Heat and Mass Transfer at Low Temperatures, in a Trapezoidal Closed Cavity

2012 ◽  
Vol 550-553 ◽  
pp. 2996-3003 ◽  
Author(s):  
M.S. Maalem ◽  
A. Benzaoui
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Experimental Study ◽  
Low Temperatures ◽  
The Other ◽  
Flowing Water ◽  
Closed Cavity ◽  
Nusselt Numbers ◽  
Future Paper ◽  
The Mean

An experimental study, in a trapezoidal closed cavity had been led in our laboratory. The considered cavity includes a vaporizing horizontal surface, two condensing ones; one is of glass and the other of aluminium surface. It is cooled down by flowing water. The other walls are thermally isolated. Acquired results allowed to identify the regime of air flow inside the cavity, to assess the mean exchange coefficients of heat and mass, across the three walls and to write a correlation for the mean Sherwood and Nusselt numbers, established for laminar flow regime. These results are important to model many solar uses as solar distillers, solar dryers, etc… We present, in this report experimental results and in a future paper, the written mathematical model and a numerical simulation.

scholarly journals Experimental Study of Natural Convection in a Closed Cavity (Static Type Domestic Fridge)

2021 ◽  
Vol 27 (10) ◽  
pp. 1-19
Author(s):  
Maryem Kanaan Adnan ◽  
Munther Abdullah Mussa
Keyword(s):  
Numerical Simulation ◽  
Experimental Study ◽  
Natural Convection ◽  
Thermal Radiation ◽  
Velocity Distribution ◽  
Thermal Flow ◽  
Closed Cavity ◽  
Glass Door ◽  
And Behavior ◽  
Temperature And Flow Fields

This work provides an analysis of the thermal flow and behavior of the (load-free) refrigerator compartment. The main goal was to compare the thermal behavior inside the refrigerator cavity to the freezer door (home refrigerator) effect and install a fan on the freezer door while neglecting the heat transmitted by thermal radiation. Moreover, the velocity distribution, temperature, and velocity path lines are theoretically studied. This was observed without affecting the shelves inside the cabinet and the egg and butter places on the refrigerator door as they were removed and the aluminum door replaced with a glass door. This study aims to expand our knowledge about the temperature and flow fields of this refrigerator model. Finally, the development of this work highlights the importance of numerical simulation in the search for improvements in the design of this refrigerator model, which may assist refrigerator manufacturers.

Direct Numerical Simulation of Forced Convective Heat Transfer From a Heated Rotating Sphere in Laminar Flows

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
Zhi-Gang Feng
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Density Function ◽  
Heat Diffusion ◽  
Rotating Sphere ◽  
Nusselt Numbers ◽  
Flow Reynolds Number ◽  
The Mean ◽  
Simulation Results

The laminar forced convection of a heated rotating sphere in air has been studied using a three-dimensional immersed boundary based direct numerical simulation method. A regular Eulerian grid is used to solve the modified momentum and energy equations for the entire flow region simultaneously. In the region that is occupied by the rotating sphere, a moving Lagrangian grid is used, which tracks the rotational motion of the particle. A force density function or an energy density function is introduced to represent the momentum interaction or thermal interaction between the sphere and fluid. This numerical method is validated by comparing simulation results with analytical solutions of heat diffusion problem and other published experimental data. The flow structures and the mean Nusselt numbers for flow Reynolds number ranging from 0 to 1000 are obtained. We compared our simulation results of the mean Nusselt numbers with the correlations from the literature and found a good agreement for flow Reynolds number greater than 500; however, a significant discrepancy arises at flow Reynolds number below 500. This leads us to develop a new equation that correlates the mean Nusselt number of a heated rotating sphere for flows of 0≤Re≤500.

scholarly journals Histopathologic evaluation of the peritoneum exposed to heat shock: experimental study in rats

