Two phase flow instability experiments were investigated in a forced circulation loop under low heating power and low pressure conditions. The observed instability was flashing induced and the oscillations took three main shapes, irregular intermittent oscillation, pure sinusoidal oscillation, and intermittent oscillation. The characteristics of the oscillating waves were analyzed based on the results of the mass flux, and fluid temperature. The effects of the pump bypass valve, the system pressure and the heating power on the oscillations amplitude, shape and frequency were investigated as well. It was found that the flashing is suppressed at high pressures and high powers, while intense oscillations occurred at low heat flux and low pressure.
Gli esperimenti di instabilità del flusso a due fasi sono stati studiati in un circuito a circolazione forzata in condizioni di bassa potenza di riscaldamento e bassa pressione. L'instabilità osservata è stata indotta da flash e le oscillazioni hanno assunto tre forme principali, oscillazione intermittente irregolare, oscillazione sinusoidale pura e oscillazione intermittente. Le caratteristiche delle onde oscillanti sono state analizzate sulla base dei risultati del flusso di massa e della temperatura del fluido. Sono stati inoltre studiati gli effetti della valvola di bypass della pompa, della pressione del sistema e della potenza di riscaldamento sull'ampiezza, la forma e la frequenza delle oscillazioni. Si è riscontrato che il flashing viene soppresso ad alte pressioni e alte potenze, mentre si verificano intense oscillazioni a basso flusso di calore e bassa pressione.
Investigation of flashing induced oscillations in vertical two-phase flows near saturation conditions
YASSIN, KARIM MOHAMMED ABDALWAGED
2022/2023
Abstract
Two phase flow instability experiments were investigated in a forced circulation loop under low heating power and low pressure conditions. The observed instability was flashing induced and the oscillations took three main shapes, irregular intermittent oscillation, pure sinusoidal oscillation, and intermittent oscillation. The characteristics of the oscillating waves were analyzed based on the results of the mass flux, and fluid temperature. The effects of the pump bypass valve, the system pressure and the heating power on the oscillations amplitude, shape and frequency were investigated as well. It was found that the flashing is suppressed at high pressures and high powers, while intense oscillations occurred at low heat flux and low pressure.File | Dimensione | Formato | |
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Investigation of flashing induced oscillations in vertical two-phase flows near saturation conditions (Executive Summary).pdf
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Investigation of flashing induced oscillations in vertical two-phase flows near saturation conditions.pdf
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https://hdl.handle.net/10589/212713