Mass Evaporation Rate Research Articles

Three approaches to modelling heating and evaporation of monocomponent droplets

Three approaches to modelling the heating and evaporation of monocomponent droplets are compared. Firstly, the heat rate supplied to the droplets to raise their internal energy is calculated based on the observation that steady-state equations for heat and mass balance in the gas phase should lead to the same droplet evaporation rates. The direct calculation of the above-mentioned heat rate is used in the second approach; the value of this rate is then used for the estimation of the droplet evaporation rate using the Spalding heat transfer number. In the third approach, the same algorithm as in the second approach is used to calculate the heat rate but the mass evaporation rate in this approach is inferred from the coupled solution to the momentum, mass and energy conservation equations in the gas phase; the gas mixture density in this approach depends on temperature. The predictions of the numerical algorithms for these approaches are compared with experimentally observed time dependencies of the rates of change of radii and average temperatures of n-decane droplets at initial temperatures and radii equal to 300 K and 0.85 mm, respectively, placed in a gas at temperatures 500 K and 760 K. It is shown that the algorithm for the third approach predicts values which are close to the experimental data.

Combined effect of grooves and nanoflower structured Co3O4 coating on bamboo wood for highly efficient solar steam generation at indoor and outdoor conditions.

Currently, interfacial solar steam generation (ISSG) in desalinating water has become very popular for obtaining purified water from polluted water. However, finding an efficient evaporator with low cost is a challenging task for researchers. In this work, we introduce natural bamboo wood (BW) that acts as an interfacial evaporator for obtaining purified water. Four different wood evaporators namely, flat wood (BW-FW), two-cut grooved wood (BW-2G), four-cut grooved wood (BW-4G), and four-cut grooved with Co3O4-coated wood (BW-4G/Co3O4) are used to study the mass loss (ML), evaporation rate (ER), and evaporation efficiency (EY). From the observations, BW-4G/Co3O4 gives an admirable ML, ER, and EY of 4.4 g, 3.366 kg m-2 h-1, and 91.34% under 1 sun illumination for 60 min. Also, the BW-4G/Co3O4 evaporator is kept under natural sun illumination. It achieves 17.8 g of ML, 1.92 kg m-2 h-1 of ER, and 76% of EY respectively under 604.762 W/m2 solar illumination for 8 h. The reasons for the observed results are as follows: (i) the presence of grooves increases the exposing area for solar illuminations, (ii) super hydrophilicity nature of wood gives continuous replenishment of water from the bottom to the evaporative surface, (iii) the excellent salt rejection property of wood aids in continuous water transportation without salt accumulations. As a result of the condensed seawater samples, the ion concentrations (zinc, magnesium, cadmium, lead, copper, and sodium) come under WHO standards. Consequently, it gives better dye water separation from polluted water.

Analytic solutions of heat and mass transfer in flat heat pipes with porous wicks

Flat heat pipes have been used in cooling computer chips. However, previous models impose heat rate through the pipe as an input parameter, preventing optimization of heat transfer. We consider a horizontal flat heat pipe with an idealized porous wick on either one or both walls. A constant temperature difference is imposed across the two ends of the pipe, and we seek a steady-state solution. The pores in the wick are straight circular capillaries running along and across the wick, and are filled with a partially-wetting liquid. Its vapor fills the center region of the pipe and is connected to the liquid through circular pore openings on the wick surface. At the hot end, the liquid evaporates from the pore openings into vapor, which moves to the cold end where it condenses and the condensate flows in the wick to the hot end to complete a cycle. The mass evaporation rate at each pore opening on the wick surface is found from evaporation kinetics. This pore-level result is incorporated into pipe-level mass, momentum, and energy balances. The mass evaporation rate is found to depend only on the pipe temperature and is essentially independent of the vapor pressure. Consequently, the pipe behaves like a fin with evaporative cooling instead of convective cooling. Thus, the analytic fin solution holds for the pipe temperature and contains only one dimensionless number S (S2 is the ratio of evaporative to conductive heat rate through the pipe). It is observed that in heat pipes, S≫1 and thermal energy is chiefly transferred by vapor flow. Analytic solutions are subsequently found for the evaporation rate, the heat rate through the pipe, and the liquid and vapor flows along the pipe. Our idealized-wick parameters are converted to the porosity and permeability of a porous medium, so that we can compare directly with two published flat heat-pipe experiments. We analyze the effects of pipe length and wick thickness on the heat rate through the pipe, and provide guides for future design of flat heat pipes.

