Search

Steam submerged jet condensation is a direct contact condensation widely used in many industries. However, this process may cause damage to related equipment due to pressure oscillation, especially at low steam mass flux. This study synchronously investigated the steam–water interface fluctuation of unstable condensation jet and its corresponding pressure oscillation through a horizontal pipe at low steam mass flux to research the condensation oscillation mechanism. Three typical flow patterns, namely, Chugging, hemispherical bubble oscillation (HBO), and encapsulating bubble oscillation (EBO), were distinguished based on the dynamic behavior of steam–water interface and oscillation pressure characteristics. Only the dynamic pressure in EBO region was periodic among the three flow patterns. In the EBO region, the pressure oscillation frequency increased with the increase of steam mass flux and decreased with the increase of water temperature. A flow pattern regime map for horizontal jet condensation related to steam mass flux and water temperature was presented based on experiments. Moreover, the influence of pipe diameters on low steam mass flux was analyzed. For the flow pattern regime map at low steam mass flux, the critical steam mass fluxes showed an inverse relationship with pipe diameter. An empirical criterion was introduced to determine the flow regime map at low steam mass flux.

Transient numerical study was performed to investigate the characteristics of interphase heat transfer in unstable steam jet under different operating conditions. Bubble radius change rate, interfacial heat transfer coefficient and overall condensation mass flux reached their maximum values during the bubble necking stage. The maximum peak value of interfacial heat transfer coefficient and bubble radius change rate decreased with the decrease of inlet pressure differential and water subcooling. The peak values of interfacial heat transfer coefficient and internal velocity were found in the bubble neck region. The effect of interphase heat transfer on bubble growth and necking stages was analyzed on the basis of overall force balance. Momentum force played a major role during the bubble growth stage, and the condensation force had a dominant effect on bubble necking stage. Condensation force first decreased and reached its minimum value during bubble rapid necking stage. Subsequently, the condensation force rapidly increased and promoted the movement of bubble necking. Moreover, the condensation force curves under different conditions had the same change law.

Interfacial fluctuation and turbulent entrainment in the vapour-liquid mixing layer have great influence on heat and mass transfer in direct contact condensation. In this study, an ingenious experimental design was adopted to explore the characteristic microstructure at the steam-water interface of a water-submerged steam jet. Firstly, the periodic evolution process of large-scale two-phase coherent entrainment vortexes in the upper and lower steam-water turbulent mixing layers was captured. This process was divided into four stages: vortex formation, vortex growth, vortex pairing and vortex shedding. At the vortex growth stage, the central axial displacement of vortex was approximately linear with time, whereas the variation of vortex scale was nonlinear with time. Secondly, the periodic fluctuation of jet penetration length was caused by the pairing and shedding of periodic vortexes. Finally, the vortex formation process and distribution law of mixing layer thickness were analysed. The average scale of vortex blob at the pairing position was predicted and showed good agreement with the experimental data.

Submerged steam jet condensation is widely applied in various fields because of its high heat transfer efficiency. In this paper, sonic steam jet condensation through a double-hole nozzle was numerically researched. First, the effect of L/D (pitch to diameter) on steam plumes was investigated. When L/D increased from 1.2 to 2.5, two steam plumes transformed from merging into one steam plume to being independent. Besides, thermal hydraulic parameters along radial directions were analyzed, revealing the existence of expansion and compression waves. Radial distributions of steam volume fraction, temperature and velocity were all largely symmetric about nozzle centerline and there all existed minimum values at nozzle centerline position. Finally, the effect of L/D on thermal hydraulic parameters of nozzle centerline was obtained. There existed peak values for steam volume fraction, temperature and velocity of nozzle centerline at one position. As L/D increased, the peak value decreased and its position moved downstream.

The driving force and the energy conversion between condensation, driving kinetic energy of water and pressure oscillation for steam jet have been experimentally investigated in the steam pressure range of 0.2–0.5 MPa and water temperature range of 293–323 K. The axial velocity of the water decreases with the increasing axial distance from the end of the steam plume, and increases with the increasing steam pressure. The driving force are in the range of 1–20 N under different steam pressure and water temperature in the experimental conditions. The driving power increases with the increasing steam pressure. In the stable condensation region, the pressure oscillation power increases with the increasing steam pressure, and decreases with the increasing water temperatures. More than 99% of the energies input are transferred to heat energy of water, and little energy is converted to the driving energy and oscillation energy of the water. The condensation plays a leading role in the energy conversion for steam jet condensation.

