Sambhaji T. Kadam, Ibrahim Hassan, Ritunesh Kumar, A. Rahman
{"title":"Review on Bubble Dynamics in Microchannel Heat Sink","authors":"Sambhaji T. Kadam, Ibrahim Hassan, Ritunesh Kumar, A. Rahman","doi":"10.1115/icnmm2019-4242","DOIUrl":"https://doi.org/10.1115/icnmm2019-4242","url":null,"abstract":"\u0000 Inception of the boiling, in pool or flow boiling, is the formation of the vapour bubble at active nucleation site. The bubble dynamics plays an important role in the boiling process. It is critical as it unfolds many facets especially when channel size is reduced to submicron. The detailed knowledge of the bubble dynamics is helpful in establishing the thermal and hydraulic flow behaviour in microchannel. In this paper, the bubble dynamics which include bubble nucleation at nucleation site, its growth, departure and motion along the flow in a microchannel are discussed in details. Different models are developed for the critical cavity radius are compiled and observed that they show large variation when compare. The bubble growth models are compiled and concluded that a development of more generalized bubble growth model is necessary to account for the inertia controlled and thermal diffusion controlled regions. The bubble at the nucleation site in a microchannel grows under the influence of various forces such as surface tension, inertia, shear, gravitational and evaporation momentum. Parametric variations of these forces are critically studied and reckoned that the slope of these forces seems to be reduced beyond 500 μm. Eventually, possible impact of the various factors such as operating conditions, geometrical parameters, and thermophysical properties of fluid on bubble dynamics in microchannel has been reported.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"37 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123252037","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Parametric Study of Vortex Generator Effects in an Additive Manufactured Minichannel Heat Exchanger","authors":"Hamidreza Rastan, T. Ameel, B. Palm","doi":"10.1115/icnmm2019-4236","DOIUrl":"https://doi.org/10.1115/icnmm2019-4236","url":null,"abstract":"\u0000 Heat exchangers with mini- and micro-channel components are capable of high energy exchange due to their incumbent large surface area to volume ratio. Concurrently, recent advances in additive manufacturing simplify the creation of metallic minichannels that incorporate turbulators for heat transfer enhancement. As part of the development of a minichannel heat exchanger with turbulators, this study analyzes the three-dimensional conjugate heat transfer and laminar flow in a minichannel heat exchanger equipped with rectangular winglet vortex generators (VGs) through numerical simulation. The minichannels have a hydraulic diameter of 2.86 mm and are assumed to be made from aluminum alloy AlSi10Mg. This material is one of the popular alloys in the additive manufacturing industry (three-dimensional (3D) printing) because of its light weight and beneficial mechanical and thermal properties. The working fluid is distilled water with temperature-dependent thermal properties. The minichannel is heated by a constant heat flux of 5 W cm−2 and the Reynolds number is varied from 230 to 950. The simulations are performed using the COMSOL® platform, which solves the governing mass, momentum, and energy equations based on the finite element method. The effect of the VG design parameters, which include VG angle of attack, height, length, thickness, longitudinal pitch, and distance from the sidewalls, is investigated. It is found that the generation of three-dimensional vortices caused by the presence of the vortex generators can notably boost the convective heat transfer, at the cost of increased pressure drop, potentially reducing the heat exchanger size for a given heat duty. A sensitivity analysis indicates that the angle of attack, VG height, VG length, and longitudinal pitch have the most significant effects on the heat transfer and flow friction characteristics. In contrast, the VG thickness and distance from the sidewalls only had minor influences on the heat exchanger performance over the studied range of design parameters.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"90 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122440860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Laminar Heat Transfer of Gas-Liquid Segmented Flows in Circular Ducts With Constant Wall Temperature","authors":"K. Alrbee, Y. Muzychka, X. Duan","doi":"10.1115/icnmm2019-4216","DOIUrl":"https://doi.org/10.1115/icnmm2019-4216","url":null,"abstract":"\u0000 Laminar heat transfer of gas-liquid Taylor flow in circular tubes is considered. Previous studies have found that introducing a gas phase into a flow stream of a liquid phase significantly increases the heat transfer rate. Other studies considered the effect of slug length on heat transfer rates. The present study’s aim