Two-phase Pressure Drop Correlations Research Articles

Thermal-Hydraulic Characterization of a Thermosyphon Cooling System for Highly Compact Edge Microdatacenter

Abstract In the European project BRAINE, an extremely efficient passive thermosyphon cooling system was developed for a novel type of Edge MicroDataCenter (EMDC) with high heat fluxes to dissipate on individual computer cards and high heat dissipation rate per unit volume in the dense array of these cards. The primary objective was the cooling of 11 nodes (which include CPUs, FGPAs, GPUs and storage) considering one heat sink evaporator per node. The present study shows the experimental results obtained with the new environmentally friendly refrigerants R1233zd(E) and R1234ze(E) as well as a validation of the solver used to design the thermosyphon for a first demo EMDC with 4 slots (i.e 4 nodes). The maximal total dissipated power was 950 W and performance ratios of heat dissipation-to-cooling fan power up to 98-to-1 were obtained. The solver validation was performed by comparing pressure drop of the different components as well as the maximum temperature of the heaters mimicking CPUs for 232 simulated datapoints and proved extremely good accuracy without any scaling or empirical factors: 99%, 78%, 53% and 95% of the datapoints for the evaporator, riser, condenser and total pressure drop, respectively, were within 30% of the experimental results, which is accuracy comparable to the best two-phase pressure drop correlations in the literature, so a very good validation result. For the temperature validation, 97% of the datapoints were within 5°C of the experimental measurements, highlighting the robustness of the solver.

Experimental study on flow boiling of HFE-7100 in rectangular parallel microchannel

With the rapid development of microelectronic technology, the integration and power of chip are increasing. Heat dissipation with high heat flux in limited space has become a bottleneck restricting the efficient and stable operation of the microelectronic devices. Flow boiling in microchannel heat sink is one of the most essential candidates for solving this problem. It has been shown that remarkable high heat transfer performance can be achieved through the liquid-to-vapor change process, which can dissipate a large amount of heat from a small area. In addition, dielectric fluorinated fluids, such as HFE-7100, HFE-7200, and FC-72, are especially suitable for cooling microelectronic devices, because of their excellent safety and environmental characteristics. However, dielectric fluorinated fluids have poorer thermophysical properties than water. Thus, the flow boiling heat transfer characteristics of dielectric fluorinated fluids can be different from those of water. In this work, flow boiling heat transfer and flow characteristics of HFE-7100 in a rectangular parallel microchannel are investigated. The tests are conducted at mass fluxes from 88.9 to 277.8 kg·m<sup>–2</sup>·s<sup>–1</sup>, inlet subcooling temperature from 20.5 to 35.5 ℃ and effective heat flux from 12 to 279 kW·m<sup>–2</sup> at nearly atmospheric pressure. The effects of mass flux, inlet subcooling temperature, effective heat flux and vapor quality are examined and analyzed. Additionally, flow visualization is also obtained to explain the heat transfer mechanism during the experiments. The results show that the boiling hysteresis is observed for HFE-7100 at low inlet subcooling temperature, and the increasing inlet subcooling temperature and mass flux can delay the onset of nucleate boiling. The increases of inlet subcooling temperature and mass flux can enhance the two-phase heat transfer coefficient. And the two-phase heat transfer coefficient is significantly dependent on the inlet subcooling temperature in the slug flow, while it is significantly dependent on the mass flux in the annular flow. The two-phase pressure drop increases drastically as the effective heat flux increases. And the two-phase pressure drops with different mass fluxes at constant vapor quality are obviously different between the slug flow and the annular flow. Furthermore, the experimental data are compared with four predicted values of the literature. It is found that the correlation of Lockhart has the best statistical agreement with an MAE of 19.6% and over 85% of points in the deviation bandwidth of ±30%. The results in this paper give valuable theoretical guidance for designing and optimizing heat dissipation equipment for microelectronic devices. By utilizing HFE-7100 as the coolant and microchannel heat sinks in flow boiling, it is possible to enhance the stability and reliability of the electronic devices. Additionally, the heat transfer performance associated with different heat fluxes can be improved by regulating the inlet subcooling and mass flow rate. Finally, the two-phase pressure drop correlation proposed by Lockhart can be employed to predict the pump power for heat dissipation equipment.

