Non-azeotropic Mixtures Research Articles

A 2D numerical study on the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures on a vertical plate

To improve the transportation efficiency and reduce the supply cost, the liquefaction becomes an important technology to store and transport the natural gas. During the liquefaction, the various components (e.g. propane, ethane, methane etc.) undergo fractional condensation phenomenon due to their different boiling points. This means that when one component condenses, others play a role of non-condensable gas (NCG). In order to reveal the influence mechanism of NCG on this condensation process, a numerical method was employed in this paper to study the condensation characteristics of three non-azeotropic binary hydrocarbon vapor mixtures, namely the propane/methane (80%–95%), ethane/methane (65%–85%) and methane/nitrogen (2%–13%) mixtures, on a vertical plate. The model was proposed based on the diffusion layer model, and the finite volume method was used to solve the governing equations. A user defined function was developed by cell iterative method to obtain the source terms in the condensation process. The numerical results show that the gas phase boundary layer formed by the NCG becomes the main resistance to the reduction of heat transfer coefficient. And for the above three mixtures, there is a negative correlation between the NCG concentration and the heat transfer coefficient. Meanwhile, the results show a good agreement with the experimental data, meaning that the proposed model is reliable. Three mixtures within same non-condensable mole fraction of 20% were also investigated, indicating that the mixtures with a higher binary hydrocarbon molecular ratio have a lower heat transfer coefficient. As a result, the presence of the lighter NCG contributes to a thicker boundary layer.

Investigation and Analysis of R463A as an Alternative Refrigerant to R404A with Lower Global Warming Potential

This research presents the development of R463A refrigerant, a nonflammable refrigerant that was retrofitted to replace R404A. R463A is primarily composed of hydrofluorocarbons/hydrocarbons/carbon dioxide (HFCs/HCs/CO2), and has global-warming potential (GWP) of 1494. It is a nonazeotropic mixture of R32 (36%), R125 (30%), R134a (14%), R1234yf (14%), and R744 (6%). R463A is composed of polyol ester oil (POE), and it is classified as a Class A1 incombustible and nontoxic refrigerant. R463A has a higher cooling capacity (Qe) than that of R404A, as it is composed of hydrofluorocarbons (HFCs) R32 and carbon dioxide (CO2) R744, and has lower GWP than that of R404A due to the use of hydrofluoroolefins (HFOs) from R1234yf. The results of this research showed that R463A can be retrofitted to replace R404A due to its composition of POE, Class A1 incombustibility, and lower toxicity. The properties of R463A and R404A, as analyzed using national institute of standards and technology (NIST) reference fluid thermodynamic and transport properties database (REFPROP) software and NIST vapor compression cycle model accounting for refrigerant thermodynamic and transport properties (CYCLE_D-HX) software, are in accordance with the CAN/ANSI/AHRI540 standards of the Air-Conditioning, Heating, and Refrigeration Institute (AHRI). The normal boiling point of R463A was found to be higher than that of R404A by 23%, with a higher cooling capacity and a 63% lower GWP value than that of R404A. The critical pressure and temperature of R463A were found to be higher than those of R404A; it can be used in a high-ambient-temperature environment, has higher refrigerant and heat-rejection effects, and has lower GWP than that of R404A by 52% due to the HFOs from the R1234yf component. The cooling coefficient of performance (COPc) of R463A was found to be higher than that of R404A by 10% under low-temperature applications. R463A is another refrigerant option that is composed of 7% carbon dioxide (CO2), and is consistent with the evolution of fourth-generation refrigerants that contain a mixture of HFCs, HFOs, HCs, and natural refrigerants, which are required to produce a low-GWP, zero-ozone-depletion-potential (ODP), high-capacity, low-operating-pressure, and nontoxic refrigerant.

