bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Investigation of Cycle Properties, Noise, and Air Pollutant Emissions of an APS3200 Auxiliary Power Unit
Authors: Siebel Teresa , Zanger Jan , Huber Andreas , Aigner Manfred , Knobloch Karsten , Bake Friedrich
Published: October 2017

Auxiliary power unit (APU) operators face increasingly stricter airport requirements concerning exhaust gas and noise emission levels. To simultaneously reduce exhaust gas and noise emissions and to satisfy the increasing demand of electric power on board, optimization of the current technology is necessary. Prior to any possible demonstration of optimization potential, detailed data of thermodynamic properties and emissions have to be determined. Therefore, the investigations presented in this paper were conducted at a full-scale APU of an operational aircraft. A Pratt & Whitney (East Hartford, CT) APS3200, commonly installed in the Airbus A320 aircraft family, was used for measurements of the reference data. In order to describe the APS3200, the full spectrum of feasible power load and bleed air mass flow combinations were adjusted during the study. Their effect on different thermodynamic and performance properties, such as exhaust gas temperature, pressure as well as electric and overall efficiency is described. Furthermore, the mass flows of the inlet air, exhaust gas, and fuel input were determined. Additionally, the work reports the exhaust gas emissions regarding the species CO2, CO, and NOx as a function of load point. Moreover, the acoustic noise emissions are presented and discussed. With the provided data, the paper serves as a database for validating numerical simulations and provides a baseline for current APU technology.
Model Following Adaptive Sliding Mode Tracking Control Based on a Disturbance Observer for the Mechanical Systems
Authors: Chen Kun-Yung
Published: October 2017

A model following adaptive sliding mode tracking control (MFASMTC) with the adjustable control gain based on a disturbance observer (DOB) for the mechanical system is proposed in this paper. The control gains of the proposed controller are automatically adjusted to compensate the unknown time-varying disturbances by the DOB. First, the unknown variables and uncertainties are lumped as the disturbance terms and the system dynamic model consist of the nominal matrix and disturbances vector. The desired model and sliding mode controller (SMC) are integrated by using the Lyapunov function candidate to obtain the general model following sliding mode tracking control (MFSMTC) with the fixed control gain. To stabilize and compensate the unknown time-varying disturbances for the control system, a DOB is combined with the MFSMTC to obtain the MFASMTC to automatically adjust the control gains. The mass-spring-damper system and two-link manipulator robot system are both used as examples system to demonstrate the proposed control scheme, respectively. The comparisons between MFSMTC with the fixed control gain and MFASMTC with the adjustable control gain based on a DOB are performed in this paper. From the simulation results, the proposed MFASMTC with the adjustable control gain based on a DOB demonstrates the stable and robust control performance for the unknown uncertainties and external disturbances. The proposed control method also can be applied to the other mechanical systems with the desired model to find the desired model following adaptive sliding mode tracking control.
On the Impulse Produced by Chordwise Flexible Pitching Foils in a Quiescent Fluid
Authors: Huera-Huarte Francisco J.
Published: October 2017

In this paper, a parametric study showing the impulsive performance of foils with different flexural stiffness pitching in a quiescent fluid is presented. A wide range of Reynolds numbers (different imposed kinematics) and foil rigidities is covered, depicting how flexibility effects on impulse are more important at the largest Reynolds numbers. The impulsive performance of the system is derived from direct thrust force measurements. Passive flexibility alters vortex strength and formation in the wake of the pitching foil. These changes in the wake formation can be used to explain the differences in the measured impulses. The wake dynamics is studied after quantitative analysis of particle image velocimetry data, and it is linked to the momentum transfer generated by the foil.
Effectiveness Measurements of Additively Manufactured Film Cooling Holes
Authors: Stimpson Curtis K. , Snyder Jacob C. , Thole Karen A. , Mongillo Dominic
Published: October 2017

As additive manufacturing (AM) technologies utilizing metal powders continue to mature, the usage of AM parts in gas turbine engines will increase. Current metal AM technologies produce parts with substantial surface roughness that can only be removed from external surfaces and internal surfaces that are accessible for smoothing. Difficulties arise in making smooth the surfaces of small internal channels, which means the augmentation of pressure loss and heat transfer due to roughness must be accounted for in the design. As gas turbine manufacturers have only recently adopted metal AM technologies, much remains to be examined before the full impacts of applying AM to turbine parts are understood. Although discrete film cooling holes have been extensively studied for decades, this objective of this study was to understand how the roughness of film cooling holes made using AM can affect the overall cooling effectiveness. Coupons made from a high temperature nickel alloy with engine-scale film holes were tested in a rig designed to simulate engine relevant conditions. Two different hole sizes and two different build directions were examined at various blowing ratios. Results showed that the effectiveness is dependent on the build direction and the relative size of the hole. It was also discovered that commercially available AM processes could not reliably produce small holes with predictable behavior.
The Correlation of Heat Transfer Coefficients for the Laminar Natural Convection in a Circular Finned-Tube Heat Exchanger
Authors: Kang Hie Chan , Chang Se-Myong
Published: October 2017

