UNITED STATES DEPARTMENT OF COMMERCE BUREAU OF STANDARDS THERMAL PROPERTIES OF PETROLEUM PRODUCTS MISCELLANEOUS PUBLICATION OF THE BUREAU OF STANDARDS, No. 97 UNITED STATES DEPARTMENT OF COMMERCE R. P. LAMONT, Secretary BUREAU OF STANDARDS GEORGE K. BURGESS, Director MISCELLANEOUS PUBLICATION No. 97 THERMAL PROPERTIES OF PETROLEUM PRODUCTS NOVEMBER 9, 1929 UNITED STATES GOVERNMENT PRINTING OFFICE WASHINGTON : 1929 F<ir isale by tfttf^uperintendent of Dotmrtients, Washington, D. C. - - - Price IS cants THERMAL PROPERTIES OF PETROLEUM PRODUCTS By C. S. Cragoe ABSTRACT Various thermal properties of petroleum products are given in numerous tables which embody the results of a critical study of the data in the literature, together with unpublished data obtained at the Bureau of Standards. The tables contain what appear to be the most reliable values at present available. The experimental basis for each table, and the agreement of the tabulated values with experimental results, are given. Accompanying each table is a statement regarding the esti- mated accuracy of the data and a practical example of the use of the data. The tables have been prepared in forms convenient for use in engineering. CONTENTS Page I. Introduction 1 II. Fundamental units and constants 2 III. Thermal expansion t 4 1. Thermal expansion of petroleum asphalts and fluxes 6 2. Thermal expansion of volatile petroleum liquids 8 3. Thermal expansion of gasoline-benzol mixtures 10 IV. Heats of combustion : 14 1. Heats of combustion of crude oils, fuel oils, and kerosenes 16 2. Heats of combustion of volatile petroleum products 18 3. Heats of combustion of gasoline-benzol mixtures 20 V. Specific volume of vapor 22 VI. Thermal conductivity 24 VII. Specific heat - 26 1. Specific heat of petroleum oils of various gravities in Btu./lb. °F. or cal./g °C__ 28 2. Specific heat of petroleum vapors 28 3. Specific heat of petroleum oils of various gravities in Btu./gal. °F 30 4. Specific heat of petroleum asphalt 30 VIII. Latent heat of vaporization 32 IX. Heat content 36 1. Heat content of petroleum liquids 36 2. Heat content of petroleum vapors 37 3. Heat content of asphalt 42 4. Heat content of paraffin wax 44 X. Conclusion 46 I. INTRODUCTION The Bureau of Standards receives many requests for information on the thermal properties of petroleum products from other departments of the Government, from the petroleum industry, and from users of these products which have found so wide a variety of applications. Information of this sort is rarely to be found in systematic form such that appropriate values for a desired property may readily be assigned to the particular product in question. Engineering handbooks and physical and chemical tables, the more accessable sources of such information, are surprisingly 1 , 2 BUREAU OF STANDARDS deficient in this respect and the values given in these publications differ widely in j many instances. The Bureau of Standards has made no extensive experimental study of the I subject as a whole, but has had occasion during the past few years to make numerous determinations of some of the thermal properties of petroleum products in combination with other investigations carried out in the laboratories of the Government. In 1927 an investigation was undertaken on the thermodynamic properties of petroleum hydrocarbons, listed as project No. 38 of American Petroleum Institute Research, j In order to lay out an experimental program intelligently, it was necessary to make a critical study of the data avaiJable on the subject in the literature. The results ob- tained from this critical study when combined with unpublished results obtained at the bureau, including some preliminary results obtained under project No. 38, appeared of sufficient technical importance to warrant the preparation of preliminary tables covering several of the properties which have been investigated experimentally. Because of the lack of published information in a form readily usable by the industry, tables have been prepared in engineering units. Most petroleum products consist essentially of a large number of different hydro- carbons which are so nearly alike physically that a mixture of them exhibits a ther- modynamic behavior somewhat analogous to that shown by a mixture of isotopes. Experimental evidence indicates that many of the thermodynamic properties of mixtures of hydrocarbons are not seriously affected by considerable changes in composition. In fact, it has been found that many of these properties are very closely related to the density of the liquid which is usually known or can be readily determined with a hydrometer. This relationship afforded a very useful means of correlating existing data on commercial products. By the same means a valuable check was obtained from data on pure hydrocarbons known to exist as constituent parts of