Vapor mixing in turbulent vaporizing flows

Scalar mixing and evaporation processes are analyzed in a compressible two-phase homogeneous and isotropic turbulence configuration. To this end, the fully compressible Navier–Stokes equations are solved using a pressure-based method and a mass-conservative interface capturing method (CLSVOF). Temperature and vapor mass fraction transport equations are coupled with the momentum equation via the evaporation rate: i.e. heat and mass transfer has an effect on the flow dynamic through the generation of a Stefan flow at the interface. In this formalism, a pressure equation is developed to include the acoustic, thermal dilatation and compressibility effects. Moreover, the method can consider several gas structures in the same domain, each with independent temperature, density, and thermodynamic pressure. The latter is important to simulate atomization, where interaction among the liquid structures (such as breakup or coalescence) can generate multiple gas inclusions. This work is one of the first to describe with high fidelity the vaporization and turbulent mixing occurring in dense two-phase flows.A statistical analysis of the vapor mass fraction field is performed. The obtained results reveal the influence of the non-homogeneous scalar source at the interface, which depend directly on the local interface temperature, on the PDF shape. Under these conditions, the vapor mass fraction PDF deviates from the Gaussian and beta PDF shapes, frequently used for turbulent combustion modeling. Furthermore, access to the local surface averaged vapor mass fraction and evaporation rate at the interface allows a statistical analysis of these variables. Results show a large dispersion of both quantities, especially at the early times of the simulations, which contradict the usual assumption of a constant vapor mass fraction (or vaporization rate) at the interface used in the literature in standard vaporization models. Finally, the influence of the mean interface curvature on the evaporation rate is quantified and discussed. Large evaporation rate are present when the interface is convex (positive mean curvature). On the contrary, local saturation zones are present near concave interface (negative mean curvature), reducing the evaporation rate magnitude.

Using the screening layer of granulated foam glass to reduce the evaporation of hydrocarbon liquids

Introduction. The open surface of evaporation of hydrocarbon liquids during their storage in tanks (reservoirs) and in case of emergency spills are the fire hazards characterized by the mass rate of evaporation. The main way to reduce the fire hazard of hydrocarbon liquids is to isolate the evaporation surface of hydrocarbon liquids using various coatings, such as pontoons or floating roofs in tanks (reservoirs), and in case of emergency spills air-filled foam can be used, etc. An effective way to reduce the evaporation of hydrocarbon liquids is to isolate the evaporation surface using light slightly hygroscopic granular materials capable of being retained on the liquid surface by the Archimedean force. The authors address the analytical-experimental evaluation of a decrease in the mass rate of evaporation of hydrocarbon liquids when a layer of granulated foam glass shields the spill surface.Calculation methodology and results. A mathematical model has been developed to describe a reduction in the evaporation rate of hydrocarbon liquids through a “dry” layer of granulated foam glass, similar to the Bouguer – Lambert – Beer law. A method of experimental evaluation of the mass evaporation rate of hydrocarbon liquids through a shielding layer of granulated foam glass of different height has been developed. Screening coefficients for a number of hydrocarbon liquids and the averaged screening coefficient were identified using the results of an experimental research into parameters of evaporation of flammable liquids (acetone, gasoline AI-92, hexane, ethanol, kerosene, diesel fuel) through a “dry” layer of granulated foam glass of the Termoisol brand (fraction 5–7 mm) obtained using the methodology developed by the authors. Dependences between the rates of liquid evaporation through different thicknesses of a “dry” layer of granulated foam glass on the pressure of saturated vapours have been established. The area height, limited by the bottom concentration limit of the vapour flame, spreading during the evaporation of tested liquids from the free surface that may also have a shielding layer of Termoizol granulated foam glass is estimated analytically and experimentally.Conclusions. The developed mathematical model and the method of experimental estimation of the mass evaporation rate of hydrocarbon liquids allows to identify the evaporation rate of hydrocarbon liquids of different classes, and it can be used to study the parameters of evaporation shielded by materials having different granulo metric compositions.

