scholarly journals Two dimensional temperature distribution model in human dermal region exposed at low ambient temperatures with air flow

2013 ◽  
Vol 8 (2) ◽  
pp. 11-24 ◽  
Author(s):  
DB Gurung
Keyword(s):  
Subcutaneous Tissue ◽  
Air Flow ◽  
Static Condition ◽  
Skin Surface ◽  
Distribution Model ◽  
Two Dimensional ◽  
Ambient Temperatures ◽  
Insensible Perspiration ◽  
Engineering And Technology ◽  
The Mathematical Model

This paper deals with thermo-regulation in human dermal part in a cold atmosphere with significant air flow. The mathematical model involving bio-heat equation has been solved using finite element method and Crank-Nicolson technique to numerically investigate two dimensional temperature distributions. The natural three layers of dermal part – epidermis, dermis, and subcutaneous tissue are considered for the study. The important parameters like blood mass flow rate, metabolic heat generation rate and thermal conductivity are taken distinct in each layer according to their distinct sub-regional activities. The human subject is assumed in static condition. The wind speed is considered in the range from the start of forced convection (? 0.2 m/s) and up to 5 m/s. The loss of heat from the skin surface to the environment is taken due to convection, radiation, and insensible perspiration. Kathmandu University Journal of Science, Engineering and Technology Vol. 8, No. II, December, 2012, 11-24 DOI: http://dx.doi.org/10.3126/kuset.v8i2.7320

Inhibiting ventilatory evaporation produces an adaptive increase in cutaneous evaporation in mourning doves Zenaida macroura

1999 ◽  
Vol 202 (21) ◽  
pp. 3021-3028 ◽  
Author(s):  
T.C. Hoffman ◽  
G.E. Walsberg
Keyword(s):  
Skin Surface ◽  
The Body ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Zenaida Macroura ◽  
Ambient Temperatures ◽  
Rapid Adjustment ◽  
Mourning Doves ◽  
A Minor ◽  
Cutaneous Evaporation

We tested the hypothesis that birds can rapidly change the conductance of water vapor at the skin surface in response to a changing need for evaporative heat loss. Mourning doves (Zenaida macroura) were placed in a two-compartment chamber separating the head from the rest of the body. The rate of cutaneous evaporation was measured in response to dry ventilatory inflow at three ambient temperatures and in response to vapor-saturated ventilatory inflow at two ambient temperatures. At 35 degrees C, cutaneous evaporation increased by 72 % when evaporative water loss from the mouth was prevented, but no increase was observed at 45 degrees C. For both dry and vapor-saturated treatments, cutaneous evaporation increased significantly with increased ambient temperature. Changes in skin temperature made only a minor contribution to any observed increase in cutaneous evaporation. This indicates that Z. macroura can effect rapid adjustment of evaporative conductance at the skin in response to acute change in thermoregulatory demand.

Microangiopathy in Severe Chronic Venous Insufficiency Evaluated by Fluorescence Video-Microscopy

1986 ◽  
Vol 1 (3) ◽  
pp. 159-169 ◽  
Author(s):  
P. Haselbach ◽  
U. Vollenweider ◽  
G. Moneta ◽  
A. Bollinger
Keyword(s):  
Intravenous Injection ◽  
Chronic Venous Insufficiency ◽  
Venous Insufficiency ◽  
Subcutaneous Tissue ◽  
Flow Distribution ◽  
Skin Surface ◽  
Video Microscopy ◽  
Healthy Controls ◽  
Microvascular Flow ◽  
Made In

Fluorescence video microscopy after intravenous injection of Na-fluorescein was used to study capillary morphology, pericapillary halo diameters, microvascular flow distribution and transcapillary diffusion of the dye in 15 healthy controls and 15 patients with severe chronic venous insufficiency (CVI). The recordings were made in the medial ankle region. Transcapillary diffusion was monitored within a densitometer window encompassing 3.2 mm2 of skin surface. Microangiopathy known from previous studies was documented in the patients with severe CVI. The number of skin capillaries within the field of observation was not reduced. In some cases inhomogeneous microvascular flow distribution and probable microthrombosis were detected. Mean halo size averaged 81 — 15 μm in the controls and 146 ± 47 μm in the patients (P < 0.001). Unexpectedly, transcapillary diffusion of Na-fluorescein was not significantly increased in the field of measurement. Possible explanations include asynchronous inflow of the dye, the presence of thrombosed and therefore not perfused capillaries, a pericapillary fibrin layer limiting diffusion and redistribution of flow in favour of the subcutaneous tissue.

Numerical Simulation of Subsea Cluster Manifold Installation by the Sheave Method

2018 ◽  
Author(s):  
Yu Zhao ◽  
Yingying Wang ◽  
Liwei Li ◽  
Chao Yang ◽  
Yang Du ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Mathematical Model ◽  
South China Sea ◽  
Deep Sea ◽  
High Reliability ◽  
Two Dimensional ◽  
Complex Environment ◽  
Lumped Mass ◽  
Lumped Mass Method ◽  
The Mathematical Model

The sheave installation method (SIM) is an effective and non-conventional method to solve the installation of subsea equipment in deep water (>1000m), which has been developed to deploy the 175t Roncador Manifold I into 1,885 meters water depth in 2002. With the weight increment of subsea cluster manifold, how to solve its installation with the high reliability in the deep sea is still a great challenge. In this paper, the installation of the 300t subsea cluster manifold using the SIM is studied in the two-dimensional coordinate system. The mathematical model is established and the lumped mass method is used to calculate the hydrodynamic forces of the wireropes. Taking into account the complex environment loads, the numerical simulation of the lowering process is carried out by OrcaFlex. The displacement and vibration of the subsea cluster manifold in the z-axis direction and the effective tension at the top of the wireropes can be gotten, which can provide guidance for the installation of the cluster manifold in the South China Sea.

