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3、of this book be reproduced, stored in a retrieval system, or transmitted in any way or by any meanselectronic,photocopying, recording, or otherwithout permission in writing from ASHRAE._Library of Congress Cataloging-in-Publication DataSpitler, Jeffrey D.Load calculation applications manual / Jeffre
4、y D. Spitler.p. cm.Includes bibliographical references and index.Summary: “Focuses on the radiant time series and heat balance methods for calculating cooling loads in nonresidential buildings. The intended audience is relatively new engineers who are learning to do load calculations, as well as exp
5、erienced engineers who wish to learn the radiant time series method“-Pro-vided by publisher.ISBN 978-1-933742-42-7 (softcover)1. Air conditioning-Efficiency. 2. Cooling load-Measurement. 3. Heating load-Measurement. 4. Heating. I. Title.TH7687.5.S683 2008697-dc222008042693ASHRAE STAFFSPECIAL PUBLICA
6、TIONSChristina HelmsEditorCindy Sheffield MichaelsAssociate EditorJames Madison WalkerAssistant EditorAmelia SandersAssistant EditorMichshell PhillipsAdministrative AssistantPUBLISHING SERVICESDavid SoltisGroup ManagerTracy BeckerGraphic Applications SpecialistJayne JacksonPublication Traffic Admini
7、stratorPUBLISHERW. Stephen ComstockContentsForeword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIIChapter OneIntroduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8、 . . . . 1Chapter TwoFundamentals of Heat Transfer and Thermodynamics . . . . . . . . . . . . . . . . . . . . . . . . . 5Chapter ThreeThermal Property Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17Chapter FourEnvironmental Design Conditions . . . .
9、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67Chapter FiveInfiltration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81Chapter SixInternal Heat Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10、 . . . . . . . . . . . . . . . . 105Chapter SevenFundamentals of the Radiant Time Series Method . . . . . . . . . . . . . . . . . . . . . . . . . 127Chapter EightApplication of the RTSMDetailed Example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161Chapter NineAir Systems, Loads, IAQ,
11、and Psychrometrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201Chapter TenHeating Load Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225Chapter ElevenHeat Balance Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12、. . . . . . . . . . . . . 235Appendix APsychrometric ProcessesBasic Principles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245Appendix BSpreadsheet Implementation of the RTSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267Appendix CCalculation of CTSFs and RTFs . . .
13、. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297Appendix DSolar Radiation and Heat Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303Appendix ETreatment of Thermal Bridges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14、 . . . . . . 315Appendix FTreatment of Uncontrolled Spaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323Appendix GCorrection Factor for High-Conductance Surface Zones . . . . . . . . . . . . . . . . . . . . . 329Index. . . . . . . . . . . . . . . . . . . . . . . . . . .
15、 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333VIIForewordThis manual is the fourth in a series of load calculation manuals published by the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. The first in the series, Cooling and Heating Load
16、Calculation Manual, by William Rudoy and Joseph Cuba, was published in 1980. A second edition, by Faye McQuis-ton and myself, was published in 1992 and focused on new developments in the trans-fer function method and the cooling load temperature difference method. Subsequent to the second edition, A
17、SHRAE Technical Committee 4.1, Load Calculations Data and Procedures, commissioned additional research. This research led to the adapta-tion of the heat balance method for use in load calculation procedures and develop-ment of the radiant time series method (RTSM) as the recommended simplified proce
18、dure. Both methods were presented in the third volume of this seriesCooling and Heating Load Calculation Principles, by Curtis Pedersen, Daniel Fisher, Richard Liesen, and myself.The Load Calculation Applications Manual, also sponsored by TC 4.1, builds on the past three, and some parts are taken di
19、rectly from previous versions. New develop-ments in data and methods have led to numerous revisions. This manual, intended to be more applications-oriented, includes extensive step-by-step examples for the RTSM.This work, more so than many technical books, represents the work of many indi-viduals, i
20、ncluding:Authors of the previous three versions, who are named above.Numerous ASHRAE volunteers and ASHRAE researchers who have developedmaterial for the ASHRAE Handbook that has now been incorporated.Members of the Project Monitoring Subcommittee, including Chris Wilkins, SteveBruning, Larry Sun, a
21、nd Bob Doeffinger, who have provided extensive comments,guidance, and direction. My graduate student, Bereket Nigusse, who has developed most of the spreadsheetsunderlying the examples and whose PhD research has led to a number of develop-ments in the RTSM that are incorporated into this manual. The
22、 contributions of all of these individuals are gratefully acknowledged.Jeffrey D. Spitler11Introductionhis manual focuses on two methods for calculating cooling loads in non-residential buildingsthe heat balance method (HBM) and the radiant time series method (RTSM). The two methods presented are ba
23、sed on fundamental heat balance principles, directly so in the case of the HBM, and less directly so in the case of the RTSM. Both methods were first fully presented for use in design load calculations in the predecessor to this volume, Cooling and Heating Load Calculation Principles (Pedersen et al
24、. 1998). Since that time, there have been a number of developments in the RTSM. This publication attempts to bring the previous volume up to date, incorporate new developments, and provide a more in-depth treatment of the method. 1.1 Definition of a Cooling LoadWhen an HVAC system is operating, the
25、rate at which it removes heat from a space is the instantaneous heat extraction rate for that space. The concept of a design cooling load derives from the need to determine an HVAC system size that, under extreme conditions, will provide some specified condition within a space. The space served by a
26、n HVAC system commonly is referred to as a thermal zone or just a zone. Usually, the indoor boundary condition associated with a cooling load calculation is a constant interior dry-bulb temperature, but it could be a more complex function, such as a thermal comfort condition. What constitutes extrem
27、e conditions can be inter-preted in many ways. Generally, for an office it would be assumed to be a clear sunlit day with high outdoor wet-bulb and dry-bulb temperatures, high office occupancy, and a correspondingly high use of equipment and lights. Design conditions assumed for a cooling load deter
