ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels最新文献

{"title":"Wetting of Water Drops on a PMMA Substrate in Viscous Medium","authors":"Kumari Trinavee, N. Gunda, S. Mitra","doi":"10.1115/ICNMM2018-7631","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7631","url":null,"abstract":"There is a significant surge in the development of water repellant (superhydrophobic), oil repellent (superoleophobic) surfaces. Though these surfaces are well studied for air medium (inviscid), still there is a lack of fundamental understanding of wetting behavior in presence of surrounding viscous medium. In the present work, we investigate the wetting behaviour of water drops on a PMMA substrate surrounded by viscous oil medium for a wide range of viscosity ratio. The sessile drop is generated at the needle tip (J-needle for denser oil) close to the PMMA substrate to initiate the spreading of a water drop on the substrate. Experimentally measured contact angle at static equilibrium can well interpret the wetting behaviour of water drop on PMMA substrate placed in oil (surrounding medium). It is also observed that the theoretical values of water (drop)-oil and oil (drop)-water system satisfy the Young’s equation of two liquid system, but certain percentage errors are observed when compared to experimental results. These differences are interpreted in terms of interfacial energies of the two-liquid systems. In addition, ‘complementary hysteresis’ model recently put forward by Ozkan et al. [Surf. Topogr.: Metrol. Prop.2017,5,024002] is modified to study the wetting characteristics. Finally, based on the comparison of experimental and theoretical values, a short perspective is provided on the potential of a stable thin lubricant film under the droplet that changes the wetting characteristics of the substrate.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114921762","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 Size and Sodium Dodecyl Sulfate on Mass Transfer for Liquid-Liquid Two-Phase Flow in Non-Circular Glass Microchannels","authors":"A. Svensson, Zan Wu, B. Sundén","doi":"10.1115/ICNMM2018-7626","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7626","url":null,"abstract":"This study concerns effects of two main variables on hydrodynamics and mass transfer in the liquid-liquid two-phase slug flow regime. The influence of size of square and rectangular microchannels and presence of sodium dodecyl sulfate (SDS) are investigated. Three microchannels with dimensions 600×600 (MC600), 400×400 (MC400) and 600×300 (MC300) μm were used with hydraulic diameters of 600, 400 and 400 μm respectively. The results revealed that decreasing the hydraulic diameter improved the interfacial area due to slug length enlargement in both phases. Furthermore, mass transfer resistance was reduced because of enhanced internal circulations, leading to considerable enhancement of the overall mass transfer coefficient KL. It was also found that the enhancement of KL was greater in the square MC400 microchannel than in the rectangular MC300, as compared to the MC600. The enhancing benefit from internal circulations in organic slugs in rectangular microchannels decreased at higher aqueous flow rates due to enlarged stagnant liquid film flow between the organic slug and the microchannel wall.\u0000 The presence of SDS slightly increased the interfacial area by reducing the slug length in both phases. However, there was a significant decrement in KL, due to a greater mass transfer resistance.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133097173","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":"Synthesis of Polydimethylsiloxane Microspheres Using Microfluidics for Treatment of Toluene in Wastewater","authors":"Zheng Lian, Y. Ren, Jun He, G. Chen, K. Koh","doi":"10.1115/ICNMM2018-7775","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7775","url":null,"abstract":"Monodispersed polydimethylsiloxane (PDMS) microspheres are fabricated by a needle-based versatile microfluidic device with flow-focusing geometry. Microdroplets with various diameters are generated by tuning the flow rate of the dispersed and continuous phase, using single emulsion as the template. The collected PDMS microdroplets are then thermally cured to form solid microspheres. We employ an optical microscope to observe the particles and capture photos. The figures are processed by ImageJ which measures the diameter of each particle. The coefficients of variation (CV) of particles are found to be less than 1.5% for all sizes, indicating that a high monodispersity has been achieved. Thereafter, we adopt the PDMS microspheres to a simulated industrial wastewater that contains organic pollutant such as toluene, for removing purposes. Since the solubility parameters of PDMS and toluene are close, toluene molecules can be extracted from its solvent into PDMS. The absorption efficiency provided by PDMS microspheres on organic pollutant such as toluene has been tested by utilizing a Headspace-Gas Chromatography (GC-HS). We then compare the obtained peak signals of toluene before and after treatment to verify the treatment effect. The needle-based microfluidic device is advantageous in its facile assembly and low cost, displaying a great potential for industrial applications.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129171945","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":"Evaluation of Heat Transfer Performance of a Spiral Microfluidic Heatsink and Heat Exchanger Device","authors":"N. S. Virik, S. D. Marshall, R. Arayanarakool, H. See, Heng Wang, P. Lee, Peter Chen Chao Yu","doi":"10.1115/ICNMM2018-7804","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7804","url":null,"abstract":"Developments in micro-technology have seen vast improvements in the design and the thermal performance of heat sinks and heat exchangers, particularly in the case of spiral microfluidic devices which deals with the flow of liquids inside curved micrometer-sized channels. The current research deals with a specially designed curved microfluidic channel used to employ the fluid mixing characteristics of Dean vortices and thus transfer heat more efficiently. This curved microfluidic channel is deployed as a spiral channel to create an effective heat sink and a heat exchanger.