Characterising Modal Behaviour of a Cantilever Beam at Different Heating Rates for Isothermal Conditions

The effect of temperature on structural response is a concern in engineering applications. The literature has highlighted that applied temperature loads change the system vibration behaviour. However, there is limited information available about temperature impacting the dynamic response. This paper investigated the heating rates effects on modal parameters for both with crack and without crack conditions in a cantilever beam. A beam subjected to three heating rates was considered: 2, 5, and 8 °C/min. The first one was assumed as a slow heating rate while the others were assumed as moderate and high, respectively. This controlled rate of heating was achieved by using a proportional-integral-derivative (PID) temperature controller. The results showed that heating at different rates has little impact on modal parameters. While this effect is minimal at lower temperatures and more evident at higher temperatures. The results of temperature ramped at 2, 5, and 8 °C/min were compared with the numerical and analytical results only for all the isothermal conditions. It was observed that the beam natural frequency and its modal amplitude decrease with the increase in temperatures and crack depths. Therefore, it is concluded that the rate of heating can make a slight impact on the dynamics response of any mechanical system.

SPECIFIC OF INTERACTION OF THE MACROPARTICLES WITH THE PLASMA-BEAM SYSTEMS

The presented paper summarizes the results of the last works of the authors on modeling the processes of heating and evaporation of macroparticles in a plasma-beam system. The emphasis are made on the influence of the parameters of the plasma as well as the electron beam introduced into the plasma on these processes. A detailed analysis of the effects that accelerate or slow down the rate of heating and evaporation of macroparticles has been performed.

Influence of aluminium content on the microstructure and densification of spark plasma sintered nickel aluminium bronze

In this study, nickel aluminium bronze alloys (NAB) with appreciable densification and improved microhardness was consolidated via spark plasma sintering technique. The NAB alloy was synthesized from starting elemental powders comprised nickel (4 wt.%), aluminium (6, 8 & 10 wt.%) and copper using dry milling technique. Starting powders were homogeneously milled using gentle ball mill for 8 h at a speed of 150 rpm and a BPR of 10:1. Subsequently, the milled powders were consolidated using the spark plasma sintering technique at 750 °C under a compressive pressure of 50 MPa and rate of heating (100 °C/min). Furthermore, the powders and sintered alloys were characterized using SEM and XRD to ascertain the microstructural and phase evolutions during the synthesis of the NAB. The density and microhardness of the alloys were further investigated to ascertain the integrity of the sintered alloys. The results indicated that the increase in aluminium content resulted in the formation of intermetallic and beta phases on the alloy after sintering and the microhardness of the alloys improved with the increase in aluminium content.

Thermodynamic Analysis on a Heat-Power Decoupling System Integrated With Absorption Heat Pump

Because of the continuous expanding of the district heating, the heating load of combined heat and power (CHP) plants increases year by year. The minimum power load of CHP plant increases with the heating load due to the heat-power coupling mechanism. Therefore, heat-power decoupling is necessary to improve the operation flexibility for CHP units. Integrating the absorption heat pump (AHP) is an effective method to realize the heat-power decoupling. In this study, a 330MW CHP unit model and AHP model have been developed and validated. The performance of the heat-power decoupling and energy saving performance has been investigated by comparing the thermodynamic performance indicators. Results show that, the proposed system can increase the maximum heating load and decrease the power generation when the primary network return temperature is decreased. When the heating steam extraction is kept constant, with the increase of the primary network return water temperature, the heat generation efficiency and the standard coal consumption rate of heating increases, the coal consumption rate of power generation and the heating efficiency decreases. And the primary network return water temperature increases from 40 °C to 70 °C, the coal consumption rate of power generation decreases by 4.3 g/kWh, and the coal consumption rate of heating increases by 0.67 kg/GJ.

