Vapor Liquid Density Research Articles

Thermal transfer performance and flow instability analysis of direct steam generation for parabolic trough solar collectors

Parabolic trough solar direct-steam-generation (DSG) technology is the enabling technologies to achieve low carbon future. However, actual inlet boundary and flow boiling instabilities pose challenge to safe operation. In this paper, the coupled optical-thermal-flow pattern model for DSG loops is built utilizing conservation equations, separated flow model and Lagrangian method. The heat transfer performance, hydrodynamic characteristics and two-phase flow law of the loop are discussed under the coupled variation of direct radiation intensity (DNI), mass flow (m), inlet temperature (Tin) and inlet pressure (Pin). The correlation between multi-condition, thermodynamic characteristics and flow instability is analyzed. The results show that increasing Pin, Tin and DNI have almost no effect on the intermittent state. The percentage of annular flow only remained stable (about 84.8%) when the steam mass was 1. Increasing DNI and Tin did not effectively improve the flow heat transfer, while increasing Pin worsened the flow heat transfer and increased the probability that the annular flow would turn into stratified flow but could reduce the pressure drop and the fluid vapor-liquid density difference and stabilizes its hydrodynamic properties. The simultaneous increase in m not only weakens this effect and strengthens the heat transfer, but also permanently reduces the probability of stratified flow. The higher the Pin, Tin and DNI, the lower the flow instability of the DSG system. Manual operation is recommended to prevent the system having flow instability in the morning due to the lower solar radiation intensity and inlet temperature when the system is started in the morning.

Influence of molecular parameters on the representativeness of interfacial properties of simple fluids.

New parameterizations for the Lennard-Jones 12/6 potential capable of reproducing the vapor pressure and surface tension with sufficient precision, but not the liquid-vapor equilibrium densities for the case of simple fluids that include Ar, Kr, Xe, Ne, and CH4 are presented in this work. These results are compared with those derived from the family of Mie(n, 6) potentials, which adequately reproduce the coexistence curve and the vapor pressure, leaving aside the surface tension. In addition, a detailed analysis is presented on different parameterizations and methodologies, which have been developed in recent decades to estimate the interfacial properties of interest here for simple fluids, such as argon, which is a molecule that is, in principle, "simple" to study but that clearly reveals the enormous discrepancy between the results reported in the literature throughout these years. These facts undoubtedly reveal one of the fundamental problems in the context of molecular thermodynamics of fluids: reproducing different thermodynamic properties with sufficient precision from a single set of free parameters for some interaction potential. In order to show the scope of the parameterizations presented for the Lennard-Jones model, they were successfully applied to the case of binary mixtures, which included Ar-Kr, Ar-CH4, and Xe-Kr. Finally, and with the aim of showing a possible solution to the problem posed in this research, results of the same interfacial properties above mentioned for argon and methane were presented in this work by using a set of molecular interactions, called ANC2s, whose flexibility allowed to reproduce the experimental evidence with just one parameterization. The results reported in this work were generated using molecular dynamics simulations.

Flow boiling of liquid nitrogen in a horizontal macro-tube at low pressure: Part Ⅱ – Heat transfer characteristics

Nitrogen is the most important cryogen in superconductivity. This study investigates the heat transfer characteristics of flow boiling in a horizontal macro-tube with an inner diameter of 10 mm, particularly focusing on flow boiling at negative gauge pressure. The experiments cover the following ranges: inlet pressure from −31.0 to 2.5 kPa, mass flux from 27.0 to 71.3 kg/(m2·s), and heat flux from 0 to 28.68 kW/m2. The effects of operating parameters on the heat transfer coefficient (HTC) are examined, and the HTC data are compared with the predicted value from four correlations. At the bottom wall, the HTC distribution exhibits a “two-peak” shape. The primary peak is dominated by nucleate boiling in bubbly, plug, and slug flow with low vapor quality, while the secondary peak is dominated by convective evaporation with higher vapor quality. These two regions are roughly divided by the vapor quality of 0.3 to 0.4. In stratified flow, the HTC at the top wall is generally lower than that at the bottom. The HTC increases as the pressure decreases, particularly in the convective evaporation region. This is attributed to the high liquid–vapor density ratio, extensive thermal conductivity, and substantial surface tension at lower pressure. The effect of heat flux or mass flux on the HTC at the bottom wall differs between the nucleate boiling and convective evaporation regions. Increasing the heat flux improves the HTC where nucleate boiling dominates, while increasing the mass flux significantly improves convective evaporation, especially at higher heat flux. All selected correlations overestimate the HTC at the top wall. The Shah correlation demonstrates the best prediction accuracy for the HTC at the bottom wall, both at near atmospheric pressure (Mean Relative Error, MRE = 21 %) and at negative pressure (MRE = 19 %).

