Conductive heat flow

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Conductive heat flow pattern of the central-northern Apennines, Italy

Conductive heat flow pattern of the central-northern Apennines, Italy

In this paper, we review the available thermal database from Pasquale et al. (2010) and analyze new available information deriving from deep temperature records, in the 1000-7000 m depth range, carried out in oil and conventional geothermal wells. We focus on the deepest temperature data similarly to what suggested by Della Vedova et al. (2001) as they may better reflect the undisturbed conductive thermal regime of the lithosphere. However, since most of available deep temperatures were measured in the permeable carbonate Paleogene-Mesozoic layers, the influence of the regional groundwater circulation on the thermal regime is investigated. To treat thermal data recorded from deep wells we use a new approach as recently suggested by Pasquale et al. (2012 and 2014). This approach consists in rigorously selecting thermal data, i.e. rejection of boreholes with less than two temperature records at different depths and treating thermal disturbances due to drilling with a technique specifically calibrated for the Apennines foreland basins (Pasquale et al., 2008). A further improvement in data processing consists in estimating thermal conductivity by taking into account porosity and anisotropy variations with depth due to the overburden of the sediment and temperature effect. Moreover, the radiogenic heat from both natural gamma-ray logs and gamma-ray spectrometry measurements on core samples is evaluated. Both the revised and the new heat-flow data provide a new preliminary pattern of the terrestrial heat flow.
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High Pressure- Temperature Electrical Resistivity Experiments on Fe-Si Alloys Bearing on Conductive Heat Flow at the Top of the Outer Core

High Pressure- Temperature Electrical Resistivity Experiments on Fe-Si Alloys Bearing on Conductive Heat Flow at the Top of the Outer Core

likely to have the same amount of chemical contamination because of the same number of Fe disk shielding, with I22 having the largest G-factor among all and the highest value of resistivity as well. With I22 and I23 likely having similar degrees of contamination, G- factor can clearly explain the higher electrical resistivity of I22 compared to I23 because of its higher G-factor value. Therefore, even with a low heating rate which can make the sample vulnerable to the chemical reaction with the electrode leads, I23 exhibits acceptable electrical resistivity values. One can conclude that, the relative length and diameter of the sample compared to the rest of conductive part of the electrical circuit inside and outside of the cell is of critical importance for a cell with pure Fe sample and Pt electrode. This fact urges a measuring method that can reduce or completely rule out the effect of electrode contribution to the resistivity measurements as much as possible.
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Coupled hydro-thermal analysis of underground coal gasification reactor cool down for subsequent CO2 storage

Coupled hydro-thermal analysis of underground coal gasification reactor cool down for subsequent CO2 storage

depth) [15]. An analytical convective heat transport model has been implemented to calculate the convective heat flux being used as input for a two dimensional numerical conductive heat flow model to simulate the UCG reactor cool down process with (forced cool down) and without water flushing (natural cool down). The model developed represents the cross section of a synthetic UCG site located at 1,000 m depth. Material properties for rock and coal have been obtained from literature. Both, the natural and the forced cool down process have been studied by a coupled analytical and numerical analysis. From the result analysis it was found that:
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Analysis of Thermal Conduction in the Machine Border Collapse: Numerical and Experimental Comparison

Analysis of Thermal Conduction in the Machine Border Collapse: Numerical and Experimental Comparison

The success of a design of a machine manufacturing line is directly related to the efficiency in the use of raw material and components, requiring a total control of the process. In this work the numerical simulation was applied to analyze the conduction of heat transferred in the Edge gluing machine Smc1 and to validate the simulations with the temperature differences collected ex- perimentally. These validations were performed with the collection of tem- peratures via thermal imaging, which provides greater accuracy of thermal conduction capture. The results obtained are similar in relation to certain points captured by thermal imaging. The thermal model analyzed represents proximity to the heat distribution during the use of the machine.
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Hot limpets: predicting body temperature in a conductance mediated thermal system

