Single-phase Vapor Research Articles

Comparisons of two-phase condensation and single-phase heat transfer and frictional pressure drop characteristics and energy-saving performance analysis of R-32 and R-410A in plate heat exchanger

In this study, the heat transfer and frictional pressure drop characteristics of R-32 and R-410A in a plate heat exchanger are experimentally evaluated. The study comprises two-phase condensation, single-phase vapor, and liquid cooling experiments of R-32 and R-410A, as well as an independent single-phase water heat transfer experiment. The effects of heat flux, mass flux, condensing pressure, mean vapor quality, and refrigerant Reynolds number on heat transfer and pressure drop are assessed for comparisons of R32 and R410A. The results demonstrate that the heat transfer performance and frictional pressure drop increase with rising mass flux and mean vapor quality and decrease with declining condensing pressure in the two-phase condensation experiments. Furthermore, increasing the heat flux enhances the heat transfer performance while having negligible impact on the frictional pressure drop. In the single-phase cooling experiments, both heat transfer performance and frictional pressure drop rise with increasing refrigerant flow rate. Based on the experimental results, Nusselt number and friction factor correlations for two- and single-phase flows of R-32 and R-410A are developed and compared with the correlations from other studies. Finally, energy-saving performance is evaluated and compared between the refrigerants.

Geology and ore fluids geochemistry of the Hamzeh–Gharanin orogenic gold deposit, NW Iran

The Hamzeh–Gharanin gold deposit (HGD) is located in the Qolqoleh–Kasnazan shear zone in the northwest of Sanandaj–Sirjan Zone (SSZ) and 40 km SW of Saqez. The main rock units are an assemblage of the Precambrian metasedimentary (pelitic) rocks and the Cretaceous phyllite associated with marble interlayers. The post–Cretaceous intrusive granitoids with NW–SE trends intruded within these two units. Mineralization occurs mainly within the NE–SW extensional veines and veinlets in proto–mylonitic, mylonitic and ultra–mylonitic rocks. Hydrothermal alterations consist of sericitization, carbonatization, silicification and chloritization. The main ore minerals include pyrite, chalcopyrite, arsenopyrite, pyrrhotite, sphalerite, galena, gold, magnetite and hematite. The fluid inclusions study from quartz minerals associated with the mineralization shows four different phases: single vapor phase (V; type I), single liquid phase (L; type II), liquid–vapor biphasic (LV; type III) and three phases (LLV; type IV). Microthermometric studies were performed on types III and IV of fluid inclusions. Homogenization temperatures (Th) for Types III and IV inclusions vary between 138 and 310 °C (mean 230 °C) and 250–335 °C (mean 300 °C) and their salinity varies between 0.52 and 13.87 and 4.79 to 9.58 (wt% NaCl), respectively. Moreover, the density of Types III and IV inclusions vary from 0.71 to 0.927 g/cm3 and 0.700–0.870 g/cm3, respectively. The oxygen (in quartz: 4.58–7.80 ‰; mean 5.82 ‰) and δ34S (in pyrite: 5.54–6.28 ‰; mean 5.91‰) isotope compositions of the mineralizing fluids indicate an insignificant meteoric water input during hydrothermal evolution and a magmatic origin of sulfur in the deposit which is broadly similar to those of orogenic gold deposits worldwide.

