considerations, and controls, xrespectively. Chapter 6 familiarizes the reader with items to consider during the con-struction process, and Chapter 7 focuses on DOAS operation and maintenance. Some of the topics covered in this book are relevant to more than one piece

21、 of the design process. Rather than reiterate the same information in multiple chapters, choices have been made regarding where to place these subjects. We have tried to organize the content in this book such that subjects are placed in the chapter most relevant to them, and the reader is referred t

22、o that section when that subject comes up again in other places. HOW TO USE THIS GUIDEReaders will get the most use out of this guide if they come to it with a clear understanding of the goals and requirements of the specific project they are working on. With these in mind, it will be easier to narr

23、ow down the types of systems and equipment configurations that would be most appropriate for their particular appli-cation. It is also important to remain aware of any specific climate considerations for the project in question.This book has been organized such that someone designing their first DOA

24、S could read the book from start to finish and receive DOAS-specific guidance for each step in the design. Readers who have already started their design or have previ-ous experience with DOAS should skip to the areas of the book that are relevant to their project or that present DOAS variations they

25、 might be less familiar with. We recommend that all readers pay some attention to controls, construction, and opera-tion, as these are the elements that can make the difference between a marginally functional DOAS and a fully optimized DOAS.ACKNOWLEDGMENTSThis work was made possible by the contribut

26、ions and assistance of many indi-viduals and organizations. We are particularly grateful to John Murphy and Lew Harriman for their encouragement and support throughout this enormous task. The entire project monitoring subcommittee (John Dieckmann, Chris Gray, Lew Harri-man, Scott McGinnis, John Murp

27、hy, and Paul Pieper) was instrumental in providing insightful guidance and feedback. Many of our best graphics were either borrowed from or inspired by existing ASHRAE publications, and we thank those authors for helping to pave the way. We are also deeply appreciative of all of the engineers, build

28、ing owners, building managers, and market stakeholders who took part in inter-views and/or showed us around their buildings as we prepared to write this guide.READER INPUTAs the use of DOAS becomes more common, the applied experience of our readers will also grow. This book should be thought of as a

29、 starting point for the dis-cussion on DOAS. We encourage any feedback or suggestions from our readers that xicould be used to improve this guide. Please send your recommendations to one of our authors at : Svein Morner, PhD, PE, CPMP, CPP, LEED AP, Member ASHRAEFounding Principal, Sustainable Engin

30、eering Group, Middleton, WIAmalia Hicks, PhD, LEED AP, Associate Member ASHRAESenior Associate, Cadmus Group, Madison, WIManus McDevitt, PE, CPMP, CPP, LEED AP, Member ASHRAEFounding Principal, Sustainable Engineering Group, Middleton, WIFigure 1.1 Changing seasons.George Hodan, The Four Seasons, 1C

31、HAPTER 1INTRODUCTIONDEFINITIONFor the purposes of this book, all material is based on the following definition of a dedicated outdoor air system (DOAS):A dedicated outdoor air system (DOAS) uses separate equipment to condi-tion all of the outdoor air brought into a building for ventilation and deliv

32、-ers it to each occupied space, either directly or in conjunction with local or 2CHAPTER 1: INTRODUCTIONcentral HVAC units serving those same spaces. The local or central HVAC units are used to maintain space temperature.As shown in Figure 1.1, outdoor air conditions can vary drastically from season

33、 to season, and even throughout the day. What doesnt change is that buildings need to be ventilated with fresh outdoor air. DOAS are designed to ensure that a building receives the required amount of outdoor air, delivered at conditions that ensure occupant comfortregardless of what the weather is d

34、oing outdoors.Why This Book Was WrittenThe use of DOAS has become increasingly popular throughout the world. How-ever, the early adoption of all new technologies and approaches is often fraught with challenges. Because of the current lack of DOAS exposure and experience, many DOAS designed and insta

35、lled today do not always take full advantage of all the benefits DOAS can offer. Often, they are designed to achieve only one or two of their many available functions. They may cool the air efficiently, but not dry it; they may dry the air, but not recover heat; or they may not vary outdoor airflow