2007 ◽  
Vol 22 (5) ◽  
pp. 342-350 ◽  
Author(s):  
João Vieira Lopes ◽  
Paulo Gonçalves de Oliveira ◽  
João Batista de Sousa ◽  
Sonia Nair Báo ◽  
Gustavo Henrique Soares Takano ◽  
...  
Keyword(s):  
Experimental Study ◽  
High Temperature ◽  
Heat Shock ◽  
The Other ◽  
Nacl Solution ◽  
Electronic Microscopy ◽  
Vascular Congestion ◽  
Histopathologic Evaluation ◽  
The Mean ◽  
And Control

PURPOSE: To evaluate histopathologic alterations of the peritoneum exposed to heat shock. METHODS: Sixty rats were randomly distributed into 6 groups: Heat Shock (HS), High Temperature (HT), Body Temperature (BT), Temperature 0oC (TZ), Sham (SH) and Control (CG) with 10 animals each. The peritoneal cavity of animals from groups HS, HT, BT and TZ was irrigated with NaCl solution 0.9% at temperatures 50ºC, 0ºC, 50ºC, 37ºC and 0ºC, respectively. For animals from group SH, the procedures were simulated and those from group CG, laparotomy and biopsies were conducted. Twenty-four hours later, biopsies of the peritoneum for exams under light and electronic microscopy were performed. RESULTS: Edema was found in groups HS 80%, HT 60%, BT 30% TZ 70%, SH 40% and CG 30%. Vascular congestion was found in groups HS 20%, HT 30%, BT 10% and TZ 20%. Erythrocyte extravasation was found in groups HT 60% and SH 10%. Mesothelium destruction was found in 100% of specimens from groups HS, HT, BT, TZ, SH and CG 90%. Necrosis was found in groups HS 30%, HT 20% and BT 10%. The mean peritoneal thickness ranged from 42.26 µm (TZ) to 26.42 µm (CG). CONCLUSION: The heat shock caused no deaths, but promoted significant peritoneal edema without affecting the other histopathologic indicatives.

scholarly journals Effect of a New Cardiac Massage Facilitator Device on the Fatigue of Rescue Workers in Cardiopulmonary Resuscitation

2020 ◽  
Vol 6 (1) ◽  
pp. 13-16
Author(s):  
Mohamad Amin Younessi Heravi ◽  
Zakiyeh Amini ◽  
Mostafa Roshanravan ◽  
Akram Gazerani
Keyword(s):  
Experimental Study ◽  
Cardiopulmonary Resuscitation ◽  
The Other ◽  
Cardiac Massage ◽  
Analog Scale ◽  
Rescue Workers ◽  
Significant Difference ◽  
Fatigue Severity ◽  
The Mean

AbstractIntroduction: Cardiopulmonary resuscitation is a direct intervention for the prevention or postponement of death in patients with cardiac arrest. The fatigue of rescue workers is of high significance when performing cardiopulmonary resuscitation effectively. The present study aimed to investigate the effect of a cardiac massage facilitator device on the fatigue of rescue workers in cardiopulmonary resuscitation.Materials and Methods: This experimental study was carried out on 30 emergency medical aid non-continuous bachelor students, divided equally into two groups: one group performed cardiac massage using the device and the other without the device. Fatigue levels were assessed using a visual analog scale to evaluate fatigue severity.Results: The mean age of participants was 23.42 ± 2.02 years, the mean height was 175 ± 4.43 cm, and the mean weight was 65.45 ± 5.02 kg. There was a statistically significant difference between the mean fatigue scores of the two groups: 0.06 with the device vs. 0.57 without the device.Conclusion: Our results suggest that the cardiac massage facilitator device presented in this study could be effective in improving the quality of cardiac massage and be helpful in cardiopulmonary resuscitation.

scholarly journals A Mathematical Model to Study the Effect of Travel Between Two Regions on the Covid-19 Infections

2020 ◽  
Vol 1 (2) ◽  
pp. 75-84
Author(s):  
Mochammad Andhika Aji Pratama
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Reproduction Number ◽  
The Other ◽  
Susceptible Population ◽  
Significant Parameter ◽  
Numerous Model ◽  
Model Predictions ◽  
The Stability ◽  
The Basic Reproduction Number