\u0000 The novel micro heat exchanger is built by integrating two or more of the specially designed microfluidic heat sink layers. For the ease of fabricating the microchannels, these devices are polymer-based. In this paper, the thermal performance of the spiral microfluidic devices is analyzed numerically and experimentally using a range of flow rates where Thermal Performance Factor is used to find a balanced point between heat transfer and pressure drop. The spiral heat exchange device proves to be an effective thermal transport system with the introduction of curved channels in the devices where the presence of Dean vortices in the system is observed, especially at lower flow rates. It can be observed that by increasing the number of layers, the thermal performance is greatly improved. This is due to the higher surface area with increasing number of layers, as well as a parallel flow structure through the layers.\u0000 These results serve as a design parameter for developing microchannel-based heat transfer devices that can achieve high efficiency of heat and mass transfer. Further heat sink and heat exchanger design improvements are discussed.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123627818","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":"Influence of Condensation on the Outer Surface of Polymer Hollow Fiber Heat Exchangers During Heat Transfer","authors":"T. Brozova, E. Bartuli","doi":"10.1115/ICNMM2018-7728","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7728","url":null,"abstract":"Condensation during heat transfer processes can be very beneficially used due to the large amount of energy contained in phase change (vapor to liquid). This contribution focuses on the possible use of polymer hollow fiber heat exchangers (PHFHEs) in air conditioning. PHFHEs consist of hundreds or thousands of polymer hollow fibers with an outer diameter of around 1 mm. The wall thickness is approximately 10% of the outer diameter. PHFHEs are heat exchangers with such benefits as low weight, easy shaping, corrosion resistance, and resistance to many chemical solutions. In comparison with metal heat exchangers (made of copper, aluminum, or stainless steel) the plastic wall of PHFHEs has low thermal conductivity (between 0.1 and 0.4 Wm-1K-1). This seems to be their key disadvantage. However, due to the extremely small thickness of the fiber’s wall this disadvantage is negligible. PHFHEs are compact heat exchangers with a large heat transfer area with respect to their volume.\u0000 This paper shows the results of condensation tests for PHFHEs that consist of 6 equivalent layers of polypropylene fibers with a length of 190 mm. The total number of fibers is 798. The air humidity was set to 50% with an air temperature of 27°C, which are the typical conditions for such tests in air conditioning technology. Another important parameter was the velocity of the air. Testing velocities were chosen as 3 m s−1 and 1 m s−1.\u0000 The influence of gravity was studied by putting the PHFHEs in three different positions. The fibers were placed in horizontal and vertical positions, and in a position where fibers form an angle of 45° with the ground.\u0000 The study showed the ineffectiveness of placing the PHFHE in a horizontal position and suggests that it is better to have a larger distance between the layers of fibers.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"54 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133891485","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":"Experimental Investigations on Thermal Performance of PCM Based Heat Sink for Passive Cooling of Electronic Components","authors":"R. Kothari, Pawan Mahalkar, S. Sahu, S. I. Kundalwal","doi":"10.1115/ICNMM2018-7732","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7732","url":null,"abstract":"In the present experimental study, an attempt has been made to study the efficient thermal management system based on phase change material for cooling of portable electronic devices. Paraffin wax is used as PCM to keep the temperature of electronic devices below critical temperature by absorbing thermal energy released by electronic components. PCM is filled inside the heat sink made of aluminum. Four different configuration of heat sink such as unfinned heat sink filled with pure PCM, two finned heat sink filled with pure PCM, unfinned heat sink filled with MF-PCM composite and two finned heat sink filled with MF-PCM composite are used in the present investigation to enhance the operating time of heat sink to reach critical set point temperature. Unfinned heat sink filled with and without PCM is used for baseline comparison. Effect of volume fraction of PCM, effect of heat flux and enhancement in operating time are reported in this study. Enhancement ratios are obtained for various heat sink configurations. The comparison of thermal performance of different configuration shows that higher enhancement ratio and effective thermal control is obtained with two finned metal foam heat sink.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131255095","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":"A Volume of Fluid Based Model for the Simulation of Bubble Growth Over a Heated Surface","authors":"I. Perez-Raya, S. Kandlikar","doi":"10.1115/ICNMM2018-7710","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7710","url":null,"abstract":"Nucleate boiling simulations uncover the dynamic and thermal behavior near the bubble-edge for different fluids and operating conditions. This information is essential to optimize boiling systems and to propose more effective heat and mass transport mechanisms. Some of the main challenges simulating boiling are preserve interface sharpness, compute mass transfer, and include interface effects. The present work analyzes the role of mass transfer estimation, sharp interface model, and surface tension computation on interface deformations in the simulation of bubble growth over a heated surface. The simulation accounts for the saturation temperature of the bubble-edge and computes mass transfer with interfacial temperature gradients. Volume-of-fluid tracks the interface and defines interfacial gradients. Results provide evidence of a stable and more realistic simulation that declares mass transfer only on mixture cells and that defines a sharp interface. In addition, results show that surface tension effects play a primary role on interface deformations. Numerical results reveal the formation of a thin thermal film near the bubble edge and liquid moving away from the interface due to vapor expansion.