Experimental study on boiling two-phase of liquid sodium along a 7-rod bundle – Part Ⅰ: Pressure drop characteristics

The two-phase pressure drop characteristics of liquid sodium are very significant for the safety and serious incident program development analysis of sodium-cooled fast reactor (SFR). In this paper, the boiling two-phase pressure drop experiments of liquid sodium were conducted in a 7-rod bundle with the mass flux range of 80 ∼ 390 kg/(m2·s), heat flux up to 120 kW/m2 and the absolute pressure range of 7.5 ∼ 100 kPa. The experimental results show that the frictional multiplier of boiling two-phase liquid sodium in the rod bundle channel decreases with the increase ofXLM. Some existing two-phase pressure drop correlations in the literatures were assessed and compared with the experimental data obtained in the present study. Results showed that these correlations could not predict the current experiments well because of the different geometries and measurements of high temperature environment. The new correlation for the two-phase friction multiplier of liquid sodium was developed in the 7 rod bundle. The predicted value of the new correlation was within 30 % of the experimental data in the rod bundle, which sufficiently demonstrates that the new correlation developed in this paper can well predict the boiling two-phase frictional pressure drop of liquid sodium in the rod bundle.

A CFD-based surrogate model for predicting slurry pipe flow pressure drops

Slurry pipelines are extensively employed in most mining operations to transport raw materials and tailings. The aim of the paper is twofold: on the one hand, to develop a generalized slurry flow model using computational fluid dynamics (CFD) to develop a better insight into the complexity of slurry pipe flows, and on the other hand, to develop a surrogate model for pressure drop predictions, which can be used in operations simulation and monitoring tools. A two-fluid model based on the Eulerian-Eulerian approach along with the SST k-ω turbulence model was used. The motion of the solid phase was modeled by the kinetic theory of granular flow (KTGF) to account for both particle-particle and particle-wall interactions. The model was validated by comparison with experimental data available in literature. A new two-phase pressure drop correlation is proposed based on the numerical computations of horizontal pipes featuring 525 data points.

Experimental study and general correlation for frictional pressure drop of two-phase flow inside microfin tubes

The adiabatic pressure drop in a microfin tube with an outside diameter of 3.5 mm was experimentally studied herein. The experiments were conducted using R1234yf as a working fluid at saturation temperatures of 20 °C and 30 °C with varying mass velocities from 50 to 300 kg m−2s−1 and vapor qualities ranging from 0.1 to 0.9. The effects of experimental conditions were analyzed and discussed with present and previous data. A new two-phase flow frictional pressure drop correlation has been developed using the data with tube diameter of 2.5–9.52 mm, mass velocity of 50–1000 kg m−2s−1, and many kinds of refrigerants. The proposed correlation predicts the experimental data of other researchers with mean deviation of 17.6%.

Saturated flow boiling inside conventional and mini/micro channels: A new general model for frictional pressure drop using genetic programming

• A new general model for FPD during saturated boiling was proposed using GP. • 6021 experimental data samples from 42 published sources were analyzed. • Present model showed favor outcomes for different flow regimes and channel sizes. • The accuracy of previous models was considerably lower than the present one. • The new model presented favor physical trends at different operating conditions. This study presents a general explicit model for estimating the saturated flow boiling frictional pressure drop (FPD) in conventional (macro) and mini/micro channels heat exchangers. An extensive database including 6021 experimental data samples has been gathered from 42 published sources, covering a broad range of fluids, channel diameters and operating parameters. The new model is based on the separated model suggested by Lockhart and Martinelli (1949) for two-phase flow. Thus, the two-phase multiplier, ϕ l o 2 has been estimated using the intelligent approach of genetic programming (GP). The presented model predicts the mentioned database with a reasonable value of average absolute relative deviation (AARD) of 21.34%. Moreover, 74.85% of predicted data have an error of lower than 30% of the experimental values. The entire database is compared with ten well-known two-phase pressure drop correlations for the evaluation of previous models. But all of them showed a total AARD of more than 27%. The GP model shows good accuracy for both conventional and mini/micro channels and different flow regimes, including low and high Reynolds numbers. In addition, it is applicable for estimating the boiling FPD in different operating conditions. Based on 752 additional data from 4 independent sources, the new model provides the best predictions for estimating the FPD in conventional and mini/micro channels.