On the continuous nature of phase change in near-critical carbon dioxide

Unique boiling behavior at near-critical conditions can leverage the large heat transfer coefficients associated with flow boiling while mitigating some of the disadvantages encountered in two-phase flows, presenting opportunities for enhancing the stability and effectiveness of cooling systems. Contemporary understanding treats subcritical boiling and supercritical heat transfer as two distinct regimes, separated by the critical point. Recent studies investigating microchannel flow boiling near the critical point challenge this notion, suggesting a significant alteration in subcritical phase change heat transfer mechanisms, predominantly driven by variations in thermophysical properties near the critical point. However, a generalized understanding of heat transfer behavior and the phase change physics near the critical point is lacking. The current work presents a new perspective to elucidate underlying fluid phenomena associated with near-critical (0.85<PR<1.02) microscale (Dh=500μm) phase change over parameterized experimental conditions (G=100−1000kgm−2s−1; q″=2−100Wcm−2). Through high-speed (8000fps) side-view microscopic imaging and simultaneous heat transfer measurements, unique flow behavior was discovered at PR>0.95, including supercritical-like phenomena and evidence of homogeneous nucleation which form the physical basis for altered heat transfer behavior. The visualized flow physics and heat transfer behavior suggest a continuous transition from subcritical phase change to supercritical mechanisms near the critical point. As homogeneous nucleation becomes the dominant phase change mechanism, the near-wall heat transfer condition transitions from nucleate boiling to single-phase vapor convection. However, due to significant thermophysical property variations near the critical point, this single-phase convection condition exhibits fluid physics and heat transfer behavior virtually indistinguishable from supercritical conditions. These insights significantly disrupt the conventional understanding of a sharp transition in fluid behavior at the critical point. The gradual change in flow boiling mechanisms near the critical point presents opportunities for application-specific tuning of heat transfer performance through pressure variation alone.

Influence of gas density on void fraction and pressure drop in upward vapor–liquid flow

The influence of gas density on the void fraction, flow map, and pressure drop was examined for an upward vapor–liquid flow. The knowledge of the flow map is necessary to ensure a safe operational condition in a nuclear zone at high pressure. Moreover, the pressure gradient and its volumetric flow rate are related to the profitability of petroleum wells. Considering these scenarios, a modified cascade refrigeration cycle was constructed to generate and measure single-phase streams with different liquid and vapor density ratios. These single-phase liquid and vapor streams were mixed and injected into an upward vertical test section with an inner diameter of 26.64 mm and length of 5.8 m. The pressure ranged from 1.7 to 2.3 MPa, liquid–vapor density ratio ranged from 10.2 to 15.2, and total mass flux ranged from 733.1 to 882.9 kg.s−1.m−2. The void fraction, pressure gradient, and frictional pressure component were measured using quick-closing valves, temperature probes, and absolute and differential pressure sensors. The experimental data and transition line behavior of the flow map at high pressures in an upward two-phase flow as well as the proposed correction factors for the pressure gradient and its frictional component reflect the novelty of this study. Most existing studies have focused only on the influence of the gas density on the horizontal flow. A key observation of our study is that the liquid–vapor density ratio significantly changes the churn and annular transition lines. According to a vertical flow map found in the literature, the disappearance of the churn region can be foreseen and an annular transition occurs at lower gas velocities. The liquid–vapor density ratio does not influence the void fraction or slip velocity ratio; both increase with the superficial vapor velocity. Correction factors for the pressure gradient and its frictional component were proposed. The mean deviation for the pressure gradient was reduced from 27 % to 16 % after application of the correction factor. Half of the experimental points presented absolute relative errors lower than 30 % for the frictional pressure gradient. A cross-validation between the experimental data reported by other authors and the proposed correction factors was conducted to assess their response. In this cross-validation, 126 additional experimental points were used for the pressure gradient whereas 1270 points were used for its frictional component. Overall, the mean deviation of the pressure gradient was reduced from 92.7 % to 31.9 % after the application of the correction factor. Similarly, the mean deviation of the frictional gradient was reduced from 70.7 % to 31.3 % after the application of the correction factor. There was no evident influence of the liquid–vapor density ratio on the total pressure gradient and drift relationships for Froude numbers spanning from 2.6 to 7.4.

Vapor and Liquid (p-ρ-T-x) Measurements of Binary Refrigerant Blends Containing R-134a, R-1234yf, and R-1234ze(E).

