Thermal Footprint Research Articles

Evaporation of a liquid film deposited on a capillary heated tube: Experimental analysis by infrared thermography of its thermal footprint

Evaporation of thin film deposited downstream menisci of slug flows is of major importance in the two-phase heat transfer phenomena occurring inside micro/mini-channels or in pulsating heat pipes. The aim of this study is consequently to analyze, by means of experimental infrared thermography, the heat transfers involved in the motion of a semi-infinite slug flow (one liquid slug followed by one single vapour bubble) in a heated capillary copper tube. Between the liquid and vapour phases the meniscus deposits a thin liquid film at the wall; this film brings about intense heat transfer at the wall by evaporation, leading to a highly significant decrease of external wall temperature. This phenomenon is better understood using infrared temperature measurements, which help to analyze the heat transfer characteristics present during evaporation. Given the highly transient nature of the process, the thickness of the deposited film is a parameter of major importance. After validation of the measurement method with tests involving no fluid or only liquid flow, the experimental results, with water being used as a working fluid, are compared to those of a numerical thermal model of which the parameters are well-known. The results drawn from the model rather accurately predict those obtained in the experiments and facilitate further analysis by presenting, for example, the evolution of liquid film thickness or heat flux density in conjunction with the wall temperature fields. It has been found that the thin film length is a first-order function of the initial thickness of the deposited film, the meniscus velocity, and the heat flux density at the wall, including the release of stored heat energy in the wall that is caused by the temperature difference before and after passage of the meniscus. This study represents a step towards better understanding the local physical phenomena governing the operation of pulsating heat pipes.

Microstructural, optical and thermal characterization of synthetic clay as a passive cooling medium

This work reports on assessing the suitability of synthetic clay as a porous medium that promotes evaporative cooling for various applications, especially temperature control of photovoltaic modules. When applied to the back of these modules and supplied with a fine mist spray of water, clay reduces the operational temperatures of photovoltaic modules by 30–40°C, depending on weather conditions. The characterization of the microstructure (crystallinity, pore size and distribution) and composition of the clay is essential in understanding the enhancements that the clay provides for evaporation. A cooling element made from the clay was tested to quantify the evaporative portion of heat transfer, while spectroscopic profiles of two photovoltaic modules under typical operational conditions were tested for thermal footprint differences. The results indicate a good match between obtained SEMs and porosity tests in estimating average pore sizes responsible for enhancing the evaporative cooling and thus lowering thermal emittance from photovoltaic modules, improving their efficiency for given ambient conditions.

Thermal characterizations of a large-format lithium ion cell focused on high current discharges

The thermal behavior of a large-format lithium ion cell has been investigated during measurements on cell and battery level. High current discharges up to 300 A are the main topic of this study. This paper demonstrates that the temperature response to high current loads provides the possibility to investigate internal cell parameters and their inhomogeneity. In order to identify thermal response caused by internal cell processes, the heat input due to contact resistances has been minimized. The differences between the thermal footprint of a cell during cell and battery measurements are being addressed. The study presented here focuses on the investigation of thermal hot and cold spots as well as temperature gradients in a 50 Ah pouch cell. Furthermore, it is demonstrated that the difference between charge and discharge can have significant influence on the thermal behavior of lithium ion cells. Moreover, the miscellaneous thermal characteristics of differently aged lithium ion cells highlight the possibility of an ex-situ non-destructive post-mortem-analysis, providing the possibility of a qualitative and quantitative characterization of inhomogeneous cell-aging. These investigations also generate excellent data for the validation and parameterization of electro-thermal cell models, predicting the distribution of temperature, current, potential, SOC and SOH inside large-format cells.

