Session: 11-09-02: Phase-Change Processes: Fundamentals and Applications

Paper Number: 145111

145111 - Exploring the Influence of Channel Diameter, Fill Ratio, and Adiabatic Length Variation on Long Oscillating Heat Pipes 

Oscillating heat pipes (OHPs) offer several advantages to traditional heat pipes; however, OHP operations have not been fully characterized, especially the operating limits of the long OHPs. Prior research has shown that OHPs thermal performance is affected by multiple parameters such as working fluid being used, diameter of the channels, size of the condenser and evaporator, and length of the adiabatic section. This study aims to measure the effects of changing adiabatic length, channel diameter, and fill ratio on thermal performance. The importance of understanding how these parameters affect thermal performance allows us to determine if this technology can be applied to engineering applications such as spacecraft thermal control. Multiple performance tests were conducted on three long OHPs, with total lengths ranging from 451 mm to 770 mm. The two-channel diameters that were tested were 1.1 mm and 1.9 mm channel diameters and the adiabatic lengths were 610 mm and 305 mm. The experimental setup for OHP testing consisted of mounting the OHP on a testbed with evaporator and condenser sections connected to heating pads and cooling plate, respectively.  A total of nine K-type thermocouples were attached to the OHP’s: Three on the evaporator section, three on the adiabatic section, and three on the condenser section. The system was insulated to reduce the effects of heat loss to the environment. The temperature of the cold plate was maintained at 10 ºC using a chiller. Power was supplied to the evaporator starting at 10 watts at an increment of 10 watts each time the temperatures reached steady-state conditions to a maximum of 65 watts or until dry-out. The OHP’s were set up horizontally, so they would not be gravity-assisted during operation. Their overall performance was determined by calculating the effective thermal conductivity of each OHP. These tests have shown that the thermal performance of the OHPs is affected by channel diameter, adiabatic length, and fill ratio. The effective thermal conductivity was seen to do better overall for all the OHPs at a 50% fill ratio. Additionally, it was noted that reducing the diameter of the OHP resulted in no startup occurring at a 70% fill ratio. Moreover, at a 30% fill ratio, none of the OHPs initiated startup. These results provide insight into what limitations the long OHPs have, which helps us determine if they can be applied universally to any configuration or if they have certain dimensional constraints. 

Presenting Author: Marcos Santana California State University, Los Angeles

Presenting Author Biography: Mechanical engineering Undergrad at California State University

Authors:

Marcos Santana California State University, Los Angeles
Anthony Cabrera California State University, Los Angeles
Apryl Sperling California State University, Los Angeles
Jim Kuo California State University, Los Angeles
John Bellardo California Polytechnic University, San Luis Obispo
Takuro Daimaru Jet Propulsion Laboratory
Eric Sunada Jet Propulsion Laboratory
Scott Roberts Jet Propulsion Laboratory