Heat Conduction

Physics defines heat as; Thermal energy transferred from a hotter system to a cooler system that is in contact, the heat energy unit is Joules (J), In general, three different modes of heat transfer are recognized: Conduction, convection, and radiation. The theory of the greenhouse effect erases the infrared radiation and the heat transfer by contact of the gas molecules in the atmosphere (14°C), and teaches us that the greenhouse gases (0.04% of the atmosphere), They receive a radiation heat transfer from the surface of the earth whose average temperature is 2.82°C, and these gases re-radiate it in all directions. We see many errors in the theory of the greenhouse effect; 1. When radiation heat transfer occurs is produced by changes in the electronic configurations of constituent atoms or molecules and transported by electromagnetic waves or photons. 2. It tells us that the surface of the Earth does not transfer its heat to the Atmosphere by conduction, when it is in contact with its surface, but by radiation. 3. It tells us that the Sun emitting infrared radiation at all known wavelengths does not emit infrared radiation at the wavelength emitted by the earth's surface. 4. It does not take into account all molecules in the atmosphere that also emit their temperature as infrared radiation. 5. It only takes into account 0.04% of the molecules in the atmospheric system, as a new way of transferring heat, not by its own infrared radiation, but as a way to radiate the heat radiated by the earth's atoms. 6. It teaches us that the earth's surface with an average temperature of 2.82°C can transfer irradiated heat to the greenhouse gases of the atmospheric system, with an average temperature of 14°C.

The calculation of vibrational properties of materials from their electronic structure is an important goal for materials modeling. A wide variety of physical properties of materials depend on their lattice-dynamical behavior: specific heats, thermal expansion, and heat conduction; phenomena related to the electron-phonon interaction such as the resistivity of metals, superconductivity, and the temperature dependence of optical spectra, are just a few of them. Moreover, vibrational spectroscopy is a very important tool for the characterization of materials. Vibrational frequencies are routinely and accurately measured mainly using infrared and Raman spectroscopy, as well as inelastic neutron scattering. The resulting vibrational spectra are a sensitive probe of the local bonding and chemical structure. Accurate calculations of frequencies and displacement patterns can thus yield a wealth of information on the atomic and electronic structure of materials.

Experimental investigation was conducted to measure the convective heat transfer coefficient and thermal performance of plate fins and plate cubic pin-fins heat sinks, under natural convection regime. The investigation was conducted for Rayleigh number from 8×10 6 to 9.5×10 6 and input heat of 10 W to 120 W. The fin spacing and fin numbers are varied between 5-12 mm and 5-9, respectively. The results demonstrated that plate cubic pin-fins heat sinks have lower thermal resistance and higher heat transfer, compared to plate fins heat sinks. Heat transfer enhancement of new-designed heat sinks is about 10% to 41.6% higher, compared to normal pin-fins. Increasing fin spaces in all types of studied heat sinks cause lower thermal resistance. But, increasing fin numbers does not cause better heat transfer. The best heat sink design was a plate cubic pin-fin heat sink with 7 fins and 8.5 mm fin spacing. Finally, empirical equations have been developed to correlate the average Nusselt number as

The crosslinking of the unsaturated polyester was studied by using experiments and a model of the process. The kinetic parameters were calculated from the heat flux-time curves obtained by differential scanning calorimetry (DSC, Netzsch-Simultaneous Thermal Analyser DSC 200), working in DSC (dynamic) mode. The temperature-time histories were studied in plain sheet copper mould. The mathematical model was constructed by taking into account the heat transferred by conduction through the resin, as well as the kinetics of heat generated by the crosslinking reaction. The contributions to the rise in temperature from heat conduction and chemical reaction are different in different parts of the composite, and can explain the temperature-, or degree of crosslinking (DOC)time histories. By considering temperature-time histories developed within the sample, more extensive knowledge of the process can be obtained. The effect of the heat transfer by conduction through the composite as well as the internal heat generated by the cure reaction is clearly shown, despite the complexity of the process. Finally, good agreement between experimental data and predicted mathematical model of the crosslinking process in plane sheet mould was shown.

