The working fluids of loop heat pipes (LHPs) play an important role in the operation of the LHPs by influencing the operating temperatures and the heat transfer limits. Therefore, the proper selection of a working fluid is a key practice in LHP fabrication, and there has been a high demand for an appropriate index that enables the quantitative comparison of the steady-state thermal performance of the working fluids. In this work, a figure of merit for LHPs was theoretically derived and experimentally verified. In particular, the pressure losses in the LHP operation were balanced with the saturation pressure difference between the evaporator and the compensation chamber to derive the figure of merit. This derived figure of merit for LHPs successfully predicted the steady-state thermal performance of the tested working fluids within the variable conductance regime. In the constant conductance regime, the differences in the condenser cooling capacity and in the liquid subcooling for different working fluids determined the thermal performance of each working fluid. The limitations and prospects of the proposed figure of merit were discussed in detail.
Derivation and Validation of a Figure of Merit for Loop Heat Pipes With Medium Temperature Working Fluids
Contributed by the Heat Transfer Division of ASME for publication in the JOURNAL OF HEAT TRANSFER. Manuscript received April 14, 2015; final manuscript received January 4, 2016; published online February 17, 2016. Assoc. Editor: Amitabh Narain.
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Joung, W., Lee, J., Lee, S., and Lee, J. (February 17, 2016). "Derivation and Validation of a Figure of Merit for Loop Heat Pipes With Medium Temperature Working Fluids." ASME. J. Heat Transfer. May 2016; 138(5): 052901. https://doi.org/10.1115/1.4032534
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