scholarly journals The thermal conductivity of gas mixtures

1929 ◽  
Vol 123 (791) ◽  
pp. 134-142 ◽  
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Calibration Curve ◽  
Bridge Circuit ◽  
Simple Calculation ◽  
Gas Analysis ◽  
Heat Losses ◽  
Gas Mixture ◽  
Metallic Conduction ◽  
Copper Lead

The action of the katharometer as an instrument for gas analysis depends essentially upon the thermal conductivity of the gas mixture examined. One method of calibration for a given pair of gases is to make a number of mixtures of known composition by volume, and to obtain from them a curve showing how the deflection θ of the galvanometer in the bridge circuit of the instrument depends upon the composition of the mixture which surrounds one of the fine platinum helices. By reference to this curve, any other mixture of the two gases can be analysed when its deflection is known. A typical calibration curve is shown in fig. 1, which is for mixtures of helium and argon. The direction of the galvanometer deflection depends on whether the gas is a better or worse conductor than air. A useful convention is to regard the deflection for gases which are better conductors than air as positive. Daynes has examined the nature of the heat losses in the katharometer cell, which are due to ( a ) radiation, ( b ) convection, ( c ) conduction by the gas, ( d ) cooling of the platinum helix by metallic conduction along the copper lead. Even at the highest temperature used in the katharometer, the effect of ( a ) is very small, and will not be influenced directly by the nature of the gas surrounding the wire. Experiments have shown that the effect of ( b ) is also small. The effect of ( c ) on the temperature of the helix is large, and will depend upon the nature of the gas. The effect of ( d ) is also considerable, and will depend upon the temperature of the helix. This effect will consequently vary with the nature of the gas under examination, but the magnitude of the effect in the steady state which is reached depends upon the effect of ( c ) (the small effects of convection and radiation will similarly depend upon the effect of ( c )). Thus in practice, the thermal conductivity of the gas controls the temperature of the helix, and the instrument will give the same reading for all gases or mixtures having the same thermal conductivity. Owing to the complicated design of the katharometer cell, it is not possible to make a simple calculation of the heat loss due solely to the conductivity of the gas, or to devise a method of converting katharometer readings directly into thermal conductivities. It should be noticed also that the calibration curves for different instruments are not all of quite the same form, owing to small differences in the winding of the helix, or of its position in the cell.

scholarly journals Thermal conductivity of insulating refractory materials: comparison of steady-state and transient measurement methods

Open Ceramics ◽  
2021 ◽  
pp. 100118
Author(s):  
Diana Vitiello ◽  
Benoit Nait-Ali ◽  
Nicolas Tessier-Doyen ◽  
Thorsten Tonnesen ◽  
Luís Laím ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Measurement Methods ◽  
Refractory Materials ◽  
Transient Measurement

Design of a Steady-State, Parallel-Plate Thermal Conductivity Apparatus for Nanofluids and Comparative Measurements With Transient HWTC Apparatus

2010 ◽  
Author(s):  
Milivoje M. Kostic ◽  
Casey J. Walleck
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Parallel Plate ◽  
Measurement Method ◽  
Mixture Theory ◽  
Hot Wire ◽  
Electro Magnetic ◽  
Magnetic Phenomena ◽  
Thermal Conductivities

A steady-state, parallel-plate thermal conductivity (PPTC) apparatus has been developed and used for comparative measurements of complex POLY-nanofluids, in order to compare results with the corresponding measurements using the transient, hotwire thermal conductivity (HWTC) apparatus. The related measurements in the literature, mostly with HWTC method, have been inconsistent and with measured thermal conductivities far beyond prediction using the well-known mixture theory. The objective was to check out if existing and well-established HWTC method might have some unknown issues while measuring TC of complex nano-mixture suspensions, like electro-magnetic phenomena, undetectable hot-wire vibrations, and others. These initial and limited measurements have shown considerable difference between the two methods, where the TC enhancements measured with PPTC apparatus were about three times smaller than with HWTC apparatus, the former data being much closer to the mixture theory prediction. However, the influence of measurement method is not conclusive since it has been observed that the complex nano-mixture suspensions were very unstable during the lengthy steady-state measurements as compared to rather quick transient HWTC method. The nanofluid suspension instability might be the main reason for very inconsistent results in the literature. It is necessary to expend investigation with more stable nano-mixture suspensions.