Condensation induced water hammer (hereafter, CIWH) phenomenon is widely observed in various industrial operations, causing severe damage to related equipment and personal safety. This study investigated the CIWH regime map and the oscillation characteristics of periodic CIWH under different pipe lengths when the steam was discharged into a water tank through a horizontal pipe. First, the CIWH regime maps were obtained under different pipe lengths, with distinct regimes of periodic CIWH and non-periodic CIWH. A criterion was proposed to predict the transitions from periodic to non-periodic CIWH. It was found that the occurrence frequency of periodic CIWH decreased with the increase in the pipe length. An empirical correlation of Strouhal number, non-dimensionalized occurrence frequency, was developed to predict the occurrence frequency. The correlation could reproduce more than 95 % of the experimental data with the error of -20.2 % to 23.7 %. The pressure oscillation intensity of periodic CIWH was analyzed. The oscillation intensity increased when the pipe length and steam mass flux increased, whereas it increased first and then decreased when pool temperature increased. Finally, the occurrence position of periodic CIWH was found to be nearly constant under the same test condition. The position moved downstream of the steam when the pipe length and Froude number increased, and Jakob number decreased. The average occurrence position was correlated with the error of -17.1 % to 18.4 %.

Three-dimensional steady simulation was performed to investigate the influence of non-condensable gas on stable condensation jet. Condensation model concerning non-condensable gas was inserted into Ansys to simulate the process of condensation with non-condensable gas. Water, steam and non-condensable gas were chosen as the three phases, and mixture multiphase model was employed. The contour of steam and axial temperature distribution were compared between numerical and experimental result, and good agreements were obtained. Then the effect of non-condensable gas on the contours of steam and air, axial parameters distributions such as velocity, temperature and pressure etc, were investigated as the void fraction of non-condensable gas ranges from 0 to 7%. As the amount of non-condensable gas increases, the penetrating length of steam plume is longer and longer, and the thermodynamic parameters along axial direction showed regular changes at the same time. Besides, it was found that non-condensable gas gathered at the end of steam plume, reaching the maximum void fraction.

Three-dimensional steady method was employed to simulate the process of stable supersonic steam jet condensed into a water pool. A thermal equilibrium phase change model was inserted into Ansys as a user defined function to simulate the condensation process. To testify the correctness of simulation model, steam plume and radial temperature distribution were compared between experiment and simulation. Then four kinds of steam plume shapes, including contraction, expansion-contraction, double-expansion-contraction, and contraction-expansion-contraction shapes, were observed from numerical results as experimental results indicated. Combined with the corresponding contours of steam void fraction, the distribution of axial thermodynamic parameters, such as pressure, temperature and velocity were analyzed for each kind of steam plume. The theory of expansion and compression wave was employed to explain the flow mechanism in each kind of steam plume.

The pressure oscillations for steam jet in stable condensation region are investigated experimentally. Steam at pressure 0.2–0.6 MPa is injected into subcooled water at one atmosphere pressure with steam mass flux ranging from 298 to 865 kg/(m 2 s), with water subcooling from 70 to 40 K. The steam plume shapes have been recorded and are compared with the pressure oscillation. The pressure oscillation for steam jet in stable condensation region is caused by the oscillation of steam plume length. When the steam plume length is the longest, the pressure oscillation has negative peak value and vice versa. Based on the experimental data and the change of steam plume shapes, a new phenomenological model of pressure oscillation is developed. The model also provides a method to obtain the steam plume length using the pressure oscillation. The prediction errors of the peak pressure oscillation are within ±30% of experimental values.

For stable sonic steam jet, conical and ellipsoidal steam plumes were observed by many researchers. Restricted by experimental method, the difference in flow and heat transfer characteristic between conical and ellipsoidal steam plumes was still unclear. To reveal the difference between the two kinds of steam plumes, three-dimensional steady numerical simulations were carried out with Eulerian multiphase model, and a thermal equilibrium phase change model was inserted into Fluent as a user defined function (UDF) to investigate the condensation phenomenon. The CFD results were compared with experimental results to testify the correctness of simulation, and good agreement was observed. Then steam pressure was varied to study its effect on the process of condensation jet. Conical and ellipsoidal steam plumes were obtained under different operating conditions. For conical steam plume, it is compressed near nozzle exit along radial direction, and the pressure in steam plume is larger than ambient pressure. However, when it comes to ellipsoidal steam plume, it expands near the nozzle exit along radial direction, when steam plume expands to the maximum extend, the pressure in steam plume is reaching the bottom, almost the same as ambient pressure. Besides, the influence of flow characteristic of steam in plume on axial temperature and steam plume shape was analyzed. When steam in plume reaches supersonic, the shape of steam plume shows ellipsoidal shape, and there is a peak along axial temperature distribution. Otherwise, it presents conical shape and axial temperature decays to ambient water temperature monotonously.

