The oscillating heat pipe is a novel, simply formed, wickless heat pipe that relies on the phase-change-induced motion of a contained working fluid to transport heat between the evaporator (hot end) and condenser (cold end). The improved heat transfer capability, simplicity, and reduced mass of oscillating heat pipes have led to great interest in the oscillating heat pipe. This paper details the terrestrial and microgravity validation of an ultrasonic consolidation manufactured structurally embedded oscillating heat pipe. It is shown that 1) for conditions in which an oscillating heat pipe is terrestrially orientation-independent, it is also likely to be gravity-independent, and 2) for conditions in which an oscillating heat pipe is not terrestrially orientation-independent, it is likely to perform better in microgravity than in a terrestrial environment. Additionally, this test campaign provides evidence that the "knee" found in most oscillating heat pipe performance versus input heat curves roughly corresponds to the point at which 1) oscillating heat pipe performance variation drops off, 2) oscillating heat pipe performance becomes orientation-independent, and 3) the oscillating heat pipe performance becomes gravity-independent. These results can be used to better predict oscillating heat pipe performance using terrestrial test data.
The ASETS-II experiment consists of three oscillating heat pipes (OHPs), an electronics box, and mounting structures that control boundary conditions. Each OHP consists of 34 channels in a typical single-layer closed loop design. Butane was selected as the working fluid for OHP #1 and #2 for its performance stability. R-134a was selected for OHP #3 in order to explore the Bond number limit’s influence on OHP operation in microgravity.
The ASETS-II Flight and Flight Spare hardware were subjected to a comprehensive set of ground testing to baseline performance prior to flight testing. For most test conditions, the Flight and Flight Spare test results for OHP #1 and OHP #2 are within the margin of uncertainty in the measurements. OHP #3 on the Flight hardware performs similarly to OHP #3 on the Flight Spare hardware; however, the difference in performance is outside the margin of uncertainty in the measurements. This variation in performance may be attributable to the fact that OHP #3 is being pushed to operate near its Bond number limit.
This paper provides an analysis of the thermal performance of aerogel insulation used during a long-term International Space Station (ISS) flight experiment aboard Space Test Program -Houston 3 (STP-H3). The Variable emissivity device Aerogel insulation blanket, Dual zone thermal control Experiment suite for Responsive space (VADER) investigation tested a variable emissivity radiator and a new form of multi-layer insulation that used aerogel as the thermal isolator. An effort was made to evaluate the performance of the aerogel insulation over the active flight period. The available flight temperature data shows no evidence of deterioration or change in the aerogel insulation's thermal performance during the two-year on-orbit period.
This study investigates the wettability of fluid-solid interactions of interest for oscillating heat pipe (OHP) applications. Measurements were taken using two techniques: the sessile drop method and capillary rise at a vertical plate. Tested surface materials include copper, aluminum, and Teflon PFA. The working fluids tested were water, acetone, R-134a, and HFO-1234yf. A novel low-pressure experimental setup was developed for refrigerant testing. Results show that the refrigerants have significantly lower hysteresis than the water and acetone-based systems, which is thought to lead to better heat transfer in OHP design.
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