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NBSIR 79-1603 


at the 


1 July - 31 December 1978 










NBSIR 79-1603 


at the 


Thermophysical Properties Division 
National Engineering Laboratory 
National Bureau of Standards 
Boulder, Colorado 80303 

Progress Report for the Period 

1 July - 31 December 1978 

U.S. DEPARTMENT OF COMMERCE, Juanita M. Kreps, Secretary 

Sidney Harman, Under Secretary 

Jordan J. Baruch, Assistant Secretary for Science and Technology 


Prepared for: 

American Gas Association, Inc. 

1515 Wilson Boulevard 
Arlington, Virginia 22209 

LNG Density Project Steering Committee 

(in cooperation with the American Gas Association, Inc.) 

Pipeline Research Committee 
(American Gas Association, Inc.) 

Gas Research Institute 
10 West 35th Street 
Chicago, Illinois 60616 

U. S. Department of Commerce 
Maritime Administration 
Washington, DC 20235 

U. S. Department of Commerce 
National Bureau of Standards 
National Engineering Laboratory 
Boulder, Colorado 80303 

U. S. Department of Commerce 
National Bureau of Standards 
Office of Standard Reference Data 
Washington, DC 20234 

U. S. Department of Commerce 
National Bureau of Standards 
Office of International Standards 
Washington, DC 20234 

LNG Custody Transfer Measurements Supervisory Committee 

National Aeronautics and Space Administration 
Lewis Research Center 
Cleveland, Ohio 44135 


The objective of this report is to: 

1. provide all sponsoring agencies with a semiannual report on the 
activities of their individual programs; 

2. inform all sponsoring agencies on related research being conducted 
at the Themophys ica 1 Properties Division; 

3. provide a uniform reporting procedure which should maintain and 
improve communication while minimizing the time, effort and 
paperwork at the cost center level. 

The work is supported by NBS and seven other agencies and represents the 
collective expenditure of $400,000 during the 6-month reporting period. The 
contents of this report augment quarterly progress meetings for certain of 
our sponsors and provide a perspective which is missing when the parts are 
viewed individually. Distribution of this document is limited and intended 
.primarily for the supporting agencies. Data or other information must be 
considered preliminary, subject to change and unpublished, and therefore not 
for citation in the open literature . 

During this reporting period we have issued the first supplement to the 
" LNG Material and Fluids" Users Manual. 

Key words: Cryogenics; liquefied natural gas; measurement; methane; 

properties; research. 


Cost Center 


I . 




(Gas Research Institute; American Gas 
Association, Inc.; NASA Lewis Research 






(NBS-Of f ice of Standard Reference Data) 



c ) 







(NBS; NBS-Office of Standard Reference 
Data; GRI) 






(LNG Density Project Steering Committee - 



f ) 


7363430 , 


II . 


a ) 

Administration; LNG Custody Transfer 
Measurements Supervisory committee 









Research Committee - AGA) 



c ) 

Association, Inc.; Gas Research Institute 



d ) 

Research Committee - AGA) 



Ill . 



METHANE (American Gas Association, Inc.; 
Gas Research Literature) 




CONTENTS (continued) 

(Maritime Administration; American Gas 
Association, Inc.; Gas Research Institute; 
NBS-Office of Standard Reference Data) 

(American Gas Association, Inc.; NBS- 
Office of International Standards; 
NBS-Thermophys ical Properties Division) 





7364574 , 








1 . 

Title . 


Principal Investigators . R. D. Goodwin, H. M. Roder, G. C. Straty, 

W. M. Haynes, R. D. McCarty, D. E. Oilier, and B. A. Younglove 

2 . Cost Center Numbers . 7360574, 7360548 

3. Sponsor Project Identification . Gas Research Institute Grant No. 
5010-362-0019 and American Gas Association, Inc., Project BR-50-10. 
National Aeronautics and Space Administration, Lewis Research Center, 
Purchase Order C-78014-C. 