This study proposes an empirical correlation for laminar natural convection applicable to external circular finned-tube heat exchangers with wide range of configuration parameters. The transient temperature response of the heat exchangers was used to obtain the heat transfer coefficient, and the experimental data with their characteristic lengths are discussed. The data lie in the range from 1 to 1000 for Rayleigh numbers based on the fin spacing: the ratio of fin height to tube diameter ranges from 0.1 to 0.9, and the ratio of fin pitch to height ranges from 0.13 to 2.6. Sixteen sets of finned-tube electroplated with nickel–chrome were tested. The convective heat transfer coefficients on the heat exchangers were measured by elimination of the thermal radiation effect from the heat exchanger surfaces. The Nusselt number was correlated with a newly suggested composite curve formula, which converges to the quarter power of the Rayleigh number for a single cylinder case. The proposed characteristic length for the Rayleigh number is the fin pitch while that for the Nusselt number is mean flow length, defined as half the perimeter of the mean radial position inside the flow region bounded by the tube surface and two adjacent fins. The flow is regarded as laminar, which covers heat exchangers from a single horizontal cylinder to infinite parallel disks. Consequently, the result of curve fitting for the experimental data shows the reasonable physical interpretation as well as the good quantitative agreement with the correction factors.
Investigation of the Use of an Inorganic Aqueous Solution in Copper-Made Phase-Change Heat Transfer Devices
Authors: Yao Qi , Supowit Jacob , Catton Ivan
Published: October 2017

A novel inorganic aqueous solution (IAS) is shown to have a better heat transfer performance than water when used as the working fluid in copper-made phase-change heat transfer devices. First, the physical properties of IAS are measured and compared to those of water. Another, a chemical analysis is performed, and the chemical reactions involved between IAS and the copper surface are listed and categorized by their contributions to the heat transfer performance. In addition, a capillary rise test is performed to show how each chemical contributes to the improvement of the surface wettability. Last, using IAS in copper-made phase-change heat transfer devices is discussed, and the main focus is how IAS improves the heat transfer performance by a smaller thermal resistance and a larger critical heat flux. The conclusion is validated by thermo-siphon tests at different inclination angles.
Accelerated Thermal Simulation for Three-Dimensional Interactive Optimization of Computer Numeric Control Sheet Metal Laser Cutting
Authors: Mejia Daniel , Moreno Aitor , Arbelaiz Ander , Posada Jorge , Ruiz-Salguero Oscar , Chopitea Raúl
Published: October 2017

In the context of computer numeric control (CNC)-based sheet metal laser cutting, the problem of heat transfer simulation is relevant for the optimization of CNC programs. Current physically based simulation tools use numeric or analytic algorithms which provide accurate but slow solutions due to the underlying mathematical description of the model. This paper presents: (1) an analytic solution to the laser heating problem of rectangular sheet metal for curved laser trajectories and convective cooling, (2) a graphics processing unit (GPU) implementation of the analytic solution for fast simulation of the problem, and (3) an integration within an interactive environment for the simulation of sheet metal CNC laser cutting. This analytic approach sacrifices the material removal effect of the laser cut in the favor of an approximated real-time temperature map on the sheet metal. The articulation of thermal, geometric, and graphic feedback in virtual manufacturing environments enables interactive redefinition of the CNC programs for better product quality, lower safety risks, material waste, and energy usage among others. The error with respect to finite element analysis (FEA) in temperature prediction descends as low as 3.5%.
Theoretical and Numerical Models to Predict Fracking Debonding Zone and Optimize Perforation Cluster Spacing in Layered Shale
Authors: Wang Tao , Liu Zhanli , Gao Yue , Zeng Qinglei , Zhuang Zhuo
Published: October 2017

Shale is a typical layered and anisotropic material whose properties are characterized primarily by locally oriented anisotropic clay minerals and naturally formed bedding planes. The debonding of the bedding planes will greatly influence the shale fracking to form a large-scale highly permeable fracture network, named stimulated reservoir volume (SRV). In this paper, both theoretical and numerical models are developed to quantitatively predict the growth of debonding zone in layered shale under fracking, and the good agreement is obtained between the theoretical and numerical prediction results. Two dimensionless parameters are proposed to characterize the conditions of tensile and shear debonding in bedding planes. It is found that debonding is mainly caused by the shear failure of bedding planes in the actual reservoir. Then the theoretical model is applied to design the perforation cluster spacing to optimize SRV, which is important in fracking. If the spacing is too small, there will be overlapping areas of SRV and the fracking efficiency is low. If the spacing is too large, there will be stratum that cannot be stimulated. So another two dimensionless parameters are proposed to evaluate the size and efficiency of stimulating volume at the same time. By maximizing these two parameters, the optimal perforation cluster spacing and SRV can be quantitatively calculated to guide the fracking treatment design. These results are comparable with data from the field engineering.
Microgripper-Embedded Fluid Fingertip-Enhancing Positioning and Holding Abilities for Versatile Grasping
Authors: Nishimura Toshihiro , Fujihira Yoshinori , Watanabe Tetsuyou
Published: October 2017

