Heat Transfer Calculation Method Research Articles

Simulation and Experimental Verification of Dynamic Heat Load for the Underground Structure Envelope

Analyses the mechanisms of dynamic heat transfer in the underground works envelope and the simplified calculation method for heat transfer. With the cooperative function of MATLAB, Simulink and COMSOL, simulates the dynamic variation of the heat load, and validates the simulation results by an experiment.

COP-based optimization of accelerated flow evaporators for household refrigeration applications

This paper reports an investigation on the impact of an alternative evaporator design, the so-called Accelerated Flow Evaporator (AFE), on the performance of household refrigerators. In this novel evaporator concept, the air-side cross-section area decreases with the distance from the air flow inlet, accelerating the air as it flows across the tubes and hence improving the air-side local heat transfer coefficient. An AFE heat transfer and pressure drop calculation method proposed elsewhere [1] has been incorporated into an overall system simulation model [2] to assess the impact of the evaporator geometry on the system COP. The results were compared with experimental data obtained in a top-mount refrigerator. The predictions of working pressures, power consumption, cooling capacity and COP agreed with the experimental data to within ±10% error bands. The model was subsequently used in an optimization exercise of the AFE geometry that considered both the system COP and the evaporator mass of material.

An improved model and the thermodynamic calculation method for tailrace tunnel ventilating system in hydropower station

Tailrace tunnel ventilating can be used as a highly efficient and energy saving air conditioning for factory buildings in hydropower station. This paper describes an improved model of heat and moisture transfer for tailrace tunnel ventilating system with the assumption of thermal insulated for the tunnel wall and with the same temperature at any cross section as the wet bulb temperature of that air, and the improved model has been validated against the field test from Yingxiuwan hydropower station and compared with the reference simplified model, the results show that the improved model has a good agreement with the field test data and a better precision than the reference simplified model for the performance prediction of heat and moisture transfer of tailrace tunnel ventilating, especially for the short tunnel system. Moreover, the thermodynamic calculation method of heat and moisture transfer is presented, and the method is intended for use in annual performances prediction or design tools for tailrace tunnel ventilating system in hydropower station.

非構造メッシュを用いたラージ・エディ・シミュレーションに適した並列ふく射伝熱計算法(熱工学,内燃機関,動力など)

A parallel calculation method for radiative heat transfer that is suitable for LES (Large Eddy Simulation) on unstructured mesh is proposed. It is based on a discrete transfer radiation model coupled with a coarse mesh generation technique. Each coarse cell is automatically generated by grouping of a certain number of cells used for fluid dynamics calculation. The number of cells in a group is called agglomeration ratio. Two thermal radiative heat transfer problems are solved for validation. One validation case is a three-dimensional L-shaped geometry problem. The results of heat flux obtained by the proposed radiation method agree well with the result of Sakami et al. Simulation speed of radiation is improved by a factor of 7.4 when the agglomeration ratio is 8. The other validation case is a high temperature (1420[K]) turbulent jet, which is solved by a LES code coupled with the proposed radiation method. Calculated temterature distributions agree well with experimental data if radiative heat transfer is taken account. The simulation speed is improved by a factor of 8 when the agglomeration ratio is 16. The temperature error caused by the cell grouping is less than 23[K].

Zonal-iterative calculation method for radiation heat transfer in cavity systems

The zonal-iterative calculation method for radiation heat transfer is developed for arbitrary number of zones (opaque diffusely-radiating and reflecting surfaces). This method is based on transformation of the initial integral equations to equivalent system of integral equations with smaller kernel norm. The method provides high accuracy at a small number of the zones. The method was used for analysis of effective radiation in an isothermal tube cavity with a longitudinal pyrometric slit. In this case one zone was enough and one of the particular solutions can be obtained analytically.

Development of Calculation Method for Radiative Heat Transfer in an Infrared-active Gas with Narrow-Band Nonuniformity and Its Examination Based on an Absorption Line Data Base (In Case of a Mixed Gases Field Including H2O and CO2)

It is necessary to consider the interrelation of absorption coefficients of emitting side and absorbing side when we carry out numerical predictions of radiative heat transfer through infrared-active gases. If we utilize the combination of a wide-band model and a narrow-band model for dealing with radiative heat transfer through a infrared-active gas that has remarkable narrow band nonumiformity, we have to consider the interrelation of absorption coefficient not only about the representative value within a narrow band but also about the fine structure in a narrow band. Calculation method for radiative transfer in nonisothermal field is constructed considering narrow band nonuniformity. It is compared with line-by-line calculation based on absorption line database HITEMP, and its validity is confirmed.