4. Introduction . Accurate phase equilibrium, equation of state (PVT), and 
thermodynamic properties data are needed to design and optimize gas 
separation and liquefaction processes and equipment, and for mass and 
heat transfer calculations. Accurate data for the pure components and 
selected mixtures of hydrocarbon systems will permit developing 
comprehensive accurate predictive calculation methods which take into 
account the dependence of the thermophysical properties of mixtures on 
the composition, temperature, and density. 

This project will provide comprehensive accurate thermophysical 
properties data and predictive calculation methods for compressed and 
liquefied hydrocarbon gases and their mixtures to support the 
development of LNG technology at NBS and throughout the fuel gas 
industry. It will also serve as the base for a comprehensive mixtures 
prediction methodology. 

5. Objectives or Goals . The objectives of our work are the determination 
of comprehensive accurate thermophysical properties data and predictive 
calculation methods for the major pure components (methane, ethane, 
propane, butanes, and nitrogen) and selected mixtures of liquefied 
natural gas and hydrocarbon mixtures at temperatures between 80 K and 
320 K and at pressures up to 35 MPa (5000 psi). Our goal is to provide 
a range and quality of data that will be recognized as definitive or 
standard for all foreseeable low temperature engineering calculations. 

6. Background . Liquefied natural gas is expected to supply an increasing 
percentage of the United States' future energy requirements. It is 
likely that massive quantities of liquefied natural gas will be imported 
during the years 1978 - 1990. Ships and importation terminals are being 
built for transporting, storing, and vaporizing liquefied natural gas 
for distribution. Accurate physical and thermodynamic properties data 
for compressed and liquefied natural gas and hydrocarbon mixtures are 
needed to support these projects. For example, accurate compressibility 
and thermodynamic properties data are needed to design and optimize 
liquefaction and transport processes; accurate data for the heating 
value, which for liquefied natural gas mixtures depends on the total 
volume, the density, and the composition, are needed to provide a basis 
for equitable custody transfer. Accurate mixture data prediction 
methods are needed for use in automated heat transfer calculations. 

Accurate thermodynamic properties data for liquefied gas mixtures must 
be based on precise compressibility and calorimetric measurements; 
compressibility data give the dependence of thermodynamic properties on 
pressure and density (at fixed temperatures); calorimetric data give the 
dependence of thermodynamic properties on temperature (at fixed 
pressures and densities). It is impossible, however, to perform enough 
compressibility and calorimetric measurements directly on multicomponent 
mixtures to permit accurate interpolation of the data to arbitrary 
compositions, temperatures and pressures. Instead, thermodynamic 
properties data for multicomponent mixtures must usually be predicted 


(extrapolated) from a limited number of measurements on the pure 
components and their binary mixtures. This project was initiated to 
provide the natural gas and aerospace industries with comprehensive 
accurate data for pure compressed and liquefied methane, the most 
abundant component in LNG mixtures. We have published National Bureau 
of Standards Technical Note 653, "Thermophysical Properties of Methane, 
From 90 to 500 K at Pressures to 700 Bar," by Robert D. Goodwin (April 
1974), and National Bureau of Standards Technical Note 684, "Thermophys- I 
ical Properties of Ethane, From 90 to 600 K at Pressures to 700 Bar," by 
Robert D. Goodwin, H. M. Roder, and G. C. Straty (August 1976). These 
reports contain the most comprehensive and accurate tables available for 
the thermophysical properties of pure gaseous and liquid methane and 
ethane, and provide an accurate basis for calculating thermophysical 
properties data for LNG and other hydrocarbon mixtures. 

7 . Program and Results . 

7.1 Propane, PVTx and Dielectric Constant Measurements -- W. M. Haynes j 

The experimental measurements of the densities of liquid mixtures of LNG 
components have been completed. The LNG density project used the same 
apparatus that is now being employed for PVT and dielectric constant 
measurements on propane. A summary of the LNG density project is given 
in the report for cost center 7361574. 