In view of the importance of the condensation-induced water hammer in various engineering fields, this study performed an analytical modeling and numerical simulation to obtain the map of the onset of the condensation-induced water hammer. Two linear boundaries were experimentally observed for the transitions between no condensation-induced water hammer and non-periodic condensation-induced water hammer and between non-periodic condensation-induced water hammer and periodic condensation-induced water hammer. The analytical modeling based on the energy balance equation was conducted to derive the onset of the condensation-induced water hammer. The analytical model suggested that the map of the onset of the condensation-induced water hammer could be displayed by two essential non-dimensional parameters, such as modified Jakob number and Froude number. The model indicated that the slope of the boundary of the onset of the condensation-induced water hammer was the product of modified Stanton number, non-dimensional interfacial area concentration, and non-dimensional temperature difference. The model could predict the boundaries between no condensation-induced water hammer and non-periodic condensation-induced water hammer and between non-periodic condensation-induced water hammer and periodic condensation-induced water hammer satisfactorily. The one-dimensional nuclear thermal-hydraulic system analysis code, RELAP5, was used for simulating the onset of the condensation-induced water hammer. The obtained boundary corresponded to the experimentally obtained boundary between non-periodic condensation-induced water hammer and periodic condensation-induced water hammer.

Steam submerged jet condensation has been widely used in nuclear fission and fusion industries, chemical engineering and aerospace industry. Steam cavity and its feature in stable condensation regime play important roles since they are closely related to heat transfer and condensation oscillation. Due to the different definitions of steam cavity, the properties of steam cavity, such as shapes, void fraction distribution and two-phase mixing regions, are different. The mechanism of steam cavity forming and development remains unclear. The existing analytical models and empirical correlations for steam jet length are verified with experimental data. Most correlations based on Kerney's model can predict the experimental jet lengths when water is stagnant and steam mass flux lower than 800 kg m−2·s−1. For other conditions, significant discrepancy is found among existing experimental jet lengths, and no model can predict them well. The heat transfer coefficient calculation models based on steam jet length correlations fail to predict the experimental data, and no unified correlations or models can predict heat transfer coefficient well. The causes of prediction deviation for jet length and heat transfer coefficient are analyzed. The inconsistent tendency and nonunified saturated temperature cause the significant predicted deviation. Further efforts on analytical and experimental studies on steam jet length and heat transfer coefficient are encouraged in the future.

Submerged steam jet condensation is widely applied in the industry, and the condensation oscillation during the condensation process is highly related to the safe operation of devices. The first dominant frequency has been frequently studied; thus this study focuses on the characteristic of the second dominant frequency of supersonic steam condensation oscillation. Results show that the second dominant frequency is generated by the oscillation of the detached steam bubble. The frequency value of the supersonic steam is lower than that of the sonic steam, and increases with the design pressure ratio. Two different methods, namely, experimental correlation and theoretical calculation, are proposed to obtain the second dominant frequency. Moreover, its propagation characteristic is investigated under different operation conditions. An energy peak, which corresponds to the position where the steam bubble separates, always appears. The energy amplitude peaks at a low design pressure ratio when the steam mass flux is not larger than 600 kg·m −2 ·s −1 , and it peaks at a high design pressure ratio when the steam mass flux increases. A theoretical method is established to obtain the second dominant frequency energy distribution, and its effectiveness is verified against experimental results. Furthermore, owing to the barrier effect of steam plume, the upstream deviation is slightly higher than the downstream deviation.

