Mechanistic model to predict frequency and amplitude of Density Wave Oscillations in vertical upflow boiling

O’Neill, Lucas E.; Mudawar, Issam

doi:10.1016/j.ijheatmasstransfer.2018.02.078

Cited by 23 publications

(8 citation statements)

References 92 publications

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“…Great care was taken in isolating physical, dynamic behavior due to DWOs from mechanically-induced oscillatory behavior through careful analysis of transient pressure signals and corresponding fast Fourier transforms, and conclusions from these works provided a starting point from which the present analysis was begun. It should also be noted that this work is the companion study to another [88] presenting a new analytic model for predicting frequency and amplitude of DWOs in vertical upflow boiling.…”

Section: )mentioning

confidence: 99%

Experimental investigation of frequency and amplitude of density wave oscillations in vertical upflow boiling

O’Neill

Mudawar

Hasan

et al. 2018

International Journal of Heat and Mass Transfer

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Historically, study of two-phase flow instabilities has been arguably one of the most challenging endeavors in heat transfer literature due to the wide range of instabilities systems can manifest depending on differences in operating conditions and flow geometry. This study utilizes experimental results for vertical upflow boiling of FC-72 in a rectangular channel with finite inlet quality to investigate Density Wave Oscillations (DWOs) and assess their potential impact on design of two-phase systems for future space missions. High-speed flow visualization image sequences are presented and used to directly relate the cyclical passage of High and Low Density Fronts (HDFs and LDFs) to dominant low-frequency oscillations present in transient pressure signals commonly attributed to DWOs. A methodology is presented to determine frequency and amplitude of DWO induced pressure oscillations, which are then plotted for a wide range of relevant operating conditions. Mass velocity (flow inertia) is seen to be the dominant parameter influencing frequency and amplitude of DWOs. Amplitude of pressure oscillations is at most 7% of the time-averaged pressure level for current operating conditions, meaning there is little risk to space missions. Reconstruction of experimental pressure signals using a waveform defined by frequency and amplitude of DWO induced pressure fluctuations is seen to have only moderate agreement with the original signal due to the oversimplifications of treating DWO induced fluctuations as perfectly sinusoidal in nature, assuming they occur at a constant frequency value, and neglecting other transient flow features. This approach is nonetheless determined to have potential value for use as a boundary condition to introduce DWOs in two-phase flow simulations should a model be capable of accurately predicting frequency and amplitude of oscillation.

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Section: )mentioning

confidence: 99%

Experimental investigation of frequency and amplitude of density wave oscillations in vertical upflow boiling

O’Neill

Mudawar

Hasan

et al. 2018

International Journal of Heat and Mass Transfer

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“…Vertical upflow once again exhibits the most dynamic (meaning large frequencies and amplitudes of oscillation) behavior, but the lack of trends for each plot indicates factors governing frequency of oscillation are independent from those determining amplitude. This is an important conclusion, as it indicates fundamentally different instability mode from that recently analyzed for flow boiling [81][82][83][84].…”

Section: Impact Of Oscillatory Modesmentioning

confidence: 43%

“…The present study deals with the condensation portion of FBCE and aims to augment prior work dealing with computational pre-diction of flow condensation [75,76], experimental and analytic assessment of the impact of body force on flow condensation heat transfer coefficient [77,78], and correlation of pressure drop and heat transfer for condensing flows using a large database from available literature [79,80]. This work also serves as a companion piece to a series of recent studies by the present authors investigating transient behavior and instabilities in flow boiling through a single rectangular mini-channel [81][82][83][84].…”

Section: Objectives Of Studymentioning

confidence: 97%

Flow condensation pressure oscillations at different orientations

O’Neill

Mudawar

Hasan

et al. 2018

International Journal of Heat and Mass Transfer

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Investigation of two-phase flow dynamic behavior and instabilities has traditionally centered on phenomena present in boiling flows due to the safety critical nature of boiling in a variety of cooling applications. Analysis of pressure signals in condensing systems reveal the presence of relevant oscillatory phenomena during flow condensation as well, which may impact performance in applications concerned with precise system control. Towards this end, the present study presents results for oscillatory behavior observed in pressure measurements during flow condensation of FC-72 in a smooth circular tube in vertical upflow, vertical downflow, and horizontal flow orientations. Dynamic behavior observed within the test section is determined to be independent of other components within the flow loop, allowing it to be isolated and interpreted as resulting from physical aspects of two-phase flow with condensation. The presence of a peak oscillatory mode (one of significantly larger amplitude than any others present) is seen for 72% of vertical upflow test cases, 61% of vertical downflow, and 54% of horizontal flow. Relative intensities of this peak oscillatory mode are evaluated through calculation of Q Factor for the corresponding frequency response peak. Frequency and amplitude of peak oscillatory modes are also evaluated. Overall, vertical upflow is seen to exhibit the most significant oscillatory behavior, although in its maximum case amplitude is only seen to be 7.9% of time-averaged module inlet pressure, indicating there is little safety risk posed by oscillations under current operating conditions. Flow visualization image sequences for each orientation are also presented and used to draw parallels between physical characteristics of condensate film behavior under different operating conditions and trends in oscillatory behavior detected in pressure signals.

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“…Around the PB region, the highly nonlinear coupling between pressure, temperature and density (thermodynamic nonlinearity) has been proposed by Herring & Heister (2006) as the reason for undesired effects such as thermoacoustic instabilities in high-pressure combustion chambers (Casiano, Hulka & Yang 2010;Poinsot & Veynante 2011) or bulk-mode oscillations in pressurized fuel heat exchangers (Hines & Wolf 1962;Faith, Ackerman & Henderson 1971;Linne et al 1997;Hitch & Karpuk 1998;Herring 2007;Palumbo 2009;Hunt & Heister 2014;Wang et al 2015;Hunt 2016), often leading to catastrophic hardware failure. These phenomena are similar to the multiphase instabilities called density wave oscillations (O'Neill & Mudawar 2018). The regions of the phase space considered in the literature are shown in figure 1.…”

Section: Introductionmentioning

confidence: 60%