Design and development of water chiller enhanced by low frequency ultrasonic waves

Name: Wannarat Rakpakdee

LCSH: Kasetsart University -- Dissertations. D.Eng. (Mechanical Engineering) 2022

Classification :.LCCS: TJ260

LCSH: Kasetsart University. -- Department of Mechanical Engineering -- Dissertations

LCSH: Ultrasonic waves

LCSH: Liquid crystals

LCSH: Heat -- Transmission

LCSH: Heat exchangers

Abstract: The research focuses on enhancing heat transfer on a heat exchanger in a water chiller using low-frequency ultrasonic waves. For the basic research, the experiment was carried out in a rectangular duct for water flow across a cylinder under 25 kHz ultrasound. Thermocouples and thermochromic liquid crystals were applied to investigate the heat transfer characteristics on the cylindrical surface. In addition, the experiment on heat transfer enhancement was investigated by a combination of 25 kHz ultrasound together with Al2O3-water nanofluid in a square duct under constant heat flux at the bottom wall. Finally, the application of ultrasound was examined for heat transfer and pressure drop of the heat exchanger in the 5-ton commercial water chiller. According to the results of water flowing across the cylinder, ultrasound can enhance the local heat transfer capability by up to 2.37 in comparison to the case without waves. The results also revealed that the waves can travel along the stream flow. The pressure drop ratio that occurred when employing ultrasound was in the range of 0.88–1.27, depending on the ultrasonic wave location. The mechanisms on the curved surface when ultrasound was applied were successfully visualized using thermochromic liquid crystals coated on the cylindrical surface. In addition, the results of the experiment on heat transfer enhancement by using ultrasonic waves and nanofluids showed that ultrasound could also boost heat transfer capability when combined with nanofluids. However, the influence of ultrasonic waves was attenuated as the concentration of the nanofluid was increased. The highest local heat transfer capability using ultrasound from a single transducer was 1.31 in Al2O3 with a volume fraction of 6.1%, and it increased to 1.58 in Al2O3 with a volume fraction of 1.5% using double transducers. Finally, the heat exchanger’s experimental results demonstrated that modifying the inlet flow configuration from two to four channels boosted the heat transfer capability by 11.6%. When the ultrasound was applied to the heat exchanger, the heat transfer capability was also enhanced by approximately 9%. By modifying the inlet configuration, the pressure drop on the shell side was decreased by 36.8–39.1%, and the pressure drop was changed by less than 1% because of the waves.

Kasetsart University. Office of the University Library

Address: Bangkok

Email: tdckulib@ku.ac.th

Name: Weerachai Chaiworapuek

Role: Thesis Advisor

Name: Mitsuhiro Fukuta

Role: Thesis CO-Advisor

Name: Masaaki Motozawa

Role: Thesis CO-Advisor

Created: 2022

Modified: 2025-07-27

Issued: 2025-07-27

วิทยานิพนธ์/Thesis

application/pdf

URL: https://www.lib.ku.ac.th/KUthesis/2565/wannarat-rak-all.pdf

CallNumber: TJ260 .W37

eng

DegreeName: Doctor of Engineering

Level: Doctoral Degraee

Descipline: Mechanical Engineering

Grantor: Kasetsart University

©copyrights Kasetsart University

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