Simulation investigation on a novel open-loop air cycle heat pump drying system

Different from conventional drying technology, the novel technology of an air cycle heat pump drying (ACHPD) system, using air as its working medium, is proposed to solve the problems of low energy efficiency, HCFC refrigerant use, and so on. A mathematical simulation model is constructed to evaluate system performance under various working conditions, and its verification via experimental results from a constructed test bench produced errors of temperature within ±1.6%, of drying rate within ±0.01%, and of system power within ±7%. Compared with a conventional electric heater drying (EHD) system, the energy-saving rate of the ACHPD system reaches about 15–27% when the mass evaporation rate increases from 0.75 kg h−1 to 3.45 kg h−1. Under set working conditions, an increase of inlet air flow rate (150–400 kg h−1) improved the dehumidification energy efficiency ratio (MER) by about 1%. However, the increase of inlet air temperature (10–40 °C) and relative humidity (30–80%) reduced MER by about 7% and 21% respectively. The efficiency improvements of heat exchanger (0.3–0.8) can improve the energy efficiency of system by 20%; however, the efficiency improvements of expander (0.55–0.8) and compressor (0.4–0.9) can deteriorate the energy efficiency of system by 17% and 36% respectively. These results would provide new technical references for the application of heat pump technology in drying field from a different perspective.

Lens Evaporation on Immiscible Liquid Surface with an Interfacial Cooling Effect.

A theoretical heat and mass transfer model of volatile liquid lens evaporation on the surface of an immiscible liquid substrate is established in toroidal coordinates. According to the coupled boundary conditions of heat and mass transfer at the lens surface as well as the interfacial cooling effect, the analytical solutions of the temperature field inside the lens and the vapor concentration field around the lens are derived for the first time. Compared with the isothermal model, the change of contact radius calculated by the present model agrees well with the experimental data, especially when the liquid substrate reaches a relatively high temperature. It also reveals that the temperature distribution inside the lens is not uniform, which is similar to the sessile droplet evaporation on a solid substrate surface. In addition, the excess temperature, heat flux, and evaporation flux of the lens–air interface increase monotonically from the lens center to the contact line. Finally, the influences of density ratio and evaporative cooling number E0 on lens mass evaporation rate are analyzed, which shows that the lens mass evaporation rate decreases with increasing density ratio and evaporative cooling number.

Numerical simulation and parameterization of the heating and evaporation of a titanium (IV) isopropoxide/p-xylene precursor/solvent droplet in hot convective air

Flame spray pyrolysis (FSP) is an excellent method to produce metal-oxide powders in the nano-size range. In this framework, the heating and evaporation of precursor solutions in hot oxidizing environments is investigated. A single spherically symmetric precursor/solvent droplets of titanium (IV) isopropoxide (TTIP) – Ti[OCH(CH3)2]4 in p-xylene – C6H4(CH3)2 at room temperature in convective hot air at atmospheric pressure is considered. Both variable liquid and gas thermophysical properties are incorporated and the non-random two-liquid (NRTL) model is used to describe the real behavior of the mixture. The bi-component droplet interior is not physically resolved and time-dependence is considered through the distillation-limit model for droplet heating and the rapid-mixing model accounts for droplet vaporization. A parameter study of the heating and evaporation characteristics of the single precursor/solvent droplet on the initial droplet size, the initial TTIP mass fraction in the droplet, the ambient air temperature, and the relative gas and droplet velocity is performed and discussed. The results are parameterized and tabulated in terms of polynomial fits of the individual mass evaporation rates of the components, the droplet surface temperature, and the normalized droplet surface area. A computer code in the programming language C is provided that can be incorporated into more complex simulations of FSP.

Morphology Evolution of a Volatile Liquid Lens on Another Immiscible Liquid Surface Induced by Evaporation.

A theoretical model was established to predict the morphology evolution of a volatile liquid lens evaporation on another immiscible liquid substrate surface. The theoretical model considered the dynamic process of contact line motion. On the basis of the boundary conditions established at the contact line, the morphology change of the liquid lens was calculated by numerically solving the Young-Laplace differential equations for the three interfaces. The mass evaporation rate was calculated by the diffusion-controlled evaporation model. Then, an experimental system was established to record the process of a hexane lens evaporation on the surface of an ionic liquid with a depth of 4 mm. The calculated hexane lens radius variation matches well with the experimental measurements, which shows the rationality of the present model. The calculated results show that the evaporation pattern of the liquid lens follows the constant contact-angle evaporation mode for ∼70% of the lifetime. During the later stage of evaporation, the contact angle decreases, accompanied by contraction of the contact line, which is similar to the mixed evaporation mode in the later stage of sessile droplet evaporation on a solid substrate surface. Furthermore, the influences of the initial hexane lens volume and the ionic liquid temperature on the dynamic contact angle were theoretically summarized. This study helps to provide in-depth insights into regulating the lens evaporation process on another immiscible liquid substrate surface to control the particle deposition mode.

