ADVERTISEMENT RETURN TO ISSUEPREVCorrespondenceNEXTComment on "Application of Entransy Analysis in Self-Heat Recuperation Technology"Adrian BejanView Author Information Department of Mechanical Engineering, Duke University, Durham, North Carolina 27708-0300, United StatesCite this: Ind. Eng. Chem. Res. 2014, 53, 47, 18352–18353Publication Date (Web):November 12, 2014Publication History Published online12 November 2014Published inissue 26 November 2014https://pubs.acs.org/doi/10.1021/ie5037512https://doi.org/10.1021/ie5037512article-commentaryACS PublicationsCopyright © 2014 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views632Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (1 MB) Get e-AlertscloseSUBJECTS:Capacitors,Entropy,Heat transfer,Thermodynamics Get e-Alerts
Background:Treatment decisions in primary myelofibrosis (PMF) are guided by several prognostic systems based on disease-specific risk factors, including complete blood counts and cytogenetics. Patient specific comorbidities, e.g. non-hematopoietic organ dysfunction, are not incorporated into current prognostic models. Likewise, PMF risk stratification has not yet integrated large scale electronic health record (EHR) clinical data to refine these scoring systems. We have identified a PMF cohort within the Synthetic Derivative (SD), a de-identified, research-dedicated mirror of the EHR at Vanderbilt University Medical Center that contains 2.9 million individual records with 148 million ICD codes, and 125 million clinical notes. As a proof of concept, we leveraged the SD to develop a PMF cohort. We then aimed to identify novel patient specific comorbidities that may be associated with reduced overall survival (OS) in PMF via a phenome-wide association (PheWAS) study. Methods:We interrogated the SD for PMF via an algorithm that relied on ICD codes, natural language processing of physician notes, and medication history to identify high probability cases. Confirmation of PMF was based on strict hematologist review using 2016 WHO criteria. To this end, only patients with accessible hematopathology reports and cytogenetics, and more than 1 visit to the institution were enrolled. Patients with transformation to AML at presentation (e.g. within 30 days) were excluded. To evaluate each patient's overall comorbidity burden, we interrogated patient phecodes, which are grouped ICD9 codes shown to better mimic clinical phenotypes (PMID 20335276). Specifically, we extracted all ICD9 codes within 360 days of PMF diagnosis or referral and converted them to phecodes using the map available at https://phewascatalog.org/phecodes. PMF disease-related phecodes or codes that corresponded to DIPSS dependent variables were excluded. We identified 375 phecodes at PMF diagnosis, and conducted a PheWAS study to test the association of each phecode with survival. Survival was calculated as the interval between PMF diagnosis or referral and death or last follow-up (censor); patients who underwent hematopoietic stem cell transplant (HSCT) or transformed to AML were censored at that respective date. Survival from PMF diagnosis was estimated using the Kaplan-Meier method. We utilized the Cox proportional hazards model adjusted for the DIPSS predictors and evaluated the association of each comorbidity with the overall survival and reported those that are statistically significant after multiple testing adjustment (Bonferroni corrected P<0.00013). Results:We identified 193 cases of PMF from 1995-2016 that met strict pathology inclusion criteria. PMF median age of diagnosis was 59 (range 24-87), 42% were female, and 35 patients were referred greater than one year after diagnosis. Median OS was 39 months (range 1-265), with 23 patients developing AML and 40 patients treated with HSCT. Comorbidity analysis adjusted for DIPSS factors revealed five phecodes associated with reduced OS with Bonferroni correction (Figure 1); intracranial hemorrhage (HR 28.7; 95% CI 7-116; P=2.83E-06) invasive fungal infection (HR 41.1; 95% CI 7-235; P=2.90E-05), cerebral degeneration or hydrocephalus (HR 15.1; 95% CI 3-60;P=8.56E-05), encephalopathy or coma (HR 15; 95% CI 3-59; P=0.0001) and renal failure (HR 4; 95% CI 2-8; P=0.0001). Within the renal failure cohort, uric acid levels within 12 months of PMF diagnosis were elevated (N=18, mean 9.3 mg/dl) compared to the remaining PMF cases (N=132; mean 7.6 mg/dl) P=0.016. An additional 21 patient specific comorbidity patterns noted near Bonferroni cutoff (P<0.01), with highlights including pulmonary congestion (HR 6; 95% CI 1.7-21), pulmonary heart disease (HR 5.9; 95% CI 0.6-58), cardiomyopathy (HR 5; 95% CI 1.3-19), congestive heart failure (HR 4.3; 95% CI 1.3-14), and pneumonia (HR 3.3; 95% CI 1.4-7). Summary:We successfully leveraged our PMF cohort to identify potential high risk patient-specific comorbidities not included in current risk models. In addition, we illustrated the capacity to use these techniques to identify potential clinical intervention (e.g. chronic hyperuricemia and its impact on renal function). This study demonstrates the potential to refine prognostication and treatment decisions via EHR data to study large populations of rare myeloid disease. Disclosures Savona: Celgene Corporation: Membership on an entity's Board of Directors or advisory committees; Incyte Corporation: Membership on an entity's Board of Directors or advisory committees, Research Funding; Karyopharm Therapeutics: Consultancy, Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Selvita: Membership on an entity's Board of Directors or advisory committees; Takeda: Membership on an entity's Board of Directors or advisory committees, Research Funding; Boehringer Ingelheim: Patents & Royalties; AbbVie: Membership on an entity's Board of Directors or advisory committees; Sunesis: Research Funding; TG Therapeutics: Membership on an entity's Board of Directors or advisory committees, Research Funding.
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No abstract is provided for this article.
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No abstract is provided for this article.
This is a review of the concepts of purpose, direction, and objective in the discipline of thermodynamics, which is a pillar of physics, natural sciences, life science, and engineering science. Reviewed is the relentless evolution of this discipline toward accounting for evolutionary design with direction, and for establishing the concept of purpose in methodologies of modeling, analysis, teaching, and design optimization. Evolution is change after change toward flow access, with direction in time, and purpose. Evolution does not have an ‘end’. In thermodynamics, purpose is already the defining feature of methods that have emerged to guide and facilitate the generation, distribution, and use of motive power, heating, and cooling: thermodynamic optimization, exergy-based methods (i.e., exergetic, exergoeconomic, and exergoenvironmental analysis), entropy generation minimization, extended exergy, environomics, thermoecology, finite time thermodynamics, pinch analysis, animal design, geophysical flow design, and constructal law. What distinguishes these approaches are the purpose and the performance evaluation used in each method.
No abstract is provided for this article.
We examine the potential of heat-transfer augmentation techniques to reduce irreversibility (entropy generation, destruction of available work) in equipment for heat exchange. A number of popular swirl flow-promoting techniques is investigated in detail. It is shown that the irreversibility reduction induced by each technique depends strongly on the operating parameters of the apparatus in which heat transfer is to be augmented. An important operating parameter is the ratio of fluid-friction irreversibility divided by heat-transfer irreversibility, φ 0. It is shown that φ 0 must lie below a critical value in order for a proposed augmentation technique to yield savings in available work. The paper illustrates the use of entropy generation in assessing the relative merit of competing heat-transfer augmentation techniques. The geometric features of a proposed augmentation technique can be optimally selected in order to yield the maximum reduction in heat exchanger duct irreversibility.
This paper shows how the configuration of a heat exchanger with fixed size controls the global performance. The cold-side fluid is driven by natural convection in vertical round tubes connected via two plenums. The hot-side fluid flows perpendicularly to the vertical tubes, and heats them by forced convection. The flow is laminar on both sides. The search for the flow configuration is pursued from a configuration with two tubes to three and four tubes. When the configuration has two tubes, the best design is with tubes with nearly the same diameter. When there are three tubes, it is possible to optimize the tube spacings as well. The constructal design represents a departure from the traditional approach, which consists of many tubes with the same diameter and spacing.
