Flow condensation pressure oscillations at different orientations

O’Neill, Lucas E.; Mudawar, Issam; Hasan, Mohammad M.; Nahra, Henry K.; Balasubramaniam, R.; Mackey, Jeffery R.

doi:10.1016/j.ijheatmasstransfer.2018.07.072

Cited by 7 publications

(3 citation statements)

References 89 publications

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“…To the best of authors’ knowledge, only Torresin et al conducted flow condensation experiments on nanostructured superhydrophobic surfaces in a minichannel. They investigated the effect of surface subcooling for three different relatively low steam mass fluxes of 5, 10, and 15 kg/m 2 s. Even though their study focused on flow condensation heat transfer enhancement with superhydrophobic surfaces, the range of steam mass fluxes was considerably low compared to that of the studies about hydrophilic and hydrophobic surfaces. ,− Moreover, while visualization studies solely focused on the droplet cycle time, other important visual parameters related to droplet dynamics such as droplet number density, droplet departure diameter, and distribution of droplets on the condensing surface at different steam mass fluxes have not been discussed in detail.…”

Section: Introductionmentioning

confidence: 99%

Copper-Based Superhydrophobic Nanostructures for Heat Transfer in Flow Condensation

Chehrghani

Abbasiasl

Sadaghiani

et al. 2021

ACS Appl. Nano Mater.

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Superhydrophobic surfaces enhance the condensation heat transfer performance by facilitating removal of condensed droplets and coalescence-induced droplet jumping. During the last decade, studies on superhydrophobic surfaces have been mostly limited to working conditions, which are ideal for electron microscopy techniques. Therefore, the behavior of condensed droplets in the presence of a vapor flow with different vapor qualities and their implementation in flow condensation heat transfer enhancement have received rather little attention, which is the motivation behind this study. Thus, beside heat transfer analysis, we performed a visualization study on flow condensation in a minichannel and investigated droplet dynamics, including a histogram of droplet diameter distribution at different time intervals and stages of a condensation cycle consisting of nucleation growth and departure, droplet departure diameters, cycle time, and droplet number density. The droplet departure diameter decreases with steam mass flux, leading to a shift to smaller radii in droplet size distribution, which enhances condensation heat transfer. Enhancements up to 33% in the heat transfer coefficient were obtained at lower steam qualities for the tested superhydrophobic surface compared to the reference plain hydrophobic surface. We demonstrated that in addition to the high vapor shear stress exerted by the flow on the interface of the vapor and the condensed droplet, the advantage of an inherently unique water repellency feature of the nanostructured superhydrophobic surface can be utilized in flow condensation for enhancing condensation heat transfer.

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Section: Introductionmentioning

confidence: 99%

Copper-Based Superhydrophobic Nanostructures for Heat Transfer in Flow Condensation

Chehrghani

Abbasiasl

Sadaghiani

et al. 2021

ACS Appl. Nano Mater.

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“…The results from the developed predicting tools are in good agreement with the experimental results. O’Neill et al 22 Experimental Circular 7.12 mm ID channel FC-72 Horizontal, vertical upflow and downflow P sat = 130–160 kPa G = 50–350 kg m −2 s −1 Analysis of pressure oscillations during FWC Flow visualizations Vertical upflow exhibits 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 considered operating conditions. O’Neill et al 19 Experimental and analytical Circular 7.12 mm ID channel FC-72 Horizontal, vertical downflow and upflow P sat = 127–132.1 kPa G = 50.3–360.3 kg m −2 s −1 HTC measurements Assessment of available predicting correlations At low mass velocities vertical upflow exhibits the highest values of HTC while, as mass velocity is increased, results obtained for all three orientations begin to converge.…”

Section: Introductionmentioning

confidence: 99%

“…The precise knowledge of how changes in the gravity level affect the condenser operation is imperative for the accurate design of thermal management systems for space applications. Analysis of pressure signals in terrestrial condensing systems reveals the presence of oscillatory phenomena due to transient flow which can be encountered also in microgravity and hypergravity conditions and may impact the thermal performance of the cooling devices 22 . The stability and the performance of a vapor compression cycle working with R134a under varying gravity accelerations were experimentally investigated by Brendel et al 23 , 24 during parabolic flight campaigns.…”

Section: Introductionmentioning

confidence: 99%

Condensation heat transfer in microgravity conditions

et al. 2023

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In the present paper, a thorough review of the experimental and numerical studies dealing with filmwise and dropwise condensation under microgravity is reported, covering mechanisms both inside tubes and on plain or enhanced surfaces. The gravity effect on the condensation heat transfer is examined considering the results of studies conducted both in terrestrial environment and in the absence of gravity. From the literature, it can be inferred that the influence of gravity on the condensation heat transfer inside tubes can be limited by increasing the mass flux of the operating fluid and, at equal mass flux, by decreasing the channel diameter. There are flow conditions at which gravity does exert a negligible effect during in-tube condensation: predictive tools for identifying such conditions and for the evaluation of the condensation heat transfer coefficient are also discussed. With regard to dropwise condensation, if liquid removal depends on gravity, this prevents its application in low gravity space systems. Alternatively, droplets can be removed by the high vapor velocity or by passive techniques based on the use of condensing surfaces with wettability gradients or micrometric/nanometric structuration: these represent an interesting solution for exploiting the benefits of dropwise condensation in terms of heat transfer enhancement and equipment compactness in microgravitational environments. The experimental investigation of the condensation heat transfer for long durations in steady-state zero-gravity conditions, such as inside the International Space Station, may compensate the substantial lack of repeatable experimental data and allow the development of reliable design tools for space applications.

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