Submerged steam jet condensation is widely applied in various fields because of its high heat transfer efficiency. Condensation oscillation is a major character of submerged steam turbulent jet, and it significantly affects the design and safe operation of industrial equipment. This study is designed to reveal the mechanism of the low-frequency pressure oscillation of steam turbulent jet condensation and determine its affected region. First, pressure oscillation signals with low frequency are discovered in the downstream flow field through oscillation frequency spectrogram and power analysis. The oscillation frequency is even lower than the first dominant frequency. Moreover, the critical positions, where the low-frequency pressure oscillation signals appear, move downstream gradually with radial distance and water temperature. However, these signals are little affected by the steam mass flux. Then, the regions with low-frequency pressure oscillation occurring are identified experimentally. The affected width of the low-frequency pressure oscillation is similar to the turbulent jet width. Turbulent jet theory and the experiment results collectively indicate that the low-frequency pressure oscillation is generated by turbulent jet vortexes in the jet wake region. Finally, the angular coefficients of the low-frequency affected width are obtained under different water temperatures. Angular coefficients, ranging from 0.2268 to 0.2887, decrease with water temperature under test conditions.

The effect of air with low mass fraction on the oscillation intensity and oscillation frequency of a submerged steam jet condensation is investigated under stable condensation region. With air mixing in steam, an obvious dynamic pressure peak appears along the jet direction. The intensity peak increases monotonously with the rise of steam mass flux and water temperature. Peak position moves downstream with the rise of air mass fraction. Moreover, when compared with that of pure steam jet, the oscillation intensity clearly decreases as air is mixed. However, when water temperature is lower than approximately 45 °C, oscillation intensity increases slightly with the rise of air mass fraction, and when water temperature is higher than 55 °C, the oscillation intensity decreases greatly with the rise of air mass fraction. Both the first and second dominant frequencies decrease with rise of air mass fraction. Finally, effect of air mass fractions on the oscillation power of the first and second dominant frequency bands shows similar trends. Under low water temperature, the mixed air has little effect on the oscillation power of both first and second frequency bands. However, when water temperature is high, the oscillation power of both first and second frequency bands appears an obvious peak when air mass fraction is about 1%. With further rise of air mass fraction, the oscillation power decreases gradually.

The condensation oscillation of submerged steam was investigated theoretically and experimentally at the condensation oscillation regime. It was found that pressure oscillation frequency was consistent with the bubble oscillating frequency and there was a quasi-steady stage when bubble diameters remained constant. A thermal-hydraulic model for the condensation oscillation regime was proposed based on potential flow theory, taking into account the effects of interface condensation and translatory flow. Theoretical derivations indicated that oscillation frequencies were mainly determined by bubble diameters and translatory velocity. A force balance model was applied to the calculation of bubble diameters at quasi-steady stage, and the oscillation frequencies were predicted with the calculated diameters. Theoretical analysis and experimental results turned out that oscillation frequencies at the condensation oscillation regime decreased with the increasing steam mass flux and pool temperature. The predicted frequencies corresponded to the experimental data well with the discrepancies of ±21.7%.

An experimental study was carried out on the pressure oscillation caused by direct contact condensation (DCC) of steam jet in water. The published researches on pressure oscillation caused by DCC were generally performed in large space pools. However, the condensation oscillation characteristics of steam jet in water flow in a confined space have not been fully understood yet. During this experiment, the steam and water were introduced into a confined channel at the same side. The dynamic pressure signals were measured without interfering the flow field. The behavior of the interface was captured by a high speed camera. The main inlet parameters, i.e. steam mass flux, water Reynolds number and water temperature were tested in the range of 150–600 kg/(m 2 s), 78,000–172,000 and 25–60 °C, respectively. The results indicated that flow patterns were determined by these three inlet parameters. According to the structure and behavior of the interface, the flow patterns under various test conditions could be divided to unstable and stable types. As flow patterns transformed from stable to unstable, the pressure oscillation intensity increased sharply. The dominant frequency for subsonic steam jet condensation oscillation in water flow was in the range of 168–1177 Hz. The frequency increased with the increase of water Reynolds number, but decreased with the increase of steam mass flux and water temperature. Moreover, a correlation for the dominant frequency was given as a function of the condensation driving potential, steam mass flux, Weber number and water Reynolds number. The predicted values agreed well with the present experimental values at the maximum deviation of ±20%.