Development of Calculation Method for Radiative Heat Transfer in an Infrared-active Gas with Narrow-Band Nonuniformity and Its Examination Based on an Absorption Line Data Base (In Case of a Nonisothermal Field Including a Single Infrared-Active Gas)

This paper proposes a rational, explicit and practicable approach for incorporating the spectral non-uniformity of absorption coefficient within a narrow band into a nongray analysis of radiative heat transfer in a nonisothermal field including a single infrared-active species. In the development of this new approach, attention is paid to securing rationality and explicitness even when the approach is applied to nonisothermal fields. This aim is achieved based on the fact that the line center of each absorption line does not move even if the gas temperature varies. Validity of the proposed approach is examined in detail trough comparison of the results obtained by the proposed approach with the results of line-by-line analysis base on a high-resolution database of absorption lines. It was confirmed in a typical nonisothermal field that the proposed approach can properly incorporate the influence of narrow band non-uniformity into a nongray analysis of radiative heat transfer in a nonisothermal field including a single infrared-active species.

The contribution of the nucleation process to grain formation in calculating solidification microstructure by CA-DFD

To predict solidification macrostructures, the direct finite difference (DFD) method for heat transfer calculation was coupled with cellular automaton (CA). In the CA-DFD, the nucleation process as the initial condition of calculations was determined according to Gaussian distribution or being instantaneous. In the case of Gaussian distribution, there are six nucleation-related parameters. In this work, the inspection of relationships of preset nuclei to grain, preset nuclei to born nuclei, and born nuclei to grain was carried out by comparison of each ratio. However, these relationships are only valid under the same solidification environments. In contrast to the preset method, the successive nuclei setting method (SNS) was carried out. This method manages the nucleus settings by every time step. The microstructures by SNS were compared with those by preset.

Periodic Unsteady Flow Aerodynamics and Heat Transfer: Studies on a Curved Surface, Combined Part I and II

Aerodynamic and heat transfer investigations were done on a constant curvature curved plate in a subsonic wind tunnel facility for various wake passing frequencies and zero pressure gradient conditions. Steady and unsteady boundary layer transition measurements were taken on the concave surface of the curved plate at different wake passing frequencies where a rotating squirrel‐cage generated the unsteady wake flow. The data were analyzed using timeaveraged and ensemble‐averaged techniques to provide insight into the growth of the boundary layer and transition. Ensemble‐averaged turbulence intensity contours in the temporal spatial domain showed that transition was induced for increasing wake passing frequency and structure. The local heat transfer coefficient distribution for the concave and convex surface was determined at those wake passing frequencies using a liquid crystal heat transfer measurement technique. Detailed aerodynamic and heat transfer investigations showed that higher wake passing frequency caused transition to occur earlier on the concave surface. Local Stanton numbers were also calculated on the concave surface and compared with Stanton numbers predicted using a differential boundary layer and heat transfer calculation method. On the convex side, no effect of wake passing frequency on heat transfer was observed due to a separation bubble that induced transition.

The Effect of Periodic Unsteady Flow on Aerodynamics and Heat Transfer on a Curved Surface

Aerodynamic and heat transfer investigations were performed on a constant curvature curved plate in a subsonic wind tunnel facility for various wake passing frequencies under zero pressure gradient conditions. Steady and unsteady boundary layer transition measurements were taken on the concave surface at different wake passing frequencies in which a rotating squirrel cage was used to generate the unsteady wake flow. The data were analyzed using time-averaged and ensemble averaged techniques to provide insight into the growth of the boundary layer and transition. Ensemble averaged turbulence intensity contours in the temporal spatial domain showed that transition was induced for increasing wake passing frequency and structure. The local heat transfer coefficient distributions for the concave and convex surfaces were determined for each wake passing frequency using a liquid crystal heat transfer measurement technique. Aerodynamic and heat transfer investigations showed that higher wake passing frequencies caused earlier transition on the concave surface. Local Stanton numbers were calculated on the concave surface and compared to Stanton numbers predicted using a boundary layer and heat transfer calculation method. On the convex side, no effect of wake passing on heat transfer was observed, due to a separation bubble that induced transition.

