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.

Theoretical Aspccts of Cloud Drop Distributions

1949 ◽  
Vol 2 (3) ◽  
pp. 376 ◽  
Author(s):  
EB Kraus ◽  
B Smith
Keyword(s):  
Cooling Rate ◽  
Drop Size ◽  
Initial Temperature ◽  
Theoretical Study ◽  
Air Pressure ◽  
Size Spectrum ◽  
Condensation Nuclei ◽  
Cloud Drop ◽  
Rate Of Cooling

A theoretical study indicates that the number and size of the drops formed in a cloud vary with the rate of cooling, the initial temperature, and the air pressure. The faster the cooling rate, the lower the initial temperature, and the lower the altitude, the greater is the number of drops and the smaller their size. The drop size spectrum also depends, to a large extent, on the number of available condensation nuclei. Furthermore, it tends to be widened by sedimentation and turbulence.

Characterizing the Effect of Processing Parameters on Temperature Distribution of 7075 Aluminum Alloy Slurry Prepared by Enthalpy Control Process

2022 ◽  
Vol 327 ◽  
pp. 263-271
Author(s):  
Gan Li ◽  
Jin Kang Peng ◽  
En Jie Dong ◽  
Juan Chen ◽  
Hong Xing Lu ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Temperature Difference ◽  
Initial Temperature ◽  
Control Process ◽  
Processing Parameters ◽  
Heating Time ◽  
7075 Aluminum Alloy ◽  
Semi Solid ◽  
7075 Alloy ◽  
Slurry Preparation

There is a strong demand for high-strength aluminum alloys such as 7075 aluminum alloy to be applied for rheocasting industry. The overriding challenge for the application of 7075 alloy is that its solid fraction is very sensitive to the variation of temperature in the range of 40% ~ 50% solid fraction, which inevitably narrows down the processing window of slurry preparation for rheocasting process. Therefore, in this work, a novel method to prepare semi-solid slurry of the 7075 alloy, so called Enthalpy Control Process (ECP), has been developed to grapple with this issue. In the method, a medium-frequency electromagnetic field was applied on the outside of slurry preparation crucible to reduce the temperature difference throughout the slurry. The effect of processing parameters, including heating power, heating time, the initial temperature of crucible and melt weight, on the temperature field of the semi-solid slurry was investigated. The results exhibited that although the all the processing parameters had a great influence on the average temperature of the slurry, heating time was the main factor affecting the maximum temperature difference of the slurry. The optimum processing parameters during ECP were found to be heating power of 7.5 KW, the initial temperature of crucible of 30 °C ~ 200 °C and melt weight of 2 kg.

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.

The Flammability Limits of Hydrogen and Methane in Air at Moderately Elevated Temperatures

1997 ◽  
Author(s):  
B. B. Ale ◽  
I. Wierzba
Keyword(s):  
Residence Time ◽  
Initial Temperature ◽  
Elevated Temperatures ◽  
Hydrogen Oxidation ◽  
Initial Mixture ◽  
Spark Ignition ◽  
Stainless Steel Surface ◽  
Flammability Limits ◽  
Simple Method ◽  
The Rich

The flammability limits of hydrogen and methane in air were determined experimentally at elevated initial mixture temperatures up to 350°C at atmospheric pressure for upward flame propagation in a conventional steel test tube apparatus. Additionally the extent to which a prolonged exposure (i.e., residence time) of the mixture to elevated temperatures before spark ignition and, consequently, the existence of pre-ignition reactions that may influence the value of the lean and rich flammability limits was also investigated. It was shown that the flammability limits for methane widened approximately linearly with an increase in the initial mixture temperature over the whole range of temperatures tested. These limits were not affected by the length of the residence time before spark ignition. Different behaviour was observed for flammability limits of hydrogen. They were also widened with an increase in the initial temperature but only up to 200°C. In this initial temperature range the limits were not affected by the length of the residence time. However, at initial temperature exceeding 200°C the flammability limits, especially, the rich limits narrowed with an increase in the temperature and were significantly affected by the residence time before spark ignition. The results of detailed chemical kinetic simulation showed that the gas phase reactions of hydrogen oxidation could not be responsible for the substantial drop in the value of the rich limit. It was therefore, suggested that this drop in the value of the rich limit with the increase in the residence time was caused by the relatively low temperature catalytic reactions on the stainless steel surface of the flame tube. Simple method for calculating the hydrogen conversion to water was proposed. The results of calculations are in fair agreement with the experimental evidence.

Influence of Fluid Viscosity on the Residence Time Distribution of Micro Reactors Made of LTCC

2008 ◽  
Author(s):  
G. A. Groß ◽  
S. Schneider ◽  
B. Schleif ◽  
J. M. Ko¨hler
Keyword(s):  
Residence Time ◽  
Time Distribution ◽  
Residence Time Distribution ◽  
Dispersion Model ◽  
Internal Diameter ◽  
Fluid Viscosity ◽  
Complex Relation ◽  
Micro Flow ◽  
Micro Reactors ◽  
Micro Mixer

The residence time distribution of LTCC microreactors was investigated depending on flow rates and fluid viscosities. A pulse trace experiment was used for monitoring the tracer signals before and behind the microreactors. The tracer signals were measured by use of micro flow-through photometers without disturbing the liquid flow. Therefore, the micro photometers were mounted directly onto FEP tubings. The residence time distribution (RTD) was determined by calculation of the dispersion model using the inlet and outlet tracer profiles. The RTD of a LTCC micro mixer and a LTCC plain meandered channel mixer were determined in the flow rate range between 50 μL/min and 3 000 μL/min using water and aqueous glycerol mixtures up to a glycerol content of 50%. Received data were compared with a PTFE tube (1 mm internal diameter) as reference. A complex relation of determined RTDs between the Reynolds number (Re) and the fluid viscosities was found. A significant non-monotonous effect of the fluid viscosity was observed. The RTD as well as the tailing behavior indicates clearly viscosity-dependent changes in the fluid regime and transport mechanisms.

scholarly journals VII. On the specific heats of gases at constant volume.—Part III. The specific heat of carbon dioxide as a function of temperature

1894 ◽  
Vol 185 ◽  
pp. 961-981
Keyword(s):  
Carbon Dioxide ◽  
Critical Temperature ◽  
Specific Heat ◽  
Lower Limit ◽  
Latent Heat ◽  
Large Scale ◽  
Initial Temperature ◽  
Specific Heats ◽  
Upper Limit ◽  
Points Of Interest

The question of the dependence of the specific heat of carbon dioxide upon its density having been investigated, so far as is described in Part II., the further question remained over as to whether the specific heat of a gas is dependent upons range of temperature over which the gas is heated. The question was evidently within the power of the steam calorimeter to answer, provided arrangements were ride for varying the lower limit of temperature—the initial temperature. To vary upper limit by resorting to vapours other than steam would, on the large scale on which operations were being conducted, have been costly and troublesome, though not attended with any inaccuracy, as the experiments of Wirtz on the Heats of several vapours, determined by the method of condensation, appear show. It is to be observed, indeed, that the use of vapours other than water would .ow of operations being conducted upon smaller quantities of the gas, as it would be sy to find liquids whose vapours possessed a latent heat one-half or one-fourth as eat as that of water; and a construction necessitating but little loss of vapour at experiment could be easily contrived. In this case, also, it would be necessary provide a means of varying the initial temperature. Chiefly on the grounds of supense I decided upon the use of steam in conjunction with a means of altering the initial temperature. It appeared probable, too, that the alteration of the initial temperature between 10° and 100° would disclose the chief points of interest in these of the gas under consideration, the critical temperature lying within this range.

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.

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