Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized HEAT TRANSMISSION MEASUREMENTS IN THERMAL INSULATIONS A symposium sponsored by ASTM Committee C-16 on Thermal and Cryogenic Insulating Materials AMERICAN SOCIETY FOR TESTING AND MATERIALS Philadelphia, Pa., 16-17 April 1973 ASTM SPECIAL TECHNICAL PUBLICATION 544 R P Tye, symposium chairman List price $30.75 04-544000-10 AMERICAN SOCIETY FOR TESTING AND MATERIALS 1916 Race Street, Philadelphia, Pa 19103 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductio © by American Society for Testing and Materials 1974 Library of Congress Catalog Card number: 73-87351 NOTE The Society is not responsible, as a body, for the statements and opinions advanced in this publication Printed in Baltimore, Maryland June, 1974 Printed in Philadelphia, Pennsylvania Second Printing, January, 1980 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions autho Foreword The Symposium on Contributions of Basic Heat Transmission Measurements to the Design and Behavior of Thermal Insulation Systems was held at the American Society for Testing and Materials Headquarters in Philadelphia, Pa., on 16-17 April 1973 The symposium was sponsored by ASTM Committee C-16 on Thermal and Cryogenic Insulating Materials R P Tye, Dynatech R/D Company, presided as the symposium chairman Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authoriz Related ASTM Publications Thermal Insulating Covers for NPS Piping, Vessel Lagging and Dished Head Segments ASTM Recommended Practice for Prefabrication and Field Fabrication o f - C 450 adjunct (1965), $4.25, 12-304500-00 Manual on the Use of Thermocouples in Temperature Measurement, STP 470A (1974), $17.50 04-470010-40 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Contents Introduction Definitions and Thermal Modelling What Property Do We Measure-^^TM Subcommittee CI 6.30 Measurement Philosophy of Subcommittee CI 6-30 Heat Transfer The Necessity of Multiple Measurements Recommendations for Future Changes Establishing Steady-State Thermal Conditions in Flat Slab SpecimensC.J.Shirtliffe Basic Problem Common Factors in Models Model Descriptions and Solutions Simplification of Solutions Truncation of Solutions Inversion of the Solutions Comparison of Settling Times Accuracy of Equations Conclusions Mechanisms of Heat Transfer in Permeable Insulation and Their Investigation in a Special Guarded Hot Plate—C G Bankvall Measurement of Heat Transfer The Guarded Hot Plate Heat Transfer Mechanisms in Fibrous Insulation The Natural Convective Heat Transfer Summary Water Vapor Diffusion and Frost in Porous Materials—^ A uracher Diffusion in Porous Frost-Containing Materials Diffusion on Simple, Frost-Containing Pore Models Diffusion in Frost-Containing Sphere Packings Discussion Conclusion Radiative Contribution to the Thermal Conductivity of Fibrous Insulations-i? M F Linford, R J Schmitt, and T A Hughes Nomenclature Theoretical Models for Radiant Heat Transfer Experimental Approach Experimental Results Calculation of the Radiation Transmission Component Conclusions Predicting Spacecraft Multilayer Insulation Performance from Heat Transfer Measurements—I D Stimpson and W A Hagemeyer System-Level MLI Blanket Results Types of Calorimeters Used The JPL Test Program Copyright Downloaded/printed University by by of 5 11 13 15 15 15 16 17 22 23 24 24 34 35 35 40 43 48 49 50 51 61 66 67 68 69 70 75 78 82 83 85 87 89 90 Discussion of Future MLI Requirements Conclusions 92 92 Techniques Design Criteria for Guarded Hot Plate Apparatus-F De Ponte and P Di Filippo The Guarded Hot Plate The Cold Plate Conclusions Suitable Steady-State Methods for Measurement of Effective Thermal Conductivity in Rigid Insulations-IV T Engelke Comparative Rod Apparatus Radial Inflow Apparatus Application Conclusions Thermal Conductance of Pipe Insulation—A Large-Scale Test Apparatus— L.R.Kimball Test Procedure Selected Experimental Results Discussion Conclusions New Development in Design of Equipment for Measuring Thermal Conductivity and Heat Flow-is Brendeng and P E Frivik Nomenclature Steady-State Measurements Test Results Transient State Measurements Robinson Line-Heat-Source Guarded Hot Plate Apparatus-M H Hahn, H E Robinson, and D R Flynn Mathematical Analysis of Line-Heat-Source Guarded Hot Plate Design of Proposed Apparatus Conclusion Calibrated Hot Box: An Effective Means for Measuring Thermal Conductance in Large Wall Sections—X R Mumaw Description of Test Apparatus Construction of Test Apparatus Hot Side Construction Details Cold Side Construction Details Specimen Frame Construction Air Infiltration Test Capability Obtaining Proper Test Results-The Data System Hot Side Chamber Calibration Testing Procedure Discussion of Testing Results Conclusions and Recommendations 193 194 195 196 198 199 199 200 201 202 203 211 Results and Applications Improving the Thermal Performance of the Ordinary Concrete Block— H N Knickle and Edgar Ducharme Procedure Experimental Work 215 216 218 Copyright Downloaded/printed University by by of 97 99 109 116 118 120 126 129 133 135 136 140 142 146 147 148 149 156 164 167 169 185 191 Economic Analysis Conclusions