is to demonstrate heat transfer enhancement due to the shortening of liquid slug lengths in a segmented flow and to further validate a model previously developed by the second author. An experimental setup was assembled using mini scale horizontal tube in which the two phase fluid flow is heated under constant wall temperature. New experimental data for gas-liquid Taylor flow in mini scale were carefully obtained using 1 cSt silicone oil which was segmented by air. The experiments were performed with a liquid fraction maintained constant at 0.5 and Reynolds numbers from 50 to 320. In the present work, it is shown that for constant wall temperature, the dimensionless mean wall flux and Nusselt number have been increased by a factor of two at the upper limit of laminar flow which was considered with ReD = 320, when the slug aspect ratio LS/D equal to 10. On other hand the enhancement becomes three times at the same limit of flow when slug aspect ratio has reduced to 1.25 which almost approaches the tube diameter.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125061930","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Investigation of Multiphase Interfaces in Small Channels Using Micro CT","authors":"J. Schuler, N. Kockmann","doi":"10.1115/icnmm2019-4203","DOIUrl":"https://doi.org/10.1115/icnmm2019-4203","url":null,"abstract":"\u0000 For the process intensification in miniaturized equipment with multiphase systems the spatial extension and shape of the interface is crucial. However, examining interfaces on the submillimeter to the submicron range is challenging due to limited optical accessibility. Therefore, in this work, micro computed X-ray tomography was applied to visualize static multiphase interfaces in small channels. The present work also introduces an image processing procedure used for the reconstruction of the tomographic data. To demonstrate both, the information value of 3D tomographic data and its advantages compared to conventional 2D imaging techniques, the contact angle between different fluid pairings and the solid channel is determined. This work forms the foundation for the three dimensional examination of multiphase flows and mass transfer in micro and milli channels.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"293 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124210000","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Bobers, Maurice Hesselmann, A. Schneider, J. Zimmermann, N. Kockmann
{"title":"Development of a Manufacturing Process for Polyimide-Based Microstructured Devices Using Reactive Ion Etching","authors":"J. Bobers, Maurice Hesselmann, A. Schneider, J. Zimmermann, N. Kockmann","doi":"10.1115/icnmm2019-4208","DOIUrl":"https://doi.org/10.1115/icnmm2019-4208","url":null,"abstract":"\u0000 Miniaturization and modularization are fast growing fields in chemical engineering in recent years. Fast and flexible production processes for microstructured devices are desirable to meet the requirements of rapid prototyping and flexible chip manufacturing. Reactive ion etching provides a structuring process which leads to a highly precise and anisotropic etching behavior. A new manufacturing process for polyimide-based microstructured devices with low surface roughness was developed and applied on reactor geometry for liquid-liquid two-phase-flow. The fabricated chip geometry is designed for creating droplets via flow focusing as the dispersed phase is incised by two continuous phase inlet streams. The droplets are created in the widening channel. In order to keep the pressure loss for the developed reactor geometry and the production time as small as possible, the manufacturing process was optimized with a view to minimize surface roughness and maximizing the etching rate by using Design of Experiments. The corresponding pressure drop was measured for flow rates from 0.05 ml min−1 to 0.5 ml min−1.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130817538","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Fabrication and Corrosion Performance of a Superhydrophobic Stainless Steel Surface","authors":"Mona Amiriafshar, X. Duan, A. Nasiri","doi":"10.1115/icnmm2019-4209","DOIUrl":"https://doi.org/10.1115/icnmm2019-4209","url":null,"abstract":"\u0000 Fabrication of surfaces with hydrophobic and superhydrophobic property has drawn extensive interests as a solution to protect metal surfaces from corrosion attacks, with potential applications in cooling devices for electronics, microfluidic systems for controlled drug delivery, as well as anti-icing, and self-cleaning techniques. This study addresses the impact of surface wettability, i.e., hydrophobicity and superhydrophobicity, on corrosion resistance improvement of metal materials. Hydrophobic and superhydrophobic metal surfaces are desirable to minimize the adhesion between water droplets and the surface. This study aims to fabricate and investigate 17-4 PH stainless steel surfaces with lowered