Mixing of two fluid streams can be seen in many applications in chemical processing and energy generation industries. The supersonic steam blows into the cold water in the mixing nozzle. When the steam condenses, steam transfers to water heat and mass (because of the temperature difference and condensation) and momentum (because of the velocity difference). The condensation should be fully completed before the end of mixing nozzle. Thus, the length of the mixing nozzle is important parameter. After the condensation is completed, the flow is single phase, that is, liquid water, and the subsonic water flows in the converging nozzle. In this study, the mixing of the supersonic steam and subsonic water in a converging nozzle is investigated. The problem is modeled using one-dimensional continuity, momentum and energy equations, and solved numerically. For the calculation of the rate of condensation, a correlation for the contact heat transfer coefficient is used.
{"title":"Mixing of Two Streams, Steam and Water, in a Converging Nozzle","authors":"H. Aybar","doi":"10.1115/imece2000-1527","DOIUrl":"https://doi.org/10.1115/imece2000-1527","url":null,"abstract":"Mixing of two fluid streams can be seen in many applications in chemical processing and energy generation industries. The supersonic steam blows into the cold water in the mixing nozzle. When the steam condenses, steam transfers to water heat and mass (because of the temperature difference and condensation) and momentum (because of the velocity difference). The condensation should be fully completed before the end of mixing nozzle. Thus, the length of the mixing nozzle is important parameter. After the condensation is completed, the flow is single phase, that is, liquid water, and the subsonic water flows in the converging nozzle. In this study, the mixing of the supersonic steam and subsonic water in a converging nozzle is investigated. The problem is modeled using one-dimensional continuity, momentum and energy equations, and solved numerically. For the calculation of the rate of condensation, a correlation for the contact heat transfer coefficient is used.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122450573","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2000-11-05DOI: 10.1299/KIKAIB.66.649_2405
H. Shirakawa, Y. Takata, Torato Kuroki, Takehiro Ito, S. Satonaka
Numerical method for thermal and fluid flow with free surface and phase change has been developed. The calculation result of one-dimensional solidification problem agrees with Neumann’s theoretical value. We applied it to a bubble growth in superheated liquid and obtained the result that a bubble grows with spherical shape. The present method can be applicable to various phase change problems.
{"title":"Numerical Solution of Thermal and Fluid Flow With Phase Change by VOF Method","authors":"H. Shirakawa, Y. Takata, Torato Kuroki, Takehiro Ito, S. Satonaka","doi":"10.1299/KIKAIB.66.649_2405","DOIUrl":"https://doi.org/10.1299/KIKAIB.66.649_2405","url":null,"abstract":"\u0000 Numerical method for thermal and fluid flow with free surface and phase change has been developed. The calculation result of one-dimensional solidification problem agrees with Neumann’s theoretical value. We applied it to a bubble growth in superheated liquid and obtained the result that a bubble grows with spherical shape. The present method can be applicable to various phase change problems.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114268803","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This experiment is based on a heating surface consisting of micro heaters where the temperature of each heater can be individually controlled by an electronic feedback loop similar to those used in hotwire anemometry. The power consumed by the heaters throughout the cycle of individual bubble growth, coalescence and departure was measured at high frequencies, thus the heat flux and its variation were obtained. At the same time, visualization of bubbles’ behaviour by a fast CCD camera has been performed to gather more information. By combining the heat flux data closely with the visualization result, we have found that the single bubble’ heat flux variation correlates with the separate stages of its life cycle: nucleation, growth, detachment and departure. By careful timing and control of two individual heaters, we were able to grow two individual bubbles side-by-side. The coalescence of these two bubbles would take place when they grow to a certain size that allows them to touch each other. We have recorded two major heat flux spikes for a typical cycle. The first one corresponds to the nucleation of bubbles, the second one is for the coalescence of the two bubbles. We found that the heat flux variation is closely related to the bubble dynamics and bubble-bubble interaction.
