Time-Resolved Measurement of Enhanced Phase Change by a Fiber in an Oscillating Two-Phase Plug Flow

Karami, Nooshin; Tessier-Poirier, Albert; Nikkhah, Alihossein; Léveillé, Étienne; Fréchette, Luc

doi:10.1109/therminic57263.2022.9950692

Cited by 4 publications

(8 citation statements)

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“…The oscillations are sustained for hours with a constant amplitude, demonstrating highly reliable and repeatable behavior. This design also guarantees the start-up of oscillations without the need to insert an additional wicking structure, as is required for the mesoscale SOFHE [4,5,10,11]. Therefore, the start-up and sustainability of the micro SOFHE are achieved by increasing the rate of net evaporation-condensation through the corner capillary.…”

Section: Resultsmentioning

confidence: 99%

“…The advantage of the latter is their flexibility in terms of design and room for optimization. The selfoscillating fluidic heat engine (SOFHE) is a novel micro heat engine first introduced and studied by the same research group [4][5][6][7][8][9][10][11]. The SOFHE was proposed to power wireless sensors when coupled with an electromechanical transducer [4] as a TEH.…”

Section: Introductionmentioning

confidence: 99%

“…To overcome this problem, liquid must be introduced into the evaporator to form a thin film that feeds the phase change and facilitates the startup. Adding wicking structures such as capillary grooves [27,28], corners [25,26], and wicking fibers [10,11] are promising solutions. In a mesoscale version of the SOFHE, which is a tube with a millimeter-scale inner diameter, the mechanical power of the SOFHE showed a significant increase (thirtyfold) by boosting the phase-change rate in the presence of a wicking fiber [5].…”

Section: Introductionmentioning

confidence: 99%

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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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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…A fiber (capillary with closed ends, Polymicro, external diameter of 350µm) is inserted inside the tube into the hot zone to create a thin film that feeds the evaporation-condensation. The fiber acts as a wicking structure and pumps liquid from the liquid plug into the evaporator [14]. The temperature of the condenser is set at 20 C. As the heating process starts, a vapor bubble forms and grows lengthwise reaching an equilibrium point (normally in the adiabatic zone).…”

Section: B Experimental Proceduresmentioning

confidence: 99%

“…The oscillation starts when the force from the evaporation-condensation (change of mass of vapor) is greater than that of friction [12,13]. To increase the oscillation amplitude, the evaporationcondensation rate must increase and be synchronized with the displacement [14]. Theoretically, SOFHE's power is proportional to the square of amplitude and frequency.…”

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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Microfabricated Self-Oscillating Fluidic Heat Engine (SOFHE) With Enhanced Phase Change Through Corner Capillaries

Karami¹,

Tessier-Poirier²,

Nikkhah³

et al. 2022

2022 21st International Conference on Micro and Nanotechnology for Power Generation and Energy Conversion Applications (PowerME

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Time-Resolved Measurement of Enhanced Phase Change by a Fiber in an Oscillating Two-Phase Plug Flow

Cited by 4 publications

References 14 publications

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

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)

Microfabricated Self-Oscillating Fluidic Heat Engine (SOFHE) With Enhanced Phase Change Through Corner Capillaries

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