Unsteady Tip Leakage Vortex Cavitation Originating From the Tip Clearance of an Oscillating Hydrofoil

2005 ◽  
Vol 128 (3) ◽  
pp. 421-429 ◽  
Author(s):  
Masahiro Murayama ◽  
Yoshiki Yoshida ◽  
Yoshinobu Tsujimoto
Keyword(s):  
Steady State ◽  
Qualitative Agreement ◽  
Cavity Growth ◽  
Simple Calculation ◽  
Tip Clearance ◽  
Cavity Volume ◽  
Cavity Size ◽  
Tip Leakage Vortex ◽  
Tip Leakage ◽  
Unsteady Characteristics

Tip leakage vortex cavitations originating from the tip clearance of an oscillating hydrofoil were observed experimentally. It was found that the delay between the unsteady and the steady-state results of the tip leakage vortex cavitation increase, and that the maximum cavity size decreases when the reduced oscillating frequency increases. To simulate the unsteady characteristics of tip leakage vortex cavitation, a simple calculation based on slender body approximation was conducted taking into account the effect of cavity growth. The calculation and experimental results of the cavity volume fluctuation were found to be in qualitative agreement.

scholarly journals Improving the quality of alumina-containing sinter using water-cooled furnace shell

2012 ◽  
Vol 44 (3) ◽  
pp. 281-286
Author(s):  
A.V. Aleksandrov ◽  
V.V. Aleksandrov
Keyword(s):  
Thermal Conductivity ◽  
Steady State ◽  
Heat Exchange ◽  
Energy Balance ◽  
Cold Water ◽  
Sintering Temperature ◽  
Radiant Heat ◽  
Thermal Processes ◽  
Technical Solutions

This article deals with the use of computer modeling to develop technical solutions to ensure better quality of alumina-containing sinter. The simulation accounted for the influence of the feed materials on the thermal processes in the furnace. The energy balance (including thermal conductivity, heat convection and radiant heat exchange) was solved assuming steady state. A good correlation was observed for the actual and calculated temperatures of the solids and gases, with less than 15% discrepancy. Using the model of the furnace investigated the possibility of lowering the temperature of sintering by removing heat from the outside of the furnace shell. To reduce the sintering temperature to 1000 ?C length of the refractory lined steel is 5 m, the height of the lining should not exceed - 0.06 m, the required rate of cold water - 54.7 m3/h

scholarly journals The Influence of Burial Depth and Soil Thermal Conductivity on Heat Transfer in Buried CO2 Pipelines for CCS: A Parametric Study

2020 ◽  
Author(s):  
Babafemi Olugunwa ◽  
Julia Race ◽  
Tahsin Tezdogan
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Steady State ◽  
Thermal Resistance ◽  
Parametric Study ◽  
Flow Assurance ◽  
Burial Depth ◽  
Soil Thermal Conductivity ◽  
Dense Phase ◽  
Pipeline Transportation

Abstract Pipeline heat transfer modelling of buried pipelines is integral to the design and operation of onshore pipelines to aid the reduction of flow assurance challenges such as carbon dioxide (CO2) gas hydrate formation during pipeline transportation of dense phase CO2 in carbon capture and storage (CCS) applications. In CO2 pipelines for CCS, there are still challenges and gaps in knowledge in the pipeline transportation of supercritical CO2 due to its unique thermophysical properties as a single, dense phase liquid above its critical point. Although the design and operation of pipelines for bulk fluid transport is well established, the design stage is incomplete without the heat transfer calculations as part of the steady state hydraulic and flow assurance design stages. This paper investigates the steady state heat transfer in a buried onshore dense phase CO2 pipelines analytically using the conduction shape factor and thermal resistance method to evaluate for the heat loss from an uninsulated pipeline. A parametric study that critically analyses the effect of variation in pipeline burial depth and soil thermal conductivity on the heat transfer rate, soil thermal resistance and the overall heat transfer coefficient (OHTC) is investigated. This is done using a one-dimensional heat conduction model at constant temperature of the dense phase CO2 fluid. The results presented show that the influence of soil thermal conductivity and pipeline burial depth on the rate of heat transfer, soil thermal resistance and OHTC is dependent on the average constant ambient temperature in buried dense phase CO2 onshore pipelines. Modelling results show that there are significant effects of the ambient natural convection on the soil temperature distribution which creates a thermal influence region in the soil along the pipeline that cannot be ignored in the steady state modelling and as such should be modelled as a conjugate heat transfer problem during pipeline design.

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