Steam direct contact condensation in subcooled water is widely used in various industries. The steam-water interface shape is an essential parameter for direct contact condensation. An experimental study was carried out to investigate the flow patterns and interface shape of bubbling regime with a vertical upward steam jet. Steam mass flux and water temperature were 8.34–50.13 kg/(m2∙s) and 40–85°C, respectively. Three flow patterns such as chugging, smooth grown bubble, and rough grown bubble were found based on the dynamic behavior of steam-water interface. The bubble collapse frequency and the maximum bubble radius at the bubble growth stage were calculated. The bubble collapse frequency increased rapidly when the smooth grown bubble regime was transformed into the rough grown regime. When the water temperature was between 40-80°C, the maximum bubble radius initially increased, and then decreased with the increase of steam mass flux. A transition criterion from the smooth grown bubble regime to the rough grown bubble regime was given based on the theoretical analysis and experimental data.

Steam condensation-induced water hammer (CIWH) can cause great pressure oscillation, and the knowledge of CIWH is important to pipes and relevant equipment. In this work, an experiment was conducted to investigate the condensation process of entrapped bubbles for periodic CIWH and its pressure oscillation in a horizontal pipe. Results indicated that CIWH was caused by the condensation of entrapped bubbles, and the initial volume of entrapped bubbles of the periodic CIWH kept nearly unchanged when the test conditions were constant. The initial bubble volume increased with the increases in steam mass flux and water temperature. The pressure oscillation intensity of the CIWH increased with the increase in initial bubble volume but decreased with the increase in water temperature. Furthermore, the change rate of bubble volume gradually increased with the condensation of the entrapped bubbles. The final change rate of bubble volume increased with the increase in initial bubble volume but decreased with the increase in water temperature. Finally, a theoretical correlation, that is, a linear relationship between the pressure oscillation intensity and the final change rate of bubble volume, was proposed to calculate the pressure oscillation intensity of the CIWH. The predicted deviation ranged from −44% to 64%.

An experimental study was conducted to investigate the condensation regime and pressure oscillation characteristics of vertical upward steam jet condensation with low mass flux. Steam mass flux and water temperature were 8.34–16.71 kg/(m2·s) and 40–85 °C, respectively. Steam bubble behavior, pressure oscillation amplitude and frequency were recorded and analyzed. Four typical regimes were found, namely, chugging, detached oscillatory, detached cracked and secondary bubble impinged regimes. A bubble condensation region map was developed by considering the effects of steam mass flux and water temperature. The average amplitude of pressure oscillation initially increased, and then decreased as water temperature increased. It reached its maximum value when water temperature was approximately 60–65 °C, which was the transition temperature range from the chugging regime to the detached oscillatory regime. Meanwhile, the frequency of pressure oscillation was within the range of 12–28 Hz. These values were higher than those for a vertical downward steam jet with the same steam mass flux and water temperature. A dimensionless correlation was obtained to predict the Strouhal number of pressure oscillation frequency. The predicted values corresponded well with the experimental data. The deviation was within the range of –9.12% to +8.30%.

Submerged steam jet condensation is widely used in many industries. However, this process may cause damage to equipment due to pressure oscillation, especially at low steam mass flux. The dynamic process of steam bubble and different pressure oscillation types were investigated in this numerical study. Five typical stages were observed, which were bubble growth stage, bubble slow necking stage, bubble rapid necking stage, bubble detachment stage and secondary bubble oscillation stage. Two pressure oscillation types were found by the synchronization analysis of bubble pattern and pressure field. The mechanisms of condensation oscillation of unstable steam jet were revealed. As for the first type, two pressure peaks existed in the fluctuation process of secondary bubble volume. The higher pressure peak was generated when secondary bubble was oscillated to its minimum volume, and the other was generated when secondary bubble was collapsed. As for the second type, only one pressure peak existed and secondary bubble was quickly contracted without volume fluctuation. Pressure peak was generated when secondary bubble was quickly contracted to its minimum volume. Moreover, analyses of flow field pressure at different locations were carried out. Results indicated that the pressure fluctuation was mainly induced by the condensation oscillation of secondary bubble for both types. The trends of pressure at different locations were the same as that of secondary bubble internal pressure.

