Papers by Richard Kurwitz
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Surface............................................................................................. more Surface...........................................................................................................................19
Volume 5: Student Paper Competition, 2016
Earth & Space 2008, 2008
This paper describes the effort by the Texas Engineering Experiment Station (TEES) and Honeywell ... more This paper describes the effort by the Texas Engineering Experiment Station (TEES) and Honeywell for NASA to design and test a pre-flight prototype pump for use in the Extra-vehicular activity (EVA) portable life support subsystem (PLSS). Major design decisions were driven by the need to reduce the pump s mass, power, and volume compared to the existing PLSS pump. In addition, the pump must accommodate a much wider range of abnormal conditions than the existing pump, including vapor/gas bubbles and increased pressure drop when employed to cool two suits simultaneously. A positive displacement, external gear type pump was selected because it offers the most compact and highest efficiency solution over the required range of flow rates and pressure drops. An additional benefit of selecting a gear pump design is that it is self priming and capable of ingesting non-condensable gas without becoming air locked. The chosen pump design consists of a 28 V DC, brushless, sealless, permanent magnet motor driven, external gear pump that utilizes a Honeywell development that eliminates the need for magnetic coupling. Although the planned flight unit will use a sensorless motor with custom designed controller, the pre-flight prototype to be provided for this project incorporates Hall effect sensors, allowing an interface with a readily available commercial motor controller. This design approach reduced the cost of this project and gives NASA more flexibility in future PLSS laboratory testing. The pump design was based on existing Honeywell designs, but incorporated features specifically for the PLSS application, including all of the key features of the flight pump. Testing at TEES verified that the pump meets the design requirements for range of flow rates, pressure drop, power consumption, working fluid temperature, operating time, gas ingestion , and restart capability under both ambient and vacuum conditions. The pump operated between 40 and 240 lbm/hr flowrate, 35 to 100 F pump temperature range, and 5 to 10 psid pressure rise. Power consumption of the pump controller at the nominal operating point in both ambient and vacuum conditions was 9.5 W, which was less than the 12 W predicted. Gas ingestion capabilities were tested by injecting 100 cc of air into the fluid line; the pump operated normally throughout this test. The test results contained a number of anomalies, specifically power increases and a few flow stoppages, that prompted TEES and Honeywell to disassemble and inspect the pump. Inspection indicated contamination in the pump and fit issues may have played roles in the observed anomalies. Testing following reassembly indicated that the performance of the pump 1) matched both the predicted performance values, 2) the performance values measured prior to disassembly, and 3) was free of the anomalies noted in the pre-disassembly testing.
We estimate order of market entry effects when moderated by the strategic characteristics of the ... more We estimate order of market entry effects when moderated by the strategic characteristics of the entering firm. Although the main effect of order of market entry on market share is remarkably strong, we find, when we control for firms' strategic inclinations, that certain strategic types appear to fare better than others when pioneering new financial services. Such differences could help explain situations in which later entrants outperform pioneers. We thank Professors donald Lessard and Scott Stem for their many thoughtful comments and suggestions.
Description/Abstract We have developed a conceptual design for an accelerator-driven thorium cycl... more Description/Abstract We have developed a conceptual design for an accelerator-driven thorium cycle power reactor which addresses the issues of accelerator performance, reliability, and neutronics that limited earlier designs. The proton drive beam is provided ...
International Journal of Multiphase Flow, 2007
To utilize the advantageous properties of two-phase flow in microgravity applications, the knowle... more To utilize the advantageous properties of two-phase flow in microgravity applications, the knowledge base of two-phase flow phenomena must be extended to include the effects of gravity. In the experiment described, data regarding the behavior of two-phase flow in a conduit under microgravity conditions (essentially zero gravity) are explored. Of particular interest, knowledge of the void fraction of the gas and liquid in a conduit is necessary to develop models for heat and mass transfer, pressure drop, and wall shear. An experiment was conducted under reduced gravity conditions to collect data by means of a capacitance void fraction sensor and high speed visual imagery. Independent parameters were varied to map the flow regime regions. These independent parameters include gas and liquid volumetric flow rates and saturation pressures. Void fraction measurements were taken at a rate of 100 Hz with six sensors at two locations along the conduit. Further, statistical parameters were developed from the void fraction measurements. Statistical parameters such as variance, signal-to-noise ratio, half height value, and linear area difference were calculated and found to have characteristics allowing flow regime identification.
AIP Conference Proceedings, 2003
ABSTRACT An ultrasonic pulse-echo method for detecting the location of the air-liquid interface o... more ABSTRACT An ultrasonic pulse-echo method for detecting the location of the air-liquid interface of a air-liquid vortex in microgravity was tested. A vortex was established in near-zero gravity conditions in hydraulically-stirred phase separator. A single ultrasonic transducer located about mid-plane of the vortex was used to sense the thickness of the layer of liquid inside the phase separator and local to the ultrasonic transducer. Comparison was made between the sensed liquid layer thickness and an ideal right circular liquid annulus calculated from the know liquid inventory in the phase separator. The absolute error between the sensed and ideal annulus thicknesses was found to be in the neighborhood of 0.1 inches for the full operational range of the separator.
