DOCSLIB.ORG

Insulation Values

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Insulation Values INSULATION VALUES TECHNICAL BULLETIN Vol. 3, No. 1 JANUARY 2017 INSULATION VALUES This is a thermal resistance guide for our insulated panels. This document is to serve as an explanation of code compliance and how these values were determined. Code Compliance In North America, the most accepted energy efficiency standard for commercial construction is the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) Standard 90.1. The current edition is 2013. This standard provides both a prescriptive and a performance path to be chosen at the designer’s discretion. The prescriptive path is most commonly used and also provides the baseline performance level that is used to determine compliance for the performance path as well, so understanding this set of requirements is critical. Within the prescriptive path, two possible methods of compliance are available to determine the minimum thermal performance of opaque areas on the building envelope. Section 5.5.3 is the pertinent passage and it reads: 5.5.3 Opaque Areas. For all opaque surfaces except doors, compliance shall be demonstrated by one of the following two methods: a. Minimum rated R-value of insulation for the thermal resistance of the added insulation in framing cavities and continuous insulation only. Specifications listed in Normative Appendix A for each class of construction shall be used to determine compliance. b. Maximum U-factor, C-factor, or F-factor for the entire assembly. The values for typical construction assemblies listed in Normative Appendix A shall be used to determine compliance. Exceptions to Section 5.5.3: 1. For assemblies significantly different from those in Appendix A, calculations shall be performed in accordance with the procedures required in Appendix A. 2. For multiple assemblies within a single class of construction for a single space-conditioning category, compliance shall be shown for either (1) the most restrictive requirement or (2) an area- weighted average U-factor, C-factor, or F-factor. 2 INSULATION VALUES The definitions pertinent to this passage italicized above are: Continuous insulation (c.i.): insulation that is continuous across all structural members without thermal bridges other than fasteners and service openings. It is installed on the interior or exterior or is integral to any opaque surface of the building envelope. Rated R-value of insulation: the thermal resistance of the insulation alone as specified by the manufacturer in units of hr·ft2·°F/BTU at a mean temperature of 75°F. Rated R-value refers to the thermal resistance of the added insulation in framing cavities or insulated sheathing only and does not include the thermal resistance of other building materials or air films. U-factor (thermal transmittance): heat transmission in unit time through unit area of a material or construction and the boundary air films, induced by unit temperature difference between the environments on each side. Units of U are BTU/hr·ft2·°F. So in effect, there are two possible ways to comply with the prescriptive requirements for a roof or wall assembly: A. Provide insulation with a Rated R-value that meets or exceeds the minimum R-value requirement from the prescriptive tables 5.5-1 through 5.5-8, depending on climate zone. B. Provide an assembly with a U-factor that meets or falls below the maximum U-factor requirement from the prescriptive tables 5.5-1 through 5.5-8, depending on climate zone Appendix A of 90.1 contains calculation and testing requirements for R-value and U-factor determination as well as a dataset of U-factors that have been predetermined in accordance with the appendix for some common assemblies. If the assembly being provided does not meet the descriptions of the common assemblies in the appendix, then a thermal test or calculation method is the only way to determine a U-factor. In fact, exception a. of 5.5.3 provides the user with a shortcut to that conclusion. Testing requirements are given in Section A9.3 and calculation requirements are given in A9.4 of Appendix A. Different levels of rigor are to be used when calculating U-factors depending on the type of assembly; however, Section A9.2 does state that two-dimensional finite element methods are always allowed. The definitions above in conjunction with the requirements of Appendix A then dictate that if Method A is used, the R-value of the insulation must be determined by either ASTM C518 or ASTM C1363 with a mean temperature of 75 degrees Fahrenheit and cannot include air film effects. Furthermore, the assembly in question must meet the one of the descriptions in the Appendix. 