scholarly journals Abrupt reduction of the critical temperature difference of a thermoacoustic engine by adding water

AIP Advances ◽  
2015 ◽  
Vol 5 (9) ◽  
pp. 097173 ◽  
Author(s):  
K. Tsuda ◽  
Y. Ueda
Keyword(s):  
Critical Temperature ◽  
Temperature Difference ◽  
Thermoacoustic Engine

Numerical Simulation of Thermocapillary Convection in an Annular Pool of Silicone Oil Heated From Inner Wall

2007 ◽  
Author(s):  
Wanyuan Shi ◽  
Nobuyuki Oshima ◽  
Nobuyuki Imaishi
Keyword(s):  
Numerical Simulation ◽  
Critical Temperature ◽  
Temperature Gradient ◽  
Numerical Simulations ◽  
Temperature Difference ◽  
Significant Influence ◽  
Thermocapillary Convection ◽  
Silicone Oil ◽  
Annular Pool ◽  
Surface Temperature Gradient

Thermocapillary convection in a shallow annular pool (depth d = 1 mm) of silicone oil (0.65 cSt, Pr = 6.7), heated from the inner wall, is investigated by numerical simulations. Under a fixed value of temperature difference between the outer and inner walls, surface temperature gradient in the inner heated pool is about 10% higher than that in the outer heated pool. Accordingly, the critical temperature difference for the incipience of HTW (ΔTc = 4.58K) is smaller than that (ΔTc = 5.0K) in the outer heated pool. Numerical simulations indicate that two groups of HTW, propagating in opposite azimuthal directions to each other, coexist and produce interference patterns in the inner heated pool. Rotation of the pool around its axis gives no significant influence on the behavior of HTW in the inner heated pool. The characteristics of HTW are discussed in contrast with those in the outer heated pool.

scholarly journals Thermal delay of drop coalescence

2017 ◽  
Vol 833 ◽  
Author(s):  
Michela Geri ◽  
Bavand Keshavarz ◽  
Gareth H. McKinley ◽  
John W. M. Bush
Keyword(s):  
Critical Temperature ◽  
Residence Time ◽  
Temperature Difference ◽  
Initial Temperature ◽  
Theoretical Study ◽  
Fluid Viscosity ◽  
Drop Coalescence ◽  
Thermocapillary Flows ◽  
Silicone Oils ◽  
Thermal Delay

We present the results of a combined experimental and theoretical study of drop coalescence in the presence of an initial temperature difference $\unicode[STIX]{x0394}T_{0}$ between a drop and a bath of the same liquid. We characterize experimentally the dependence of the residence time before coalescence on $\unicode[STIX]{x0394}T_{0}$ for silicone oils with different viscosities. Delayed coalescence arises above a critical temperature difference $\unicode[STIX]{x0394}T_{c}$ that depends on the fluid viscosity: for $\unicode[STIX]{x0394}T_{0}>\unicode[STIX]{x0394}T_{c}$, the delay time increases as $\unicode[STIX]{x0394}T_{0}^{2/3}$ for all liquids examined. This observed dependence is rationalized theoretically through consideration of the thermocapillary flows generated within the drop, the bath and the intervening air layer.

The Effect of the Temperature Difference on the Performance of Photovoltaic-Thermoelectric Hybrid Systems

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
M. El Mliles ◽  
Y. El Kouari ◽  
A. Hajjaji
Keyword(s):  
Critical Temperature ◽  
Hybrid System ◽  
Temperature Difference ◽  
Efficiency Enhancement ◽  
Cell Efficiency ◽  
High Power Factor ◽  
Pv Cell ◽  
Te Material ◽  
Increasing Temperature ◽  
Selection Of

The performance of the photovoltaic-thermoelectric (PV-TE) hybrid system was examined using three types of PV cells and a thermoelectric generator (TEG) based on bismuth telluride. The investigated PV cells are amorphous silicon (a-Si), monocrystalline silicon (mono-Si), and cadmium telluride (CdTe). The results showed that the TEG contribution can overcome the degradation of the PV cell efficiency with increasing temperature at the minimal working condition. This condition corresponds to the critical temperature difference across the TEG that guarantees the same efficiency of the hybrid system as that of the PV cell alone at 298 K. The obtained results showed that the critical temperature difference is 13.3 K, 44.1 K, and 105 K for the a-Si, CdTe, and mono-Si PV cell, respectively. In addition, the general expression of the temperature difference across the TEG needed for an efficiency enhancement by a ratio of r compared with a PV cell alone at 298 K was given. For an efficiency enhancement by 5 % (r = 1.05), the temperature difference required is 30.2 K, 61.3 K, and 116.1 K for the a-Si, CdTe, and mono-Si PV cells, respectively. These values cannot be achieved practically only in the case of the a-Si PV cell. Moreover, a TE material with a high power factor can reduce this temperature difference and improve the performance of the hybrid system. This work provides a tool that may be useful during the selection of the PV cell and the TE material for the hybrid system.