Sensor Technologies and Applications for Smart Roads and Smart Buildings

Smart System Integration (SSI) principles currently have widespread applications in the societal infrastructure sector addressing critical needs of safety, quality of environment and energy conservation applications. This is easy to understand since SSI approaches provide a small and cost-effective approach to monitoring and controlling the many environments surrounding us vis-à-vis the utilization of broad selection of sensors in their front end. In addition to these front end sensors, Smart Systems also include a diverse array of other functions including signal conditioning circuits (e.g. ASICs with embedded microcontrollers), energy sources, and communication back ends….either wired or wireless and all assembled and packaged. The sensors, when linked together to form a network are frequently referred to as Wireless Autonomous Sensor Networks (WASNs).Major opportunities for these Smart System Integration solutions currently exist in structural bridge monitoring. In the US alone, the American Society of Civil Engineers (ASCE) has recently reported that there are over 583,000 bridges and of these over 25% are structurally deficient or functionally obsolete. ASCE also reports that of the 76,926 dams that exist in the US of which 1,819 have high hazard potential. Various organizations including the University of Michigan and the University of Illinois have been developing solutions to monitor these and other civil engineering structures including dams, buildings, levees and pipelines.Additionally, infrastructure monitoring has expansive applications in building monitoring from a structural, energy management, security and quality of environment perspectives. The US census reported that there are over 160 million households in the US and it is reported that there are 1.7 billion households internationally. Most provide heating (and many also provide cooling) to their inhabitants. This is in addition to commercial buildings. WASNs are critical to the efficient monitoring and control of these systems especially in these times of minimizing the systems’ thermal footprint and minimizing energy consumption.This presentation will address several of the systems currently in use and/or under development at commercial organizations and research facilities in the US to be able to monitor and control these infrastructure applications. Applications include bridge monitoring, smart roads (traffic control and parking) and smart buildings. We will present functional analysis of the systems, address specific elements of the systems (with a focus on sensors) and provide measured results to establish the feasibility and efficacy of such approaches.

Errata to: “On the shear stress and thermal footprints of turbulent spots at zero pressure gradient”

Errata to: “On the shear stress and thermal footprints of turbulent spots at zero pressure gradient”

Cross-Linked Carbon Nanotube Heat Spreader

ABSTRACTAmong the exceptional properties of isolated individual carbon nanotubes (CNTs), exceptional thermal conductivity along their axis has been demonstrated, However they have also shown poor thermal transfer between adjacent CNTs. Thick bundles of aligned CNTs have been used as heat pipes, but the thermal input and output power densities are the same, providing no heat spreading effect. We demonstrate the use of energetic argon ion beams to join overlapping CNTs in a thin film to form an interpenetrating network with an isotropic thermal conductivity of 2150 W/m K. Such thin films may be used as heat spreaders to enlarge the thermal footprint of laser diodes and CPU chips, for example, for enhanced cooling. At higher ion energies and fluence, the CNTs appear to collapse and reform, aligned parallel to the ion beam axis, and form dense high aspect ratio tapered structures. The high surface area of these structures lends themselves to applications in energy storage, for example. We consider the mechanisms of energetic ion interaction with CNTs and junction formation of two overlapping CNTs during the subsequent self-healing process, as well as the formation of high aspect ratio structures under more extreme conditions

The Carbon Footprint Analysis of Thermal Power Plants

Thermal power plant is the main CO2 emission source in China. This paper discusses the carbon footprint of a thermal power plant in Liaoning province of China based on LCA (Life Cycle Assessment. The reviewed thermal power plants total carbon footprint is about 6.52 million tons, of which 90.23% are from fuel combustion. The onsite emission is 5.91 million tons which depends on the power plants technology level and energy efficiency. In order to alleviate carbon emissions at the power enterprise level, an integrated effort should be taken, including the optimization of energy structures, improvement of energy efficiency and technology level. Recommendations for thermal power plant management are that companies should make full use of geographical advantages and adopt high-quality fuels actively.

On the shear stress and thermal footprints of turbulent spots at zero pressure gradient

Turbulent spots were artificially created in a flat plate boundary layer and visualized by shear-stress sensitive and temperature-sensitive liquid crystals. These procedures employ surface shear stress and temperature as passive tracers to provide insights into the structure of a turbulent spot at the near-wall region. The liquid crystals successfully displayed the “true” footprints of the spots. Quantitative data, such as the heat transfer rate, were likewise provided. The results of the present study prove the existence of a spanwise overhang on a turbulent spot, which could produce important implications on transitional modeling in gas turbine industry.

