NATIONAL BUREAU OF STANDARDS REPORT

7775

THERMAL CONDUCTIVITY OF A SPECIMEN OF

CHROMIUM-COPPER ALLOY

by

Thomas W. Watson and Henry E. Robinson

Report to the

U.S. Naval Ordnance Laboratory

White Oak

Silver Spring, Maryland

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
THE NATIONAL BUREAU OF STANDARDS

Functions and Activities

The functions of the National Bureau of Standards are set forth in the Act of Congress, March 3, 1901, as amended by Congress in Public Law 619, 1950. These include the development and maintenance of the national standards of measurement and the provision of means and methods for making measurements consistent

with these standards; the determination of physical constants and properties of materials; the development of

methods and instruments for testing materials, devices, and structures; advisory services to government agencies on scientific and technical problems; invention and development of devices to serve special needs of the

Government; and the development of standard practices, codes, and specifications. The work includes basic

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and various consultation and information services. Research projects are also performed for other government

agencies when the work relates to and supplements the basic progratn of the Bureau or when the Bureau's

unique competence is required. The scope of activities is suggested by the listing of divisions and sections on the inside of the back cover.

Publications

The results of the Bureau's research are published ei.ther in thp Bureau's own series of publications or

in the journals of professional and scientific societies. The Bureau itself publishes three periodicals available from the Government Printing Office: The Journal of Research, published in four separate sections,

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and Technical Notes. A complete listing of the Bureau's publications can be found in National Bureau of Standards Circular

460, Publications of the National Bureau of Standards, 1901 to June 1947 ($1.25), and the Supplement to National Bureau of Standards Circular 460, July 1947 to June 1957 (S1..50), and Miscellaneous Publication 240,

July 1957 to June 1960 (Includes Titles of Papers Published in Outside Journals 1950 to 1959) ($2.25); available from the Superintendent of Documents, Government Printing Office, Washington 25, D. C.
NATIONAL BUREAU OF STANDARDS REPORT

MBS PROJECT MBS REPORT

1006-30-10642 January 7, 1963 7775

THERMAL CONDUCTIVITY OF A SPECIMEN OF

CHROMIUM-COPPER ALLOY

by

T. W. Watson and H. E. Robinson

Heat Transfer Section

Building Research Division

Report to the

U.S. Naval Ordnance Laboratory

Code MSD-22

White Oak

Silver Spring, Maryland

IMPORTANT NOTICE NATIONAL BUREAU OF STAN

for use within the Government. Be and review. For this reason, the p whole or in part, is not authorize Bureau of Standards, Washington

the Report has been specifically pri

accounting documents intended Approved for public release by the 5i ected t0 additional evaluation n i _ T • it . n

sting of this Report, either in Director of the National Institute of )ffice of the Director, National Standards and Technology (NIST) J Government agency for which on October 9, 2015. es for its own oSe.

U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS
-2 -

Temperatures along the specimen were indicated by seven thermocouples located symmetrically about the longitudinal center of the specimen, spaced approximately 3.51 cm apart, with one additional thermocouple

near the bottom end of the specimen® Thermocouples were similarly located in almost exactly corresponding longitudinal positions on the guard

tube*

The guard tube was equipped near its lower end with an external

circumferential electric heater, as shown. The guard tube was cooled at

the top by means of a copper-tube coil soldered circumferentially at a position corresponding in effect to that of the specimen coolant well.

Coolant (water at 40°C) was pumped through the guard coil and specimen

well in series connection, as shown.

The electrical heater for the specimen consisted of a porcelain

cylinder 1*25 cm in diameter and 5.2 cm long, threaded longitudinally

with 26-gage nichrome heater wire. Its resistance was approximately 22

ohms. Current was brought to the heater through relatively large heater

leads, to which separate potential leads were connected at the point

where they entered the porcelain core. The heater was energized by an

adjustable constant-voltage d-c source. Heater current and voltage

drop measurements were made using standard resistors and the high precision manual potentiometer used for thermocouple observations. The

guard was heated with alternating current governed by a sensitive temperature controller actuated by the guard temperature at a selected

position*

The thermocouples were made from calibrated chromel and alumel

26-gage wires, welded by gas-oxygen flame to form a butt joint about

0,042 cm in diameter.