A consistent description of a shear flow, the accompanied viscous heating, and the associated entropy balance is given in the framework of a deterministic dynamical system, where a multibaker dynamics drives two fields: the velocity and the temperature distributions. In an appropriate macroscopic limit their transport equations go over into the Navier-Stokes and the heat conduction equation of viscous flows. The inclusion of an artificial heat sink can stabilize steady states with constant temperatures. It mimics a thermostating algorithm used in non-equilibrium molecular-dynamics simulations.

A numerical study has been carried out to understand and highlight the effects of axial wall conduction in a conjugate heat transfer situation involving simultaneously developing laminar flow and heat transfer in a square microchannel with constant flux boundary condition imposed on bottom of the substrate wall. All the remaining walls of the substrate exposed to the surroundings are kept adiabatic. Simulations have been carried out for a wide range of substrate wall to fluid conductivity ratio (k sf $ 0.17-703), substrate thickness to channel depth (d sf $ 1-24), and flow rate (Re $ 100-1000). These parametric variations cover the typical range of applications encountered in microfluids/microscale heat transfer domains. The results show that the conductivity ratio, k sf is the key factor in affecting the extent of axial conduction on the heat transport characteristics at the fluid-solid interface. Higher k sf leads to severe axial back conduction, thus decreasing the average Nusselt number (Nu). Very low k sf leads to a situation which is qualitatively similar to the case of zero-thickness substrate with constant heat flux applied to only one side, all the three remaining sides being kept adiabatic; this again leads to lower the average Nusselt number (Nu). Between these two asymptotic limits of k sf , it is shown that, all other parameters remaining the same (d sf and Re), there exists an optimum value of k sf which maximizes the average Nusselt number (Nu). Such a phenomenon also exists for the case of circular microtubes.

Using a block model of 1532 cubical cells, temperature distributions are calculated for the lowest 21 cm of the human leg for electric fields recommended in the ANSI RF safety guideline. The thermal model uses inhomogeneous volume-averaged tissue properties: blood-flow rate, metabolism, thermal conductivity, specific heat, etc. The SAR's are obtained using the impedance method. A modified method of finite difference technique is used to solve the 3-D heat conduction equation for the thermal model. Numerical results are obtained for RF currents at 3 and 40 MHz projected for the E fields recommended by the ANSI Standard (614 and 61.4 V/m, respectively) and also for power densities one-tenth of that level. Temperatures as high as 41.6" are obtained for some internal cells for the higher Efields while relatively moderate temperatures on the order of 37°C are obtained for the lower E fields. Some of the calculated results for the surface temperature have been compared and found to be in good agreement with the experimental data for initial rates of heating.

A numerical model was developed for the computation of the wind field, air temperature and humidity in the urban canopy layer and in the atmospheric boundary layer above urban areas. The model is of k–ε type. The ensemble-spatial averaged three-dimensional Reynolds equations, equation of continuity, turbulent kinetic energy equation (k-equation), and equation for dissipation rate of turbulent energy (ε-equation) are solved together with equations of heat and moisture transfer in the air. Inside the urban canopy layer, volumes of buildings and other urban structures are accounted for by a spatial averaging procedure. With given average building height and building width for each grid mesh, effects of buildings on the momentum transfer are modelled by introducing a form drag force. Temperatures of the ground surface, building walls or roof are computed by the solution of the heat conduction equation in the ground or walls, roof. Evaporation at the ground surface is evaluated using a Bowen ratio. The exhausted heat by building air conditioning is evaluated by employing a building air conditioning model. This heat together with traffic-induced artificial heat are accounted for in the model as heat sources. A numerical model for the momentum, heat and moisture transfer in the plant canopy is also coupled to the model to investigate the effects of vegetation on the urban climate. Verification of the model against observational data in the Tokyo Metropolitan area, Japan, reveals that the model is capable of simulating the momentum, heat and mass transfer in the urban boundary layer. Especially, the model can compute air temperature, humidity and wind velocity at the street level, which cannot be computed by a general above city atmospheric circulation model.

