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Keon Vereen

Undergraduate Major: Aerospace Engineering

McNair Mentor:
Dr. Ranganathan Kumar, Dept. of Mechanical, Materials & Aerospace Engineering (MMAE)

Future Plans: Aerospace Engineering Ph.D.

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Keon Vereen

Keon Vereen was born in Myrtle Beach, South Carolina. He became interested in the engineering discipline at the beginning of high school. Attending the University of Central Florida allowed him to talk to NASA engineers and scientists about the future of the aerospace field.  His current research involves bubble dynamics in nuclear reactor research. In addition to research with the McNair program, he is involved in the Research and Mentoring Program (RAMP). He is interested in obtaining a doctoral degree in the aerospace field and specializing in advanced propulsion technology with an emphasis on electric and nuclear propulsion. The following is an abstract of research Keon completed as an undergraduate at UCF:

Title: Optical Measurements in Nucleate Boiling for High Pressure Refrigerant Flow

Conducted at the University of Central Florida as part of the Ronald E. McNair Scholars Program.

Mentors: Dr. Ranganathan Kumar, Dept. of Mechanical, Materials & Aerospace Engineering (MMAE)

Abstract: In this study, we have investigated the effect of flow rate and high pressure on bubble nucleation of R134a refrigerant in vertical flow boiling system. An experimental facility was built which consists of three major parts: test section, flow loop, and cameras for flow visualization. The test section is made of acrylic plate which contains thin rectangular flow channel (46 cm length, 3.8 cm width, and 3 mm depth), heater, and thermochromic liquid crystal (TLC) sheet. The test section can withstand up to 2.1MPa and the flow loop comprises of tube, pump, intercooler, pressure sensor, and flow regulators which allow regulating both the pressure and flow rate of the refrigerant. The flow through the channel is against the direction of gravity (upflow). The thermochromic liquid crystal (TLC) technique is used to determine the heater surface temperature at high temporal and spatial resolution. Liquid crystals thermo-chromatography uses encapsulated liquid crystals that are sensitive to temperature which is registered through changing color and thus hue angle. The visualization and image recording process is performed by employing two synchronized high resolution and high speed cameras which simultaneously capture colored TLC images as well as bubble nucleation and departure at very high frame rates. The Prosilica cameras used in this study are capable of capturing as high as 1000 frames per second. While a Lab view software works as data and image acquisition system, a customized Matlab program is used to post-process the images which include determining hue angle from TLC images, bubble size, location and frequency. In order to use TLC for temperature measurement, hue versus temperature relationship was first established through in-situ calibration. Then this calibrated relation between hue and temperature was used to obtain the temperature data for experimental runs. Experiments were conducted at different high pressures ranging from 550 kPa to 830 kPa and flow rate ranging 0.95 l/m (liter per minute) to 1.9 l/m in order to investigate the effect of pressure and flow rate of refrigerant. The temporal-temperature response with heat fluxes is also studied. Primary results showed that pressure and flow rate affect bubble nucleation and growth. Bubble frequency was recorded at different heat flux. As expected bubble nucleation rate (frequency) was found to increase significantly with heat flux. Detailed analysis of the effect of these parameters on the bubble nucleation, temperature profile, bubble size and growth are presented.