THE ENGINEERING METHODS FOR DETERMINING THE GEOMETRIC DIMENSIONS OF MULTI-TUBE BI-COOLANT CAPACITORS

Artificial cold is widely used in various industries and agriculture, transportation, air conditioning systems and many other fields of science and technology. High-quality equipment for the production of cold is also important for the technical equipment of the Armed Forces, because it is sometimes necessary to provide certain temperature conditions for the reliable operation of electronic means for various purposes and electronic equipment of weapons. In a hot climate, there is a need to create comfortable conditions for the personnel of the units, as well as ensuring quality storage of food and water. An important device of any refrigeration machine is the condenser of coolant, which significantly determines its efficiency. Recently, much attention is paid to the study and application of mixtures of known refrigerating agents along with single-component substances. It is shown that in certain cases, mixtures of coolants can improve the volumetric and energy parameters of low-temperature installations and obtain this effect without significant structural changes. This is very promising for mobile installations, including military ones, which have to work in various climatic conditions that require adjustment of cooling capacity. A promising working substance of bi-cooling plants is a binary non-azeotropic mixture of freons-12 and 22. The mode of operation of bi-coolant capacitors differs from the modes of operation of one-component devices, which is explained by the mutual influence of heat and mass transfer processes occurring together in the boundary vapor layer at the condensation surface and the condensate film. This circumstance makes the strict calculation of the heat exchange surface of capacitors quite difficult. In such calculations, it is necessary to use data on the thermophysical properties of the mixture in both the steam and liquid phases. However, these data cannot be found in the literature for all promising two-component refrigerants. Data on the vapor-liquid equilibrium of mixtures are also required. Taking into account the above, in this work, an experimental study process of the condensation of pure freons-12 and 22, as well as their mixtures on a twenty-row sheaf of ribbing tubes, was carried out. The article describes the construction of the experimental capacitor and the method of measurement. The obtained experimental formulas for calculating condensation on single horizontal pipes and on a sheaf of horizontal pipes, as well as on the impact of the rows of condenser pipes on heat transfer are presented. The obtained data are compared with the literature data. The results of the experiment allowed us to propose a simplified engineering method for calculating the condensation surface of multi-tube bi-coolant capacitors. In addition, a method for calculating the basic geometric parameters of such shell-and-tube capacitors in the industrial load range is proposed.

Experimental study on flow boiling heat transfer characteristics of R134a, R245fa and R134a/R245fa mixture at high saturation temperatures

The flow boiling heat transfer characteristics of R245fa, R134a and non-azeotropic mixture R134a/R245fa (0.33/0.67 by mass) at high saturation temperatures were investigated in a horizontal tube with 10 mm I.D. Effects of high saturation temperatures on heat transfer coefficients of R134a, R245fa and the mixture were investigated from 55 °C to 95 °C. Heat flux was controlled from 6 to 24 kW/m2 and mass flux ranged from 100 to 300 kg/m2.s. The results show the heat transfer coefficient of the mixture (R134a/R245fa with 33%/67% by mass) is much lower than that of pure R134a and is close to that of pure R245fa. At high saturation temperatures, mass flow rate has less influence on heat transfer coefficient of R245fa and the mixture at a large heat flux. The heat transfer coefficients of three working fluids increase slightly when the saturated temperatures change within 10 °C. The pressure drops of pure R245fa and the binary mixture were studied and the pressure drop of the mixture (R134a/R245fa with 33%/67% by mass) is a little higher than that of R245fa.A modified heat transfer correlation considering the mixing effect of binary mixture is proposed for the mixture of R245fa/R134a, and the mean absolute deviation is within 20%. A modified two phase frictional factor for the mixture is proposed and the deviation of the mixture using modified two phase frictional factor is between −6% and +22%.

Study on calculation method of condensation heat transfer for non-azeotropic hydrocarbon mixtures in helically coiled tubes

In order to study the condensation heat transfer characteristics of non-azeotropic hydrocarbon mixtures in helically coiled tubes for large-scale spiral-wound heat exchangers, a simplified physical model of three-section helical tubes was proposed. Reasonable governing equations and boundary conditions were set up, and the grid independence was verified. Then, the condensation heat transfer characteristics of mixture refrigerants were analyzed. In addition, considering the effect of mass transfer resistance of non-azeotropic mixtures on heat transfer during condensation, a method combining numerical simulation with the Bell and Ghaly correction method was proposed to calculate the condensation heat transfer coefficient of mixtures. By comparing with the experimental results, the accuracy of the calculation model is verified, which provides theoretical support for the design of large-scale spiral-wound heat exchangers.