Analyzing the footprints of near‐surface aqueous turbulence: An image processing‐based approach

AbstractIn this contribution, a detailed investigation of surface thermal patterns on the water surface is presented, with wind speeds ranging from 1 to 7 m s − 1 and various surface conditions. Distinct structures can be observed on the surface—small‐scale short‐lived structures termed fish scales and larger‐scale cold streaks that are consistent with the footprints of Langmuir circulations. The structure of the surface heat pattern depends strongly on wind‐induced stress. Consistent behavior regarding the spacing of cold streaks can be observed in a range of laboratory facilities when expressed as a function of water‐sided friction velocity, u * . This behavior systematically decreased until a point of saturation at u * = 0.7 cm/s. We present a new image processing‐based approach to the analysis of the spacing of cold streaks based on a machine learning approach to classify the thermal footprints of near‐surface turbulence. Comparison is made with studies of Langmuir circulation and the following key points are found. Results suggest a saturation in the tangential stress, anticipating that similar behavior will be observed in the open ocean. A relation to Langmuir numbers shows that thermal footprints in infrared images are consistent with Langmuir circulations and depend strongly on wind wave conditions.

Recent Developments in Plate Exchangers—Ammonia/Carbon Dioxide Cascade Condensers

The use of carbon dioxide and ammonia in low temperature cascade systems is gaining momentum in the industrial refrigeration market. The use of a plate exchanger as cascade condenser is a viable option due to the high thermal efficiency and smaller footprint characteristics of such exchangers. There is a lack of reliable data in the open literature on condensation of carbon dioxide and evaporation of ammonia in such heat exchangers. This article presents the latest research on condensation of carbon dioxide and evaporation of ammonia in various corrugated plate exchangers at different saturation temperature and heat/mass flux. The data are reduced to generalized empirical correlations to be used as design tools by engineers. It also discusses the mechanical aspects of plate exchanges and their suitability in cascade systems.

Arrays of low‐temperature plasma probes for ambient ionization mass spectrometry

This paper reports the development of arrays of capillary-based low-temperature plasma (LTP) probes for direct sample analysis. These probe arrays allow a higher surface area to be analyzed, increasing the throughput in large sample analysis. Validation of these arrays was performed on illicit, cathinone-based drugs marketed as 'bath salts'. LTP arrays consisting of 1, 7, and 19 probes were constructed with quartz capillaries and held together with silver epoxy resin adhesive. Three drugs, mephedrone, methylone and methylenedioxypyrovalerone, were analyzed with each plasma ion source and an ion trap mass spectrometer in full MS and in MS/MS positive ion mode. Chemical and thermal footprints were determined for each source. A reactive probe design was used to inject trifluoroacetic anhydride directly into the plasma stream for on-line derivatization. Small LTP probes and bundled arrays provide low picogram level limits of detection for mephedrone, methylone and methylenedioxypyrovalerone. Bundling the probes together in larger arrays increases the surface area analyzed by a factor of ten, while maintaining surface temperatures below 40 °C. Selectivity towards mephedrone and methylone was increased using trifluoracetylation under ambient ionization conditions. Low-temperature plasma ionization sources allow rapid detection of illicit 'bath salt' drugs in low amounts. The sources have a larger sampling area that allows faster detection of each analyte, and selectivity towards the selected drug is enhanced by adding reagents directly into the plasma stream.

Long-term performance of an irregular shaped borehole heat exchanger system: Analysis of real pattern and regular grid approximation

A reliable evaluation of long-term performance of a heat pump coupled with a borehole heat exchanger (BHE) field is necessary to verify the stability of its heat exchange capability over the time. The BHE field pattern is often assumed to be regular (e.g., rectangular, L-shaped, T-shaped, etc.), or is assumed to be adequately approximated by one of these shapes. Moreover, a planned geothermal system is often designed regardless of the presence of other existing or planned BHE systems. In order to evaluate the validity and the possible limitations of these assumptions commonly made by the designer, a number of 25-year time span simulations have been carried out by means of 2D finite element modeling. In particular, the case of a real 28 BHE field, irregularly shaped and related to a building located in Northern Italy, has been studied together with its 7-by-4 regular grid approximation and a series of 28 BHE fields having different shapes. Besides the real annual thermal load profile characterized by quasi-balanced winter heating and summer cooling, two other profiles characterized by increasingly unbalanced operation have been taken into account. The numerical study shows that (i) the regularly shaped approximation, a common choice in BHE design, seems to be reasonable under the condition that groundwater flow is absent for all the thermal load profiles; (ii) if a strong heating/cooling imbalance occurs, the thermal footprint of a BHE field can be very extensive, preventing the installation of future nearby BHE systems.