Condensation oscillation of steam jet is of high importance for industrial facility. In this study, the mechanism and propagation characteristic of the second dominant frequency is investigated. Firstly, the second dominant frequency is found under all the test conditions based on frequency spectrum. The second dominant frequency decreases with the rise of water temperature and steam mass flux. Then, the second dominant frequency is proved to be generated by the separated steam bubbles oscillation based on the bubble oscillation theory. And the theoretical oscillation frequency equation of separated steam bubble is used to predict the second dominant frequency, the predicted deviation ranges from −17% to 6%. Furthermore, the propagation characteristic of the second dominant frequency is investigated, and a theoretical propagation equation for the second dominant frequency is derived. Then, the axial and radial distribution characteristic of oscillation amplitude and energy of the second dominant frequency are analyzed and researched. In the downstream flow field and the radial direction, the propagation characteristic of steam bubble oscillation wave is well corresponding to the predicted results. However, in the upstream flow field, due to the effect of steam plume, the oscillation amplitude and energy of the second dominant frequency attenuate rapidly and the experimental data are much smaller than the predicted value.

Steam jet condensation is important in many industrial applications. In this work, the pressure oscillation and steam jet patterns during submerged jet condensation in quiescent water is investigated experimentally. Firstly, it is found that even at stable condensation region, the steam cavity length varies all the time and steam bubbles separate from the steam cavity periodically. With the variation of steam cavity length and separated bubble oscillation, condensation also undergoes oscillation. Along the axial direction, the pressure oscillation intensity increases first and then decreases gradually. There is an distinct pressure oscillation peak, and the peak position varies over a length-to-diameter ratio range of X / D = 2 to X / D = 7. The axial position of pressure oscillation peak corresponds to the end of steam cavity. Moreover, oscillation energy analysis shows that the oscillation energy generated by separated steam bubble is much higher than that generated by the steam cavity length variation. Finally, based on the relationship between the axial distribution of pressure oscillation and the steam cavity, a method is proposed to determine the maximum steam cavity length by measuring the pressure oscillation distributions. The predicted deviation is only in range of ±16% for the test conditions.

An experimental study was performed to investigate the direct contact condensation (DCC) of steam–air mixture in subcooled water flow in a rectangular channel. The main inlet parameters including steam mass flux, water mass flux and water temperature were tested at 150–550 kg/(m2 s), 6–14 × 103 kg/(m2 s) and 30 °C, respectively. The air mass fraction was in the range of 0%–2%. Four different flow patterns for pure steam in subcooled water flow were filmed by a high speed camera. The effect of air on these four flow patterns was investigated by introducing air into steam. The pressure and temperatures on the wall of channel were measured without destroying the flow field. The results indicated that with the present of air, the direct contact condensation was hindered, the interface area enlarged, the mixture layer thickened and plenty of small bubbles gathered in the channel. The air had greater influence on the phase interface area of unstable flow patterns than that of stable flow patterns. This phenomenon could not only be observed in the pictures of flow patterns, but also be reflected in the bottom wall pressure and temperature distributions. The average heat transfer coefficient for pure steam jet in subcooled water flow was in the range of 3.92–6.81 MW/(m2 °C). Since air mass fraction increased, the average heat transfer coefficient decreased.

Marangoni condensation attracts much attention in recent years. This study focused on the effect of tube diameters on Marangoni condensation heat transfer in the case of ethanol–water mixture vapors. Several tube outer diameters, including 0.793 mm, 1.032 mm, 1.221 mm, 10.0 mm, and 20.0 mm, were chosen to indicate the phenomenon, as well as the vertical plate. The ranges of the tube diameters were from macroscale to microscale. The experimental results showed that for pure steam the heat transfer coefficients monotonically increased with the decrease in diameters. For the ethanol–water mixture vapors, the reduction effect of liquid thickness and the accumulation effect of condensate liquid jointly influenced the heat transfer. In the case of macrosurfaces, the promotion effect caused by diameter decrease played a dominant role, and the heat transfer coefficients increased with decreasing the diameters. In the case of microsurfaces, the negative effect of condensate liquid accumulation became active and wa...

The effect of nozzle structure on the steam jet lengths of submerged condensation in quiescent water is investigated theoretically and experimentally. Two typical nozzles are analyzed and tested. Theoretical analysis shows that nozzle structure has a great influence on the steam jet length but was paid little attention before. Then a theoretical model for steam jet length with different nozzle structures is proposed based on the expansion and compression wave theory. Theoretical model indicates that steam jet length is greatly affected by nozzle structure. The steam jet length of straight pipe nozzle is longer than that of orifice nozzle under the same pool water temperature and steam mass flux, and the steam jet length is inverse proportion to the maximum expansion ratio, approximately. Then the theoretical model is verified by the experimental results. Finally, a universal semi-empirical correlation considering the nozzle structure is proposed. The prediction length corresponds to the experimental data very well and the discrepancy is within ±25% for different nozzle structures for the steam mass flux 400–800 kg·m−2·s−1 and water temperature 10–70 °C.

