A MEMS Turbopump for High-Temperature Rankine Micro Heat Engines—Part II: Experimental Demonstration

Amnache, Amrid; Liamini, Mokhtar; Gauthier, Félix; Beauchesne-Martel, Philippe; Omri, Mohamed; Fréchette, Luc

doi:10.1109/jmems.2020.3008625

Cited by 6 publications

(3 citation statements)

References 15 publications

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“…In terms of information applications, achieving supercritical turbulent flow conditions has the potential to remarkably enhance the cooling of the nextgeneration of processors to help boost the digital future [48]. Furthermore, to overcome the small efficiencies resulting from the laminar flows encountered [49], the successful design and deployment of future microsize heat engines, refrigerators and heat exchangers will inevitably have to focus first on achieving supercritical fluid turbulence at the microscale. As an example, typical current microchips generate approximately 1.5 kW/cm 2 of heat [50] that needs to be efficiently dissipated by means of microfluidic cooling systems.…”

Section: Importance In Heat Transfer Applicationsmentioning

confidence: 99%

Thermophysical Analysis of Microconfined Turbulent Flow Regimes at Supercritical Fluid Conditions in Heat Transfer Applications

Bernades

Jofre

2022

Journal of Heat Transfer

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The technological opportunities enabled by understanding and controlling microscale systems have not yet been capitalized to disruptively improve energy processes. The main limitation corresponds to the laminar flows typically encountered in microdevices, which result in small mixing and transfer rates. This is a central unsolved problem in the thermal-fluid sciences, in what some researchers refer to as “quot;ab-on-a-chip and energy - microfluidic frontier”. Therefore, this work focuses on analyzing the potential of supercritical fluids to achieve turbulence in microconfined systems by studying their thermophysical properties. In particular, a real-gas thermodynamic model, combined with high-pressure transport coefficients, is utilized to characterize the Reynolds number achieved as a function of supercritical pressures and temperatures. The results indicate that fully-turbulent flows can be attained for a wide range of working fluids related to heat transfer applications, power cycles and energy conversion systems, and presenting increment ratios of O(100) with respect to atmospheric (subcritical) thermodynamic conditions. The underlying physical mechanism to achieve relatively high Reynolds numbers is based on operating within supercritical thermodynamic states (close to the critical point and pseudo-boiling region) in which density is relatively large while dynamic viscosity is similar to that of a gas. In addition, based on the Reynolds numbers achieved and the thermophysical properties of the fluids studied, an assessment of heat transfer at turbulent microfluidic conditions is presented to demonstrate the potential of supercritical fluids to enhance the performances of standard microfluidic systems by factors up to approximately 50x.

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Section: Importance In Heat Transfer Applicationsmentioning

confidence: 99%

Thermophysical Analysis of Microconfined Turbulent Flow Regimes at Supercritical Fluid Conditions in Heat Transfer Applications

Bernades

Jofre

2022

Journal of Heat Transfer

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“…The piston provides mechanical work through a unique oval-shaped phase change thermodynamic cycle [5]. There are other examples of micro heat engines, including micro gas turbines [14,15] and micro steam turbines [16][17][18], which demonstrate traditional Brayton and Rankine thermodynamic cycles, respectively. They offer high power (watt-scale), but have the complexity of high-speed rotating parts.…”

Section: Introductionmentioning

confidence: 99%

Capillary enhanced phase change in a microfabricated self-oscillating fluidic heat engine (SOFHE)

