[en] In this paper a boundary element formulation for heat conduction problems are presented. The different types of boundary conditions of condution, convection and radiation are included in the integral equations. The transient fundamental solution is used and by considering small time limits the integration over the time domain are calculated analytically. In the absence of a radiation boundary condition a set of linear system of equations would be developed. While, in the presence of radiation boundary conditions, a set of nonlinear system of equations is resulted. Also presented in this paper a multi-region boundary element analysis for heat conduction problems composed of different materials having different thermal properties. The compatibility and equilibrium are used to link the systems of equations developed for each region. Examples are provided to check the accuracy of the method and the implementation. (orig.)

[en] The authors consider nonadiabatic premixed flame propagation in a long cylindrical channel. A steadily propagating planar flame exists for heat losses below a critical value. It is stable provided that the Lewis number and the volumetric heat loss coefficient are sufficiently small. At critical values of these parameters, bifurcated states, corresponding to time-periodic pulsating cellular flames, emanate from the steadily propagating solution. The authors analyze the problem in a neighborhood of a multiple primary bifurcation point. By varying the radius of the channel, they split the multiple bifurcation point and show that various types of stable periodic and quasi-periodic pulsating flames can arise as secondary, tertiary, and quaternary bifurcations. Their analysis describes several types of spinning and pulsating flame propagation which have been experimentally observed in nonadiabatic flames, and also describes additional quasi-periodic modes of burning which have yet to be documented experimentally

[en] A study has been carried out for laminar heat transfer in a tube subjected to a streamwise variation of the convective coefficient. The heat exchange section of the tube is divided in two parts. The first part (the heated region) is subjected to a uniform wall heat flux, whereas the second part (the cooled region) is fitted with an array of external annular fins. In this paper, the influence of axial wall conduction and axial fluid conduction has been examined in detail, indicating that both mechanism have a pronounced effect on the heat transfer characteristics of the fluid flow. (author)

[en] Heat transfer from a heated plate to circular air jets issuing from a square array of nozzles is measured by means of an Infrared Scanning Radiometer (IRSR). Experimental tests are performed for different values of jet Reynolds number, nozzle-to-plate distance, nozzle-to-nozzle spacing and nozzle diameter. The two-dimensional character of IRSR and the possibility of processing digital thermal images on a computer allow to obtain surface temperature maps as well as to compute local heat transfer coefficient profiles. (author)

[en] The problem of heat transfer in longitudinal fins with the main geometries used in equipaments of heat transfer by convection is analyzed. The equation of energy is solved analytically of several geometries fins, with unidimensional formulation, through the use of the convective heat transfer coefficient. The problem of fin optimization is approached analytically yielding the parameters which allow the maximum heat transfer for each particular material waste in the fin. The use of the insulated tip model suggests the use of fins and its optimization for any Biot number of the fin. The use of the convective tip model allows us to determine when is vantageous or disadvantageous to use fins and when fin optimization is possible according to the value of the Biot number and to a convection parameter on the fin tip. (Author)

[en] In this paper we give thermal-hydraulic models of pebble bed. A code, THPBHR, developed by the present authors is briefly introduced. Radial cooling and poloidal direct cooling methods are given and discussed. The thermal-hydraulic calculations of them by THPBHR are given. Calculation results show that both cooling methods can meet the demands of blanket design. The heat transfer in the beds with poloidal cooling is better than with radial cooling, but the pressure drop is higher. The non-uniformity of outlet temperature is much higher with poloidal cooling. (orig.)

[en] Heat transfer in fusion reactor blankets using particle beds depends on both the bulk effective thermal conductivity and the thermal conductance in the near-wall region of the bed. Especially for metallic beds, which exhibit high solid-to-gas thermal conductivity ratios, there are several parameters which can strongly affect heat transfer. These include gas composition and pressure, particle packing factor, type of bed (single or binary sizes), surface conditions, and the state of stress in the bed. Because of the strong dependence of heat transfer on the contact area between pebbles and walls, the thermal and mechanical behavior in the near-wall region can be strongly interrelated. In this work, the authors describe a new model for wall-bed thermal conductance which includes the effect of decreased porosity in the near-wall region, thermophysical properties of both the particles and the wall, and the effect of forces which can occur within the bed under fusion-relevant blanket conditions. The internal stress state in particle beds is difficult to predict due to stress concentrations at the particle contact points which can lead to inelastic deformations, and due to the complex packing arrangements which may occur

[en] Short communication

[en] The present book describes a method for calculating the strength of the most common types of heat exchanger with a straight bundle of tubes, whose components are stressed by the process-dependent excess pressures in the space inside and the space around the tubes as well as by the different longitudinal deformation of the tube and the shell around the tubes due to the temperature difference between the two flow media. In general, these heat exchangers consist of the bundle of tubes with the two tube plates, the shell around the tubes which is either flanged or directly welded to the tube plates, the distributors which are also flanged or welded to the tube plates, and the standpipes. Heat exchangers with a submersible bottom usually also have a flange on the submersible plate and the plate bottom commonly used in this construction. The parts of the distributors which lie in the unperturbed region, the standpipes, the flanges on the tube plates, and the plate bottom on the submersible bottom all can be reliably and efficiently calculated using the formulae given in the AD leaflets and are therefore not considered in the calculation method described here. This book limits itself to the calculation of the tube bundle and the tube plates as well as of all structural components influenced by the deformation of the tube bundle and the tube plates. (orig./TK)

No abstract available