This paper presents a novel fingertip system with a two-layer structure for robotic hands. The outer part of the structure consists of a rubber bag filled with fluid, called the “fluid fingertip,” while the inner part consists of a rigid link mechanism called a “microgripper.” The fingertip thus is a rigid/fluid hybrid system. The fluid fingertip is effective for grasping delicate objects, that is, it can decrease the impulsive force upon contact, and absorb uncertainties in object shapes and contact force. However, it can only apply a small grasping force such that holding a heavy object with a robotic hand with fluid fingertips is difficult. Additionally, contact uncertainties including inaccuracies in the contact position control cannot be avoided. In contrast, rigid fingertips can apply considerable grasping forces and thus grasp heavy objects effectively, although this makes delicate grasping difficult. To maintain the benefits of the fluid fingertip while overcoming its disadvantages, the present study examines passively operable microgripper-embedded fluid fingertips. Our goal is to use the gripper to enhance the positioning accuracy and increase the grasping force by adding geometrical constraints to the existing mechanical constraints. Grasping tests showed that the gripper with the developed fingertips can grasp a wide variety of objects, both fragile and heavy.
Electrochemical Corrosion Finite Element Analysis and Burst Pressure Prediction of Externally Corroded Underground Gas Transmission Pipelines
Authors: Gadala Ibrahim M. , Abdel Wahab Magd , Alfantazi Akram
Published: October 2017

An integrative numerical simulation approach for pipeline integrity analysis is presented in this work, combining a corrosion model, which is the main focus of this paper, with a complementary structural nonlinear stress analysis, using the finite element method (FEM). Potential distributions in the trapped water existing beneath pipeline coating disbondments are modeled in conjunction with reaction kinetics on the corroding exposed steel surface using a moving boundary mesh. Temperature dependencies (25 °C and 50 °C) of reaction kinetics do not greatly affect final corrosion defect geometries after 3-yr simulation periods. Conversely, cathodic protection (CP) levels and pH dependencies within the near-neutral pH range (6.7–8.5) strongly govern depth profiles caused by corrosion, reaching a maximum of ∼3 mm into the pipeline wall. A 0.25 V amplification of CP potential combined with a 0.5 mm widening in disbondment opening size reduces defect penetration by almost 30%. Resulting corrosion defect geometries are used for stress examinations and burst pressure evaluations. Furthermore, nonlinear elastic–plastic stress analysis is carried out using shell elements in order to predict the burst pressure of corroded pipes. Corrosion is modeled by reducing the stiffness of a damaged element that has the dimensions of the defect. The predicted burst pressures are in good agreement with those obtained using an experimental-based formula.
Modeling Effective Thermal Conductivity of Thermal Radiation for Nuclear Packed Pebble Beds
Authors: Wu Hao , Gui Nan , Yang Xingtuan , Tu Jiyuan , Jiang Shengyao
Published: October 2017

In nuclear packed pebble beds, it is a fundamental task to model effective thermal conductivity (ETC) of thermal radiation. Based on the effective heat transfer cells of structured packing, a short-range radiation model (SRM) and a subcell radiation model (SCM) are applied to obtain analytical results of ETC. It is shown that the SRM of present effective heat transfer cells are in good agreement with the numerical simulations of random packing and it is only slightly higher than empirical correlations when temperature exceeds 1200 °C. In order to develop a generic theoretical approach of modeling ETC, the subcell radiation model is presented and in good agreement with Kunii–Smith correlation, especially at very high temperature ranges (over 1500 °C). Based on SCM, one-dimensional (1D) radial heat transfer model is applied in the analysis of the HTTU experiments. The results of ETC and radial temperature distribution are in good agreement with the experimental data.
Numerical Investigation of Flow Structure and Heat Transfer Produced by a Single Highly Confined Bubble in a Pressure-Driven Channel Flow
Authors: Willard John R. , Keith Hollingsworth D.
Published: October 2017

A numerical investigation of a single highly confined bubble moving through a millimeter-scale channel in the absence of phase change is presented. The simulation includes thermal boundary conditions designed to match those of completed experiments involving bubbly flows with large numbers of bubbles. The channel is horizontal with a uniform-heat-generation upper wall and an adiabatic lower boundary condition. The use of a Lagrangian framework allows for the simulation of a channel of arbitrary length using a limited computational domain. The liquid phase is a low-Reynolds-number laminar flow, and the phase interactions are modeled using the volume-of-fluid (VOF) method with full geometric reconstruction of the liquid/gas interface. Results are presented for three bubble diameters, which include two levels of confinement within the channel and two liquid flow rates. Bubble shape and speed closely match experimental observations for each bubble size and liquid flow rate. Nusselt numbers in the bubble wake for all configurations follow a power law relationship with distance behind the bubble. Important dynamical structures include a pair of vortical structures at the rear of the bubble associated with the primary heat transfer enhancement and a pair of prominent liquid jets oriented in the transverse direction on either side of the bubble.
Estimating Two Parameters From Two Complementary Transient Experiments
Authors: McMasters Robert L. , de Monte Filippo , Beck James V.
Published: October 2017

A desirable feature of any parameter estimation method is to obtain as much information as possible with one experiment. However, achieving multiple objectives with one experiment is often not possible. In the field of thermal parameter estimation, a determination of thermal conductivity, volumetric heat capacity, heat addition rate, surface emissivity and convection coefficient may be desired from a set of temperature measurements in an experiment where a radiant heat source is used. It would not be possible to determine all of these parameters from such an experiment; more information would be needed.

