scholarly journals A flow method for comparing the specific heats of gases part I.―The experimental method

1930 ◽  
Vol 126 (801) ◽  
pp. 319-332 ◽  
Keyword(s):  
Specific Heat ◽  
Measured Temperature ◽  
Constant Flow ◽  
Technical Problems ◽  
Specific Heats ◽  
Resistance Thermometers ◽  
Wide Range ◽  
Exact Temperature ◽  
Careful Design ◽  
Theoretical Developments

Recent theoretical developments of kinetic theory, especially in the theory of pseudo-unimolecular reactions, have led to the demand for further measurements of the specific heats of vapours and gases, especially at high temperatures. Again many technical problems are demanding a better knowledge of the specific heats of gases over a wide range of conditions. The method to be described enables the ratio of the specific heats of two gases to be measured accurately. Since the monatomic gases are available as reliable standards, the fact that the method gives relative values only is of little account. There appear to be possibilities of wide application for the method on account both of its simplicity and its adaptability to a wide range of temperature and pressure. The method consists essentially in passing a slow stream of gas through a narrow tube, along which a temperature gradient has been established. The change of the temperature distribution along the tube depends on the properties of the gas and the rate of flow. It is found possible to choose the arrangement so that the measured temperature difference between two parts of the tube is a direct measure of the specific heat of the gas flowing in the tube. It will be seen that, though the method belongs to the "constant flow" class, it differs considerably in principle from that originally devised by Callendar and used for liquids by Callendar and Barnes, and Lang; and for gases by Swann, Nernst, and Scheel and Heuse. In the first place, all these experimenters measured the rate of supply of heat electrically, whilst the heat lost by conduction and radiation appeared as an experimentally determined correction; in the method to be described, the heat losses, though playing an essential part in the theory of the apparatus, do not enter at all into the measurement of the specific heat. Secondly, in previous constant flow methods the temperature of the gas itself has been measured by resistance thermometers, a proceeding which involves very careful design of the thermometer, the thorough mixing of the gas, and which has constituted the essential difficulty of specific heat measurements. In the present method the difficulty is avoided by never requiring to measure the exact temperature of the gas. Instead the temperature of the tube containing the gas is measured without in any way disturbing the flow.

THE RESONANCE METHOD OF MEASURING THE RATIO OF THE SPECIFIC HEATS OF A GAS, Cp/Cv: PART V: SECTION A: AN IMPROVED APPARATUS FOR MEASURING THE RATIO OF THE SPECIFIC HEATS OF A GAS: SECTION B: THE USE OF ELECTRONIC COUNTER CIRCUITS TO MEASURE LOW FREQUENCIES AND A VARIABLE LOW FREQUENCY OSCILLATOR

1949 ◽  
Vol 27a (3) ◽  
pp. 27-38 ◽  
Author(s):  
L. Katz ◽  
S. B. Woods ◽  
W. F. Leverton
Keyword(s):  
Specific Heat ◽  
Low Frequency ◽  
Resonance Method ◽  
Time Interval ◽  
Low Frequencies ◽  
Specific Heats ◽  
Wide Range ◽  
New Apparatus ◽  
The Stability ◽  
Number Of Cycles

This paper describes an improved apparatus for the determination of γ = Cp/Cv, the ratio of the specific heat at constant pressure to the specific heat at constant volume for a gas. With this apparatus, γ is determined by the resonance method of Clark and Katz. The new apparatus is constructed of stainless steel and is designed to withstand pressures up to 100 atm. This new apparatus is more compact and can be used with corrosive gases. Provision is made for the control and accurate measurement of the temperature of the enclosed gas over a wide range of temperatures. An electronic counter which will measure time intervals, in units of 10 μsec., from 100 μsec. to several seconds in length is described in Section B. An unknown frequency may be determined by measuring the time interval in which a preselected number of cycles occurs. The accuracy is such that frequencies may be measured to within approximately 1 part in 105. The circuit for a variable frequency transitron oscillator with an output of 30 w. in a range of 15 to 250 c.p.s. is shown. The stability of the oscillator is such that the frequency may easily be maintained within 1 part in 10,000 for long periods, and with care in temperature control and choice of electrode voltages much greater stabilities may be obtained.