Achieving a better understanding of binary azeotropic mixtures distillation through Aspen Plus process simulations

AbstractMass transfer operations are at the heart of every chemical engineering curriculum, as they are the basis of separation procedures extensively used in the chemical industry. Distillation, which involves mass transfer between vapor and liquid phases, is, by far, the most extended separation practice. However, the presence of azeotropes in most of the mixtures with industrial interest complicates the process analysis due to tedious and complex calculations, even in the simplest case of binary mixtures. Moreover, the need for recycle streams makes convergence and variables specification very difficult as compared with the separation of nonazeotropic mixtures. Initial training in process simulators results fundamentally in high‐quality chemical engineering teaching programs. It yields a better understanding of enhanced distillation and entails the use of professional tools highly demanded by employers. This paper reports how the use of the commercial simulator Aspen Plus can help students explore azeotropic distillation by their own, and thus enables looking into aspects which are beyond the scope of problems solved by hand.

Analysis of the effect of thermohydraulic irreversibility of processes in the cycle of a refrigeration machine with a non-azeotropic mixture of refrigerants

The object of research is the effect of thermohydraulic irreversibility of energy processes in the cycle of a refrigeration machine using an ozone-safe non-azeotropic mixture as a refrigerant on its energy efficiency. One of the most problematic places during the development and design of such refrigeration machines is that, due to the peculiarities of the thermodynamic properties associated with the different chemical composition of the components, non-azeotropic mixtures are characterized by differences in the equilibrium concentrations of the components in the liquid and vapor phases. This property of non-azeotropic mixtures presents a certain difficulty for their effective application in refrigeration machines and heat pumps. During the study, modern methods of analysis and synthesis of thermodynamic systems are used, based on the application of the theoretical apparatus of technical thermodynamics, thermoeconomics, the theory of heat and mass transfer, as well as elements of the theory of systems engineering. The issue of assessing the energy efficiency of the cycles of refrigeration units operating on a non-azeotropic mixture of refrigerants is considered, taking into account the variability of the composition of the components of the mixture. A method has been developed for the formation of the composition of a multicomponent mixture, taking into account the influence of the non-isobarity of processes in the hydraulic circuit of the refrigerant circulation on the energy efficiency of the refrigeration machine. Based on a numerical experiment, the influence of changes in the concentrations of the components of the mixture R32, R125, R134a on the non-isothermal phase transition in the evaporator and condenser, as well as on pressure losses in the hydraulic circuit elements of an autonomous air conditioner, is established. The effect of friction at a temperature level below ambient temperature on the exergy efficiency of the refrigeration machine is analyzed. An advanced exergy analysis of the refrigeration cycle with a non-azeotropic mixture is carried out, as a result of which the avoidable and unavoidable, as well as the endogenous and exogenous components of the destruction of exergy in the elements are determined. The proposed method, due to its visibility, can significantly simplify the finding of the thermodynamic parameters of the refrigerant at the nodal points of the refrigeration machine cycle during numerical simulation.

An MINLP formulation for the optimization of multicomponent distillation configurations

Designing configurations for multicomponent distillation, a ubiquitous process in chemical and petrochemical industries, is often challenging. This is because, as the number of components increases, the number of admissible distillation configurations grows rapidly and these configurations vary substantially in their energy needs. Consequently, if a method could identify a few energy-efficient choices from this large set of alternatives, it would be extremely attractive to process designers. This paper develops such a method by solving a Mixed Integer Nonlinear Program (MINLP) that is formulated to pick, among the regular-column configurations of Shah and Agrawal (2010b), those configurations that have a low vapor-duty requirement. To compute the minimum vapor-duty requirement for each column within the configuration, we use techniques that rely on the Underwood’s method. The combined difficulty arising from the nonlinearity of Underwood equations and the combinatorial explosion of the choice-set of alternatives poses unmistakable challenges for the branch-and-bound algorithm, the current method of choice to globally solve MINLPs. To address this difficulty, we exploit the structure of Underwood equations and derive valid cuts that expedite the convergence of branch-and-bound by enabling global solvers, such as BARON, infer tighter bounds on Underwood roots. This provides a quick way to identify a few lucrative alternative configurations for separation of a given non-azeotropic mixture. We illustrate the practicality of our approach on a case-study concerning heavy-crude distillation and on various other examples from the literature.

