Experimental Verification of a Standard Test Procedure for Solar Collectors

9 AlllDD TTbEn NATL INST OF STANDARDS & TECH R.I.C. A1 11 0099621 Hill, James Edward/Experimental verlfica TA435 .U58 V117;1979 C.I NBS-PUB-C 1979 i|35 .U58 NO. 117 1979 C.2 NBS BUILDING SCIENCE SERIES 117 Experimental Verification of a Standard Test Procedure for Solar Collectors U.S. DEPARTMENT OF COMMERCE • NATIONAL BUREAU OF STANDARDS * »• rrrTTJT.T. TT tttt 1 m~ v I NATIONAL BUREAU OF STANDARDS The National Bureau of Standards' was established by an act of Congress March 3, 1901. The Bureau's overall goal is to strengthen and advance the Nation's science and technology and facilitate their effective application for public benefit. To this end, the Bureau conducts research and provides: (1) a basis for the Nation's physical measurement system, (2) scientific and technological services for industry and government, (3) a technical basis for equity in trade, and (4) technical services to promote public safety. The Bureau's technical work is performed by the National Measurement Laboratory, the National Engineering Laboratory, and the Institute for Computer Sciences and Technology. THE NATIONAL MEASUREMENT LABORATORY provides the national system of physical and chemical and materials measurement; coordinates the system with measurement systems of other nations and furnishes essential services leading to accurate and uniform physical and chemical measurement throughout the Nation's scientific community, industry, and commerce; conducts materials research leading to improved methods of measurement, standards, and data on the properties of materials needed by industry, commerce, educational institutions, and Government; provides advisory and research services to other Government Agencies; develops, produces, and distributes Standard Reference Materials; and provides calibration services. The Laboratory consists of the following centers: Absolute Physical Quantities' — Radiation Research — Thermodynamics and Molecular Science — Analytical Chemistry — Materials Science. THE NATIONAL ENGINEERING LABORATORY provides technology and technical services to users in the public and private sectors to address national needs and to solve national problems in the public interest; conducts research in engineering and applied science in support of objectives in these efforts; builds and maintains competence in the necessary disciplines required to carry out this research and technical service; develops engineering data and measurement capabilities; provides engineering measurement traceability services; develops test methods and proposes engineering standards and code changes; develops and proposes new engineering practices; and develops and improves mechanisms to transfer results of its research to the utlimate user. The Laboratory consists of the following centers: Applied Mathematics — Electronics and Electrical Engineering' — Mechanical Engineering and Process Technology' — Building Technology — Fire Research — Consumer Product Technology — Field Methods. THE INSTITUTE FOR COMPUTER SCIENCES AND TECHNOLOGY conducts research and provides scientific and technical services to aid Federal Agencies in the selection, acquisition, application, and use of computer technology to improve effectiveness and economy in Government operations in accordance with Public Law 89-306 (40 U.S.C. 759), relevant Executive Orders, and other directives; carries out this mission by managing the Federal Information Processing Standards Program, developing Federal ADP standards guidelines, and managing Federal participation in ADP voluntary standardization activities; provides scientific and technological advisory services and assistance to Federal Agencies; and provides the technical foundation for computer-related policies of the Federal Government. The Institute consists of the following divisions: Systems and Software — Computer Systems Engineering — Information Technology. 'Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted; mailing address Washington, D.C. 20234. 'Some divisions within the center are located at Boulder, Colorado, 80303. The National Bureau of Standards was reorganized, effective April 9, 1978. JAN Z W3 NBS BUILDING SCIENCE SERIES 117 1^1 Experimental Verification of a Standard Test Procedure for Solar Collectors James E. Hill John P. Jenkins and Dennis E. Jones Center for Building Technology National Engineering Laboratory National Bureau of Standards Washington, D.C. 20234 Prepared for The Department of Energy Research and Development Branch for Solar Heating and Cooling Office of the Assistant Secretary for Conservation and Solar Applications Washington, D.C. 20545 U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary Jordan J. Baruch, Assistant Secretary for Science and Technology