3 INSULATION VALUES Otherwise, Method B must be used and the U-factor of the assembly is to be determined by testing per ASTM C1363 or finite element modeling. In either case, a representative sample section including panel edges, joints and thermal bridges such as fasteners is considered and the air film allowance provided in Section A.9.4.1 should be included as well. Insulated panels are not an assembly type but instead are insulated sheathing that can be utilized on various kinds of assemblies. Therefore, it is not entirely clear how they apply to ASHRAE requirements. IMPs have thermally broken side joints and since the presence of fasteners alone does not violate the requirements for continuous insulation, IMPs can be interpreted to meet that definition. However, many designers do not agree with that interpretation and instead want to treat IMPs as an assembly and therefore require U-values from the manufacturer since Method A would not apply in that instance. Unfortunately, ‘thermal bridge’ is not defined in ASHRAE 90.1, so no guidance is provided by the standard itself. Because of this ambiguity, it is not clear which method from Section 5.5.3 is to be used for IMPs. Therefore, R-values determined by test and U-factors determined by calculation in accordance with ASHRAE are presented in Table 2 below and it is left to the designer’s discretion which to use. Insulated Metal Panel R-value and U-factors The information is provided shows the results thermal modeling using the THERM V7 which was calibrated and verified using ASTM C518 and ASTM C1363 testing. With the many different widths, profiles and thicknesses it is not possible to test every possible variable for the products offered by Metl-Span. The THERM software is widely used and was developed at Lawrence Berkeley National Laboratory (LBNL) for heat-transfer analysis of the sometimes complicated geometries of real-world building products. 4 INSULATION VALUES Core R-value per Nominal ASTM C518 42” Wide Panel Mean Temp Core (hr·ft2·°F/BTU) Panel (°F) Thickness Profile (in.) U-factor R-value w/o air films w/ air films (BTU/ (hr·ft2·°F/ hr·ft2·°F) BTU) 2 14.29 15.14 0.0706 14.16 2.5 17.86 18.71 0.0516 19.38 3 21.43 22.28 0.0424 23.58 75 4 28.57 29.42 0.0324 30.86 5 35.71 36.56 0.0264 37.88 CF Mesa 6 42.86 43.71 0.0224 44.64 2 15.87 16.72 0.0669 14.95 2.5 19.84 20.69 0.0491 20.37 3 23.81 24.66 0.0401 24.94 40 4 31.75 32.60 0.0305 32.79 5 39.68 40.53 0.0248 40.32 6 47.62 48.47 0.0210 47.62 Core R-value per 36" Wide Panel ASTM C518 Core (1/4" reveal) Mean Temp (hr·ft2·°F/BTU) Panel Profile Thickness (°F) U-factor R-value (in.) w/o air films w/ air films (BTU/ (hr·ft2·°F/ hr·ft2·°F) BTU) 2 14.29 15.14 0.0669 14.95 2.5 17.86 18.71 0.0500 20.00 75 3 21.43 22.28 0.0400 25.00 Architectural 4 28.57 29.42 0.0307 32.57 Flat 2 15.87 16.72 0.0637 15.70 2.5 19.84 20.69 0.0456 21.93 40 3 23.81 24.66 0.0378 26.46 4 31.75 32.60 0.0289 34.60 5 INSULATION VALUES Core R-value per Nominal ASTM C518 42” Wide Panel Mean Temp Core (hr·ft2·°F/BTU) Panel (°F) Thickness Profile (in.) U-factor R-value w/o air films w/ air films (BTU/ (hr·ft2·°F/ hr·ft2·°F) BTU) 2 14.29 15.14 0.0721 13.87 2.5 17.86 18.71 0.0523 19.12 3 21.43 22.28 0.0432 23.15 75 4 28.57 29.42 0.0328 30.49 5 35.71 36.56 0.0267 37.45 CF Flute 6 42.86 43.71 0.0226 44.25 2 15.87 16.72 0.0692 14.45 2.5 19.84 20.69 0.0498 20.08 3 23.81 24.66 0.0410 24.39 40 4 31.75 32.60 0.0311 32.15 5 39.68 40.53 0.0252 39.68 6 47.62 48.47 0.0214 46.73 Core R-value per 36" Wide Panel ASTM C518 Panel Mean Temp Thickness (hr·ft2·°F/BTU) U-factor R-value Profile (°F) (in.) (BTU/ (hr·ft2·°F/ w/o air films w/ air films hr·ft2·°F) BTU) 3 Due to the deep profiling 0.0814 12.29 4 of the 7.2 Insul-Rib Panel, 0.0537 18.62 Insul-Rib 75 5 the C518 test cannot be 0.0395 25.32 used to determine thermal 6 0.0314 31.85 performance 6 INSULATION VALUES Nominal Core R-value per 42” Wide Panel Mean Temp Core ASTM C518 Panel Profile (°F) Thickness (hr·ft2·°F/BTU) U-factor (in.) w/o air films w/ air films (BTU/hr·ft2·°F) 3 10.83 11.68 0.0856 