Measurement of the heat transfer coefficient in the dimpled channel: effects of dimple arrangement and channel height

• Published in: Journal of mechanical science and technology Vol. 23; no. 3; pp. 624 - 630
• Main Authors: Shin, Somin, Lee, Ki Seon, Park, Seoung Duck, Kwak, Jae Su
• Format: Journal Article
• Language: English
• Published: Heidelberg Korean Society of Mechanical Engineers 01.03.2009; Springer Nature B.V; 대한기계학회
• Subjects: Analytical and numerical techniques; Applied sciences; Boundary layer and shear turbulence; Channels; Continuous cycle engines: steam and gas turbines, jet engines; Control; Dimpling; Dynamical Systems; Engineering; Engines and turbines; Exact sciences and technology; Fluid dynamics; Fluid flow; Fundamental areas of phenomenology (including applications); Heat transfer; Heat transfer coefficients; Industrial and Production Engineering; Liquid crystals; Mechanical Engineering; Mechanical engineering. Machine design; Physics; Reynolds number; Studies; Turbulent flows, convection, and heat transfer; Upstream; Vibration; 기계공학; Turbine heat transfer; Transient liquid crystal technique; Turbine blade cooling; Dimple; Thermal characteristic; Transient response; Turbine blades; Thermal factor; Reynolds number; Turbomachinery; Spheres; Heat transfer coefficient; Experimental study; Liquid crystals; Flow reattachment; Cooling by air; Gas turbines; Recirculating flow; Alveolus; Height; Heat transfer
• ISSN: 1738-494X; 1976-3824
• DOI: 10.1007/s12206-008-1211-1

Heat transfer coefficients were measured in a channel with one side dimpled surface. The sphere type dimples were fabricated, and the diameter (D) and the depth of dimple was 16 mm and 4 mm, respectively. Two channel heights of about 0.6D and 1.2D, two dimple configurations were tested. The Reynolds number based on the channel hydraulic diameter was varied from 30000 to 50000. The improved hue detection based transient liquid crystal technique was used in the heat transfer measurement. Heat transfer measurement results showed that high heat transfer was induced downstream of the dimples due to flow reattachment. Due to the flow recirculation on the upstream side in the dimple, the heat transfer coefficient was very low. As the Reynolds increased, the overall heat transfer coefficients also increased. With the same dimple arrangement, the heat transfer coefficients and the thermal performance factors were higher for the lower channel height. As the distance between the dimples became smaller, the overall heat transfer coefficient and the thermal performance factors increased.