An Experimental Study of Plane Plumes in Cold Water

1983 ◽  
Vol 105 (2) ◽  
pp. 248-254 ◽  
Author(s):  
Y. Joshi ◽  
B. Gebhart
Keyword(s):  
Buoyancy Force ◽  
Cold Water ◽  
Pure Water ◽  
Density Variation ◽  
Complex Flow ◽  
Flow Temperature ◽  
Ambient Temperatures ◽  
Density Relation ◽  
Convective Motions ◽  
Extremum Conditions

The peculiar density variation of water with temperature makes the Boussinesq approximations invalid in the vicinity of density extremum conditions. The buoyancy force reversals which often arise from the density extremum have been studied in many recent investigations. The formulation of an accurate density relation has resulted in a simplified analysis for many convective motions. Two such analyses have dealt with the flow generated above a heated line source in cold water, around the extremum point. We present an experimental investigation of such flow. Temperature measurements have been carried out for ambient temperatures, t∞ ≥ tm, the temperature of density extremum, for pure water at atmospheric pressure. These measurements are in satisfactory agreement with the analyses. As the ambient temperature is successively increased above the density extremum temperature, the transformation of the flow behaviour from non-Boussinesq to Boussinesq is very clearly observed. Velocity measurements have been made at t∞=4°C, the extremum temperature. For t∞<tm, very complex flow patterns exist, due to the bidirectional buoyancy force. These patterns have been visualized. The influence of a bounding impermeable surface below the plume source has also been examined.

Natural Convection in a Horizontal Cavity Partially Occupied by a Porous Media Saturated by a Coolant Liquid

2006 ◽  
Author(s):  
Fakhreddine S. Oueslati ◽  
Rachid Bennacer ◽  
Habib Sammouda ◽  
Ali Belghith
Keyword(s):  
Heat Transfer ◽  
Porous Media ◽  
Natural Convection ◽  
Flow Structure ◽  
Boussinesq Approximation ◽  
Density Variation ◽  
Heat Fluxes ◽  
Complex Flow ◽  
Coupled Equations ◽  
Complex Flow Structure

The natural convection is studied in a cavity witch the lower half is filled with a porous media that is saturated with a first fluid (liquid), and the upper is filled with a second fluid (gas). The horizontal borders are heated and cooled by uniform heat fluxes and vertical ones are adiabatic. The formulation of the problem is based on the Darcy-Brinkman model. The density variation is taken into account by the Boussinesq approximation. The system of the coupled equations is resolved by the classic finite volume method. The numerical results show that the variation of the conductivity of the porous media influences strongly the flow structure and the heat transfer as well as in upper that in the lower zones. The effect of conductivity is conditioned by the porosity which plays a very significant roll on the heat transfer. The structures of this flow show that this kind of problem with specific boundary conditions generates a complex flow structure of several contra-rotating two to two cells, in the upper half of the cavity.

Water Temperature and Drowning

PEDIATRICS ◽  
1991 ◽  
Vol 87 (5) ◽  
pp. 747-748
Author(s):  
LINDA QUAN ◽  
KIM R. WENTZ
Keyword(s):  
Water Temperature ◽  
Rectal Temperature ◽  
Cold Water ◽  
Puget Sound ◽  
Swimming Pool ◽  
Ambient Temperatures ◽  
Rapid Induction

In Reply.— Dr Nichter et al propose that the normal or mildly impaired survival of five asystolic children in our series was due to the rapid induction of hypothermia by the cold waters of the Puget Sound area. However, we reported that hypothermia (rectal temperature &lt;34°C) was not associated with increased survival. In addition, the data in the Table show that none of these five children experienced cold-water submersions. The ambient temperatures and thus possibly swimming pool temperatures in this temperate area's summers are certainly less warm than Florida's.

Dual core and shell temperature regulation during sea acclimatization in Gentoo penguins (Pygoscelis papua)

1994 ◽  
Vol 266 (4) ◽  
pp. R1319-R1326 ◽  
Author(s):  
E. Dumonteil ◽  
H. Barre ◽  
J. L. Rouanet ◽  
M. Diarra ◽  
J. Bouvier
Keyword(s):  
Body Temperature ◽  
Metabolic Rate ◽  
Thermal Insulation ◽  
Cold Water ◽  
Threshold Temperature ◽  
Ambient Temperatures ◽  
Adaptation To Cold ◽  
Marine Life ◽  
Shell Temperature ◽  
Skin Temperatures

Penguins are able to maintain a high and constant body temperature despite a thermally constraining environment. Evidence for progressive adaptation to cold and marine life was sought by comparing body and peripheral skin temperatures, metabolic rate, and thermal insulation in juvenile and adult Gentoo penguins exposed to various ambient temperatures in air (from -30 to +30 degrees C) and water (3-35 degrees C). Juvenile penguins in air showed metabolic and insulative capacities comparable with those displayed by adults. Both had a lower critical temperature (LCT) close to 0 degree C. In both adults and juveniles, the intercept of the metabolic curve with the abscissa at zero metabolic rate was far below body temperature. This was accompanied by a decrease in thermal insulation below LCT, allowing the preservation of a threshold temperature in the shell. However, this shell temperature maintenance was progressively abandoned in immersed penguins as adaptation to marine life developed, probably because of its prohibitive energy cost in water. Thus adaptation to cold air and to cold water does not rely on the same kind of reactions. Both of these strategies fail to follow the classical sequence linking metabolic and insulative reactions in the cold.