4 14.44 15.29 0.0654 ThermalSafe 5 18.05 18.90 0.0529 Wall 75 6 21.66 22.51 0.0444 7 25.27 26.12 0.0383 8 28.88 29.73 0.0336 Core R-value per 42” Wide Panel Core ASTM C518 Panel Mean Temp Thickness 2 U-factor R-value Profile (°F) (hr·ft ·°F/BTU) (in.) (BTU/ (hr·ft2·°F/ w/o air films w/ air films hr·ft2·°F) BTU) 2 14.29 15.07 0.0600 16.67 2.5 17.86 18.64 0.0490 20.41 3 21.43 22.21 0.0414 24.15 75 4 28.57 29.35 0.0318 31.45 5 35.71 36.49 0.0257 38.91 CFR Roof 6 42.86 43.64 0.0217 46.08 2 15.87 16.65 0.0567 17.64 2.5 19.84 20.62 0.0462 21.65 3 23.81 24.59 0.0390 25.64 40 4 31.75 32.53 0.0298 33.56 5 39.68 40.46 0.0241 41.49 6 47.62 48.40 0.0201 49.75 7 INSULATION VALUES Core R-value per 36" Wide Panel ASTM C518 Panel Mean Temp Thickness (hr·ft2·°F/BTU) U-factor R-value Profile (°F) (in.) 2 w/o air films w/ air films (BTU/ (hr·ft ·°F/ hr·ft2·°F) BTU) 1.5 10.71 11.56 0.0783
Load more

Recommended publications
  • Application Note AN-1057
    Application Note AN-1057 Heatsink Characteristics Table of Contents Page Introduction.........................................................................................................1 Maximization of Thermal Management .............................................................1 Heat Transfer Basics ..........................................................................................1 Terms and Definitions ........................................................................................2 Modes of Heat Transfer ......................................................................................2 Conduction..........................................................................................................2 Convection ..........................................................................................................5 Radiation .............................................................................................................9 Removing Heat from a Semiconductor...........................................................11 Selecting the Correct Heatsink........................................................................11 In many electronic applications, temperature becomes an important factor when designing a system. Switching and conduction losses can heat up the silicon of the device above its maximum Junction Temperature (Tjmax) and cause performance failure, breakdown and worst case, fire. Therefore the temperature of the device must be calculated not to exceed the Tjmax. To design a good
    [Show full text]
  • How Air Velocity Affects the Thermal Performance of Heat Sinks: a Comparison of Straight Fin, Pin Fin and Maxiflowtm Architectures
    How Air Velocity Affects The Thermal Performance of Heat Sinks: A Comparison of Straight Fin, Pin Fin and maxiFLOWTM Architectures Introduction A device’s temperature affects its op- erational performance and lifetime. To Air, Ta achieve a desired device temperature, Heat sink the heat dissipated by the device must be transferred along some path to the Rhs environment [1]. The most common method for transferring this heat is by finned metal devices, otherwise known Rsp as heat sinks. Base Resistance to heat transfer is called TIM thermal resistance. The thermal resis- RTIM tance of a heat sink decreases with . Component case, Tc Q Component more heat transfer area. However, be- cause device and equipment sizes are decreasing, heat sink sizes are also Figure 1. Exploded View of a Straight Fin Heat Sink with Corresponding Thermal Resis- tance Diagram. growing smaller. On the other hand, . device heat dissipation is increasing. heat sink selection criteria. Q RTIM, as shown in Equation 2. Therefore, designing a heat transfer The heat transfer rate of a heat sink, , . path in a limited space that minimizes depends on the difference between the Q = (Thot - Tcold)/Rt = (Tc - Ta)/Rt (1) thermal resistance is critical to the ef- component case temperature, Tc, and fective design of electronic equipment. the air temperature, Ta, along with the where total thermal resistance, Rt. This rela- This article discusses the effects of air tionship is shown in Equation 1. For Rt = RTIM + Rsp + Rhs (2) flow velocity on the experimentally de- a basic heat sink design, as shown in termined thermal resistance of different Figure 1, the total thermal resistance Therefore, to compare different heat heat sink designs.