The work presented in the present research shows how thermal parameters can be determined from temperature measurements using complementary experiments where the same material is tested more than once using a different geometry or heating configuration in each experiment. The method of ordinary least squares is used in order to fit a mathematical model to a temperature history in each case. Several examples are provided using one-dimensional conduction experiments, with some having a planar geometry and some having a cylindrical geometry. The parameters of interest in these examples are thermal conductivity and volumetric heat capacity. Both of these parameters cannot be determined simultaneously from one experiment but the practice of using two complementary experiments allows each of the parameters to be determined.

An examination of confidence regions is an important topic in parameter estimation and this aspect of the procedure is addressed in the present work. A method is presented as part of the current research by which confidence regions can be found for results from a single analysis of multiple experiments.
Computational Study of Flow and Heat Transfer With Anti Cross-Flows (ACF) Jet Impingement Cooling for Different Heights of Corrugate
Authors: Dhanasegaran Radheesh , Pugazhendhi Ssheshan
Published: October 2017

In the present study, a flow visualization and heat transfer investigation is carried out computationally on a flat plate with 10×1 array of impinging jets from a corrugated plate. This corrugated structure is an Anti-Cross Flow (ACF) technique which is proved to nullify the negative effects of cross-flow thus enhancing the overall cooling performance. Governing equations are solved using k-ω Shear Stress Transport (SST) turbulence model in commercial code FLUENT. The parameter variation considered for the present study are (i) three different heights of ACF corrugate (C/D = 1, 2 & 3) and (ii) two different jet-to-target plate spacing (H/D = 1 & 2). The dependence of ACF structure performance on the corrugate height (C/D) and the flow structure has been discussed in detail, therefore choosing an optimum corrugate height and visualizing the three-dimensional flow phenomena are the main objectives of the present study. The three-dimensional flow separation and heat transfer characteristics are explained with the help of skin friction lines, upwash fountains, wall eddies, counter-rotating vortex pair (CRVP), and plots of Nusselt number. It is found that the heat transfer performance is high at larger corrugate heights for both the jet-to-plate spacing. Moreover, the deterioration of the skin friction pattern corresponding to the far downstream impingement zones is greatly reduced with ACF structure, retaining more uniform heat transfer pattern even at low H/D values where the crossflow effects are more dominant in case of the conventional cooling structure. In comparison of the overall heat transfer performance the difference between C/D = 3 & C/D = 2 for H/D = 2 is significantly less, thus making the later as the optimal configuration in terms of reduced channel height.
Experimental Study of a Single Microchannel Flow Under Non-Uniform Heat Flux
Authors: Eltaweel Ahmed , Baobeid Abdulla , Hassan Ibrahim
Published: October 2017

Non-uniform heat fluxes are commonly observed in thermo-electronic devices that require distinct thermal management strategies for effective heat dissipation and robust performance. The limited research available on non-uniform heat fluxes focus mostly on microchannel heat sinks while the fundamental component, i.e. a single microchannel, has received restricted attention. In this work, an experimental setup for the analysis of variable axial heat flux is used to study the heat transfer in a single microchannel with fully developed flow under the effect of different heat flux profiles. Initially a hot spot at different locations, with a uniform background heat flux, is studied at different Reynolds numbers while varying the maximum heat fluxes in order to compute the heat transfer in relation to its dependent variables. Measurements of temperature, pressure, and flow rates at a different locations and magnitudes of hot spot heat fluxes are presented, followed by a detailed analysis of heat transfer characteristics of a single microchannel under non-uniform heating. Results showed that upstream hotspots have lower tube temperatures compared to downstream ones with equal amounts of heat fluxes. This finding can be of importance in enhancing microchannel heat sinks effectiveness in reducing maximum wall temperatures for the same amount of heat released, by redistributing spatially fluxes in a descending profile.
Thermal Analysis of the Sensor in a Radiation Budget Instrument
Authors: Pfab Jonathan F. , Vick Brian , Mahan J. Robert , Priestley Kory
Published: October 2017

Earth radiation budget instruments (RBI) are devices designed to study global climate change. These instruments use telescopes mounted on low earth orbit satellites to measure emitted and reflected solar radiation from the earth. Radiation is measured by virtue of temperature changes caused by absorbed radiation from the earth scans on the surface of a delicate gold-black detector. In this paper a thermal model of the detector in a typical radiation budget instrument is formulated.

A numerical solution is developed using a complex model building procedure. The idea is to split complex physical processes into simpler, individual physical processes. The basic procedure is to solve for each individual physical process in a numerically stable and efficient manner, and then assemble these processes in a cascading sequence to form a complete numerical solution of a complex model. The major advantage is that complicated mathematical models can be solved as a sequence of much simpler and less computationally intensive processes.