Fluids Engineering, 2005
In the microgravity environment experienced by space vehicles, liquid and gas do not naturally se... more In the microgravity environment experienced by space vehicles, liquid and gas do not naturally separate as on Earth. This behavior presents a problem for two-phase space systems, such as environment conditioning, waste water processing, and power systems. Furthermore, with recent renewed interest in space nuclear power systems, a microgravity Rankine cycle is attractive for thermal to electric energy conversion and would require a phase separation device. Responding to this need, researchers have conceived various methods of producing phase separation in low gravity environments. These separator types have included wicking, elbow, hydrophobic/hydrophilic, vortex, rotary fan separators, and combinations thereof. Each class of separator achieved acceptable performance for particular applications and most performed in some capacity for the space program. However, increased integration of multiphase systems requires a separator design adaptable to a variety of system operating condition...
Applied Thermal Engineering, 2018
With the fast growth of 3D printing technologies, it is promising to apply 3D printed structures ... more With the fast growth of 3D printing technologies, it is promising to apply 3D printed structures to nuclear power plant (NPP) devices for heat transfer enhancement. Since Inconel and steel are commonly used materials for NPP devices (e.g. reactor core components and steam generators), investigations on 3D printed structures made of these materials are of necessary. In the present work, an Inconel smooth plate and three 3D-printed test samples (grooves, pin-fins and cubes) with micro-porous structured surfaces were tested. The smooth plate is made of Inconel and the 3D printed samples are made of steel-bronze mixture. In tests, heat flux, surface temperature, pressure, etc. were obtained by a data acquisition system. In addition, videos were recorded by a NAC high speed camera for visualization study. Comparisons were made among various testing samples to find the optimum structure. Results indicate that all the 3D printed samples show better boiling heat transfer at low heat flux conditions compared to that of the Inconel plate. With the increase of heat flux, the degree of heat transfer enhancement weakens. Among the three 3D printed samples, the cubes sample demonstrates the best heat transfer performance and the pin-fins one shows the worst.
International Journal of Multiphase Flow, 2004
Hydrodynamic measurements are presented for two-phase flows in Mars and Moon gravity conditions. ... more Hydrodynamic measurements are presented for two-phase flows in Mars and Moon gravity conditions. High accuracy pressure drop and flow rate data were obtained using dichlorodifluoromethane (i.e., R-12) as the working fluid flowing in a nominally 11.1 mm inner diameter tube. Measurements were made at Mars gravity, approximately 0.38-g, and Moon gravity, approximately 0.17-g, using NASAÕs KC-135 aircraft. A simplified scaling approach was developed using dimensional analysis and can be used to design an Earthbased test bed to simulate a Mars or Moon gravity prototype. For a specific geometry, a selected working fluid at a fixed temperature and pressure, and a particular flow regime condition, the pressure drop functional scaling equation is a simple, power-law relationship for the Euler number as a function of only the Froude number. The research completed supports the use of Earth-g tests to predict the behavior of two-phase systems for Moon-g and Mars-g applications.
Space technology and applications international forum (STAIF - 97), 1997
ABSTRACT An experimental package was constructed to operate a loop heat pipe (LHP) in microgravit... more ABSTRACT An experimental package was constructed to operate a loop heat pipe (LHP) in microgravity aboard NASA's KC-135 aircraft. Startup of the LHP was performed in flight and ground testing. Data revealed different temperature profiles for similar startups indicating different locations of the vapor and liquid inventories. A sharp increase in evaporator temperature of approximately 10 K followed by a small decrease was very comparable to startups in capillary pumped loops. In contrast, a steady linear rise in wall temperatures with time was used to indicate the absence of liquid in the vapor sections of the evaporator. Temperature transients in the liquid line during particular startups indicate movement of fluid out of the compensation chamber and into the liquid line. Experimental results match expected behavior and show a high degree of repeatability.
AIP Conference Proceedings, 2005
ABSTRACT The desire to utilize enabling, two-phase (gas-liquid) systems for advanced life support... more ABSTRACT The desire to utilize enabling, two-phase (gas-liquid) systems for advanced life support and thermal management are driven by NASA's exploration initiative and the early development of commercial space interests. Two-phase flow heat transfer is highly advantageous over single-phase systems. Two-phase fluid loops provide significant thermal transport advantages over their single-phase counterparts and are able to carry more energy per unit mass than single-phase systems at reduced pumping power per unit mass. These advantages alone offer great reductions in both mass and volume, as well as power requirements; unfortunately, the ability to predict two-phase phenomena such as flow regime transitions and void fraction at microgravity conditions is greatly limited and its development will facilitate the utilization of two-phase systems. The drift flux model is a useful tool to predict the void fraction and thus, the pressure drop. Results of a statistical analysis indicate that for water/air and water-Zonyl/air fluids, the drift velocity, Ugj, is -0.070 and the distribution parameter, C0, is 1.269. These results indicate that the surfactant used had little effect on the model compared to the liquid density difference from the water-glycerin mixture as well as the liquid density and vapor density differences from the refrigerants R12 and R134a.
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Papers by Richard Kurwitz