    [Show full text]
  • Guide for the Use of the International System of Units (SI)
    Guide for the Use of the International System of Units (SI) m kg s cd SI mol K A NIST Special Publication 811 2008 Edition Ambler Thompson and Barry N. Taylor NIST Special Publication 811 2008 Edition Guide for the Use of the International System of Units (SI) Ambler Thompson Technology Services and Barry N. Taylor Physics Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 (Supersedes NIST Special Publication 811, 1995 Edition, April 1995) March 2008 U.S. Department of Commerce Carlos M. Gutierrez, Secretary National Institute of Standards and Technology James M. Turner, Acting Director National Institute of Standards and Technology Special Publication 811, 2008 Edition (Supersedes NIST Special Publication 811, April 1995 Edition) Natl. Inst. Stand. Technol. Spec. Publ. 811, 2008 Ed., 85 pages (March 2008; 2nd printing November 2008) CODEN: NSPUE3 Note on 2nd printing: This 2nd printing dated November 2008 of NIST SP811 corrects a number of minor typographical errors present in the 1st printing dated March 2008. Guide for the Use of the International System of Units (SI) Preface The International System of Units, universally abbreviated SI (from the French Le Système International d’Unités), is the modern metric system of measurement. Long the dominant measurement system used in science, the SI is becoming the dominant measurement system used in international commerce. The Omnibus Trade and Competitiveness Act of August 1988 [Public Law (PL) 100-418] changed the name of the National Bureau of Standards (NBS) to the National Institute of Standards and Technology (NIST) and gave to NIST the added task of helping U.S.
    [Show full text]
  • Is the Thermal Resistance Coefficient of High-Power Leds Constant? Lalith Jayasinghe, Tianming Dong, and Nadarajah Narendran
    Is the Thermal Resistance Coefficient of High-power LEDs Constant? Lalith Jayasinghe, Tianming Dong, and Nadarajah Narendran Lighting Research Center Rensselaer Polytechnic Institute, Troy, NY 12180 www.lrc.rpi.edu Jayasinghe, L., T. Dong, and N. Narendran. 2007. Is the thermal resistance coefficient of high-power LEDs constant? Seventh International Conference on Solid State Lighting, Proceedings of SPIE 6669: 666911. Copyright 2007 Society of Photo-Optical Instrumentation Engineers. This paper was published in the Seventh International Conference on Solid State Lighting, Proceedings of SPIE and is made available as an electronic reprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited. Is the Thermal Resistance Coefficient of High-power LEDs Constant? Lalith Jayasinghe*, Tianming Dong, and Nadarajah Narendran Lighting Research Center, Rensselaer Polytechnic Institute 21 Union St., Troy, New York, 12180 USA ABSTRACT In this paper, we discuss the variations of thermal resistance coefficient from junction to board (RӨjb) for high-power light-emitting diodes (LEDs) as a result of changes in power dissipation and ambient temperature. Three-watt white and blue LED packages from the same manufacturer were tested for RӨjb at different input power levels and ambient temperatures. Experimental results show that RӨjb increases with increased input power for both LED packages, which can be attributed to current crowding mostly and some to the conductivity changes of GaN and TIM materials caused by heat rise.
    [Show full text]
  • Thermal-Electrical Analogy: Thermal Network
    Chapter 3 Thermal-electrical analogy: thermal network 3.1 Expressions for resistances Recall from circuit theory that resistance �"#"$ across an element is defined as the ratio of electric potential difference Δ� across that element, to electric current I traveling through that element, according to Ohm’s law, � � = "#"$ � (3.1) Within the context of heat transfer, the respective analogues of electric potential and current are temperature difference Δ� and heat rate q, respectively. Thus we can establish “thermal circuits” if we similarly establish thermal resistances R according to Δ� � = � (3.2) Medium: λ, cross-sectional area A Temperature T Temperature T Distance r Medium: λ, length L L Distance x (into the page) Figure 3.1: System geometries: planar wall (left), cylindrical wall (right) Planar wall conductive resistance: Referring to Figure 3.1 left, we see that thermal resistance may be obtained according to T1,3 − T1,5 � �, $-./ = = (3.3) �, �� The resistance increases with length L (it is harder for heat to flow), decreases with area A (there is more area for the heat to flow through) and decreases with conductivity �. Materials like styrofoam have high resistance to heat flow (they make good thermal insulators) while metals tend to have high low resistance to heat flow (they make poor insulators, but transmit heat well). Cylindrical wall conductive resistance: Referring to Figure 3.1 right, we have conductive resistance through a cylindrical wall according to T1,3 − T1,5 ln �5 �3 �9 $-./ = = (3.4) �9 2��� Convective resistance: The form of Newton’s law of cooling lends itself to a direct form of convective resistance, valid for either geometry.