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129695915","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":"Flow Pattern, Heat Transfer and Pressure Drop Behaviors of Micro-Channel Flow Boiling","authors":"S. Saisorn, Pochai Srithumkhant, Pakorn Wongpromma, M. Suchatawat, S. Wongwises","doi":"10.1115/ICNMM2018-7672","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7672","url":null,"abstract":"Two-phase flow of R-134a with high confinement number was experimentally carried out in this study. Flow boiling conditions for different orientations were controlled to take place in a stainless steel tube having a diameter of 0.5 mm. Based on a saturation pressure of 8 bar, a heat flux range of 2–26 kW/m2, and a mass flux range of 610–815 kg/m2s, a constant surface heat flux condition was controlled by applied DC power supply on the test section. The flow behaviors were described based on flow pattern and pressure drop data while heat transfer mechanisms were explained by using heat transfer coefficient data. In this work, nucleate boiling was observed, and the importance of the change in the flow direction was neglected, corresponding to the confinement number of around 1.7.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132183495","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":"Effect of Microstructures on Superhydrophobic and Slippery Lubricant-Infused Porous Surfaces During Condensation Phase-Change","authors":"D. Orejón, Yota Maeda, F. Lv, Peng Zhang, Y. Takata","doi":"10.1115/ICNMM2018-7640","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7640","url":null,"abstract":"Superhydrophobic surfaces (SHSs) and slippery lubricant-infused porous surfaces (SLIPSs) are receiving increasing attention for their excellent anti-icing, anti-fogging, self-cleaning and condensation heat transfer properties. The ability of such surfaces to passively shed and repel water is mainly due to the low-adhesion between the liquid and the solid surface, i.e., low contact angle hysteresis, when compared to hydrophilic or to hydrophobic surfaces. In this work we investigated the effect of surface structure on the condensation performance on SHSs and SLIPSs. Three different SHSs with structures varying from the micro- to the nano-scale were fabricated following easy and scalable etching and oxidation growth procedures. The condensation performance on such surfaces was evaluated by optical microscopy in a temperature and humidity controlled environmental chamber. On SHSs important differences on the size and on the number of the coalescing droplets required for the jump to ensue were found when varying the surface structure underneath the condensing droplets. A surface energy analysis is proposed to account for the suppression of the droplet-jumping performance in the presence of microstructures. On other hand, by impregnating the same SHSs with a low surface tension oil, i.e., SLIPSs, the adhesion between the condensate and the SLIPSs can be further reduced. On SLIPSs slight differences on the droplet density over time and shedding performance upon the inclusion of microstructures were observed. Droplets were found to shed faster and with smaller diameters on SLIPSs in the presence of microstructures when compared to solely nanostructured SLIPSs.\u0000 We conclude that on SHSs the droplet-jumping performance of micrometer droplets is deteriorated in the presence of microstructures with the consequent decrease in the heat transfer performance, whereas on SLIPSs the droplet self-removal is actually improved in the presence of microstructures.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128279232","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":"Numerical Investigation on Thermo-Hydrodynamic Performance of Recharging, Interrupted and Straight Microchannels: A Comparative Study","authors":"Sangram Kumar Samal, M. Moharana","doi":"10.1115/ICNMM2018-7725","DOIUrl":"https://doi.org/10.1115/ICNMM2018-7725","url":null,"abstract":"In this study, a three-dimensional numerical investigation on the thermo-hydrodynamic performance of a newly proposed recharging microchannel (RMC) is carried out. In this new design, a straight microchannel separated into more than one small channels and each small channels having individual inlet and outlet. This design enhances the heat transfer and makes the temperature almost uniform across the length of the substrate. The comparison of fluid flow and heat transfer performance between this recharging microchannel (RMC), interrupted microchannel (IMC) and straight microchannel (SMC) with same hydraulic diameter and substrate length were conducted to explore the effect of geometrical configuration on the heat transfer enhancement. The results reveal that for the recharging microchannel, the average Nusselt number increases by 49–122%, while the total pressure drop increases by 15–89%, compared with the interrupted and straight microchannel for the Reynolds number ranging from 100 to 500. From the result, it is also observed that for the investigated Reynolds number range the recharging microchannel having the highest thermal performance compared to interrupted and straight microchannel with a maximum performance factor of 1.80. The outcome of this study indicates possible use of recharging microchannel heat sinks for high heat flux removal applications such as electronic cooling.","PeriodicalId":137208,"journal":{"name":"ASME 2018 16th International Conference on Nanochannels, Microchannels, and Minichannels","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122001265","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}