The thermocouple junctions were pressed into transverse grooves

0*04 cm wide by 0.05 cm deep and 0.6 cm in length in the convex surface of the bar and tightly secured by hammering the metal around the

groove. The thermocouple leads were individually insulated electrically

with fiberglass sleeving, and brought out in the powder insulation in

the same transverse plane as the junction (one wire in each direction)

forming a 2 -cm circle. The wires were brought out through the powder

insulation near the guard tube. The thermocouples in the guard tube

were electrically welded to form a spherical junction about 0.10 cm in

diameter* The junctions in the guard were inserted into radiallydrilled holes 0,11 cm in diameter and 0.17 cm deep, and tightly secured

by punch-pricking the metal around the hole. The wires were similarly

brought out through the powder insulation. The longitudinal positions

of the thermocouple junctions were taken as those of the centers of the

grooves, or of the drilled holes, measured to the nearest 0*01 cm with

a laboratory cathetometer

.
- 3 -

After installation of the specimen, the space between it and the

guard tube was filled with diatomaceous earth powder insulation, which

also was used to insulate the space surrounding the guard tube. The

tests were conducted with the insulation exposed to atmospheric air.

In principle, if there were no heat exchange between the specimen

and its surroundings, the conductivity could be determined from the

measured power input to the specimen and the average temperature gradient for each of the six spans along the specimen, all of uniform known

cross-sectional area. In practice, a perfect balance of temperatures

between the bar and guard all along their lengths is not possible because of differences in their temperature coefficients of conductivity,

and the effect of the outward heat losses of the guard. In addition to

heat exchanges between the bar and guard from this cause, a relatively

insignificant longitudinal flow of heat occurs in the powder insulation

surrounding the specimen, and the contribution of the specimen to this

heat flow must depend somewhat on the bar-to-guard temperature unbalance.

In order to evaluate the heat flow in the bar at the center points

of each of the six spans, a partly empirical procedure was used. Two

steady-state test-runs were made with slightly different bar and guard

temperatures and power inputs. In the two tests, the heat flow and the

observed temperature drop from end to end of a given span differed, as

did also the approximate integral with respect to length of the observed

temperature differences between bar and guard, summed from the hot end

of the bar to the span center point. It is thus possible to write for

each span two equations (one for each test-run) of the form

AkAt

+

Ax

fS Q

where A is the cross-sectional area of the specimen,

k is the specimen conductivity at the mean temperature of the

span.

At is the temperature drop from end to end of the span,

Ax is the length of the span,

fS represents the total net heat loss from the bar from its bottom

end at the heater to the midpoint, x, of the given span, expressed as the product of S, which is the integral J

V Q(tbar " tgUard)^x » anc^ an average heat transfer coefficient f for the

thermal path from bar to guard.

Q is the measured power input to the specimen heater.
COOLANT

REMOVABLE TRIVET

SUPPORT

NOTES

1. DIMENSIONS IN

CENTIMETERS

2. X INDICATES A

THERMOCOUPLE

POSITION

3. MAIN THERMOCOUPLES

ON BAR ARE PLACED

3.51 CM. APART

CONTAINER

GUARD CYLINDER

SPECIMEN

INSULATION

BAR HEATER

GUARD HEATER

APPARATUS FOR MEASURING THE THERMAL

CONDUCTIVITY OF METALS

Figure 1
CHROMIUM

-

COPPER

ALLOY

O O o

Jo IT) fO cvj

ro fo rd

^

o

iO

<0 CsS

iZ

o

o

<0

0o UUO/M ‘ AllAllOnQNOO IVIrtUBHl

200

300

ro

TEMPERATURE

U. S. DEPARTMENT OF COMMERCE

Luther H. Hodges, Secretary

NATIONAL BUREAU OF STANDARDS

A. V. Astin, Director THE NATIONAL BUREAU OF STANDARDS

The scope of activities of the National Bureau of Standards at its major laboratories in Washington, D.C., and

Boulder, Colorado, is suggested in the following listing of the divisions and sections engaged in technical work.

