Variation in oscillating heat pipe performance

•Orientation and fluid influence oscillating heat pipe performance variation.•Higher reliability found in a double-sided than single-sided configuration.•Vertically oriented oscillating heat pipes had lower thermal resistance. Oscillating heat pipes have been shown to be an effective means for thermal management. However, the constant, phase-change-powered oscillation can also produce variations in performance. The goal of this research is to quantify performance variation of oscillating heat pipes through repeated tests with closed-loop flat plate oscillating heat pipes. The heat pipes were filled with two different working fluids, butane and R134a, and tested in both double-sided and single-sided cooling configurations, two or three different orientations, and four different power levels, and repeated to quantify the variation in performance, including average thermal resistance, intratest variation (repeatability), intertest variation (temperature fluctuations), and reliability (likelihood of temperature overshoot). Orientation, configuration, working fluid, and power level all influenced the level of variation in performance. In a double-sided configuration, OHPs had lower thermal resistance when oriented vertically. In a single-sided configuration, OHPs had lowest thermal resistance when the evaporator was below the condenser. OHPs were significantly more reliable and experienced smaller temperature fluctuations when in the double-sided than single-sided configuration.