36、in response to building occupancy, forgoing substantial energy savings. Some use overly simplified control strategies, improperly apply exhaust air energy recovery, and/or deliver conditioned outdoor air to the building in a manner that reduces or limits the benefits of decoupling ventilation from s

37、pace conditioning.This guide was developed to assist engineers in designing optimal DOAS. Although, over time, a sizable body of literature has accumulated pertaining to the design, installation, and operation of DOAS, it is widely scattered and time-con-suming to search out. Such searches are parti

38、cularly impractical for design engi-neers with pressing deadlines. In this book, we aim to consolidate much of the existing material into one volume, focusing on the overview and major issues while referring the reader to supplemental sources for more specialized or in-depth infor-mation.REASONS FOR

39、 USING DOASThere are many reasons to use DOAS. Some of the most common drivers are (1) improving humidity control, (2) reducing energy use, (3) the desire to simplify ven-tilation design and control, (4) the desire to use heating and cooling equipment that does not provide ventilation and/or dehumid

40、ification (e.g., radiant panels or passive chilled beams), and (5) reducing installation cost. Here is how these driving factors have encouraged a rise in DOAS installations over the last few decades.Humidity ControlIn many locations worldwide, for both residential and commercial buildings, mechanic

41、al ventilation is either a code requirement or an industry-standard prac-tice. With the introduction of outdoor air often comes an increase in dehumidifica-ASHRAE DESIGN GUIDE FOR DEDICATED OUTDOOR AIR SYSTEMS3tion loads. In fact, incoming ventilation and makeup air typically carries more than 80% o

42、f a buildings annual dehumidification load (ASHRAE 2015a, Chapter 62).Annual cumulative latent ventilation loads typically exceed sensible ventilation cooling loads by 3:1 to 5:1 in all but high-altitude and desert climates (Harriman et al. 1997). Figure 1.2 Annual cumulative latent (dehumidificatio

43、n) and sensible-cooling load from ventilation air.Harriman et al. (1997)Figure 1.2 shows the annual cumulative latent and sensible cooling and dehumidification load from ventilation for sample climates. In addition, the peak sensible-cooling conditions are typically not close to the peak latent load

44、 condi-tions, as is shown for a sample climate in Figure 1.3. Ventilation latent loads peak at more moderate temperatures, not necessarily the peak dry bulb condition. Tradi-tional system designs may be unequipped to handle such high latent loads (Kosar et al. 1998) over the wide range of ambient co

45、nditions. A dedicated dehumidification component, such as that typically included in a DOAS, can remove the ventilation latent load, often avoiding the need for the cooling equipment to cool the air too low for the sensible load to a temperature lower than required for the sensible load, thereby req

46、uiring the need to use extensive reheat.Figure 1.3 Design extremes. Harriman et al. (2000)4CHAPTER 1: INTRODUCTIONBecause of widespread adoption of light-emitting diode (LED) lighting and low solar heat gain coefficient windows, internal sensible-cooling loads have been greatly reduced while the ven

47、tilation load has not. The consequence of these tech-nology advancements is that, in many cases, separating the latent cooling from the majority of the sensible cooling with a DOAS may reduce the cost of the mechani-cal system (in particular, if using an energy recovery device in the DOAS) because o

48、f downsized sensible-cooling equipment, which can help pay for the cost of dehu-midification, cooling, heating, and filtering the ventilation air in the DOAS.Energy ImpactsThe goal of reducing energy consumption in buildings has had a much greater influence on design decisions in recent years. Due i

49、n part to this increased aware-ness of efficiency, DOAS has gained in popularity and is emerging as an effective, cost-efficient approach to reducing energy use. For example, one important way that DOAS contributes to energy savings is by removing humidity from the outdoor air, which allows the remaining cooling com-ponents to operate based solely on dry-bulb temperature. Dry ventilation air can eliminate or strictly limit the use of reheat energy as required by ANSI/ASHRAE/IES Standa