Karami,

Tessier-Poirier,

Leveille

et al. 2023

J. Micromech. Microeng.

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This paper reports the design, fabrication, and characterization of a miniaturized version of a self-oscillating fluidic heat engine (SOFHE) for thermal energy harvesting. This new design includes capillary corners of a square cross-section, as well as an etched capillary path on the bottom wall that improves the performance in terms of stability and mechanical power owing to the enhanced phase change. The engine consists of a vapor bubble trapped in a microchannel by an oscillating liquid plug (acting as a piston) set in motion by periodic evaporation and condensation in the vapor bubble. The underlying physics of the oscillations is similar to those of a single-branch pulsating heat pipe. The channel is microfabricated by anodically bonding a grooved glass wafer (top and sidewalls) to a silicon wafer (bottom wall). To further increase the phase change, two more channels are fabricated with an etched capillary path on the bottom wall at two different widths of 25 and 50 µm and a depth of 100 µm. This is the first miniaturized SOFHE that generates a reliable amplitude in the millimeter range. By measuring the change in the volume of the vapor bubble and the frequency, we calculated the change in pressure using the momentum balance on the liquid plug, and then calculated the work, mechanical power, and power density. We observed that the addition of the etched capillary path at a width of 50 µm led to a twofold increase in the amplitude (from 1.6 to 4 mm) and consequently a fivefold increase in the generated power (from 7 to 39 µW). This study opens a new path towards designing different wicking structures to maximize the amplitude and power density of SOFHE, making it a promising thermal energy harvester to power wireless sensors.

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“…Energy harvesting has emerged to address this need by generating electricity from available energy in the ambient. Thermal energy harvesters converts heat directly into electricity like thermoelectric generators (TEGs) [1], or indirectly (thermal-tomechanical-to-electrical) like micro heat engines coupled with an electromechanical transducer [2][3][4][5][6]. A self-oscillating fluidic micro heat engine (SOFHE) is a recently discovered micro heat engine with a unique thermodynamic cycle [7].…”

Section: Introductionmentioning

confidence: 99%

Effect of evaporator length on the performance of a self-oscillating fluidic heat engine (SOFHE)

Karami,

Tessier-Poirier,

Léveillé

et al. 2023

Progress in Canadian Mechanical Engineering. Volume 6

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This paper reports the effect of evaporator length on the performance of a self-oscillating fluidic heat engine (SOFHE). The SOFHE is a thermal energy harvester, when coupled with an electro-mechanical transducer that was proposed to power wireless sensors widely used in the Internet of Things (IoT). The mechanical power of the SOFHE is in the order of fraction of milliwatts, which makes it a promising power supply for a range of wireless sensors with the power requirements of 10s µW. The SOFHE consists of a vapor bubble trapped by an oscillating liquid plug acting as a piston. The working principle of the SOFHE is similar to a singlebranch pulsating heat pipe. The engine is a small tube (inner diameter of 2 mm) filled with deionized water heated from a closed end and cooled from the opposite open end. By perturbing the equilibrium of the vapor bubble-liquid plug, oscillation start and are sustained by cyclic evaporationcondensation from a thin film in the vapor bubble. To characterize SOFHE's mechanical power as a function of the evaporator length, measurements of pressure, oscillation amplitude, and frequency are conducted. As the evaporator length decreases (from 7 cm to 1 cm), the oscillation amplitude decreases (from 5.9 mm to 1.5 mm) while the frequency increases (from 27 Hz to 52 Hz). In theory, the power of SOFHE is proportional to the square of frequency and amplitude, so the trend in power is not obvious given the opposing effects. The results show a decrease in the mechanical power from 380 µW to 180 µW, which implies that the negative effect of the amplitude decrease dominates over the increase in frequency. A fourfold decrease was also observed in the net evaporation rate (from 1027 to 242 µg/s), which explains why the amplitude decreases with the evaporator length. The research findings contribute to the design of both SOFHEs and pulsating heat pipes by suggesting that a longer heated zone improves the performance.

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A MEMS Turbopump for High-Temperature Rankine Micro Heat Engines—Part II: Experimental Demonstration

Cited by 6 publications

References 15 publications

Thermophysical Analysis of Microconfined Turbulent Flow Regimes at Supercritical Fluid Conditions in Heat Transfer Applications

Thermophysical Analysis of Microconfined Turbulent Flow Regimes at Supercritical Fluid Conditions in Heat Transfer Applications

Capillary enhanced phase change in a microfabricated self-oscillating fluidic heat engine (SOFHE)

Effect of evaporator length on the performance of a self-oscillating fluidic heat engine (SOFHE)

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