Parameter studies are performed on the numerical accuracy, conduction effects, initial conditions, boundary conditions due to contact with adjoining surfaces, radiation exchange with surfaces optically visible to the detector, and the volumetric heat source due to absorbed radiation from the earth scene. Extremely accurate temperature predictions are required due to the low signal to noise ratio. It is found that predictions are most sensitive to the amount and distribution of irradiation on the detector surface, which is computed independently using a Monte Carlo ray trace method.
Synchronized High-Speed Video and Infrared Thermometry Study of Bubble Dynamics During Nucleate Boiling of Nanoemulsion
Authors: Stephenson Robert , Xu Jiajun
Published: October 2017

In this study, a combination of synchronized high-speed video (HSV) and infrared (IR) thermography was used to characterize the nucleation, growth and detachment of bubbles generated during nucleate boiling inside the nanoemulsion fluid. The Ethanol/Polyalphaolefin nanoemulsion fluid was formed by dispersing ethanol nanodroplets into base fluid Polyalphaolefin, in which these nanodroplets can serve as the pre-seed boiling nuclei. With this unique combination, it allows controlled nucleation, time-resolved temperature distribution data for the boiling surface and direct visualization of the bubble cycle to track bubble nucleation and growth. Data gathered included measurements of bubble growth versus time, as well as 2D temperature history of the heater surface underneath the bubbles. Our findings demonstrate a significant difference of bubble dynamics between the nanoemulsion fluid and pure ethanol, which may also account for the substantial increase in heat transfer coefficient and critical heat flux of nanoemulsion fluid. It is also observed here that the bubbles occurred inside the nanoemulsion fluid appear to be more uniform and two orders-of-magnitude larger in size. While the growth rate of the bubbles inside pure ethanol was found to be heat diffusion controlled at a coefficient around ½, which however, dropped to be around 0.3 for nanoemulsion fluid. Further study on this unique system will help reveal its heat transfer mechanisms.
Convective Heat Transfer of Ethanol/Polyalphaolefin Nanoemulsion Inside Circular Minichannel Heat Exchanger
Authors: Zewede Fana , Argaw Henok , Tran Thanh , Xu Jiajun
Published: October 2017

This work experimentally studied the convective heat transfer characteristics of a novel nanostructured heat transfer fluid: “Ethanol/Polyalphaolefin(PAO) nanoemulsion fluids” flowing through a heat exchanger made of twelve circular minichannels. Ethanol/PAO nanoemulsion fluid is a thermodynamically stable system formed by dispersing ethanol into a mixture of PAO and surfactants, in which the ethanol added inside forms self-assembled nanodroplets of tens of nanometers in diameter. These ethanol nanodroplets can serve as pre-seed boiling nuclei at elevated temperature. The Reynolds number was varied between 140 and 1200 to maintain the entire range of flow regime remained at laminar flow for both single- and two-phase convective heat transfer experiments. Pure PAO was also tested under same conditions and used as baseline data for comparison.

It is found that: for single phase flow, there is no significant increase in Nusselt number of Ethanol/PAO nanoemulsion compared to that of PAO fluid in laminar flow regime. However, when the nucleation of ethanol nanodroplets inside the nanoemulsion fluid was initiated, it showed a substantial increase in heat transfer coefficient compared to that of PAO fluid: a 75% enhancement can be achieved under current test conditions. While its mechanism is not completely clear yet, it is believed that such an effect is likely related to the latent heat carried by ethanol bubbles, as well as the increased turbulence and mixing generated during the two-phase flow of nanoemulsion which can increase the heat transfer rate.
Performance of a Pulsating Heat Pipe Fabricated With a 3-D Printer
Authors: Koito Yasushi , Kawaji Masahiro
Published: October 2017

A pulsating heat pipe (PHP) was fabricated by a 3-D printer, and its heat transfer characteristics were investigated by experiments. A graphene-laden PLA (PolyLactic Acid) filament was used as a 3-D printing material. Ten square channels having a cross section of 1.5 mm × 1.5 mm and a length of 80 mm were made inside the PHP and the ends of channels were connected. Since the graphene-laden PLA filament allows electric currents to pass through, the 3-D printed PHP was electroplated by copper to maintain its airtightness. Ethanol was used as the working fluid. The filling ratio of the working fluid was 50 %. In experiments, an evaporator section of the PHP was heated by a heater and a condenser section was cooled using a water-cooling jacket. The heater power was changed from 2.0 W to 8.0 W while the cooling water temperature and its flow rate were kept at 4.0 °C and 0.25 LPM, respectively. The transient temperature distribution of the PHP was measured by thermocouples. Moreover, because the graphene-laden PLA is nontransparent, an X-ray imaging system was also employed to observe the two-phase flow phenomena occurring in channels of the PHP. From the experimental results, the continuous heat transport from the evaporator to the condenser section of the PHP was confirmed with vapor-liquid two-phase flow characteristics observed inside the channels.
Atmospheric Water Harvesting Systems for Utilization of Waste Natural Gas From Oilfields and Landfills
Authors: Wikramanayake Enakshi , Ozkan Onur , Bahadur Vaibhav
Published: October 2017