After testing the dead weight gauge measurement system, PVT measurements 
have been carried out for liquid propane at pressures to 360 bars along 
three isotherms at 146, 160, and 178 K (approximately 14 data points per . 
isotherm) . These data have been compared with the calculated values 
from the equation of state for propane developed by R. D. Goodwin. The 1 
maximum difference between the calculated and experimental densities was | 
0.07% while the average deviation was 0.02%. No problems were 
encountered in using the apparatus at high pressures. 

This apparatus utilizes a magnetic suspension densimeter, which is based 
on an application of Archimedes' principle. The uncertainty in the 
measured density depends directly upon the uncertainty in the 
determination of the volume of the magnetic float. The volume of the 
float changes with pressure. Thus measurements have been carried out by 
H. M. Ledbetter of our division to determine the bulk modulus of the 
float material (barium ferrite) as a function of temperature between 76 
and 300 K. These measurements demonstrated that the change in the 
volume of the float is less than 0.03% for a pressure change of 
360 bars. (The bulk modulus (or compressibility coefficient) of barium 
ferrite changes approximately 2% from 76 to 300 K. This corresponds to 
a volume change of less than 0.001% for a pressure of 500 bars. For all 
practical purposes it can be assumed that the bulk modulus of barium 
ferrite is independent of temperature over the temperature range of the 
propane measurements.) 

One of the coaxial leads to the capacitor used in the dielectric 
constant measurements broke when an effort was being made to remove a 
short to ground from the capacitor cylinder to which this coaxial cable 
was connected. The apparatus must be disassembled and the coaxial cable 
replaced . 

7.2 Calculational Methods — R. D. McCarty 

Work is continuing, at a partial staff-year level, on the extension and 
optimization of the corresponding states method to mixtures of methane 
with nitrogen and other fluids. The transformation of the methane 
surface to N 2 , C>2' Ar > H 2 anc ^ C 2 H 4 ^ as been accomplished and 
the development work on the transformation function itself has begun. | 


We have determined that the transformation function previously used for 
liquid density near saturation is inadequate for a broader range of 
pressure and temperature. Initial efforts in finding a new function are 

7.3 Propane, Specific Heat Data -- R. D. Goodwin 

This project is complete and the results published in "Specific Heats of 
Saturated and Compressed Liquid Propane," by R. D. Goodwin, J. Res. Nat. 
Bur. Stand. (U.S.) 83, 449-58 (Sep-Oct 1978). 

7.4 Butane, Preliminary Thermophysical Properties Data -- R. D. Goodwin 

The objective is to prepare provisional tables of thermodynamic 
properties of normal and isobutane, using available physical properties 
data. In this work we expect to discover those areas of properties data 
most in need of further experimental measurements. 

In general, there is an abundance of quite inconsistent data from 
different laboratories, requiring tedious weightings, selections, and 
eliminations. There are few data for liquid butanes at LNG 
temperatures . 

Satisfactory formulations have been developed for the virial equation, 
the saturated liquid densities, specific heats for the saturated liquid 
below the boiling point, and for the ideal gas thermodynamic functions 
for both fluids. 

By thermal loops, in a procedure first developed by W. T. Ziegler, we 
have derived new "data" (where none existed) from the triple- to the 
boiling-point for vapor pressures, densities of the saturated vapor, and 
for heats of vaporization. The vapor-pressure equation has been 
adjusted to include these new data, and a provisional description has 
been developed for the heats of vaporization up to the critical point. 

Manuscripts for reports on the equation of state and provisional tables 
of thermodynamic properties for both n-butane and i-butane are complete 
and in the final stages of the NBS review process. They will be 
published as NBS Interagency reports. 

The work on isobutane was done sooner than planned because of a 
Department of Energy funded experimental project on that fluid which 
will be used as a geothermal working fluid. The latter work is being 
done at NBS-Gaithersburg and the two projects will be done on a 
collaborative basis so that the resulting 'final' tables will serve both 
projects. The need for measurements to be made on i-butane at Boulder 
will be, consequently, reduced greatly. 