Heat Transfer in the Rod Bundles and Thermal Analysis of Constor RBMK Cask Under Normal Storage Conditions

For demonstrating the safety of the casks intended for spent nuclear fuel transport and storage, the maximum temperature of the nuclear fuel rod cladding must be defined. For the gas filled CONSTOR RBMK metal-concrete cask developed jointly by GNB (Germany) and AOOT NPO CKTI (Russia) for RBMK-1000/1500 assemblies (Russian design) storage and transport the thermal analysis has been carried out for normal and fire accident conditions of operation. This paper is devoted to the description of the method applied to the analysis of heat transfer in the basket with assemblies disposed in the cask cavity. The combined analytical and numerical method for heat transfer calculation in the cask cavity based on a two-zone model of heat transfer inside the assembly has been developed and verified by means of the tests performed with an electrically heated bundle model consisting of 127 rods. One of the main features of the method is the real multi-rod assembly substitution by a homogenous heat-releasing bar with effective heat conductivity enclosed in the heat-conducting casing which models the basket tube.

Radiation Heat Transfer in Three-dimensional Closed Space Including Diffuse and Specular Surfaces. Numerical Calculation Method using Improved Ray Tracing Method.

A numerical calculation method of radiation heat transfer in a three-dimensional closed space including diffuse and specular surfaces has been developed. In order to enable to analyze the radiation heat exchange on each surface considering multiple specularly reflections and obstacles of radiation in the space, the improved heat ray tracing method was presented for calculating above-mentioned view factors accurately. It was examined to be applicable to complicated problems by test calculations using a few models with specular surfaces and obstacles. Continuing effort is applied to a more realistic problem. The example cited in this paper is the infrared emitter with a parabolic specular reflector, which is the common electric heating apparatus. The measured result of a radiant irradiated power distribution agrees well with the calculated one. The practical validity of our method was verified.

Theoretical and Experimental Study on Heat Transfer and Thermal Performance of Concentration Solar Collector of Horizontal Coaxial Cylinders

Heat transfer and thermal performance of the concentrating solar collector of horizontal coaxial cylinders for a solar thermal power source are studied theoretically and experimentally. The design parameters considered in the theory are the concentration ratio, the diameters of a semi-transparent glass tube and a selective absorber tube, the effective length and the optical property of an absorber tube, the storage temperature, the pressure in the annulus, and the inlet temperature and the flow rate of a heat transfer medium. The thermal performance of the absorber system is evaluated by the outlet temperature of the fluid, the collector efficiency, the exergy efficiency and the final conversion efficiency. The experimental results confirm the calculation method of heat transfer and thermal performance.

Comparison of rocket nozzle heat transfer calculation methods

misalignment effects. Also, a simple method of discretization that is suitable for programming is discussed here. At this stage, it is suggested that the entire problem of the static aeroelastic analysis of guided launch vehicles, including various misalignment effects, may be approached systematically in order to find out which factor has the greatest contribution to the aeroelastic behavior of the vehicle. As a first step, one may analyze this problem by including the flexibility of vehicle and assuming rigid joints. Later, joint rotations, misalignment effects, etc., may be included in succession. This will provide a clear picture to the understanding of the problem. Also, it may be of considerable help to the designer before he takes up the dynamic aeroelastic investigations.

External heat transfer—calculation methods and moist material drying kinetics

The method, based on the use of the Rebinder number, for calculating the duration of drying and the heat transfer is set forth and the relationships for the Nusselt numbers in the first and second periods are given.

Heat exchange during the flow of mercury and water in a closely packed bundle of rods

The paper is a report of an experimental investigation into heat transfer to mercury and water from closely packed rods. Thermal modelling problems are discussed, figures are given for the temperature field of the heat exchange surface and the rigs, test procedure and analysis are described. An approximate heat transfer calculation method is suggested for a particular arrangement of closely packed rods.

AN INTEGRAL METHOD FOR CALCULATING HEAT AND MASS TRANSFER IN LAMINAR BOUNDARY LAYERS

An integral method previously used successfully in several kinds of boundary layer problems has been extended to treat simultaneous heat and mass transfer in a binary-mixture laminar boundary layer when the pressure is uniform. The principal results are two pairs of dual integral relations arising from solutions to the integral concentration and energy equations. One pair connects the surface mass transfer rate and surface concentration of injected gas; the other relates surface temperature and heat transfer rate in the presence of mass transfer. Only the cases of helium and air injection into an undissociated air stream are discussed in detail, but the method can be applied to problems involving other gases. The approximate results agree quite well with some numerical solutions and with recent experimental results for which no numerical solutions are available.

Approximate calculation method for heat transfer in laminar boundary layers with constant surface temperature

A simple method for the calculation of heat transfer in a laminar, constant property and constant surface temperature flow, was described by Smith and Spalding [1]. In the present paper, the method is extended to the range of Prandtl numbers 0.7 to 10. Examples are given of heat transfer calculations for ellipses of 2:1 and 4:1 fineness ratio.