An evaporator with communication wick is necessary for compact thermal control system. Two-phase fluid loop systems with the evaporator is very promising in thermal performance as one of the thermal control systems. Developments of high thermal performance and compact or plate-type thermal control systems are demanded for satellites. The evaporator with communication wick was investigated in the heat transfer performance. First, heat transfer characteristics of the evaporator with communication wick were analyzed with calculation. The evaporator was manufac tured on the basis of the analytical evaluation, and the experiments of the heat transfer were carried out using ethanol as the working fluid. As a result, it was found that the overall heat transfer coefficient showed the value of maximum 20 kW/m2 for ethanol in experiment and had the higher value in the case of the working fluid, ammonia, in the analysis.
The present review article reports a series of works the present author has been conducted and some recent topics on the so-called ‘‘self-rewetting’’ fluids. First of all, extraordinary surface tension behavior of high-carbon alcohol aqueous solutions is introduced, and then the potential of the self-rewetting fluids for thermal management applications is emphasized. Secondly, experimental results for wicked heat pipes and pool boiling characteristics at normal gravity condition and some experimental results for wickless heat pipe in reduced gravity conditions are given, and ultra-light weight flexible, inflatable, deployable space radiator concept is presented. Finally, latest topics concerning self-rewetting fluids, such as nano-self-rewetting fluids and micro-channel flow boiling with self-rewetting fluids, are briefly introduced.
This study deals with heat transfer enhancement surface manufactured by thermal spraying. Two thermal spraying methods using copper as a coating material, wire flame spraying (WFS) and vacuum plasma spraying (VPS) , were applied to the outside of copper cylinder with 20 mm OD. The heat transfer performance around the horizontal cylinder under microgravity was evaluated in pool boiling experiments with HCFG123 for heat fluxes between 1.0 and 160 kW/m2 and saturation temperature of 30°C. The microgravity experiments were carried out during a parabolic flight of an airplane. As a result, the surface by VPS produced higher heat transfer coefficient and lower superheat at the onset of boiling under microgravity. For the smooth surface, the effect of gravity on boiling heat transfer coefficient was a little. For the coated surface, a large difference in heat transfer characteristics to gravity was observed in the moderate heat flux range. Heat transfer was improved in gravity transition from hyper-gravity to microgravity. The difference in heat transfer coefficient was a little between the normal gravity and microgravity. For all the test section, test section was covered by vapor with the heat flux of 160 kW/m2 under microgravity.
We have investigated the heat transfer during quenching of the tube by cryogenic fluid for the development of Cryogenic Fluids Management in space. A transparent heated tube was employed for the direct measurement of quench front temperature and its velocity during the tube quenching. These experiments aimed at understanding the effects of gravity on the tube quenching under terrestrial conditions, and the experiments using liquid nitrogen as the test fluid were conducted in the low mass velocity region (75～150 kg/m2s) and four different orientations of gravity (θ= ± 90° , ±45°).The direct measurements of quench front temperature and its velocity succeeded, and the results indicated that the configuration of quench front and heat transfer were affected by gravitational orientation.
In order to obtain the fundamental knowledge of free-surface flows under low-gravity conditions, the unsteady deformations of liquid surface in cylindrical vessels with a vane were experimentally observed with a drop tower. Main concern was placed on the dynamic behavior of the liquid driven by surface force and wetting, and the flow fields were found to be governed by the similarity rule described by Weber number. In addition, the algorithm of CIP-LSM, a numerical method for three-dimensional free-surface flows, was developed on the basis of TCUP scheme, Level Set Method and MARS. The observed flow fields were also simulated by the developed code and the numerical results showed a good agreement with the corresponding experimental data.
Numerical analyses of fluid dynamics were carried out in vane type surface tension tank, which installs propellant management device for microgravity condition. Calculation of static menisci by ``Surface Evolver'' and numerical simulations of dynamic fluid behavior by a simple one-dimensional analytical model and ``FLOW-3D'' were conducted. These results were evaluated by experimental results in microgravity condition employing drop shaft facility. It was shown that calculated static menisci were consistent with experimental ones. Dynamic fluid behavior agreed well with experimental results in the short period after microgravity condition started. However we have to improve the analytical code because the liquid behavior trapped in the vicinity of the vane couldn't be sufficiently simulated. Space evaluation test were carried out after these calculations and experiments. It was shown that vane type surface tension tank worked successfully in microgravity condition on orbit, and exhaust efficient of fuel was achieved 99.2%.