Crack sizing by laser excited thermography

Active thermography is a nowadays widely used NDT method making use of thermal material properties for defect detection. Basically, the sample is heated and the resulting surface temperature is recorded by an IR camera. For laser thermography a laser is used to heat the sample locally. The resulting spherical heat flow allows the detection of voids in arbitrary orientation. In this work, a method is presented which is suitable for the quantitative characterization of depth and angle of surface cracks. The main idea is to evaluate the crack-caused asymmetries of the laser's thermal footprint. The heat is introduced at fixed reference positions relative to the crack. In this paper a data analysis procedure is presented which allows the crack depth and angle to be described by only two characteristic scalar parameters. By investigating artificial test specimens with spark eroded notches, the feasibility of this method is validated. Furthermore, the behavior of the characteristic parameters with variations of crack angle, depth and experimental conditions is studied systematically by FEM simulations, showing that these parameters are well behaved.

The infrared thermometer in school science: teaching physics with modern technologies

Infrared thermometers measure temperature from a distance, using the infrared radiationemitted by all objects. These so-called non-contact thermometers make a wide variety oftemperature measurement and monitoring activities accessible to school-age students.Portable hand-held sensors also enable new or simplified investigations to be carried outwith quick and easy measurements. Following thermal footprints is a simple but engagingactivity for students: finding out which seat was occupied recently, which cup was filledwith a hot drink and which with a cold drink, which car was being driven a short time agoand so on.Nevertheless, introducing and explaining infrared thermometry in schools is not trivial. Tothis end an introduction with four steps is proposed.

Use of a Flexible Carbon Dioxide Laser Fiber for Precise Dissection of the Neurovascular Bundle During Robot-Assisted Laparoscopic Prostatectomy

Carbon dioxide (CO(2)) lasers deliver energy with minimal thermal spread to tissues during dissection. Excess thermal spread during dissection of the neurovascular bundle (NVB) can affect potency in men after robot-assisted radical prostatectomy (RARP). We report on a novel delivery mechanism for CO(2) laser energy through a flexible fiber to enhance accuracy of NVB dissection during RARP. A feasibility study of the OmniGuide BeamPath URO-LG CO(2) laser fiber for NVB dissection was performed on 10 patients with primary Gleason 3 T1c prostate cancer during RARP. Bilateral lateral fascial antegrade nerve sparing was performed. We evaluated fiber performance, safety, and efficacy. The fiber was inserted through the 12-mm assistant's port and easily manipulated by robotic instruments. Once pedicles were clipped and dissected, the laser fiber was effective in establishing planes of dissection between prostatic capsule and NVB. The endoscopically discernable thermal laser footprint was small, with minimal thermal spread during nerve sparing, meticulous dissection of NVB, and fascial layer identification. Although the laser did provide extremely accurate dissection, it was unable to serve as an adequate means of larger vessel coagulation. The flexible CO(2) laser fiber was easily manipulated. Identification of fascial layers during nerve sparing was facilitated with the fiber. Long-term follow-up is necessary to determine efficacy of this technology versus conventional techniques on the NVB. Larger studies are currently in progress to determine if use of the flexible CO(2) laser fiber results in improvements in functional outcomes with regard to return of sexual potency after RARP.