COVID-19 has attracted a lot of researchers’ attention since it has emerged in Wuhan, China in December 2019. Numerous model predictions on the COVID-19 epidemic have been created in case of Wuhan and the other regions. In this paper, a new COVID-19 epidemic model between two regions is proposed. The model differentiates asymptomatic infectious compartment and symptomatic infectious compartment. It is assumed that the symptomatic population cannot infect the susceptible population due to direct isolation, but the asymptomatic population can. The symptomatic population is also assumed to be unable to travel between regions. We analyze the stability of the model using Lyapunov Function. The Basic Reproduction Number for the model is presented. The numerical simulation and sensitivity analysis are explored to determine the significant parameter of the model.

A prey - partially dependent predator with a reserved zone: modelling and analysis

2015 ◽  
Vol 5 (1) ◽  
pp. 1
Author(s):  
M.V. Ramana Murthy ◽  
Dahlia Khaled
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
Lyapunov Function ◽  
Functional Response ◽  
Equilibrium Points ◽  
Dynamical Behavior ◽  
The Other ◽  
Local Bifurcation ◽  
Control Parameters ◽  
Persistence Conditions

<p>In this paper, a mathematical model consisting of a prey-partially dependent predator has been proposed and analyzed. It is assumed that the prey moving between two types of zones, one is assumed to be a free hunting zone that is known as an unreserved zone and the other is a reserved zone where hunting is prohibited. The predator consumes the prey according to the Beddington-DeAngelis type of functional response. The existence, uniqueness and boundedness of the solution of the system are discussed. The dynamical behavior of the system has been investigated locally as well as globally with the help of Lyapunov function. The persistence conditions of the system are established. Local bifurcation near the equilibrium points has been investigated. Finally, numerical simulation has been used to specify the control parameters and confirm the obtained results.</p>

Multi-Center Study of Thromboplastin Calibration Precision – Influence of Reagent Species, Composition, and International Sensitivity Index (ISI)

1993 ◽  
Vol 69 (01) ◽  
pp. 035-040 ◽  
Author(s):  
A M H P van den Besselaar ◽  
R M Bertina
Keyword(s):  
Oral Anticoagulants ◽  
International Normalized Ratio ◽  
The Other ◽  
World Health ◽  
Rabbit Brain ◽  
Sensitivity Index ◽  
Bovine Plasma ◽  
Significant Difference ◽  
The Mean ◽  
International Sensitivity Index

SummaryFour thromboplastin reagents were tested by 18 laboratories in Europe, North-America, and Australasia, according to a detailed protocol. One thromboplastin was the International Reference Preparation for ox brain thromboplastin combined with adsorbed bovine plasma (coded OBT/79), and the second was a certified reference material for rabbit brain thromboplastin, plain (coded CRM 149R). The other two thromboplastin reagents were another rabbit plain brain thromboplastin (RP) with a lower ISI than CRM 149R and a rabbit brain thromboplastin combined with adsorbed bovine plasma (RC). Calibration of the latter two reagents was performed according to methods recommended by the World Health Organization (W. H. O.).The purpose of this study was to answer the following questions: 1) Is the calibration of the RC reagent more precise against the bovine/combined (OBT/79) than against the rabbit/plain reagent (CRM 149R)? 2) Is the precision of calibration influenced by the magnitude of the International Sensitivity Index (ISI)?The lowest inter-laboratory variation of ISI was observed in the calibration of the rabbit/plain reagent (RP) against the other rabbit/plain reagent (CRM 149R) (CV 1.6%). The highest interlaboratory variation was obtained in the calibration of rabbit/plain (RP) against bovine/combined (OBT/79) (CV 5.1%). In the calibration of the rabbit/combined (RC) reagent, there was no difference in precision between OBT/79 (CV 4.3%) and CRM 149R (CV 4.2%). Furthermore, there was no significant difference in the precision of the ISI of RC obtained with CRM 149R (ISI = 1.343) and the rabbit/plain (RP) reagent with ISI = 1.14. In conclusion, the calibration of RC could be performed with similar precision with either OBT/79 or CRM 149R, or RP.The mean ISI values calculated with OBT/79 and CRM 149R were practically identical, indicating that there is no bias in the ISI of these reference preparations and that these reference preparations have been stable since their original calibration studies in 1979 and 1987, respectively.International Normalized Ratio (INR) equivalents were calculated for a lyophilized control plasma derived from patients treated with oral anticoagulants. There were small but significant differences in the mean INR equivalents between the bovine and rabbit thromboplastins. There were no differences in the interlaboratory variation of the INR equivalents, when the four thromboplastins were compared.