Numerical simulation of flow boiling heat transfer and pressure drop in a corrugated plate heat exchanger at low mass flux and vapor quality conditions

This article reports on a numerical study conducted to predict the flow boiling dynamics, heat and mass transfer, and pressure drop in corrugated plate heat exchangers. The conservation equations are discretized in the context of the finite volume method and solved using the mixture multiphase flow model. The Semi Mechanistic Wall boiling model, based on Chen’s method, is used to calculate the wall heat flux. Moreover, Lee’s model is adopted to compute the evaporation/condensation rate. Water is used as the working fluid and solutions are generated at low mass flux and vapor content for subcooled and saturated liquid water at the inlet. An experimental setup is developed, and measurements are performed to validate the numerical solution. The model shows good agreement with experimental data and with values obtained from available correlations for the two-phase heat transfer coefficient and pressure drop. Results indicate an increase in the heat transfer coefficient when the mass flux is increased, and wall and inlet flow temperatures are decreased. Further, the drop in pressure increases with an increase in the mass flux, wall temperature, and vapor quality. The flow boiling heat transfer is found to be in the nucleate boiling regime. Additional new insights on the complex flow boiling process are reported by utilizing contour plots of the mass evaporation rate, vapor fractions, and velocity vector fields.

Study on influencing factors of atmospheric environmental risk of bulk liquid chemical leakage at wharf

In this study, 10% pipe diameter leakage was taken as a typical accident of liquid chemical leakage in bulk at wharf. The leakage rate and evaporation rate of 8 common chemicals were calculated using Bernoulli equation of fluid mechanics and mass evaporation rate. The evaporation rate and the concentration of toxic end point were compared. SLAB model was adopted to analyze the atmospheric environmental risk of chemical leakage under typical accident conditions. According to the calculation results, the atmospheric environmental risk under the scenario of 10% pipe diameter leakage accident was acceptable.

Experimental Study on Evaporation Characteristics of Light Cycle Oil Droplet under Various Ambient Conditions

The authors conducted droplet evaporation experiments of light cycle oil (LCO) at various ambient temperatures and pressures. Five kinds of LCO and three kinds of arranged fuels were used. We investigated the evaporation characteristics of LCO and the relationships between the evaporation characteristics and the cetane index. In addition to that, a surrogate fuel composed of four chemical species, which can simulate the droplet evaporation characteristics of LCO, was suggested. Experimental results show that the differences in droplet lifetime between fuel species become larger with decreasing ambient temperature. This is because the low volatile component made the evaporation rate outstandingly slow at a low ambient temperature. It was found that the relationship between droplet lifetime and the late-stage distillation temperature becomes stronger at low ambient temperature and high ambient pressure. By an analysis employing the properties of chemical species in LCO surrogate fuel, it is clarified that the mass evaporation rate becomes smaller than the internal diffusion, which is the condition similar to that in the distillation test. Finally, the relationship between the droplet lifetime and the cetane index was investigated. It can be concluded that the droplet lifetime is independent of the cetane index under all conditions tested in this study. The experimental data obtained by this research can be utilized for the validation of multicomponent fuel droplet evaporation models in the future.

Molecular dynamics simulation of sub/supercritical evaporation with n-butanol/n-heptane blended fuel

Sub/supercritical evaporations of single-component fuels have been developed well so far. In the last decade, dual fuels, even multiple fuels have received more attention. However, sub/supercritical evaporations of dual fuels are more complicated than that of single-component fuels, as dual fuels have uncertain critical points, and single-component fuels have exact critical points. Therefore, in this study, we focused on the functional relationship between the critical temperatures and the blending ratios (n-heptane to n-butanol) of the n-butanol/n-heptane blends by molecular dynamics simulations. A liquid film of the blends was constructed in nitrogen environment. The sub/supercritical evaporations processes of the blends were simulated in different ambient temperatures and pressures and in different blending ratios of the blends. The density profile, surface temperature, evaporation mass ratio and evaporation rate were estimated and compared under sub/supercritical states. The critical temperature of the blends was determined by the surface temperature and the surface tension. Results indicate that under ambient low supercritical condition, a transition from subcritical to supercritical state does not happen in the evaporation process of blends. The evaporation mass ratio is not always equal to the blending ratio as the way used in current evaporation model, but a function over time. A fitting formula for calculating the critical temperatures of the blends is provided.