Numerical Simulation of Airflow Organization Process during Double Highway Tunnel Fire

2014 ◽  
Vol 501-504 ◽  
pp. 2370-2376
Author(s):  
Hai Yan Wang ◽  
Mei Zhen Chen ◽  
Guo Fa Liu
Keyword(s):  
Pressure Field ◽  
Air Flow ◽  
Concentration Field ◽  
Key Technology ◽  
Tunnel Fire ◽  
Highway Tunnel ◽  
Organization Process ◽  
In Fire ◽  
The Mathematical Model ◽  
And Diffusion

Taking Majiazhai double highway tunnel as a prototype, the mathematical model of double tunnel fire is established to analyze smoke plume spread and diffusion during air flow organization process of highway tunnel fire. In the conditions of double tunnel fire jet fans closed, tunnel jet fans open, ventilators of tunnel and cross-road open simultaneously, the temperature field, pressure field and concentration field of air flow and smoke relative motion are obtained. Then it puts forward that the key technology for smoke countercurrent control in double tunnel fire is to increase the ventilation resistance in fire source upwind cross-road and reduce the air quantity flowing from tunnel jet fans into cross-road.

A 2D Numerical Model for Simulation of Two-Dimensional Circular Dam-Break

2011 ◽  
Vol 130-134 ◽  
pp. 2993-2996
Author(s):  
Ming Qin Liu ◽  
Y.L. Liu
Keyword(s):  
Solution Procedure ◽  
Dam Break ◽  
Curvilinear Coordinates ◽  
Two Dimensional ◽  
Proposed Model ◽  
Curvilinear Coordinate ◽  
Orthogonal Curvilinear Coordinate System ◽  
Orthogonal Curvilinear Coordinates ◽  
Averaged Model ◽  
The Mathematical Model

The purpose of this paper is to present a 2D depth-averaged model under orthogonal curvilinear coordinates for simulating two-dimensional circular dam-break flows. The proposed model uses an orthogonal curvilinear coordinate system efficiently and accurately to simulate the flow field with irregular boundaries. As for the numerical solution procedure, The SIMPLEC solution procedure has been used for the transformed governing equations in the transformed domain. Practical application of the model is illustrated by an example, which demonstrates that the mathematical model can capture hydraulic discontinuities accurately such as steep fronts, hydraulic jump and drop, etc.

Design Parameters for the Housing of Two-Dimensional Air Flow Sensors

2018 ◽  
Vol 18 (24) ◽  
pp. 10154-10162 ◽  
Author(s):  
Reiner Jedermann ◽  
Nico Hartgenbusch ◽  
Mykhailo Borysov ◽  
Walter Lang
Keyword(s):  
Air Flow ◽  
Design Parameters ◽  
Two Dimensional ◽  
Flow Sensors

Temperature regulation

2017 ◽  
Author(s):  
Bareket Falk ◽  
Raffy Dotan
Keyword(s):  
Body Temperature ◽  
Children And Adolescents ◽  
Temperature Regulation ◽  
Heat Dissipation ◽  
Epidemiological Data ◽  
Skin Surface ◽  
Neutral Zone ◽  
Sweat Loss ◽  
Ambient Temperatures ◽  
Dry Heat

Under all but the most extreme environmental heat conditions, children control their body temperature (at rest and during exercise) as well as adults. Children, however, use a different thermoregulatory strategy. Compared with adults, children rely more on dry heat dissipation and less on evaporative cooling (sweating). Their larger skin surface-area relative to mass does put children at increasing disadvantage, relative to adults, as ambient temperatures rise above skin temperature. Similarly, they become increasingly disadvantaged upon exposure to decreasing temperatures below the thermo-neutral zone. Like adults, children inadvertently dehydrate while exercising in hot conditions and are often hypohydrated, even before exercise, and their core temperature rises considerably more than adults in response to a given fluid (sweat) loss, which may put them at higher risk for heat-related injury. However, epidemiological data show rates of both heat- and cold-related injuries among children and adolescents as similar or lower than at any other age.

Heat Convection from a Horizontal Cylinder Rotating in a Quiescent Fluid

1986 ◽  
Vol 10 (3) ◽  
pp. 141-152
Author(s):  
H.M. Badr ◽  
S.M. Ahmed
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mathematical Model ◽  
Horizontal Cylinder ◽  
Heat Transfer Process ◽  
Two Dimensional ◽  
Two Dimensional Flow ◽  
Boussinesq Fluid ◽  
The Mathematical Model ◽  
Quiescent Fluid

The aim of this work is a theoretical investigation to the problem of heat transfer from an isothermal horizontal cylinder rotating in a quiescent fluid. The study is based on the solution of the conservation equations of mass, momentum and energy for two-dimensional flow of a Boussinesq fluid. The effects of the parameters which influence the heat transfer process namely the Reynolds number and Grashof number are considered while the Prandtl number is held constant. Streamline and isotherm patterns are obtained from the mathematical model and the results are compared with previous experimental data. A satisfactory agreement was found.

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