Flow Boiling Phenomenological Differences Between Micro- and Macroscale Channels

Tibiriçá, Cristiano; Ribatski, Gherhardt

doi:10.1080/01457632.2015.972726

Cited by 25 publications

(18 citation statements)

References 22 publications

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“…Thus, the uniform film thickness criterion proposed by Tibirica and Ribatski [23] matches the microchannel criterion of Cheng and Wu [16].…”

Section: Figure 3: Large Variation In the Convective Confinement Numbmentioning

confidence: 53%

“…In 2015, Tibirica and Ribatski [23], by combining a broad literature review with their own experiments using tubes with diameters from 1.00 to 2.32 mm, concluded that the key characteristics of microscale tubes are (1) the absence of stratified flows and (2) uniformity of the liquid film thickness along the tube perimeter for slug and annular flows in horizontal channels. Using an analytical model, they determined the maximum diameter for which a liquid slug could exist in a tube under static conditions was…”

Section: Figure 3: Large Variation In the Convective Confinement Numbmentioning

confidence: 99%

“…The fluid properties for water and R245fa were obtained from REFPROP Version 9.1 [24] (which calculates properties for water according to Wagner and Pruss [25] and R245fa according to Lemmon and Span [26]) and those for HFE7100 were obtained from Rausch et al [19]. The contact angles for water and R245fa are from [23] and for HFE7100 from [27]. It is assumed that the channels have circular cross sections, thereby providing identical values for the physical and hydraulic diameters.…”

Section: Summary Of Microchannel Definitionsmentioning

confidence: 99%

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Gravity effects in microgap flow boiling

Robinson

Bar‐Cohen

2017

2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

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Increasing integration density of electronic components has exacerbated the thermal management challenges facing electronic system developers. The high power, heat flux, and volumetric heat generation of emerging devices are driving the transition from remote cooling, which relies on conduction and spreading, to embedded cooling, which facilitates direct contact between the heat-generating device and coolant flow. Microgap coolers employ the forced flow of dielectric fluids undergoing phase change in a heated channel between devices. While two-phase microcoolers are used routinely in ground-based systems, the lack of acceptable models and correlations for microgravity operation has limited their use for spacecraft thermal management. Previous research has revealed that gravitational acceleration plays a diminishing role as the channel diameter shrinks, but there is considerable variation among the proposed gravity-insensitive channel dimensions and minimal research on rectangular ducts. Reliable criteria for achieving gravity-insensitive flow boiling performance would enable spaceflight systems to exploit this powerful thermal management technique and reduce development time and costs through reliance on ground-based testing. In the present effort, the authors have studied the effect of evaporator orientation on flow boiling performance of HFE7100 in a 218 μm tall by 13.0 mm wide microgap cooler. Similar heat transfer coefficients and critical heat flux were achieved across five evaporator orientations, indicating that the effect of gravity was negligible.

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“…Thus, the uniform film thickness criterion proposed by Tibirica and Ribatski [23] matches the microchannel criterion of Cheng and Wu [16].…”

Section: Figure 3: Large Variation In the Convective Confinement Numbmentioning

confidence: 53%

Section: Figure 3: Large Variation In the Convective Confinement Numbmentioning

confidence: 99%

Section: Summary Of Microchannel Definitionsmentioning

confidence: 99%

See 1 more Smart Citation

Gravity effects in microgap flow boiling

Robinson

Bar‐Cohen

2017

2017 16th IEEE Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems (ITherm)

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“…Figure 4 reveals a certain degree of nonuniformity of the liquid film along the tube perimeter. Recently, this aspect was taken into account to characterize micro-and macro-scale behaviors by Ong and Thome [22], Tibiriçá [31] and Tibiriça and Ribastki [32]. Based on flow pattern behaviors and on the degree of uniformity of the liquid film along the tube perimeter, Ong and Thome [22] developed a new macro-to-micro-scale threshold criterion; moreover, they included a transitional region between them.…”

Section: Subjective Characterizationmentioning

confidence: 99%

“…According to the Ong and Thome [22] criterion, the two-phase flow results obtained in the present study are within the mesoscale range. More recently, Tibiriçá [31] and Tibiriça and Ribastki [32] developed two macro-to micro-threshold criteria, based on the degree of uniformity of the film along the tube perimeter and the capillary height, considered as criterion for the occurrence of stratified flows. According to both criteria proposed by them, the results for a 2.32-mm ID tube are characterized as macroscale two-phase flows while for a 1.1-mm ID tube are microscale two-phase flows.…”

Section: Subjective Characterizationmentioning

confidence: 99%

Two-Phase Flow Characteristics During Convective Boiling of Halocarbon Refrigerants Inside Horizontal Small-Diameter Tubes

Sempértegui-Tapia

Alves

Ribatski

2013

Heat Transfer Engineering

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Two-phase flow observations were performed for The tests were run for mass velocities ranging from 100 to 600 kg/m 2 -s and saturation temperatures of 22, 31, and 41 • C. Additionally, an objective method to characterize two-phase flow patterns was developed. This method is based on simultaneous processing of signals from the following devices: a pair of diodes laser-sensors with a transparent tube between them within which the two-phase flow occurs, a micro-piezoelectric pressure transducer to determine the variation in the local pressure, and a microthermocouple within the fluid. The method was developed based on the k-means clustering algorithm, which consists of the gradual agglomeration of data of similar average characteristics. Simultaneous images of two-phase flow were obtained through a high-speed camera (10,000 frames/s) and used to identify the following flow patterns: bubbly, elongated bubbles, churn, and annular flows. The maps obtained by the objective method were compared against flow pattern results segregated based on flow visualization and a reasonable agreement was obtained between them. The vapor quality for the transition between churn and annular flow pattern decreases with decreasing the tube diameter, whereas the vapor quality for the transition between elongated bubbles and churn flow decreases with increasing tube diameter. Effects of saturation temperature and mass velocity were also verified. Additionally, elongated bubble velocities, frequencies, and lengths were determined based on the analysis of high-speed videos and the processing of signals of the diode/laser-sensor. The elongated bubble velocity was correlated as a linear function of the two-phase superficial velocity. A new image treatment method was developed to automatically identify the entrainment frequencies, which were segregated according to two groups: low and high frequency. The former group was characterized by frequencies lower than 20 Hz and the later by 50-500 Hz frequency ranges.

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