A simple correlation was developed earlier by Kandlikar (1983) for predicting saturated flow boiling heat transfer coefficients inside horizontal and vertical tubes. It was based on a model utilizing the contributions due to nucleate boiling and convective mechanisms. It incorporated a fluid-dependent parameter F{sub fl} in the nucleate boiling term. The predictive ability of the correlation for different refrigerants was confirmed by comparing it with the recent data on R-113 by Jensen and Bensler (1986) and Khanpara et al. (1986). In the present work, the earlier correlation is further refined by expanding the data base to 5,246 data points from 24 experimental investigations with ten fluids. The proposed correlation gives a mean deviation of 15.9 percent with water data, and 18.8 percent with all refrigerant data, and it also predicts the correct h{sub TP} versus x trend as verified with water and R-113 data yielded the lowest mean deviations among correlations tested. The proposed correlation can be extended to other fluids by evaluating the fluid-dependent parameter F{sub fl} for that fluid from its flow boiling or pool boiling data.

A General Correlation for Saturated Two-Phase Flow Boiling Heat Transfer Inside Horizontal and Vertical Tubes

PROTRACED COUNTERINSURGENCY: CHINESE COIN STRATEGY IN XINJIANG by MAJ J. Scott LaRonde, USA, 95 pages. In 1949, following the conclusion of its revolutionary war against the Chinese Nationalist forces, the People’s Liberation Army (PLA) peacefully occupied China’s western most province of Xinjiang. For nearly sixty years, the PLA has conducted a counterinsurgency against several, mostly Uyghur-led, separatist movements. Despite periods of significant violence, particularly in the early 1950s and again in the 1990s, the separatist forces have not gained momentum and remained at a level one insurgency. Mao ZeDeng is revered as a master insurgent and the father of Fourth Generation Warfare. Strategists in armies worldwide study his writings on revolutionary and guerilla warfare. This monograph concludes that Mao, as well as the communist leaders who followed him, was also successful at waging protracted counterinsurgency. For nearly sixty years, separatist movements in Xinjiang, Tibet, and Taiwan have all failed. This monograph analyzes the conflict in Xinjiang and concludes that the Chinese continue to defeat the separatist movement in Xinjiang through a strategy that counters Mao’s seven fundamentals of revolutionary warfare.

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Approved for Public Release; Distribution is Unlimited

Main factors affecting the lifetime of Proton Exchange Membrane fuel cells in vehicle applications: A review

Liquid water visualization in PEM fuel cells: A review

In flow boiling, the nucleate and convective components are superimposed by a very complex mechanism, which so far is not well understood Two models exist in present literature, one by Chen [3] (1963), using addition of the two components with a suppression factor; and one by Shah [8] (1976), using the “greater of” the two components with a Bo-number simplified correlation Neither model presents a satisfactory solution, as attested by the numerous methods published since then, mostly based only on regression analysis-derived correction factors In this article a new model, based on asymptotic addition of the two boiling components, is introduced It follows the established principles of flow boiling and converges correctly to the extremes of all parameters Tested on the University of Karlsruhe data bank containing over 13,000 data points in vertical flow boiling, results superior to previous correlations are demonstrated

Flow Boiling Heat Transfer in Vertical Tubes Correlated by an Asymptotic Model

This paper describes an experimental investigation to determine the mechanism governing nucleate pool boiling heat transfer in refrigerant-oil mixtures, the role diffusion plays in this process, and the influence of the fluid mixture properties. Boiling heat transfer date were taken in mixtures of up to 10 per cent oil by weight in R-113. Thermophysical properties of the mixtures (density, viscosity, surface, tension, specific heat, and contact angle) were measured. The decrease in heat transfer coefficient with incresing oil concentration is attributed to diffusion in an oil-enriched region surrounding the growing vapor bubbles. A correlation based on a postulated mechanism is presented which shows fair agreement with the experimental data from this study and with data obtained from the literature.

Prediction of Nucleate Pool Boiling Heat Transfer Coefficients of Refrigerant-Oil Mixtures

https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=841176

PEM fuel cell membrane hydration measurement by neutron imaging

A Fresnel lens comprising a substantially polygonal focusing portion adapted to focus solar radiation to a area having the same geometry as the focusing portion of the lens. Also a solar module comprising the Fresnel collecting lens and a substantially polygonal photovoltaic cell. The photovoltaic cell is mounted at distance from the Fresnel collecting lens so that the size of the area substantially matches the size of the photovoltaic cell. Also a solar panel having multiple modules within a glazed building envelope system. The solar panel also includes an actuating mechanism within the glazed window envelope system. The actuating mechanism is operatively connected to the plurality of solar modules and is adapted to move the solar modules to track the sun.

Concentrating type solar collection and daylighting system within glazed building envelopes

Evaluation of bubble departure diameter correlations

Chapter 1. Introduction to Thermal and Fluids Engineering. Chapter 2. The First Law. Chapter 3. Thermal Resistances. Chapter 4. Fundamentals of Fluid Mechanics. Chapter 5. Thermodynamic Properties. Chapter 6. Appications of the Energy Equation to Open Systems. Chapter 7. Thermodynamic Cycles and the Second Law. Chapter 8. Refrigeration, Heat Pump, and Power Cycles. Chapter 9. Internal Flows. Chapter 10. External Flows. Chapter 11. Conduction Heat Transfer. Chapter 12. Convection Heat Transfer. Chapter 13. Heat Exchangers. Chapter 14. Radiation Heat Transfer. Chapter 15. Ideal Gas Mixtures and Combustion (Web). Appendix A: Tables in SI Units. Appendix B: Tables in British Units. Appendix C: Answers to Selected Problems. Index.

/pdf/introduction-to-thermal-and-fluids-engineering-mv5dljwduc.pdf

Michael K. Jensen

Papers

Prediction of Nucleate Pool Boiling Heat Transfer Coefficients of Refrigerant-Oil Mixtures

PEM fuel cell membrane hydration measurement by neutron imaging

Concentrating type solar collection and daylighting system within glazed building envelopes

Evaluation of bubble departure diameter correlations

Introduction to Thermal and Fluids Engineering