Buoyancy force reversals in vertical natural convection flows in cold water

1980 ◽  
Vol 97 (02) ◽  
pp. 279 ◽  
Author(s):  
Van P. Carey ◽  
Benjamin Gebhart ◽  
Joseph C. Mollendorf
Keyword(s):  
Natural Convection ◽  
Buoyancy Force ◽  
Cold Water

Inhibition of shivering in hypothermic seals during diving

2005 ◽  
Vol 289 (2) ◽  
pp. R326-R331 ◽  
Author(s):  
Petter H. Kvadsheim ◽  
Lars P. Folkow ◽  
Arnoldus Schytte Blix
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Cold Water ◽  
Brain Temperature ◽  
Muscular Activity ◽  
Emg Activity ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Cystophora Cristata ◽  
Increase Oxygen Consumption

The mammalian response to hypothermia is increased metabolic heat production, usually by way of muscular activity, such as shivering. Seals, however, have been reported to respond to diving with hypothermia, which in other mammals under other circumstances would have elicited vigorous shivering. In the diving situation, shivering could be counterproductive, because it obviously would increase oxygen consumption and therefore reduce diving capacity. We have measured the electromyographic (EMG) activity of three different muscles and the rectal and brain temperature of hooded seals ( Cystophora cristata) while they were exposed to low ambient temperatures in a climatic chamber and while they performed a series of experimental dives in cold water. In air, the seals had a normal mammalian shivering response to cold. Muscles were recruited in a sequential manner until body temperature stopped dropping. Shivering was initiated when rectal temperature fell below 35.3 ± 0.6°C ( n = 6). In the hypothermic diving seal, however, the EMG activity in all of the muscles that had been shivering vigorously before submergence was much reduced, or stopped altogether, whereas it increased again upon emergence but was again reduced if diving was repeated. We conclude that shivering is inhibited during diving to allow a decrease in body temperature whereby oxygen consumption is decreased and diving capacity is extended.

scholarly journals EFFECT OF SLAUGHTERING TECHNIQUES ON THE QUALITY OF FRESH “PATIN SIAM “ CATFISH (Pangasius hypopthalmus) STORED AT AMBIENT TEMPERATURE

2014 ◽  
Vol 9 (2) ◽  
pp. 63
Author(s):  
Diah Ikasari ◽  
Theresia Dwi Suryaningrum
Keyword(s):  
Cold Water ◽  
Abdominal Cavity ◽  
Proximate Analysis ◽  
Plate Count ◽  
Fish Quality ◽  
Flesh Quality ◽  
Ambient Temperatures ◽  
Quality Deterioration ◽  
Microbiological Parameters

Fish handling is one of factors that affect fish quality deterioration, including slaughtering technique. In this study, the quality deterioration of fresh patin Siam catfish (Pangasius hypopthalmus) which were handled with different slaughtering techniques was observed. Fish were fasted for one day before slaughtered with two different techniques namely live-chilling and bleeding techniques. Live-chilling technique was conducted by exposing  fish into cold water with temperature of 0-5°C for 15 minutes, while bleeding technique was conducted by cutting directly on the arteries part of fish head. After being slaughtered, fish were then stored at ambient temperatures for 18 hours and observed for its quality deterioration in every 3 hours. The observed parameters of fish quality deterioration were including the sensory attributes which were described using descriptive test by trained panelists; chemical parameters including proximate analysis; pH and Total Volatile Base (TVB), and microbiological parameters including Total Plate Count (TPC), coliform and E.coli. Results showed that the flesh of patin Siam catfish slaughtered by live-chilling technique had more blood in the fish body tissue, while bleeding technique resulted in much brighter flesh as well as abdominal cavity. The flesh quality decreased after 18 hours of storage in both treatments, but no significant changes in their proximate values. Bleeding technique was more recommended compared to live-chilling technique for slaughtering patin Siam catfish due to its predominance in producing better flesh quality.

scholarly journals A Numerical Research of Heat Transfer in Rectangular Fins with Different Perforations

2019 ◽  
Vol 8 (12S) ◽  
pp. 367-371
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Heat Transfer Rate ◽  
Transfer Rate ◽  
Buoyancy Force ◽  
Temperature Drop ◽  
Density Variation ◽  
Transfer Enhancement ◽  
Enhancement Of Heat Transfer ◽  
Numerical Research

Heat Transfer enhancement needs buoyancy force. This is to be achieved by making perforations on fin surfaces. The present paper is a study on the enhancement of heat transfer in terms of density, velocity and temperature with three different perforation geometry (parallel square, inclined square and circular). CFD was used to carry out the study of density variation, velocity and temperature drop among different perforated fins. This type of perforated fin has an improvement in heat transfer rate over its dimensionally equivalent solid fin.

