Effect of wavy amplitude on the thermo-hydraulic performance of a single-walled wavy microchannel

• Main Author: Koh, Roderick Min Rui
• Other Authors: Ooi Kim Tiow
• Format: Final Year Project
• Language: English
• Published: 2018
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/74731
• Institution: Nanyang Technological University

The possibility of achieving microscale heat transfer using conventional machining methods has been demonstrated. In this study, a microchannel was formed by concentrically mounting an insert with a nominal diameter of 19.4 mm into a hollow cylinder with an inner diameter of 20.0 mm to produce the desired annular gap of 300 μm for the microchannel. Existing studies on wavy microchannel have proven that this channel curvature technique is able to enhance the single-phase convective heat transfer at an affordable pressure drop penalty. Furthermore, this passive enhancement technique can be easily implemented by using computer numerical control (CNC) techniques. Sinusoidal waves were introduced on the surface of the insert to improve heat transfer with distilled water as the working fluid. The enhancement in heat transfer is always accompanied by pressure drop or the increase in demand for pumping power. The experiment conducted utilizes six inserts consisting of three wave lengths and two amplitudes which yield a total of six possible wavelength-amplitude combinations. The plain insert used in this experiment serves as a reference to determine the hydrodynamic and thermal performance of the six inserts with a total of 9 data point collected per insert at Reynolds number ranging from 1300 to 3800 at 1000 W of input power. Results generated shows an improvement in heat transfer in the microchannel for the wavy insert with shorter wave length resulting in a higher Nusselt number at the tested Reynolds numbers however it results in a high Darcy friction factor. The highest heat transfer enhancement is 120 % with an increment of 283 % in friction factor. In this experiment, when compared under the pumping power demand, the wavy insert yields a maximum 53% improvement in efficiency when compared against the plain insert. It was discovered that the amplitude and wavelength strongly influence the performance index