Session: 11-16-02: Oscillating Heat Pipes and Thermosiphons

Paper Number: 112416

112416 - An Experimental Investigation of the Relationship Between Evaporator and Condenser Sizes With Oscillating Heat Pipe Start-Up 

Oscillating Heat Pipes (OHPs) are unique two-phase heat transfer devices with many advantages over standard and more widely adopted thermal control devices, including an ability to operate passively, with high effective thermal conductivity, under high heat fluxes, under a wide range of temperatures, and with very few design constraints. OHPs operate based on the process of evaporating and condensing a working fluid on opposite ends of a series of serpentine channels. The pressure difference causes an oscillating behavior of the liquid along the direction of the channels enabling a high heat transfer rate. The capability of this technology has garnered much attention and interest for a variety of applications. While as a thermal management device, OHP technology shows much promise, there is still much to be understood about the fundamental principles of its operation. One of the most important aspects of OHP operation but that still needs further understanding is the phenomena known as “start-up”, which is creating the proper conditions to enable the operating, oscillatory process of an OHP to begin. In this research, experimental testing is performed to investigate the relationship between evaporator and condenser length and OHP start-up. In this study, combinations a small, medium, and large length evaporators and condensers were tested for a 1mm square channel with a working fluid of R134a at a filling ratio of 50% to find the minimum amount of heat that would start-up the OHP. From this testing, it was found that both a longer evaporator and condenser allow for less heat to start-up the OHP. Still, while a large condenser can independently lead to early start-up of an OHP, for a large evaporator, there is still a dependency on the size of condenser when it comes to how much power is required. Furthermore, the process of start-up relies heavily on the history of the OHP, i.e. the initial liquid-vapor distribution of the working fluid in the channels. Outlined in this paper is a developed method of “resetting” the liquid distribution to allow for consistent start-up results and overcoming any adverse history from previous operation of the OHP. Furthermore, it was found and investigated, under the conditions of the experiment, a zero-heat input method of confirming a suitable liquid-vapor distribution. This work hopes to contribute to the experimental parametric studies of Oscillating Heat Pipes to help better understand the principles of its operation and allow for more common use in a variety of applications.

Presenting Author: Spencer Miesner California State University, Los Angeles

Presenting Author Biography: Spencer Miesner is a master's student in Mechanical Engineering at California State University, Los Angeles as well as a graduate intern at Jet Propulsion Laboratory. The current focus of Spencer’s research is in exploring the use of Oscillating Heat Pipe technology for spacecraft applications.

Authors:

Spencer Miesner California State University, Los Angeles
Neyda Bautista California State University, Los Angeles
Kieran Wolk University of California, Los Angeles
Ben Furst Jet Propulsion Laboratory
Takuro Diamaru Jet Propulsion Laboratory
Eric Sunada Jet Propulsion Laboratory
Scott Roberts Jet Propulsion Laboratory
John Bellardo California Polytechnic State University, San Luis Obispo
Jim Kuo California State University, Los Angeles