The way to reconstruct the heat fluxes by solving the inverse boundary heat exchange problem for the anisotropic stripe

2011 ◽  
Vol 58 (14) ◽  
pp. 1200-1205
Author(s):  
S. A. Kolesnik ◽  
E. L. Kuznetsova
Keyword(s):  
Heat Exchange ◽  
Heat Fluxes ◽  
Inverse Boundary ◽  
The Way

scholarly journals Challenges in Modeling Turbulent Heat Fluxes to Snowpacks in Forest Clearings

2018 ◽  
Vol 19 (10) ◽  
pp. 1599-1616 ◽  
Author(s):  
Jonathan P. Conway ◽  
John W. Pomeroy ◽  
Warren D. Helgason ◽  
Nicholas J. Kinar
Keyword(s):  
Heat Exchange ◽  
Surface Temperature ◽  
Latent Heat ◽  
Turbulent Fluxes ◽  
Heat Fluxes ◽  
Turbulent Heat ◽  
Snow Surface ◽  
Turbulent Heat Exchange ◽  
Uncertainty Estimates ◽  
Model Tuning

Abstract Forest clearings are common features of evergreen forests and produce snowpack accumulation and melt differing from that in adjacent forests and open terrain. This study has investigated the challenges in specifying the turbulent fluxes of sensible and latent heat to snowpacks in forest clearings. The snowpack in two forest clearings in the Canadian Rockies was simulated using a one-dimensional (1D) snowpack model. A trade-off was found between optimizing against measured snow surface temperature or snowmelt when choosing how to specify the turbulent fluxes. Schemes using the Monin–Obukhov similarity theory tended to produce negatively biased surface temperature, while schemes that enhanced turbulent fluxes, to reduce the surface temperature bias, resulted in too much melt. Uncertainty estimates from Monte Carlo experiments showed that no realistic parameter set could successfully remove biases in both surface temperature and melt. A simple scheme that excludes atmospheric stability correction was required to successfully simulate surface temperature under low wind speed conditions. Nonturbulent advective fluxes and/or nonlocal sources of turbulence are thought to account for the maintenance of heat exchange in low-wind conditions. The simulation of snowmelt was improved by allowing enhanced latent heat fluxes during low-wind conditions. Caution is warranted when snowpack models are optimized on surface temperature, as model tuning may compensate for deficiencies in conceptual and numerical models of radiative, conductive, and turbulent heat exchange at the snow surface and within the snowpack. Such model tuning could have large impacts on the melt rate and timing of the snow-free transition in simulations of forest clearings within hydrological and meteorological models.

Research of Smoke Isolating with Air Curtain at Ship’s Tunnel

2012 ◽  
Vol 516-517 ◽  
pp. 111-114
Author(s):  
Xiao Jun Zhu ◽  
Chen Hua Zhong
Keyword(s):  
Heat Exchange ◽  
Flow Field ◽  
Air Curtain ◽  
Heat Control ◽  
The Way

The rapid spreading of poisonous smoke is the main reason which causes death in ship fires. Ships always have long tunnels to traveling passengers or cargos. Because of their longness and straightness, smoke diffuses rapidly. Fire doors are used to stop the smoke from spreading into other parts in vessels. When the fire doors are closed, the way for evacuation is also closed. So it’s important for the professionals to develop a kind of smoke-preventing device which can let people pass by when stopping the smoke. The air curtain is a kind of smoke isolating device which is used to decrease the heat exchange in supermarket or freezer. This paper analyzes flow field, the heat control and the smoke isolating ability of air curtain used in the ships’ long tunnels with different jet angles and initial velocities. At last, a suitable angle is proposed.

scholarly journals HYDRODYNAMICS, DISTRIBUTION OF FLOWS AND THERMAL EFFICIENCY OF COIL HEAT EXCHANGERS IN UNITS OF HEAT-USING APPARATUS OF TUBE FURNACES

2019 ◽  
Vol 62 (4) ◽  
pp. 143-151
Author(s):  
Stanislav P. Sergeev ◽  
Faddey F. Nikiforov ◽  
Sergey V. Afanasiev ◽  
Juliya N. Shevchenko
Keyword(s):  
Heat Exchange ◽  
Turbulent Flow ◽  
Thermal Efficiency ◽  
Heat Exchangers ◽  
Heat Fluxes ◽  
Hydrodynamic Characteristics ◽  
Technological Problem ◽  
Tube Furnaces ◽  
Suction Or Injection ◽  
Coil Heat