Some Recent Experimental Data on Glass Fiber Insulating Materials and Their Use for a Reliable Design of Insulations at Low TemperaturesD Fournier and S Klarsfeld Theoretical Data Measurements Facilities Materials Investigated and Test Procedure Experimental Results Some Applications of Both Theoretical Results and Experimental Data to Design Actual Insulations at Low Temperatures General Conclusion Evacuated Load Bearing Thermal Insulation up to 800°C-D J Dickson Procedure Experimental Results Discussion Conclusions Thermal Conductivity of Evacuated Glass Beads: Line Source Measurements in a Large Volume Bead Bed Between 225 and 300 K—M G Langseth, F E Ruccia, and A E Wechsler Nomenclature Bead Tank Conductivity Measurements Using a Line Source Heat Flow Probe and Line Source Probe Comparisons Conclusions High Performance Thermal Insulation for an Implantable Artificial Heart-Z) R Stoner, R C Svedberg, J W H Chi, and T Vojnovich Thermal Test Apparatus Fabrication of Insulation Systems Experimental Results Discussion Study of Thermophysical Properties of Constructional Materials in a Temperature Range from 10 to 400 Yi—A V Luikov, A G Shashkov, L L Vasiliev, S A Tanaeva, Yu P Bolshakov, and L S Domorod Nomenclature Experimental Procedure Analysis and Measurement of the Heat Transmission of Multi-Component Insulation Panels for Thermal Protection of Cryogenic Liquid Storage Vessels-/ G Bourne and R P Tye Materials and Systems Evaluated Experimental Details Analytical Model Results and Discussion Appendix Reference Materials of Low Thermal Conductivity Questionnaire Copyright Downloaded/printed University by by of 220 221 223 224 227 230 231 235 240 243 245 248 250 253 256 257 259 270 273 275 277 280 281 285 290 290 292 297 299 300 301 304 307 307 309 STP544-EB/Jun 19874 Introduction During the past decade there has been an ever-increasing utilization of thermal insulation materials and systems Furthermore, the impact of the world energy crisis has fostered additional expansion in the prediction and use of thermal insulation which will not diminish in the coming years Applications have become more exotic, conditions of temperature and environment more extreme, and the consequent insulation systems and their means of evaluation are now more sophisticated As a result, new methods for measurement of thermal performance must be developed and existing methods improved in order to keep abreast of this continued use of thermal insulation Insulating materials are generally inhomogeneous, because heat transfer in them can take place through a number of separate and interacting mechanisms By means of more reliable measurements of heat transmission, we become more aware of these mechanisms and how the performance of certain materials and systems depend less upon solid conduction than upon other processes such as radiation, convection, and mass transfer With more confidence in the results, we can better understand heat transmission behavior and, consequently, develop better and more economical materials and systems In the United States, ASTM Committee C-16 on Thermal and Cryogenic Insulating Materials is responsible for the promulgation of standards concerning thermal and cryogenic insulation materials, systems, and test methods Within this committee, Subcommittee CI6.30 on Thermal Conductance is directly responsible for test methods relating to heat transmission characteristics The subcommittee has kept abreast of developments in the field by continuously revising and upgrading the relevant standard test methods under their jurisdiction and by communicating, where possible, with their counterparts on similar national committees In addition, they have foreseen future requirements by developing new or extending existing standards to fulfill the potential needs The purpose of these test methods is to uphold the realistic philosophy by evaluating an insulation under operating conditions rather than by measuring a physicallydefined property which may have no meaning for these materials and systems Seven years ago, Committee C-16 sponsored a similar technical meeting where the topic related specifically to heat transmission measurements at cryogenic temperatures We have arrived at a point where significant developments in the evaluation of heat transmission have taken place; therefore, the committee Copyright' 1974 by A S T M International Copyright by Downloaded/printed University of ASTM by Washington www.astm.org Int'l (all (University rights of reserved); Washington) Fri pursuant Jan to HEAT TRANSMISSION MEASUREMENTS decided that a further international meeting among workers in this field was justified so current technologies and ideas could be discussed and subsequently applied to future worldwide activities The goal of this symposium was to provide a forum which would extend our horizons, cover all types of insulations at all operating temperatures, and illustrate that better measurement and performance characteristics can lead to further improvements in materials and systems The international group of papers in this volume covers representative subjects in the areas of fundamental