V480 FLEXIBLE CO 2 LASER ASSISTED NEUROVASCULAR BUNDLE DISSECTION FOR ROBOTIC PROSTATECTOMY

You have accessJournal of UrologyProstate Oncology1 Apr 2010V480 FLEXIBLE CO2 LASER ASSISTED NEUROVASCULAR BUNDLE DISSECTION FOR ROBOTIC PROSTATECTOMY Philippa Cheetham, Matthew Truesdale, and Ketan Badani Philippa CheethamPhilippa Cheetham More articles by this author , Matthew TruesdaleMatthew Truesdale More articles by this author , and Ketan BadaniKetan Badani More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2010.02.554AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Carbon dioxide (CO2) lasers have been cited to deliver energy with minimal thermal spread to tissues during dissection. The CO2 laser is thus widely used in head and neck oncology surgery and neurosurgery, resulting in predictable penetration depth and minimal collateral damage. Until recently, use of the CO2 laser as a surgical tool has been limited by the necessity for delivery through a rigid, rather than a fiber-based flexible delivery system. Excess thermal spread during neurovascular bundle (NVB)dissection can affect potency in men following radical prostatectomy. We report on a novel delivery of CO2 laser energy through a flexible fiber to enhance the accuracy of dissection of the NVB during robotic assisted laparoscopic prostatectomy (RALP). METHODS A feasibility study of the OmniGuide® BeamPath™ URO-LG CO2 laser fiber for neurovascular bundle dissection was performed on 8 men with clinical stage T1c, Gleason 6 or 7 prostate cancer during RALP. Upon identification of the NVB, a large needle driver was used to manipulate the fiber. Bilateral lateral fascial nerve sparing was performed in antegrade fashion. RESULTS We evaluated the performance, safety and efficacy of the fiber, which was successfully inserted through the assistant's port (12 mm). The size of the device allowed adequate space for simultaneous insertion of standard 5 mm laparoscopic tools. The fiber was easily manipulated by robotic instruments.Once the pedicles were clipped and dissected, the laser fiber was effective in establishing the plane of dissection between the prostatic capsule and the neurovascular bundle. Visual examination indicated that the thermal footprint of the laser was small, with minimal thermal spread during the nerve sparing portion of the procedure. This resulted in meticulous dissection of the NVB and fascial layer identification.The use of the laser fiber was safe with precise soft tissue cutting, stemming from its ready absorption in water. Whilst the laser did provide extremely accurate dissection, it was unable to serve as an adequate means of coagulation in larger vessels. CONCLUSIONS The flexible CO2 laser fiber was easily manipulated and identification of fascial layers during nerve sparing was facilitated with the fiber. Long-term follow-up is necessary to determine the efficacy of this technology versus conventional techniques on the NVB. Larger studies are currently in progress to determine if use of the flexible CO2 laser fiber results in improvements in functional outcomes with regards to return of sexual potency following robotic prostatectomy. New York, NY© 2010 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 183Issue 4SApril 2010Page: e189 Advertisement Copyright & Permissions© 2010 by American Urological Association Education and Research, Inc.MetricsAuthor Information Philippa Cheetham More articles by this author Matthew Truesdale More articles by this author Ketan Badani More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Sintered porous heat sink for cooling of high-powered microprocessors for server applications

This paper experimentally investigates the sintered porous heat sink for the cooling of the high-powered compact microprocessors for server applications. Heat sink cold plate consisted of rectangular channel with sintered porous copper insert of 40% porosity and 1.44 × 10 −11 m 2 permeability. Forced convection heat transfer and pressure drop through the porous structure were studied at Re ⩽ 408 with water as the coolant medium. In the study, heat fluxes of up to 2.9 MW/m 2 were successfully removed at the source with the coolant pressure drop of 34 kPa across the porous sample while maintaining the heater junction temperature below the permissible limit of 100 ± 5 °C for chipsets. The minimum value of 0.48 °C/W for cold plate thermal resistance ( R cp ) was achieved at maximum flow rate of 4.2 cm 3 /s in the experiment. For the designed heat sink, different components of the cold plate thermal resistance (R cp ) from the thermal footprint of source to the coolant were identified and it was found that contact resistance at the interface of source and cold plate makes up 44% of R cp and proved to be the main component. Convection resistance from heated channel wall with porous insert to coolant accounts for 37% of the R cp . With forced convection of water at Re = 408 through porous copper media, maximum values of 20 kW/m 2 K for heat transfer coefficient and 126 for Nusselt number were recorded. The measured effective thermal conductivity of the water saturated porous copper was as high as 32 W/m K that supported the superior heat augmentation characteristics of the copper–water based sintered porous heat sink. The present investigation helps to classify the sintered porous heat sink as a potential thermal management device for high-end microprocessors.