The pressure-density-temperature-composition (p-ρ-T-x) data of binary refrigerant mixtures containing R-134a (1,1,1,2-tetrafluoroethane), R-1234yf (2,3,3,3-tetrafluoropropene), and R-1234ze(E) (trans-1,3,3,3-tetrafluoropropene) were measured in both the vapor and liquid phases using a two-sinker, magnetic-suspension densimeter. The specific samples in this study comprised two compositions of approximately (0.3/0.7) and (0.7/0.3) mole fraction for each of the following three binary refrigerant blends: R-1234yf + R-134a, R-134a + R-1234ze(E), and R-1234yf + R-1234ze(E). Single-phase vapor densities were measured over a temperature range of (253 to 293) K and pressures from approximately (0.04 to 0.5) MPa. Single-phase liquid and supercritical densities were measured over a temperature range of (230 to 400) K and pressures up to 21 MPa; for refrigerant blends containing R-1234yf, the maximum pressure was limited to approximately 12 MPa. Overall relative combined, expanded (k = 2) uncertainties in density ranged from 0.043% to 0.418%, with an average uncertainty of approximately 0.06%. Here, we present measurement results, along with comparisons to available literature data and to default equations of state and mixture models included in REFPROP.

Vapor and Liquid (p-ρ-T-x) Measurements of Binary Refrigerant Blends Containing R-32, R-152a, R-227ea, R-1234yf, and R-1234ze(E).

The pressure-density-temperature-composition ( ) data of binary refrigerant mixtures containing R-32 (difluoromethane), R-152a (1,1-difluoroethane), R-227ea (1,1,1,2,3,3,3-heptafluoropropane), R-1234yf (2,3,3,3-tetrafluoropropene), and R-1234ze(E) (trans-1,3,3,3-tetrafluoropropene) were measured in both the vapor and liquid phases using a two-sinker, magnetic-suspension densimeter. The specific samples in this study comprised two compositions of approximately (0.3/0.7) and (0.7/0.3) mole fraction for each of the following four binary refrigerant blends: R-32 + R-1234yf, R-32 + R-1234ze(E), R-1234yf + R-152a, and R-1234ze(E) + R-227ea. Single-phase vapor densities were measured over a temperature range of approximately (253 to 293) K and pressures from (0.05 to 0.98) MPa. Single-phase liquid and supercritical densities were measured over a temperature range of approximately (230 to 400) K and pressures up to 22 MPa; for refrigerant blends containing R-1234yf the maximum pressure was limited to 14 MPa. Overall relative combined, expanded (k = 2) uncertainties in density ranged from 0.025% to 0.191%, with an average uncertainty of approximately 0.05%. Here, we present measurement results, along with comparisons to available literature data and to default equations of state and mixture models included in REFPROP.

DESIGN OF HELICAL TYPE STEAM GENERATOR FOR EXPERIMENTAL POWER REACTOR

Reaktor Daya Eksperimental (RDE) is a high-temperature gas-cooled reactor (HTGR) for electricity generation, heat generation, and hydrogen production by Batan. Empirical and numerical calculations are needed to strengthen the existing design. The numerical method by computational fluid dynamic (CFD) analyzes temperature distribution and pressure drop along the pipe. The Batan RDE steam generator design has a seven-layer helical pipe model, while this research uses a one-layer helix pipe. In empirical calculations, the heat transfer region has three sections; single-phase liquid, two-phase, and single-phase vapor heat transfer. In numerical calculations, apply the assumption of constant heat flux and constant working fluid properties. The results of empiric calculations data showed that the helical pipe height was 3.98 m, shorter than the Batan design, which is 4.97 m. This considerable difference due to empirical calculations did not cover the safety factor. The results of numerical calculations show that in the single-phase, empiric calculation data were acceptable since the different values of numerical calculations for empiric calculations data were below 10%. Meanwhile, the case of the two-phase numerical calculations is not satisfactory and needs further research to obtain optimal results.

Life Span of Slippery Lubricant Infused Surfaces.