In general, each section carries out specialized research, development, and engineeringfin the field indicated by

its title. A brief description of the activities, and of the resultant publications, appears on the inside of the

front cover. WASHINGTON, I), C.

Electricity. Resistance and Reactance. Electrochemistry. Ele<Hrical Instruments. Magnetic Measurementa

Dielectrics. High Voltage.

Metrology. Photometry and Colorimetry. Refractometry. Photographic Research. Length. Engineering Metrology.

Mass and Scale. Volumetry and Densimetry.

Heat. Temperature Physics. Heat Measurements. Cryogenic Physics. Equation of State. Statistical Physics.

Radiation Physics. X-ray. Radioactivity. Radiation Theory, High Enei*gy Radiation. Radiological Equipment.

Nucleonic Instrumentation. Neutron Physics.

Analytical and Inorganic Chen^stry. Pure Substances. Spectrochemistry, Solution Chemistry. Standard Refer* ence Materials. Applied Analytical Research, Crystal Chemistry.

Mechanics. Sound. Pressure and Vacuum. Fluid Mechanics. Engineering Mechanics. Rheology. Combustion

Controls.

Polymers. Macromolequles: Synthesis and Structure. Polymer Chemistry. Polymer Physics. Polymer Characterization. Polymer Evaluation and Testing. Applied Polymer Standards and Research. Dental Research.

Metallurgy. Engineering Metallurgy. Microscopy and Diffraction. Metal Reactions. Metal Physics. Electrolysis

and Metal Deposition.

Inorganic Solids. Engineering Ceramics. Class. Solid State Chemistry. Crystal Growth. Physical Properties.

Crystallography.

Building Research. Structural Engineering. Fire Research. Mechanical Systems. Organic Building Materials.

Codesand Safety Standards. Heat Transfer. Inorganic Building Materials. Metallic Building Materials.

Applied Mathematics. Numerical Analysis. Computation. Statistical. Engineering. Mathematical Physics. Operations Research.

Data Processing Systems. Components and Techniques. Computer Technology. Measurements Automation.

Engineering Applications. Systems Analysis.

Atomic Physics. Spectroscopy. Infrared Spectroscopy. Far Ultraviolet Physics. Solid State Physics. Electron

Physics. Atomic Physics. Plasma Spectroscopy.

Instrumentation. Engineering Electronics. Electron Devices. Electronic Instrumentation. Mechanical Instru- ments. Basic Instrumentation.

Physical Chemistry. Thermochemistry. Surface Chemistry. Organic Chemistry. Molecular Spectroscopy. Elementary Processes. Mass Spectrometry. Photochemistry and Raciation Chemistry.

Office of Weights and Measures. BOULDER, COLO.

Cryogenic Engineering Laboratory. Cryogenic Equipment. Cryogenic Processes. Properties of Materials. Cryogenic Technical Services.

CENTRAL RADIO PROPAGATION LABORATORY

lonospliere Research and Propagation. Low Frequency and Very Lofcv Frequency Research. Ionosphere Research. Prediction Services. Sun-Earth Relationships. Field Engineering. Radio Warning Services. Vertical

Soundings Research.

Radio Propagation Engineering. Data Reduction Instrumentation. Radio Noise. Tropospheric Measurements.

Tropo^jheric Analysis. Propagation-Terrain Effects. Radio-Meteorology. Lower Atmosphere Physics.

Radio Systems. Applied Electromagnetic Theory* High Frequency and Vbry High Frequency Research. Fre- quency Utilization. Modulation Research. Antenna Research. Radiodeterminajtion.

Upper Atmosphere and Space Physics. Upper Atmosphere and Plasma Physics. High Latitude Ionosphere

Physics. Ionosphere and Exosphere Scatter. Airglow and Aurora. Ionospheric Radio Astronomy.

RADIO STANDARDS LABORATORY

Radio Physics. Radio Broadcast Service. Radio and Microwave Materials. Atomic Frequency and Time-Interval

Standards. Radio Plasma. Millimeter-Wave Research.

Circuit Standards. High Frequency Electrical Standards. High Frequency Calibration Services. High Frequency

Impedance Standards. Microwave Calibration Services. Microwave Circuit Standards. Low Frequency Calibration

Services.