Friction Factor Measurements in an Equally Spaced Triangular Tube Array

Friction factor data for adiabatic cross-flow of water in a staggered tube array was obtained over a Reynolds number range (based on hydraulic diameter and gap velocity) of about 10,000 to 250,000. The tubes were 12.7mm (0.5 inch) outer diameter, in a uniformly spaced triangular arrangement with a pitch-to-diameter ratio of 1.5. The friction factor was compared to several literature correlations, and was found to be best matched by the Idelchik correlation. Other correlations were found to vary significantly from the test data. Based on the test data, a new correlation is proposed for this tube bundle geometry which covers the entire Reynolds number range tested

Critical heat flux experiments in a heated rod bundle with upward crossflow of Freon 114

Critical heat flux (CHF) data were obtained for upward crossflow of R-114 in a heated staggered rod bundle. Data were obtained over a broad range of mass fluxes (135 to 1,221 kg/m{sup 2} sec), inlet subcooling (0 to 55 C), and qualities ({minus}0.42 to 0.92). The present work extends the available database to higher quality, inlet subcooling, and mass flux. The test section is 3.43 cm x 15.24 cm (1.35 in. x 6 in.) in cross section with a total length of 55.88 cm (22 inches) from the top of the inlet flow straightener to the perforated plate at the test section exit. The rod bundle has a triangular pitch with a diameter (D) of 0.635 cm (0.25 in), and a pitch to diameter (P/D) ratio of 1.5. The rod bundle has 165 rods with a 15.24 cm (6 in.) heated length arranged in 55 rows of three rods each. Unheated half rods were positioned on the walls of the test section to maintain the regular rod arrangement and prevent flow bypass along the gaps between the window and the first column of heated rods. A single instrumented heater was positioned five rows upstream from the bundle exit to determine CHF. The last three rows of rods in the bundle were unheated to prevent undetected dryout downstream of the CHF position. Temperature excursions due to CHF were sensed using four imbedded thermocouples (TC) in the heater rod. The four TC temperatures were continuously monitored on a strip chart recorder. The rod heat was gradually increased until CHF was detected. Overall, the data are in good agreement with the Jensen and Tang correlation in the range of application of this correlation. The local minima in CHF which occurs near zero quality is slightly lower in the present experiment than for the Jensen and Tang correlation. At high quality, CHF drops off more rapidly than the Jensen-Tang prediction. Data are now available to extend the existing correlations to higher quality, and higher inlet subcooling

Mixed convection in vertical rod bundles

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 1982Includes bibliographical references.by Paul Douglas Symolon.Ph. D.Ph. D. Massachusetts Institute of Technology, Department of Mechanical Engineerin

Manual for use with the computer code SUPERENERGY: data reduction version. [LMFBR]

A data reduction version of the SUPERENERGY code is presented as a means of calibrating the mixing parameters epsilon/sub 1/* and C/sub 1/ from salt tracer injection experiments. In addition to the older version (SUPERENERGY-DRV-1) which uses a single concentration distribution map to calibrate each mixing parameter, a new version (SUPERENERGY-DRV-2) is presented which utilizes two maps from two different injection levels to calibrate each mixing parameter

High-altitude, long-endurance unmanned aerial vehicles vs. satellites

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 145-159).Satellites have become a critical component of nearly every aspect of modern life. In addition to well-known civilian applications, military applications of space-based platforms include supporting mission operations through communications; intelligence, surveillance and reconnaissance (ISR); and position, navigation and timing (PN&T). While satellite applications are numerous and increasing technical achievements make satellites more capable, they do have several drawbacks. Satellites are expensive, they require long development times and they are difficult to replace. Since the successful Chinese anti-satellite (ASAT) missile test on January 11, 2006, U.S. military leaders have become increasingly concerned over this new vulnerability to critical space assets. In addition to efforts designed to improve operationally responsive space capabilities, military leaders have begun researching alternatives to space-based platforms. In November, 2006, the U.S. Army released the Army Space Master Plan (ASMP). In the unclassified extract of that plan, the Army identifies a list of eight topics for further investigation including the question, "Where should the Army invest in near-space and high-altitude, long-endurance [HALE] platforms as a lower cost, more responsive alternative to space platforms if they prove technically feasible?" This thesis discusses technical challenges associated with making HALE platforms feasible and explores the potential benefits of using these platforms to augment or enhance the three primary military applications of communications, ISR and PN&T including a detailed examination of current satellite-based military payload capabilities and limitations.(cont.) Finally, this thesis discusses potential methods to integrate HALE capabilities into the current U.S. Army Space Operations doctrine and provides some suggestions for the potential role of Army Space Operations in the design, development, implementation and use of HALE systems. By demonstrating how the Army can use HALE platforms to reduce the capability gap and fulfill more of the users' requirements, this research will answer the question posed in the Army Space Master Plan.by William Everette Symolon.S.M

Fluid-mixing studies in a hexagonal 217-pin wire-wrapped rod bundle. [LMFBR]

Mixing, pressure drop, and flow split experiments were performed on a 217 pin LMFBR fuel bundle with a pitch to diameter ratio of 1.25 and a lead length of 12 inches. It was found that the turbulent flow data could best be characterized by the energy parameter C/sub 1L/=.106, which is 9% higher than the value from the correlation of Chiu et al. Chiu's correlation was developed on a data base of 61 and 91 pins. The spread of existing data about the correlation is +- 25%, but the error band on our data is expected to be less (approx. +- 10% since injection depth effects were not previously considered). This result is consistent with the concept of increased swirl flow in larger bundles (more pins)

Single-Image Super Resolution using Convolutional Neural Network

Increasing threats to U.S. national security satellite constellations have resulted in an increased interest in constellation resilience and satellite redundancy. CubeSats have contributed to commercial, scientific and government applications in remote sensing, communications, navigation and research and have the potential to enhance satellite constellation resilience. However, the inherent size, weight and power limitations of CubeSats enforce constraints on imaging hardware; the small lenses and short focal lengths result in imagery with low spatial resolution. Low resolution limits the utility of CubeSat images for military planning purposes and national intelligence applications. This paper implements a super-resolution deep learning architecture and proposes potential applications to CubeSat imagery

Mixed Convection Heat Transfer Experiments in Smooth and Rough Verticla Tubes

The mixed convection regime is a transitional heat transfer regime between forced convection and natural convection, where both the forced component of flow, and the buoyancy induced component are important. Aiding flow is when buoyancy forces act in the same direction as the forced flow (heated upflow or cooled downflow), while opposing flow is when the buoyancy force is in the opposite direction of the forced flow (cooled upflow or heated downflow). For opposing flow the buoyancy always increases the rate of heat transfer over the forced convection value. For aiding flow, as the heat flux increased, a reduction in heat transfer is encountered until a condition known as laminarization occurs, where the heat transfer is at a minimum value. Further increases in the wall heat flux causes re-transition to turbulence, and increased heat transfer. In this paper, for the first time, experiments were performed to characterize the effect of surface roughness on heat transfer in mixed convection, for the case of aiding flow. A correlation was developed to allow calculation of mixed convection heat transfer coefficients for rough or smooth tubes