The specific heats of three paramagnetic salts at very low temperatures

1956 ◽  
Vol 237 (1210) ◽  
pp. 395-403 ◽  
Keyword(s):  
Specific Heat ◽  
Absolute Temperature ◽  
Magnesium Nitrate ◽  
Paramagnetic Resonance ◽  
Specific Heats ◽  
Ammonium Alum ◽  
Relaxation Measurements ◽  
Ferric Ammonium ◽  
The Absolute ◽  
Measured Specific Heat

The specific heats of three paramagnetic salts, neodymium magnesium nitrate, manganous ammonium sulphate and ferric ammonium alum, have been measured at temperatures below 1°K using the method of γ -ray heating. The temperature measurements were made in the first instance in terms of the magnetic susceptibilities of the salts, the relation of the susceptibility to the absolute temperature having been determined for each salt in earlier experiments. The γ -ray heatings gave the specific heat in arbitrary units. The absolute values of the specific heats were found by extrapolating the results of paramagnetic relaxation measurements at higher temperatures. The measured specific heat of neodymium magnesium nitrate is compared with the value calculated from paramagnetic resonance data, and good agreement is found.

scholarly journals III. Investigations of the specific heat of solid bodies

1865 ◽  
Vol 155 ◽  
pp. 71-202 ◽  
Keyword(s):  
Specific Heat ◽  
Thermal Action ◽  
General View ◽  
Specific Heats ◽  
General Law ◽  
Different Temperatures ◽  
The Times ◽  
The Individual ◽  
Solid Bodies

I. About the year 1780 it was distinctly proved that the same weights of different bodies require unequal quantities of heat to raise them through the same temperature, or on cooling through the same number of thermometric degrees, give out unequal quantities of heat. It was recognized that for different bodies the unequal quantities of heat, by which the same weights of different bodies are heated through the same range, must be determined as special constants, and considered as characteristic of the individual bodies. This newly discovered property of bodies Wilke designated as their specific heat , while Crawford described it as the comparative heat, or as the capacity of bodies for heat . I will not enter upon the earliest investigations of Black, Irvine, Crawford, and Wilke, with reference to which it may merely be mentioned that they depend essentially on the thermal action produced when bodies of different temperatures are mixed, and that Irvine appears to have been the first to state definitely and correctly in what manner this thermal action (that is, the temperature resulting from the mixture) depends on the original temperature, the weights, and the specific heats of the bodies used for the mixture. Lavoisier and Laplace soon introduced the use of the ice-calorimeter as a method for determining the specific heat of bodies; and J. T. Mayer showed subsequently that this determination can be based on the observation of the times in which different bodies placed under comparable conditions cool to the same extent by radiation. The knowledge of the specific heats of solid and liquid bodies gained during the last century, and in the first sixteen years of the present one, by these various methods, may be left unmentioned. The individual determinations then made were not so accurate that they could be compared with the present ones, nor was any general conclusion drawn in reference to the specific heats of the various bodies. 2. Dulong and Petit’s investigations, the publication of which commenced in 1818, brought into the field more accurate determinations, and a general law. The investigations of the relations between the specific heats of the elements and their atomic weights date from this time, and were afterwards followed by similar investigations into the relations of the specific heats of compound bodies to their composition. In order to give a general view of the results of these investigations, it is desirable to present, for the elements mentioned in the sequel, a synopsis of the atomic weights assumed at different times, and of certain numbers which stand in the closest connexion with these atomic weights.

Thermodynamic Properties of Pure and Mixed Thermal Plasmas Over a Wide Range of Temperature and Pressure

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Omid Askari
Keyword(s):  
Thermodynamic Properties ◽  
Specific Heat ◽  
Fluid Dynamic ◽  
Thermal Plasmas ◽  
Statistical Thermodynamic ◽  
Reference Source ◽  
Degree Of Ionization ◽  
Wide Range ◽  
Self Consistent ◽  
Temperature And Pressure