Hot limpets: predicting body temperature in a conductance mediated thermal system

For each experiment, the recorded meteorological data and the known physical characteristics of each test object and the rock were used in the heat-budget model to predict the time course of body temperature. These temperatures could then be compared to actual, recorded body temperatures. As noted above, for experiments with the cone and the silver-bodied limpet, data for the first 3 days of the experiment were used to allow the model to relax into independence from its starting conditions, and the last 5 days were used to compare the model to the measured cone temperatures. It was not possible to leave the live limpets exposed for longer than a day, so an alternative Table·2. Symbols used in the text and the equation in which
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Theoretical Rationale of Heating Block for Testing Bench of Aerospace Crafts Thermal Protection Elements

Theoretical Rationale of Heating Block for Testing Bench of Aerospace Crafts Thermal Protection Elements

Abstract. The theoretical rationale for the structural layout of a testing bench with zirconium dioxide heating elements on the basis of modelling radiative-conductive heat transfer are presented. The numerical simulation of radiative-conductive heat transfer for the two-dimensional scaled model of the testing segment with the finite-element analysis software package Ansys 15.0 are performed. The simulation results showed that for the selected layout of the heaters the temperature non-uniformity along the length of the sample over time will not exceed 3 % even at a temperature of 2000 K.
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ANALYSIS OF COMBINED CONDUCTION AND RADIATION HEAT TRANSFER IN A RECTANGULAR FURNACE INCLUDING TWO FLAMES

ANALYSIS OF COMBINED CONDUCTION AND RADIATION HEAT TRANSFER IN A RECTANGULAR FURNACE INCLUDING TWO FLAMES

influencing parameters, such as radiation- conduction parameter (RC) on thermal behavior of the system. As a main result, it was found that the rise in the value of RC and emissivity and decrease in optical thickness and scattering albedo increase the rate of radiative transfer. Varady and Fedorov [4] studied the conduction-radiation heat transfer in a semitransparent glass foam layer. It was assumed that the foam layer is thin with uniform thickness, which is bounded by hot combustion gases on top and glass melt on bottom. They used Schuster-Schwarzchild approximation for solving the radiative transfer equation and presented a method to obtain the effective thermal conductivity of the foam layer. Regarding the combustion process in furnaces, some results are presented in literature. Modeling and simulation of an industrial furnace under the conventional combustion as well as under the highly preheated and diluted air combustion (HPDAC) conditions was done by Hamidi and Rahimi [5].
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Streamwise curvature effects on turbulent wall jet heat transfer.

Streamwise curvature effects on turbulent wall jet heat transfer.

showed that large differences occurred in the regions approaching separation. Giles, Hays and Sawyer (Ref.11) studied turbulent jet flow on logarithmic spiral surfaces. They found that similarity of the velocity profiles existed everywhere along the jet and that the rate of jet growth was much higher than for jets along circular cylinders at corresponding downstream distances. Sridhar and Tu (Ref.12) in their study of curvature effects on turbulent wall jets concluded that the inner layer velocity profile was

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Thermal Properties of Organic Foods

Thermal Properties of Organic Foods

The glass transition was determined with TA Universal Analysis 2000 version 4.5A software (TA instruments, USA). The glass transition was characterized with the following parameters of the endothermic baseline shift: the onset (Tgo), end (Tge) and inflection (Tgi) points. The onset and end points were measured by an extrapolation of the baselines to the intersection with the glass transition line. Because the glass transition was detected by the heating of the sample, the end point refers to a higher temperature then than the onset point. The inflection point shows the inflection of the glass transition curve, and was found as illustrated in Figure 4. This point should not be confused with the midpoint of the glass transition, which is measured as a middle point on the virtual glass transition line between the onset and end point of the glass transition. Also, the inflection point is characterized by a negative peak of the derived heat flow curve.
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Design and Testing of a Modified Hydroponic Shipping Container System for Urban Food Production

