Mashekova, AigerimZhao, YongNg, Eddie Y. K.Zarikas, Vasilios...
18页
查看更多>>摘要：Breast cancer is one of the most common and deadly diseases in women, which can also affect men. Early detection and treatment of this disease can increase the chances of cure. Currently, there are many different approaches to breast cancer screening, each of which has its own advantages and disadvantages. Thermography is one of those breast cancer screening methods that is considered safe and non-invasive. The approach with new image processing and intelligent classification techniques has gained renewed interest. The non-contact tech-nology, which is relatively inexpensive, has great potential for integration with the Internet for early detection of breast cancer through mass screening and subsequent continuous monitoring of suspected patients. This paper presents a comprehensive review of previous studies conducted at the intersection of thermography, numerical simulation, and artificial intelligence that can improve early detection of breast cancer.
查看更多>>摘要：Electrical motors are one of the most utilised items employed by plants. A key design issue is removing unwanted heat caused by winding and core losses in the motor. This paper investigates the incorporation of a new technology, Thermoelectric Electric Coolers (TEC) to improve the heat flow from the core and casing to the surrounding air. Three test configurations are used. The first one is the heat sink system because of its simple construction arrangement capable of being simply adapted to a motors external casing. The second one is the heat displacement system "heat pipes" because of very large number of motors mounted in confined areas and the third one is the water-cooled heat sink arrangement extensively used in critical areas. The aim of this study is to evaluate the incorporation of TEC to each of these systems to remove unwanted heat more than the current systems. Experimental results show that the addition of the above systems with TEC reduce slot temperatures by 14.9%, 12%, and 18.96%, respectively. The reduction in insulation temperatures will result in increased motor insulation life or allow the motors to be overloaded (increased output) without exceeding insulation thermal ratings.
查看更多>>摘要：Metallic tailoring of oxygen carrier plays a crucial role within chemical looping combustion (CLC) applications, which can be correlated to the redox reaction enhancement and sustainability. Such attributes arise from the electric valence of the material constituents, which can bring about superior oxygen vacancy and structural stability. In the concurrent study, the role of electronegativity of the bimetallic carriers upon CLC performance was scrutinized based on various bimetallic metal oxides composition. Two metallic systems were examined in the current study: Iron based oxides and copper-based oxides, where the secondary metallic element within each of the examined oxide carrier is composed of one of the 5 metallic elements, predefined for the purpose of electronegativity variation. The secondary metallic element include: Calcium, Lanthanum, Magnesium, Manganese, and Chromium. Several gas byproducts were monitored during the course of the CLC reaction, via mass spectrometer, in order to quantify the variations incurred as a result of different metallic composition inclusion. Additionally, electron microscopic techniques, such as the SEM, were utilized in the study, so as to visualize the structural alteration of sintered materials. The experimental results indicate a higher reactivity with the fuel at a higher electronegativity difference within the bimetallic structure, in the case of iron-based oxide system. Also, copper-based oxide system was associated with higher carbon dioxide production with higher selectivity, relative to iron-based oxide systems.
查看更多>>摘要：Ice slurry has been put into use as secondary refrigerant in many industrial fields due to its promising characteristics. But the complex flow properties of ice slurry flow have brought significant difficulties to transport processes. In this paper, a CFD-PBM coupled model has been employed to investigate the flow characteristics of the ice slurry flow in horizontal various elbow pipes. The ice kinetics processes (growth, aggregation, and breakage) are all taken into consideration. The results show that different elbow angles affect the pressure, velocity, ice size and uniformity of ice slurry when flowing across the elbow. Longer length and higher bending angle of elbow make boundary layer separation and secondary flow more obvious. For the elbow angle less than 90 degrees, the redistribution of pressure and velocity enhance the aggregation process at pipe section center at elbow outlet sections, which results in the growth of ice particles. The inlet velocity, ice packing fraction (IPF) and elbow angle both influence the uniformity of ice slurry. Inlet velocity has positive correlation, while IPF and elbow angle have reverse effect. In order to improve the efficiency of ice slurry transport process and avoid the ice blockage, higher velocity, lower IPF and suitable elbow angle (less than 90 degrees are suggested.
查看更多>>摘要：The present study numerically investigates the cooling performance of portable cold storage boxes using phase change material (PCM) for safe and secure transportation of vaccines under a controlled temperature range of -55 degrees C to -40 degrees C at different ambient conditions. A suitable PCM (SP-50) is identified to comply with the temperature requirement of the cold storage box and a comparative study has been performed between a cuboid and cylindrical configuration having the same volume of the box and PCM. Temporal variation of temperature and liquid fraction during phase change of PCM are demonstrated with the help of CFD analysis. The inside temperature of the cylindrical configuration of the box is found to be 4.03% lower than the cuboid box after 17hrs of cooling duration for an ambient temperature of 45 degrees C. Cooling efficiency and cooling duration of the cylindrical configuration is 8.7% and 20.4% more than the cuboid one respectively at the ambient temperature of 30 degrees C. The relative dominance between convection and radiation heat transfer is evaluated at different surfaces for both configurations.
Delgado Maldonado, Paul AdrianRibeiro da Silva, Raquel da CunhaSalinas, Carlos T.Biglia, Felipe Merces...
