Top PDF UTCI-Fiala multi-node model of human heat transfer and temperature regulation.

UTCI-Fiala multi-node model of human heat transfer and temperature regulation.

UTCI-Fiala multi-node model of human heat transfer and temperature regulation.

multi-node model(s) of human thermoregulation. Mathematical modelling of human thermal regulation and comfort goes back some 70 years. Following diverse general human heat balance considerations (e.g. Burton 1937, Aschoff and Wever 1958, Fanger 1973) various two-node models of human thermoregulation emerged (e.g. Azer and Hsu 1977, Gagge et al. 1986). In the past forty years, also more complex, multi- segmental models (e.g. Stolwijk 1971, Wissler 1985, Huizenga et al. 2001, Tanabe et al. 2002, Fiala et al. 1999 - 2003) have been developed. Compared to two-node models, multi-segmental (here: multi-node) models simulate the human body in greater detail predicting both overall and local physiological responses. Human environmental heat losses are calculated taking into account characteristic inhomogeneities such as non-uniform skin temperatures, regulatory responses, clothing properties or environmental conditions. Heat dissipation within the body is predicted by explicit simulation of the individual human heat transfer components (including blood circulation) using thermal and physiological properties of the main tissue types and taking into consideration the specific role of extremities in human thermoregulation.
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UTCI-Fiala multi-node model of human heat transfer and temperature regulation

UTCI-Fiala multi-node model of human heat transfer and temperature regulation

multi-node model(s) of human thermoregulation. Mathematical modelling of human thermal regulation and comfort goes back some 70 years. Following diverse general human heat balance considerations (e.g. Burton 1937, Aschoff and Wever 1958, Fanger 1973) various two-node models of human thermoregulation emerged (e.g. Azer and Hsu 1977, Gagge et al. 1986). In the past forty years, also more complex, multi- segmental models (e.g. Stolwijk 1971, Wissler 1985, Huizenga et al. 2001, Tanabe et al. 2002, Fiala et al. 1999 - 2003) have been developed. Compared to two-node models, multi-segmental (here: multi-node) models simulate the human body in greater detail predicting both overall and local physiological responses. Human environmental heat losses are calculated taking into account characteristic inhomogeneities such as non-uniform skin temperatures, regulatory responses, clothing properties or environmental conditions. Heat dissipation within the body is predicted by explicit simulation of the individual human heat transfer components (including blood circulation) using thermal and physiological properties of the main tissue types and taking into consideration the specific role of extremities in human thermoregulation.
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Validation of the Fiala multi-node thermophysiological model for UTCI application

Validation of the Fiala multi-node thermophysiological model for UTCI application

and more detailed physiological observation databases for the purposes of model validation. One of the most recent models, which was made available to the COST Action 730 1 was the multi-node thermophysiological model of Fiala (Fiala et al. 1999, 2001, 2003, 2010). A special version of Fiala’s multi-node model was set up for COST Action 730 and hereafter referred to as the UTCI-Fiala model. Following the intention of UTCI to provide a direction-independent assessment tool, the passive (heat transfer) system of the UTCI-Fiala model was configured as a symmetric model with identical physiological responses on the left and right extremities and spatial body sectors, thereby enabling a reduction of the number of body elements to twelve comprising 187 tissue nodes in total (compared to 342 nodes of the original model). Secondly, the short wave radiation absorbed at the surface of each anatomic element was calculated using local projected area factors for unknown body orientation derived from work of Kubaha et al. (2004). Further adjustments and extensions of the original model are described by Fiala et al. (2011) in this special issue.
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Heat transfer over a nonlinearly stretching sheet with non-uniform heat source and variable wall temperature

Heat transfer over a nonlinearly stretching sheet with non-uniform heat source and variable wall temperature

Later, Erickson et al. [3] extended the work of Sakiadis [2] to account for mass transfer at the stretched surface. The two dimensional boundary layer flow caused by a linear stretching sheet in an otherwise quiescent fluid was first discussed by Crane [4]. He obtained a closed form exponential solution. Singh [5] studied the effect of non-uniform heat source on hydromagnetic convective flow of a viscoelastic fluid. Grubka and Bobba [6] studied the heat transfer characteristics of a continuous stretching surface with variable temperature. Abel and Nandeppanavar [7–9] studied the effect of non-uniform heat source on viscoelastic boundary layer flows. Further, Abel et al. [10] investigated the effects of viscous dissipation and non-uniform heat source. Abel and Mahesha [11] studied the effects of non-uniform heat source with variable thermal conductivity. Ali [12] investigated the effects of power law index on heat transfer characteristics of a power law fluid flow. Tsai et al. [13] investigated the effects of non-uniform heat source on unsteady stretching sheet.
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A lattice Boltzmann model for heat transfer in heterogeneous media

