Thermoelastic plastic deformation of a functional gradient material under conditions of central symmetry

В работе рассматривается ряд краевых задач теории термоупругопластического деформирования материала в условиях тороидальной симметрии. Рассмотрен процесс упругой разгрузки предварительно нагретого объекта. Рассчитаны поля остаточных напряжений и перемещений. Получены точные формулы для аналитического решения поставленной краевой задачи A number of boundary value problems of the theory of thermoelastoplastic deformation of a material under conditions of toroidal symmetry are presented. The process of elastic unloading of a heated object is considered. The fields of residual stresses and displacements are calculated. Exact formulas are obtained for the analytical solution of the stated boundary value problem.

NATURAL CONVECTION IN A MICROPOLAR NANOFLUID FILLED OPEN RECTANGULAR ENCLOSURE EMBEDDED WITH A HEATED OBJECT OF DIFFERENT GEOMETRIES

A numerical investigation has been performed to analyze heat convection through a micropolar nanofluid in an open rectangular enclosure. It embedded the inner heated object of different geometries and finite heat source length on the bottom wall with uniform heat flux. The remaining portion of the wall containing heat source and all the remaining walls are assumed as adiabatic except the top wall. Successive over-relaxation (SOR) method coupled with Gauss-Seidel iteration technique are employed in order to numerically tackled the nonlinear model momentum and energy equations. The effect of the calibrated parameters such as Rayleigh number, length of the wall heat source, the geometry of the inner block, vortex viscosity parameter, the type of nanoparticles, and the concentration of nanoparticles on the flow and thermal performance is studied. The computed results show that increasing in the Rayleigh number and the concentration of nanoparticles have a positive effect on Nusselt number whereas increasing in wall heat source length and vortex viscosity attenuates the Nusselt number. Also, the geometry of the inner block has effect in the flow pattern and the temperature distribution.

Impact of Surface Treatment of Historic Bricks on the Process of Water Vapours Diffusion

The article is dealing with impact of selected types of surface finish of historic bricks on their diffusion properties, i.e. on the process of their spontaneous self-drying. Within the pilot experiment was monitored diffusion flow of water vapours going from humid brick fragment through its surface finish to the surrounding environment. Brick fragment was saturated with water to a degree usually corresponding to common humidity of uninsulated underground brickwork of historic buildings. Surrounding environment had parameters of common heated object for residential or administrative purpose or an object for storage of things sensitive to impact of high relative air humidity. Test results proved that any surface finish of the brickwork, even its hydropohobisation is significantly slowing down process of drying of the masonry compared to the speed of drying of the untreated brickwork. It is evident from the course of lines of diffusion flows that the process of water vapours diffusion is most intense at the beginning of the period (about 5 to 10 days) and after this period the diffusion flow speed goes to a long-term stabilisation of diffusion flow speed, in such a way that its course is in average corresponding to linear functional dependence on time. In conclusion of the article we introduce on practical example calculation of real time of drying up of the masonry in historic building selected space flooded with flood water where is now running process of natural drying without additional humidity sources.

Improved localisation and discrimination of heat emitting household objects with the artificial vision therapy system by integration with thermal sensor

AimTo demonstrate the potential clinically meaningful benefits of a thermal camera integrated with the Argus II, an artificial vision therapy system, for assisting Argus II users in localising and discriminating heat-emitting objects.MethodsSeven blind patients implanted with Argus II retinal prosthesis participated in the study. Two tasks were investigated: (1) localising up to three heat-emitting objects by indicating the location of the objects and (2) discriminating a specific heated object out of three presented on a table. Heat-emitting objects placed on a table included a toaster, a flat iron, an electric kettle, a heating pad and a mug of hot water. Subjects completed the two tasks using the unmodified Argus II system with a visible-light camera and the thermal camera-integrated Argus II.ResultsSubjects more accurately localised heated objects displayed on a table (p=0.011) and discriminated a specific type of object (p=0.005) presented with the thermal camera integrated with the Argus II versus the unmodified Argus II camera.ConclusionsThe thermal camera integrated with the artificial vision therapy system helps users to locate and differentiate heat-emitting objects more precisely than a visible light sensor. The integration of the thermal camera with the Argus II may have significant benefits in patients’ daily life.

Simplified simulation technique of rotating, induction heated, calender rolls for study of temperature field control

Predictive computer simulation of the temperature field control system of an induction heated object encounters difficulties associated with the nonlinearityof systemon the one hand, and the time of calculation on the other hand, during numerical analysis of the magnetothermal field of the object, especially in 3D. The paper presents a methodology for the fast simulation of temperature field for a completed induction heating system of calender rolls. The method of 3D calculations of rotating calender rolls with a moving web of wet paper can be connected easily with a simulation of the temperature field controller, for simulation of complex control systems.

FREE CONVECTIVE HEAT TRANSFER FROM AN OBJECT AT LOW RAYLEIGH NUMBER

Free convective heat transfer from a heated object in very large enclosure is investigated in thepresent work. Numerical investigation is conducted to explore the fluid flow and heat transfer behavior in thevery large enclosure with heated object at the bottom. Heat is released from the heated object by naturalconvection. Entrainment is coming from the surrounding. The two dimensional Continuity, Navier-Stokesequation and Energy equation have been solved by the finite difference method. Uniform grids are used in theaxial direction and non-uniform grids are specified in the vertical direction. The differential equations arediscretized using Central difference method and Forward difference method. The discritized equations withproper boundary conditions are sought by SUR method. It has been done on the basis of stream function andvorticity formulation. The flow field is investigated for fluid flowing with Rayleigh numbers in the range of 1.0 ?Ra ? 1.0×103 and Pr=0.71. It is observed that the distortion of flow started at Rayleigh number Ra=10. It isobserved that the average heat transfer remains constant for higher values of Reyleigh number and heatingefficiency varies with Ra upto the value of Ra=35 and beyond this value heating efficiency remains constant.DOI: http://dx.doi.org/10.3329/jme.v43i1.15775

Heating system with vapour compressor heat pump and vertical U-tube ground heat exchanger

Heating system with vapour compressor heat pump and vertical U-tube ground heat exchangerIn the paper a heating system with a vapour compressor heat pump and vertical U-tube ground heat exchanger for small residential house is considered. A mathematical model of the system: heated object - vapour compressor heat pump - ground heat exchanger is presented shortly. The system investigated is equipped, apart from the heat pump, with the additional conventional source of heat. The processes taking place in the analyzed system are of unsteady character. The model consists of three elements; the first containing the calculation model of the space to be heated, the second - the vertical U-tube ground heat exchanger with the adjoining area of the ground. The equations for the elements of vapour compressor heat pump form the third element of the general model. The period of one heating season is taken into consideration. The results of calculations for two variants of the ground heat exchanger are presented and compared. These results concern variable in time parameters at particular points of the system and energy consumption during the heating season. This paper presents the mutual influence of the ground heat exchanger subsystem, elements of vapour compressor heat pump and heated space.