Transient behavior of liquid trap heat pipe thermal diodes

TWO types of diodes, both employing the liquid trap technique, have been developed. One is an a l l aluminum axial groove design (with an outer dimeter of the heat pipe of 1 0 mml, and the other is an all-stainless steel artery design (with an outer diameter of the heat pipe of 7 mm). The diode length including trap is 470 mm. Ammonia has been used as the working fluid in both cases. TWO diodes of the axial groove design, one straight and one bent prototype diode, and one straight development model of the artery desigmhave been investigated. The maximum forward mode performance of the axial groove prototype diodes is 280 W at 2OoC for horizontal orientation. This corresponds to a heat transport capability Of Elm Wcm. The forwardand revecse-mode conductances are 20.8 W/K and 0.039W/K, respectively, for the straight prototype, which results in a turn down ratio of 525. The shutdown time and energy for the straight prototype are 18 min and 1.6 Whr, respectively. The figures for the bent promtype are somewhat better. The artery diode has a maximum forward-mode performance of 130 W at 2OoC for horizontal orientation. This corresponds to a heat transport capability of 3900 Wcm. The forwardand reverse-mode conductances ere 7.7 N/K and 0.0032 W/K, respectively, which results in a high turn down ratio of 2400. Shutdown time and energy are 20 mi and 2.3 Whr, respectively. The restart behavior of both the axial groove and of the artery diodes is reliable. L