A lattice Boltzmann model for heat transfer in heterogeneous media

should be very small and (2) the specific heat capacity and thermal conduc- tivity of working fluid should be constant. Unfortunately, in many industrial applications (e.g. combustion), these two assumptions can hardly be met. Re- cently, some scholars discussed how to model conjugate heat transfer by the LB method [17–22]. For conjugate heat transfer, the investigated domain is consisted of several different medium layers, and the specific heat capacity and/or thermal conductivity of the medium layers may be different with each other. However, their LB approaches can not treat spatially consecutive varia- tion of thermophysical properties within any medium layer as in their models the thermophysical properties of each medium layer must to be spatially iden- tical. On the other words, these LB models for conjugate heat transfer aim to handle interfaces between heterogeneous medium layers rather than to model variable thermophysical properties of working media.
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A lattice Boltzmann model for heat transfer in porous media

A lattice Boltzmann model for heat transfer in porous media

Porous media are commonly found not only in the nature but also in industries. Furthermore, porous media is an important research prototype for a diversity of dis- ciplines. So far a REV (representative elementary volume) scale lattice Boltzmann (LB) model has been proposed and popularly used for investigation on heat transfer in porous media. Unfortunately, such model suffers from a serious drawback that it can not address an investigated domain where the heat capacitance (the product of density and specific heat capacity) of porous media varies spatially obviously. Such deficit restricts dramatically its applicable range. The purpose of the present work is to remedy such serious shortcoming in a simple way. Numerical validation demonstrates the capability and reliability of the present model. In order to clearly show the advantage of the present model, here a single-relaxation-time LB model is taken as an example to illustrate how to remedy the shortcoming of previous mod- els. Its multiple-relaxation-time counterpart can be established straightforwardly in the same way.
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Regulation of brain temperature in winter acclimatized reindeer under heat stress

Regulation of brain temperature in winter acclimatized reindeer under heat stress

When ungulates are under heat stress, it has been assumed that cold venous outflow from the nasal mucosa is drained either directly to the heart for general body cooling or by way of the angular oculi vein (AOV) to a cavernous venous sinus located just below the brain (Figs1 and 2). Here, heat is exchanged with the arterial blood in a rete on its way to the brain for selective brain cooling (SBC) (Baker and Hayward, 1968). The reindeer (Rangifer tarandus) is an Arctic animal that has adapted to annual changes of 80°C in ambient temperature by growing a fur of excellent insulation value in the autumn to be shed in the following spring. That together with a reduction of surface temperature caused by vascular changes (Johnsen et al., 1985b) and an efficient nasal heat exchange mechanism (Blix and Johnsen, 1983) result in a 30°C reduction in lower critical temperature from summer to winter (Nilssen et al., 1984a). The animal, so equipped to withstand cold, consequently has few avenues of heat loss in winter and runs the risk of hyperthermia during exercise when metabolic heat production rises rapidly with running speed (Nilssen et al., 1984b) and softness of the surface over which the animal travels (Fancy and White, 1985). We have observed that moderately heat-stressed reindeer pant, first with the mouth closed, but, under severe heat stress, they resort to open-mouth panting (OMP) to dissipate heat from their big and richly vascularized tongue. In a previous study, we (Aas-Hansen et al., 2000) found, however, that the flow of air through the nose is reduced from 100 to only 2% of the respiratory minute volume when the animal resorts to OMP. That would seem to imply that SBC might be compromised when it is most needed.
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A Cell Model to Describe and Optimize Heat and Mass Transfer in Contact Heat Exchangers

A Cell Model to Describe and Optimize Heat and Mass Transfer in Contact Heat Exchangers

The scheme of the process is shown in Figure 1. The operating volume is filled with a packing (for instance, with Rashig rings). The cold water is supplied at the top of the apparatus and flows down as a thin film over the packing surface that is rather high due to the shape of its elements. The hot gas is fed at the bottom of the appara- tus and flows up to the top interacting with the water flow. Let us separate in the volume two parallel vertical channels: one for the water flow and another one for the gas flow. The channels can be presented as two one-di- mensional chains of cells of the length Δx. The number of cells in each chain is m = H/Δx, and the serial number of the cell i is the integer argument of its spatial position. The thermophysical state of the flows can be presented by column vectors. For example, the vectors of heat, temperature and mass for the water chain have the form Q w = {Q wi }, t w = {t wi }, m w = {m wi }, etc, where i = 1, 2,  ,
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A Mathematical Model to Solve Bio Heat Transfer Problems through a Bio Heat Transfer Equation with Quadratic Temperature Dependent Blood Perfusion under a Constant Spatial Heating on Skin Surface

A Mathematical Model to Solve Bio Heat Transfer Problems through a Bio Heat Transfer Equation with Quadratic Temperature Dependent Blood Perfusion under a Constant Spatial Heating on Skin Surface