Thermal footprint of an eroded thrust sheet in the southern Appalachian thrust belt, Alabama, USA

Erosion of the leading hanging-wall cutoffs of thrust sheets commonly obscures the magnitude of thrusting. The Jones Valley thrust fault in the southern Appalachian thrust belt in Alabama, USA, is exposed along a northwest-directed, large-scale frontal ramp, and the leading part of the thrust sheet has been eroded. Previously published and newly collected vitrinite reflectance data from Pennsylvanian coal beds document a distinct, northeast-trending, elongate, oval-shaped thermal anomaly northwest of the trace of the Jones Valley fault. The northwest edge of the thermal anomaly is ~18 km northwest of the fault trace, suggesting the original extent of the eroded thrust sheet. The anomaly ends both northeastward and southwestward along strike at lateral ramps. The southeast edge of the anomaly corresponds to the location of a footwall frontal ramp. A three-dimensional heat conduction model for simultaneous horizontal (two-dimensional) and vertical heat flow in a rectangular thrust sheet is designed to test whether the documented thermal anomaly (%Ro = 1.0–1.6) may reflect the former extent of thrust-sheet cover. The model uses a 3-km-thick thrust sheet with horizontal dimensions of 10 x 30 km, as well as a three-dimensional analytical solution to the heat conduction equation, whereby the thrust sheet cools both laterally and vertically. The model reproduces the magnitude and oval shape of the vitrinite reflectance anomaly at 100–500 k.y. after thrust emplacement. The geothermal gradient reaches a steady state at ~2 m.y., and is never fully reestablished even for long times because of lateral cooling in the hanging wall. Thickness and extent of the thrust sheet from the thermal model are consistent with balanced and restored cross sections of the Jones Valley thrust sheet based on geologic data; a thrust sheet ~3 km thick was emplaced ~18 km onto the foreland over the site of the thermal anomaly. The three-dimensional thermal evolution of both the hanging wall and the footwall is distinct from that predicted from one-dimensional models; a three-dimensional model predicts less heating of the footwall because of horizontal heat loss across bounding ramps.

The near wall effect of synthetic jets in a boundary layer

An experimental investigation to analyse the qualitative near wall effect of synthetic jets in a laminar boundary layer has been undertaken for the purpose of identifying the types of vortical structures likely to have delayed separation on a 2D circular cylinder model described in this paper. In the first instance, dye visualisation of the synthetic jet was facilitated in conjunction with a stereoscopic imaging system to provide a unique quasi three-dimensional identification of the vortical structures. Secondly, the impact of synthetic jet structures along the wall was analysed using a thermochromic liquid crystal-based convective heat transfer sensing system in which, liquid crystals change colour in response to the thermal footprints of a passing flow structure. Of the different vortical structures produced as a result of varying actuator operating and freestream conditions, the footprints of hairpin vortices and stretched vortex rings revealed a marked similarity with the oil flow pattern of a vortex pair interacting with the separation line on the cylinder hence suggesting that either of these structures was responsible in delaying separation. Conditions were established for the formation of the different synthetic jet structures in non-dimensional parameter space.

A Microfabricated Nebulizer for Liquid Vaporization in Chemical Analysis

A miniaturized nebulizer chip for vaporization of liquid samples for mass spectrometry has been designed, fabricated, and characterized for fluidic and thermal performance. Silicon/glass chip has a liquid sample channel placed centrally between symmetric nebulizer gas channels. The liquid sample is nebulized and vaporised by an integrated platinum heater. The vaporized sample exits through an etched nozzle, and is ionized by an external corona needle. The ions are analysed by a mass spectrometer. The chip has been fabricated in both anisotropically wet etched and DRIE versions in silicon, with an anodically bonded Pyrex glass cover plate. Three different fluidic inlet designs are presented, with both through-wafer and edge insert versions. The shape of the erupting gas jet has been visualized by infrared thermography by using a low-diffusivity imaging screen and high heat capacity helium as a test gas. Dimensions of the jet's thermal footprint on the screen show that the jet is very narrow and confined, and this is confirmed in mass spectrometry results. This confined jet supplies the sample to the ionization region near corona tip, enabling efficient use of very small sample amounts and submicroliter flows.1591