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.

Modeling liquid–vapor phase change experiments: Cryogenic hydrogen and methane

Mass accommodation coefficients are essential inputs to kinetic models of liquid–vapor phase change, yet after nearly 100 years there remains significant discrepancy in reported values. These discrepancies have been attributed to a wall material or geometric dependency resulting in the need for an empirical correction factors. The lack of experimental results for cryogenic fluids poses a serious impediment to modeling/predicting propellant behavior for long term space missions. Using a combination of neutron imaging experiments and multi-scale modeling, mass accommodation coefficients for liquid hydrogen and methane are determined. When the local variation in thermophysical properties are accounted for, the experimentally derived accommodation coefficients for hydrogen are invariant to container size, material and evaporation rate. The discrepancy in prior measurements of the accommodation coefficient for other fluids can be alleviated by a multi-scale analysis that incorporates local variation in thermophysical properties. The values of accommodation coefficients for hydrogen and methane are consistent with generalized transition state theory. This suggests that a mass accommodation coefficient is a solely a function of the liquid–vapor density ratio, making it a fluid-independent property easily determined without the need for empirical correction factors as reported in previous investigations.

Machine Learning-Enabled Development of Accurate Force Fields for Refrigerants.

Hydrofluorocarbon (HFC) refrigerants with zero ozone-depleting potential have replaced chlorofluorocarbons and are now ubiquitous. However, some HFCs have high global warming potential, which has led to calls by governments to phase out these HFCs. Technologies to recycle and repurpose these HFCs need to be developed. Therefore, thermophysical properties of HFCs are needed over a wide range of conditions. Molecular simulations can help understand and predict the thermophysical properties of HFCs. The prediction capability of a molecular simulation is directly tied to the accuracy of the force field. In this work, we applied and refined a machine learning-based workflow to optimize the Lennard-Jones parameters of classical HFC force fields for HFC-143a (CF3CH3), HFC-134a (CH2FCF3), R-50 (CH4), R-170 (C2H6), and R-14 (CF4). Our workflow involves liquid density iterations with molecular dynamics simulations and vapor-liquid equilibrium (VLE) iterations with Gibbs ensemble Monte Carlo simulations. Support vector machine classifiers and Gaussian process surrogate models save months of simulation time and can efficiently select optimal parameters from half a million distinct parameter sets. Excellent agreement as evidenced by low mean absolute percent errors (MAPEs) of simulated liquid density (ranging from 0.3% to 3.4%), vapor density (ranging from 1.4% to 2.6%), vapor pressure (ranging from 1.3% to 2.8%), and enthalpy of vaporization (ranging from 0.5% to 2.7%) relative to experiments was obtained for the recommended parameter set of each refrigerant. The performance of each new parameter set was superior or similar to the best force field in the literature.

Resolving the spatial scales of mass and heat transfer in direct plasma sources for activating liquids

When plasma is in direct contact with liquid, an exchange of mass and heat between the two media occurs, manifested in multiple physical processes such as vaporization and multiphase heat transfer. These phenomena significantly influence the conditions at the plasma–liquid interface and interfere with other processes such as the multiphase transport of reactive species across the interface. In this work, an experimentally validated computational model was developed and used to quantify mass and energy exchange processes at a plasma–liquid interface. On the liquid side of the interface, it was shown that a thin film of liquid exists where the temperature is approximately three times higher than the bulk temperature, extending to a depth of 10 μm. As the depth increased, a strongly nonlinear decrease in the temperature was encountered. On the plasma side of the interface, plasma heating caused background gas rarefaction, resulting in a 15% reduction in gas density compared to ambient conditions. The combined effect of gas rarefaction and liquid heating promoted vaporization, which increased liquid vapor density in the plasma phase. When water is the treated liquid, it is shown that water vapor constitutes up to 30% of the total gas composition in the region up to 0.1 mm from the interface, with this percentage approaching 70–80% of the total gas composition when the water’s temperature reaches its boiling point.