Using the extended mapping method with symbolic computation, we found exact analytical solution of the BHT equation with temperature-dependent blood perfusion, that describes the nonuniform temperature distribution in biological tissues. Using this solution, we have explicitly investigated temperature distribution in living tissues. The effects of the surrounding medium and the effects of the temperature-dependent blood perfusion on tem- perature distribution are also addressed. The exact solutions found in this work can be used to predicate the evolution of the detailed temperature within the tissues during thermal therapy.
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Study Of Cause Of Rise In Temperature Of Earth And Effect Of Temperature (Heat) On Human Body

Study Of Cause Of Rise In Temperature Of Earth And Effect Of Temperature (Heat) On Human Body

summers at many places on the planet lead to change in biodiversity. With more heat waves on the horizon and a big one currently sweeping much of the areas the risk of heat-related health problems has also been on the rise. Heat exhaustion is a relatively common reaction to severe heat and can include symptoms such as dizziness, headache and fainting. It can usually be treated with rest, a cool environment and hydration (including refueling of electrolytes, which are necessary for muscle and other body functions). Heat stroke is more severe and requires medical attention it is often accompanied by dry skin, a body temperature above 103 degrees Fahrenheit,
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The Effects Of Inlet Temperature On Heat Transfer Behaviours Of Evaporation In Rectangular Microchannels

The Effects Of Inlet Temperature On Heat Transfer Behaviours Of Evaporation In Rectangular Microchannels

the best performances. In this study, the inlet temperature of 40 0 C is the best choice for designing of microchannel heat sinks and the total heat flux is about 57.74 W/cm 2 . Besides, the steam output temperature increases with increasing of inlet water temperature in both numerical simulation and experimental data. The exit vapour quality also increases with increasing of inlet temperature in numerical simulation; however, the values of increments in all of cases are very small. In addition, the effect of mass flow rate to the time of occurring nucleation site and full evaporation was also investigated. The results obtained from numerical simulation were in good agreement with experimental data, with percentage errors were less than 2 %.
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FEM Approach for Transient Heat Transfer in Human Eye

FEM Approach for Transient Heat Transfer in Human Eye

All the previously developed models have neglected the effects of blood perfusion and metabolism on ret- ina/iris/cilliary body. The significance of blood perfusion and metabolism on the temperature distribution in the eye is debatable, since they take place only on retina, choroid, iris and cilliary body, which constitute very small part of human eye. The blood flow in the iris/sclera part plays significant role to adjust eye temperature with the rest of the body [3]. In [8] it is clearly mentioned that “Due to lack of literature data, the perfusion term is ne- glected. The effect of this assumption on the accuracy of the model however remaining unknown”. The retina has perhaps the highest oxygen consumption rate (metabo- lism) of any tissue in the body [12]. Hence it is necessary to investigate the effects of blood perfusion and metabo- lism in order to obtain a more accurate result. The objec- tive of this paper is to determine the transient tempera- ture distribution in human eye. Hence, this model pro- vides the results for transient temperature distribution including the effect of blood perfusion and metabo- lism.
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Heat Transfer

Heat Transfer

It is impossible to construct an engine that will work in a complete cycle and produce no other effect except the raising of a weight and the cooling of a reservoir. The second law says that if you draw heat from a reservoir to raise a weight, lowering the weight will not generate enough heat to return the reservoir to its original temperature, and eventually the cycle will stop. If two blocks of metal at different temperatures are thermally insulated from their surroundings and are brought into contact with each other the heat will flow from the hotter to the colder. Eventually the two blocks will reach the same temperature, and heat transfer will cease. Energy has not been lost, but instead some energy has been transferred from one block to another.
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Heat Transfer

Heat Transfer

B) FORCED – CONVECTION: - If a fluid is forced to move to take up heat from a hot body then the convection process is called forced convection In this case Newton’s law of cooling bolds good. According to which rate of loss of heat from a hot body due to moving fluid is directly proportional to the surface area of body and excess temperature of body over its surroundings

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Numerical simulation heat transfer by natural convection in liquid metal with a sinusoidal temperature

Numerical simulation heat transfer by natural convection in liquid metal with a sinusoidal temperature

For comparison, the structure of the flow and isotherms for the air (Figure 3) are different from the liquid metal. As noted, the presence of two counter- rotating cells to Ra = 10 3 and 10 5 and a single vortex to Ra = 10 4 and 10 6 , it is also noted that the intensity of the flow increases by increasing Ra. Heat transfer by convection is triggered from as Ra = 10 4 . Thus, there is a symmetry of the isotherms for Ra = 10 5 and the transfer becomes fully convective for Ra = 10 6 . Note that the effect found on the stream lines, affects the structure of the isotherms, This changing of the flow structure explained by the density of air is lighter than the liquid metal.
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Adiabatic wall temperature and heat transfer coefficient influenced by separated supersonic flow