The ultrasonic pulse-echo backscattered amplitude integral (BAI)-mode imaging technique [IEEE Trans. UFFC, 45:30 (1998)] has demonstrated sensitive detection of subwavelength channel defects (38-m diameter reliably and 6-m diameter occasionally) in flexible 220-m-thick food package seals (17.3 MHz, Ϸ 86 m). However, the underlying subwavelength defect detection mechanism is poorly understood. In this contribution, a theoretical modeling study was undertaken to elucidate the mechanism. The subwavelength diameter channel was fused in-between two plastic package films by applying heat from one side of the films. The sample cross-section microstructure was characterized from both optical and acoustic images. The cross-section impedance profiles along sample thickness dimension were determined. Although identical in nominal impedance properties before sealing, the two binding films showed an asymmetric impedance profile after sealing. Transient finite-element heat conduction analysis and impedance profiles of multiple-sealed package samples showed that the single-sided heating process caused an asymmetric impedance profile. A generalized impedance model was proposed based on these observations. An efficient two-dimensional simulation tool using a finite-difference time-domain method and the perfectly matched layer numerically evaluated the defect detection behavior of the radio-frequency (rf) echo waveforms. The normalized correlation coefficients between the simulated and the measured rf echo waveforms were greater than 95% for this generalized model, which suggested the validity of the proposed impedance model.

In the present paper we extend the fourth order method developed by Chawla et al. [M.M. Chawla, R. Subramanian, H.L. Sathi, A fourth order method for a singular twopoint boundary value problem, BIT 28 (1988) 88-97] to a class of singular boundary value problems

Numerical solutions have been obtained for the nonlinear heat conduction equations arising in the theory of thermal explosions. Explosion times are calculated for externally heated spheres, cylinders, and slabs of several explosive materials, and the results are shown to agree with experiment.

Thermal conductivity of particulate beds is an important property for many industrial handling processes as well as for storage of particulate materials. This paper presents a new theoretical model that is based on heat transfer between particles in three modes: heat conduction through contact area, heat conduction through voids and radiation through voids. The model is further adjusted in order to obtain effective thermal conductivity of a particulate bed by using empirical augmentation factors for the heat transfer coefficient of each one of the heat transfer mechanisms. Comparison of the results predicted by the semi-empirical model to our experimental results show good agreement. The theoretical model was investigated to examine the effect of various parameters (such as: particle elasticity and surface roughness, particle and gas thermal conductivity and particle diameter), on the effective thermal conductivity of various particulate beds. Our results show the significant effect of the contact area (that is a clear function of the compression load) between particles on the effective thermal conductivity.

Kinetics of solidification of phase change materials (PCM) was analyzed for combined heat conduction in the PCM and container wall, and convection in the cold fluid. Stable and convergent numerical methods were derived after transformation to normalized size scale, and corresponding immobilization of the moving boundary. The accuracy was confirmed by comparing numerical solutions and corresponding analytical solutions for control by heat conduction in solidifying layers. The proposed method was used to assess when solidification is controlled solely by conduction in solidified layer, and to analyze relative roles of conduction through the container and convection in the cold fluid.

The paper presents a short survey of three topics: modern sensor networks, distributed parameter systems and estimation techniques, especially using artificial intelligence tools, to be involved in the new domain of identification of distributed parameter systems, based on sensor networks and artificial intelligence. As smart and small devices the modern sensors are capable to be implemented in large distributed parameter systems. Sensor networks, with hundred and thousands of ad-hoc tiny sensor nodes spread across a geographical, are acting as a distributed sensor in a distributed parameter system. Sensor network topics, sensor network architectures and sensor network applications are presented. Examples of distributed parameter systems with large application in practice as the process of heat conduction, applications related to electricity domain, motion of fluids, the processes of cooling and drying, phenomenon of diffusion and other applications are presented. The identification...