Discrete Boltzmann multi-scale modelling of non-equilibrium multiphase flows

The aim of this paper is twofold: the first aim is to formulate and validate a multi-scale discrete Boltzmann method (DBM) based on density functional kinetic theory for thermal multiphase flow systems, ranging from continuum to transition flow regime; the second aim is to present some new insights into the thermo-hydrodynamic non-equilibrium (THNE) effects in the phase separation process. Methodologically, for bulk flow, DBM includes three main pillars: (i) the determination of the fewest kinetic moment relations, which are required by the description of significant THNE effects beyond the realm of continuum fluid mechanics; (ii) the construction of an appropriate discrete equilibrium distribution function recovering all the desired kinetic moments; (iii) the detection, description, presentation and analysis of THNE based on the moments of the non-equilibrium distribution ( $f-f^{(eq)}$). The incorporation of appropriate additional higher-order thermodynamic kinetic moments considerably extends the DBM's capability of handling larger values of the liquid–vapour density ratio, curbing spurious currents, and ensuring mass/momentum/energy conservation. Compared with the DBM with only first-order THNE (Ganet al.,Soft Matt., vol. 11 (26), 2015, pp. 5336–5345), the model retrieves kinetic moments beyond the third-order super-Burnett level, and is accurate for weak, moderate and strong THNE cases even when the local Knudsen number exceeds$1/3$. Physically, the ending point of the linear relation between THNE and the concerned physical parameter provides a distinct criterion to identify whether the system is near or far from equilibrium. Besides, the surface tension suppresses the local THNE around the interface, but expands the THNE range and strengthens the THNE intensity away from the interface through interface smoothing and widening.

CFD study on film boiling features of cryogenic fluid influenced by heat structures and gravity levels

Understanding bubble behaviors and thermal characteristics under various working conditions is of great significance to the efficient utilization of cryogenic propellants. In the present study, simulation models of pool film boiling at horizontal plate and cylinder surface are proposed with Volume of Fluid (VOF) method combined with Lee’s phase change model. Based on the physical and thermal performance, the gravity levels, physical properties, and heater structure dimensions are investigated respectively, which could satisfy the common application conditions of cryogenic propellants. The results show that the movement of bubbles at gas–liquid interface is critical to the pool film boiling heat transfer, and also the heat transfer mechanism affects the bubble motion behaviors. The critical wavelength and the most dangerous wavelength are significant length scales for the bubble behaviors in pool film boiling. When the cylindrical heater size is larger than the most dangerous wavelength, the bubble behaviors as well as the heat flux appear the similar characteristics with that at the plate heater surface. Moreover, the critical wavelength is approximately two times of the bubble departure diameter in the present cryogenic liquid boiling events, and the parameters, including liquid–vapor density difference, surface tension, and gas thermal conductivity, could affect the boiling heat flux significantly. In addition, under 0.03g condition, the bubble departure diameter could reach 27 mm and the boiling heat flux decreases to 800 W/m2, which are significantly different from that in normal gravity. In general, the present CFD model could execute a film boiling study accurately, and a series of detailed results on the bubble behaviors as well as the heat flux could be revealed.

Modeling and Optimization of the Bubble Detachment Diameter for a Pool Boiling System

AbstractPrediction of boiling heat transfer for pool boiling systems is crucial from the viewpoint of safe operation as well as in terms of logical use of energy. Here, five pool boiling processes for calculating the bubble detachment diameters are described. The effects of liquid density and vapor density on the bubble detachment diameter of these pool boiling systems, namely, ethanol, methanol, water, Na2SO4‐water, and NaCl‐water, are determined by applying response surface methodology. According to P‐values and analysis of variance, there is a good agreement between the obtained regression models for the five pool boiling processes and experimental data for estimation of the bubble detachment diameters.