Prothrombin Time Standardization: Report of the Expert Panel on Oral Anticoagulant Control

1979 ◽  
Vol 42 (04) ◽  
pp. 1073-1114 ◽  
Keyword(s):  
Prothrombin Time ◽  
Expert Panel ◽  
The Other ◽  
Rabbit Brain ◽  
Calibration Constant ◽  
Freeze Dried ◽  
The Mean ◽  
Point Of Intersection ◽  
And Control ◽  
Standardization Report

SummaryIn collaborative experiments in 199 laboratories, nine commercial thromboplastins, four thromboplastins held by the National Institute for Biological Standards and Control (NIBS & C), London and the British Comparative Thromboplastin were tested on fresh normal and coumarin plasmas, and on three series of freeze-dried plasmas. One of these was made from coumarin plasmas and the other two were prepared from normal plasmas; in each series, one plasma was normal and the other two represented different degrees of coumarin defect.Each thromboplastin was calibrated against NIBS&C rabbit brain 70/178, from the slope of the line joining the origin to the point of intersection of the mean ratios of coumarin/normal prothrombin times when the ratios obtained with the two thromboplastins on the same fresh plasmas were plotted against each other. From previous evidence, the slopes were calculated which would have been obtained against the NIBS&C “research standard” thromboplastin 67/40, and termed the “calibration constant” of each thromboplastin. Values obtained from the freeze-dried coumarin plasmas gave generally similar results to those from fresh plasmas for all thromboplastins, whereas values from the artificial plasmas agreed with those from fresh plasmas only when similar thromboplastins were being compared.Taking into account the slopes of the calibration lines and the variation between laboratories, precision in obtaining a patient’s prothrombin time was similar for all thromboplastins.

Platelet Suruival and Function in Rats with Enhanced Thrombotic Tendency

1985 ◽  
Vol 54 (04) ◽  
pp. 739-743 ◽  
Author(s):  
Federica Delaini ◽  
Elisabetta Dejana ◽  
Ine Reyers ◽  
Elisa Vicenzi ◽  
Germana De Bellis Vitti ◽  
...  
Keyword(s):  
Arachidonic Acid ◽  
Nephrotic Syndrome ◽  
Platelet Function ◽  
Laboratory Tests ◽  
Thrombus Formation ◽  
The Other ◽  
Mean Survival Time ◽  
The Mean ◽  
And Function ◽  
Thrombotic Tendency

SummaryWe have investigated the relevance of some laboratory tests of platelet function in predicting conditions of thrombotic tendency. For this purpose, we studied platelet survival, platelet aggregation in response to different stimuli, TxB2 and 6-keto-PGFlα production in serum of rats bearing a nephrotic syndrome induced by adriamycin. These animals show a heavy predisposition to the development of both arterial and venous thrombosis. The mean survival time was normal in nephrotic rats in comparison to controls. As to aggregation tests, a lower aggregating response was found in ADR-treated rats using ADP or collagen as stimulating agents. With arachidonic acid (AA) we observed similar aggregating responses at lower A A concentrations, whereas at higher AA concentrations a significantly lower response was found in nephrotic rats, despite their higher TxB2 production. Also TxB2 and 6-keto-PGFlα levels in serum of nephrotic rats were significantly higher than in controls. No consistent differences were found in PGI2-activity generated by vessels of control or nephrotic rats.These data show that platelet function may appear normal or even impaired in rats with a markedly increased thrombotic tendency. On the other hand, the significance of high TxB2 levels in connection with mechanisms leading to thrombus formation remains a controversial issue.

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