surface energies and modified wetting properties. Various micro- and sub-micro scale finished surfaces with different surface roughness, namely as-received, sandblasted, ground, and polished, were employed, followed by applying a low energy superhydrophobic coating to fabricate hydrophobic and superhydrophobic surfaces on 17-4 PH stainless steel base material. The specific impacts of the surface roughness on wettability and corrosion resistivity of the manufactured surfaces were examined. The ground and polished surfaces followed by applying a 30–50 μm thick superhydrophobic dip coating resulted in steady-state contact angles of up to 152° and 146°, respectively, while the non-engineered coated base metal exhibited the contact angle of 140°. The ground surface with the average surface roughness (Ra) of ∼ 0.03 μm has the optimal roughness. According to the Cassie-Baxter model, the coated ground surface can retain the entrapped air within its interstices more adequately than the other surfaces with either lower surface roughness, such as the polished surface with the roughness of 0.02 μm, or higher surface roughness, such as as-received and sandblasted surfaces with the Ra value of 5.52 μm and 11.98 μm, respectively.\u0000 To study the corrosion performance and electrochemical stability of the fabricated surfaces, cyclic polarization testing (CPT) and electrochemical impedance spectroscopy (EIS) were performed in an aerated 3.5 wt.% NaCl solution that mimics seawater environment. The electrochemical measurements confirmed that the water-repelling property of the surface contributes to the anti-corrosion capability of the substrate. Data from the corrosion tests indicate that the lowest corrosion current density, highest corrosion potential, and highest pitting potential, were found for the coated ground surface followed by the coated polished surface. The EIS results also highlighted the significantly greater absolute value of impedance for the coated ground and coated polished surfaces even after 240 hrs of immersion in the electrolyte solution than the other fabricated surfaces at lower frequency ranges. The improvement in the 17-4 PH stainless steel corrosion performance was contributed to the size of the fabricated surface micro- and sub-micro scale fe","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"174 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114240876","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Mortazavi, Anthony D. Santamaria, Jingru Benner, Vedang Chauhan
{"title":"Enhanced Liquid Water Removal From PEM Fuel Cell Flow Channels by Superimposing Acoustic Pressure Wave on Air Flow","authors":"M. Mortazavi, Anthony D. Santamaria, Jingru Benner, Vedang Chauhan","doi":"10.1115/icnmm2019-4295","DOIUrl":"https://doi.org/10.1115/icnmm2019-4295","url":null,"abstract":"\u0000 Enhanced water removal from the flow channel of an ex-situ PEM fuel cell test section is obtained by superimposing acoustic pressure wave on air flow prior to entering into the flow channel. Water accumulation within the flow channel was visualized with a CCD camera and liquid-gas two-phase flow pressure drop was measured along the flow channel. Acoustic pressure waves were superimposed in sine waves at different frequencies between 20 and 120 Hz with a 20-Hz interval. Results indicated that water accumulation in the flow channel was lowest when acoustic pressure waves were superimposed at 80 Hz on air flow. For experiments with no acoustic vibration, the average water slug cumulative area for three runs was obtained at 288.6 mm2 while this average was as low as 43.9 mm2 for experiments conducted at 80 Hz. For other frequencies tested (20, 40, 60, 100, and 120 Hz), water accumulation within the flow channel was less than that for experiments with no vibration but the accumulation of water was still greater than experiments conducted at 80 Hz. The two-phase flow pressure drops were also lowest for experiments conducted at 80 Hz while the highest pressure drops were obtained in experiments with no acoustic vibration. Droplets were also visualized from a side-view angle in a goniometer in order to obtain contact angles. Images showed droplet oscillation under the influence of acoustic vibration. For the three superficial air velocities tested in this study (1.30, 1.82, and 2.30 m/s) the contact angle hysteresis were almost identical with an average value around 40°.