Excess natural gas produced in oilfields is routinely flared due to the absence of alternative uses. Similarly, landfills emit large quantities of methane, which is primarily flared or vented. Both these activities result in large scale energy waste and undesired methane and carbon dioxide emissions. This work examines the benefits of using excess natural gas to harvest atmospheric moisture. Natural gas-powered refrigeration systems can enable large scale dehumidification via condensation. The harvested water can be used for water-intensive operations like hydraulic fracturing, drilling and waterflooding in nearby oilfields. This solution thus addresses the issues of energy waste, water and greenhouse gas emissions A first-order model is used to estimate the water harvest, based on the gas flow rate, ambient weather and the refrigeration system. The benefits of flared gas-powered water harvesting are quantified for the Eagle Ford (Texas) and the Bakken (North Dakota) Shales, which account for the bulk of US flaring. The benefits of landfill gas-powered water harvesting are quantified for the Barnett (Texas), and Monterey (California) Shales, which can be served by 30 and 15 landfills, respectively. Overall, flared gas utilization for water production can meet 15% and 60% of the annual water requirements of the Eagle Ford and Bakken Shales, respectively. The water harvested using landfill gas (from nearby landfills) can meet 22% and 73% of the annual water requirements of the Barnett and Monterey Shales, respectively. This technology will also eliminate millions of trucking trips to transport water. Overall, this waste-to-value concept has global relevance, since a combination of excess gas availability, water scarcity and hot-humid conditions is common in many regions of the world.
Potential for Passive Radiative Cooling by PDMS Selective Emitters
Authors: Czapla Braden , Srinivasan Arvind , Yin Qingtian , Narayanaswamy Arvind
Published: October 2017

The scalability and implementation of selective emitters in passive radiative cooling applications are limited by the high fabrication costs due to the complexity of these structures. The usage of commercially available polymers in selective emitters holds potential in lowering the cost of radiative cooling solutions. In this work, we demonstrate that thin films of polydimethyl-siloxane (PDMS) on aluminum substrates act as radiative coolers by selectively emitting in the wavelength range of 8 μm to 13 μm, where the Earth’s atmosphere is highly transparent. We also show that our device can achieve passive cooling up to 12 °C below the ambient temperature under the night sky. This suggests that PDMS, especially due to its ease of deposition, may be a viable selective emitter in passive radiative cooling applications.
Impact of Moisture on the Thermal Properties of Nanoparticle-Based Materials
Authors: Elsahati Muftah O. , Richards Robert F.
Published: October 2017

Nanoparticle packed beds are of interest because of their extremely low thermal conductivities. However, thermal nanoparticle packed beds exposed to ambient air show unusual increases in conductivity. The causes for that increase in conductivity are examined with experimental measurements. Sorption isotherms and thermal conductivity measurements for 20 nm and 200 nm silica nanoparticle packed beds exposed to a range of humidity are presented. Both nanoparticle beds demonstrate hygroscopic behavior, absorbing significant amounts of moisture upon exposure to humid air. The thermal conductivity of the nanoparticle beds are shown to increase monotonically with relative humidity. More than an order of magnitude increase in conductivity is seen, with a large increase at very low humidity. The measurements illuminate the effects of moisture on the thermal properties of nanoparticle-based materials.
Comparison of 30 Boiling and Condensation Correlations for Two-Phase Flows in Compact Plate-Fin Heat Exchangers
Authors: Li Wenhai , Alabi Ken , Ladeinde Foluso
Published: October 2017

Over the years, empirical correlations have been developed for predicting saturated flow boiling [1–15] and condensation [16–30] heat transfer coefficients inside horizontal/vertical tubes or micro-channels. In the present work, we have examined 30 of these models, and modified many of them for use in compact plate-fin heat exchangers. However, the various correlations, which have been developed for pipes and ducts, have been modified in our work to make them applicable to extended fin surfaces. The various correlations have been used in a low-order, one-dimensional, finite-volume type numerical integration of the flow and heat transfer equations in heat exchangers. The NIST’s REFPROP database [31] is used to account for the large variations in the fluid thermo-physical properties during phase change. The numerical results are compared with Yara’s experimental data [32]. The validity of the various boiling and condensation models for a real plate-fin heat exchanger design is discussed. The results show that some of the modified boiling and condensation correlations can provide acceptable prediction of heat transfer coefficient for two-phase flows in compact plate-fin heat exchangers.
Experimental Study of Condensation Flow Inside Horizontal Smooth, Herringbone and Three Enhanced Surface Tubes
Authors: Yan Xiaolong , Li Wei , Tang Weiyu , Zhu Hua , Sun Zhijian , Liu Zhichun , Liu Fu , Kukulka David
Published: October 2017