    [Show full text]
  • Arxiv:1311.4868V1 [Cond-Mat.Mes-Hall] 19 Nov 2013
    Anisotropic magneto-thermal transport and Spin-Seebeck effect J.-E. Wegrowe∗ and H.-J. Drouhin Ecole Polytechnique, LSI, CNRS and CEA/DSM/IRAMIS, Palaiseau F-91128, France D. Lacour Institut Jean Lamour, UMR CNRS 7198, Universit´eH. Poincarr´e,F -5406 Vandoeuvre les Nancy, France (Dated: August 21, 2021) Abstract The angular dependence of the thermal transport in insulating or conducting ferromagnets is derived on the basis of the Onsager reciprocity relations applied to a magnetic system. It is shown that the angular dependence of the temperature gradient takes the same form as that of the anisotropic magnetoresistance, including anomalous and planar Hall contributions. The measured thermocouple generated between the extremities of the non-magnetic electrode in thermal contact to the ferromagnet follows this same angular dependence. The sign and amplitude of the magneto- voltaic signal is controlled by the difference of the Seebeck coefficients of the thermocouple. PACS numbers: 85.80.Lp, 85.75.-d, 72.20.Pa arXiv:1311.4868v1 [cond-mat.mes-hall] 19 Nov 2013 ∗Electronic address: [email protected] 1 Exploiting the properties of heat currents in magnetic systems for data processing and storage is a decisive challenge for the future of electronic devices and sensors. Recent research efforts, in line with spintronics developments, focus more specifically on the properties of the spin degrees of freedom associated to the electric charges and heat currents [1]. Important series of experiments - the so-called spin-pumping and spin-Seebeck measurements - have been performed in this context [2{12]: a magneto-voltaic signal is observed at zero electric current on electrodes that are in thermal contact with a ferromagnet.
    [Show full text]
  • Some Thermal Resistance Values
    Some Thermal Resistance Values Assuming constant thickness of given material Substance R (1 inch) R (1cm) (imperial units) (metric units) Air (non-convecting) 6 0.42 Copper 3.7x10-4 2.6x10-5 Plywood 1.25 8.6x10-2 Glass 0.18 1.3x10-2 Brick 0.11 7.7x10-3 Concrete 0.14 1.0x10-2 Fiberglass batts 3.6 0.25 Polyurethane foam 6.3 0.43 McFarland pg 16-8 To obtain actual R value, multiply by number of inches/cm of thickness Typical R values for various structures Structure R value R value ft2hr°F/Btu m2K/W 2x4 wall with 11 1.94 fiberglass insulation 2x4 wall with 22 3.87 polyurethane foam insulation Ceiling with 11 in. 38 6.87 fiberglass batts Ceiling with 14 in. 49 8.63 fiberglass batts ex Example (imperial units) A homeowner has a total ceiling area of (50 ft)x(20 ft) = 1000 ft2 Currently the attic is insulated with fiberglass insulation having an R value of 8 (“R8”) Question: If the winter temperature is 32°F and the house interior is at 72°F, how much heat is lost through the ceiling assuming no air leakage (just conduction) Q Q 1 1 Btu From ∆T = R we have = A∆T = (1000)(40) = 5000 At t R 8 hr Btu 1055J 1hr Convert 5000 = 1465W = 1.47kW to kW: hr 1Btu 3600s Question: If the homeowner increases to R38 insulation, by what fraction will the heat loss decrease? Heat loss is proportional to 1/R value, therefore the loss will decrease by a fraction (1/38)/(1/8)= 0.21 Role of Fiberglass insulation e.g.