ABSTRACT One of the most efficient ways to reduce the pollution and fuel consumption of an automotive engine is to downsize the engine, whilst maintaining a high level of power and torque. This is achieved by using turbochargers. In urban, and often in suburban, traffic conditions the engine power demand is weak in relation to the maximum power available, so the turbocharger runs at low speed. To appreciate and improve engine performance, it is necessary to know the characteristics of the turbomachinery in this functioning area, characteristics which are not given by turbocharger manufacturer. The reason for this lack of information will be explained and the experiments we are currently conducting at low turbocharger speed are presented. Experimentally, it has been demonstrated that the measured performances of the compressor are dependent on heat exchange (convection and conduction) and are also linked to the pressure and temperature of the lubricating oil. At the CNAM laboratory, the turbocharger test rig has been equipped with a special torquemeter, allowing rotation speeds of up to 120000 rpm, set up between the turbine and the compressor. The turbine is thus separated from the compressor and could be considered as a drive which provides mechanical power to the turbocharger (torquemeter + compressor + bearing unit). Temperature and pressure of the lubricating oil can be adjusted to an experiment’s requirements. The test bench lay out is described. To achieve accurate measurements and evaluate the influence of heat exchanges, tests have been carried out with the whole compressor thermally isolated and with preheated inlet air. The compressor can be assumed to be adiabatic, and the power given to the air flow can be calculated using the first law of thermodynamics. Mechanical bearing losses can be deduced from this calculation and torquemeter power, but also from measurements of lubricating oil flow, and oil temperature at inlet and outlet. The results of experiments for different lubricating oil temperatures and pressures and turbocharger speeds are presented. Real compressor characteristics curves are set up and a comparison of experimental mechanical power losses with a journal bearing CFD model is presented.

A model is presented of stationary shearing produced during the chip formation in orthogonal cutting. The work material is supposed to be a thermal sensitive viscoplastic rigid material. The effects of material parameters, of heat conductivity and of inertia on the distribution of strain rate and of temperature in the primary shear zone are analysed. The cutting forces are calculated for a large range of cutting speeds including high speed machining. The results are obtained by developing a simple one-dimensional modelling of the primary shear zone. Experimental measurements are compared with the theoretical results. Copyright ,~ 1996 Elsevier Science Ltd.

Thermal-sprayed heat exchangers were tested at high temperatures (750 C), and their performances were compared to the foam heat exchangers made by brazing Inconel sheets to their surface. Nickel foil was brazed to the exterior surface of 10-mm-thick layers of 10 and 40 PPI nickel foam. A plasma torch was used to spray an Inconel coating on the surface of the foil. A burner test rig was built to produce hot combustion gases that flowed over exposed face of the heat exchanger. Cooling air flowed through the foam heat exchanger at rates of up to 200 SLPM. Surface temperature and air inlet/exit temperature were measured. Heat transfer to air flowing through the foam was significantly higher for the thermally sprayed heat exchangers than for the brazed heat exchangers. On an average, thermally sprayed heat exchangers show 36% higher heat transfer than conventionally brazed foam heat exchangers. At low flow rates, the convective resistance is large (~4 3 1022 m2 K/W), and the effect of thermal contact resistance
is negligible. At higher flow rates, the convective resistance decreases (~2 3 1023 m2 K/W), and the lower contact resistance of the thermally sprayed heat exchanger provides better performance than the brazed heat exchangers.

The paper considers a problem in which a steady-state sonic wave is propagated in the longitudinal direction in a fluid enclosed between two horizontal parallel plates which are kept at different temperatures;. The distance between the plates is much smaller than the sound wavelength. Rayleigh's vortical acou~stic streaming that appears in the region between the plates as a result of the sound wave leads to forced heat convection. The effect of that forced convection on heat transferred between the plates is analyzed theoretically. An acoustic Peclet number, which represents the interaction between heat conduction and #orced convection is introduced, and asymptotic relations expressing the mean Nusselt number in terms of this dimensionless group are derived. The results obtained demonstrate that acoustic streaming results in a marked enhancement of heat transfer between the plates.