Adiabatic wall temperature and heat transfer coefficient influenced by separated supersonic flow

For flow around simple bodies (plane surfaces, cylinders, cones) adiabatic wall temperature is defined with the use of theoretical meaning for recovery factor as a function of Prandlt number. However, when the flow with a boundary layer separation is considered (behind ribs, dimples, holes) then it is difficult to define adiabatic wall temperature and it is often changed for the flow stagnation temperature. Such approach results in high errors in defining heat transfer coefficient – up to 50%. The goal of this research was applying of an unsteady state methodology for adiabatic wall temperature acquisition in aerodynamic experiment together with heat transfer coefficient definition.
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Static Conversion of a Salinity Difference into a Temperature Difference: A Heat and Mass Transfer Investigation

Static Conversion of a Salinity Difference into a Temperature Difference: A Heat and Mass Transfer Investigation

We investigate heat and mass transport phenomena occurring in a fully static (i.e. with no moving mechanical parts) cooling device, which has been experimentally tested and interpreted by a simplified one-dimensional theoretical model. The realized lab-scale prototype operates at ambient pressure and consists of several identical stages, which are designed to generate a cooling capacity inducing multiple evaporation/condensation processes. Such processes are driven by a salinity difference between two water solutions, which can be separated for instance by a hydrophobic membrane [1–3]. Here, we present both the preliminary experimental results and predictions by the numerical model. The latter is only intended to reasonably extrapolate the expected behavior of the device under a wider range of operating conditions. More specifically, we estimate the cooling performance at different salinity values of the solutions, thermal loads, number of stages, and other relevant geometrical quantities of our design. It is interesting noticing that, in the proposed set-up, the constant salinity difference needed for sustaining the cooling load may be possibly maintained using passive solar regeneration as discussed by the Authors of this work in a previous study [4], thus paving the way to a static cooling cycle driven by solar power.
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The WTO as a Node of Global Governance: Economic Regulation and Human Rights Discourses

The WTO as a Node of Global Governance: Economic Regulation and Human Rights Discourses

Three perspectives may be discerned on the relationship between human rights norms and economic liberalisation. For some there is a fundamental conflict: `neoliberal globalisation is incompatible with the globalisation of human rights’ (George 1999, 15). Others consider that human rights, understood as liberal rights protecting both economic and political freedom of individuals, would complement and even reinforce the WTO’s free trade mission, as shown above in the discussion of constitutionalisation. A middle view argues that although the two have developed in isolation, they have much in common and are converging: human rights are not confined to restricting the state but also prescribe positive state action, but equally trade regulation cannot aim only at negative integration but must provide a basis to balance the costs of liberalisation and make them socially acceptable; hence, it could be helpful to develop debate between the two perspectives (Cottier 2002). This section will explore these viewpoints in relation to a couple of specific examples.
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Estimating uncertainty of temperature measurements for studies of flow boiling heat transfer in minichannels

Estimating uncertainty of temperature measurements for studies of flow boiling heat transfer in minichannels

Abstract. This paper presents the method of estimating the uncertainty of temperature measurements conducted using K-type thermocouples in the study of flow boiling heat transfer in minichannels. During heat transfer experiments, the fluid temperature at the inlet and outlet of the minichannel is measured with thermocouples connected to a DaqLab 2005 data acquisition station. The major part of the experimental setup for calibration of temperature measurement included a calibrator of thermocouples. The thermocouples were manufactured by Czaki Thermo-Product, Poland. The temperatures recorded with the thermocouples were compared statistically while measuring the temperature of demineralised water at several characteristic points at liquid phase change or using the reference temperature known from the calibrator. The experimental error of the temperature measurement method was determined according to the principles of statistical analysis. Estimates of the mean value and the experimental standard deviation of the experimental error as well as the confidence interval for a single experimental error and the measurement accuracy were presented. The uncertainty of the difference in temperature was also calculated.
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Universal thermal climate index (UTCI) applied to determine thresholds for temperature-related mortality

Universal thermal climate index (UTCI) applied to determine thresholds for temperature-related mortality

tures. Hence, it is advisable to apply specific models of mortality in such studies; for exam- ple, those that take into account an ordinal number of a day since a wave has started. In particular, it was shown that in Arkhangelsk ordinary temperature was more closely related to mortality during heat waves than effective one. In the present work we, for the first time in Russia, have examined a possibility to apply a bioclimatic index UTCI as a marker of a tem- perature-induced stress and also used standard statistical numerical procedures to test a hy- pothesis that has been often stated in multiple research, namely, that high nighttime tempera- ture might exert greater influence than daytime one during hot season due to people being un- able to get their usual night rest from heat.
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