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"13 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125273874","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Falling Film Evaporation of HFO-1233zd(E) in Vertical Rectangular Minichannels Consisting of Serrated-Fins","authors":"J. Ohara","doi":"10.1115/icnmm2019-4221","DOIUrl":"https://doi.org/10.1115/icnmm2019-4221","url":null,"abstract":"\u0000 In the present study, the characteristics of heat transfer are experimentally investigated on the falling film evaporation of alternative pure refrigerant HFO-1233zd(E) in a plate-fin heat exchanger having a vertical rectangular minichannels of 2.11 mm hydraulic diameter consisting of serrated-fins. The refrigerant liquid is supplied to the channel through 37 holes of a liquid distributor. The liquid flowing down vertically is heated electrically from the rear wall of the channel and evaporated. The experimental parameters are as follows: the mass velocities are varied 7.4∼55.1 [kg/(m2s)], the heat fluxes are varied 8.7∼50 [kW/m2] and the pressures are about 100 [kPa].\u0000 In the case of small mass velocity being smaller than 20 [kg/(m2s)], heat transfer coefficient decreases monotonously and gradually with increase of quality and take value of 5∼1[kW/m2K]. It is thought that the cause of lower value of heat transfer coefficient is occurring dry patch and aria enlargement of dry area in the downstream region. In the case of large mass velocity being larger than 41 [kg/(m2s)], the value of heat transfer coefficient becomes larger with increase of quality except for the case of mass velocity being 41 [kg/(m2s)] and heat flux being 50[kW/m2]. Improved heat transfer is to be thinkable that the liquid and vapor flow becomes dripping in the middle-stream region, and turns into mist flow with thin liquid film on the fin surface in the downstream region of quality being larger than 0.4.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125242387","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Stability and Scalar Transport in Laminar Non-Newtonian Flow in a Bifurcating T-Junction","authors":"A. Chatterjee, F. Khalkhal","doi":"10.1115/icnmm2019-4274","DOIUrl":"https://doi.org/10.1115/icnmm2019-4274","url":null,"abstract":"\u0000 We consider the prototype bifurcating T-junction planar flow and compare the stability of the steady two-dimensional flow field for a Newtonian and a shear thinning inelastic fluid. Global stability of the flow to two-dimensional perturbations is analyzed using numerical solutions of the linear perturbation equation. Calculations are performed for two flow ratios between the main channel and the bifurcating channel, and for two different values of the time constant in the non-Newtonian rheological model. The results show that although the steady flow remains stable to two-dimensional perturbations for Newtonian Reynolds number up to ∼ 400, shear thinning is destabilizing in that the decay rate of the perturbation field is slower. The perturbation growth rate curves for all of the different cases may be correlated by volume averaging the local Reynolds number over the flow domain, indicating that the effect of shear thinning on stability may be described using a suitably defined average Reynolds number. These stability results provide some justification for CFD calculations of steady non-Newtonian two-dimensional flows presented in earlier papers. Since scalar transport is of interest in this flow field, we also present some numerical calculations for the Nusselt number profile along the bifurcating channel wall. The results show that for the shear thinning fluid the scalar transport rate is differentially larger by ∼ 75% across one of the bifurcating channel walls, a consequence of fluid rheology enhancing the effect of flow asymmetry in the entrance region of the bifurcation.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"116 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124601321","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Effects of Channel Length and Chevron Angle on Pressure Drop in the Entrance Region of Corrugated Rib Channels","authors":"M. Hamoda, K. Pope, Y. Muzychka","doi":"10.1115/icnmm2019-4254","DOIUrl":"https://doi.org/10.1115/icnmm2019-4254","url":null,"abstract":"\u0000 Plates with corrugated walls are used in plate heat exchangers for heat transfer enhancement usually at the expense of the fluid friction. In this paper, the effects of varying channel lengths and corrugation angles on the pressure drop in corrugated rib channels are examined. Water was used as the working fluid and the Reynolds number varied over the range 400 ≤ ReDe ≤ 2,500. The test fixture is constructed from aluminum and the plates core were machined with the same corrugation depth, 1.14 mm, but with different lengths, 10.16 cm and 20.32 cm and different corrugation inclination angles, 30°, 45°, and 60°. The hydraulic diameter of the formed channel is about 2.0 mm. Experimental results show that the friction factor for the short ribbed plates is significantly higher than those of the longer ribbed plates. In addition, the pressure drop increases with an increase of the corrugation angle for all ribbed plates tested. Based on the experimental results, correlations for predicting friction factor are proposed.","PeriodicalId":221056,"journal":{"name":"ASME 2019 17th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115380885","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}