Xenon thermal conductivity

Figure 4 graphically represents the results of the xenon thermal conductivity comparison and shows the deviation of the semi-empirical method of calculating xenon thermal conductivity from the empirically derived DIPPR curve fit recommended in this paper. Figure 4 shows that NIST results track well with DIPPR results. At 1150 K (reactor outlet gas temperature) the semi-empirical approach deviates from the empirically derived DIPPR value by 9.6%. 

FIGURE 4. Xenon Thermal Conductivity as a Function of Temperature. 

Adequate helium and xenon pure eomponent viseosity and thermal conduetivity data exist to allow the use of curve fits of experimental data. The method recommended to calculate the viscosity and thermal conductivity of pure hehum and pme xenon is to use equations provided by the Design Institute for Physical Property Data (DIPPR) (Daubert et al., 1992). These equations were produced from curve fits of experimental data and include a quahty estimate with each correlation. The quality estimate represents the average rehability of data plus error from regression. DIPPR indicates less than 3% error for hehum and xenon viscosity and less than 5% error for hehum and xenon thermal conductivity. 

The only condition for cool-flame production with ethanol was that the temperature at the centre of the vessel rose above the ambient by a critical amount, about 20 °C. This suggests that thermal factors are important in cool-flame production, and this was confirmed by the effect of addition of inert gases. The special importance of thermal conductivity is exemplified by the differing effects of helium and xenon, two gases with identical heat capacities but very different thermal conductivities. Thus helium raised the limit, while xenon lowered it. 

The values in these tables were generated from the NIST REFPROP software (Lemmon, E. W, McLinden, M. O., and Huber, M. L., NIST Standard Reference Database 23 Reference Fluid Thermodynamic and Transport Properties—REFPROP, National Institute of Standards and Technology, Standard Reference Data Program, Gaithersburg, Md., 2002, Version 7.1). The primary source for the thermodynamic properties is Lemmon, E. W, and Span, R., Short Fundamental Equations of State for 20 Industrial Fluids, / Chem. Eng. Data 51(3) 785-850, 2006. The source for viscosity and thermal conductivity is McCarty, R. D., Correlations for the Thermophysical Properties of Xenon, National Institute of Standards and Technology, Boulder, Colo., 1989. 

C at five different heating rates (0.5, 1, 5, 10, and 15°C/min). The thermal properties of the samples were then measured in x, y, and z directions with a Xenon flash diffusivity apparatus. The thermal conductivity of the samples was calculated from their thermal diffusivity. Table 2 lists the Z-direction thermal conductivity values for each graphitization heating rate and position within the furnace. From these data, it is clear that the thermal conductivity is directly related to the graphitization heating rate. A similar trend was observed in the crystal properties of the foams determined from X-ray diffraction (not shown here for brevity). However, it is not understood why there is a maximum at l°C/min. 

Values extracted and in some cases rounded off from those cited in Rabinovich (ed.), Thermophysical Properties of Neon, At on, Krypton and Xenon, Standards Press, Moscow, 1976. v = specific volume, mVkg h = specific enthalpy, kj/kg s = specific entropy, kJ/(kg-K). This source contains an exhaustive tabulation of values. The notation 7.420.-4 signifies 7.420 x 10". This book was published in English translation by Hemisphere, New York, 1988 (604 pp.). The 1993 ASHRAE Handbook—Fundamentals (SI ed.) has a thermodynamic chart for pressures from 1 to 2000 bar, temperatures from 90 to 700 K. Saturation and superheat tables and a chart to 50,000 psia, 1220 R appear in Stewart, R. B., R. T. Jacobsen, et al.. Thermodynamic Properties of Refrigerants, ASHRAE, Atlanta, GA, 1986 (521 pp.). For specific heat, thermal conductivity, and viscosity see Thermophysical Properties of Refrigerants, ASHRAE, 1993. 

