Session: 11-01: Micro/Miniature Two-Phase Devices/ Systems

Paper Number: 132056

132056 - Three-Dimensional Oscillating Heat Pipe: Flow Pattern Transition and Heat Transfer Performance 

Abstract: 

The traditional oscillating heat pipe (OHP), due to its symmetrical structure, primarily transfers heat in the form of pulsation during operation. At the same time, the oscillation, stagnation, and flow of the working fluid exhibit randomness. The flow pattern of the working fluid inside an OHP can be altered through structural design and operating conditions to promote the formation of stable unidirectional flow. Experimental research was conducted on a three-dimensional helical OHP with 11 bends, employing asymmetric heating and cooling. Deionized water was used as the working fluid with a fill ratio of 50%. The lengths of the evaporator, adiabatic section, and condenser were 40mm, 76mm, and 64mm, respectively. The temperature distribution in the OHP was analyzed to understand the variations in flow and heat transfer at different power levels. As the temperature of the evaporator section increased, the OHP started to operate. In the initial stage at low power, due to insufficient driving force, the flow pattern inside the OHP was chaotic, primarily operating in an oscillatory manner. With increasing power, the working fluid could form stable unidirectional flow within the OHP and maintain stability within a certain power range. Further increasing power, at specific power points, a flow pattern transition to unidirectional flow occurred inside the OHP, with unidirectional flow as the main pattern accompanied by reciprocating pulsation. During the flow pattern transition process, the temperature of the evaporator section decreased and the temperature of the condenser section increased. The heat transfer performance significantly improved. Further increasing power caused the disappearance of the flow pattern transition process. Finally, at higher power levels, the OHP maintained stable pulsation. Through comprehensive analysis of flow and heat transfer performance, the results indicate: (1) Three-dimensional OHP with asymmetric heating and cooling can promote the formation of stable unidirectional circulation flow within the OHP. (2) Heating power influences the flow of the working fluid and the OHP exhibits adaptability to power changes, resulting in different flow patterns at different power levels. (3) The flow pattern inside the OHP has a significant impact on heat transfer performance. Unidirectional flow, accompanied by reciprocating pulsation can significantly enhance heat transfer. By discovering the flow pattern transition in the three-dimensional OHP, a deeper understanding is gained of the changes in flow patterns under different operating conditions and their impact on heat transfer performance. This provides a beneficial direction for improving and optimizing the heat transfer performance of OHPs.

Presenting Author: Zhang Liu Dalian Maritime University

Presenting Author Biography: Male, Ph.D. student in Dalian Maritime University, mainly engaged in research on enhancing heat transfer in pulsating heat pipes.

Authors:

Zhang Liu Dalian Maritime University
Yulong Ji Dalian Maritime University
Dengke Zhang Dalian Maritime University