Applicability of heat-exchanger theory to estimate heat losses to surrounding formations in a thermal flood

Heat losses to cap and base rocks undermine the performance of a thermal flood. As a contribution to this subject, this paper investigates the applicability of the principles of heat exchanger to characterise heat losses between a petroleum reservoir and the adjacent geologic systems. The reservoir-boundary interface is conceptualised as a conductive wall through which the reservoir and adjacent formations exchange heat, but not mass. For a conduction-dominated process, the heat-transport equations are formulated and solved for both adiabatic and non-adiabatic conditions. Simulations performed on a field-scale example show that the rate of heating a petroleum reservoir is sensitive to the type of fluids saturating the adjoining geologic systems, as well as the characteristics of the cap and base rocks of the subject reservoir. Adiabatic and semi-infinite reservoir assumptions are found to be poor approximations for the examples presented. Validation of the proposed model against an existing model was satisfactory; however, remaining differences in performances are rationalised. Besides demonstrating the applicability of heat-exchanger theory to describe thermal losses in petroleum reservoirs, a novelty of this work is that it explicitly accounts for the effects of the reservoir-overburden and reservoir-underburden interfaces, as well as the characteristics of the fluid in the adjacent strata on reservoir heating. These and other findings should aid the design and management of thermal floods.

Modeling of Materials Heating on Solar Furnace and Cooling of Melt

The possibilities of calculating the rate of heating and cooling of molten materials on the example of pyroxene rocks under the influence of concentrated solar radiation in the Big Solar Furnace are shown. The dependences of the microstructure of the material obtained from the cooled melt on the cooling rate of the melt are analyzed. It is shown that a different method of cooling the melt can achieve different cooling rates: 102 ; 103 and 104 deg/s.

The Effects of Dynamic Transformation on the Formation of Pt-M (M = Ni, Fe) Nanocrystals

ABSTRACTIn the synthesis of metallic nanocrystals (NCs) using a high-temperature colloidal approach, the competition between deposition and diffusion of “free atom (or clusters)” plays an important role as it can direct the morphology of NCs during their evolution. This competition is closely associated with some dynamic conditions such as heat and mass transfer. Stirring speed and ramp rate of heating are two factors that greatly impact the heat and mass transfer processes and consequently determine the morphology of the products but rarely discussed in most synthetic protocols. Herein, we study the syntheses of Pt-M (M = Ni, Fe) NCs as model reactions, showing that a low stirring speed and high ramp rate of heating result in ununiform pod-like NCs, whereas the inverse conditions promote NCs in a uniform shape. This observation can be plausibly explained using a competition mechanism between the deposition and diffusion of the newly reduced atoms during a stage of the NC’s growth.

Experimental Studies of Heat and Moisture Exchange in the Process of Convective Drying of Thin Wet Materials

New ways of experimental data processing by generalized complex variables that are characteristic of the drying process are presented. The authors presented the results of a study of heat and moisture exchange in the convective drying of thin flat moist capillary-porous materials. As a result of the processing of the experimental data, equations were obtained for determining the densities of heat fluxes, average integral temperatures, drying time and moisture evaporation rate in the second drying period. The relationship between the densities of heat fluxes in the first and second periods and the temperature change in the second period is revealed. The dependence for calculating the temperature of the material in the period of the falling drying rate taking into account the heat that is expended to heat the wet body is presented. The equations for determining the temperature in the second period by the temperature coefficient of drying, the rate of heating of the wet material and the rate of heating of the wet body are presented as well. An equation for determining the drying time by the value of the rate of loss of moisture content of the material is given. A mathematical expression for calculating the intensity of moisture evaporation in the first and second drying periods depending on the ratio of moisture content in the first period and the current in the second moisture content one is set. The conditions of a regular regime for heat and moisture exchange for a second drying period are adduced. The authors consider the possibility of determining the rate of heating of wet material by the heating rate using the graphical differentiation of the temperature function, which is described by the curve, as a function of time in the second drying period. The problems of using the methods of the theory of the regular regime for heating wet bodies during the investigation of the drying process are considered. The formulas for determining the rate of heating of the body and the rate of loss of moisture content are given. The accuracy of the experimental data processing and the reliability of the experimental equations obtained for all the materials under study are verified. As a result of the research, all the basic kinetic characteristics necessary for the calculation of heat and moisture exchange in the drying process have been determined.

Hydrogen Behavior in NdRh3-Based Hydrides

Samples of desorbed NdRh3-based hydrides have been investigated by the X-ray diffraction method. X-ray data analysis showed that the samples contain two phases with hexagonal and cubic lattices. It was revealed that proportion of these phases in the samples depends on the rate of heating before the hydrogen desorption. At high rates of the heating in the desorbed samples amount of the phase with cubic lattice increased. This behaviour of the hydrogen in hydrides can be explained by the difference in the diffusion of disordered and ordered hydrogen atoms.