Two-phase pressure drop analysis of swirl tube in one-side high heat load condition for plasma facing component application

In this study, the two-phase pressure drop of a one-side heated swirl tube (twist ratio = 3, 5) was experimentally studied. If the a heat flux is gradually increased, the vapor blocks the flow path, thus leading to an increase in the differential pressure. As the inset sub-cooling and mass flow rate increase, the vapor is removed by condensation more rapidly, and thus, the rate of increase of differential pressure is reduced. From the evaluation of the prediction performance of the existing two-phase pressure drop correlations, it was found that the mean error rates of all correlations exceeded 50%. This is because most of the existing correlations were not developed based on the microchannel, but they were not focused on the swirl tube. Therefore, the authors developed a new two-phase pressure drop multiplier correlation for a one-side heated swirl tube that reflects the effect of the twist tape by modifying the Manglick single-phase swirl tube pressure drop correlation using the AI regression method.

Development of Empirical Correlation of Two-Phase Pressure Drop in Moisture Separator Based on Separated Flow Model

Pressure drop across the moisture separator installed in the steam generator of a nuclear power plant affects the power generation efficiency, and so accurate pressure drop prediction is important in generator design. In this study, an empirical correlation is proposed for predicting the two-phase pressure drop through a moisture separator. To ensure the applicability of the correlation, a series of two-phase air-water experiments were performed, and the results of the present test and of the benchmark test of high-pressure steam-water were used in developing the correlation. Based on the experimental results, quality, dimensionless superficial velocity, density ratio of the working fluid, and the geometrical factor were considered to be important parameters. The two-phase pressure drop multiplier was expressed in terms of these parameters. The empirical correlation was found to predict the experimental results within a reasonable range.

Experimental Investigation on Adiabatic Two-Phase Frictional Pressure Drop of R1234ze(E) and R134a in a Horizontal Minichannel

Abstract R1234ze(E) has been created as an environmentally friendly substitution of R134a. An experimental investigation on adiabatic two-phase frictional pressure drop inside a 1.88 mm horizontal minichannel with R1234ze(E) and R134a was conducted. The saturation pressure and mass flux ranged within 0.6–0.9 MPa and 450–900 kg/(m2 s). Based on the 299 measured data points, the influences of various factors, including saturation pressure, mass flux, and the like, are examined detailedly. Larger mass flux brings about larger frictional pressure drop, and vapor quality performs the same function, but saturation pressure works inversely. The frictional pressure drops between R1234ze(E) and R134a present no significant differences. The experimental data are compared against 23 predictive models, among which the one from Xu and Fang (2013, “A New Correlation of Two-Phase Frictional Pressure Drop for Condensing Flow in Pipes,” Nucl. Eng. Des., 263, pp. 87–96) gives the best accuracy. In addition, a database including 3150 experimental adiabatic two-phase frictional pressure drop data points is derived from the current study and 29 published literature. Based on the database, the 23 models are assessed, and the most effective one is from Müller-Steinhagen and Heck (1986, “A Simple Friction Pressure Drop Correlation for Two-Phase Flow in Pipes,” Chem. Eng. Process., 20(6), pp. 297–308). This work can provide guidance for choosing appropriate two-phase frictional pressure drop models under adiabatic conditions.

Effect of Ambient Temperature Variation on Pressure Drop During Condensation in Long Inclined Tubes

Abstract Two-phase flow pressure drop during condensation of steam inside inclined tube heat exchangers was investigated over a wide range of ambient temperature. The ambient temperature changes from 3 to 45 °C, the steam mass flux varies from 3 to 18 kg/(m2 · s), vapor quality ranges from 0.51 to 0.86. 608 data points were experimentally obtained and compared with eight commonly used correlations from the available literatures. Frictional pressure drop increases with increasing temperature difference and fan speed. For the full experimental dataset, the best overall performing correlation was obtained by using the Wallis correlation (MAPE = 17.60%, NRMSE = 14.87%). For cold ambient temperatures, (Tamb < 20 °C, N = 298), the best overall performing correlation was obtained by using the Carey correlation (MAPE = 11.02%, NRMSE = 14.71%). For hot ambient temperatures (Tamb > 30 °C, N = 196), the Lockhart and Martinelli correlation has shown the best performance (MAPE = 16.84%, NRMSE = 20.45%). An improved two-phase frictional pressure drop correlation based on the Wallis correlation (Wallis, 1969, One Dimensional Two-Phase Flow, McGraw-Hill, New York) is proposed.

