Application Cases

Experiment Name: Boiling Phase-Change Heat Transfer Experiment in Microchannels

Experiment Content: To investigate the influence of the electrowetting effect on boiling phase-change heat transfer in microchannels. Under different electrowetting parameters, the impact of the electrowetting effect on the gas-liquid interface behavior is analyzed, and the bubble size and gas-liquid interface behavior within the microchannel are visually observed. The influence of the AC electrowetting effect on bubble size, gas-liquid interface behavior, and wall temperature changes is clarified.

Research Direction: Boiling Phase-Change Heat Transfer in Microchannels

Testing Equipment: Signal generator, ATA-2081 high-voltage amplifier, high-speed camera, data acquisition device, etc.

Figure 1: Schematic diagram of the experimental setup

Experiment Process: Deionized water is used as the working fluid medium, which is pushed into the test microchannel by a syringe pump. After absorbing the wall heat provided by the DC power supply in the test section, the fluid changes from a single-phase liquid to a boiling phase-change fluid and then flows out of the microchannel exit into the fluid collector. The dielectric drive voltage is provided by the signal generator and output through the power amplifier (Aigtek, ATA-2081) (voltage: 0-360V, frequency: 0-2kHz). By using a PLC to supply power to the drive electrode array in sequence, the oscillation of the gas-liquid interface within the microchannel can be controlled.

Experiment Results:

Figure 2: Experimental Results

The PLC relay is designed to apply dielectric voltage every 5 seconds, then disconnect for 5 seconds, and this pattern is applied periodically. When a dielectric voltage of 50V is applied, in the first cycle, the wall temperature quickly drops from 102.8°C of the hydrophobic wall to 102.4°C of the hydrophilic wall; when the dielectric voltage is turned off, the wall temperature quickly rises back to 102.8°C. In the following cycles, it is observed that the wall temperature quickly decreases under the dielectric voltage and quickly rises again when the voltage is turned off. A similar phenomenon is observed when the dielectric voltage is 60V. The experimental results show that under the condition of flow boiling in microchannels, the AC voltage electrowetting effect has a cooling effect on the wall temperature, and the temperature response changes very quickly. The electrowetting effect causes the gas-liquid interface to oscillate periodically in the millisecond range. The oscillation of the gas-liquid interface periodically wets the dry area of the bubble, thereby reducing the wall temperature. It is found that the higher the drive voltage applied by the power amplifier, the more significant the reduction in wall temperature, but the frequency has no significant effect on the reduction of wall temperature.

Power Amplifier Recommendation: ATA-2081 High-Voltage Amplifier

Figure: Specifications of the ATA-2081 High-Voltage Amplifier