Влияние концентрации капель воды в аэрозольном облаке на скорости их испарения

The results of experimental studies of the integral characteristics of the water droplets evaporation in aerosol cloud are presented. Variable parameters: initial radius of droplets 0.1–0.25 mm, temperature of combustion products 573–873 K, concentration of water droplets 0.03–0.1 l /m3. The ranges of variation of the water mass evaporation rate are determined depending on the concentration of droplets in the aerosol cloud and their initial sizes. Approximation expressions for the established dependencies are obtained. For the first time, an approach was proposed to determine the evaporation rate of aerosol droplets taking into account the known/calculated values of the evaporation rate of a single drop.

Experimental study of coupled heat and mass transfer phenomena between air and desiccant in a solar assisted thermal liquid desiccant system

Liquid desiccant dehumidification is a promising energy-extensive process for air dehumidification, which can easily be driven by any waste or renewable heat sources. In the current study, a hybrid method is proposed by combining the solar evacuated tube collectors as a regeneration source to drive liquid desiccant system in a close-loop. Subsequently, an experimental setup has been fabricated to assess the performance of the overall system using a novel desiccant mixture. The overall energy balance between the ambient air and the liquid desiccant was also studied. Effects of independent parameters such as solution to airflow rate, solution concentration and temperature on the dehumidifier-regenerator performance parameters such as latent heat ratio, condensation rate, desiccant mass fraction index, evaporation rate, latent and enthalpy effectiveness were analyzed. The result of present investigation showed that high solution to airflow (S/A) ratio enhanced the dehumidification and low S/A ratio enhanced the liquid desiccant regeneration rate. The maximum latent heat ratio for the dehumidifier at the design condition was 0.92, and the thermal coefficient of performance of the system was found as 1.1. The airside pressure drop in the dehumidifier/regenerator was also estimated at different flow rates of desiccant. Further, adaptive neuro-fuzzy inference system (ANFIS) prediction models are developed to predict the system performance as a function of system-independent parameters. The model results exhibited a good agreement with the experimental outcomes. The latent heat ratio and evaporation rate are predicted within a mean absolute percentage error (MAPE) of 2.7% and 2.3%, respectively.

Effects of microwave heating on quality attributes of pineapple juice

The effects of microwave heating on the quality attributes of pineapple juice were investigated in this study. The experiments were conducted based on the central composite design of response surface methodology to analyze the relationship of mass evaporation rate at different initial masses of pineapple juice (100–250 g) on the physiochemical properties of pineapple juice. The results showed to have significant parabolic increment, except the sugar content of pineapple juice behaved linearly with the mass evaporation rate. The diffusion of moisture was well explained by the Fick's second law. The modified Arrhenius model was used to estimate the activation energy (1.02–3.20 kW/kg). The drying model of Henderson and Pabis could fit well into the kinetic behavior of concentrating pineapple juice. The change of quality attributes, particularly browning effect and proteolytic activity could be minimized using low initial mass of juice and heated at short duration for high evaporation rate. Practical applications Microwave oven has been widely used for food heating and juice concentrating because of its convenience in fast heating. Juice is concentrated to minimize storage and transportation cost. However, overheating could change quality attributes of pineapple juice, especially the browning effect and proteolytic activity, as well as the ratio of sugar-to-acid affecting pineapple taste. The findings revealed that small volume and short heating duration could reduce the change of quality attributes, even at high evaporate rate. The parameters vary according to the water and sugar content which affect the heat capacity of juice. Large volume limits moisture diffusion as explained by Fick's second law. The monolayer drying model of Henderson and Pabis could fit to the concentrating process satisfactory. Microwave heating could be used to concentrate pineapple juice with minimal effects on quality attributes, if small volume at shorter time was used in the process.