NATIONAL BUREAU OF STANDARDS, Ernest Ambler, Director Issued January 1979 Library of Congress Catalog Card Number: 78-600138 National Bureau of Standards Building Science Series 117 Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 117, 127 pages (Jan. 1979) CODEN: BSSNBV U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1978 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 Stock No. 003-003-02008-7 Price $3.00 (Add 25 percent additional for other than U.S. mailing). CONTENTS Page Abstract iv 1. Introduction 1 2. ASHRAE Standard 93-77 3 3. Description of NBS Test Facility 11 4. Test Results 25 5. Summary and Conclusions 41 6. Recommendations for Future Work 45 7. References 47 Tables 51 Appendix A - Calculation of Air Flow Rate Using a Nozzle and Pressure Difference Measurements 61 Appendix B - Description of a Radiometer to Determine Sky Temperature 64 Figures 67 iii Experimental Verification of a Standard Test Procedure for Solar Collectors by James E, Hill, John P. Jenkins and Dennis E. Jones Abstract A proposed procedure for testing and rating solar collectors based on thermal performance was published by the National Bureau of Standards (NBS) in 1974, Subsequently, the American Society of Heating, Refrig- erating, and Air Conditioning (ASHRAE) developed a modified version of the NBS procedure which was adopted in early 1977 as ASHRAE Standard 93-77. A test facility for water-heating and air-heating collectors has been built at NBS and was used to support the development of Standard 93-77, The purpose of this report is to describe the recently adopted test procedure, the NBS test facility, and the tests that were conducted to support the development of the procedure. Keywords: Measurement; solar collector; solar energy; solar radiation; standards; standard test; testing. In discussing this experimental program, certain commercial components were used and are identified in order to provide a descriptive characteri- zation of their features. Inclusion of a given component is this report in no case implies a recommendation or endorsement by the National Bureau of Standards, and the presentation should not be construed as a certifica- tion that any component would provide the indicated performance. Similarly, the omission of a component does not imply that its capabilities are less than those of the included components. This report is intended to be informative and instructive and not an evaluation of any commercially available components. iv 1. INTRODUCTION A proposal for testing and rating solar collectors based on thermal performance was published by the National Bureau of Standards (NBS) in 1974 [1-3]," The procedure prescribed that a series of outdoor steady-state tests be conducted to determine the near-normal-incidence efficiency of the collector over a range of temperature conditions. The American Society of Heating, Refrigerating, and Air Conditioning Engineers subsequently developed a modified version of the NBS procedure which was adopted in February, 1977, as ASHRAE Standard 93-77 [4]. It is similar to the NBS procedure but calls for additional tests to determine the collector time constant as well as an incident angle correction factor that can be applied to the near-normal-incidence efficiency to determine collector performance both early in the morning and late in the day. Three test loops have been built at NBS in accordance with ASHRAE Stan- dard 93-77, two for modular water-heating collectors and the other for Figures in brackets indicate literature references at end of the report, 1 air heaters. A major part of the NBS collector testing program since mid-197 6 has been devoted to using these facilities to support the development of Standard 93-77, The purpose of this report is to describe the recently adopted test procedure, the NBS test loops, and the tests that were conducted during 1976 and 1977 to support the adoption of the procedure. A second major part of the NBS collector testing work has been to con- duct a round robin program in which two flat-plate liquid-heating collectors were tested by 21 organizations around the United States during 1976 and early 1977. The purpose of the program was to have a a variety of testing laboratories attempt to utilize the NBS test procedure* and then determine the extent to which the results differed or were comparable. The test data and subsequent analysis for this program are available in separate publications [5, 6], *ASHRAE Standard 93-77 was not adopted at the time this program was initiated. 2 93 BASBDO^^^'>'^'^OE DEVICES 2. ASHRAE STANDARD 93-77 The testing procedure recommended by NBS in reference [1-3] called for the determination of the thermal efficiency of the solar collector by passing the heat transfer fluid

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