Since their discovery a decade ago, slippery liquid infused porous surfaces (SLIPSs) or lubricant infused surfaces (LISs) have been demonstrated time and again to have immense potential for a plethora of applications. Of these, one of the most promising is enhancing the energy efficiency of both thermoelectric and organic Rankine cycle power generation via enhanced vapor condensation. However, utilization of SLIPSs in the energy sector remains limited due to the poor understanding of their life span. Here, we use controlled conditions to conduct multimonth steam and ethanol condensation tests on ultrascalable nanostructured copper oxide structured surfaces impregnated with mineral and fluorinated lubricants having differing viscosities (9.7 mPa·s < μ < 5216 mPa·s) and chemical structures. Our study demonstrates that SLIPSs lose their hydrophobicity during steam condensation after 1 month due to condensate cloaking. However, these same SLIPSs maintain nonwetting after 5 months of ethanol condensation due to the absence of cloaking. Surfaces impregnated with higher viscosity oil (5216 mPa·s) increase the life span to more than 8 months of continuous ethanol condensation. Vapor shear tests revealed that SLIPSs do not undergo oil depletion during exposure to 10 m/s gas flows, critical to condenser implementation where single-phase superheated vapor impingement is prevalent. Furthermore, higher viscosity SLIPSs are shown to maintain good stability after exposure to 200 °C air. A subset of the durable SLIPSs did not show change in slipperiness after submerging in stagnant water and ethanol for up to 2 weeks, critical to condenser implementation where single-phase condensate immersion is prevalent. Our work not only demonstrates design methods and longevity statistics for slippery nanoengineered surfaces undergoing long-term dropwise condensation of steam and ethanol but also develops the fundamental design guidelines for creating durable slippery liquid infused surfaces.

Consolidated theoretical/empirical predictive method for subcooled flow boiling in annuli with reference to thermal management of ultra-fast electric vehicle charging cables

Ability to deliver very high electrical current through a charging cable is key to successful proliferation of electric vehicles (EVs). Associated with high current delivery is a host of thermal problems stemming from the need to remove enormous amounts of heat from the cable. This study seeks to develop a highly effective thermal management scheme based on subcooled flow boiling principles. The main objective is to develop a consolidated theoretical/empirical method for predicting the heat transfer and pressure drop characteristics of both laminar and turbulent flows though concentric circular annuli with uniformly heated inner wall and adiabatic outer wall. Although maintaining subcooled boiling along the entire cable is a key practical objective, this consolidated method is shown to be capable of tackling multiple flow regimes (single-phase liquid, subcooling boiling, saturated boiling, and single-phase vapor) and highly effective at predicting local surface and fluid temperatures. This method is then adopted to design and optimization of very high current EV charging cable cooling system using dielectric fluid HFE-7100 as coolant. Effects of various parameters, including electrical current, both wire and conduit sizes, inlet fluid temperature, and flow rate are carefully addressed and recommendations made for effective and robust overall system design.

Development of a two-fluid model for predicting phase-changing flows inside thermal vapor compressors used in thermal desalination systems

The aim of this study is to investigate the performance of “thermal vapor compressors (TVCs)” as one of the main components of “multi-effect distillation (MED)” systems. A single-phase vapor flow is normally required for continuous operating of a TVC, though a mixed liquid-vapor steam flow is often formed in TVCs due to a steam condensation in the supersonic flow through nozzles. A two-phase flow in a TVC undesirably reduces its performance, and lowers fresh water production rates of a desalination system. More accurate prediction of the “entrainment ratio” as a main performance parameter of a TVC completely influences on the gain output ratio (GOR) of a desalination system. For this purpose, a mathematical model was developed with respect to the phase-changing flow, and the model was later validated with experimental data. An iterative multiphase flow methodology based on a non-equilibrium condensation theory was developed to explore the difference between “single-fluid” and “two-fluid” models. Interactions between the liquid and the vapor phases were thoroughly evaluated through comparing variations in nucleation rates, droplets radii, number of droplets, and so on. The advantage of this method over other numerical methods is that this method is capable of considering different velocities for the liquid and the vapor streams based on the Eulerian-Eulerian approach, where formation and collapse of droplets can be precisely predicted. Results revealed that the performance of a TVC can better be predicted in a two-fluid model when compared with a single-fluid model.