Design and Testing of a Modified Hydroponic Shipping Container System for Urban Food Production

Since active thermal control accounted for nearly 80% of the total energy requirement throughout the design year, it was most important factor for improvement in the MHSC opera- tional design. Structural conduction and ventilation convec- tion contributed the largest heating and cooling loads in the model. Reducing the heat transfer associated with these components increased the thermal efficiency of the modeled MHSC, thereby allowing the system to maintain optimal plant growth temperatures with less energy dedicated to thermal control. Demonstrating the effects of these principles, three alternative design and operational scenarios were considered: 1) Follow common practice for inhabited structures and improve the insulation value of the MHSC by replacing the 2” extruded polystyrene (XPS) rigid foam board with 2” of closed cell spray polyurethane foam (SPF) on all surfaces and increasing the R eff for the unit from 5.00 to 6.25 [33];
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Effect of Cascading the Thermoelectric Peltier Cooler on COP and Cooling Load

Effect of Cascading the Thermoelectric Peltier Cooler on COP and Cooling Load

Yamanashi [14] applied heat balance equations in analyzing the coefficient of performance of thermoelectric cooling system by addition of heat exchangers at both side of the device. The balancing equations follow non-equilibrium thermodynamics. For optimizing the two-stage thermoelectric coolers, two different configurations were presented. These configurations are cuboidal pyramidal shaped modules. These arrangements were studied by using COP as an optimization criterion. In the case of the pyramidal shaped module, number of thermocouples between two stages is in ratio of 2.5-3 with lower stage having more modules. The current flowing in the module also follows the same ratio. In the case of cuboidal type module both first and second stage has same number of thermocouples.
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Magneto Hydrodynamic Free Convection Heat and Mass Transfer Flow of a Viscous, Conductive Fluid over an Inclined Stretching Sheet with Viscous Dissipation and Constant Heat Flux Using Homotophy Perturbation Method

Magneto Hydrodynamic Free Convection Heat and Mass Transfer Flow of a Viscous, Conductive Fluid over an Inclined Stretching Sheet with Viscous Dissipation and Constant Heat Flux Using Homotophy Perturbation Method

Abstract - The present research article is to investigate the magnetohydrodynamic (MHD) free convective heat and mass transfer flow of viscous incompressible electrically conductive fluid over an inclined stretching sheet with viscous dissipation and constant heat flux with the help of homotophy perturbation technique. This paper gives the description of the effect of flow parameters on velocity, temperature and concentration, which is graphically represented in figures.

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Heat flow modeling in copiers

Heat flow modeling in copiers

A way to look at the system is to divide the intermediate in elements that successively encounter different boundary conditions. Imagine sitting on top of the intermediate and following the contour of the intermediate, moving through the system. Boundary conditions are dependent on the configuration of the copier, but known. In the general case, the intermediate will consecutively be heated, fused, cleaned and reprinted by a number of drums. When assumed that the system after some time will get in stationary situation and the heat flow in longitudinal direction due to conduction is negligible compared to the heat flow imposed by the mechanical movement of the intermediate, it is sufficient to describe only one element with variable length and varying boundary conditions. The simulation will continue until the set of differential equations, given the boundary conditions and initial values, reaches the stationary solution. Figure 2 illustrates the basic concept behind this approach. For example Matlab is a tool that is perfectly suitable to support this way of modeling. A model using this concept is currently available at Océ and serves as a starting point for the generation of the dynamic models introduced in this paper.
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NUMERICAL PREDICTIONS ON FLOW AND HEAT TRANSFER IN HEAT EXCHANGER TUBE EQUIPPED WITH VARIOUS FLOW ATTACK ANGLES OF INCLINED-WAVY SURFACE