On instantaneous pressure surges and time averaged pressure drop in intermittent regime of two-phase flow

Vigorous aeration and instantaneous pressure fluctuations associated with intermittent flow cause severe erosion-corrosion in the piping systems which lead to material degradation or wall thinning and leakages. Sometimes, this phenomenon results in catastrophic failures and hazards in transportation pipelines for industries such as petroleum, nuclear, geothermal and chemical. Present analysis is on the instantaneous pressure surges associated with the intermittent flow patterns and the two-phase frictional pressure drop. Experiments are carried out for three distinct sub-regimes of intermittent flow namely; Plug, Less Aerated Slug (LAS) and Highly Aerated Slug (HAS) flow. Instantaneous pressure fluctuation and time averaged pressure drop along the pipe length are reported for 350 combinations of inlet flow conditions (in term of ReSL and ReSG) of intermittent flow regime. Combined images of captured visual observations and measured instantaneous pressure fluctuations are demonstrated in terms of their influence on erosion and corrosion in detail. The obtained results are compared with the existing models for estimation of two-phase pressure drop proposed by earlier researchers. Large deviations between the experimental results and existing pressure models signify the need of separate correlation for two-phase frictional pressure drop for intermittent flow regime. In this direction, a unified correlation for prediction of two-phase frictional pressure drop for intermittent flow regime is proposed. The measured experimental results and obtained correlation for pressure drop will help in avoiding the erosion-corrosion in piping system. Also, database presented in this paper will aid to the effective and safe design of piping systems for petroleum, nuclear, geothermal and chemical industries.

Development of a new spacer grid pressure drop model in rod bundle for the post-dryout two-phase flow regime during reflood transients

Flow blockages such as the spacer grids play an important role in a two-phase flow system as they modify the flow and heat transfer behavior. Their existence, on the one hand, increase the turbulent mixing and heat transfer capability of fluid directly downstream; while on the other hand, create additional pressure loss within the system thus requiring a detailed and comprehensive understanding. In the present work, a new two-phase flow pressure drop correlation induced by spacer grids in the dispersed flow film boiling (DFFB) regime is developed based on the unique reflood experimental data obtained from the Nuclear Regulatory Commission/Pennsylvania State University rod bundle heat transfer test facility. The test conditions cover wide ranges of system parameters for two-phase flow system which can be used for model development. It is found that the most dominating system parameter is the mixture mass flow rate across the spacer grid location. As a result, the spacer grid loss coefficient is correlated with the mixture Reynolds number and a blockage geometry correction factor. The current correlation is found to significantly improve the prediction of the spacer grid pressure drop in the DFFB regime generally within a 25% error span, while the other exiting correlations failed to capture the two-phase flow hydraulic behavior involved during the reflood transients. The current correlation developed can be readily implemented into existing thermal-hydraulic analysis codes to further improve their prediction capabilities in the DFFB regime with the presence of flow blockages.

Development of a correlation for pressure drop of two-phase flow inside horizontal small diameter smooth and microfin tubes

Abstract This study investigated the pressure drop of adiabatic vapor-liquid two-phase flow inside horizontal smooth and microfin tubes with 2.5 mm outside diameter. R134a and R1234yf were used as working fluid and the experiments were carried out at saturation temperatures of 20 and 30°C, mass velocities ranging from 50 to 200 kg m−2s−1 and vapor qualities ranging from 0.1 to 0.9. The effects of mass velocity, vapor quality, refrigerant properties and tube diameter on the pressure drop were analyzed. Some typical previous pressure drop correlations were used to predict the experimental data. A new two-phase pressure drop correlation for small diameter tubes was proposed based on the experimental data. The new correlation agrees with the available other researchers’ data and it can be broadly applied to the small diameter smooth and microfin tubes, wide range of mass velocity and many kinds of refrigerants.

New Correlations for Two Phase Flow Pressure Drop in Homogeneous Flows Model

The calculation of pressure drop in pipes two-phase flow is essential in different areas. Even though several studies concerning this issue have been conducted, an accurate correlation is still required. The objective of the paper is to develop correlations for two-phase friction pressure drop and mixture viscosity. The new correlation can be used to compute the friction pressure drop for two phase flow in homogenous approach modeling. The original equation is generated from a similitude between the mixture viscosity for two-phase flows and the thermal conductivity of the porous structure. The new correlation is evaluated against 846 experimental data of friction pressure drop collected from literature on circular pipes; the experimental data including different working fluids such as R1234ze (E), R32, R-600a R717, R134a, R410A and carbon dioxide (CO2) at different hydraulic inner diameters and mass flux. Models are assessed based on the relative percentage error and the probability density function (PDF). The predictions by the new correlation and other correlations from the literature are compared based on some experimental data. It is found that new correlation has a mean absolute relative deviation (MARD) of 30%. It is proved that these new correlations of two-phase flow pressure drop can be used to predict the experiment measurements of pressure drop, on circular pipes, minichannels and microchannels.