Heat transfer characteristics of liquid hydrogen flowing inside of a vertical heated pipe under quasi-stationary heat input

Heat transfer from inner surface of a vertical heated pipe to subcooled or saturated liquid hydrogen flowing upward was measured for quasi-steadily increasing heat input up to fully developed film boiling regime and decreasing the heat input through the film boiling regime. The experiments were carried out at the inlet pressures of 400, 700 and 1100 kPa and subcoolings from 0 K to 11 K. Three test pipe heaters made of SS310S with inner diameters of 6 and 8 mm and lengths of 100 and 200 mm were used. Experimental data from non-boiling to developed film boiling and developed film boiling down to minimum film boiling was obtained with the record of mass flow rate by continuously increasing and decreasing the heat input. It was observed that though the mass flow rate decreases with the increase of the heat generation rate, the heat transfer coefficient increases. Discussions on heat and mass transfer in inverted annular flow, dispersed droplet flow, single-phase vapor flow regimes and their changing conditions from one by one were carried out to clarify the phenomena. A calculation code of heat transfer characteristics was developed based on the discussions. The calculated results are in good agreement with the experimental results.

Effect of Wall Temperature Profile Inputs on Thermal Hydraulic Characteristics in Long Vertical Steam Generator Tube

Flow boiling phenomenon in long vertical tubes at high pressure is of great importance in nuclear and thermal power plants. These tubes are associated with several complexities such as flow instabilities, flow-induced vibrations, pressure drop, dry out etc. which may lead to tube fatigue/damage (responsible for severe plant accident and safety issues). Therefore, precise modeling of complete flow boiling phenomenon (single phase liquid to single phase vapor including two-phase flow boiling region) is necessary to design boiler tube and to avoid complexities. Most of the work carried out in literature mostly deals with modeling of particular heat transfer region of the tube. The present work, effect of wall temperature profile inputs on the thermal hydraulic characteristics and pressure drop in 23 m long steam generator (SG) tube at 172 bar pressure has been studied. Wall temperature profile (TP) is given as input by two different ways. The TP-1 is obtained from DESOPT one-dimensional computer code. Linearly increasing TP-2 is given based on shell side bulk fluid temperatures. In our recent article, a new methodology for modeling of complete flow boiling of long vertical tube has been developed, the vertical tube is divided into four sections based on flow patterns (which are decided in terms of vapor fraction value) to model the complete flow boiling process. Simulations were carried out at 20 % and 60 % designed heat duties. The heat transfer coefficient and vapor fraction results with TP-1 shows shift in the peak in positive direction as that of TP-2. Also, TP-2 shows extra small peak in axial heat flux and heat transfer coefficient distribution profile. The magnitude of predicted pressure drop for both the temperature profiles is comparable. Overall, axial distribution profiles of thermal hydraulics parameters such as vapor fraction, heat transfer coefficient etc. showed almost same trend for both the temperature profile inputs.

Snapshot of a magmatic/hydrothermal system from electrical resistivity tomography and fumarolic composition, Whakaari/White Island, New Zealand