An experimental study has been carried out to investigate the pressure oscillation of the sonic steam jet in a pool. The exit diameter of the nozzle was 8 mm and the steam mass flux was 298–865 kg/(m2 s), water temperature 20–70 °C. The dominant frequency and amplitude of pressure oscillation have been analyzed. A theoretical model on pressure oscillation amplitude was set up and a semi-empirical correlation was given to predict the dimensionless R.M.S (root mean square) amplitude of pressure oscillation. The pressure oscillation is mainly caused by the variation of steam speed δu, heat transfer coefficient δh and net steam-water interface δS. The dominant frequency of the pressure oscillation decreased with the increase of the water temperature while increased in CO region and decreased in SC region with the increase of the steam mass flux. The amplitude of the pressure oscillation is inversely proportional to the dominant frequency. The dominant frequencies did not change with the variation of x/de and r/de. But the amplitudes decreased with the increase of x/de and r/de. An empirical correlation was suggested to predict the dimensionless R.M.S amplitude based on the experimental data. The predictions agreed well with the experiments, and the discrepancies were within ±30%.

In this paper, condensation heat transfer characteristics of ethanol–water vapor mixtures on a vertical mini-vertical tube with 1.221 mm outside diameter were investigated experimentally. The experiments were performed at different velocities and pressures over a wide range of ethanol mass fractions in vapor. The test results indicated that, with respect to the change of the vapor-to-surface temperature difference, the condensation curves of the heat transfer coefficients revealed nonlinear characteristics, and had peak values. At 2 % ethanol mass fraction in vapor, the condensation heat transfer coefficient value of the ethanol–water vapor mixture was found to have a maximum heat transfer coefficient of 50 kW m−2 K−1, which was 3–4 times than that of pure steam. The condensation heat transfer coefficients decreased with increased ethanol mass fraction in vapor. The vapor pressure and vapor velocity had a positive effect on the condensation heat transfer coefficients of ethanol–water vapor mixtures.

An experimental investigation was carried out to find the lifting-pressure performance of a steam-driven jet injector for various configuration parameters. The pressure profiles along the mixing chamber were measured with constant inlet steam and water parameters; the results indicated that the injector had a self-adaptive characteristic and the outlet water mass flow rate had an invariable characteristic. The lifting-pressure coefficient was affected significantly by the area ratio of the secondary nozzle and area ratio of the mixing chamber, and the influences were discussed. Moreover, the pressure distribution characteristic of a supersonic steam jet in water was studied under different steam pressures and water temperatures. The results indicated that the pressure distributions were affected by flow and condensation characteristics that were described by steam pressure and water temperature; the maximum axial pressure ratio was also discussed. Predictions of the distance of the maximum axial pressure ...

The heat transfer characteristics for condensation onto three plates (flat, taper fin, and flat fin) of water-ethanol vapor have been systematically investigated. A comparison of the three condensation heat transfer characteristics was made, and the effect of temperature gradients on the Marangoni condensation heat transfer was investigated. The results showed that the condensation modes on the surfaces with temperature gradients were usually a mixture of several different modes, while a single mode usually occurred on the condensing surface of the plat plate. The change of condensation modes on plates with fins was less marked and frequent than that on the flat plate. The mean heat transfer coefficients for the flat-fin plate, which had larger temperature gradients on the condensing surface, were greater than those on the surfaces with smaller temperature gradients. However, the degree of promotion of heat transfer by the temperature gradients depended on their values. Temperature gradients on the condensing surface made the vapor-to-surface temperature difference region, responsible for enhancing heat transfer, move to the lower region, and larger temperature gradients produced more significant movement. Moreover, the positive effect of both vapor velocity and pressure on the heat transfer was weakened by temperature gradients. The enhancement effect of vapor velocity and pressure on heat transfer was weaker when the temperature gradients on the condensing surface were larger.

