Hydrogen: Its Technology and Implication

Hydrogen Properties - Volume III

Cox

• Publisher: CRC Press
• Year: 2019
• Print ISBN: 9781138597044
• eBook ISBN: 9780429945175
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Biology

Volume II of this series provides detailed design information on systems necessary for the storage, transfer, and transmission of gaseous and liquid hydrogen.Cost factors, technical aspects, and models of hydrogen pipeline systems are included together with a discussion of materials for hydrogen service. Metallic hydride gaseous storage systems for the utility and transportation industry are covered in detail, and the design Dewars and liquid hydrogen transfer systems are examined.This series in 5 volumes represents a serious attempt at providing information on all aspects of hydrogen at the postgraduate and professional level. It discusses recent developments in the science and technology of hydrogen production; hydrogen transmission and storage; hydrogen utilization; and the social, legal, political environmental, and economic implications of hydrogen's adoption as an energy medium.

Chapter 1

Introduction

This document gathers together the available thermophysical properties of hydrogen. The work was performed at the Cryogenic Data Center of the National Bureau of Standards in Boulder, Colorado. The Cryogenic Data Center has been collecting data and documents pertinent to the field for 15 years and presently has about 100,000 coded entries which may be computer searched to give bibliographies on the physical properties of materials at low temperatures. A computer search of the data center holdings produced a bibliography for hydrogen of about 2,500 references. All of these references were considered; some of them do not appear here as a result of the review and editing process.

Chapter 1
INTRODUCTUION

1.1. SCOPE AND PHILOSOPHY

The scope of this volume is defined as all physical properties of fluid hydrogen (chemical properties were excluded) with no limits on pressure or temperature. Although the solid phase was not included in the original scope, articles dealing with the properties of solid which were encountered during the review of the literature have been noted on the description sheets, and values of properties for the solid at the triple point have been included where possible. In addition, short descriptions of slush and metallic hydrogen are given. Properties of the isotopes of hydrogen have not been included, except in a few instances; the reader is referred to Reference 14.

Papers on engineering processes utilizing hydrogen were specifically excluded in the bibliographic search and subsequent review. The subject of hydrogen embrittlement of materials is not treated here (see Reference 276).

The level of review of the properties of hydrogen varies from the extensive tabulations of “critically evaluated” thermodynamic and transport properties to the selection of a few representative values from the literature by persons knowledgeable in the field. In the latter case the data selected were judged to be the most useful to the largest number of potential users of this volume. For those who need to pursue the subject in greater detail, a list of references is provided. References to articles that treat areas of limited interest in which only a few articles exist have also been included.

1.2. DESCRIPTIVE SHEETS

These sheets serve as the starting point for the use of this volume. For a given property each sheet usually contains the following:

A. A brief description or definition of the property to distinguish between similar sounding terms.

B. A locator of tabular values of the property. The range and units of the tables are given for convenience.

C. A locator of graphs and charts of the property.

D. Mathematical equations which represent the property provided that the functional form is simple.

E. One or more values of the property, usually at fixed points to illustrate the range of the property.

F. An estimate of uncertainty is usually given. It is made on a 2 σ level of probability. This means that there is a 95% chance that new experimental measurements (of equal or greater accuracy) of the property will fall within a 2 σ band of the quoted numbers. The estimate of the uncertainty of a property is seldom straightforward and is often made on the basis of the accuracy of the instrumentation used rather than the random scatter of a given set of data. In the case of a property that is tabulated over a wide range of pressure and temperature, the stated uncertainty is for the most uncertain value, and the uncertainty of most of the tabular entries is much less. Exceptions to the above convention are noted individually on the descriptive sheets. The most common exception is the critical region where the uncertainty of most properties is greater than the stated value. In no case should the quoted uncertainty be associated with values from other than recommended sources or values extrapolated from the tables.