Combined interpretation of Electrical Resistivity Tomography (ERT) data, with plume and fumarolic gas emissions provides a snapshot of the Whakaari/White Island hydrothermal system 11 months prior to an eruption on December 9, 2019. Two and three dimensional inversion of the ERT data images the F0 fumarole as a low resistivity (2–5 Ωm) feature reflecting the two-phase zone surrounding the single phase vapour conduit. Crucially, interpretation of the inversion images is well constrained by a large existing dataset of rock electrical properties, including surface conductivity, porosity and intrinsic formation factor, alongside new measurements of liquid phase electrical conductivity taken from a range of hot-springs on the island. Pore-filling liquids are an order of magnitude more conductive than sea-water with their low to very low pH (3.4 to −0.3) contributing to their extremely conductive nature. An extensive low-resistivity feature (0.2 Ωm) at ~125 m depth is therefore interpreted as a liquid saturated layer exposed to hydrothermal alteration by acid fluids. The intersection of the F0 fumarole trace with this layer is coincident with a previously determined source of deformation, suggesting that heat transport inside the fumarole conduit pressurises surrounding liquid and vapour filled pore space, generating the deformation signal. The timeseries of fumarolic and plume emissions in the year prior to the ERT survey show that the gases transported by the fumarole are a mixture of high temperature magmatic vapour and lower temperature gas equilibrated within the hydrothermal environment. Interpretation of the gas data suggests that the snapshot captured by the ERT image shows the single-phase vapour and two-phase vapour-liquid regions adjacent to the conduit were likely at close to their smallest extent, consisting of mostly hydrothermal derived gases.

Geology, geochemistry, geochronology and genesis of the late Miocene porphyry Cu-Au-Mo mineralization at Afyon-Sandıklı (AS) prospect, western Anatolia, Turkey

Afyon-Sandıklı ‘AS’ is an example of a porphyry Cu-Au-Mo systems hosted in post-collisional late Miocene magmatic rocks within the Afyon-Ören Zone of Turkey. The systems were generated by multi-phase intrusions emplaced into early stage volcanic and volcanoclastic rocks of the Afyon volcanics. The REE and radiogenic isotope data from these rocks suggest a magma source containing residual garnet with a low hydrous phase. These collectively, favor a metasomatized mantle source for magmas generated in either subduction or post-collisional environments.Four main alteration types have been identified in the AS porphyry Cu prospect; potassic, phyllic, epidote-chlorite and advanced argillic. The alteration zones are centered around monzonite porphyry intrusives. Chalcopyrite and bornite are the main copper minerals in the potassic alteration zone with subordinate molybdenite. All are replaced by pyrite.The U-Pb SHRIMP analyses on a post-mineral micromonzonite porphyry dike yielded an age of 10.97 ± 0.09 Ma, whereas the host monzonite porphyry yielded an age range between 10.5 and 12.5 Ma. Ar-Ar geochronology on alunite constrains the timing of the argillic alteration at 11.2 ± 0.5 Ma.Fluid inclusion studies were performed on primary inclusions in quartz veins from the potassic and phyllic alteration zones. The primary fluid inclusions in quartz veins in both zones were classified as Type 1, single-phase vapor (V); Type 2, two-phase liquid-vapor (L-V); and Type 3, three-phase liquid-vapor-solid (L-V-S). Type 3 inclusions in the potassic alteration zone with weak phyllic overprint have higher homogenization temperatures compared to those in pervasive phyllic alteration zones. The majority group of fluid inclusions in the AS prospect are Type 2 inclusions with variable vapor and liquid abundances. This suggests boiling (phase separation) of the hydrothermal fluids, and post boiling trapping of the vapor and liquid. The presence of abundant multiphase (Type 3) inclusions in the AS prospect marks the stage when phase separation took place. The phase separation appears to have resulted in intermediate to high-salinity multiphase brines and daughter crystals in the residual fluid. Additionally, we suggest that superposition of phyllic and potassic alteration zones with a variety of Type 2 and Type 3 inclusions in the AS prospect should mark the stage at which mixing by relatively cooler and dilute meteoric water coupled with phase separation occurred.The calculated δ18O(fluid) vs δD(fluid) values for the alteration minerals display a wide range between the primary magmatic field to the meteoric water line. The δ18O(fluid) vs δD(fluid) values for biotite suggest a strong magmatic water influence during the formation of potassic alteration. Likewise, a very narrow range of δ34S, close to the sulfur isotope values of magmatic sulfur indicate a magmatic source, and may suggest that potassic alteration was caused by a uniform magmatic fluid source. Additionally, the enrichment in the δD(fluid) from biotite suggests that phase separation (boiling) was also active during potassic alteration. The overlapping pattern of the δ18O(fluid) vs δD(fluid) compositions for biotite and sericite indicate an isotopic similarity, and may suggest that they have been formed from a similar, predominantly magmatic fluid mixed to some degree with the meteoric water.