Condensation heat transfer of sonic steam jet in subcooled water was investigated experimentally over a wide range of steam mass flux and water temperature. Four different steam plume shapes were observed in present test conditions, and condensation regime map was given based on steam mass flux and water temperature. Maximum expansion ratio and dimensionless penetration length of the steam jet were also obtained in the ranges of 1.04–2.20 and 2.86–14.60, respectively. Then the semi-empirical correlations were given to predict the expansion ratio and penetration length, the results showed good agreement between the predictions and experiments. Moreover, temperature fields in the steam plume and surrounding water were measured. Axial temperature distributions represented the four typical steam plumes, and variation of the axial temperature confirmed existence of expansion and compression waves. Finally, surface renewal model was adopted to predict condensation heat transfer coefficients, which were in the range of 0.98–1.45 MW/m 2 K and mainly dependent on the physical property and steam plume shape, including expansion angle, expansion ratio and penetration length.

A low mass flux steam jet in subcooled water was experimentally investigated. The transition of flow pattern from stable jet to condensation oscillation was observed at relatively high water temperature. The axial total pressures, the axial and radial temperature distributions were measured in the jet region. The results indicated that the pressure and temperature distributions were mainly influenced by the water temperature. The correlations corrected with water temperature were given to predict the dimensionless axial pressure peak distance and axial temperature distributions in the jet region, the results showed a good agreement between the predictions and experiments. Moreover, the self-similarity property of the radial temperature was obtained, which agreed well with Gauss distribution. In present work, all the dimensionless properties were mainly dependent on the water temperature but weakly on the nozzle size under a certain steam mass flux.

Bubble dynamics is quite complicated in the field of two-phase hydrodynamics because the interfacial heat and mass transfer is comprehensively affected by various influencing factors. Bubble condensation can be either thermally controlled or inertia controlled. Inertia controlled bubble condensation indicates that considerable pressure difference exists between the steam bubble and ambient liquid. In this paper, the inertia controlled steam bubble condensation was simulated using moving particle semi-implicit (MPS) method. The spherical bubble is located in the center of the cylindrical pool which makes the possibility of 2-D axisymmetric computation. The lateral and bottom wall are set to be rigid insulated boundaries and the top is free surface boundary. The pool volume must be large enough to eliminate the effects by pool wall. The initial bubble pressure ranges from 0.48 MPa to 3.98 MPa, and the initial bubble diameter ranges from 2 mm to 5 mm, and the ambient water pressure and temperature is 0.1 MPa and 70 °C, respectively. The bubble dynamics during condensation was investigated and the influences of initial bubble pressure and diameter were obtained. The bubble deformation during condensation is shown in figure 1, and the variations of bubble diameters and pressures during condensation are shown in figures 2 and 3, respectively.

In present experiment, the vapor mixture with different velocities (2m⋅s−1, 4m⋅s−1) and different ethanol mass fraction (0.5%, 1%, 2%, 5%, 10%, 20%, 50%) flew through vertical micro-tube and condensed on the outer tube surface at pressure 31.16kPa, 47.36kPa. The condensation modes were observed by CCD camera, and the characteristics of the heat transfer coefficients versus the vapor-to-surface temperature differences for different experimental conditions were obtained. The condensation heat transfer coefficients of vapor mixture decrease with the vapor concentration increasing. The maximum peak value of heat transfer coefficients, up to 39 kW⋅m−2⋅K1, which was about 3-4 times greater than that of steam, appeared when the ethanol mass fraction was 2%. A heat transfer coefficient correlation including the effects of all the tested parameters is proposed by using the multiple linear least squares method based on the experimental data. The calculated values agreed well with the experimental data and the deviations between them were from −20% to 20%.

In this paper, the steam shape parameters and the condensation oscillation characteristics of the direct contact condensation of submerged steam jet into subcooled water were investigated through a side hole nozzle. Meanwhile, the dimensionless jet length and the expansion ratio versus pool water temperature and steam mass flux were obtained by measuring the photographs taken by a high speed camera. Both of them increased gradually with rise of pool water temperature and steam mass flux. A comparison of the shape parameters of three different style nozzles was also achieved. And a correlation of the dimensionless jet length was obtained, the predicted data agreed well with the experimental data, while the discrepancy was within ±5%. For the pressure oscillation versus steam mass flux, the peaks and the root mean square value of pressure oscillation were almost consistent in the range of 150-400 kgm-2s-1, while both of them increase in the range of 400-800 kgm-2s-1. The positive peak and negative peak were completely symmetrical.