A FLUID SYSTEM FOR TRANSFERRING HEAT OVER SMALL TEMPERATURE GRADIENTS WITHOUT FORCED CIRCULATION

1940 ◽  
Vol 18a (8) ◽  
pp. 144-150
Author(s):  
W. H. Cook ◽  
T. A. Steeves
Keyword(s):  
Liquid Ammonia ◽  
Temperature Gradients ◽  
Fluid System ◽  
Small Temperature ◽  
Thermostatic Control ◽  
Forced Circulation ◽  
Temperature Variations ◽  
Spatial Temperature

An enclosed system of piping partly filled with liquid ammonia was found to transfer useful quantities of heat to a bunker containing a solid refrigerant (ice), with temperature gradients of 30 to 50° F. without the use of forced circulation. The system could be adapted to reduce spatial temperature variations and provide thermostatic control where solid refrigerants are used, as in railway refrigerator cars. Such arrangements are discussed briefly.

REDUCTION OF SPATIAL TEMPERATURE VARIATIONS IN AIR-COOLED STORAGE ROOMS. II.

1946 ◽  
Vol 24f (5) ◽  
pp. 380-395
Author(s):  
J. W. Hopkins ◽  
T. A. Steeves ◽  
W. H. Cook
Keyword(s):  
Vertical Distribution ◽  
Heat Load ◽  
Air Flow ◽  
Temperature Gradients ◽  
Single Factor ◽  
Temperature Variations ◽  
Storage Room ◽  
End To End ◽  
Practical Implications ◽  
Spatial Temperature

Measurements made under a series of imposed conditions of heat load, dunnage spacing, and air flow were in agreement with previous work in this laboratory in demonstrating (a) the occurrence of appreciable permanent temperature gradients in material, whether exothermic or not, stacked in an air-cooled storage room, and (b) the possibility of markedly reducing these gradients by effective channelling of air through the stack. With end-to-end circulation, blocking of voids in the room was the most important single factor in minimizing intra-stack temperature differentials under the conditions of these tests. Further improvement was effected by the provision of optimum dunnage and by augmenting the air flow. It is to be inferred that with blocked voids, dunnage should be extended to all external surfaces of the stack. The desirability of uniform transverse and vertical distribution of the circulating air was also evident. Further trials on a larger scale are required to explore the practical implications of these findings.

scholarly journals Cardiac Spiral Wave Drifting Due to Spatial Temperature Gradients – a Numerical Study

2018 ◽  
Author(s):  
Guy Malki ◽  
Sharon Zlochiver
Keyword(s):  
Numerical Simulations ◽  
Single Cell ◽  
Numerical Study ◽  
Spiral Wave ◽  
Spiral Waves ◽  
Temperature Gradients ◽  
Effect Of Temperature ◽  
Local Perturbation ◽  
Marginal Effect ◽  
Spatial Temperature

ABSTRACTCardiac rotors are believed to be a major driver source of persistent atrial fibrillation (AF), and their spatiotemporal characterization is essential for successful ablation procedures. However, electrograms guided ablation have not been proven to have benefit over empirical ablation thus far, and there is a strong need of improving the localization of cardiac arrhythmogenic targets for ablation. A new approach for characterize rotors is proposed that is based on induced spatial temperature gradients (STGs), and investigated by theoretical study using numerical simulations. We hypothesize that such gradients will cause rotor drifting due to induced spatial heterogeneity in excitability, so that rotors could be driven towards the ablating probe. Numerical simulations were conducted in single cell and 2D atrial models using AF remodeled kinetics. STGs were applied either linearly on the entire tissue or as a small local perturbation, and the major ion channel rate constants were adjusted following Arrhenius equation. In the AF-remodeled single cell, recovery time increased exponentially with decreasing temperatures, despite the marginal effect of temperature on the action potential duration. In 2D models, spiral waves drifted with drifting velocity components affected by both temperature gradient direction and the spiral wave rotation direction. Overall, spiral waves drifted towards the colder tissue region associated with global minimum of excitability. A local perturbation with a temperature of T=28°C was found optimal for spiral wave attraction for the studied conditions. This work provides a preliminary proof-of-concept for a potential prospective technique for rotor attraction. We envision that the insights from this study will be utilize in the future in the design of a new methodology for AF characterization and termination during ablation procedures.

Clustering of the resonant triads induced by vertical-shear instability in astrophysical discs

2020 ◽  
Vol 499 (3) ◽  
pp. 3222-3232
Author(s):  
Yuri Shtemler ◽  
Michael Mond
Keyword(s):  
Characteristic Frequency ◽  
Characteristic Time ◽  
Temperature Gradients ◽  
Shear Instability ◽  
Vertical Shear ◽  
Higher Dimension ◽  
Small Temperature ◽  
Common Mode ◽  
Vertical Speed ◽  
Resonant Triads

ABSTRACT Clustering of resonant triads that are induced by vertical-shear instability (VSI), driven by the combined effect of the vertical speed shear and small temperature gradients, is studied for vertically isothermal thin unmagnetized Keplerian discs. The authors’ recent study of isolated VSI resonant triads is extended to illustrate their clustering. The coupling conditions for two VSI resonant triads with one common mode are derived and generalized to higher dimension clustering. The clustering of two, three, and four triads connected via one common mode is numerically simulated. The numerical simulations demonstrate the chaotization of non-linear oscillations about the prototypes of the linearly stable modes with a growing cluster’s dimension that is accompanied by a decrease of the characteristic time of chaotization and an increase of the characteristic frequency of perturbations. The chaos associated with the VSI resonant clustering is believed to precede transition to sustainable turbulence in astrophysical discs.

scholarly journals Small temperature variations are a key regulator of reproductive growth and assimilate storage in oil palm (Elaeis guineensis)

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Naoki Tani ◽  
Zubaidah Aimi Abdul Hamid ◽  
Natra Joseph ◽  
Othman Sulaiman ◽  
Rokiah Hashim ◽  
...  
Keyword(s):  
Oil Palm ◽  
Elaeis Guineensis ◽  
Reproductive Growth ◽  
Small Temperature ◽  
Temperature Variations

scholarly journals Effect of small temperature variations on the tensile behaviourof Ti-6Al-4V

2011 ◽  
Vol 10 ◽  
pp. 2330-2335 ◽  
Author(s):  
J. Galán López ◽  
J. Peirs ◽  
P. Verleysen ◽  
J. Degrieck
Keyword(s):  
Small Temperature ◽  
Temperature Variations

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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