7.5 Pure Nitrogen and Nitrogen-Methane PVTx Property Measurements — 

G. C. Straty and D. E. Diller 

Gas expansion PVT measurements on pure compressed and liquefied nitrogen 
have been completed. About 300 measurements were made at 21 densities 
in the range 11.2 - 28.4 mol/L, 80 - 270 K, 1 - 350 bars. These 
measurements were made to provide more accurate pure component data for 
an accurate mathematical model of the PVT properties of nitrogen-methane 
mixtures . 

Twelve isochoric gas-expansion PVT runs have been made on a gravimetri- 
cally prepared 50.115 mole % nitrogen-49.885 mole % methane mixture in 
the T, P, p range 82 - 320 K, 2 - 350 bar, 11 - 28.6 mol/L. The 
measurements are being compared with the extended corresponding states 
model (R. D. McCarty, NBSIR 77-867 (Oct 1977), which was previously 


optimized to saturated liquid density measurements on this mixture at 
temperatures below 140 K. Differences between calculated and measured 
densities range from several tenths percent at low temperatures and high 
densities to several percent near the critical temperature (~ 161 K) and 
critical density (~ 10.5 mol/L) . About eight more measurement runs are 

7.6 Sound Velocity of Propane — B. A. Younglove 

New measurements of the sound velocity of propane have been initiated. 

We will evaluate the performance of the sound velocity approach in 
liquid propane at 100 K to see if the previous geometry is satisfactory. 
Drawings were made for a new configuration of spacer length twice the 
old length in case the former arrangement does not work. Calculations 
for dispersion from correlations available in the literature indicate 
that this should not be a problem. This and other features of the 
proposed measurements were recently discussed during a visit by Bruce 
Gammon of DoE , Bartlesville, Oklahoma, an expert in the field of sound 
velocity measurements. We have installed and tested a new vacuum jacket 
for the sound velocity cryostat which allows much more convenient 
dismantling of the system. The computer programming necessary for 
experimental sound velocity measurement has commenced. We have a 
computer file for computation of propane density from measured values of 
temperature and pressure, and a file for computation of sound velocity 
from a measurement of frequency using the information obtained from the 
previously mentioned calculation. The latter file is not in complete 
form. We will next work on checking the system as mentioned above for 
general behavior in liquid propane. Also we will check the sample 
holder system for temperature gradients, temperature measurement 
accuracy and other features required for proper measurement of sound 
velocity . 

8. Problem Areas . None. 

9. Level of Effort . July 1 - December 31, 1978. 

Staff-years expended 

Equipment and/or Services Purchased 

Approximate expenditures, total 

10. Future Plans. 


11 . 2K$ 
9 6 . 4K$ 

Objectives and Schedule: Quarter 1 2 

Evaluate and optimize promising 

calculation methods for the 

thermodynamic properties of 
methane-nitrogen mixtures. 

Measure, analyze and report PVT and 
dielectric constant data for propane. 

Publish provisional tables of thermo- 
dynamic properties for the butanes 
and develop an accurate equation of 
state . 

Measure, analyze and report sound 
velocity data for propane. 


Title . FLUID transport properties 

Principal Investigator . Howard J. M . Hanley- 
Cost Center Number. 7362290 

Sponsor Project Identification . NBS-Office of Standard Reference Data 

Introduction . Methods for predicting the transport properties of fluid 
mixtures are unreliable and data are scarce. Prediction methods are 
needed, however, to supply the necessary design data needed to increase 
efficiency and reduce costs. 

Objectives or Goals . The long range or continuing goal of the program 
is to perform a systematic study of the theories and experimental 
measurements relating to transport properties, specifically the 
viscosity and thermal conductivity coefficients, of simple mixtures over 
a wide range of experimental conditions. The specific objectives of the 
program include: 1) the systematic correlation of the transport 

properties of simple binary mixtures and the development of prediction 
techniques, 2) development of a mixture theory for the dilute gas region 
and the dense gas and liquid regions, 3) extension of the theory and 
prediction techniques to multicomponent systems, and 4) suggested 
guidelines for future areas of experimental work. 