Numerical and theoretical investigations of the cavitation performance and instability for the cryogenic inducer

Cryogenic pumps are widely used in the fields of liquid rocket engines, liquefied natural gas (LNG) transportation, and International Thermonuclear Experimental Reactor (ITER) systems. An inducer is usually installed in front of the cryogenic pump to prevent the pump performance deterioration and flow instabilities caused by cavitation. The objectives of this paper are to investigate the influence of flow conditions on the thermal cavitation in a cryogenic inducer and purpose the theoretical models to predict the inducer performance and flow instabilities. In the present study, inducer working at different inlet temperature and rotating speed with liquid nitrogen was numerically investigated. The results show that the temperature drop around cavity regions increases and the cavity volume decreases with the increasing temperature, which leads to the delay of the drop of head coefficient. The increase of rotating speed leads to the increase of cavity volume and earlier deterioration of cavitation performance. The sub-synchronous rotating cavitation is observed in the inducer. It is characterized by the FFT analysis of cavity area fluctuation. The increase of temperature suppresses both the size and unevenness of the cavitation on each blade. Further analysis indicates that the temperature drop resulting from the cooling effect of evaporation around the cavitation area is significant due to the smaller liquid-vapor density ratio. A theoretical prediction model and a one-dimensional analysis model were developed to investigate the cavitation performance and instability. The theoretical models can accurately predict the influence of thermodynamic effect on the inducer cavitation and the pressure fluctuation inside the blade channel. These theoretical models can be applied to the design and testing of cryogenic pumps in practical applications.

Numerical simulation of bubble dynamics and heat transfer in the 2D saturated pool boiling from a circular surface

In this paper, the saturated pool boiling heat transfer from a heated circular surface is investigated numerically based on the popular lattice Boltzmann phase-change method. The crucial interfacial phenomena, including the bubble growth, departure, coalescence, and rising under different wall superheats, wettabilities, and heater sizes are studied, and the corresponding heat transfer characteristics within these bubble dynamics are also revealed. The numerical experiments indicate that at low wall superheats the bubble nucleation occurs only at the top of the heated circle. With the increase in the wall superheat, the sides and the bottom of the heated circle also become nucleate sites. As the wall superheats continue to increase, more and more nucleate sites are activated so that the heated circle is wrapped by the vapor film early in the boiling process. And the average heat flux varies periodically with time corresponding to bubble dynamics in nucleation boiling regime. It reaches a steady state of film boiling regime after the stable vapor film is generated from the heated circular. It is also found that hydrophobic surface is conducive to the onset of boiling. However, it leads to a low critical heat flux and incurs film boiling at a lower wall superheat, which is also observed in both experimental and numerical studies. On the other hand, the boiling regimes can undergo the transition from nucleate boiling regime to film boiling regime at the same wall superheat with the increase in the heater size. In addition, under various wall superheats and wettabilities, the bubble departure diameters from the circular surface are smaller than those from the flat surface, while the bubble departure periods from the circular surface are less than those from the flat surface one. Finally, the saturated boiling curves from the circular surface for different wall wettabilities, heater sizes, liquid–vapor density ratios, and heating modes are also achieved.

Thermodynamic Process Simulation and Evaluation on Surface-Mounted Evaporative Cooling System

The change of exergy has a direct impact on the circulation head of the surface-mounted evaporative cooling system that relies on the change of vapor-liquid density for circulating cooling. In this paper, the circulation system of the surface-mounted evaporative cooling system is taken as the research object. Based on the second law of thermodynamics, an exergy analysis model of main equipment is established to analyze and evaluate the characteristics of exergy change of the system. The research results show that under different thermal loads, the exergy efficiency is less than 70%, the exergy loss in the liquid box is relatively large, and the main irreversible exergy loss in liquid box occurs in the vapor-liquid boiling process, which will restrict the cooling capacity of the system. This study provides a theoretical basis for further optimizing the flow heat transfer process of the surface-mounted evaporative cooling system.

Attainment of rigorous thermodynamic consistency and surface tension in single-component pseudopotential lattice Boltzmann models via a customized equation of state.