This paper deals with inhomogeneous shearing deformation of an in"nite rubber-like slab under a temperature di!erence across its thickness. The deformation is analyzed within the context of "nite thermoelasticity with entropic origin for the stress. The isothermal strain energy functions of Mooney and of Yeoh are generalized by incorporating them into the thermoelastic model. The energy balance equation, which is decoupled from the linear momentum balance equations, is solved for the temperature "eld using the Fourier's law of heat conduction. The derived linear temperature "eld and the equations of the thermoelastic model are inserted into the linear momentum balance equations, thus yielding an ordinary di!erential equation for the shear strain. The shear strain, the degree of inhomogeneity in the shear strain, the stress "eld, and the principal stresses are then determined using a "nite di!erence method. The Mooney slab undergoes markedly greater shear strain near the colder boundary, thus exhibiting a boundary layer-like structure at higher temperature di!erences across the thickness. However, the Yeoh slab exhibits a relatively smaller variation of the shear strain even at the highest temperature di!erence. This di!erence in the behavior of the two slabs is attributed to the shear sti!ening of the Yeoh slab, which counteracts the formation of a boundary layer-like structure. Both slabs experience constant shear stresses across the thickness, whereas they experience much greater normal stress di!erences varying across the thickness. The values of the major principal stress turn out to be close to those of the "rst normal stress di!erence. The presence of a large normal stress di!erence compared with a relatively smaller shear stress in the slabs creates the possibility for Mode I type fracture propagation. (E. Bilgili). these materials when subjected to temperature gradients and "nite deformations. Rubber-like materials show non-linear stress}strain behavior, exhibit large deformation even under small loads, and have material parameters dependent on temperature . The coupling between the deformation and temperature increases the complexity of the non-linear equations that arise in "nite deformation of rubber-like materials.

The power of the handheld electronics devices continues to increase because packaging advances reduce their size even as more features are added and enhanced. The computational fluid dynamics (CFD) numerical simulation is performed on thermal management of the mobile phone using a heat storage unit (HSU) filled with the phase change material (PCM). The chips and HSU are embedded in an epoxy polymer casing. The PCM absorbs the heat dissipation from the chips and stores as latent heat to maintain the chip temperature below the allowable service temperature. Eight cases of simulations are carried out with or without PCM at several power dissipations. The use of PCM in mobile phone has shown to be effective in keeping the chip temperature down to acceptable level for certain duration.

The analytical solution for a vertical heated plate subjected to conjugate heat transfer due to natural convection at the surface and conduction below is presented. The heated surface is split into two regions; the uniform heat flux region toward upstream and remaining fraction as the uniform wall temperature region. The fractional areas under the two regions are considered variable. Adopting thermally thin wall regime approximation, the possible solutions were investigated and found to satisfactorily deal with longitudinal conduction and temperature variation in the transverse direction. A test setup was developed and the experiments were conducted to obtain relevant data for comparison with the analytical solutions. The ranges for Rayleigh number and heat conduction parameter (α) during various test conditions were 2×108–6×108, and 0.001–1, respectively. The limiting solutions for stipulated conditions are analyzed and compared with experimental data. Reasonable agreement is obser...

Bone ablation using different pulse parameters and four emission lines of 9.3, 9.6, 10.3, and 10.6 μm of the CO2 laser exhibits effects which are caused by the thermal properties and the absorption spectrum of bone material. The ablation mechanism was investigated with light- and electron-microscopy at short laser-pulse durations of 0.9 and 1.8 μs and a long pulse of 250 μs. It is shown that different processes are responsible for the ablation mechanism either using the short or the long pulse durations. In the case of short pulse durations it is shown that, although the mineral components are the main absorber for CO2 radiation, water is the driving force for the ablation process. The destruction of material is based on explosive evaporation of water with an ablation energy of 1.3 kJ/cm3. Histological examination revealed a minimal zone of 10–15 μm of thermally altered material at the bottom of the laser drilled hole. Within the investigated spectral range we found that the ablation threshold at 9.3 and 9.6 μm is lower than at 10.3 and 10.6 μm. In comparison the ablation with a long pulse duration is determined by two processes. On the one side, the heat lost by heat conduction leads to carbonization of a surface layer, and the absorption of the CO2 radiation in this carbonized layer is the driving force of the ablation process. On the other side, it is shown that up to 60% of the pulse energy is absorbed in the ablation plume. Therefore, a long pulse duration results in an eight-times higher specific ablation energy of 10 kJ/cm3.