G. A list of references is given with each descriptive sheet.

1.3. FIGURES

Chapter 3 is a collection of property charts and diagrams. These figures were taken from the literature in the original form of presentation; consequently, the units are a complete mix of SI, metric, and engineering. In most cases the prime purpose of the figures is to illustrate the behavior of a property over a wide range of pressure and temperature. Although the figures will provide adequate values for rough calculations, the tabular values are recommended for precise calculations.

1.4. TABLES

The tables of properties are collected in Chapter 4. The extensive tabulations of thermodynamic and transport properties cover the range from the triple point to 3000 K, with pressures to 100 MPa. They are presented in SI units for both para and normal hydrogen.

1.5. COMPUTER PROGRAMS AND EXTRAPOLATION

In many instances a computer program is a convenient source of property data. In other instances, particularly where a large number of values is needed in a short time, a computer program to furnish these values is a necessity. For these and other reasons, the use of computer programs to furnish fluid property data has steadily increased in recent years. This increased usage has resulted in a variety of computer programs. At the present time there does not seem to be a single program that will satisfy every need, and a choice must often be made on the basis of the particular job requirements. Table 1 lists the more important fluid property programs for hydrogen and some of the pertinent information needed to select the proper program for a particular job. A column-by-column description of Table 1 is given below.

A. Column 1 lists four general methods used to computerize the thermodynamic properties of fluids. The linear interpolation method is, as the name implies, tabular interpolation of property values stored in the computer. This method is fast but not very accurate and requires more computer core storage than the other methods. The most accurate method, if programmed properly, is polynomial interpolation. The disadvantages of the polynomial method are a lack of versatility and slow computations relative to the other methods. A good compromise and a widely used method is the equation-of-state approach using a modified Benedict Webb Rubin (MBWR) equation. This method offers accuracies only slightly worse than the polynomial interpolation method and has the advantages of being faster and more versatile and giving a continuous, thermodynamically consistent surface. The main disadvantage of the MBWR is that it is functionally incorrect in the critical region, i.e.,

Table 1
MAJOR HYDROGEN PROPERTIES COMPUTER PROGRAMS

^a Numbers refer to explanations in text.

^b This program used to calculate tables in Chapter 4.

$\rho ={\rho }_c\pm 20\%\text{and}{\text{T=T}}_{\text{c}}\pm 5\%$

The nonanalytical equation-of-state approach (no programs using this method are listed in Table 1) gives theoretically correct results in the critical region, but these equations are usually difficult to use.

B. Column 2 gives the range of validity of a program in terms of pressure and temperature limits. Extrapolation of these programs beyond the stated limits is not recommended. If properties are needed beyond the stated range of validity, the list of references for that property in Chapter 2 should first be scanned, as references to properties at extreme temperatures and pressures have been noted there. If extrapolation of one of the programs is necessary, the modified BWR type is the most convenient and least likely to yield large errors.

C. The symbols used in column 3 are defined as follows:

P	= pressure
T	= temperature
ρ	= density
H	= enthalpy
s	= entropy
λ	= thermal conductivity
η	= viscosity
cp	= specific heat capacity at constant pressure
cv	= specific heat capacity at constant volume
ϵ	= dielectric constant
γ	= surface tension
RI	= refractive index
ω	= speed of sound

The units of the properties vary from program to program.

D. The accuracy of the properties calculated from these programs varies from property to property within a given program. The accuracies quoted in column 4 are for densities calculated from a P-T input. Since they are an estimate of the average accuracies, they are most useful as a basis of comparison with the other programs.

E. Column 5 is self-explanatory. Copies or use of the program may be obtained by contacting the agency listed.

F. For certain applications the mathematical continuity of the properties is importan...

Table of contents

• Cover
• Title Page
• Copyright Page
• Table of Contents
• Chapter 1 Introduction
• Chapter 2 Discussion of the Properties
• Chapter 3 Data Graphs (For Parahydrogen Unless Otherwise Stated)
• Chapter 4 Data Tables
• Unit Conversions, Physical Constants, and Symbols
• References
• Index