The lack of thermodynamic consistency is a well-recognized problem in the single-component pseudopotential lattice Boltzmann models which prevents them from replicating accurate liquid and vapor phase densities; i.e., current models remain unable to exactly match coexisting density values predicted by the associated thermodynamic model. Most of the previous efforts had attempted to solve this problem by introducing tuning parameters, whose determination required empirical trial and error until acceptable thermodynamic consistency was achieved. In this study, we show that the problem can be alternatively solved by properly designing customized equations of state (EOSs) that replace any cubic EOS of choice during the computation of effective mass used in Shan-Chen forces. A two-parameter cubic-shaped customized EOS is introduced. Contrary to previous efforts, customization parameters in the new EOS are nonempirical and are rather derived from solving the integral mechanical stability equation, which neglects the need for any type of tuning for the attainment of rigorous thermodynamic consistency. The proposed approach reduces the errors of the coexisting densities and saturated pressure in the simulation to a maximum of 0.01% within the liquid-vapor density ratio range from O(1) to O(10^{4}), which had not been achieved in any of the previous tuning-based efforts. A straightforward way for achieving the desired surface tension via the customized EOS is also provided.

Volumetric properties of carbon dioxide + acrylic acid binary in the context of supercritical precipitation polymerization

Acrylic acid can be polymerized by precipitation in different solvents. Carbon dioxide is an interesting solvent given its tunable density and solvent power depending on the pressure and temperature. These physicochemical characteristics make it possible to solubilize some polar compounds in CO 2 depending on temperature and pressure. In this work, we report pressure vs volume pseudo-continuous curves at constant temperature for the CO 2 + AA binary mixture. They were determined in a fully computerized variable-volume high-pressure view cell capable of monitoring the position of the piston. The experimental data is simultaneously isoplethic and isothermal and it covers a wide range of pressures (up to 20 MPa). Using this raw experimental data, other properties were determined such as liquid-vapor phase boundaries, density and excess volumes. The temperature range was 313.15–363.15 K and the mole fraction of AA in the mixture was increased from 0.044 to 0.594.

Ledinegg instability analysis on direct vapor generation inside solar collectors

Compared with direct steam generation (DSG), direct vapor generation (DVG) system based on organic working fluid has better application potential in low and medium temperature distributed system. However, there is a lack of understanding of the two-phase flow instability that commonly occurs in DVG systems and can cause fatal damage to the system. In this paper, Ledinegg instability is considered as a common flow instability, and its occurrence characteristics and avoidance strategies are presented. First, a theoretical model was established to study Ledinegg instability of organic working fluid. Then, the effects of heat flux q, inlet subcooling Tc, length-to-diameter ratio L/D and fluid properties are analyzed. Particularly, a characteristic parameter RL representing the possibility of Ledinegg instability is proposed for the first time in performance evaluation of Ledinegg instability. The results show that as L/D decreases from 200 to 100, RL reduces from 0.88 to 0.25. As q increases from 10 kW/m2 to 30 kW/m2, RL increases from 0.54 to 1.03. When Tc is less than 3 °C, RL approaches 0 and Ledinegg instability disappears. With the increase of surface tension σ and the latent heat of vaporization r, the decreases of vapor-liquid density ratio ρsv/ρsl and the decreases of vapor-liquid viscosity ratio μsv/μsl, RL increases. The physical equation describing RL of Ledinegg instability is helpful to guide DVG system to reduce or avoid Ledinegg instability in design and operation.

Effect of instantaneous change of surface temperature and density on an unsteady liquid–vapour front in a porous medium

This article presents a comprehensive analysis of time dependent condensation model embedded in a porous medium with variations in liquid–vapour densities. Both similarity and asymptotic solutions for the unsteady liquid–vapour phase change front are obtained with the manifestation of various pertinent parameters. The obtained results are compared which congregate well as depicted clearly in graphs. Results indicate that with different diffusivity and contrast ratios, the similarity front parameter is found to be gradually declining with variation in a density ratio. We have shown for the condensation process, the ratio of sensible to latent heat is independent of time and is equal to the half of the Stefan number of the liquid phase.

