Experimental Investigation Of Changes Research Articles

Experimental and numerical study on heat transfer performance of wavy channel heat sink with varying channel heights

Today, electronic device cooling is a significant challenge that has been addressed by utilizing heat sinks with various designs. The numerical and experimental investigation of changes in the wavy channel heat sink height is carried out to improve the performance. As a novelty, the heat sink's height remains constant to assess how open space above the channels affects the performance. The work aims to assess the impact of various heat fluxes and flow rates on temperature, Nu number, flow, and velocity; meanwhile conducting a non-dimensional analysis. At the flowrate of 6.94cm3/s, once the channel's height was reduced to 10 mm, the highest temperature decreased by 7.84%, while by the decrement of height to 7 and 4 mm, it witnessed 14.14% and 23.81% rises, respectively. The local Nusselt number for 10 mm height and 19.56cm3/s flow ranges between 127.47 and 106.53 in 5.17 W/cm2 heat flux. The flow with higher dimensionless velocity is dispersed throughout the open area above the heat sink, once the 12.7 mm height is reduced to 10 mm. The performance evaluation criterion of the system is determined by considering the ratio between Nu number and friction factor, which is obtained between 1.08 and 1.22 for 10 mm channel height. Thus, the 10 mm wavy channel height can be suggested for cooling electrical equipment.

Experimental investigation of change in performance parameters on cooling of lithium‐ion battery pack using nanofluids

AbstractElectric vehicles surged into the automobile industry due to increasing emissions and future extinction of fossil fuels which resulted due to their unforeseen utilization all over the globe. Battery is important components for manufacturing of electric vehicles (EVs). Currently lithium‐ion (Li‐ion) cells are the most advanced and efficient cell technology developed till date. These cells work well within an operating temperature range of 15° C to 35°C. Thus, many battery cooling techniques were developed such as air, liquid, phase change material (PCM) and heat pipe based cooling system. Liquid cooling was found to be the most efficient, adoptable and convenient system used in EVs. The current paper focuses on development of an active indirect liquid cooling system using nanofluids as coolant. Different performance parameters such as mass flow rate, nanoparticle concentration and maximum temperature of battery pack were varied and simulation results were validated using experimental results. The results concluded that nanofluids show improved and enhanced cooling as in comparison with other coolants such as water and ethylene glycol. Al2O3‐water nanofluid is the most preferable to use in EVs as coolants due to its efficient cooling, low cost and environmental friendly nature. On increasing the mass flow rate of the coolants, flowing into the cooling tube increases the cooling performance and reduces the temperature of battery pack within the battery operating zone. The cooling performance using nanofluids increased by 40% as in comparison with water and ethylene glycol as coolants when tested experimentally.

Experimental investigation of changes in petrophysical properties and structural deformation of carbonate reservoirs

Abstract To examine the effect of pressure on pore structure and petrophysical properties of carbonate rock, the porosity, permeability, CT scanning, SEM and elastic wave velocity of two carbonate core plug samples from an oilfield in Southwest Iran were analyzed under cyclic pressure. One of the plugs was calcite and the other was dolomite with anhydrite nodules. The cyclic pressure exerted on the samples increased from 13.79 MPa to 27.58 MPa in six steps, and the variations in petrophysical properties of the two samples at different pressure loading and unloading steps were counted and analyzed. The results show that the calcite sample decreases in porosity and permeability with the increase of pressure, which is consistent with the results from compression and shear wave velocity tests. In the dolomite sample, the decreasing trend was not observed; fluctuations of compressive and shear velocities were observed during the loading stage, which may be due to different geometries of the pores and the porosity variation in the sample. Understanding the variation of carbonate petrophysical properties with pressure is helpful for optimizing reservoir development scheme.