Chemical composition and thermodynamics properties of different thermal plasmas are calculated in a wide range of temperatures (300–100,000 K) and pressures (10−6–100 atm). The calculation is performed in dissociation and ionization temperature ranges using statistical thermodynamic modeling. The thermodynamic properties considered in this study are enthalpy, entropy, Gibbs free energy, specific heat at constant pressure, specific heat ratio, speed of sound, mean molar mass, and degree of ionization. The calculations have been done for seven pure plasmas such as hydrogen, helium, carbon, nitrogen, oxygen, neon, and argon. In this study, the Debye–Huckel cutoff criterion in conjunction with the Griem’s self-consistent model is applied for terminating the electronic partition function series and to calculate the reduction of the ionization potential. The Rydberg and Ritz extrapolation laws have been used for energy levels which are not observed in tabulated data. Two different methods called complete chemical equilibrium and progressive methods are presented to find the composition of available species. The calculated pure plasma properties are then presented as functions of temperature and pressure, in terms of a new set of thermodynamically self-consistent correlations for efficient use in computational fluid dynamic (CFD) simulations. The results have been shown excellent agreement with literature. The results from pure plasmas as a reliable reference source in conjunction with an alternative method are then used to calculate the thermodynamic properties of any arbitrary plasma mixtures (mixed plasmas) having elemental atoms of H, He, C, N, O, Ne, and Ar in their chemical structure.

Topology, Shape, and Size Optimization of Additively Manufactured Lattice Structures Based on the Superformula

2018 ◽  
Author(s):  
Andrea Nessi ◽  
Tino Stanković
Keyword(s):  
Lattice Structure ◽  
Lightweight Design ◽  
Mathematical Formulation ◽  
Lattice Structures ◽  
Structural Synthesis ◽  
Normal Surface ◽  
Technical Problems ◽  
Wide Range ◽  
Tetrahedral Meshing

This paper investigates the application of Superformula for structural synthesis. The focus is set on the lightweight design of parts that can be realized using discrete lattice structures. While the design domain will be obtained using the Superformula, a tetrahedral meshing technique will be applied to this domain to generate the topology of the lattice structure. The motivation for this investigation stems from the property of the Superformula to easily represent complex biological shapes, which opens a possibility to directly link a structural synthesis to a biomimetic design. Currently, numerous results are being reported showing the development of a wide range of design methods and tools that first study and then utilize the solutions and principles from the nature to solve technical problems. However, none of these methods and tools quantitatively utilizes these principles in the form of nature inspired shapes that can be controlled parametrically. The motivation for this work is also in part due to the mathematical formulation of the Superformula as a generalization of a superellipse, which, in contrast to the normal surface modeling offers a very compact and easy way to handle set of rich shape variants with promising applications in structural synthesis. The structural synthesis approach is organized as a volume minimization using Simulated Annealing (SA) to search over the topology and shape of the lattice structure. The fitness of each of candidate solutions generated by SA is determined based on the outcome of lattice member sizing for which an Interior Point based method is applied. The approach is validated with a case study involving inline skate wheel spokes.

Specific heats of polymer powders by differential scanning calorimetry

1982 ◽  
Vol 60 (14) ◽  
pp. 1853-1856 ◽  
Author(s):  
Eva I. Vargha-Butler ◽  
A. Wilhelm Neumann ◽  
Hassan A. Hamza
Keyword(s):  
Differential Scanning Calorimetry ◽  
Specific Heat ◽  
Scanning Calorimetry ◽  
Temperature Range ◽  
Specific Heats ◽  
Powdered Form ◽  
Polymer Powders

The specific heats of five polymers were determined by differential scanning calorimetry (DSC) in the temperature range of 300 to 360 K. The measurements were performed with polymers in the form of films, powders, and granules to clarify whether or not DSC specific heat values are dependent on the diminution of the sample. It was found that the specific heats for the bulk and powdered form of the polymer samples are indistinguishable within the error limits, justifying the determination of specific heats of powders by means of DSC.

3. Results of Experiments on the Specific Heat of Certain Rocks

1845 ◽  
Vol 1 ◽  
pp. 373-374
Author(s):  
M. Regnault
Keyword(s):  
Specific Heat ◽  
Royal Society ◽  
Specific Heats

Professor Forbes observed that, in his communication to the Royal Society on the Conductivity of Soils for Heat, on the 20th December last (see Proceedings, page 343*), he had referred to the separation of the conductivity and specific heat, which are involved in the results of the thermometric experiments on subterranean temperature. In order to eliminate the effect of specific heat, M. Regnault of Paris (well known by his experiments on this subject) undertook, at the request of M. Elie de Beaumont, to ascertain the specific heats of the soils in which the different sets of thermometers are sunk.