    [Show full text]
  • Lifetime Modelling Issues of Power Light Emitting Diodes
    energies Article Lifetime Modelling Issues of Power Light Emitting Diodes János Hegedüs, Gusztáv Hantos and András Poppe * Department of Electron Devices, Budapest University of Technology and Economics, 1117 Budapest, Hungary; [email protected] (J.H.); [email protected] (G.H.) * Correspondence: [email protected]; Tel.: +36-1-463-2721 Received: 27 May 2020; Accepted: 23 June 2020; Published: 1 July 2020 Abstract: The advantages of light emitting diodes (LEDs) over previous light sources and their continuous spread in lighting applications is now indisputable. Still, proper modelling of their lifespan offers additional design possibilities, enhanced reliability, and additional energy-saving opportunities. Accurate and rapid multi-physics system level simulations could be performed in Spice compatible environments, revealing the optical, electrical and even the thermal operating parameters, provided, that the compact thermal model of the prevailing luminaire and the appropriate elapsed lifetime dependent multi-domain models of the applied LEDs are available. The work described in this article takes steps in this direction in by extending an existing multi-domain LED model in order to simulate the major effect of the elapsed operating time of LEDs used. Our approach is based on the LM-80-08 testing method, supplemented by additional specific thermal measurements. A detailed description of the TM-21-11 type extrapolation method is provided in this paper along with an extensive overview of the possible aging models that could be used for practice-oriented LED lifetime estimations. Keywords: power LED measurement and simulation; life testing; reliability testing; LM-80; TM-21; LED lifetime modelling; LED multi-domain modelling; Spice-like modelling of LEDs; lifetime extrapolation and modelling of LEDs 1.
    [Show full text]
  • Thermal Resistance Measurements
    NiST PUBLICATIONS / W \ NIST SPECIAL PUBLICATION 400-86 U.S. DEPARTMENT OF COMMERCE /National Institute of Standards and Technology aoo-86 1990 C.2 NATIONAL INSTITUTE OF STANDARDS & TECHNOLOGY Researdi Infcmnatiofi Center Gakhersburg, MD 20899 DATE DUE Demco. Inc. 38-293 Semiconductor Measurement Technology: Thermal Resistance Measurements Frank F. Oettinger and David L. Blackburn Semiconductor Electronics Division Center for Electronics and Electrical Engineering National Engineering Laboratory National Institute of Standards and Technology Gaithersburg, MD 20899 July 1990 U.S. DEPARTMENT OF COMMERCE, Robert A. Mosbacher, Secretary NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY, John W. Lyons, Director National Institute of Standards and Technology Special Publication 400-86 Natl. Inst. Stand. Technol. Spec. Publ. 400-86, 78 pages (July 1990) CODEN: NSPUE2 U.S. GOVERNMENT PRINTING OFFICE WASHINGTON: 1990 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402-9325 Semiconductor Measurement Technology: THERMAL RESISTANCE MEASUREMENTS Table of Contents Page I. POWER TRANSISTORS 1 Introduction 1 The Concept of Thermal Resistance 2 The Effect of Nonuniform Junction Temperature on the Definition of Rqjr ... 2 The Variation of Rqjr with Device Operating Conditions (/c?^CJs) 3 General Methods for Measuring Device Temperature 7 Control of the Thermal Environment 13 Selection of Temperature-Sensitive Electrical Parameters 14 Measurement of Temperature- Sensitive Electrical Parameters 17 Safe-Operating- Area Limits 21 DC Thermal Limit 21 Second Breakdown Limit 26 Relating the Chip Temperature to the Measured Temperature 29 Determination of Area of Power Generation and Peak Junction Temperature . 29 Detection of Onset of Current Constrictions 33 Reasons for Measuring Temperature 33 Measurement of Integrated Power Devices 38 Power Transistor Thermal Standardization Activities 41 II.