An Experimental Synthesis of Quartz, Albite, and Analcite

1950 ◽  
Vol 87 (1) ◽  
pp. 41-44 ◽  
Author(s):  
Gilbert Wilson
Keyword(s):  
Critical Temperature ◽  
Low Temperature ◽  
Temperature Difference ◽  
Quartz Sand ◽  
Sodium Aluminate

AbstractQuartz sand, sodium aluminate and water were heated together in a bomb to above the critical temperature. The apparatus was designed to give a temperature difference of about 100°C. between the two ends of the bomb. Quartz, albite, and analcite were formed in the low temperature end of the bomb.

Convective temperature oscillations in molten gallium

1974 ◽  
Vol 64 (3) ◽  
pp. 565-576 ◽  
Author(s):  
D. T. J. Hurle ◽  
E. Jakeman ◽  
C. P. Johnson
Keyword(s):  
Magnetic Field ◽  
Experimental Study ◽  
Critical Temperature ◽  
Transverse Magnetic Field ◽  
Temperature Difference ◽  
Companion Paper ◽  
Transverse Magnetic ◽  
Temperature Oscillations ◽  
Over The Top

An experimental study of the occurrence of temperature oscillations in molten gallium contained in a rectangular boat and heated from the side is reported. The dependence of the critical temperature difference across the boat for which oscillations set in upon the boat dimensions and upon the strength of a transverse magnetic field is described. The dependence of the frequency of oscillation on these parameters is also reported together with measurements of the variation of the phase of the oscillations over the top surface of the melt. The results are discussed in relation to the theory in the companion paper by Gill (1974).

An Approximate Analysis of the Influence of Aerodynamic Heating and Initial Twist on the Torsional Stiffness of Thin Wings

1960 ◽  
Vol 27 (2) ◽  
pp. 332-334
Author(s):  
Lit S. Han
Keyword(s):  
Critical Temperature ◽  
Temperature Difference ◽  
Torsional Stiffness ◽  
Aerodynamic Heating ◽  
Approximate Analysis ◽  
Fiber Stress ◽  
Aspect Ratios ◽  
Thin Wing ◽  
Approximate Formulas

In the present paper, approximate formulas are derived, based on the “fiber-stress” concept, for the combined influence of aerodynamic heating and initial twist on the torsional stiffness of a thin wing. Criteria are established for calculating the critical temperature difference between that of the edges and that of the mid-chord position, for preventing possible aeroelastic reversals or buckling. Formulas are valid for wings with large aspect ratios.

On the stability of a fluid heated from below

1950 ◽  
Vol 204 (1078) ◽  
pp. 297-309 ◽  
Keyword(s):  
Critical Temperature ◽  
Temperature Difference ◽  
Heated Surface ◽  
Lower Surface ◽  
Absolute Temperature ◽  
Infinite Plane ◽  
Onset Of Convection ◽  
Deep Layers ◽  
The Absolute ◽  
Rigid Plane

In 1916 Lord Rayleigh showed that in certain circumstances a layer of fluid contained between two infinite plane horizontal surfaces could remain at rest with the density increasing upwards, and he enunciated a criterion which allows the critical temperature difference for the onset of convection to be found in terms of the depth of the fluid, the viscosity and conductivity of the gas and a reference temperature, such as the absolute temperature of the lower (heated) surface. His result was extended to a fluid bounded by two rigid plane surfaces by Jeffreys, and in this form has been examined experimentally by K. Chandra (using air) and D. T. E. Dassanayake (using carbon dioxide). Their results show (i) that the Rayleigh-Jeffreys criterion is confirmed for relatively deep layers, (ii) that in relatively shallow layers an entirely distinct mode (‘columnar’), which does not satisfy the Rayleigh-Jeffreys criterion, is initiated and (iii) that this mode passes into another mode when the temperature of the lower surface is greatly increased, at temperature differences which agree approximately with Rayleigh-Jeffreys criterion. The problem has been re-examined in the present paper, on the assumption that the new mode found by Chandra and Dassanayake arises from instability in a shallow boundary layer, whose depth is unrelated to the distance between the upper and lower rigid boundaries. It is shown that the criterion for the ‘columnar’ mode involves only the ratio of the absolute temperatures of the upper and lower surfaces, and an expression is derived and verified for the critical temperature difference at which the transition takes place from the ‘columnar’ to the ‘cellular’ mode. Finally, it is shown that the Rayleigh mode will occur if the depth of the fluid exceeds a certain value, but that for the more shallow layers, the ‘columnar’ mode will be generated initially, ultimately passing to the ‘cellular’ mode for increased temperature difference.

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