https://scholarsarchive.byu.edu/cgi/viewcontent.cgi?article=2573&context=facpub

Supercritical CO2 Brayton cycles for solar-thermal energy

CFD applications in various heat exchangers design: A review

Comparison of void fraction correlations for different flow patterns in horizontal and upward inclined pipes

As the scale of devices becomes small, thermal control and heat dissipation from these devices can be effectively accomplished through the implementation of microchannel passages. The small passages provide a high surface area to volume ratio that enables higher heat transfer rates. High performance microchannel heat exchangers are also attractive in applications where space and/or weight constraints dictate the size of a heat exchanger or where performance enhancement is desired. This survey article provides a historical perspective of the progress made in understanding the underlying mechanisms in single-phase liquid flow and two-phase flow boiling processes and their use in high heat flux removal applications. Future research directions for (i) further enhancing the single-phase heat transfer performance and (ii) enabling practical implementation of flow boiling in microchannel heat exchangers are outlined.

History, Advances, and Challenges in Liquid Flow and Flow Boiling Heat Transfer in Microchannels: A Critical Review

The development technology and applications of supercritical CO2 power cycle in nuclear energy, solar energy and other energy industries

Heat transfer and pressure drop correlations of microchannel heat exchangers with S-shaped and zigzag fins for carbon dioxide cycles

Fin shape effects on thermal-hydraulic characteristics were studied for a Microchannel Heat Exchanger (MCHE) with S-shaped fins using 3D-CFD and changing the fin parameters: fin angle, overlapping length, fin width, fin length, and edge roundness. The fin angle effect on the pressure drop is consistent with the equation obtained experimentally by Weisbach for a circular bent tube: the pressure drop in the S-shaped fin configuration results from bent flow. The overlap of fins with those located immediately downstream at the offset position provides a guide wing effect that reduces the pressure drop remarkably. The overlap was changed by changing the fin radial position and arc length. The pressure drop was minimized when the downstream fins are placed in the middle of the bent flow channels formed by the fins upstream, which differs from Ito's configuration obtained from experiments with a single bent duct. Regarding arc length, the pressure drop is minimized at the standard overlapping length, which was f...

Advanced Microchannel Heat Exchanger with S-shaped Fins

In-bundle void measurement of a BWR fuel assembly by an x-ray CT scanner: Assessment of BWR design void correlation and development of new void correlation

Supercritical carbon dioxide (S-CO2 ) gas turbines can generate power at high cycle thermal efficiency, even at modest temperatures of 500–550°C, because of their markedly reduced compressor work near the critical point. Furthermore, the reaction between Na and CO2 is milder than that between H2 O and Na. A more reliable and economically advantageous power generation system could be achieved by coupling with a sodium-cooled fast reactor. At Tokyo Institute of Technology, numerous development projects have been conducted for development of this system in cooperation with JAEA. Supercritical CO2 compressor performance test results are given as described herein. A centrifugal compressor is chosen for the performance test. Main compressor parts are stored in a pressure vessel. Maximum design conditions of the supercritical CO2 test apparatus are pressure of 11 MPa, temperature of 150°C, the flow rate of 6 kg/s and rotational speed of 24,000 rpm. The centrifugal compressor has an electric motor with permanent magnets on the rotor surface, with speed control by an inverter up to 24,000 rpm, a rotor shaft for the impeller, and a motor supported by gas bearings. Different compressor design points are examined using impellers of three kinds; test data are obtained using those impellers under steady state conditions with changing pressure, temperature, flow rate, and compressor rotor speed. The pressure ratio (compressor outlet pressure/inlet pressure) is obtained with the function of compressor rotational speed and the fluid flow rate. The data cover a broad region from sub-critical to supercritical pressure. Such data were obtained for the first time. No unstable phenomenon was observed in the area where the CO2 properties change sharply. Data of the pressure ratio vs. flow rate were coincident with the fundamental compressor theory.Copyright © 2010 by ASME

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Performance Test Results of the Supercritical CO2 Compressor for a New Gas Turbine Generating System

The purpose of this study is to develop a void fraction correlation based on the void data measured by an X-ray CT scanner. The tests were carried out in an out-of-pile test facility that can simulate the high pressure and high temperature conditions of BWRS. An electrically heated test assembly simulated a BWR fuel assembly on a full scale. The new void fraction correlation has been developed based on the drift flux model, and the prediction accuracy of the void fraction data for this study was Δα (the average of the difference between measurement and calculation)=0.3% and σ (standard deviation of Δα)=1.9%. The agreement with other published void fraction data was fairly good.

Takao Ishizuka

Papers

Heat transfer and pressure drop correlations of microchannel heat exchangers with S-shaped and zigzag fins for carbon dioxide cycles

Advanced Microchannel Heat Exchanger with S-shaped Fins

In-bundle void measurement of a BWR fuel assembly by an x-ray CT scanner: Assessment of BWR design void correlation and development of new void correlation

Performance Test Results of the Supercritical CO2 Compressor for a New Gas Turbine Generating System

Void Fraction Correlation for Rod Bundle. Void Fraction Correlation Based on Void Data of BWR Fuel Assembly Measured by X-Ray CT Scanner.