    [Show full text]
  • How to Calculate “R” Values
    TECHNICAL INFORMATION Bulletin #01 February 2018 How to calculate “R” Values “R” value is used to designate the parallel surfaces and means the Where r1 = uninsulated pipe radius thermal resistance of an object. R-value increases proportionally to in inches 01 The higher the R-value, the higher the thickness. r2 = insulated pipe radius in inches thermal resistance and thus, Cylindrical Objects insulating value. k = thermal conductivity The simple equation for R-value Flat Objects r does does not hold true for r ln 2 2 ( r ( R-values for flat objects such as cylindrical objects like pipe R= 1 for sheet insulation are easy to insulation. For these objects, k calculate. It is simply the thickness the heat flow is not the simple of the insulation in inches divided straight-through heat flow found Based on this equation, the by the thermal conductivity of the with flat objects. Instead, the heat R-value gets larger as the insulation. For example, a two flow is radial because the inner insulation thickness increases but inch thick sheet of insulation with surface area is much smaller than also as the pipe sizes gets smaller. a thermal conductivity of 0.25 outer surface area and the R-value For example, 1" thick insulation Btu•in/h•ft2•°F has an R-value calculation must take this into will have a higher R-value on a 1" equal to 2 divided by 0.25 or 8.0. account. As a result, the equation pipe than it will on a 3" pipe. As a for the R-value of cylindrical result, one must always consider This simple equation is true for any objects is as follows: the pipe size and insulation flat, homogeneous material with thickness to determine the R-value of insulation on a pipe.
    [Show full text]
  • The Bridge Between the Device and System of Thermoelectric Power
    Electronic Supplementary Material (ESI) for Energy & Environmental Science. This journal is © The Royal Society of Chemistry 2020 1 Supporting Information for 2 System efficiency and power: the bridge between the device and 3 system of thermoelectric power generator 4 Kang Zhu1,2, Biao Deng1,2, Pengxiang Zhang1,2, Hee Seok Kim3, 5 Peng Jiang4 and Weishu Liu1,2* 6 1 Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, 7 Guangdong 518055, China 8 2 Shenzhen Engineering Research Center for Novel Electronic Information Materials and Devices, Southern 9 University of Science and Technology, Shenzhen, Guangdong 518055, China 10 3 Department of Mechanical Engineering, University of South Alabama, Mobile, Alabama 36688, USA 11 4 State Key Laboratory of Catalysis, CAS Center for Excellence in Nanoscience, Dalian Institute of Chemical 12 Physics, Chinese Academy of Sciences, Dalian, Liaoning 116023, China 13 *Email: [email protected] 14 15 1. Derivation of the Governing Equation of a Thermoelectric Process 16 The earlier works by Callen1 and Domenicali2 are reviewed, to present a complete derivation 17 of the differential equation which governs the temperature distribution in a thermoelectric leg in 18 steady state. The particle current density, the energy current density and the entropy current 19 density within a TE leg are respectively denoted as 퐽⃗, 푊⃗ and 푆⃗. The heat current density is by 20 definition written as 푞⃗ = 푇푆⃗. In a steady-state process the following conditions should be met, 21 ∇ ∙ 푊⃗ = 0#(푆1) 22 ∇ ∙ 퐽⃗ = 0#(푆2) 23 ∇ ∙ 푆⃗ = 푆̇ #(푆3) 24 where 푆̇ is the entropy production rate per unit volume.
    [Show full text]
  • Recommended Practice for the Use of Metric (SI) Units in Building Design and Construction NATIONAL BUREAU of STANDARDS
    <*** 0F ^ ££v "ri vt NBS TECHNICAL NOTE 938 / ^tTAU Of U.S. DEPARTMENT OF COMMERCE/ 1 National Bureau of Standards ^^MMHHMIB JJ Recommended Practice for the Use of Metric (SI) Units in Building Design and Construction NATIONAL BUREAU OF STANDARDS 1 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 pro- mote public safety. The Bureau consists of the Institute for Basic Standards, the Institute for Materials Research, the Institute for Applied Technology, the Institute for Computer Sciences and Technology, the Office for Information Programs, and the Office of Experimental Technology Incentives Program. THE ENSTITUTE FOR BASIC STANDARDS provides the central basis within the United States of a complete and consist- ent system of physical measurement; coordinates that system with measurement systems of other nations; and furnishes essen- tial services leading to accurate and uniform physical measurements throughout the Nation's scientific community, industry, and commerce. The Institute consists of the Office of Measurement Services, and the following center and divisions: Applied Mathematics — Electricity
    [Show full text]