Combination of two-stage series evaporation with non-isothermal phase change of organic Rankine cycle to enhance flue gas heat recovery from gas turbine

Nowadays, gas turbines (GTs) are increasingly used in China, with a relatively low performance. Organic Rankine cycle (ORC) is promising to recover the flue gas heat recovery from GT. To efficiently enhance the heat recovery, two-stage series evaporation is combined with non-isothermal phase change of non-azeotropic mixtures. Thus, two-stage series organic Rankine cycle (TSORC) with six non-azeotropic mixtures, composed of R245fa and hydrocarbons, as the working fluids are investigated. The cycle performances of TSORC with non-azeotropic mixtures are compared with those of the ORC with pure working fluid. Moreover, a case study was conducted to illustrate the performance enhancement by TSORC with the non-azeotropic mixture for fuel gas waste heat from C200HP. The results show that the net power output, thermal and exergy efficiencies of the TSORC are superior to those of the ORC at the same mass fraction, especially for the net power output. Comparing with the stand-alone gas turbine of C200HP, the TSORC with cyclohexane/R245fa[0.8/0.2] increases the efficiency of C200HP system by 35.48%, and the power generation efficiency of the C200HP-TSORC system achieves 44.71%. The TSORC with non-azeotropic mixtures as the working fluids is advisable and can be popularized in engineering applications.

Droplet Evaporation of Non-azeotropic and Azeotropic Mixture on a Superheated Surface

Droplet Evaporation of Non-azeotropic and Azeotropic Mixture on a Superheated Surface

ANN-based correlation for frictional pressure drop of non-azeotropic mixtures during cryogenic forced boiling

A crucial aspect of Joule-Thomson cryocooler analysis and optimization is the accurate estimation of frictional pressure drop. This paper presents a pressure drop model for boiling of non-azeotropic mixtures of nitrogen with hydrocarbons (e.g., methane, ethane, and propane) in microchannels. These refrigerant mixtures are important for their applicability in natural gas liquefaction plants. The pressure drop model is based on computational intelligence techniques, and its performance is evaluated with the mean relative error (mre), and compared with three correlations previously selected as most accurate: Awad and Muzychka; Sun and Mishima; and Cicchitti et al.Comparison between the proposed artificial neural network (ANN) model and the three correlations shows the advantages of the ANN to predict pressure drop for non-azeotropic mixtures. Existing correlations predict experimental data within mre = 23.9–25.3%, while the ANN has mre = 8.3%. Additional features of the ANN model include: (1) applicability to laminar, transitional and turbulent flow, and (2) demonstrated applicability to experiments not used in the training process. Therefore, the ANN model is recommended for predicting pressure drop due to accuracy and ease of applicability.

Peculiarities of determination of the heat transfer coefficient at boiling of non-azeotropic mixtures in tubes

In this work, the calculation techniques for determining the heat transfer coefficient for boiling non-azeotropic mixtures in tubes are described. In particular, the dependencies proposed by the authors of Shin et al. (1997) and Mezentseva et al. (2014). These dependencies were used to calculate and compare the experimental data on the heat transfer coefficients for the boiling of a non-azeotropic mixture R32/R134a (30/70%) in copper smooth tube with a diameter of 6.34 mm. The results showed that the dependence of Mezentseva et al. (2014) is in good agreement with the experimental data with an accuracy of ± 15%. In addition, this dependence considers the corresponding heat exchange regime and requires less thermodynamic properties of the mixture in calculations.

Comprehensive evaluation of supercritical power cycle system using non-azeotropic mixtures driven by medium-temperature solar heat source

Aimed at the medium-temperature solar energy heat source, the use of low-boiling binary non-azeotropic organic mixtures as the supercritical cycle working fluids to generate power was put forward. On the premises of meeting the requirements of thermal property, safety, and economic efficiency, 8 working fluids combining R245fa with R152a according to different mass ratios were used and the supercritical thermal system mathematical model was established based on the first and second laws of thermodynamics. The cycle characteristics were contrasted from the multi-angle aspects including seven indices like thermal efficiency, exergy efficiency, and so on. Considering various factors, the multi-index comprehensive evaluation model of energy efficiency was constructed by using the analytic hierarchy process method. Through simulation calculations, the results show that properly increasing the proportion of R245fa promotes effective improvement of the supercritical cycle characteristics and working fluid R245fa/R152a(0.96/0.04) can improve the indexes including net output power, economy, and environmental performance of the system. The proposed one has the optimal evaluation index value among the candidates.

