scholarly journals Experimental Study of Intermetallic Diffusion in Large Temperature Gradients

1961 ◽  
Vol 32 (5) ◽  
pp. 945-950 ◽  
Author(s):  
C. J. Meechan
Keyword(s):  
Experimental Study ◽  
Temperature Gradients ◽  
Large Temperature ◽  
Intermetallic Diffusion

scholarly journals A Computer Programme With Temperature Gradient Capability for the Network Analysis of Hybrid Circuits

1980 ◽  
Vol 6 (3-4) ◽  
pp. 227-229
Author(s):  
Carl R. Zimmer
Keyword(s):  
Thermal Analysis ◽  
Input Data ◽  
Steady State Solution ◽  
Temperature Gradients ◽  
Large Temperature ◽  
Computer Programme ◽  
System Operation ◽  
Linear Network ◽  
Periodic Inputs ◽  
Additional Option

A modified version of the computer programme SINC-S is described which permits the user to specify independently up to 30 different device temperatures in a given problem when the proper control statement is included. An additional option is an algorithm for the steady-state solution of a non-linear network with periodic inputs, so that realistic system operation may be simulated. The programme may be used to provide more accurate simulation of circuits where large temperature gradients are present, and to furnish input data for other thermal analysis programmes

Thermal Rectification by Ballistic Phonons

2008 ◽  
Author(s):  
John Miller ◽  
Wanyoung Jang ◽  
Chris Dames
Keyword(s):  
Distribution Function ◽  
Mean Free Path ◽  
Temperature Gradients ◽  
Reverse Direction ◽  
Large Temperature ◽  
Thermal Rectification ◽  
Einstein Distribution ◽  
Ballistic Phonons ◽  
Dimensional Electron Gas ◽  
Bose Einstein

In analogy to the asymmetric transport of electricity in a familiar electrical diode, a thermal rectifier transports heat more favorably in one direction than in the reverse direction. One approach to thermal rectification is asymmetric scattering of phonons and/or electrons, similar to suggestions in the literature for a sawtooth nanowire [1] or 2-dimensional electron gas with triangular scatterers [2]. To model the asymmetric heat transport in such nanostructures, we have used phonon ray-tracing, focusing on characteristic lengths that are small compared to the mean free path of phonons in bulk. To calculate the heat transfer we use a transmission-based (Landauer-Buttiker) method. The system geometry is described by a four-dimensional transfer function that depends on the position and angle of phonon emission and absorption from each of two contacts. At small temperature gradients, the phonon distribution function is very close to the usual isotropic equilibrium (Bose-Einstein) distribution, and there is no thermal rectification. In contrast, at large temperature gradients, the anisotropy in the phonon distribution function becomes significant, and the resulting heat flux vs. temperature curve (analogous to I-V curve of a diode) reveals large thermal rectification.

Effects of Inlet Temperature Gradients on Turbomachinery Performance

1975 ◽  
Vol 97 (1) ◽  
pp. 64-71 ◽  
Author(s):  
B. Lakshminarayana
Keyword(s):  
Combustion Chamber ◽  
Secondary Flow ◽  
Gas Turbines ◽  
Secondary Flows ◽  
Temperature Gradients ◽  
Large Temperature ◽  
Inlet Temperature ◽  
Temperature Profiles ◽  
Blade Row

An analysis is carried out to predict the nature and magnitude of secondary flows induced by temperature gradients in turbomachinery stator and rotor. The effect of this thermal driven secondary flow is severe in gas turbines, due to large temperature gradients that exist at the outlet of the combustion chamber. Secondary flows change the temperature profiles at the exit of the blade row and generate thermal wakes. A method of incorporating these effects into the calculation of gas, blade and casing temperatures in a turbine is demonstrated through an example.