Investigation on heat transfer in line chill-down process with various cryogenic fluids

This paper focuses on the transient process of the pipe cooling by the internal flow of cryogenic fluid, which is a so-called cryogenic line chill-down process. Due to the increasing use of cryogenic fluid in various industries, the heat transfer characteristics during the line chill-down process are followed with great interest. One of the biggest concern is that there are no universal heat transfer correlations for simulating the chill-down process. This research aims to extend the quenching database with liquid oxygen and predict the cryogenic line chill-down process with a one-dimensional homogeneous model. The line chill-down experiments are performed by liquid oxygen with the mass flux range from 15.9 kg/m2-s to 75.9 kg/m2-s. A 7 m long stainless steel 316 horizontal tube is used as the test section. The empirical correlations for heat transfer coefficient of single-phase vapor convection and film boiling are suggested based on the chill-down experimental data of liquid oxygen, liquid argon, and liquid nitrogen. The line chill-down process is simulated by applying the empirical correlations in a one-dimensional homogeneous model. The feasibility of the dynamic simulation model is verified in the mass flux up to 868 kg/m2-s by simulating the chill-down experimental data in the literature. Moreover, the characteristics of the critical heat flux, critical heat flux temperature, and minimum heat flux temperature are also investigated by comparing various experimental data and the empirical correlations. This study provides not only the open experimental data with liquid oxygen, which is rarely found in the literature but also the numerical simulation method, which predicts the line chill-down time within ± 10% error.

A novel thermodynamic design model of a new HFO refrigerant single phase vapor jet cooling system

Vapor jet refrigeration system has been a promising research topic by far. This system bears such importance due to using low grade energy instead of the less economical high grade energy necessary for driving the conventional vapor compression refrigeration cycles despite the low COP values. The main purpose of the present work is to introduce a mathematical model to optimally size the single phase supersonic vapor ejector and to give a detailed picture on how the system operating conditions affect the main dimensions of the optimally operated ejectors. On the other hand, this paper is a predesign study of the operating conditions effect on the system performance parameters like the COP, entrainment and area ratios. The model is validated with experimental data mentioned in the literature and it gives high trusted results. Moreover, the model is general as it can be used with any refrigerant. However, the present results belong to the environment friendly hydro-fluoroolefin refrigerant (R1234yf) which will be increasingly adopted and a potential alternative for the currently used hydroflourocarbon (HFC) R134a.

Dew Points, Dielectric Permittivities, and Densities for (Hydrogen + Carbon Dioxide) Mixtures Determined with a Microwave Re-Entrant Cavity Resonator

Accurate dew-point, dielectric permittivity, and density measurements of two binary (H2 + CO2) mixtures with CO2 mole fractions of 0.94638 and 0.74576 were carried out utilizing an apparatus that employs a microwave re-entrant cavity resonator. Isochoric dew-point measurements were conducted at pressures up to 7.1 MPa and temperatures from T = (249.55 to 296.61) K for the (0.05362 H2 + 0.94638 CO2) mixture and between T = (251.63 and 280.44) K for the (0.25424 H2 + 0.74576 CO2) mixture. The combined expanded uncertainty with a level of confidence of approximately 95% (k = 2) in dew-point temperature and pressure ranged between (0.016 and 0.065) K and (0.0041 and 0.0177) MPa, respectively. Within 2.5%, the new data were consistent with the predictions of the GERG-2008 equation of state. Measurements of dielectric permittivity in the single-phase vapor region over the temperature range from (273.06 to 313.18) K at pressures up to 8.2 MPa and in the vicinity of the phase boundary were conducted to determine mixture molar densities by applying a method based on the polarizability mixing rule developed by Harvey and Prausnitz. The microwave-determined mixture densities near 5 MPa agree within 0.33% of reported values measured with a precision two-sinker magnetic suspension densimeter; mixture densities near 8 MPa agree within 1.33% of values calculated with the GERG-2008 equation of state.