studies of heat transmission processes, experimental techniques, both large and small scale, and the measurement and analysis of particular materials or systems for specific applications The wide variety of subjects discussed, especially the Subcommittee C 16.30 position paper which outlines their future philosophy, should stimulate further activities The international representation of authors produces a further cross-fertilization of ideas which ultimately promotes greater international cooperation One particular area concerns that of the well characterized reference materials of low thermal conductivity being made available in the future The Appendix briefly outlines how Subcommittee C16.30 has started the work to solve the problem In conclusion, I wish to thank all of the authors for their efforts in making the symposium a success The paper by B Tsevetkov, "Experimental Determinations of the Thermal Conductivity of Fluids by Coaxial-Cylinder Apparatus," was received too late for inclusion in this pubhcation and will appear in the July 1974 issue of the Journal of Testing and Evaluation I trust that we have discovered new areas of concentration resulting in more numerous future meetings R P Tye Manager, Testing Services, Dynatech R/D Co., Cambridge, Mass symposium chairman Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authori 294 HEAT TRANSMISSION MEASUREMENTS TABLE 2-Thermophysical properties of construction glass-fiber material Temperature, K Thermal Conductivity, W-m"'-K-' Thermal Diffusivity, m^-s"' 80 90 100 110 120 130 140 150 160 170 180 190 200 210 220 230 240 250 260 270 280 290 300 310 320 330 340 350 360 370 380 390 400 410 420 0.1650 0.1655 0.1660 0.1670 0.1675 0.1680 0.1690 0.1700 0.1710 0.1699 0.1720 0.1730 0.1740 0.1760 0.1765 0.1780 0.1785 0.1800 0.1810 0.1820 0.1835 0.1845 0.1860 0.1865 0.1880 0.1890 0.1900 0.1915 0.1925 0.1940 0.1950 0.1965 0.1980 0.2000 0.2100 0.297-10-'' 0.272-10-' 0.249-10-' 0.236-10-' 0.219-10-' 0.205-10-' 0.195-10-' 0.178-10-' 0.167-10-' 0.154-10-' 0.143-10-' 0.1328-10' 0.1245-10' 0.1172-10' 0.1097-10-' 0.1025-10-' 0.0957-10-' 0.0900-10"' 0.0836-10' 0.0785-10-' 0.0734-10-' 0.0694-10"' 0.0647-10-' 0.0607-10-' 0.0572-10-' 0.0533-10' 0.0504-10-' 0.0475-10' 0.0450-10' 0.0427-10-' 0.0405-10-' 0.0373-10-' 0.0365-10' 0.0348-10-' 0.0348-10' Specific Heat, J-kg-'-K-' 400 440 480 510 550 590 640 690 740 800 865 940 1005 1080 1160 1250 1340 1440 1560 1670 1800 1910 2070 2210 2370 2550 2720 2900 3080 3270 3460 3700 3910 4130 4350 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized LUIKOV ETAL ON THERMOPHYSICAL PROPERTIES 295 TABLE l-Thermophysical properties of Textolyte (1439 kg/m') Temperature, K Thermal Conductivity, W-m"'-K-' Thermal Diffusivity, m' -s-' specific Heat, (lO-')J-kg-'-K-' 11.6 18.6 29.7 36.5 43.2 49.8 56.4 62.6 76.9 84.9 89.1 96.1 105 114.8 124.8 133.1 142.2 148.8 156 162.2 173.4 177.8 183 195.5 206.7 215.6 223.3 232.1 243.3 252.8 263 281 296.8 305.4 0.180 0.252 0.274 0.266 0.320 0.345 0.326 0.330 0.303 0.298 0.290 0.286 0.309 0.318 0.327 0.336 0.346 0.356 0.389 0.384 0.432 0.458 0.440 0.455 0.455 0.444 0.446 0.446 0.444 0.451 0.450 0.449 0.460 0.462 3.44-10' 1.85-10-' 1.08-10-' 1.04-10-' 0.930 10-' 0.845 10-' 0.800 ' 0.665 10-' 0.634 10-' 0.525 ' 0.506 ' 0.509 ' 0.442 •lOr' 0.470 10-' 0.450 ' 0.398 10-' 0.335 10-' 0.410 ' 0.361 10-' 0.386 10-' 0.346 10-' 0.434 10-' 0.384 10-' 0.425 ' 0.336 10-' 0.318 10-' 0.290 ' 0.291 10-' 0.260 ' 0.270 10-' 0.243 10-' 0.214 10-' 0.210-10-' 0.502 1.011 1.650 2.099 2.558 2.644 2.804 3.100 3.202 3.140 3.384 3.547 4.040 4.170 4.500 5.200 6.000 5.700 6.398 6.740 7.000 6.300 6.820 7.910 6.410 8.298 9.000 8.900 10.029 9.729 11.100 11.800 11.700 hollow cylinder (0 = 25 mm, = 45 mm, = 140 mm) and those for polymethylmetacrylate, in the form of a solid cylinder (0 = 40 mm, = 120 mm) The maximum error in the data presented amounts to 10 percent References [1 ] Luikov, A W., Analytical Heat Diffusion Theory, Academic Press, New York, 1968 [2] Luikov, A V., Shashkov, A G., and Vasiliev, L L in Proceedings, Third Symposium on Thermophysical Properties, 22-25 March 1965 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 296 HEAT TRANSMISSION MEASUREMENTS TABLE 4-Thermophysical properties of polymethylmetacrylate Temperature, K Thermal Conductivity, W-m-'-K"' 17.00 23.45 32.07 38.725 43.26 49.235 54.20 60.15 65.745 75.65 87.65 99.30 104.025 110.95 117.525 127.925 134.760 141.05 147.225 153.00 164.635 175.835 184.340 211.36 221.55 231.135 240.92 249.70 259.15 270.15 282.675 291.79 0.049 0.066 0.082 0.084 0.0885 0.098 0.101 0.115 0.117 0.122 0.131 0.134 0.136 0.141 0.146 0.149 0.151 0.153 0.156 0.160 0.164 0.166 0.167 0.170 0.171 0.174 0.175 0.177 0.179 0.182 0.185 0.187 Thermal Diffusivity, m^ -s"' Specific Heat, (10"')J-kg"'-K"' 4.15-io-' 3.58-10"' 3.48-10-' 3.26-10-' S.IO-IO"' 2.96-10" 2.78-10"' 2.60-10-' 2.40-10' 2.11-10-' 1.86-10"' 1.182-10"' 1.71-10"' 0.0825 0.119 0.125 0.170 0.201 0.230 0.186 0.238 0.290 0.340 0.380 0.403 0.430 0.448 1.54-10-' 1.50-10"' 1.45-10"' 1.44-10"' 1.42-10-' 1.40-10-' 0.490 0.545 0.560 0.581 0.610 0.620 1.38-io"' 1.17-10"' 1.15-10"' 0.770 0.790 1.08-10" 