On the Prediction of Pressure Fluctuations and Pressure Drop Caused by Confined Bubble Growth During Flow Boiling in a Rectangular Mini/Micro-Channel

Heat-sinks based on flow boiling in microchannels have the potential to mitigate temperature rise in high heat flux devices such as electronic equipment. One of the major challenges is the instability associated with pressure fluctuations caused due to the confined bubble growth during boiling in a microchannel. This paper presents a comprehensive model to estimate the dynamic pressure fluctuations in a channel of rectangular cross-section and compares with the experimental results. The time-averaged pressure drop obtained from the transient model has been verified with the experimental results and the steady two-phase flow pressure drop correlations. Effects of various parameters such as heat flux and mass flux on the time-averaged pressure drop and the transient pressure fluctuations are presented. The paper also provides an approximate methodology to estimate the nucleation frequency derived from the waiting period of the bubble. The calculated frequency is validated qualitatively with the experimental observation available in the literature. The current work also demonstrates that the transient pressure drop models, which, with suitable inputs, predict the local pressure fluctuations during confined bubble growth, can also be used to predict the steady- flow pressure drop.

Comparison of Two-Phase Flow Correlations for Thermo-Hydraulic Modeling of Direct Steam Generation in a Solar Parabolic Trough Collector System

Direct steam generation (DSG) in parabolic trough collector (PTC) is an efficient and feasible option for solar thermal power generation as well as for industrial process heat supply. The two-phase flow inside the absorber tube complicates the thermo-hydraulic modeling of the DSG process. In the present work, a thermo-hydraulic model is developed for the DSG process in the receiver of a solar PTC. The two-phase flow in the evaporating section is analyzed using two empirical correlations of heat transfer and pressure drop, and a flow map integrated heat transfer and pressure drop model. The results of the thermo-hydraulic simulation using different two-phase heat transfer and pressure drop correlations were compared with experimental data from the direct solar steam (DISS) test facility at Plataforma Solar de Almeria (PSA), Spain. The test facility has collectors with aperture width of 5.76 m, focal length of 1.71 m, and absorber tube with inner and outer diameters of 50 mm and 70 mm, respectively. The simulation results using the aforementioned two-phase models were found to be satisfactory and consistent within the experimental uncertainty. The flow map based heat transfer model predicted the mean fluid temperature with root-mean-square error (RMSE) of 0.45% and 1.40%, for the cases considered in the present study. Whereas the flow pattern map based pressure drop model predicts the variation of pressure along the length of the collector with RMSE of 0.5% and 0.14%. Moreover, the flow pattern map based model predicts the different flow regimes paving a better understanding of the two-phase flow and helps in identifying the critical sections along the collector length.

Effects of pipe size on horizontal two-phase flow: Flow regimes, pressure drop, two-phase flow parameters, and drift-flux analysis

This paper performs experimental studies to investigate the effects of pipe size on horizontal air–water two-phase flow in a wide range of flow configurations. Some of the major characteristic two-phase flow phenomena of interest include flow regime transitions, two-phase frictional pressure drop, local interfacial structures, and drift-flux analysis. Based on the experimental results obtained in two pipe sizes, the flow regime maps and the correlations for two-phase frictional pressure drop employed in conventional nuclear reactor system analysis codes (TRACE and RELAP) are evaluated. It is found that the flow regime maps in the codes incorrectly predict plug and slug flows as bubbly flow. Effects of pipe size on flow regime transitions are observed, while these effects are not reflected on the maps employed in the codes. The frictional pressure drop analysis suggests that the closure relations used in both TRACE and RELAP can be improved for horizontal two-phase flow. The local time-averaged two-phase flow parameters acquired by a four-sensor conductivity probe including void fraction, interfacial area concentration, bubble velocity, and bubble Sauter-mean diameter provide quantitative descriptions for the interfacial structures in different pipe sizes. It is found that increasing the pipe size tends to cause bubbles to be more concentrated near the top wall in bubbly flow. As a result, the bubble layer occupies a smaller portion of the flow area as pipe diameter increases. Based on the experimental database, drift-flux analysis using both the 〈〈vg〉〉 vs. 〈 j〉 and 〈α〉 vs. 〈β〉 methods is performed. The effect of pipe size on drift-flux analysis is found to be negligible. The global slip is found to be less than one, indicating that the gas phase moves slower than the liquid phase in horizontal bubbly flow. This analysis also provides a predictive method to estimate the void-weighted bubble velocity and void fraction, which can be predicted with an average percent difference of ±3.3% and ±3.1%, respectively.

