Design and development of a shape memory alloy activated heat pipe-based thermal switch

    Authors

    O. Benafan; W. U. Notardonato; B. J. Meneghelli;R. Vaidyanathan

    Comments

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    Abbreviated Journal Title

    Smart Mater. Struct.

    Keywords

    NEUTRON-DIFFRACTION; IN-SITU; R-PHASE; TRANSFORMATION; BEHAVIOR; NITI; TEMPERATURES; DEFORMATION; TI50NI47FE3; RECOVERY; Instruments & Instrumentation; Materials Science, Multidisciplinary

    Abstract

    This work reports on the design, fabrication and testing of a thermal switch wherein the open and closed states were actuated by shape memory alloy (SMA) elements while heat was transferred by a two-phase heat pipe. The motivation for such a switch comes from NASA's need for thermal management in advanced spaceport applications associated with future lunar and Mars missions. As the temperature can approximately vary between -233 and 127 degrees C during lunar day/night cycles, the switch was designed to reject heat from a cryogen tank into space during the night cycle while providing thermal isolation during the day cycle. A Ni47.1Ti49.6Fe3.3 (at.%) alloy that exhibited a reversible phase transformation between a trigonal R-phase and a cubic austenite phase was used as the sensing and actuating elements. Thermomechanical actuation, accomplished through an antagonistic spring system, resulted in strokes up to 7 mm against bias forces of up to 45 N. The actuation system was tested for more than thirty cycles, equivalent to one year of operation. The thermal performance, accomplished via a variable length, closed two-phase heat pipe, was evaluated, resulting in heat transfer rates of 13 W using pentane and 10 W using R-134a as working fluids. Experimental data were also compared to theoretical predictions where possible. Direct comparisons between different design approaches of SMA helical actuators, highlighting the effects of the helix angle, were carried out to give a layout of more accurate design methodologies.

    Journal Title

    Smart Materials and Structures

    Volume

    22

    Issue/Number

    10

    Publication Date

    1-1-2013

    Document Type

    Article

    Language

    English

    First Page

    17

    WOS Identifier

    WOS:000324645000041

    ISSN

    0964-1726

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