28、mination are subjective. But, after the design conditions are agreed upon, the design cooling load represents the maximumor peak heat extrac-tionrate under those conditions.1.2 The Basic Design QuestionsIn considering the problem of design from the HVAC system engineers view-point, there are three m
29、ain questions that a designer needs to address. They are: 1. What is the required equipment size? 2. How do the heating/cooling requirements vary spatially within the building? 3. What are the relative sizes of the various contributors to the heating/cooling load?The cooling load calculation is perf
30、ormed primarily to answer the second ques-tion, that is, to provide a basis for specifying the required airflow to individual spaces within the building. The calculation also is critical to professionally answering the first question. Answers to the third question help the designer make choices to i
31、mprove the performance or efficiency of the design and occasionally may influence architectural designers regarding energy-sensitive consequences.T2Load Calculation Applications Manual1.3 Overview of the ASHRAE Load Calculation Methods1.3.1 Models and RealityAll calculation procedures involve some k
32、ind of model, and all models are approximate. The amount of detail involved in a model depends on the purpose of that model. This is the reality of modeling, which should describe only the variables and parameters that are significant to the problem at hand. The challenge is to ensure that no signif
33、icant aspects of the process or device being modeled are excluded and, at the same time, that unnecessary detail is avoided.A complete, detailed model of all of the heat transfer processes occurring in a building would be very complex and would be impractical as a computational model, even today. Ho
34、wever, generally building physics researchers and practitioners agree that certain modeling simplifications are reasonable and appropriate under a broad range of situations. The most fundamental of these is that the air in the space can be modeled as well-stirred. This means there is an approximatel
35、y uniform temperature throughout the space due to mixing. This modeling assumption is quite valid over a wide range of conditions. With that as a basis, it is possible to formulate fundamental models for the various heat transfer and thermodynamic processes that occur. The resulting formulation is c
36、alled the HBM. There is an introduction to the general prin-ciples of the HBM in Chapter 2 and further description in Chapter 11.1.3.2 The Heat Balance MethodThe processes that make up the heat balance model can be visualized using the schematic shown in Figure 1.1. It consists of four distinct proc
37、esses:1. the outside face heat balance2. the wall conduction process3. the inside face heat balance4. the air heat balanceFigure 1.1 shows the heat balance process in detail for a single opaque surface. The shaded part of the figure is replicated for each of the surfaces enclosing the zone. The proc
38、ess for transparent surfaces would be similar to that shown but would not have the absorbed solar component at the outside surface. Instead, it would be split into two parts: an inward-flowing fraction and an outward-flowing fraction. These fractional parts would participate in the inside and outsid
39、e face heat balances. The transparent surfaces would, of course, provide the transmitted solar component that contributes to the inside heat balance. The double-ended arrows indicate schematically where there is a heat exchange, and the single-ended arrows indicate where the interaction is one way.
40、The formula-tion of the heat balance consists of mathematically describing the four major pro-cesses, shown as rounded blocks in the figure.1.3.3 The Radiant Time Series MethodThe RTSM is a relatively new method for performing design cooling load calcu-lations. It is derived directly from the HBM an
41、d effectively replaced all other simpli-fied (non-heat-balance) methods such as the transfer function method (TFM), the cooling load temperature difference/solar cooling load/cooling load factor method (CLTD/SCL/CLFM), and the total equivalent temperature difference/time averaging method (TETD/TAM).
42、 The RTSM was developed in response to a desire to offer a method that was rigorous yet did not require iterative calculations of the previous methods. In addition, the periodic response factors and radiant time factors have clear Introduction3physical meanings and, when plotted, allow the user to v
43、isually see the effects of damping and time delay on conduction heat gains and zone response. The utility of the RTSM lies in the clarity, not the simplicity, of the procedure. Although the RTSM uses a “reduced” heat balance procedure to generate the radi-ant time series (RTS) coefficients, it is ap
44、proximately as computationally intensive as the heat balance procedure upon which it is based. What the RTS method does offer is insight into the building physics without the computational rigor of the HBM, a sacrifice in accuracy that is surprisingly small in most cases. Previous sim-plified method
45、s relied on room transfer function coefficients that completely obscured the actual heat transfer processes they modeled. The heat-balance-based RTS coefficients, on the other hand, provide some insight into the relationship between zone construction and the time dependence of the building heat tran
46、sfer processes. The RTSM abstracts the building thermal response from the fundamen-tally rigorous heat balance and presents the effects of complex, interdependent physical processes in terms that are relatively easy to understand. The abstraction requires a number of simplifying assumptions and appr
47、oximations. These are cov-ered in Section 7.1. Figure 1.2 shows the computational procedure that defines the RTSM. A more detailed schematic is shown in Chapter 7.In the RTSM, a conductive heat gain for each surface is first calculated using air-to-air response factors. The conductive heat gains and
48、 the internal heat gains are then split into radiant and convective portions. All convective portions are instantaneously converted to cooling loads and summed to obtain the fraction of the total hourly cool-ing load due to convection.Radiant heat gains from conduction, internal sources, and solar t
49、ransmission are operated on by the RTS to determine the fraction of the heat gain that will be con-verted to a cooling load in current and subsequent hours. These fractional cooling loads are added to the previously calculated convective portions at the appropriate hour to obtain the total hourly cooling load.Figure 1.1 Schematic of heat balance process in a zone.4Load Calculation Applications Manual1.4 Organization of the ManualThis manual is organized to roughly proceed from the general to the specific. Chapter 2 provides an overvie
