INCIDENCE ANGLE MODIFIERS IN CYLINDRICAL June 1996

107 Pages·2008·13.52 MB·English

INCIDENCE ANGLE MODIFIERS IN CYLINDRICAL
SOLAR COLLECTOR
DESXGN
FINAL REPORT FOR THE PERIOD
-
June 1996 May 1997
Joseph P. Ryan
Solar Energy Applications Laboratory
Colorado State University
Fort Collins, CO 80523
Date Published: May 1997
PREPARED FOR THE DEPARTMENT OF ENERGY
U.S.
CONSERVATION AND RENEWABLE ENERGY
Under Grant DE-FG36-95GO10093
DISCLAIMER
This report was prepared as an account of work sponsored by an agency of the
United States Government Neither the United States Government nor any agency
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The views and opinions of authors expressed herein do not ncocsslrily state or
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THESIS
INCIDENCE ANGLE
MODIFIERS
IN CYLINDRICAL COLLECTOR
SOLAR DESIGN
Submitted
by
Joseph
P. Ryan
Department of Mechanical Engineering
partial fulfiknent of the requirements
In
for the degree of Master of Science
Colorado State University
Fort Collins, Colorado
Spring
1997

.L D
ABSTRACT OF
THESIS
INCIDENCE ANGLE MODIFIERS
IN CYLINDRICAL SOLAR COLLECTOR DESIGN
This thesis presents an analysis of the thermal performance of cylindrical solar col-
lectors. A major contributor to performance is optics, the principle focus of this work. A
tool used to compute the incidence angle modifiers (IAM’s) for cylindrical solar collectors
is presented. The Monte Carlo Method is employed in a computer code to
Fortran 90
compute the hemispheric IAM’s of cylindrical solar collectors. Using concentric cylin-
ders, the tubes are modeled with and without back plane reflectors of varying size. The
computed IAM’s are verified both analytically and experimentally. Outdoor experiments
on an array of cylindrical tubes with various back planes and two different tube spacings
are described. Agreement with TRNSYS runs in daily energy gain is excellent. Over the
38 data sets, taken on different days, a maximum error of 11.2% is observed, with an aver-
age of 3%. Heat loss tests, used to calculate an overall heat loss coefficient for the
error
collector, are also described.
A parametric variation study is used to illustrate the effect of varying many of the
collector parameters. This study provides insight into the signScant design parameters
for cylindrical collectors. This insight is used to analyze the effect of these design
solar
parameters on the annual energy delivered by the collector. In addition, a simple cost
analysis illustrates the benefits of varying the design parameters. The use of this new pro-
gram and a detailed Life Cycle Cost analysis are the tools needed for optimizing the
design of a cylindrical solar collector.
...
Ill
*. c
The IAM code, executables, sample input and output files and instruction manual
can be found on the world wide web:
http://www.ColoState.EDU/Orgs/SEAL/resemh/
IAM/iam.html.
Joseph
F? Ryan
Department of Mechanical
Engineering
Colorado State University
Fort Collins, Colorado
80523
Spring 1997
TABLE OF CONTENTS
................................................................................................
ABSTRACT OF THESIS iii
ACKNOWLEDGMENTS ................................................................................................. v
.................................................................................................
TABLE OF CONTENTS vi
.........................................................................................................
LIST OF ix
FIGURES
.............................................................................................................
LIST OF TABLES x
........................................................................................................
NOMENCLAW xi
CHAmR1 . INTRODUCTION
......................................................................................................
1.1 Introduction 1
......................................................................................................
1.2 Background 3
.........................................................................................
1.3 Research Objectives 6
..........................................................................................................
1.4 Approach 6
.....................................................................................
1.5 of Thesis 7
Organization
CHAPTER 2 . THEORETICAL FORMULATION
......................................................................................................
2.1 Introduction 9
...............................................................................................
2.2 Physical System 9
...............................................................................
2.2.1 Geometry of Cylinders 9
...................................................................
2.2.2 Geometry of Planar Surfaces 11
.........................................................................................
2.3 Material Properties 13
...............................................
2.3.1 Radiative Properties for Opaque Surfaces 14
................................
2.3.2 Radiative Properties for Semi-transparent Surfaces 17
...................................................................................
2.4 Balance Model 21
Energy
...........................................................................
2.4.1 General Thermal Model 21
........................................................................
2.4.2 TRNSYS Thermal Model 23
..............................................................................
2.5 Problem Parameterization 25
........................................................................................................
2.6 26
Summary
vi
CHAPTER3 . MONTECARLOMODEL
....................................................................................................
3.1 Introduction 27
..............................................................................................
3.2 Implementation 28
...................................................................................
3.2.1 Material Properties 29
............................................................................
3.2.2 Ray Tracing Procedure 31
............................................................................................
3.2.3 Convergence 35
........................................................................................................
3.3 Summary 36
CHAPTER4 . EXPERIMENTALAPPROACH
....................................................................................................
4.1 Introduction 38
........................................................................................
4.2 System Description 38
......................................................................
4.2.1 NEG Sun Family Collector 38
.................................................................................
4.2.2 Collector Variations 40
......................................................................................
4.3 Heat Gain Procedure 41
................................................................................................
4.4 Heat Loss Test 43
..............................................................................................
4.5 Data Collection 45
.........................................................................................
4.6 Experimental Error 45
........................................................................................................
4.7 Summary 50
CHAPTER 5 . RESULTS AND DISCUSSION
....................................................................................................
5.1 Introduction 51
.....................................................................
5.2 Analytical Validation of IAM’s 51
.....................................................................................
5.3 Experimental Results 53
.............................................................................
5.3.1 Heat Loss Test Results 55
.............................................................................
5.3.2 Heat Gain Test Results 57
.........................................................................
5.4 Parametric Variation Results 60
.................................................................................
5.4.1 Effect of Tube Pitch 61
............................................................
5.4.2 Effect of Back Plane Reflectance 63
.....................................................................
5.4.3 Effect of Back Plane Width 65
.....................................................
5.4.4 Effect of Back Plane to Spacing 66
Tube
.....................................................
5.4.5 Effect of Collector Tube Absorptance 67
........................................................................
5.4.6 Effect of Glass Properties 67
.............................................................
5.5 Cylindrical Solar Collector Analysis 70
.................................................................
5.5.1 Annual TRNSYS Simulations 71
...........................................................................................
5.5.2 Cost Analysis 74
........................................................................................................
5.6 Summary 76
vii
CHAPTER 6 . CONCLUSIONS AND RECOMMENDATIONS
6.1 Summary ........................................................................................................ 78
................................................................
6.2 Sun Family Collector Design 80
NEG
..........................................................................
6.3 IAM Program Modifications 81
................................................................................................................
REFERENCES 82
APPENDIX A . PROGRAM MANUAL ............................................................... 84
IAM
. .......................................................................................
A 1 General Description 84
...............................................................................................................
A.2 Units 84
......................................................................................................
A.3 Input Deck 84
...........................................................................
A.4 Execution of IAM Program 87
AS Output Files .................................................................................................... 88
...........................................................................
A.6 Access to the IAM 88
Program
APPENDIX B . DECK ....................................................................... 89
TRNSYS INPUT
. ....................................................................................................
B Introduction 89
1
......................................................................................................
B.2 Input Deck 89
viii