Enhanced condensation heat transfer of two-phase flow on the horizontal tube side receives more and more concerns for its fundamentality and importance. Experimental investigations on convective condensation were performed respectively in different horizontal tubes: (i) a smooth tube (11.43 mm, inner diameter); (ii) a herringbone tube (11.43 mm, fin root diameter); and (iii) three enhanced surface (EHT) tubes (11.5 mm, equivalent inner diameter): 1EHT tube, 2EHT-1 tube and 2EHT-2 tubes. The surface of EHT tubes is enhanced by arrays of dimples with the background of petal arrays. Experiments were conducted at a saturation temperature of approximately 320 K; 0.8 inlet quality; and 0.2 outlet quality; 72–181 kg·m−2·s−1 mass flux using R22, R32 and R410A as the working fluid. The refrigerant R32 presents great heat transfer performance than R410A and R22 at low mass flux due to its higher latent heat of vaporization and larger thermal conductivity. The heat enhancement ratio of the herringbone tube is 2.72–2.82, rated number one. The primary dimples on the EHT tube increase turbulence and flow separation, and the secondary petal pattern produce boundary layer disruption to many smaller scale eddies. The 2EHT tubes are inferior to the 1EHT tube. A performance factor is used to evaluate the enhancement effect except of the contribution of area increase.
Temperature Measurement of Microscale Electronic Devices With 3D Thermoreflectance Imaging
Authors: Zhang Hongjie , Wen Sy-Bor
Published: October 2017

3D thermoreflectance (TR) imaging utilizing light field camera is proposed and developed in this study. With the capability of resolving light direction and intensity simultaneously, we are able to measure directional TR signal from tilted or curved surfaces through the light field camera. Once the directional TR coefficients of the target surface is collected, we can then estimate the temperature distributions of tilted or curved surfaces based on the measured directional TR signal. This new 3D TR imaging approach has the potential to measure temperature of surfaces with different configurations as long as the TR signal is strong enough. In this technical paper, we first present basic principles of 3D TR imaging techniques based on light field theory. The construction and calibration procedures of the resulting 3D TR imaging system are then presented. At the end of the technical paper we present steady-state surface temperature measurements of microscale electronic devices including an infrared laser diode and a gold wire with the current 3D TR imaging system. The obtained temperature distributions of the microscale samples showing high temperature and spatial resolutions in real-time temperature measurement on the 3D surfaces that cannot be achieved with traditional 2D TR imaging techniques.
Numerical Analysis of Thermal Transport in Nano Fluidic Porous Filled Heat Exchangers for Electronics Cooling
Authors: Zing Carlos , Mahjoob Shadi
Published: October 2017

The exponential growth in electronic power has brought amazing technology but with it also comes a burden in high heat production that threatens the safety of the product since electronics’ failure rate increases by its operating temperature. As such, cooling techniques have a key role to keep the temperature of electronics devices, such as processors, memory and graphics chips, below a maximum operating temperature. In this work, a porous filled heat exchanger has been numerically modeled to investigate the cooling effectiveness and temperature distribution on the base of the heat exchanger subjected to high heat flux leaving these devices. The effects of different nanofluid coolants (0.75% double walled carbon nanotube in water (DWCNT), 1% alumina in water, and 1% diamond in 20:80 ethylene glycol/water), porous materials (copper and annealed pyrolytic graphite (APG)), and porosity values are investigated. The coolant enters from an inlet channel normal to the base, moves through the porous field, and then leaves the heat exchanger through two opposite exit channels parallel to the base. The study is performed for two and three dimensional geometries in which two different designs are studied for 3D cases. One of the designs has a rectangular cross sectional inlet channel (along transverse direction) and the other design has square one. The results indicate that utilizing APG porous matrix, for all studied coolants of pure water and water based nano fluidics, improves substantially the cooling of the base of the heat exchanger in 2D and 3D with rectangular inlet. The results also show that utilizing carbon nanofluids (DWCNT) as coolant for high porosity structures, in both copper and APG porous matrices, improves cooling efficiency and temperature uniformity over the base, for all 2D and 3D cases. The effect of inlet channel geometry, square and rectangular, is also investigated for either similar velocity or similar mass flow rate at the inlet channel entrances.
Numerical Investigation on a Modified “Piccolo Tube” System in Aircraft Anti-Icing
Authors: Buonomo Bernardo , Diana Alessandra , Manca Oronzio , Nardini Sergio
Published: October 2017

In this work, an anti-icing “Piccolo tube” system is numerically analyzed, in order to investigate the efficiency of hot air impinging jets on internal wing surface. The model is two-dimensional and it is composed by the wing profile and an external volume. External air is considered a mixture, composed by dry air and water-vapor. A steady state problem with standard k-ε model is assumed. Numerical simulations are performed considering an average coefficient on the external surface and thermofluidynamic field inside the wing due to the anti-icing system. Numerical solutions are carried out by means of the Ansys-FLUENT code. Simulations are performed considering two values of the angle of attack, 0° and 4°, and two Mach number values, 0.576 and 0.700, related to the internal flow. esults are presented in terms of velocity and temperature fields, wall temperature profiles along the wing surfaces. As comparison, a case with only dry air in the external domain is performed. Results indicate that in presence of droplets the anti-icing system is less efficient than in the ideal case of dry air. Furthermore, a larger angle of attack improves the performance of the anti-icing system, but a larger Mach number deteriorates it.
Critical Heat Flux for Convective Boiling in Mini-Tube due to Power Transient
Authors: Shibahara Makoto , Fukuda Katsuya , Liu Qiusheng , Hata Koichi
Published: October 2017