1.06-10"' 1.03-10"' 1.00-10"' 0.97-10"' 0.865 0.910 0.935 0.966 1.010 [3\ Vasiliev, L L., Inzhenerno-fizicheskiiZhurnal, Vol 7, No 5, 1964, pp 76-84 (•^i Vasiliev, L h., Inzhenerno-fizicheskii Zhurnal, Vol 17, No 6, 1969, pp 1119-1122 [5] Shashlcov, A G., Domorod, L S., Tanaeva, S A., and Vasiliev, L L., International Journal of Heat Mass Transfer, Vol 15,1972, pp 2385-2390 [6] Luikov, A V., Vasiliev, L L., Shnyrev, A D., Barsukov, V F., and Klebanovich, A A., Progress in Refrigeration Science and Technology, Vol 1,1973 [7] Y{ama\hy,T.y , Journal of Applied Physics,Vo\ 35, No 4, 1964, pp 1190-1200 [S] Steere, R S., Journal of Applied Physics, Vol 37, No 9,1966, pp 3338-3344 [9] Tye, R P in Proceedings, XIII International Congress of Refrigeration, Washington, D C V o l 1,1971 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions auth / G Bourne l and R P Tye ' Analysis and Measurement of the Heat Transmission of Multi-Component Insulation Panels for Thermal Protection of Cryogenic Liquid Storage Vessels REFERENCE: Bourne, J G and Tye, R P., "Analysis and Measurement of the Heat Transmission of Multi-Component Insulation Panels for Thermal Protection of Cryogenic Liquid Storage Vessels," Heat Transmission Measurements in Thermal Insulations, ASTM STP 544, American Society for Testing and Materials, 1974, pp 297-305 ABSTRACT: A new concept involving the use of easily fabricated and assembled panels consisting of balsa wood, rigid plastic foams, and wood facings has been proposed for the external thermal protection of large liquid natural gas storage vessels Heat transmission determinations in scale models of the proposed panels up to 90-mm thick have been undertaken with the use of a 600-mm square guarded hot plate apparatus for the proposed use temperature conditions In addition, thermal conductance measurements on the basic components have been made at regular temperature intervals over the approximate range 100 to 300 K An analytical model has been derived to predict the variation in test results with geometry This model can be used to select the optimum full scale configuration considering both thermal and structural performance and to predict tank heat leakage KEY WORDS: thermal insulation, insulating systems, fuel storage tanks, heat transmission During the past two decades there has been a continuing increase in the use of sophisticated thermal insulating material systems Present and future needs will not diminish the use of thermal insulations nor for the quest for more efficient systems Nowhere is this more apparent than in the many current designs Manager, Thermal Engineering Group, and manager, Testing Services, Thermatest Dept., respectively Dynatech R/D Company, Cambridge, Mass 02139 297 Copyright' 1974 by A S T M International Copyright by Downloaded/printed University of ASTM by Washington www.astm.org Int'l (all (University rights of reserved); Washington) Fri pursuant Jan to 298 HEAT TRANSMISSION MEASUREMENTS proposed for the insulation of the large liquid natural gas (LNG) tanks mounted upon the various types of ocean tanker vessels For these applications, while the thermal requirements remain paramount, any system contemplated must nominally become an integral part of the overall structure Thus, there has to be a distinct trade-off between the thermal and mechanical performance with the overall system still remaining economically viable While the ultimate solution for these LNG tanks is probably the use of an internal insulation material system, the various present designs are all oriented towards external insulation systems Most of these utilize existing materials in one mode or another and the thermal properties of the individual materials are often known; but it now becomes necessary to measure, or hopefully to predict, the performance of any system based upon them The present paper describes work carried out at Dynatech to evaluate the thermal performance of a number of scaled models of prepared thermal insulation systems developed by Baltek Corporation These systems are based upon the balsa wood in combination with other insulating materials such as cellular plastics and wooden face panels In addition, a one-dimensional analytical model has been developed in order to predict the performance of full scale systems of this type from a knowledge of that of the individual components—samples of which were also evaluated In any system it is necessary for there to be two functions: namely, thermal insulation and structural load bearing Since conventional lightweight good thermal insulation materials have poor strength characteristics, it is necessary that mechanical strength be provided by other means in order to take full advantage of these excellent thermal characteristics One such method is to build a structure composed of balsa wood and insulation This one insulation system consists of strips of balsa wood, itself a good thermal insulator, in combination with strips of different cellular plastics Balsa wood is ideal for this class of system since it is easy to work with, lightweight, stable, and, best of all, when it is aligned with the grain perpendicular