The tiny final trap, loaded with the equivalent of 10 cc (at STP) Xe/CO2 product, is heated to 200°C and the product gas is allowed to expand into one of four counting cells. Transfer efficiency is boosted by use of a syringe pump, as shown in Area 3 of Fig. 15.7. The exact ratio of the Xe and CO2 mix is determined with a thermal conductivity device (TDC). This is an important measurement because the xenon separation efficiency depends on various factors, e.g., the conditioning of the traps and the ambient temperature. The ARSA typically produces a product gas that is about 50% xenon. 

The helium/xenon coolant will be compared relative to some other common gasses. The properties that will be examined are viscosity, thermal conductivity, specific heat and density. 

This table shows that helium has the highest thermal conductivity with the helium/xenon mixture coming in second. 

Measuring thermal parameters of Li-ion cells is crucial for optimizing the thermal design of battery systems with respect to lifetime and safety issues. The thermal parameters of interest are heat capacity, thermal conductivity, and heat exchange between the cell s surface and the environment due to radiation and convection. Traditionally, heat capacity is obtained by calorimeter measurements and thermal conductivity is obtained by heat flux or Xenon-Flash measurements [1], Disadvantages of these methods are the requirement of expensive measurement devices and the destruction of the cell for thermal conductivity measurements. 

The fact that one adamantine crystal could be produced in which the thermal conductivity was reduced to values near the theoretical minimum by an uncharged, neutral atom like xenon suggested that the phonon heat transport could be lowered in other semiconducting crystals without changing the electron concentration or their mobilities. This is the phonon glass-electron crystal, or PGEC, concept [4]. 

Hanley, H. J. M. (1974). The viscosity and thermal conductivity coefficients of dilute argon, liypton, and xenon. J. Phys. Chem. Ref. Data, 2,619-642. 

Springer, G. S. fe Wingeier, E. W. (1973). Thermal conductivity of neon, argon, and xenon at high temperatures. J. Chem. Phys., 59,2747-2750. 

For a harmonic crystal the phonon lifetime is infinite and there is no scattering of thermal phonons.To understand the mechanism on how the guest-host interactions lead to the anomalous temperature dependence of the thermal conductivity, the lifetimes were calculated for phonon-phonon scatterings as a result of the anharmonic terms in the xenon-water potential of xenon hydrate in the small and large cage. The inverse relaxation time (lifetime), of a lattice vibration with frequency C0j q) (/ is the branch index and q is the direction of the momentum transfer) is related to the transition rate, W, of the lattice wave scattered from state qj q f by a defect according to, ... 

Results of the calculated thermal conductivity for ice Ih, S-I methane hydrate and empty hydrate are depicted in Figure 14. The thermal conductivity of ice Ih has improved, but the absolute value is still slightly smaller than the experiment. The calculations reproduced previous observation that the thermal conductivity of the hydrate is lower than ice Ih and the empty hydrate. Even though the empty hydrate has a lower thermal conductivity than ice Ih, the crystalline temperature profile is similar. A surprising finding is the reversal in the thermal conductivity of methane hydrate at low temperature. From 250 to 100 K, the thermal conductivity decreases slightly. When the hydrate is cooled below 100 K, the conductivity increases and follows the trend as a crystal. This unusual temperature profile has indeed been observed in methane and xenon hydrates,details of which will be deferred to a later part of this chapter. To unravel the thermal transport mechanism, various correlation functions were computed and the relaxation times analyzed.The HCACF can be fitted to... 

Figure 16 Experimental thermal conductivity of (a) xenon hydrate and (b) methane hydrate. Reprinted figure with permission from A. I. Krivchikov, B. Y. Gorodilov, O. A. Korolyuk, V. G. Manzhelii, O. O. Romantsove, H. Conrad, W. Press, J. S.

Helium and Xenon viscosity and thermal conductivity values impact pressure drop and heat transfer calculations... 

Review of Helium and Xenon Pure Component and Mixture Transport Properties and Recommendation of Estimating Approach for Project Prometheus (Viscosity and Thermal Conductivity)... 

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