The theoretical foundations of construction, mathematical description and engineering calculation of heat exchangers of the serpentine type in blocks of heat-using equipment of tube furnaces and other types of reactors designed for carrying out endothermic reactions (in particular, reforming of natural gas with water vapor) are considered. It is shown that the thermal efficiency of heat exchangers of the coil type is significantly affected by the correct choice of parameters ensuring a uniform distribution of energy flows over the surface of heat-resistant heat exchange tubes. This technological problem is solved by compiling the heat balance and selecting the system of the corresponding equations, which allows to calculate the temperature contour of the coil heat exchanger, its hydrodynamic characteristics and the distribution of mass and heat flows through the heat exchange tubes. The use of the tensor form of the Boussinesq hypothesis is considered, with which the Reynolds equation describing a turbulent flow is transformed to a partial differential equation for a single unknown function and its averaged form is obtained. In relation to the problem under consideration, the correctness of the chosen approach was confirmed both theoretically and experimentally. It is shown that in the core of a turbulent flow with an intense suction or injection, the liquid behaves almost as ideal and the well-known Helmholtz – Friedmann theorem holds with the necessary accuracy. From the aforementioned averaged equation, expressions are obtained that are suitable for describing heat fluxes in channels with suction or injection. According to this theoretical model, thermal calculations of coil-type heat exchangers were carried out, a more accurate assessment of the temperature of the heated medium in each coil tube was made, and the temperature gradient of the external heat carrier over the cross section of the gas duct was found. For the first time in the practice of calculations when choosing the parameters of coils, a number of boundary conditions were taken into account, such as the condition of the coil layout, the necessary heat exchange surface, permissible restrictions on hydraulic resistance, etc.

A New Approach to Solve Inverse Boundary Design of a Radiative Enclosure with Specular-Diffuse Surfaces

2021 ◽  
Author(s):  
Babak Mosavati ◽  
Maziar Mosavati
Keyword(s):  
Heat Flux ◽  
Monte Carlo ◽  
Temperature Distribution ◽  
Monte Carlo Method ◽  
Industrial Applications ◽  
Heat Fluxes ◽  
Uniform Heat Flux ◽  
Uniform Temperature ◽  
Inverse Boundary ◽  
Uniform Temperature Distribution

Abstract The maintenance of uniform temperature distribution affects the efficiency in the most industrial applications. In the current study, a novel strategy has been developed for inverse radiative boundary design problems in radiant enclosures. This study presents the Backward Monte Carlo method to investigate the inverse boundary design of an enclosure composed of specular and diffuse surfaces. A new optimized Monte Carlo method is proposed to determine the temperature distribution of heaters to achieve desirable prescribed uniform heat flux on the design surfaces. The proposed approach is highly efficient and simple to implement with appropriate results. The evaluated heat fluxes on design surfaces and temperature distribution of heaters are compared with the case where the reradiating walls are assumed to be perfectly diffuse. In the proposed approach, for a specific range of specularity, the absorptivity of the reradiating surfaces does not affect the temperature distribution of heaters. Compared to the diffuse walls, the specular walls have more uniform temperature distribution and heat flux of heaters. This finding will provide insight into solar furnaces design to enhance temperature uniformity, making specular surfaces suitable in many industrial applications.

scholarly journals Analogy in the processes of heat exchange of capillary-porous coatings in energy installations

2019 ◽  
Vol 85 ◽  
pp. 05003
Author(s):  
Alexander Genbach ◽  
David Bondartsev ◽  
Iliya Iliev ◽  
Angel Terziev
Keyword(s):  
Heat Exchange ◽  
High Heat ◽  
Heat Fluxes ◽  
Porous Coating ◽  
Heat Conducting ◽  
Porous System ◽  
Experimental Conditions ◽  
Limiting State ◽  
Combined Action ◽  
System Operating