A finite element weighted residual process has been used to solve transient linear and non-linear two-dimensional heat conduction problems. Rectangular prisms in a space-time domain were used as the finite elements. The weighting function was equal to the shape function defining the dependent variable approximation. The results are compared in tables with analytical, as well as other numerical data. The finite element method compared favourably with these results. It was found to be stable, convergent to the exact solution, easily programmed, and computationally fast. Finally, the method does not require constant parameters over the entire solution domain.

A numerical approximation of the Green's function equation based on a heat-flux formulation is given. It is derived by assuming as a functional form of the surface heat flux a stepwise variation with space and time. The obtained approximation is very important in investigation of the inverse heat conduction problems (IHCPs) because it gives a convenient expression for the temperature in terms of the heat flux components. Additionally, it is very important for the unsteady surface element (USE) method which is a modern boundary discretization method. Green's function approximate solution equation (GFASE) also creates 'naturally' fixed groups or modules of work elements called ''building blocks'' that may be added together to obtain space and time values of temperature. In the current case, they are subject to a partial heating by an applied surface heat flux. The ''building block'' solution can be derived by using the various analytical and numerical approaches available in heat conduction literature though the exact analysis is preferable, as discussed in the text. Poorly-convergent series deriving from Green's functions approach are replaced by closed-form algebraic solutions.

A finite-element approach to thermoelastohydrodynamic lubrication analysis is developed by extending a previous mass-and energy-conserving algorithm to include wall-convection boundary conditions, groove-mixing theory, and thermo-mechanical deformations. To this end, the cross-film-averaged energy equation is coupled with the heat conduction equations relevant to the bearing sleeve and the journal by fitting the temperature profile across the film thickness with a fourth-order polynomial. A finite-element condensation technique is used to reduce the unknowns in heat conduction equations in the bush and in the journal to the temperatures of the sleeve surface and journal axis, respectively. Applied to the analysis of steadily loaded journal bearings, the proposed method shows good agreement with published experimental results and incurs low computational cost.

A novel algorithm for handling material non-linearities in bodies consisting of subregions having different, temperature dependent heat conductivities is developed. The technique is based on Kirchhoff's transformation. The material non-linearity is reduced to a solution dependent function of unified form added to unknown nodal Kirchhoff's transforms. Assembling of element contributions brings the non-linearity to the right hand sides of the global set of equations. The first step of the solution of this set is the Gaussian pre-elimination (condensation) of linear degrees of freedom. At this stage efficient block solvers can be used. Then, a set of non-linear equations is extracted from the condensed one and solved employing the Newton-Raphson technique. The iteratively solved set consists of the least possible number of equations and its Jacobian matrix is calculated efficiently by taking advantage of the specific form of the equations.

The phase-field method has become an important and extremely versatile technique for simulating microstructure evolution at the mesoscale. Thanks to the diffuse-interface approach, it allows us to study the evolution of arbitrary complex grain morphologies without any presumption on their shape or mutual distribution. It is also straightforward to account for different thermodynamic driving forces for microstructure evolution, such as bulk and interfacial energy, elastic energy and electric or magnetic energy, and the effect of different transport processes, such as mass diffusion, heat conduction and convection. The purpose of the paper is to give an introduction to the phase-field modeling technique. The concept of diffuse interfaces, the phase-field variables, the thermodynamic driving force for microstructure evolution and the kinetic phase-field equations are introduced. Furthermore, common techniques for parameter determination and numerical solution of the equations are discussed. To show the variety in phase-field models, different model formulations are exploited, depending on which is most common or most illustrative.

