| Summary: | Modern technological advancements of electronics have allowed production of more compact components and have also led to greater heat generation by these devices. This has led to rising demand to cool these devices more efficiently than ever before. Two promising methods to achieve high heat transfer performance is through nucleate pool boiling and submerged jet impingement cooling technique. This report conveys the experimental investigations of the effects of surface modification on the heat transfer performance on a 20 mm by 20 mm electric heating surface. A total of eight modified surfaces were experimented on of which six copper surfaces were polished with abrasive paper to achieve varying levels of the roughness parameter Ra in the range of 3.83 µm to 0.06 µm. Two other surfaces were micro-machined to obtain surfaces with deep and shallow microgrooves. Saturated pool boiling experiments at atmospheric conditions were conducted on the eight surfaces till critical heat flux (CHF) was met. The two microgrooves and one plain surface with Ra of 0.06µm was further experimented on by in cooperating submerged jet impingement cooling with Reynold number of 12000. Besides an anomaly, general trend of the pool boiling experiment indicates that the heat transfer coefficient and CHF was improved with increasing surface roughness. The submerged jet impingement cooling experiment confirms that the average heat transfer coefficient for plain, microgroove deep and microgroove shallow surface was increased by 24%, 43% and 69% respectively as compared to pool boiling. The CHF was also further enhanced in comparison to pool boiling. An anomaly during the pool boiling experiment with surface Ra of 0.89 µm suggest that roughness parameter, Ra is not the only parameter that influences the heat transfer performance. Further study on bubble dynamics and active nucleation site would be highly anticipated to identify the most fundamental factor that influences the heat transfer performance. For future studies, submerged jet impingement array could be introduced with thermocouple placed in an orientation to capture 3-dimensional heat transfer through heating element.
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