Liquid–Vapor Phase Transitions and Critical Properties of the C3H7OH–C6H14 System

Proceeding from the experimental (p,T,x) and (p,ρ,T,x) dependences for mixtures of 1-propanol and n-hexane (mole fractions 0.2, 0.5, 0.8, and 0.9) in the two-phase (liquid–vapor), single-phase (liquid and vapor), near-critical, and supercritical regions, the parameters of the points of liquid–vapor phase transformations have been determined by the method of isochore kinks p = f(T)ρ,x and the parameters of the critical points have been found by the semigraphical method with allowance for the scaling behavior. The dependences of the pressure on temperature, density, and composition along the phase-coexistence curve are described by a three-parameter polynomial equation of state: expansion of the compressibility factor Z = p/RTρ in powers of the reduced density, reduced temperature, and composition. The mean relative error of deviation of the calculated pressures from experimental values does not exceed 1%. The temperature dependence of the system density along the liquid–vapor phase-coexistence curve is described by two power-law functions at critical exponent β0 = 0.338 ± 0.002: far from the critical point and in the symmetric part of the equilibrium curve. The mean relative error is 1.47%.

On the evaluation of dryout conditions for a heat-releasing porous bed in a water pool

This work is motivated by the problem of restraining temperature escalation inside a porous heat-releasing media submerged in a pool of liquid coolant. When coolant temperature reaches saturation, boiling begins in the bulk of the porous bed, with void generation rate determined by the heating power. Amount of void determines hydrostatic pressure difference that drives natural circulation of two-phase flow through the porous material. At a certain critical value of the heat release rate, the driving head cannot overcome drag of the two phase porous media flow, which results in complete evaporation of coolant in some zone. Temperature of material in the dry zone increases significantly due to deterioration of heat exchange with single phase vapor flow in comparison with boiling flow heat transfer. The paper considers the problem of determining the critical conditions for onset of dryout in a heat-releasing porous bed of an arbitrary shape. The well-known one-dimensional problem for a flat top-flooded bed is revisited, and the functional form of the dryout boundary (expressed as the dryout heat flux, DHF) is derived using non-dimensional parameters. Asymptotic behavior of the solution is analyzed, and, by the method of asymptotic interpolation, a surrogate model is proposed consisting of three single-argument, non-dimensional functions. It is shown that such a model provides acceptable accuracy even in the cases where complete similarity of solutions is not achieved. The results obtained provide important insights into the physics of the problem, reduce the number of free parameters, and enable fast evaluation of dryout conditions without the need of numerical solution of algebraic equations involved in the exact formulation. The ultimate goal of the surrogate model development, i.e. its application to multidimensional configurations, is discussed.

A ROBUST STATISTICAL ALGORITHM FOR BOUNDARY DETECTION IN LIQUID SPRAYS

This work presents a statistical algorithm to detect phase boundaries in liquid sprays. Experimental data were obtained in a nonevaporating acetone spray at atmospheric conditions to minimize the refractive index gradients and associated beam steering. Mie scattering and diffuse background illumination (DBI) diagnostics are implemented to demonstrate the robustness of the approach. The analysis shows that the present algorithm yields similar results for the two different diagnostics, unlike existing threshold-based methodologies providing inconsistent results. The algorithm can be used to identify partial liquid boundaries between single-phase liquid and vapor boundaries. Thus, for each case, liquid boundaries were defined in terms of liquid probability of 100% or less than 100%. Sprays from two different injectors were analyzed to demonstrate the versatility of the methodology. A parametric study was conducted to demonstrate that motion blur can affect an accurate detection of the phase boundaries, and hence, the exposure time in the experiment must be sufficiently small.