Thesis Defense - Tolga Emir (MSME)

Tolga Emir – M.Sc. Mechanical Engineering

Prof. Dr. Mehmet Arik – Advisor

Date: 25.07.2023

Time: 14.00

Location: AB1 246

“EXPERIMENTAL INVESTIGATION ON POOL BOILING HEAT TRANSFER OVER MICROTEXTURED, ADDITIVE MANUFACTURED SURFACES, AND EXTENDED OPERATION”

Prof. Dr. Mehmet Arık, Özyeğin University

Assist. Prof. Dr. Altuğ Melik Başol, Özyeğin University

Assoc. Prof. Dr. Murat Çelik, Boğaziçi University

Abstract:

The ever-increasing population and rising living standards require the development of high-performance, efficient, and safe technologies. Compact thermal systems face challenges due to limited space availability, while waste heat reduction and efficient cooling become crucial. Pool boiling heat transfer offers high-performance cooling opportunities for thermal problems especially electronics limited with high heat fluxes, and has been extensively studied over the last eight decades. This study aims to enhance boiling heat transfer (BHT) by incorporating artificial cavities through microdrill manufacturing and additive manufactured (AM) microchannel surfaces. Additionally, the development of oxide layers and their impact on surface performance are investigated. The boiling performance of surfaces with micro-drilled artificial cavities is analyzed under different operating conditions. In addition, the study examines the effect of microchannel geometries, specifically rectangular, V-shape, and inverse V-shape channels fabricated using laser powder bed fusion, on BHT. The influence of surface roughness on heat transfer is compared between additive manufactured surfaces and conventionally polished surfaces. Oxide layer development and its effect on heat transfer are explored on copper substrates under various operating scenarios. De-ionized (DI) water and 3M™ Novec™ hydrofluoroether (HFE-7100) Engineered Fluid were preferred as working liquids to be suitable for the cooling of electronic systems priorly. In this study, the tests were conducted at between 0 - 10 K subcooling temperatures and 1 - 1.5 Bar pressures. The experimental analysis includes contact angle measurements, confocal microscopy, scanning electron microscopy, X-ray diffraction, and high-speed imaging for bubble formation. These investigations contribute to understanding and improving heat transfer performance in boiling systems.

Bio:

A student with a fully funded scholarship in B.Sc and M.Sc. programs in mechanical engineering at Özyeğin University, Türkiye. He worked as a student assistant at the Energy Efficient Lighting Technologies Research, Development, Demonstration and Education Center (EVATEG Center) under the supervision of Prof. Dr. Mehmet Arik and Assoc. Prof. Dr. Mete Budakli. Besides my tasks, such as assistance in the courses and tutoring in exercises, I have developed and commissioned an experimental setup for pool boiling research, on which I studied the thermal performance and bubble formation on different heater surfaces immersed in water and refrigerants. He received funding during my Bachelor-program from The Scientific and Technological Research Council of Türkiye (TÜBITAK) upon the submission of my proposal. The results which were collected from my investigation have been orally presented at several national and international conferences, while one of our papers has been recently awarded the Hartnett-Irvine Award (2022), which The International Centre gives for Heat and Mass Transfer (ICHMT). Concerning contributions in journals, one review paper was published, and two experimental SCI papers were submitted, and currently preparing two more papers on boiling heat transfer for submission in international journals. He’s familiar with the fundamentals of heat and mass transfer, fluid mechanics as well as measurement techniques and has studied various applications of these physics by being temporarily involved in groups working in EVATEG on synthetic jet cooling, frost formation, and partial condensation.