Flow boiling heat transfer of R123/R134a mixture in a microchannel

The flow boiling heat transfer of R123/R134a non-azeotropic mixture has been experimentally studied in a single microchannel of 190 μm ID for various experimental conditions: mixture composition (R123 ratio: 0.250, 0.502, 0.746), mass velocity (G = 314–470 kg/m2 s), heat flux (q″ = 10–20 kW/m2) and vapor quality (x = 0.2–0.9). The wall temperature is measured by a thermometer attached to the wall of the microchannel. Fluid temperature is measured at the inlet and outlet of the microchannel. The heat transfer coefficient is calculated based on the temperature, pressure, and mass flow measurement. The results indicate that the heat transfer characteristics of the mixed refrigerant are a function of mixture composition. The heat transfer for R123 mole fractions of 0.502 and 0.746 show good agreement with those resulting from the heat transfer mechanism of thin film liquid evaporation as pure R123. On the other hand, the heat transfer characteristics for R123 mole fraction of 0.250 indicates a heat transfer mechanism of nucleate boiling followed by two-phase forced convection of pure R134a. The criterion for the heat transfer mechanism concerning the flow boiling of mixed refrigerants in microchannels is determined by the presence of nucleate boiling at low vapor quality, which is identical to the criterion for pure refrigerants. The criterion of the heat transfer mechanism for mixed refrigerants is verified by the comparison with experimental results. Finally, the flow boiling heat transfer correlation for a mixed refrigerant in microchannels is developed from that for pure refrigerant using a correction reflecting the mass transfer effect in the mixed refrigerant. The new heat transfer correlation makes good predictions for experimental data. The new correlations can be applied to refrigerants which have similar thermophysical properties with R134a or R123.

Experimental investigation of single bubble growth in the boiling of the superheated liquid mixed refrigerants

The reduction of the bubble growth rate in mixed liquid refrigerants is one of the main reasons for the reduction of the boiling heat transfer coefficient. To study the mass diffusion effect and the reduction of the bubble growth rate in boiling of non-azeotropic mixtures, an experiment was conducted to investigate the bubble growth rates of R142b, R134a, isobutane and R142b/R134a mixtures in a vertical transparent quartz tube. The pressure used in this experiment ranged from 0.2 to 0.47 MPa, and the superheats ranged from 1.5 to 23.3 °C. Moreover, in order to obtain a uniformly superheated liquid, the bubbles were grown at a single nucleation site, and the departure frequency for the successive bubbles was lower than 20 Hz. Experimental bubble growth constants were obtained, and the reliability of the experimental study was supported by theoretical models for pure refrigerants. Additionally, for the study of bubble growth rate in binary mixtures, the attenuation factors for superheat were calculated and compared with different proposed models. The experimental attenuation factors were much smaller than the calculated results. Thus, a correlation was identified, and the errors were primarily in the range of −30% to +30%.

Prediction of heat transfer coefficients for forced convective boiling of N2-hydrocarbon mixtures at cryogenic conditions using artificial neural networks

A key problem faced in the design of heat exchangers, especially for cryogenic applications, is the determination of convective heat transfer coefficients in two-phase flow such as condensation and boiling of non-azeotropic refrigerant mixtures. This paper proposes and evaluates three models for estimating the convective coefficient during boiling. These models are developed using computational intelligence techniques. The performance of the proposed models is evaluated using the mean relative error (mre), and compared to two existing models: the modified Granryd’s correlation and the Silver-Bell-Ghaly method. The three proposed models are distinguished by their architecture. The first is based on directly measured parameters (DMP-ANN), the second is based on equivalent Reynolds and Prandtl numbers (eq-ANN), and the third on effective Reynolds and Prandtl numbers (eff-ANN).The results demonstrate that the proposed artificial neural network (ANN)-based approaches greatly outperform available methodologies. While Granryd's correlation predicts experimental data within a mean relative error mre = 44% and the S-B-G method produces mre = 42%, DMP-ANN has mre = 7.4% and eff-ANN has mre = 3.9%. Considering that eff-ANN has the lowest mean relative error (one tenth of previously available methodologies) and the broadest range of applicability, it is recommended for future calculations. Implementation is straightforward within a variety of platforms and the matrices with the ANN weights are given in the appendix for efficient programming.