The objective of this paper is to analyze the temperature distributions and heat affected zone in skin tissue medium when irradiated with either a collimated or a focused laser beam from a short pulse laser source. Experiments are performed on multi-layer tissue phantoms simulating skin tissue with embedded inhomogeneities simulating subsurface tumors and as well as on freshly excised mouse skin tissue samples. Two types of lasers have been used in this study-namely a Q-switched pulsed 1064 nm Nd:YAG short pulse laser having a pulse width of 200 ns and a 1552 nm diode short pulsed laser having a pulse width of 1.3 ps. Experimental measurements of axial and radial temperature distribution in the tissue medium are compared with the numerical modeling results. For numerical modeling, the transient radiative transport equation is first solved using a discrete ordinates method for obtaining the intensity distribution and radiative heat flux inside the tissue medium. Then the temperature distribution is obtained by coupling the bio-heat transfer equation with either hyperbolic non-Fourier or parabolic Fourier heat conduction model. The hyperbolic heat conduction equation is solved using MacCormack's scheme with error terms correction. It is observed that experimentally measured temperature distribution is in good agreement with that predicted by hyperbolic heat conduction model. The experimental measurements demonstrate that converging laser beam focused directly at the subsurface location can produce desired high temperature at that location compared to that produced by collimated laser beam for the same laser parameters. Finally the ablated tissue removal is characterized using histological studies as a function of laser parameters.

The ground heat exchangers (GHE) consist of pipes buried in the soil and is used for transferring heat between the soil and the heat exchanger pipes of the ground source heat pump (GSHP). Because of the complexity of the boundary conditions, the heat conduction equation has been solved numerically using alternating direction implicit finite difference formulation. A software was developed in MATLAB environment and the effects of solution parameters on the results were investigated. An experimental study was carried out to test the validity of the model. An experimental GSHP system is installed at Yıldız Technical University Davupasa Campus on 800 m 2 surface area with no special surface cover. Temperature data were collected using thermocouples buried in soil horizontally and vertically at various distances from the pipe center and at the inlet and the outlet of the ground heat exchanger. Experimental and numerical simulation results calculated using experimental water inlet temperatures were compared. The maximum difference between the numerical results and the experimental data is 10.03%. The temperature distribution in the soil was calculated and compared with experimental data also. Both horizontal and vertical temperature profiles matched the experimental data well. Simulation results were compared with the other studies.

It was possible to describe large number of processes such as melting, solidification, microwave thawing, spray-drying, and freeze-drying by a single theoretical model. All these applications and some others have one thing in common, that is the formation of a moving interface during the process of heat and mass transfer. This interface may be defined by a sharp boundary or by a region, depending on the application considered. The unsteady-state heat conduction equation was found to describe well the transport of heat in these processes. Two different numerical solutions have been developed, one for the sharp interface and the other for materials that undergo phase transformation within a range of temperatures. In spite of the large variation in the applications considered in this paper, the agreement was good between the theoretical predictions and our experiments, and some of the measurements available in the literatures.

Vacuum glazing consists of two glass sheets with a narrow internal evacuated space. The separation of the sheets under the influence of atmospheric pressure is maintained by an array of small support pillars. The thermal resistances associated with the heat flow through individual pillars, and through the pillar array, are calculated using a simple analytic method, and by more complex finite element models. The results of both approaches are in very good agreement, and are validated by comparison with experimental data. It is shown that, for many purposes, the amount of heat which flows through the pillars can be determined without incurring significant errors by assuming that the heat flow is uniformly distributed over the area of the glass. Finite element modelling, and a superposition method, are used to determine the temperature distribution on the external surfaces of the glass sheets due to pillar conduction. Again the results obtained with both approaches are in very good agreement. An approximate method is described for calculating the magnitude of these temperature non-uniformities for all practical glazing parameters.