A model of the dynamics of steam bubbles generating on a solid surface in porous structures and a steam-generating wall (substrate) is developed. The model is based on the filming and photography with speed camera SKS-1M. The removal of high heat fluxes (up to 2х106 W/m2) is provided by the combined action of capillary and mass forces with application of intensifiers. An analytical model is developed based on the theory of thermoelasticity. The limiting state of a poorly heat-conducting porous coating and a metal substrate has been determined. The heat fluxes were calculated from the time of spontaneous appearance of the steam nucleation (10-8) up to the time of material destruction (102 ÷ 103 s). The destruction of the coating under the action of compression forces occurs in much earlier time than the tension forces. The intervals of the heat flux within which such destruction occurs are different for the quartz coating qmax ≈ 7х107 W/m2, qmin ≈ 8х104 W/m2 and for granite coating qmax ≈ 1х107 W/m2, qmin ≈ 21х104 W/m2. Experimental units, experimental conditions, the results of the heat exchange crisis and the limiting state of the surface are presented, and critical heat fluxes are calculated. The investigated capillary-porous system, operating under the combined action of capillary and mass forces, has the advantage over pool boiling, thin-film evaporators and heat pipes.

Studies of heat regulation in the sheep, with special reference to the Merino

1950 ◽  
Vol 1 (2) ◽  
pp. 200 ◽  
Author(s):  
DHK Lee
Keyword(s):  
Heat Exchange ◽  
Special Reference ◽  
Heat Balance ◽  
Present Knowledge ◽  
Thermal Physiology ◽  
Animal Body ◽  
Animal Economy ◽  
The Way

This paper is a tentative application to a particular animal, the sheep, of concepts concerning heat regulation in "warm-blooded" animals, built up over ten years of laboratory, field, and library inquiry. The heat exchange between the animal and its environment is first analysed in a quantitative, physical fashion, and the deficiencies in present knowledge are pointed out. The ways in which the animal body attempts to maintain a heat balance are next considered, and the secondary consequences of these processes to the animal economy indicated. The paper concludes with a brief consideration of the comparative aspects. It is essentially a formulation of the way in which the thermal physiology of any animal should be considered, using the sheep as a convenient example. Many of the data are drawn from work carried out under the author's direction.

scholarly journals Annual Observations of Climatic Impacts in the Songhua River Basin, China

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Xiaocheng Song ◽  
Liu Jing
Keyword(s):  
Heat Flux ◽  
Heat Exchange ◽  
Stochastic Model ◽  
Heat Fluxes ◽  
Sensible Heat ◽  
Songhua River ◽  
Songhua River Basin ◽  
The Relationship ◽  
The Songhua River Basin ◽  
The Songhua River

Heat fluxes have been recognized as determinant regarding the river effect on microclimate. The relationship between rivers and the atmosphere is particularly significant for heat fluxes and varies with the meteorology and hydrology. In this study, based on annual observation data from the Songhua River Basin (Harbin, China), a regression and a stochastic model were used to analyze the relationship of the atmosphere-river daily maximum temperatures and evaluate the heat fluxes. The root mean square error (RMSE) of the river temperature was 2.21°C with the regression method, improving to 0.83°C with the stochastic model. The net shortwave radiation flux was the dominant heat gain component, while the latent heat flux accounted for the main heat loss. The sensible heat flux represented the smallest contribution. The river thermal effect in summer mainly resulted from the latent heat exchange, while the effect of the sensible heat exchange tended to be stronger in spring and autumn.

scholarly journals How Life Works—A Continuous Seebeck-Peltier Transition in Cell Membrane?

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 960 ◽  
Author(s):  
Umberto Lucia ◽  
Giulia Grisolia
Keyword(s):  
Heat Exchange ◽  
Cell Membrane ◽  
Thermophysical Properties ◽  
Electric Potential ◽  
Heat Fluxes ◽  
Thermodynamic Approach ◽  
Equilibrium Thermodynamic ◽  
Cell Systems ◽  
Phenomenological Coefficients

This paper develops a non-equilibrium thermodynamic approach to life, with particular regards to the membrane role. The Onsager phenomenological coefficients are introduced in order to point out the thermophysical properties of the cell systems. The fundamental role of the cell membrane electric potential is highlighted, in relation to ions and heat fluxes, pointing out the strictly relation between heat exchange and the membrane electric potential. A Seebeck-like and Peltier-like effects emerge in order to simplify the description of the heat and the ions fluxes. Life is described as a continuos transition between the Peltier-like effect to the Seebeck-like one, and viceversa.

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