Modeling and Simulation of Single Ethanol/Water Droplet Evaporation in Dry and Humid Air

ABSTRACT The modeling and simulation of the heating and evaporation of a spherically symmetric single, bi-component ethanol/water droplet in convective air is studied which allows for an improved understanding of the different heating and evaporation characteristics of the two components of the bi-component droplet. The concentration inside the droplet interior is considered to be uniform and the temperature is modeled with the distillation-limit model. The Abramzon–Sirignano model is used for describing the convective droplet heating and evaporation, and Brenn’s extension for multicomponent droplets is used for modeling the ethanol/water droplet. The UNIFAC method is employed to describe the activity coefficients to account for the non-ideal behavior of the ethanol/water mixture. The numerical results corresponding to non-ideal and ideal mixing are compared with experimental data from the literature. Moreover, a parameter study of the ethanol/water droplet evaporation in both dry and humid air for combustion conditions is performed where both the initial gas temperature and velocity and the initial droplet size and composition are varied. The evolution of the droplet surface area, the mass fractions, the mass evaporation rate, and the surface temperature are analyzed for the different conditions. In general, the UNIFAC method initially leads to a somewhat faster evaporation rate and slows down after the higher volatile component has almost completely evaporated; however, its effect on the droplet lifetime is small. Humidity strongly affects the bi-component droplet heating and evaporation because of the condensation of water on the droplet surface which retards the water evaporation but enhances the initial ethanol evaporation for high relative humidity. Also, in humid conditions, the droplet lifetime is strongly increased compared to evaporation in dry air. The parametric dependencies of droplet lifetime and the evaporation characteristics of the bi-component ethanol/water droplet evaporation in both dry and humid convective air may be used in more complex simulations of non-reacting and reacting spray flows.

Will Polyethylene furanoate (PEF) challenge Polyethylene terephthalate (PET)?

The preparation and characterization of SiN thin films using an aerosol-type liquid precursor delivery system (LDS) for application as a water-vapor permeation barrier layer in organic electronic devices is described. The proposed LDS consisted of three major parts: 1) an aerosol generator that transformed the liquid precursor to an aerosol molecule using a piezoelectric ultrasonic vibrator, 2) a vaporizer that transformed the injected aerosol molecules to a vapor state, and 3) a vapor storage canister. The instant evaporation fraction and maximum evaporation mass rate were measured to be 98.3% and 2.55 g/min, respectively. The temperature in the vaporizer was stable, showing a 1 °C variation from the set temperature. As the LDS temperature increased, the evaporation mass rate also increased from 0.035 to 2.55 g/min. A 30 nm thick SiN layer was prepared to evaluate the performance of the LDS, which was attached to a cyclic chemical vapor deposition system. The prepared SiN layer had a smooth surface with no defects or pinholes; the root mean square surface roughness of the prepared SiN film was measured to be 0.185 nm, which is adequate to be used as encapsulation layers in organic electronic devices. The water vapor transmission rate through the 30 nm thick SiN layer was calculated to be 1.31 × 10−6 g/m2/day by Ca-degradation test. The results indicated that the produced films meets the requirement for application as an encapsulation layer to protect the organic layer in organic electronic devices from water vapor penetration, especially in organic light-emitting diodes.

The effect of the interface length on the evaporation rate of a horizontal liquid layer under a gas flow

The dynamics of evaporation from the confined surface of a horizontal layer of liquid (ethanol) under the action of a gas (air) flow has been experimentally studied. The influence of the longitudinal dimension of the interface (0.01–0.03 m) on the specific mass rate of evaporation was studied. It was found that the specific mass evaporation rate decreases with an increase in the interface length due to a decrease in the vapor concentration gradient in the boundary layer.

Numerical simulation of supersonic flow past a plate with surface material sublimation

A method of direct numerical simulation and a method of solving the boundary-layer equations were applied to parameters of a supersonic boundary layer for a flow past a flat plate (Mach number M = 2) for the case of a plate coated with a sublimation material. The sublimating material is naphthalene (C10 H8). Comparison of results from these two approaches — numerical simulation and solution of a boundary layer under the assumption on the local self-similarity — demonstrated a satisfactory agreement between them. Calculations demonstrated that a higher surface temperature produces a higher mass rate of evaporation. Meanwhile, the total heat flux to the solid wall decreases and the wall temperature is lower than for the case of zero sublimation. Since the molecular mass of naphthalene is by several times higher than the molecular mass of air and due to evaporation-induced wall cooling, we observe a higher density of the mixture of air with the sublimating substance vapor near the wall. This may facilitate a higher stability of the supersonic boundary layer and delays the flow transition to the turbulent state.