to the face of the insulation (end grain), the sections where the beams cross act as load bearing points permitting pressure to be applied to the surface of the insulation The overall thickness of the proposed systems for LNG appUcations ranges from approximately 220 to 250 mm They consist nominally of three equal thickness individual layers, each composed of a calculated minimum amount of end grain balsa plus some flat grain, in various orientations, combined with the maximum amount of other insulation possible Usually one or both sides is faced with to 8-mm-thick plywood In application one face will be cooled to approximately 110 K while the other will be close to 300 K The thickness of the system when combined with these temperature requirements makes testing of full scale panels somewhat Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions au BOURNE AND TYE ON MULTI-COMPONENT INSULATION PANELS 299 difficult and very expensive It was therefore decided that approximate one-third scale models of the various basic materials in built up sections would be evaluated, and the experimentally measured thermal performance of the component sections would be compared to those predicted from the model Materials and Systems Evaluated A total of ten test "panels" were to be evaluated Each panel was supplied in duplicate pieces, each 600-mm square with appropriate uniform thickness, some 76 mm for unfaced materials, and for those having plywood faces 88 to 91 mm The faces were as flat as could be obtained for commercially available materials, and any sUght imperfections were removed by hand finishing A typical one-third scale model thermal conductivity panel configuration is shown in Fig The sample descriptions are as follows: Commercial urethane foam having a density of 44.4 kg* m"' Commercial polystyrene foam having a density of 18.5 kg-m"^ Solid flat grain balsa wood having a density of 210 kg-m"^ Solid end grain balsa wood having a density of 110 kg-m"^ Commercial foamed glass having a density of 144 kg-m"^ Three equal thickness layers of the basic system (alternate balsa wood and polystyrene foam strips) with one mm plywood facing The individual layers were bonded together with a thin epoxy layer The angular displacement between the layers was 90 deg The same as Panel except that the layers were unbonded and there were two plywood facings plywood facing (top and/or bottom) balsa strips insulation FIG I-Schematic assembly of a typical thermal conductivity test configuration (All dimensions in millimetres) Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized 300 HEAT TRANSMISSION MEASUREMENTS Similar to Panel except with the angular displacement being 60 deg Panel without the plywood facings 10 Panel re-tested, with heat flow vertically up only 11 Panel with the polystyrene strips replaced by urethane strips Experimental Details The measurements of thermal performance were undertaken according to ASTM Test for Thermal Conductivity of Materials by Means of the Guarded Hot Plate (C 177-71) utilizing a 600-mm square guarded hot plate of conventional design The hot plate consisted of a central 300-mm square metering section, a separate 150-mm-wide annular guard section with a 3-mm gap between them Each section consisted of a very uniformly wound resistance heater embedded in a silicone rubber and with blackened aluminum surface plates covering both sides The total thickness was some 19 mm when the whole system was clamped together A 12-junction multi-way differential thermocouple was attached such that alternate junctions were in the central and guard sections close to the gap between them A thin Teflon sheet was placed on the underside of each plate to ensure that the thermocouple junctions were electrically insulated from each other and each section The outer surface of each plate contained eight grooves, each approximately 1.5-mm wide and deep These grooves were cut such that four each ended at various positions in the central and guard sections, respectively Insulated thermocouples were fitted tightly into the grooves and the bead junctions were cemented in place—care being taken to make sure that they remained flush with the surface In this way the absolute temperature and temperature distribution across each face could be obtained accurately with httle or no heat distortion through the plates and samples Each cold plate consisted of a uniformly wound copper tubing fluid cooled heatsink and a thick aluminum plate with black surfaces, with a uniformly wound resistance heater between them The upper surface of the plate contained a similar number of thermocouples over the surface to those used in the central plates For each determination the sample pieces were placed under an applied load on either side of the hot plate and between the respective upper and lower cold plates For the first two composite panels 36-gage butt-welded thermocouples protected by a thin teflon tape were laid across the four surfaces of the test samples in two positions in each of the central and guard sections, respectively During the measurements it was found that the temperature readings given