Experimental analysis of a Flat Plate Pulsating Heat Pipe with Self-ReWetting Fluids during a parabolic flight campaign

Abstract

A Flat Plate Pulsating Heat Pipe (FPPHP) filled with an ordinary liquid (water) and a self-rewetting mixture (dilutes aqueous solutions of long-chain alcohols with unusual surface tension behaviour) is investigated under variable gravity conditions on board a 'Zero-g' plane during the 65 th Parabolic Flight Campaign of the European Space Agency. The FPPHP thermal performance in terms of evaporator and condenser temperatures, start-up levels and flow regimes is characterized for the two working fluids and a power input ranging from 0 to 200W (up to 17 W/cm 2 at the heater/evaporator wall interface). The experimental set-up also includes a transparent plate enabling the visualization of the oscillating flow patterns during the experiments. For a low power input (4 W/cm 2 ), the pulsating heat pipe filled with pure water is not able to work under low-g conditions, because the evaporator immediately exhibits dry-out conditions and the fluid oscillations stops, preventing heat transfer between the hot and cold side and resulting in a global increase of the temperatures. On the other hand, the FPPHP filled with the self-rewetting fluid runs also during the microgravity phase. The liquid rewets several times the evaporator zone triggering the oscillatory regime. The selfrewetting fluid helps both the start-up and the thermal performance of the FPPHP in microgravity conditions.

Acceleration control of a multi-rotor UAV towards achieving microgravity

“…Therefore, as seen from Fig. 10d, the UAV was not able to maintain constant vertical acceleration throughout the manoeuvre, 8 and it does not achieve microgravity. The only UAV to achieve mean acceleration levels close to microgravity apart from our UAV is the one shown in Fig.…”

“…The contemporary Earth-based microgravity test facilities are drop towers [6,13,21,25] and fixed-wing manned aircraft performing parabolic manoeuvres [8,26]. The performance of a microgravity test facility is quantified in terms of the maximum acceleration experienced during the test-g-peak, the duration for which microgravity can be achieved-gtime, the mean acceleration experienced during this time-glevel, and the standard deviation about this mean-g-quality.…”

Innovations in pulsating heat pipes: From origins to future perspectives

“…In the above-mentioned temperature range, the inverse Marangoni effect is supposed to move the vapour bubbles from the hot zone to the cold zone and to recall the liquid slugs from the condenser and rewet the evaporator. By the time being preliminary results show modest performance enhancements in the gravity assisted mode [79], while promising outcomes have been found on the thermal response in microgravity conditions [80].…”

Experimental analysis and transient numerical simulation of a large diameter pulsating heat pipe in microgravity conditions

“…This possibility was first speculated by Gu et al [2] and later proved on board a parabolic flight with a tubular PHP filled with FC-72 by Mangini et al [10] and Mameli et al [11]. Cecere et al [12] and Ayel et al [13] tested a copper flat PHP filled respectively with a self-rewetting fluid and FC-72 during the parabolic flights. However, in all the above cases, due to the short duration of microgravity periods, it was not possible to reach a pseudo-steady state.…”