The analysis of acoustic emission signals detected during the loading of cement-based materials

The article deals with the experimental investigation of changes in the internal structure of materials subjected to loading. The main aim of the experiments was to identify crack formation and their propagation within the elastic part of the stress-strain diagram and define its significance and influence on the overall failure behaviour of specimens under loading. The specimens' overall behaviour was monitored using the non-destructive testing method of acoustic emission (AE). Three different cement-based composites, which differed mainly in the maximum value of the expected static modulus of elasticity, were manufactured for the purpose of experiments. Based on the results, it can be stated that the increased number of micro-cracks in the specimens' internal structure is reflected in an increased number of AE events. The specimens with a lower value of the static modulus of elasticity showed higher AE activity during all the periods of loading being investigated. In addition, the AE energy released due to the formation of micro-cracks was the highest in specimens with a lower value of the modulus of elasticity.

Experimental Investigation of Change in the Contrast between Flotation Properties of Calcic Minerals

The interaction of fatty acid sodium oleate collector and higher isoalcohols in a liquid phase and on surface of separated scheelite and calcite minerals is investigated. The research findings on monophase calcite and scheelite are presented with their X-ray patterns and IR spectra. The experimental data show the contribution of the intermolecular interactions in combinations of differently ionizable oxyhydryl collectors to the increased contrast between floatabilities of scheelite and calcite. The IR spectroscopy states that the maximum strength of the intermolecular hydrogen bridges between oleate and isoalcohols in the range of 300–3200 cm–1 fits with the molar ratio of 2. Isoalcohols in the surface layer of scheelite neutralize hydrophilic behavior of oleate micellas by means of generation of heteromolecular associates through hydrogen bridges, loosen the hydrated layer and enhance air bubble attachability; adhesion of isoalcohol drops improves floatability of scheelite; higher isoalcohols reduce flotation activity of calcite. The maximum contrast in flotation properties is observed in slimes at respective oleate concentrations fitting the micelle formation process.

Experimental investigation of changes in petrophysical properties during CO2 injection into dolomite-rich rocks

Carbon dioxide may be injected into an underground geological structure for mere geo-sequestration purposes or as a means of enhanced hydrocarbon recovery. During such an operation, CO2 is expected to dissolve in the in-situ fluids (primarily consisting of brine) generating a reactive in-situ solute (i.e. carbonated brine). Subsequently, a series of consecutive chemical reactions may occur between the solute and the host rock. While these reactions are generally known from a qualitative perspective, to what extent they may impact on the host formation’s petrophysical properties requires extensive evaluation on a case by case basis. Due to the presence of highly reactive minerals in their composition, carbonate rocks (e.g. dolostone) present a more complex system to evaluate in terms of the above mentioned chemical reactions.This experimental study has been carried out to evaluate changes in the petrophysical properties of a number of heterogeneous dolostone samples after undergoing carbonated brine flooding under in-situ reservoir conditions. In this study, the core-flood experiments are complemented by pre- and post-flood porosity, permeability and NMR (nuclear magnetic resonance) measurements, X-ray CT scanning and X-ray Diffraction (XRD) and Energy-Dispersive X-ray (EDX) analysis. Overall, a slight increase in the porosity was observed in most samples, most likely, caused by the dissolution of dolomite (CaMg(CO3)2), calcite (CaCO3) and/or anhydrite (CaSO4). The results also show an increase in the permeability of some samples which again could be attributed to dissolution of the minerals. The X-ray CT images show signs of excessive dissolution of minerals and the creation of dissolution patterns (i.e. wormholes). On the other hand, reductions in permeability and porosity by 57% and 12%, respectively, were also observed in a sample. This is believed to be due to the combined effects of the mineral precipitation and mechanical compaction mechanisms dominating over the mineral dissolution. A small shift in the pore size distribution of the samples towards smaller pore sizes was also observed which is believed to have been caused by mechanical compaction.