Critical heat flux (CHF) of convective boiling in a mini-tube due to power transient was measured. A platinum tube with an inner diameter of 1.0 mm was heated exponentially by a direct current power supply as Joule heating. The heated length of the platinum tube was 40.9 mm. The platinum tube was mounted vertically in the water-loop apparatus which consisted of a circulating pump, a pre-heater, a flow mater, a pressurizer, a cooler and a test section. The deionized water was pressurized by the pressurizer up to approximately 800 kPa to measure CHFs at the high subcooling. The upward flow velocity in the platinum tube was ranged from 5 to 11 m/s. The inlet subcooling was ranged from 92 to 117 K. The heat generation rate was controlled with exponential functions. The e-folding time of the heat generation rate was ranged from 30 ms to 18 s. As an experimental result, it was found that the CHFs increased with increasing the flow velocity and the inlet subcooling. The CHF also increased with decreasing the e-folding time of the heat generation rate. Since the heat generation rate of the platinum tube increased rapidly under the power transient condition, it was considered that the heat flux of the platinum tube increased until the vapor blanket covered the heated surface of the platinum tube.
Polarized Radiative Transfer in Anisotropic Disordered Media With Short-Range Order
Authors: Wang B. X. , Zhao C. Y.
Published: October 2017

The aim of this study is to present a general method to investigate radiative transfer in disordered media with a subwave-length, anisotropic short-range order and provide a fundamental understanding on the interplay between polarized radiative transfer and microstructural anisotropy as well short-range order. We show the anisotropy of short-range order, described by an anisotropic correlation length in Gaussian random permittivity model, induces a significant anisotropy of radiative properties. Here the photon scattering mean free path is derived using the Feynman diagrammatic expansion of self-energy, and the transport mean free path and phase function are calculated based on the diagrammatic representation of the irreducible vertex in the Bethe-Salpeter equation. We further consider the transport of polarized light in such media by directly solving Bethe-Salpeter equation (BSE) for photons, without the use of traditional vector radiative transfer equation (VRTE). The present method advantageously allows us to elegantly relate anisotropic structural parameters to polarized radiative transport properties and obtain more fundamental physical insights, because the approximations in all steps of our derivation are given explicitly with reasonable explanations from the exact ab-initio BSE. Moreover, through a polarization eigen-channel expansion technique for intensity tensor, we show that values of transport mean free path in different polarization eigen-channels are rather different, which are also strongly affected by structural anisotropy and short-range order. As a conclusion, this study depicts some fundamental physical features of polarized radiative transfer in disordered media, and is also valuable for potential applications of utilizing anisotropic short-range order in disordered media in manipulation of polarized radiative transfer.
Computational Modeling of the Effect of Flue-Wall Deformation on the Carbon Anode Quality for Aluminum Production
Authors: Zaidani Mouna , Abu Al-Rub Rashid , Tajik Abdul Raouf , Shamim Tariq
Published: October 2017

The flue-wall deformation during the service life of carbon anode baking furnaces has a substantial impact on the carbon anode quality (i.e., thermal, electrical, and mechanical properties) used in the reduction cell of aluminum production. Deformation of the furnace flue-walls, which is one critical mode of furnace aging, leads among others to inhomogeneous baking of the anodes and consequently to a deterioration of the resulting anode quality. This paper focuses on the development of a 3D multi-physics computational model, which is able to take into account a large number of physical phenomena and parameters that play a role in the baking process while considering different levels of the flue-wall deformation. In fact, this 3D model takes into account the thermo-hydro-mechanical coupling due to coupled fluid flow and transient heat transfer, packing coke load and the thermal expansion, and enable us to analyze the influence of these parameters on the resistance to deflection of the flue-walls, and ultimately improved baking process and furnace geometry can be proposed The developed model can predict the anode temperature distribution, creation of hot spot and anode overbaking in certain area as a function of the flue wall deformation mode. By developing this tool, we can effectively predict the deformable flue wall reliability under varying operating conditions, and provide useful insights on enhancing the long-term structural integrity through furnace retrofitting or design adjustment.
Thermal Radiation From Microsphere Photolithography Patterned Metasurfaces
Authors: Qu Chuang , Kinzel Edward C.
Published: October 2017

Frequency-Selective Surfaces (FSS) type metasurfaces consist of periodic arrays of antenna elements. They can be scaled from microwave frequencies to the infrared wavelengths where they allow the scattering response to be engineered. This includes the spectral absorptance/emittance. At IR wavelengths, the features sizes of the metasurface are sub-micron which poses manufacturing issues for the meter squared scales required for most heat transfer applications. In this paper, we investigate the use of Microsphere Photolithography for creating spectrally selective metasurfaces. This approach uses a self-assembled array of microspheres as a lens array to focus a lattice of photonic jets into photoresist. These can be used with lift-off to create metal-insulator-metal (MIM) or even five-layer of resonant structures. We study the design constraints and synthesize a broadband emitter in the mid-infrared. The spectral absorptance is measured experimentally using FTIR. The structures are then tested at moderate temperatures to demonstrate the ability to affect surface temperature/heat flux in practical applications.