The specific heats of copper, silver, and gold below 300 K

1987 ◽  
Vol 65 (9) ◽  
pp. 1104-1110 ◽  
Author(s):  
Douglas L. Martin
Keyword(s):  
Specific Heat ◽  
Debye Temperature ◽  
Temperature Scale ◽  
Specific Heats ◽  
Practical Temperature ◽  
Practical Temperature Scale

Specific-heat measurements on silver and gold in the 15–320 K range are reported and compared with earlier measurements on these metals. The present results together with recent measurements on copper (D. L. Martin, Rev. Sci. Instrum. 58, 639 (1987)) are analyzed in terms of the Debye temperature. The results suggest a negative anharmonic contribution to specific heat for silver and gold. Structure in the results for all three metals below 60 K is consistent with known imperfections in the International Practical Temperature Scale of 1968.

An experimentally-validated framework for interpreting active-DTS measurements conducted in fully saturated porous media

2021 ◽  
Author(s):  
Nataline Simon ◽  
Olivier Bour ◽  
Nicolas Lavenant ◽  
Gilles Porel ◽  
Benoît Nauleau ◽  
...  
Keyword(s):  
Porous Media ◽  
Contaminant Transport ◽  
Temperature Increase ◽  
Saturated Porous Media ◽  
Distributed Temperature Sensing ◽  
Groundwater Flux ◽  
Wide Range ◽  
Independent Experimental Data ◽  
Theoretical Developments ◽  
Thermal Conductivities

<p>            Our ability to characterize aquifers, predict contaminant transport and understand biogeochemical reactions occurring in the subsurface directly depends on our ability of characterizing the distribution of groundwater flow. In this context, recently-developed active-Distributed Temperature Sensing (DTS) experiments are particularly promising, offering the possibility to characterize groundwater flows resulting from heterogeneous flow fields. Here, based on theoretical developments and numerical simulations, we propose a general framework for estimating active-DTS measurements, which can be easily applied and takes into account the spatial distribution of the thermal conductivities of sediments.</p><p>            Two independent methods for interpreting active-DTS experiments are proposed to estimate both the porous media thermal conductivities and the groundwater fluxes in sediments. These methods rely on the interpretation of the temperature increase measured along a single heated fiber optic (FO) cable and consider heat transfer processes occurring both through the FO cable itself and through the porous media. In order to validate these interpretation methods with independent experimental data, active-DTS measurements were collected under different flow-conditions during laboratory tests in a sandbox. First, the combination of a numerical model with laboratory experiments allowed improving the understanding of the thermal processes controlling the temperature increase. Then, the two complementary and independent interpretation methods providing an estimate of both the thermal conductivity and the groundwater flux were fully validated and the excellent accuracy of groundwater flux estimates (< 5%) was demonstrated.</p><p>            Our results suggest that active-DTS experiments allow investigating groundwater fluxes over a large range spanning 1x10<sup>-6</sup> to 5x10<sup>-2</sup> m/s, depending on the duration of the experiment. The active-DTS method could thus be potentially applied to a very wide range of flow systems since groundwater fluxes can be investigated over more than three orders of magnitude. In the field, the reliable and direct estimation of the distribution of fluxes could replace the measurement of hydraulic conductivity, whose distribution and variability still remains difficult and time consuming to evaluate.</p>

scholarly journals XVI. On the specific heats of gases at constant volume.—Part II. Carbon dioxide

1894 ◽  
Vol 185 ◽  
pp. 943-959 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Specific Heat ◽  
Constant Volume ◽  
Specific Heats ◽  
Extended Range ◽  
Absolute Density ◽  
Lower Temperature ◽  
The One ◽  
Range Observation ◽  
Linear Nature

The present paper is occupied with an experimental investigation into the variation of the specific heat at constant volume of carbon dioxide attending change of absolute density. The investigation is in continuation of a previous one, in which Carbon Dioxide, Air, and Hydrogen were the subjects of a similar enquiry over low ranges of density. It appeared to me desirable to extend the observations more especially in the case of carbon dioxide, because of the extended knowledge we already possess of its isothermals, and the fact that its critical temperature is within convenient reach. Other physical properties of the gas have also received much attention of recent years. It is also readily procured in a nearly pure state. The observations recorded in this paper extend, in the one direction, to densities, such that liquid is present at the lower temperature; and in the other, to a junction with the highest densities of the former paper. A plotting of the new observations is in satisfactory agreement with the record of the old. It reveals, however, the fact that the linear nature of the variation of the specific heat with density, deduced from the former results, is not truly applicable over the new, much more extended range observation. For convenience the chart at the end of this paper embraces the former results, and the present paper is extended to include the entire results on the variation of specific heat with density where the range of temperature, obtaining at each experiment, is approximately the same: that from air temperature to 100° C.

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