Background . A continuing program has successfully expanded the state- 
of-the-art of transport phenomena for pure fluids. Information for pure 
fluids is required as a prerequisite for mixture studies. The theory of 
transport phenomena has been developed and applied to produce practical 
numerical tables of the viscosity, thermal conductivity and diffusion 

( 3 ) 

coefficients of simple fluids: Ar, Kr, Xe , N^, 0 F 2 , He, H^, CH^, 

r h {4) c h (5) 
C 2b ' C 3 H 8 * 

It has been shown that a successful mixture program can emerge from 
combining the results for pure fluids with mixture equation of state 
studies. The equation of state work is being carried out by other 
investigators in this laboratory. 

Program and Results . We continue to develop the prediction procedure 
for the transport properties of mixtures reported previously. ' 

We have recently studied the fundamentals via computer simulation^ ' to 
assess the scientific justification of the corresponding states 
approach . 

The critical point behavior remains of interest^) and preliminary 
results are in process of publication. 

The transport properties of pure ethylene are being correlated. 

Problem Areas . The lack of suitable experimental mixture transport 
properties data for comparison purposes is the main problem. Also 
equation of state (PVT) data for mixtures are needed. 

Level of Effort . July 1 - December 31, 1978. 

Staff-years expended 

Equipment and/or Services Purchased 

Approximate expenditures, total 

2. 5K$ 
3 6 . 7K$ 

10 . 

Future Plans . 

The corresponding states predictive procedure for 

mixtures will be more fully developed and expanded in line with the 
concurrent equation of state studies. We intend to investigate, in 
particular, the behavior of the transport properties at gas/liquid and 
liquid/liquid equilibria. Computer simulation studies will be expanded 
Mixtures in which the components are very different (shape, size, mass, 
etc.) will be emphasized. 


1. H. J. M. Hanley, Prediction of the Viscosity and Thermal Conductivity 
Coefficients of Mixtures, Cryogenics, Vol 16, No. 11, 643-51 (Nov 1976) 
H. J. M. Hanley, Prediction of the Thermal Conductivity of Fluid 
Mixtures, Proceedings 7th ASME Conf . on Thermophysical Properties; 

H. J. M. Hanley in "Phase Equilibria and Fluid Properties in the 
Chemical Industry," ACS Symp. Series No. 60 (1977). 

2. H. J. M. Hanley, Transport Coefficients in the One-Fluid Approximation: 
Behavior in the Critical Region, J. Res. Nat. But. Stand. (U.S.) 8_2 , 18 
( 1977) . 

3. H. J. M. Hanley, W. M. Haynes and R. D. McCarty, The Viscosity and 

Thermal Conductivity Coefficients for Dense Gaseous and Liquid Methane, 
J. Phys. Chem. Ref. Data, Vol 6, No. 2, 597-609 (1977). 

4. H. J. M. Hanley, K. E. Gubbins and S. Murad, A Correlation of the 

Existing Viscosity and Thermal Conductivity Coefficients of Gaseous and 
Liquid Ethane, J. Phys. Chem. Ref. Data, Vol 6, No. 4, 1167 (1977). 

5. H. J. M. Hanley, P. M. Holland, K. E. Gubbins and J. M. Haile, J. Phys. 

6 . 

Chem. Ref. Data (in press 1978). 