Operational behavior and heat transfer in a thermosiphon desorber at sub-atmospheric pressure. Part I: The model

The thermosiphon desorber or bubble pump is advantageous in absorption cooling devices, since the processes of refrigerant desorption and solution pumping is combined in one hermetical unit. This supersedes the necessity of a mechanical solution pump. In the application with NH3/H2O the thermosiphon desorber typically operates at a pressure of around 15 bar with a liquid vapor density ratio in the range of 102, which is in a well-known regime of two phase flow. Nevertheless, for the application of thermosiphon desorbers in H2O/LiBr absorption chillers, which are commonly operated at a pressure below 0.1 bar with the liquid vapor density ratio in the range of 104, there is a lack of heat transfer correlations for two-phase flow.First attempts to fill this gap of flow boiling heat transfer correlations in the thermosiphon desorber at sub-atmospheric pressures is presented in this paper. A model is formed by solving simultaneously the mass, energy, and momentum equations. The well-known correlations for predicting single-phase and two-phase flow heat transfer coefficient and frictional pressure drop have been reviewed to find a possibility for applying them to the thermosiphon desorber. The mass flow rate and heat transfer behavior with the different flow length of the riser tube and with changing the pressure has been theoretically studied in the model. For verification, the model has been compared to experimental data using pure water. This will be presented in the second part of the paper.

The effect of Cu nanoparticles on the characteristics of vapor–liquid interface of argon at various saturated temperatures by molecular dynamic simulation

In this study, the effect of copper nanoparticles on the interface properties of liquid–vapor argon is investigated by molecular dynamics simulation. Stoddard Ford potential function has been utilized to estimate the interactions of argon–argon and argon–copper particles. Simulation is done in the nanoscale computational domain to phase change of vapor to liquid at different saturated temperatures. Density values and surface tension for different cutoff radii are obtained. It is demonstrated that in the $$r_{\text{c}} = 4\sigma$$ calculated values are acceptable. Simulation results show that nanoparticles change the interface properties of liquid–vapor argon. With addition of nanoparticles, liquid density decreases and vapor density increases. Nanoparticles displace density distribution and cause fluctuations in the density profile. Also, surface tension increases with increase in nanoparticle concentration.

Flow and heat transfer characteristics of microchannel flow boiling enhancement with channel configurations

The heat dissipation problem encountered in the process of the development of new electronic equipment and mechanical components towards miniaturization has become the bottleneck of continuous progress in the field of mechanical and electronic control engineering, and the flow boiling heat transfer technology in microchannel may provide the effective cooling guarantee for this purpose. Given the reasonable operating temperature ranges of devices and the diversity of coolant evaporation temperature and pressure choices, refrigerants have become an important option, especially for zeotropic mixtures, which can not only modulate the properties of pure components, but also present the unique phase change heat transfer characteristics with great application prospects. In the present study, the flow boiling heat transfer research of R134a/R245fa zeotropic mixtures as well as their pure compartments in parallel multi-microchannel with continuous and segmented channel configurations were experimentally studied. Each microchannel test section consisted of seven parallel channel passages with the same total length of 110 mm. The cross-sectional area of each channel passage was 2 mm × 1mm (width×height) with the slab width of 0.5 mm. What difference from continuous microchannel was that 10 mm-long interconnected area was arranged every 30 mm along the channel length in segmented one. The experiments were carried out at the same inlet saturation temperature of 26 °C under the conditions comprising the heat flux range of 20− 350 kW/m2 and mass flux range of 300− 400 kg/(m2 s), respectively. In order to obtain more accurate data matching relationship, the analysis of heat transfer performance focused on the region near the outlet of the test sections. It’s worth noting that the multi-microchannel should be treated as fin effects during the heat transfer data reduction. The ribbed slabs could be considered as the rectangular straight fins either for continuous or segmented multi-microchannel. The results showed that compared with continuous microchannel, the heat transfer performance was slightly enhanced for pure components while slightly suppressed for zeotropic mixtures in segmented microchannel at lower effective heat flux. With the increase of effective heat flux, the heat transfer suppression effect of zeotropic mixtures was gradually weakened. The interconnected area was helpful to delay the occurrence of the transfer deterioration and improve the flow boiling CHF regardless of pure or zeotropic refrigerants. Besides, the flow boiling pressure drop in segmented microchannel was obviously reduced for zeotropic mixtures and their pure components. The smaller the liquid-vapor density ratio of test refrigerants, the higher the reduction of pressure drop with the help of interconnected area. For zeotropic mixtures, the flow boiling pressure drop was smaller at lower effective heat flux and the increasing trend of pressure drop on heat flow is slower.