1、I n t er n a tio n al J o u rn al of Heating ,Ventila t i n g , Air-conditioning and Refrigerating Research RESEARCH Volume 3, Number 4, October 1997 STDmASHRAE SRCH IJHVAC 3-4-ENGL 1777 H 0757b50 0529b88 72T International Journal of Heating, Ventilating, Air-Conditioning and Refrigerating Research
2、Editor Raymond Cohen, Ph.D., P.E., Professor of Mechanical Engineering and Herrick Professor of Engineering, Purdue University, U.S.A. Associate Editors Arthur E. Bergles, Ph.D., P.E., John A. Clark and Edward T. Crossan Professor of Engineering Emeritus, Department of Mechanical Engineering, Aerona
3、utical Engineering and Mechanics, Rensselaer Polytechnic Institute, U.S.A. Science, University of Oxford, United Kingdom Fire Research Laboratory, National Institute of Standards and Technology, U.S.A. Arthur L. Dexter, D.Phil., C.Eng., Reader in Engineering Science, Department of Engineering David
4、A. Didion, D.Eng., P.E., Leader, Thermal Machinery Group, Building and Ralph Goldman, Ph.D., Senior Consultant, Arthur D. Little, Inc., U.S.A. Hugo Hens, Drh., Professor, Department of Civil Engineering, Laboratory of Building Physics, Katholieke Universiteit, Belgium Ken-Ichi Kimura, Dr. Eng., Prof
5、essor, Department of Architecture, Waseda University and President, Society of Heating, Air-conditioning and Sanitary Engineers of Japan, Japan Universitt Hannover, Germany Universit de Lige, Belgium University of Wisconsin-Madison, U.S.A. University of California, Santa Barbara, U.S.A. Horst Kruse,
6、 Dr.-Ing., Professor, Institut fr Kltetechnik und Angewandte Wrmetechnik, Jean J. Lebrun, Ph.D., Professor, Laboratoire de Thermodynamique, John W. Mitchell, Ph.D., P.E., Professor, Mechanical Engineering, Dale E. Seborg, Ph.D., Professor, Chemical Engineering, Policy Committee William J. Coad, chai
7、r Hans O. Spauschus Fritz W. Steimle Raymond Cohen Frank M. Coda W. Stephen Comstock Publisher W. Stephen Comstock Robert A. Parsons, Handbook Editor Scott A. Zeh, Publishing Services Manager Nancy F. Thysell, Typographer Jenny Otlet-Jakovljevic ASHRAE Staff Editorial Assistant 01997 by the American
8、 Society of Heating, Refrigerating and Air-Con- ditioning Engineers. Inc., 1791 Tullie Circle, Atlanta, Georgia 30329. All rights reserved. Periodicals postage paid at Atlanta, Georgia. and additional mailing offices. HVACLR Reseorch (ISSN 1078-9669) is published quarterly as a peer- reviewed archiv
9、al research journal for the R nor may any pan of this book be reproduced, stored in a remeval system, or transmitted in any form or by any means-electronic, photocopying. recording, or other-without permission in writing from ASHRAE. Absirad.5-Abstracted and indexed by Engineering Information, Inc.