D. J. Evans and H. J. M. Hanley, Phys. Rev. (submitted). 



Principal Investigators . G. C. Straty, N. A. Olien, B. A. Younglove, 

H. M. Roder, L. A. Weber, B. J. Ackerson, and D. E. Diller 

Cost Center Numbers . 7360122, 7360124, 7360125 

Sponsor Project Identification . NBS 

Introduct ion . Accurate thermophysical properties data and predictive 
calculation methods for cryogenic fluids are needed to support advanced 
cryogenic technology projects. For example, liquefied natural gas is 
expected to supply an increasing percentage of the United States' energy 
requirements through 1990. Liquefaction plants, ships and receiving 
terminals are being constructed to transport and store natural gas in 
the liquid state (LNG). Accurate thermophysical properties data for LNG 
are needed to design low temperature processes and equipment. Accurate 
data will benefit the energy industries and the consumer by providing 
for safe and efficient operations and reduced costs. We are now 
examining the data needs of a number of higher temperature industries 
such as the synthetic natural gas (SNG) industry. This area of 
technology as well as the liquefied petroleum gas (LPG) industry are 
logical extensions of the current LNG work. SNG mixtures can be 
characterized as much more complex than natural gas, containing unlike 
(including highly polar) molecules. Interactions between unlike 
molecules are not well understood and the accurate data necessary to 
quantitatively understand the interactions are lacking. The needs for 
accurate predictive methods for SNG are essentially the same as LNG, 
i.e., to reduce capital and operating costs and improve energy 
ef f iciency . 

Objectives or Goals . The objectives of this project are to provide 
comprehensive accurate thermodynamic, electromagnetic and transport 
properties data and calculation methods for technically important 
compressed and liquefied gases (helium, hydrogen, oxygen, nitrogen, 
methane, ethane, etc.) at low temperatures. In addition we intend to 
develop the capability to perform accurate PVT measurements on gaseous 
mixtures and pure components at high pressures and above room 
temperature. Precise compressibility, calorimetric and other physical 
property measurements will be performed to fill gaps and reconcile 
inconsistencies. Definitive interpolation functions, computer programs 
and tables will be prepared for engineering calculations. The immediate 
goals of this work are to obtain accurate sound velocity and thermal 
diffusivity data for compressed and liquefied gases by using laser light 
scattering spectroscopy techniques; design, construct and performance 
test a precision PVT apparatus for the region 250 - 900 K with pressures 
to 35 MPa; and design, construct and performance test a transient 
hot-wire thermal conductivity apparatus for the region 70 - 350 K with 
pressures to 80 MPa. 

Background . The application of laser light scattering techniques to 
obtaining thermophysical properties data was initiated to complement and 
check other measurement methods and to solve measurement problems 
inherent in more conventional methods. For example, laser light 
scattering techniques permit measurements of sound velocities for fluids 
under conditions for which sound absorption is too large to perform 
ultrasonic measurements; laser light scattering techniques permit 
measurements of thermal dif fusivities under conditions for which 
convection interferes with measurements of thermal conduction. The 
feasibility of light scattering experiments to obtain data on binary 
diffusion coefficients has also been demonstrated. 


Light scattering allows thermal diffusivity measurements in the region 
where density fluctuations are relatively large, but accuracy drops 
significantly as you pass outside the extended critical region. To 
complement the scattering method, thermal conductivity measurements can 
be made with more conventional techniques such as a hot-wire technique. 
In the latter method a very small platinum wire is surrounded by the 
fluid and a voltage pulse is applied to the wire. The temperature of 
the wire is momentarily raised and the resistance increases. A series 
of very closely spaced resistance measurements would describe the return 
of the wire to equilibrium. These resistance vs. time measurements can 
be related to the rate of heat dissipation in the surrounding fluid and 
thus the thermal conductivity (provided convection heat transfer is 
prevented ) . 

The development of accurate mathematical models (equation of state) for 
fluid mixtures requires accurate PVT data for the pure constituents and 
binary mixtures of key molecular pairs. Experience with LNG has 
identified the type and accuracy of the data required. In addition to 
that, work on SNG at high temperatures is a logical follow-on to the low 
temperature work on LNG. Typical constituents of raw SNG from coal via 
the Lurgi process are: water - 50.2%; hydrogen - 20.1%; carbon 

dioxide - 14.7%; carbon monoxide - 9.2%; methane - 4.7%; ethane - 0.5%; 
hydrogen sulfide and others - 0.6%. 

An apparatus has been assembled for laser light scattering spectroscopy 
measurements on compressed and liquefied gases (76 - 300 K, 35 MPa). 

The apparatus consists of a high pressure optical cell, a cryostat 
refrigerated by means of liquid nitrogen, an argon ion laser and 
low-level light detection equipment. 