NUMERICAL PREDICTIONS ON FLOW AND HEAT TRANSFER IN HEAT EXCHANGER TUBE EQUIPPED WITH VARIOUS FLOW ATTACK ANGLES OF INCLINED-WAVY SURFACE

Sawhney et al. (2017) experimentally investigated the pressure loss, heat transfer configuration and thermal performance in a solar air heater with wavy delta winglet. The number of wave (3, 5 and 7), Reynolds number (4000 – 17,300), arrangement (inline and staggered) and relative longitudinal pitch (3, 4, 5 and 6) were varied. They reported that the maximum Nusselt number is around 223% over the flat plate with the friction loss around 10.3 times above the base case. They also stated that the optimum thermo-hydraulic performance is found to be around 2.09. Li et al. (2016) numerically reported the laminar flow and heat transfer in a microchannel heat sink with triangular cavities and rectangular ribs for Re = 173 - 635. The influences of relative rib width and relative cavity width on the flow structure and performance were investigated. Shirvan et al. (2017) summarized the effects of wavy surface on natural convection heat transfer in a cosine corrugated square cavity filled with nanofluid. Xu et al. (2015) experimentally investigated on thermal performance enhancement in a wavy finned flat tube heat exchanger for the Reynolds number in the range 1340 – 13,476. They stated that the Nusselt numbers of discontinuous type, staggered type and vortex-generator type are increased by 11.29%, 28.61% and 56.46% on average, and the friction factors are increased by 3.23%, 66.26% and 48.58% on average, respectively. Xiao et al. (2017) studied the augmentations on heat transfer and performance in a wavy finned flat tube by water spray cooling for Re = 210 - 680. They claimed that the Nusselt numbers of three water flow rates are increased by 48 - 68% on average when compared to the case without spray. Du et al. (2014) performed the investigations on heat transfer augmentation in a wavy finned flat tube with punched longitudinal vortex generators. The flow attack angle of the delta winglet vortex generators was considered. They claimed that the optimum performance evaluation
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A BASIC REVIEW ON TRIPLE CONCENTRIC TUBE HEAT EXCHANGER

A BASIC REVIEW ON TRIPLE CONCENTRIC TUBE HEAT EXCHANGER

in graphical form of temperatures along with the length of heat exchanger for all flow arrangements which are mentioned above. They concluded that both the experimental and numerical results are close enough. [9] Cristian Patrascioiu and Sinziana Radulescu developed a numerical model using equations of heat transfer and fluid dynamics for laminar flow in triple concentric tube heat exchanger for prediction of outlet temperature. [10] They have used mineral oil as hot fluid in inner annulus and water as coolant in inner tube and outer annulus. Average deviation ranging in the domain 3.5 to 4.8 % for temperature prediction. [11]
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Investigation of boiling heat transfer and flow regimes in a heat exchanger

Investigation of boiling heat transfer and flow regimes in a heat exchanger

Abstract. Experimental and numerical simulation of heat transfer and flow regimes for vertical flow across horizontal tubes are presented for mass flow rate in the range 0.03 – 0.17 kg/s and heat fluxes in the range 1.07–1.35 kW/m 2 . The tubes had a diameter of 9.75 mm and a pitch to diameter ratio of 1.85. The CFX version 14.0 from ANSYS was used to predict the flow regimes and the temperature distribution in the tube bundles. These data and the predictions from numerical simulation were compared with the data available in the literature. It is found that the circulation zone in the shell becomes bigger as the mass flow rate is increases. The flow patterns identified in this experiment are bubbly, intermittent and annular flow. These data agrees well with the published data.
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Review on Comparative Study between Straight Tube Heat Exchanger and Helical Coil Heat Exchanger

Review on Comparative Study between Straight Tube Heat Exchanger and Helical Coil Heat Exchanger