11页
查看更多>>摘要：Frost formation is an undesirable phenomenon in heat exchangers, where a thin layer of frost forms, negatively influencing the performance and operation of the equipment. The frost layer increases the thermal resistance between the air flow and the cold surfaces in evaporators, which reduces the heat transfer rate and decreases the thermal efficiency. In the present study, the phenomenon of frost growth on a triangular array of slender vertical tubes was investigated experimentally in a wind tunnel. Fast CCD cameras were used for frost thickness measurement. A numerical investigation was conducted to simulate the frost thickness growth on the cold tube surface. Volumetric mean approach for frost formation modelling was applied and a modified formulation for calculation of the local Nusselt number in the vertical slender tube case was proposed. The numerical predictions showed a reasonably good agreement in relation to the mean values of the frost thickness measured in experimental tests up to the range of 5,000 to 6,000 s of simulation. Afterwards, in model predictions, the frost growth is bigger than the experimental results in the range of 14% to 33% higher in relation to mean values.
查看更多>>摘要：Improving the heat transfer characteristics of materials can be accomplished by increasing the surface area. This surface roughening can be accomplished efficiently and directly using pulsed-laser processing. Here, laser processing of copper using a picosecond laser pulse technique produced mound-like structures, with surface morphologies and subsurface microstructures dependent on laser pulse count, with higher pulse counts producing a unique layering of Cu and Cu2O in the mounds. Processing in ambient air resulted in the formation of surface oxides. The presence of oxides deleteriously influenced the heat transfer characteristics, with a lower heat transfer coefficient compared to unprocessed Cu. To remove the oxidation, the laser-processed copper was subjected to different acid treatments. It was found that treatment using citric acid resulted in efficient and effective removal of oxides both surface and subsurface. For low pulse count samples, an improvement in the heat transfer characteristics was observed after oxide removal, and outperformed the polished reference sample at heat fluxes above approximately 90 W/cm(2). However, the removal of oxides using citric acid was found to actually decrease heat transfer characteristics for high pulse count samples with the onion-like subsurface layers, as oxide removal left behind voids in the structure which were detrimental to heat transfer. Thus, optimized laser surface processing which avoids subsurface onion-like layer formation enhances heat transfer performance.
查看更多>>摘要：This paper presents a review on heat transfer coefficient and pressure drop during condensation and boiling in helically coiled tubes. The geometric parameters such as coil diameter, coil pitch and operating parameters containing saturation temperature, system pressure, mass flux, heat flux and vapor quality have significant effects on the heat transfer characteristics. The frictional pressure drop during flow boiling increases with increasing vapor quality and mass flux, and decreases with increasing system pressure. Also, the effect of the curvature on the two-phase frictional multiplier is negligible. The frictional pressure drop in condensation increased with increasing average vapor quality and mass flux, and decreased with increasing saturation temperature. According to the results reported, heat flux had little effect on the pressure drop during condensation. Flow boiling heat transfer coefficient in helical coils of large diameter showed the similar characteristics and trend with the straight tube as the system pressure decreased. Lockhart-Martinelli parameter was generally preferred to be used by the authors as a function in the correlations to predict flow boiling heat transfer coefficient. There was a decrease in the average Nusselt number with increasing heat flux for the constant Dean number during condensation. This reduction in the average Nusselt number indicated that the turbulence effect created by the secondary flow in the helically coiled tubes eliminated the effects caused by the difference in density. The correlations used for determination of Nusselt number and pressure drop in helical coils with their major findings are presented in details.
de Moura, Ermerson F.Henriques, Izabela B.Ribeiro, Guilherme B.
14页
查看更多>>摘要：In recent years, the interest of space agencies and private companies in space exploration has increased, mainly in deep space missions. This type of mission poses great challenges due to the high energy level demanded from the power systems, requiring a more efficient and compact energy conversion system. Thus, this work carried out a finite-time thermodynamic model and exergy analysis of a Stirling cycle for nuclear space power generation. The thermodynamic model was coupled to a simple dynamic Stirling engine model and takes into account several aspects such as the thermal losses between the hot and cold side of the Stirling cycle, finite-time regeneration, temperature drop along heat pipes, and variable compression ratio. The system performance and component irreversibilities were evaluated by varying the nuclear core temperature and the cold side temperature of the cycle. Then, the figure of merit mass per power output (kg.kW(-1)) of the energy conversion system was computed, enabling the model to find temperature conditions for a system that aligns high efficiency and compactness. The results showed that the component with the greatest irreversibility is the reactor core with a value of 496.14 kJ, representing 68.18% of the total irreversibility. The exergy analysis showed that only 5.15% of the total exergy is used for power generation and 24.33% is rejected to space. Moreover, the cold side temperature of 352 K provided the system with the lowest value of mass per power output (87.69 kg.kW(-1)).
查看更多>>摘要：The Transcritical Regenerative Series Two-stage Organic Rankine Cycle (TR-STORC) was shown to deliver improved performance than Series Two-stage ORC (STORC) and single-stage ORC for dual-source heat recovery applications. However, TR-STORC utilizes partial evaporation for regeneration which requires precise control of two-phase flows. In real-time operations involving dual/multiple heat sources, this is difficult to achieve due to fluctuating heat inputs, leading to liquid carryover and subsequent corrosion of turbine blades. This study explores a novel Transcritical Ejector Regenerative STORC (TER-STORC), which replaces the need for two phase flows with a avapor-vapor regeneration via an ejector operating entirely with fully evaporated vapor (FE mode). Partial evaporation (PE) mode of TER-STORC requiring two-phase flows is also analyzed for comparison. Results indicate that the FE mode of TER-STORC can achieve performance comparable to PE mode and TR-STORC. FE mode of ejector operation is less sensitive to variations in ejector pressure drop than PE mode while delivering 0.2-4% lower power outputs with lower heat exchanger requirements than TR-STORC by up to 18%.At the engine design point, only a 2% drop in power output is seen for FE mode compared to TR-STORC. TER-STORC presents a robust system with reduced complexity for multisource heat recovery.
NSTL
Elsevier