Experimental Investigation of Change in the Contrast between Flotation Properties of Calcic Minerals

Experimental Investigation of Change in the Contrast between Flotation Properties of Calcic Minerals

Experimental investigation of changes in methane adsorption of bitumen-free Woodford Shale with thermal maturation induced by hydrous pyrolysis

This study quantifies the effects of organic-matter (OM) thermal maturity on methane (CH4) sorption, on the basis of five samples that were artificially matured through hydrous pyrolysis achieved by heating samples of immature Woodford Shale under five different time–temperature conditions. CH4-sorption isotherms at 35 °C, 50 °C, and 65 °C, and pressures up to 14 MPa on dry, solvent-extracted samples of the artificially matured Woodford Shale were measured. The results showed that CH4-sorption capacity, normalized to TOC, varied with thermal maturity, following1 the trend: maximum oil (367 °C) > oil cracking (400 °C) > maximum bitumen/early oil (333 °C) > early bitumen (300 °C) > immature stage (130 °C). The Langmuir constants for the samples at maximum-oil and oil-cracking stages are larger than the values for the bitumen-forming stages.The total pore volume, determined by N2 physisorption at 77 K, increases with increased maturation: mesopores, 2–50 nm in width, were created during the thermal conversion of organic-matter and a dramatic increase in porosity appeared when maximum-bitumen and maximum-oil generation stages were reached. A linear relationship between thermal maturity and Brunauer–Emmett–Teller (BET) surface area suggests that the observed increase in CH4-sorption capacity may be the result of mesopores produced during OM conversion. No obvious difference is observed in pore-size distribution and pore volume for samples with pores <2.0 nm with the increase of thermal maturity based on CO2 physisorption at 273 K.The isosteric heat of adsorption and the standard entropy for artificially matured samples ranged from 17.9 kJ mol−1 to 21.9 kJ mol−1 and from −85.4 J mol−1 K−1 to −101.8 J mol−1 K−1, respectively. These values are similar to the values of immature Woodford kerogen concentrate previously observed, but are larger than naturally matured organic-rich shales. High-temperature hydrous pyrolysis might have induced Lewis acid sites on both organic and mineral surfaces, resulting to some extent, in chemical interactions between the adsorption site and the methane C–H bonds.The formation of abundant mesopores (2–50 nm) within organic matter during organic-matter thermal maturation makes a great contribution to the increase in both BET surface area and pore volume, and a significant increase in 2–6 nm pores occurs at maximum-oil-generation and oil-cracking to gas, ultimately controlling the methane-adsorption capacity. Therefore, consideration of pore-size effects and thermal maturity is very important for gas in place (GIP) prediction in organic-rich shales.

Experimental investigation of change in sheet resistance and Debye temperatures in metallic thin films due to low-energy ion beam irradiation

We present a systematic experimental investigation of low-energy (0–1 kV) ion irradiation induced changes in sheet resistivity and Debye temperatures in metallic nano-films of Ag, Cu and Al of thickness d/λo ∼ 2–5, where d is the film thickness and λo is the bulk mean free path, as a function of ion beam induced defects and impurities in a controlled manner. Ions of both atomic (Ne, Ar and Kr) and molecular (H2, N2) gases are employed in the investigation and the number of defects and impurities in the nano-film can be varied in a controlled manner by varying the ionic mass number (1–84) and beam fluence (8.7 × 1015–1.4 × 1016 ions cm−2). Low-temperature measurements are carried out for pristine and irradiated films to obtain the residual sheet resistance (RRS). An empirical formula relating the variation of RRS with beam fluence and ionic mass number is proposed for the first time. The change in RRS is due to the large diffusion of the impurities inside the nano-films as confirmed from energy dispersive x-ray spectroscopy. The Debye temperature (ΘD) is determined from Bloch–Grüneisen fitting of the temperature variation of sheet resistance data and it is found that ΘD decreases with increase in both fluence and ionic mass number arising primarily from the change in bulk modulus of the nano-film.