The light scattered from fluctuations in the fluid can be analyzed with 
either digital autocorrelation techniques for the examination of the 
very narrow lines associated with scattering from temperature 
fluctuations (Rayleigh scattering) or with a scanned Fabry Perot 
interferometer for the measurement of the Doppler frequency shifts 
associated with the scattering from propagating density (pressure) 
fluctuations (Brillouin scattering). 

Apparatus for photon-counting and digital autocorrelation has been 
assembled, interfaced with computer facilities and programmed to enable 
on-line data accumulation and analysis. Initial problems associated 
with signal modulations from excessive building vibrations have been 
solved by levitating the apparatus on an air suspension system. A 
small, highly stable capacitor has also been designed, constructed and 
installed inside the scattering cell to permit the dielectric constant 
of the scattering fluid to be determined, which should allow more 
accurate fluid densities to be obtained for use in the data analysis. 
Apparatus tests on well characterized, strongly scattering, test fluids 
have been made to verify data analysis programs. 

Extensive thermal diffusivity data have been obtained for methane. 
Measurements have been made along the coexistence curve, the critical 
isochore, and critical isotherm. The measurements extend outside the 
critical region as well as deep into the critical region. In the deep 
critical region the effect of temperature gradients and impurities have 
been investigated. Outside the critical region, these effects do not 
affect measurements beyond experimental accuracy. The range of the 
measurements extends from 150 K to 230 K and 3 mol/L to 22 mol/L. The 
inaccuracy of the measurements is about 5% in the critical region, 

nalysis of the 

the results has been submitted to the Journal of Chemical Physics. 

increasing to 10% or greater further away. A detailed 
data and experimental error has been made and a paper 



Some preliminary results on a mixture of 70% methane and 30% ethane were 
obtained very near the vapor-liquid critical point (plait point). The 
results are interesting in that the thermal conductivity of the mixture 
does not exhibit a critical anomaly whereas pure methane does exhibit an 
anomaly in the thermal conductivity as the critical point is approached. 
The anomalous behavior of pure fluids and nonanomalous behavior of 
mixtures is qualitatively and quantitatively in agreement with theoreti- 
cal predictions (see preceding title 'Fluid Transport Properties'). We 
hope to be able to perform more definitive measurements on hydrocarbon 
mixtures in the near future. 

7 . Program and Results . 

7.1 Transient Hot-Wire Apparatus . The assembly of the apparatus is 
complete and some preliminary measurements on air at low pressure and 
near room temperature have been made. Some difficulties have arisen due 
to the limited precision of the Nova minicomputer. The machine carries 
only 16 binary digits precision and must be run in double precision. 
Operation in this mode, however, increases execution time by a factor of 
three. The data acquisition on this type of apparatus dictates that a 
number of measurements be acquired in a little over two seconds. The 
number of data points read in double precision is only marginally 
adequate. Software means of circumventing this problem are now being 
explored . 

7.2 Laser Light Scattering Measurements . During the past reporting 
period some additional measurements were made on a 70% methane-30% 
ethane binary mixture near the mixture critical point (plait point). 
These results are not definitive enough to establish for certain the 
existence or non-existence of an anomaly in the thermal conductivity. 
What is needed is a systematic study of the behavior of a series of 
well-characterized mixtures, especially as the concentration of one 
component goes to zero. 

7.3 High Temperature PVT Apparatus . Adequate funding for this program 
was obtained in December 1978; as a result design, procurement and 
construction will proceed at a level of effort of approximately 1.5 
staff-years/year. An automatic self-balancing thermometry bridge has 
been obtained and checked out. Two precision quartz pressure 
transducers (to 35 MPa) have been received and are installed in the NBS 
Pressure Calibration System for calibration and long term stability 
testing. Preliminary design of the experimental method and cell are in 
progress as well as an examination of available high temperature baths. 

A desktop calculator for data acquisition and experimental control is on 
order . 

