A modeling study on alleviating uneven defrosting for a vertical three-circuit outdoor coil in an air source heat pump unit during reverse cycle defrosting

Song, Mengjie; Liang, Xin; Deng, Shiming

doi:10.1016/j.apenergy.2015.10.026

Cited by 42 publications

(6 citation statements)

References 24 publications

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“…Furthermore, the defrosting cycle of the ASHP unit is approximately 120 min under the frosting condition, and the entire defrosting duration is approximately 10 min, as indicated by previous studies [6,17]. Therefore, the power consumptions of the RCD and ultrasonic array defrosting over 120 min were calculated as follows:…”

Section: Analysis Of Ultrasonic Array Defrosting Performancementioning

confidence: 98%

“…With an increase in the wave velocity, the advance time decreased. The advance time of each vibrator was calculated using Equation (6). Finally, with respect to the deflection of the focused beam, the distance between the focusing point and each vibrator was calculated, and the advance time was subsequently determined according to the distance.…”

Section: Numerical Analysis Of Ultrasonic Guided Wavesmentioning

confidence: 99%

“…In severe cases, this can lead to operational accidents or even financial ruin [3][4][5]. To ensure that an ASHP operates efficiently under frost conditions, periodic defrosting is necessary [6].…”

Section: Introductionmentioning

confidence: 99%

“…The defrosting power consumption of the ASHP unit under ultrasonic array excitation decreases from −3.27% to 0.12%, whereas the heat-supply enthalpy difference increases from 4.47% to 10.86%. Therefore, the percentage increment of the COP is between 7.16% and 11.12%, and the power consumption of the reverse-cycle defrosting is 3-12 times that of ultrasonic array defrosting.Energies 2019, 12, 3117 2 of 18 defrosting [12,13], (4) fin surface treatment [14,15], and (5) reverse-cycle defrosting (RCD) [6,16,17]. Although these defrosting methods effectively delay or remove the frost accumulated on the surface of outdoor coils, they exhibit limitations and problems.…”

mentioning

confidence: 99%

“…Energies 2019, 12, 3117 2 of 18 defrosting [12,13], (4) fin surface treatment [14,15], and (5) reverse-cycle defrosting (RCD) [6,16,17]. Although these defrosting methods effectively delay or remove the frost accumulated on the surface of outdoor coils, they exhibit limitations and problems.…”

mentioning

confidence: 99%

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Ultrasonic Guided Wave Phased Array Focusing Technology and Its Application to Defrosting Performance Improvement of Air-Source Heat Pumps

Tan

Zhang

et al. 2019

Energies

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Previous studies have indicated that a basic frost layer negatively affects the heat-transfer efficiency and is difficult to remove using a single ultrasonic transducer. Herein, an ultrasonic phased array technology is proposed for evaporator coil defrosting. First, the dispersion curve of the guided wave in the vibration transfer plate and frosting fin is calculated, and the advance time of each ultrasonic vibrator and the ultrasonic near-field pressures under different velocities are determined through numerical calculations using the MATLAB software. Next, according to the advance time, ultrasonic array focusing is performed to remove the basic frost layer. Finally, the power consumption, heat-supply enthalpy difference, and coefficient of performance (COP) of the air-source heat pump (ASHP) unit are analysed. The theoretical analysis, numerical calculations, and experimental results consistently revealed that ultrasonic array focusing compensates for the energy dissipation and expends the effective defrosting area. Additionally, the perpendicular stress elicited by the Lamb wave and the differential transverse shear stress generated by the SH wave exceed the tensile strength and adhesion stress of the basic frost layer. The basic frost layer cracks and falls away, owing to the combination of the ultrasonic stress effect and the cavitation effect. The defrosting power consumption of the ASHP unit under ultrasonic array excitation decreases from −3.27% to 0.12%, whereas the heat-supply enthalpy difference increases from 4.47% to 10.86%. Therefore, the percentage increment of the COP is between 7.16% and 11.12%, and the power consumption of the reverse-cycle defrosting is 3–12 times that of ultrasonic array defrosting.

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Section: Analysis Of Ultrasonic Array Defrosting Performancementioning

confidence: 98%

Section: Numerical Analysis Of Ultrasonic Guided Wavesmentioning

confidence: 99%