Buoyancy-induced flows in water under conditions in which density extrema may arise

1978 ◽  
Vol 89 (4) ◽  
pp. 673-707 ◽  
Author(s):  
Benjamin Gebhart ◽  
Joseph C. Mollendorf
Keyword(s):  
Buoyancy Force ◽  
Saline Water ◽  
Density Variation ◽  
Force Density ◽  
Appreciable Effect ◽  
Transport Parameters ◽  
Local Flow ◽  
Thermal Buoyancy ◽  
Temperature Levels ◽  
Very High

The temperature dependence of the density of both pure and saline water, even to very high salinity and pressure levels, decreases at decreasing temperature toward an extremum. The nature of this variation precludes approximating the buoyancy-force density difference linearly with a temperature difference. This peculiar density variation of water has very significant effects, even at environmental temperature levels. A new equation has appeared which relates density to temperature, salinity and pressure with very high accuracy. Its form is especially suited to the analysis of convective motions. We consider here vertical boundary-layer flows. Analysis of flows arising from thermal buoyancy and from combined buoyancy effects shows the simplicity of the formulation. Relatively few new parameters arise. Extensive calculations for thermally buoyant flows show the large magnitude of the effects of the complicated density variation on transport. Buoyancy-force reversals and convective inversions are predicted. The latter are in close agreement with past experiments. A new Grashof number arises which is an accurate indication of the actual local flow vigour. The effects of specific temperature conditions are given in detail. The appreciable effect of the Prandtl number is calculated. Transport parameters are given for salinities and pressures up to 40 p.p.t. and 1000 bars, respectively.

scholarly journals A Microfluidic Device for Automated High Throughput Detection of Ice Nucleation of Snomax®

Micromachines ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 296
Author(s):  
Priyatanu Roy ◽  
Margaret House ◽  
Cari Dutcher
Keyword(s):  
Heat Treatment ◽  
Microfluidic Device ◽  
High Throughput ◽  
Pure Water ◽  
Ice Nucleation ◽  
Food Storage ◽  
Detection Methods ◽  
Microfluidic Platform ◽  
Ambient Temperatures ◽  
Effects Of Aging

Measurement of ice nucleation (IN) temperature of liquid solutions at sub-ambient temperatures has applications in atmospheric, water quality, food storage, protein crystallography and pharmaceutical sciences. Here we present details on the construction of a temperature-controlled microfluidic platform with multiple individually addressable temperature zones and on-chip temperature sensors for high-throughput IN studies in droplets. We developed, for the first time, automated droplet freezing detection methods in a microfluidic device, using a deep neural network (DNN) and a polarized optical method based on intensity thresholding to classify droplets without manual counting. This platform has potential applications in continuous monitoring of liquid samples consisting of aerosols to quantify their IN behavior, or in checking for contaminants in pure water. A case study of the two detection methods was performed using Snomax® (Snomax International, Englewood, CO, USA), an ideal ice nucleating particle (INP). Effects of aging and heat treatment of Snomax® were studied with Fourier transform infrared (FTIR) spectroscopy and a microfluidic platform to correlate secondary structure change of the IN protein in Snomax® to IN temperature. It was found that aging at room temperature had a mild impact on the ice nucleation ability but heat treatment at 95 °C had a more pronounced effect by reducing the ice nucleation onset temperature by more than 7 °C and flattening the overall frozen fraction curve. Results also demonstrated that our setup can generate droplets at a rate of about 1500/min and requires minimal human intervention for DNN classification.

Evidence of a Convective Instability Allowing Warm Water to Freeze in Less Time Than Cold Water

1996 ◽  
Vol 118 (1) ◽  
pp. 65-72 ◽  
Author(s):  
P. K. Maciejewski
Keyword(s):  
Natural Convection ◽  
Flow Field ◽  
Initial Temperature ◽  
Cold Water ◽  
Warm Water ◽  
Cooling Process ◽  
Convective Cooling ◽  
Convective Motions ◽  
Different Levels ◽  
Field Inversion

This experimental study explores the possibility that warm water may freeze in less time than cold water due to natural convection alone, i.e., in the absence of significant cooling by evaporation. This possibility is rooted in the following two hypotheses: (1) The Rayleigh number associated with a sample of warm water may exceed a critical value above which the convective motions within the water sample may become turbulent and enhance the rate of convective cooling, and (2) the inversion of the flow field that is expected to occur in the vicinity of maximum density, i.e., at 4°C, will occur at different points in the cooling process for identical samples of water at different levels of initial temperature and result in an enhanced rate of convective cooling after the flow field inversion for those cases at higher levels of initial temperature that enter the flow field inversion with higher kinetic energy. The results of this study establish that, under certain circumstances, a sample of water that is initially warm will freeze in less time than an identical sample of water that is initially cold due to natural convection alone.

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