by the thermocouples in the plates and in the sample agreed to better than 1.5 K Since the temperature differences were over 200 K the overall thermal conductivity values did not change by more than percent, w'hichever thermocouple was used However, the temperature distributions across the plate Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authoriz BOURNE AND TYE ON MULTI-COMPONENT INSULATION PANELS 301 were found to be better than ± 0.2 K For all other subsequent tests no thermocouples were placed on the surface The composite sample was surrounded by a shroud ahd all of the interspace and surrounds filled with a pre-dried powder thermal insiilation to reduce radial losses A large plastic container was placed over the whole apparatus and dry nitrogen gas was flushed through the system for several hours and maintained during the test A steady temperature distribution was established in the system by running liquid nitrogen through the cold plates at a controlled rate and adjusting the d-c power to the central heater The power to the guard heater was controlled automatically by utilizing the output of the differential thermocouples such that the temperature across the main and guard heaters remained constant Equilibrium conditions were attained normally after some to 10 h At equilibrium the d-c power was measured with a precision resistance network and the temperatures were evaluated from the average readings of the numerous thermocouples dispersed about the various surfaces The thermal conductivity was derived in the usual manner For the single case with measurement for the panel with vertical up flow of heat, liquid nitrogen was not run through the lower heat sink The temperature of the lower surface was controlled by adjusting the power to the heater over the lower cold plate so that the temperature difference across the lower sample was maintained at zero to better than ± 0.2 K In this way all of the power generated in the central heater contributed to the temperature gradient established across the upper sample Analytical Model A simple one-dimensional constant property model of the system has been developed It is relatively precise for thick sections providing they have symmetry about the axis Conductive heat transfer from the hot surface to the cold surface is assumed to occur through four separate paths One path goes through the wood only and one through the insulation only The other two pass through three alternating layers of wood and insulation, one with the central layer being wood and one with the central layer being insulation, as in Fig Use of this network implies that there is no thermal short circuiting of the matrix, caused by separation of the different segments which may have different coefficients of thermal expansion, nor any significant convective heat transfer An additional assumption is that heat transfer from one path to another has a negligible effect on the overall coefficient In order to verify this assumption a 264-node two-dimensional model was generated for a system simulating two beams of wood embedded in an infinite plate of insulation The equivalent conductance of the two-dimensional system Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions auth 302 HEAT TRANSMISSION MEASUREMENTS h^ ^ ^-•H l ^ ^ ^ v ^ ^ ^ >v hN v v V ^ A tjoQ^ ^ k ^ \ Insulation V ^ s s, •N V ^ 1^ • Plywood FIG 2~Thermal network to estimate conductance of balsa-insulation system was found to be within percent of the value estimated by the one-dimensional analysis In solving the network it is assumed that the average thermal conductivity over the total temperature range for the single component could be used for each individual resistance The systems evaluated ^re symmetric, for example, in the case with two wood segments, heat passes through balsa wood, then the insulation segment, then balsa wood again Therefore, the average temperature of the insulation segment is the same as the average temperature obtained in a parallel path that is solely insulation even though the surfaces of the insulation segment and the parallel insulation path are at different temperatures Similarly, the average temperature of the two balsa segments is the same as the average Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions autho BOURNE AND TYE ON MULTI-COMPONENT INSULATION PANELS 303 temperature of an all-wood path The one-dimensional model has not been verified by test for systems which are not symmetric about the mid-plane The overall thermal conductivity for a system faced with two sheets of plywood is X j - Xi + \ "•" ^3 "•" ^4 where Xi =A all balsa (1) X, =A all insulation (2) Xa =^3 25 + 3A X^ Xft I two-thirds balsa (3) X,, 25 + 3A 26T ^ • J two-thirds insulation (4) x^ XT) ! where AI to A4 = the respective areas of each section, A = the thickness of the balsa wood and insulation, = the thickness of the facings, and X6,X,-,and Xw = the overall thermal conductivities of the balsa wood, insulation, and facing material, respectively Overall thermal conductivity values for the temperature conditions of the test were established for the urethane, polystyrene, and balsa wood