Locomotion with flexible propulsors: I. Experimental analysis of pectoral fin swimming in sunfish

A full understanding of the mechanics of locomotion can be achieved by incorporating descriptions of (1) three-dimensional kinematics of propulsor movement, (2) material properties of the propulsor, (3) power input and control and (4) the fluid dynamics effects of propulsor motion into (5) a three-dimensional computational framework that models the complexity of propulsors that deform and change area. In addition, robotic models would allow for further experimental investigation of changes to propulsor design and for testing of hypothesized relationships between movement and force production. Such a comprehensive suite of data is not yet available for any flexible propulsor. In this paper, we summarize our research program with the goal of producing a comprehensive data set for each of the five components noted above through a study of pectoral fin locomotion in one species of fish: the bluegill sunfish Lepomis macrochirus. Many fish use pectoral fins exclusively for locomotion, and pectoral fins in most fish are integral to generating force during maneuvering. Pectoral fins are complex structures composed of jointed bony supports that are under active control via pectoral fin musculature. During propulsion in sunfish, the fin deforms considerably, has two leading edges, and sunfish can rotate the whole fin or just control individual sections to vector thrust. Fin material properties vary along the length of fin rays and among rays. Experimental fluid dynamic analysis of sunfish pectoral fin locomotion reveals that the fin generates thrust throughout the fin beat cycle, and that the upper and lower edges each produce distinct simultaneous leading edge vortices. The following companion paper provides data on the computational approach taken to understand locomotion using flexible pectoral fins.

Cross-linked thermoplastic blends of polyethylene with an elastomer 4. Thermorelaxation and adhesion characteristics

The results of an experimental investigation of changes in the thermorelaxation and thermoshrinkage stresses and the strength of adhesion joints with steel of binary blends of high-density polyethylene with an elastomer (ethylene-propylene-dicyclopentadiene terpolymer) in the course of γ-radiation and chemical cross-linking are reported. The interconnection/relationship between the highest values of the stresses, as well as the characteristics of formation processes of the joints, and certain structural characteristics of the blends (content of their cross-linked part, the degree of crystallinity, etc.) is discussed.

Experimental study of the behaviour of real asperities within lubricated contacts

Thin film colorimetric interferometry was used in combination with phase shifting interferometry for the detailed experimental investigation of changes in real surface microgeometry within the elastohydrodynamic conjunction formed between a real, random, rough surface, a steel ball and a smooth glass disc. Three real roughness features were studied in detail — the transverse ridge, transverse groove and longitudinal groove. The ridge was found to be heavily deformed within lubricated contact and its height increased with increasing rolling speed. For the transverse groove, a local reduction in film thickness at the leading edge was observed, while the longitudinal groove maintained its undeformed shape. Copyright © 2006 John Wiley & Sons, Ltd.

Influence of annealing on the diffusion characteristics and optical losses of multimode Ag +-glass waveguides

In the recent paper the experimental investigation of changes of optical and diffusion characteristics of multimode Ag +-glass waveguides in the process of annealing is presented. It has been shown that the process of refractive index profile redistribution in investigated samples had irregular and step-by-step character. At first the refractive index in the underlying waveguide layers increased because of a silver ions outflow from near-surface regions. Then silver ions started to migrate all over the waveguide profile and finally the silver ion concentration did not vary significantly in the medium layers of waveguide but the waveguide length kept growing. The refractive index profile redistribution was accompanied by change of waveguide mode losses. Experimental results let us conclude that major sources of optical losses were the microscopic metallic conglomerates in the waveguide region. During annealing their concentration in the near surface region decreased at first and then increased while in the underlying regions their concentration practically did not change. The space and temporal dependences of diffusion coefficients of the ion-exchanged process of silver ions in glass have been obtained in the result of the inverse diffusion problem solution. The maximum value of the diffusion coefficient was about 2.73×10 −15 m 2/ s .

Experimental Investigation of Changes in the Wall Temperature in Different Regimes of Motion of Supercritical-Pressure Liquids

Results of an investigation of the temperature regime of a wall for the laminar, transient, and turbulent regimes of motion of an ascending flow and different temperatures of toluene are given. Conditions for the occurrence of improved and impaired regimes of heat transfer with different characters of changes in the wall temperature are revealed.

An experimental investigation of changes in the meaning of level of aspiration.

An experimental investigation of changes in the meaning of level of aspiration.