these products. Although some consistent differences were found between data on paraffin and naphthene base products of the same density, these differences were small and, consequently, of little significance in practical applications of the data. It must be realized, however, that values for the properties of petroleum products, which are subject to considerable variation in composition, can not be assigned with the same degree of accuracy as can be done in the case of materials which have a definite composition. H. FUNDAMENTAL UNITS AND CONSTANTS Temperature scale. —The Fahrenheit scale as used in this paper is derived from the International centigrade scale by means of the relation Fahrenheit temperature = (1.8 X centigrade temperature) + 32 The International centigrade scale adopted by the International Conference of ; Weights and Measures at Paris in 1927 is realized in the temperature interval 0° to 660° C, by means of the resistance thermometer of pure platinum, standardized at the temperatures of melting ice (0° C), condensing steam (100° C), and condensing sulphur vapor (444.6° C), all at standard atmospheric pressure. In accordance with common practice in the United States, 60° F. is used here as the reference temperature for specifying the density and volume of petroleum products. : THERMAL PROPERTIES OF PETROLEUM PRODUCTS 6 Mass.—The fundamental unit of mass, the kilogram, is used indirectly here. All units of weight used in this paper are weights in vacuo (mass) and not apparent weights in air. The difference is small in all cases involved here, amounting to 0.1 or 0.2 per cent. Since most of the experimental data considered were given in terms of unit mass, these units were retained and used consistently throughout. The Hunts used are related as follows 1 pound = 0.453592 kilograms Volume.—The fundamental unit of liquid volume, the liter, is defined as the volume occupied by 1 kilogram of pure water at its maximum density (4° C). The unit of liquid volume actually used throughout this circular, however, is the gallon (231 cubic inches) because of the general use of this unit in engineering and industrial practice in the United States. This unit is defined in terms of the fundamental unit by the relation 1 gallon = 3.78533 liters It is often convenient to determine the volume of liquid containers by weighing them both empty and filled with water. Since the mass of a gallon of pure water at 60° F. is known, the unit of liquid volume used here may be realized directly from the fundamental unit of mass, by the relation. 1 gallon = 3.78170 kilograms or 8.33722 pounds of water at 60° F. Density.—Mass per unit volume is the universal definition of density. In this circular, densities are expressed in pounds per gallon which are related to the funda- mental units by 1 pound per gallon = 0.119829 kilograms per liter Densities are also expressed in terms of specific gravity, defined by i 60° ™ density of oil at 60° F. Specific gravity at F>= w density of water at 6Q o R which is equivalent to the following numerical relation Density of oil at 60° F. in lbs. per gal. = 8.33722 X specific gravity of oil at 60°/60° F. Densities are commonly determined by means of a hydrometer, an instrument familiar to large numbers of persons who take an interest in their storage batteries. Some hydrometers are graduated to indicate density or specific gravity directly, although there are almost an infinite variety of arbitrary hydrometer scales in existence. Each industry in which hydrometers are used appears to have its own selection of arbitrary scales. The petroleum industry has had, in the past, two such arbitrary scales, both of which were known as Baume scales for liquids lighter than water. In order to avoid confusion, the American Petroleum Institute, the Bureau of Mines, and the Bureau of Standards agreed, in 1921, to recommend that in the future only one arbitrary scale be used in the petroleum industry, and that it be known as the A. P. I. scale. This scale is defined by the relation Degrees A. P. i.-g—J*^^ -131.5 The A. P. I. scale is used extensively in the classification and description of petroleum products. In order to make the data contained in this circular of convenience to those unfamiliar with this scale, it appeared desirable to use both, degrees A. P. I. 4 BUREAU OF STA.ND A.RDS and its equivalent, specific gravity at 60°/60° F. Degrees A. P. I. are used as one of the independent variables in the tabulation of the data partly because they are equivalent to a uniform scale of specific volume. Heat unit.—The fundamental heat unit used here is the international joule, or watt second, since electric heating was employed in most of the calorimetric measure- , ments considered. The relation between this unit and the corresponding cgs unit, as given in Bureau of Standards Circular No.