of the appropriate density The values are shown in Table in the result section The thermal conductivity of the plywood facing was estimated to be 0.14 W*m~' 'KT' (1 Btu*in*hr~' "ft"^ - F ' ) A large error in this estimate has negligible effect in the final results The wood in the test panels occupies 31.25 percent of each layer and alternate layers are perpendicular so that the area proportions are: Ai =0.097, A2 =0.685, and A3 =^4 =0.109 In the actual large scale panels the wood will occupy 33.3 percent of each layer Thus, the calculated results will tend to be Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions author 304 HEAT TRANSMISSION MEASUREMENTS TABLE I—Thermal conductivity often thermal insulation materials and systems for conditions: hot face 395 ± K, cold face 82 ±2 K Thermal Conductivity, lO'W-m-'-K"' (Btu-in-hr'-fr'-F-') Sample No Measured Derived Difference,', 10 11 2.18(0.15) 2.44 (0.17) 4.52(0.31) 5.52 (0.38) 4.02 (0.28) 3.63 (0.25) 3.77 (0.26) 3.71 (0.26) 3.46 (0.24) 3.49 (0.24) 3.34 (0.23) 3.47(0.24) 3.67(0.255) 3.67(0.255) 3.25(0.225) 3.25(0.225) 3.35(0.23) 4.5 2.7 2.7 6.8 6.8 lower than those expected at full scale The effect is estimated to be of the order of 1.5 to percent Results and Discussion The experimental results obtained for all the samples evaluated are given in Table Also included are the values calculated for the composite panels using the experimentally determined values for the individual material in the previously described analysis In discussing the results two main factors have to be considered These are the performance values obtained for the various materials and systems and the degree of agreement between the measured and derived values, respectively In the former case no direct comparisons can be made with any previous results due to the factor of differences in materials and the conditions of test However, for the case of the cellular plastics and the foam glass materials the overall conductivity values obtained are in good agreement with those which can be obtained from the curves of Tye^ who measured some similar materials at cryogenic temperatures but with small temperature differences across the test samples The curves provided in that paper over the approximate range 100 to 300 K for different insulating materials can then be used to derive overall thermal conductivity values for other wider sets of temperature difference conditions within that range, and thus the proposed analysis could be refined, particularly if similar results were made available for balsa wood over the same temperature range The balsa wood results show the typical anistropy that is expected for wood ' Tye, R P., Proceedings, XIII International Congress of Refrigeration, Washington, D C, Vol 1, Institute International de Froid, Paris, 1971 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized BOURNE AND TYE ON MULTI-COMPONENT INSULATION PANELS 305 materials In this case the flat grain material had a much higher density than the end grain due to load bearing requirements Much larger anisotropy values can be expected for flat and end grain materials having similar densities Overall values for the panels indicate that an improvement of performance can be obtained by use of such systems when compared directly with structural insulations such as all balsa wood or foamed glass Since any insulation material can be used in conjunction with the balsa, additional systems can be devised for particular requirements Very good agreement is apparent between the measured and derived values for the various panel systems The largest differences are for Panels and 10 where the systems were not surfaced It is possible that in these samples where internal movements of components are only partially restricted differential expansion did, in fact, produce small separations between components allowing some direct thermal short circuiting However, the differences are still small Thus, it would appear that the proposed simple approach is valid and can be used to predict the performance of similar types of systems providing overall average thermal conductivities of the components are available for the actual conditions These can be obtained by direct measurement or from curves of thermal conductivity measured over the complete temperature range or using small temperature differences Acknowledgments The authors wish to thank Baltek Corporation for permission to publish the results of the experimental study They also wish to thank their colleague H S Spector who carried out much of the careful experimental work described Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authoriz STP544-EB/Jun 19874 APPENDIX Reference Materials of Low Thermal Conductivity During recent years, Subcommittee CI6.30 on Thermal Conductance of ASTM Committee C-16 on Thermal and Cryogenic Insulating Materials has spent a considerable amount of time and effort revising and upgrading its standards relative to the measurement of heat transmission in thermal insulations and systems In particular, the ASTM Test for Thermal Conductivity of Materials by Means of the Guarded Hot Plate (C 177-63) has been