In this paper we study the laminar condensation process of a saturated vapor in contact with one side of a vertical thin plate, caused by a natural laminar boundary layer flow on the other surface of the plate. The effects of both longitudinal and transversal heat conduction in the plate are considered. The momentum and energy balance equations are reduced to a system of differential equations with five parameters. Asymptotic and numerical solutions for the temperature and condensed film thickness distributions are presented for all possible values of the nondimensional plate thermal conductance cc

Conservation principles are used to represent all physical transformations occurring in the universe, accordingly are also adopted to design runner conduit for thermoplastic melt injection. Conservation principles for thermoplastic melt injection through runner conduit are implemented by considering cylindrical co-ordinates system relevant to its geometrical configuration for deriving governing equations. While the continuity equation ensures volumetric conservation of thermoplastic melt, the momentum equation represents equilibrium of forces on thermoplastic melt injection through runner conduit. During an injection moulding cycle heat and work done energy transformations are balanced by implementing first and second law of thermodynamics. Thermoplastic melt state change through the runner conduit for a particular cycle is appreciated by heat conduction equation. Traditionally inertia and entropy contribution is neglected to skip rigorousness, nevertheless they continue to prevail....

A nonlinear transient heat transfer finite element model is developed to simulate the curing process of polymer matrix composites. Temperature distributions inside laminates can be evaluated by solving the nonlinear anisotropic heat conduction equations including internal heat generation produced by exothermic chemical reactions. Thermal properties are assumed to be both temperature and degree of cure dependent. Thermal properties, degree of cure and internal heat generation due to the exothermic reaction are permitted to vary within an element. Numerical examples are presented to verify accuracy and convergence and to demonstrate use of the present finite element procedure for analyzing composite curing processes. Glass-polyester and Hercules AS4/3501-6 graphite-epoxy composites are considered. Good agreement between experimentally measured and predicted temperature distributions is obtained for various cure cycle histories. 0 1997 Civil-

A set of correlations is developed for transient heat conduction in finite solids (plates, cylinders and spheres) exposed to high Biot number convection boundary conditions. For Bi C 3, the error of the approximate solutions is well below 1% of the initial temperature difference driving the transient.

In warmer climates, buildings made of cement-based materials often exhibit unfavorable thermal characteristics including higher interior temperature, especially in the absence of an active cooling mechanical system. The purpose of this research project was to investigate the thermal effects of newly designed passive cooling systems on concrete roofs in existing buildings. Each tested passive cooling system consists of a combination of materials that can reduce net heat load in buildings. Commercially available materials such as aluminum 1100 and galvanized steel were used as radiation reflectors; and polyurethane, polystyrene, polyethylene, and an air gap were used as insulation. Experimental results based on laboratory-scale prototypes show that the radiation reflector shape as well as the material selection of each passive cooling system led to reductions in heat conduction between 65 and 88% when compared to a control prototype. Each passive cooling system showed a slow thermal time response when compared to a plain concrete roof, which is a desirable characteristic for controlling thermal fluctuations when heat conduction is also reduced simultaneously. Transient empirical models to predict accurately the midpoint temperature of a cement roof were formulated with and without passive cooling systems in use.

Singapore's building regulations require the submission of Envelope Thermal Transfer Value (ETTV) calculations for new buildings. The current ETTV method accounts for the thermal contributions of conventional external shading devices, such as overhangs or fins. For complex façade design solutions, a longer and more complicated calculation process is required. This additional method is based on manual calculations, and can be a deterrent to pursuing more advanced shading strategies. As a response, this paper presents a modified computer-based methodology for ETTV calculation. The study looked into quantifying the shading contribution of different strategies, including interblock shading. Research focused on defining correction factors that can be plugged into the current ETTV equation. These feed into three aspects of thermal heat gain through a building skin -heat conduction through opaque wall, heat conduction through transparent window, and solar radiation through transparent window. The revised methodology was then applied to a case study, to exhibit its ideal application in accounting for non-standard shading devices.