8. Problem Areas . Light scattering has proven to be a valuable tool for 

obtaining thermal diffusivity data on fluids. This is particularly true 
in a broad temperature and density range around the critical point, 
where more conventional experimental methods fail or are severely 
limited. The intensity of the scattered light however decreases 
drastically as one moves away from the critical region. Data accuracy 
in this region becomes limited by the statistical nature of the 
scattering process and the ability to maintain stability and precise 
experimental parameters over the extended periods of time necessary for 
data accumulation. 

The difficulties outlined in 7.1 regarding the processing capabilities 
of the present minicomputer persist in delaying the start of 
experimental measurements at low temperature and high pressure. 


9. Level of Effort . July 1 - December 31, 1978. 

Staff-years expended 

Equipment and/or Services Purchased 
Approximate expenditures, total 

6. 3K$ 
61 .0K$ 

10. Future Plans. 

Objectives and Schedule: Quarter 



Complete performance test transient 
hot-wire thermal conductivity 

apparatus. ^ 

Design, construct and performance 

test high temperature-high 

pressure PVT apparatus. 

Laser light scattering measurements 

on well-characterized binary 

systems . 


1. B. J. Ackerson and G. C. Straty, Rayleigh Scattering from Methane, J. 
Chem. Phys . 6_9, 1207-12 (Aug 1978 ). 

2. B. J. Ackerson and H. J. M. Hanley, The Thermal Diffusivity of Methane 
in the Critical Region, Chem. Phys. Lett. 5_3 , 596-8 (Feb 1978 ). 



Principal Investigators . M. J. Hiza, A. J. Kidnay (part-time), and 
R. C. Miller (part-time) 

Cost Center Numbers . 7360123, 7362289, 7368574 

Sponsor Project Identification . NBS , NBS (OSRD) , GRI 

Introduction . Accurate thermodynamic properties data and prediction 
methods for mixtures of cryogenic fluids are needed to design and 
optimize low temperature processes and equipment. This project provides 
new experimental measurements on equilibrium properties and compilations 
of evaluated equilibrium properties data which are suitable for direct 
technological use or for the evaluation of prediction methods. 

Objectives or Goals . The overall objectives of this project are to 
provide critically evaluated data on the phase equilibria and thermo- 
dynamic properties of cryogenic fluid mixtures. The program has been 
divided into the following elements: 

a) Preparation of a comprehensive bibliography on experimental 
measurements of equilibrium properties for mixtures of selected 
molecular species of principal interest in cryogenic technology. 

b) Selection and/or development of methods for correlation, evaluation 
and prediction of equilibrium properties data. 

c) Retrieval and evaluation of experimental data for specific mixture 
systems selected on the basis of theoretical and/or technological 
importance . 

d) Preparation of guidelines for future research based on the 
deficiencies noted in (a), (b), and (c). 

e) Performing experimental research to alleviate deficiencies and 
provide a basis for improvement of prediction methods. 

Background . A physical equilibria of mixtures research project was 
established in the Thermophysical Properties Division in 1959. The 
initial effort, based on a bibliographic search and other considera- 
tions, was directed toward the acquisition of new experimental data on 
the solid-vapor and liquid-vapor equilibria and physical adsorption 
properties for a limited number of binary and ternary mixtures of 
components with widely separated critical temperatures. Most of the 
systems studied included one of the light hydrocarbon species — 
methane, ethane, or ethylene (ethene) — with one of the quantum 
gases -- helium, hydrogen, or neon. The data for these systems led to 
significant improvements in the predictions of physical adsorption 
equilibrium and a correlation for the prediction of deviations from the 
geometric mean rule for combining characteristic energy parameters. In 
addition, significant new information was obtained for interaction third 
virial coefficients which was used in a correlation by one of our 
consultants, J. M. Prausnitz. The approach taken in this work has been 
as fundamental as possible with the intention of having an impact on a 
broad range of mixture problems. 

Recent efforts have been directed toward problems associated with 
systems containing components with overlapping liquid temperature 
ranges, such as nitrogen + methane, methane + ethane, etc.