CHALLENGES AND METHODS IN ANALYZES OF THE HEAT TRANSFER IN POLYMER DRY BEARINGS

Tribologia ◽  
2018 ◽  
Vol 282 (6) ◽  
pp. 71-78
Author(s):  
Krzysztof KASZA ◽  
Łukasz MATYSIAK ◽  
Artur KRÓL
Keyword(s):  
Numerical Model ◽  
Measurement Errors ◽  
Temperature Sensors ◽  
Temperature Gradients ◽  
Maximum Temperature ◽  
Large Temperature ◽  
Internal Temperature ◽  
Require Temperature ◽  
Polymer Bearing ◽  
Load Conditions

Heat generation and dissipation in dry polymer bearings are important aspects in their design and operation, because the overheating may lead to fast wear or product damage. The estimation of the maximum temperature under defined load conditions is crucial, but it is also a challenging task. Firstly, it is difficult to measure temperature directly at the contact surface between the bearing and the shaft. Secondly, thermocouples that are commonly used as the temperature sensors might create measurement errors. The work presented in this paper utilizes the numerical model of a polymer bearing for the analysis of the internal temperature field. The model is validated with use of experimental data; and, in order to mitigate the measurement errors of the thermocouple sensor, their geometry and properties are included in the simulation model. The achieved agreement between simulation and experimental temperatures is 10% on average, and it is judged that the numerical model may be applied for thermal analysis of the polymer bearing. The obtained results confirm the influence of the thermocouples with metallic sheaths on the temperature distribution inside the tested polymer bearing. It is shown that the value of the measurement errors depends on the layout of thermocouples and might be significantly reduced by their proper arrangement. It is believed that the presented approach for the analysis of thermal performance of dry polymer bearings might be applied to similar cases, which are characterized by large temperature gradients and require temperature sensors, that are made of the materials of high thermal conductivity.

The phosphorus-31 and metal nuclear magnetic resonance spectra of complexes of tin(II) and lead(II) with tricyclohexylphosphine oxide, sulfide, and selenide

1982 ◽  
Vol 60 (23) ◽  
pp. 2921-2926 ◽  
Author(s):  
Philip A. W. Dean
Keyword(s):  
High Field ◽  
Nmr Spectra ◽  
Chemical Shifts ◽  
Temperature Gradients ◽  
Large Temperature ◽  
Linear Variation ◽  
Small Temperature ◽  
Nuclear Magnetic Resonance Spectra ◽  
Small Temperature Variation ◽  
Reduced Temperature

The new stannous and plumbous complexes M(OP(C6H11)3)n2+ (n = 2 or 3, M = Sn or Pb) and [M(SP(C6H11)3)x(SeP-(C6H11)3)3−x]2+ (M = Sn or Pb) have been prepared in SO2 solution and characterized by their reduced temperature slow-exchange 31P and metal (119Sn or 207Pb) nmr spectra. No evidence could be found for complexes in which both OP(C6H11)3 and EP(C6H11)3 (E = S or Se) are coordinated to tin(II) or lead(II). The same pattern of chemical shifts is found in the 119Sn and 207Pb nmr spectra: δM(M(OP(C6H11)3)22+) < δM(M(OP(C6H11)3)32+ < δM(M(SP(C6H11)3)32+) < δM(M(SeP(C6H11)3)32+) and a monotonic but non-linear variation of δM with x for [M(SP(C6H11)3)x(SeP(C6H11)3)3−x]2+. From M(AsF6)2 in SO2 as reference, the range of the metal chemical shifts is 999–2079 ppm and 2407–7707 ppm in the 119Sn and 207Pb nmr spectra respectively. In the 31P nmr spectra, all of the appropriate two-bond M—P couplings are observed, but the fine structure expected from coupling to 31P could not always be observed in those metal nmr spectra which were measured at high field; it is suggested that these metal nmr spectra are "smeared out" by a combination of large temperature sensitivity of the metal chemical shifts and the small temperature variation allowed by the nmr spectrometer temperature controller and/or diffusion along any temperature gradients present along the length of the nmr sample.

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