Influences of tube pitches on heat transfer and pressure drop characteristics of two-phase propane flow boiling in shell side of LNG spiral wound heat exchanger

For clarifying the influences of tube pitches on heat transfer and pressure drop characteristics of two-phase flow in the shell side of LNG spiral wound heat exchanger, experiments are performed on test samples covering the longitude tube pitch of 2–6 mm and the radial tube pitch of 1–4 mm. Propane is used as the tested fluid. The operational conditions cover the vapor quality of 0.2–0.9, the mass flux of 40–80 kg (m2 s)−1, the heat flux of 4–10 kW m−2, the pressure of 0.25 MPa and the temperature of −19.4 °C. The uncertainties of tested heat transfer coefficients and pressure drops are within 14.4% and 4.0%, respectively. The results indicate that, as the longitude tube pitch increases, both the heat transfer coefficient and pressure drop decrease; while as the radial tube pitch increases, the heat transfer coefficient always decreases for the mass flux of 60 and 80 kg (m2 s)−1, but varies non-monotonously for the mass flux of 40 kg (m2 s)−1; and the pressure drop decreases maximally by 61% with the increasing radial tube pitch. Two-phase heat transfer and pressure drop correlations reflecting the influences of tube pitches are developed, and the deviations of the predicted heat transfer coefficients and pressure drops from the experimental data are within ± 20% and ± 25%, respectively.

An experimental study of flow boiling frictional pressure drop of R134a in a horizontal 1.002 mm tube under hypergravity

An experimental study with a horizontal 1.002 mm inner diameter mini-tube is conducted to investigate the two-phase frictional pressure drop of R134a flow boiling under hypergravity. Totally 1718 data points under the gravity from 1 to 3.16g were obtained, with mass fluxes of 400–1075 kg/m2 s, vapor qualities of 0.05–0.85, heat fluxes of 24.0 and 31.5 kW/m2, and saturation pressures of 0.6 and 0.7 MPa. The hypergravity conditions were achieved using a centrifugal acceleration machine. The results show that with increasing gravity the flow boiling frictional pressure drop increases at high vapor quality but decreases at low vapor quality, and the trend reversals take place roughly in the range of 0.07 < x < 0.45, depending on saturation pressure and mass flux. The comparison between the experimental data and the predictions of 28 correlations of two-phase frictional pressure drop is made, and the results show that the best correlation has a mean absolute deviation of 12.8% for the entire data, 10.6% for normal gravity, and 13.7% for hypergravity.

Characterization and pressure drop correlation for sprays under the effect of micro scale cavitation

In this study, spray formation and atomization, droplet evolutions, break-up, and corresponding cavitating flows at the outlet of a short micro-channel with an inner diameter of 152 μm were experimentally studied at different injection pressures with the use of a high speed visualization system. High speed visualization was performed at five different segments to cover a ∼27.5 mm distance beginning from the micro-channel outlet (Five segments, at distances of 0–5.5, 5.5–11, 11–16.5, 16.5–22 and 22–27.5 mm from the micro-channel outlet) to assess the spray formation mechanism. High speed visualization revealed that droplet evolution is initiated from the second segment at low upstream pressures (5–30 bars), whereas droplets are discretized from the liquid jet in the fourth and fifth segments at medium and high upstream pressures (40–100 bars). Bigger size droplets formed at the outlet up to an injection pressure of 30 bars, while cavitation effect of intensified cavitating flows became dominant beyond this injection pressure, leading to smaller droplet sizes and a more conical spray. Pressure drop was correlated together with Martinelli parameter for cavitating flows and a new correlation for two-phase pressure drop was developed. Moreover, in order to segment the discretized droplets at low upstream pressure (5–30 bars) from captured images and to perform an in-depth analysis on them, an active contour approach utilizing curve evolution and level set formulation was implemented. As shown by experimental results, droplets were successfully segmented at different low pressure levels. The droplet/bubble evolution can be exploited in biomedical and engineering applications, where destructive effects of bubbly cavitating flows are needed.