Temperature uniformity of a hybrid pressure-controlled loop heat pipe with a heat pipe liner

A hybrid pressure-controlled loop heat pipe (PCLHP) was designed to improve the temperature uniformity of the pneumatically controlled temperature field of a conventional PCLHP. The hybrid PCLHP contained an annular heat pipe liner (HPL) in the cylindrical working space to equilibrate the axial temperature profile. To investigate the effects of the HPL construction on the spatial uniformity and transient response of the temperature field generated by the hybrid PCLHP, three different types of HPLs were fabricated; two annular heat pipes, one with dual wicks on the inner and outer walls (DWHPL) and one with a single wick only on the inner wall (SWHPL), and one aluminum liner containing multiple commercial rod-type heat pipes (LMCHP) were tested. Overall, the annular HPL with a dual wick structure (DWHPL) provided significant enhancement in the spatial temperature uniformity with the reduced expense of increased response times; for example, an approximately tenfold improvement in temperature uniformity was attained (e.g., approximately 10 mK temperature depressions over a 10 cm distance), with comparatively fast responses to temperature changes due to the formation of dual liquidvapor phase interfaces on the inner and outer walls of the HPL.