Ocean Thermal Energy Conversion Using Double-Stage Rankine Cycle

Ocean Thermal Energy Conversion (OTEC) using non-azeotropic mixtures such as ammonia/water as working fluid and the multistage cycle has been investigated in order to improve the thermal efficiency of the cycle because of small ocean temperature differences. The performance and effectiveness of the multistage cycle are barely understood. In addition, previous evaluation methods of heat exchange process cannot clearly indicate the influence of the thermophysical characteristics of the working fluid on the power output. Consequently, this study investigated the influence of reduction of the irreversible losses in the heat exchange process on the system performance in double-stage Rankine cycle using pure working fluid. Single Rankine, double-stage Rankine and Kalina cycles were analyzed to ascertain the system characteristics. The simple evaluation method of the temperature difference between the working fluid and the seawater is applied to this analysis. From the results of the parametric performance analysis it can be considered that double-stage Rankine cycle using pure working fluid can reduce the irreversible losses in the heat exchange process as with the Kalina cycle using an ammonia/water mixture. Considering the maximum power efficiency obtained in the study, double-stage Rankine and Kalina cycles can improve the power output by reducing the irreversible losses in the cycle.

Experimental study on the concentration of ethylene glycol aqueous solution by metal powder sintered porous capillary wicks

In industry, the ethylene glycol concentration is realized by flashing and distillation and a series of processes. These processes with high energy consumption are complicated. To solve this problem, a method for concentrating ethylene glycol aqueous solution with metal powder sintered capillary wick is proposed. The capillary wick with length 50mm, outer diameter 30mm and inner diameter 10mm sintered by copper powder is used as an evaporator for ethylene glycol solution in this study. The effects of inlet flow rate, heating temperature, inlet concentration, as well as the pore size of the capillary wicks on the concentration of ethylene glycol are all analyzed experimentally. It is found that the ethylene glycol solution can be concentrated from the mass fraction of 10% at inlet to 16% at outlet through the capillary wick, which indicates that the concentration method proposed in this paper is feasible. Moreover, the evaporated water is generally positively correlated with inlet flow rate and evaporation temperature within a certain range, however, the evaporation will not increase when the inlet flow rate and heating temperature reaches a certain level due to the permeation and evaporation limitation effect. Increasing the inlet concentration reduces the volume of the condensate, but the corresponding increase in outlet concentration is not noticeable. It is also found experimentally that the capillary wick sintered with particles with 56.3μm diameter has the best concentration performance for the ethylene glycol solution. The concentration method proposed by this study is expected to be helpful for the dehydration of organic solvents or the separation of binary non-azeotropic liquid mixtures in industrial production.

Heat transfer degradation during condensation of non-azeotropic mixtures

International organizations call for a reduction of the HFCs production and utilizations in the next years.Binary or ternary blends of hydroflourocarbons (HFCs) and hydrofluoroolefins (HFOs) are emerging as possible substitutes for high Global Warming Potential (GWP) fluids currently employed in some refrigeration and air-conditioning applications.In some cases, these mixtures are non-azeotropic and thus, during phase-change at constant pressure, they present a temperature glide that, for some blends, can be higher than 10 K. Such temperature variation during phase change could lead to a better matching between the refrigerant and the water temperature profiles in a condenser, thus reducing the exergy losses associated with the heat transfer process. Nevertheless, the additional mass transfer resistance which occurs during the phase change of zeotropic mixtures leads to a heat transfer degradation. Therefore, the design of a condenser working with a zeotropic mixture poses the problem of how to extend the correlations developed for pure fluids to the case of condensation of mixtures. Experimental data taken are very helpful in the assessment of design procedures. In the present paper, heat transfer coefficients have been measured during condensation of zeotropic mixtures of HFC and HFO fluids. Tests have been carried out in the test rig available at the Two Phase Heat Transfer Lab of University of Padova. During the condensation tests, the heat is subtracted from the mixture by using cold water and the heat transfer coefficient is obtained from the measurement of the heat flux on the water side, the direct measurements of the wall temperature and saturation temperature. Tests have been performed at 40°C mean saturation temperature. The present experimental database is used to assess predictive correlations for condensation of mixtures, providing valuable information on the applicability of available models.

Heat transfer at nucleate boiling of non-azeotropic mixtures

At present, there is no sufficiently reliable and physically proved method for calculating the heat exchange coefficient in boiling of non-azeotropic mixtures. The main cause is complexity of the mechanism of boiling since non-azeotropic mixtures have the temperature glide (i.e. non-isothermal phase transition). The experimental results at boiling of non-azeotropic mixtures in horizontal smooth steel and copper pipes have been selected for the theoretical analysis. The experimental data for the nucleate boiling were compared to calculations on various theoretical dependences. The calculated heat transfer coefficient is proposed by Gogonin’s dependence (2006). The mentioned dependence taking into account the influence of physical properties of a wall and its roughness on a heat exchange coefficient, results in the best coincidence to experimental data.