Abstract: The main purpose of this study is to determine the relative advantage of using a helically coiled heat exchanger over a straight tube heat exchanger. It is found that the heat transfer in helical circular tubes is higher as compared to Straight tube due to their geometrical shape. Helical coils offer advantages over straight tubes due to their compactness and increased heat transfer coefficient. The increased heat transfer coefficients are a consequence of the curvature of the coil, which induces centrifugal forces to act on the moving fluid, resulting in the development of secondary flow. The curvature of the coil governs the centrifugal force while the pitch (or helix angle) influences the torsion to which the fluid is subjected to. The difference in velocity sets-in secondary flows. The fluid particles flowing at the core of the pipe have higher velocities than those flowing near to the pipe wall. Thus the fluid particles flowing close to the tube wall experience a lower centrifugal force than the fluid particles flowing in the tube core. This causes the fluid from the core region to be pushed towards the outer wall. This additional convective transport increases heat transfer and the pressure drop when compared to that in a straight tube.
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Optimisation of outside air pre-cooling via underground conductive heat transfer

Optimisation of outside air pre-cooling via underground conductive heat transfer

Site based measurements were undertaken, whereby soil temperatures at depths of 1 and 2 metres and dry bulb entering exiting air temperatures for the existing system were obtained. Through the use of these site based measurements and ANSYS Simulation Software a comparison model and simple straight run model was developed to portray the effects that, pipe diameter, airflow velocity and system length has on the exiting air temperatures. This allowed numerical results from ANSYS to be compared against the existing operational system results obtained from site and against previous literature to conclude with the recommended findings and develop the tabled system selections. Upon review of the results it could be seen that pipe diameter had the greatest effect on performance relative to pipe length and that the greatest change occurred within the first 10m with respect to length. It could also be seen that as velocity of air flow increased, the performance of the system decreased. During a review of the existing literature it was found that the typically installed pipe materials were found to have minimal effect on performance and that capital expenditure would be the determining factor on pipe material selection.
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Constructul design of tree-shaped conductive pathways for cooling a heat generating volume

Constructul design of tree-shaped conductive pathways for cooling a heat generating volume

Whereas the paths of heat conduction are like a tree network, the amount of the angle among these pathways has a determinant role at the value of heat conduction. Therefore, prior to starting the main problem, the problem related to angle among the pathways is discussed to find the angle by which the thermal resistance minimizesIn order to answer this question, some numerical stimulation should be done considering the angle among the pathways as an independent variable. Regarding the fact that, if the thermal conduction pathways being designed in a way that the accessibilities of the pathways to all hot spots become uniform, better heat transfer will be achieved. So, it seems that, if the angle among the blades being considerd equal to each other, it will be close to the optimal state. Thus, the angle among the thermal conduction pathways is assumed equal to (360/n+1) degree, where n is the number of pathways with high thermal conductivity coefficient. In order to investigate the validity of the discussed analysis, the obtained result with explained hypothesis is compared to the results of [23]. In [23], the angle among the blades was considered constant and equal to 90 degrees so that the angle between blades and tree caber is set to 45 degrees. Also, number of blades in different states of the stimulation is considered constant and equal to four. Finally, the problem which was probed in reference [23] is repeated by considering the same situation and just with this difference that the angle among the thermal conduction pathways is set to (360/n+1). By considering the number of blades (n=4), the angle among the pathways is counted to 72 degrees.
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Thermal Diffusivities and Conductivities of Molten Germanium and Silicon

Thermal Diffusivities and Conductivities of Molten Germanium and Silicon

Thermal diffusivity values of molten germanium and silicon were measured by a laser flash method. Simple but useful sample cell systems were developed to keep the molten germanium and silicon shape uniform for a given thickness. In the present experimental condition, it is necessary to consider the effect of not only the radiative heat loss but also the conductive heat loss at the interface between the molten sample and the cell material under the present experimental conditions. However, the computer simulation results suggest that the conductive heat loss is found to be negligibly small. The thermal diffusivity values of molten germanium and silicon are given in the following equations (unit: m 2 /s).
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