10、Available electronically on Compendex Plus and in print in Engineer- ing Index. Disclaimer-ASHRAEhas compiled this publication with care, but ASHRAE has not investigated, and ASHRAE expressly disclaims any duty to investigate, any product service, process. procedure, design. or the like which may be
11、 described herein. The appearance of any techni- cal data or editorial material in this publication does not constitute endorsement, warranty, or guaranty by ASHRAE of any product, ser- vice, process, procedure. design. or the lie. ASHRAE does no1 warrant that the information in this publication is
12、free of errors. and ASHRAE does not necessarily agrcc with any statement or opinion in this publica- tion. The entire risk of the use of any information in this publication is assumed by the um. Postmnser-Send form 3579 to: HVACENGL L797 E 0757b50 0529b70 388 310 HVAC however, this makes up only 5%
13、of the program. In the current research program, there are approximately 100 active projects. Large efforts are being devoted to indoor air quality (IAQ), refrigerants and refrigeration topics, and other issues of continuing importance such as energy conservation. For example, projects are underway
14、to research operation and maintenance practices that affect IAQ in office buildings, determine how to use living microorganisms to scrub unwanted volatile organic compounds from building air- streams, determine how to treat air filters to get rid of unwanted microorganisms, determine water solubilit
15、y of refrigerant blends, develop corrosion data on new refrigerant and lubricant mixtures, and determine the effect of oil on heat transfer in flooded evaporators using new refrigerants. Research projects such as these will pay great dividends in the years to come, just as others have done in the pa
16、st. ASHRAE has always devoted great efforts to disseminate technical information and the results of research to its membership. Starting at the beginning in 1895, we have continually published the ASHRAE Transactions from both our annual and semi-annual meetings. In the early 1920s, the ASHVE Guide
17、was developed to include the latest and best design procedures and data for our members. That book has now evolved into our four-volume ASHRAE Hand- book. The Society also publishes the monthly ASHRAE Journal, numerous special publications, and proceedings of every specialty conference that we hold.
18、 ASHRAE took another great step forward in 1994 with the decision to publish this, the Inter- national Journal of HVAC whereas, the actual value of q is probably slightly smaller because the interface between the desiccant and air is not a smooth surface (see Appendix A for further discussion). A va
19、lue of q = 0.05 is estimated for the molecular sieve coating investigated here. This means that 5% of the energy of phase change is assumed to be delivered directly to the air. In Appendix A, the value of q for various applications of heat and mass transfer theory is discussed, the development of Eq
20、uation (3) is pre- sented and it is suggested that more research is necessary to obtain a more accurate value of q. The conservation of mass in the air results in two continuity equations, one for the dry air and one for the water vapor. These equations include storage, convection and phase change.
21、The equations are: and The conservation of mass for the matrix is: where u is the mass fraction of water (vapor or liquid) in the desiccant (i.e. mass of water per mass of dry desiccant). To complete the formulation of the problem, several thermodynamic relations are needed. They are as follows: Pg
22、= Pa+Pv 2 500 800 - 2 307( T- 273.15) hfg = ha, = h*hjg = l+(h*,-1) ( 1- 4m)y h fg where Wm is the maximum moisture capacity of the desiccant, h describes the shape of heat of sorption as a function of moisture content, and 332 HVACl x=o =TI x=L =O (49) It should be noted that the initial conditions
23、 for the problem are not critical because the desired solution is the quasi-steady-state solution for an energy wheel rotating at constant speed with constant inlet conditions for both the hot and cold air flows. NUMERICAL SCHEME The governing equations were discretized using the using the finite vo
24、lume method with a staggered grid (Patankar 1980). The upwind difference scheme was used in the air because heat conduction and moisture diffusion are negligible. Central differencing was used in the matrix because there is no air flow. All the dependent variables and properties were solved at the n
25、odes and the velocity solved at the faces. The transient terms were solved using the implicit formula- tion. The numerical solution scheme is fully implicit for all of the coupled dependent variables in that the most updated value is used in each algebraic equation. The property values and source te
26、rms were treated in a semi-implicit manner because they were updated at the end of each itera- tion, and kept constant during the next iteration. The discretized equations (see Appendix C) were solved using a Gauss-Seidel iteration technique with under relaxation. The energy equation in the matrix w
27、as solved using the Tridiagonal Matrix Algorithm. The algorithm used to solve the coupled heat and moisture transfer problem is as follows: 1. Estimate the rate of phase change and the properties needed in the governing equations. 2. Solve the T,pv, U, u, and Tg fields in order with Equations (C7),
28、(C17), (C13), (C22), and (Ci), respectively (i.e. differential Equations (2), (5), (6), (7), and (l), respectively). 3. Update the property information with Equations (8) through (21) and (3 1). 4. Update the rate of phase change (riz) using Equation (22). 5. Return to step 2 and iterate until a converged solution is reached. 6. Increment time, return to step 2 and iterate until a quasi-steady solution is obtained.
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