revised in scope so that it now covers the temperature range of to 1300 K In addition, the ASTM Test for Thermal Conductivity of Materials by Means of the Heat Flow Meter (C 518-70) has been accepted as a standard for certification purposes over a limited temperature range at or near room temperature, and further activities have been directed toward the promulgation of international specifications based on these methods The members of the task groups responsible for the revisions are quite aware of the fact that there are numerous deficiencies and a number of improvements still necessary in the standards Furthermore, different organizations have continually obtained wide variations in values on similar materials, even over a limited temperature range, when using modified forms of the basic apparatus These diversities are magnified as the temperatures and conditions become more extreme and consequent heat loss problems increase A task group has been established to resolve these problems and to examine the question of the availability of reference materials of low thermal conductivity covering the widest temperature range possible If reference materials are available then a cooperative measurements investigation should be carried out In this way all measurements will be improved and unreliable apparatus and techniques corrected Ultimately, testing laboratories will have to be certified to carry out ASTM tests In the area of heat transmission it is important to provide reference materials which can be used to evaluate the performance of a test apparatus Unlike materials of higher thermal conductivity where heat transport is predominantly by solid conduction mechanisms, heat transfer in thermal insulation is by a combination of modes including solid, gaseous, convection, and radiation Because the properties are affected by environment and temperature conditions, the ideal reference materials must be readily available and unaffected by heat treatment or at least be in a stabilized condition after heat treatment In order to obtain a true concept of their properties and stabilities, such materials must be made available and numerous measurements must be made on them by as many organizations as possible using different types of hot plate and heat meter apparatus under controlled temperature and environmental conditions 307 Copyright' 1974 by A S T M International Copyright by Downloaded/printed University of ASTM by Washington www.astm.org Int'l (all (University rights reserved); of Washington) Fri pursuant Jan to L 308 HEAT TRANSMISSION MEASUREMENTS The task group has concluded that disregarding the difficulties of effects of environment and temperature there are many candidate materials now available Many materials have been examined including a number in the range of thermal conductivity (~ lOT^ to W'm^'KT') covering various ranges of temperature, and at least one under high vacuum and at cryogenic temperatures (~ 10"* W'm"'Kr') The following materials have been proposed as worthy of study Min K 2000 for the range 300 to 1000 K A fiberglass material for the range 100 to 500 K Also a candidate for measurements in high vacuum at cryogenic temperatures Hypalon and a silicone rubber for the range 100 to 500 K A foamed glass for the range 100 to 600 K A foamed silica for the range 100 to 1100 K A silica fiber for the range 300 to 1200 K in different environments The accompanying questionnaire was sent to all those known to have apparatus for evaluation of thermal insulations So far, approximately 70 worldwide organizations have responded positively, stating they are willing to participate in all or part of an evaluation program Participation by others is welcome Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized Thermal Conductivity Reference Materials Project Questionnaire Do you have (a) guarded hot plate apparatus? (b) heat meter apparatus? (c) other for thermal insulations? Please identify What are the temperature limits? (a) hot face (6) cold face (c) differential across sample Can you control sample environment? (a) vacuum below 10"^ torr (b) gas pressures above atm What is orientation of plates? Can you change heat flow direction? What is sample configuration and maximum thickness? Can you control contact pressure on sample? Please give brief details of (a) temperature measurement techniques {b) power measurement techniques (c) thickness measurement and control (d) procedures for calibration Please give details of known or estimated (a) accuracy (b) precision 10 Are you willing to participate in measurement of some or all of the candidate reference materials? 11 Will you buy sets of samples once they can be made available? 12 Can you suggest other possible materials for consideration as reference materials of low thermal conductivity? Please supply the requested information and return to R P Tye, Dynatech R/D Company, 99 Erie Street, Cambridge, Mass 02139 309 Copyright by ASTM Int'l (all rights reserved); Fri Jan 23:12:22 EST 2016 Downloaded/printed by University of Washington (University of Washington) pursuant to License Agreement No further reproductions authorized