This is a theoretical, numerical, and experimental study of natural convection heat transfer from an immersed surface with intermittent uniform heat flux. Scale analysis predicts that the “on” time interval can be optimized such that the overall Nusselt number is maximized. Furthermore, Nu increases monotonically as the “off” time interval decreases. These features are verified and determined more accurately by complete numerical simulations for a vertical flat surface in the range 103 ≤ Ra ≤ 105 and Pr = 7, where Ra is based on heat flux and wall height. They are further verified by means of water experiments in the range 1010 ≤ Ra ≤ 1011. The pulsating heater configurations tested experimentally are the vertical cylinder, which approximates boundary layer flow on a plane surface, and the horizontal cylinder. The optimal square-wave heat pulse for a natural convection immersion heater is reported in general (scaling correct) terms.
This is an experimental and numerical study of natural convection and forced convection air cooling of plate finned heat sinks. The study documents quantitatively two effects: (1) the orientation of the fin array relative to the gravitational field in natural convection, and relative to a free stream in forced convection, and (2) the tilting of the crests of the plate fins relative to the approaching flow. In each configuration, the results based on complete three-dimensional numerical simulations of the flow and heat transfer confirm the validity of the results determined based on direct measurements. For example, it is shown that the overall thermal conductance of the heat sink increases when the fin crests are inclined so that they face the approaching fluid. This augmentation effect increases as the coolant velocity increases. The thermal performance of arrays positioned perpendicularly to the flow is also documented.
An experimental and theoretical study of the static buckling of a downward flowing stream surrounded by a highly flexible duct is reported. It is shown analytically that the stream buckles into a meandering shape that depends strongly on the flow velocity in the duct. The amplitude of the buckled shape is found to be governed by the magnitude of the transverse force created by nonzero curvature at the free end of the duct. Experimental measurements confirm the buckled shape described analytically.
The objective of the Journal of Mechanics is to provide an international forum to foster exchange of ideas among mechanics communities in different parts of world.
No abstract is provided for this article.
This article extends to three-dimensional heat flow the constructal method of minimizing geometrically the thermal resistance between a heat-generating volume and one point. Optimized is the geometry of each volume element, and the shape and distribution of high-conductivity inserts. The new feature is the maximization of the amount of heat-generating material that operates at temperatures close to the hot-spot level (Tmax). Volume elements and subsequent constructs acquire optimal shapes where all the external surfaces are isothermal at Tmax. The same, constant thermal resistance separates each surface point (Tmax) and the common heat-sink point (Tmin). The optimized architecture is pine-cone-like, with high-conductivity nerves and low-conductivity filling (and heat-generating) material. The similarities between the constant-resistance structures and the three-dimensional tree networks found in nature are discussed. The analogy between evolutionary flow systems and evolutionary mechanical support systems is reasoned based on the same (constructal) principle of pursuing objective (purpose) subject to global and local constraints.
Here we show the performance of a cooling system consisting of one stream that morphs while embedded in a square plate heated uniformly. Several configurations are considered in order to establish the evolutionary direction in which the thermal performance of the cooling system is improving. First, serpentine shapes are considered. The total length of serpentine length is fixed, and the number of meanders is varied. The stream inlet and outlet are free to migrate on the perimeter of the heated plate. The results show that the serpentine with four elbows maintains lower peak temperatures when the inlet and the outlet of the duct are positioned in the middle of the side of the plate. We report the configuration in which the thermal conductance is maximum. Second, we analyzed the effect of various loop cooling configurations such as square, circular and clover leaf. Each loop is centered on the center of the plate, and its length is free to vary. The minimum peak temperature is achieved when the length of the circular loop is Lc =2.5L, and when the length of the square loop is Lc =2.8L. The clover leaf designs show even better performance.
This report identifies properties to be considered when selecting materials used in construction of torque tubes for rotating superconducting field windings in electrical machinery. The main design requirements are stated and the groups of material properties that influence directly the mechanical and thermal performance of a torque tube are derived. Most desirable is a low thermal conductivity to modulus of elasticity ratio which governs the refrigeration expenses and the tube wall aspect ratio (thickness/length). Numerical examples point out that fibre-reinforced plastics are potential candidates for use in torque tubes.
