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Description
Based on the electrohydrodynamic (EHD) technology mastered by APR Technologies, a Swedish SME, the core of APR's space products is a small-sized patented liquid EHD pump. This pump enables very deterministic and fast regulation of fluid flow, thereby controlling thermal conductance between thermal interfaces in active thermal control systems. Its main advantage is its operation across a wide temperature and thermal flux range with power consumption below 2 W, in OFF mode, power consumption is 0 W. Since the pump has no moving parts, it experiences no mechanical wear or vibrations.
During 2023 and 2024, APR's space product portfolio of thermal switches and pumped loops has grown, with three branches for each product family.
EHD pumped loops are built similarly to mechanically pumped loops, with tubing connecting the heat exchangers (cold plates), pump, and volume compensation. The mechanical pump is replaced with an EHD pump, which has the advantage of no moving parts. The pumped loop family consists of a cryogenic low-OFF single-phase loop at TRL 4 and a single-phase loop at TRL 5 (3 kg) targeting telecom with a 100 W load. Additionally, an EHD pumped two-phase loop targeting high-power applications has been demonstrated in a national activity and is currently at TRL 4.
EHD pumped thermal switches are compact devices where the thermal conductance between two interfaces can be modulated by controlling the fluid pumping between the interfaces within the device volume. In zero gravity, the stationary fluid has a high thermal resistance, leading to low thermal conductance between the interfaces in OFF mode. Conversely, in ON mode a large amount of heat can be transported by the pumped liquid. The thermal switch developed within the Neosat program targets 150 W loads, has a mass of 1400 g, and a turndown ratio of about 25. Two smaller thermal switches, developed to TRL 5 in a GSTP activity for lunar surface exploration batteries (150 g) and smallsats (260 g), have anticipated turndown ratios of over 50 and 11, respectively.