{"title":"Coalescence of Dual Bubbles on Micro Heaters","authors":"Tailian Chen, J. Chung","doi":"10.1115/imece2000-1505","DOIUrl":"https://doi.org/10.1115/imece2000-1505","url":null,"abstract":"\u0000 This experiment is based on a heating surface consisting of micro heaters where the temperature of each heater can be individually controlled by an electronic feedback loop similar to those used in hotwire anemometry. The power consumed by the heaters throughout the cycle of individual bubble growth, coalescence and departure was measured at high frequencies, thus the heat flux and its variation were obtained. At the same time, visualization of bubbles’ behaviour by a fast CCD camera has been performed to gather more information. By combining the heat flux data closely with the visualization result, we have found that the single bubble’ heat flux variation correlates with the separate stages of its life cycle: nucleation, growth, detachment and departure. By careful timing and control of two individual heaters, we were able to grow two individual bubbles side-by-side. The coalescence of these two bubbles would take place when they grow to a certain size that allows them to touch each other. We have recorded two major heat flux spikes for a typical cycle. The first one corresponds to the nucleation of bubbles, the second one is for the coalescence of the two bubbles. We found that the heat flux variation is closely related to the bubble dynamics and bubble-bubble interaction.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"102 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130154957","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
An investigation of wave processes in liquids with bubbles containing evaporating drops is presented. A model is used which takes into account both the liquid radial inertia due to medium volume changes, and the temperature distribution inside and around the bubbles. An analysis of the microsopic fields of physical parameters is aimed at closing the system of equations for averaged characteristics. The evolution of non-steady shock waves in liquids with bubbles containing evaporating drops is studied by numerical methods. The effect of the initial conditions, shock strength, volume fraction, dispersity of the vapor phase, initial static pressure and of the thermophysical properties of the phases on shock-wave structure and evolution is studied. The possible enhancement of disturbances in the region of their initiation is shown. The phenomenon of the nonlinear anomalous enhancement of waves reflected from a wall is established.
{"title":"Shock Waves in Liquids With Bubbles Containing Evaporating Drops","authors":"N. Khabeev, A. Bertelsen, O. R. Ganiev","doi":"10.1115/imece2000-1523","DOIUrl":"https://doi.org/10.1115/imece2000-1523","url":null,"abstract":"\u0000 An investigation of wave processes in liquids with bubbles containing evaporating drops is presented. A model is used which takes into account both the liquid radial inertia due to medium volume changes, and the temperature distribution inside and around the bubbles. An analysis of the microsopic fields of physical parameters is aimed at closing the system of equations for averaged characteristics. The evolution of non-steady shock waves in liquids with bubbles containing evaporating drops is studied by numerical methods. The effect of the initial conditions, shock strength, volume fraction, dispersity of the vapor phase, initial static pressure and of the thermophysical properties of the phases on shock-wave structure and evolution is studied.\u0000 The possible enhancement of disturbances in the region of their initiation is shown. The phenomenon of the nonlinear anomalous enhancement of waves reflected from a wall is established.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"51 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124760021","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Heat transfer measurements and photographic studies were performed to capture the detailed evolution of liquid-vapor interfacial behavior near critical heat flux (CHF) for a 90-degree downward-facing convex surface. The test surface, with a width of 3.2 mm and a 102.6-mm radius, consisted of a series of nine heaters which dissipated equal power. Instrumentation within each heater facilitated localized heat flux and temperature measurements along the convex surface, and transparent front and back windows enabled optical access to a fairly two-dimensional liquid-vapor interface. Near CHF, vapor behavior along the convex surface was cyclical in nature and somewhat similar to that observed in pool boiling on horizontal downward-facing flat surfaces. The vapor repeatedly formed a stratified layer at the bottom of the convex surface, which stretched as more vapor was generated, and then departed from the surface. Subsequently, the bottom (downward-facing) heaters, followed by the other heaters, were wetted with liquid before the nucleation/coalescence/stratification/release process repeated itself. Prior to CHF, the surface was adequately cooled by the liquid wetting. At CHF, the surface was still wetted for a brief period, but the wetting time was too short to allow adequate cooling of the downward-facing heaters, and the temperature of these heaters began to rise. This study proves that despite the pronounced thickening of the vapor layer as it propagates upwards along the convex surface, CHF always commences on the downward-facing heaters.
{"title":"Pool Boiling Critical Heat Flux on a Downward-Facing Convex Surface","authors":"A. Howard, I. Mudawar","doi":"10.1115/imece2000-1503","DOIUrl":"https://doi.org/10.1115/imece2000-1503","url":null,"abstract":"\u0000 Heat transfer measurements and photographic studies were performed to capture the detailed evolution of liquid-vapor interfacial behavior near critical heat flux (CHF) for a 90-degree downward-facing convex surface. The test surface, with a width of 3.2 mm and a 102.6-mm radius, consisted of a series of nine heaters which dissipated equal power. Instrumentation within each heater facilitated localized heat flux and temperature measurements along the convex surface, and transparent front and back windows enabled optical access to a fairly two-dimensional liquid-vapor interface. Near CHF, vapor behavior along the convex surface was cyclical in nature and somewhat similar to that observed in pool boiling on horizontal downward-facing flat surfaces. The vapor repeatedly formed a stratified layer at the bottom of the convex surface, which stretched as more vapor was generated, and then departed from the surface. Subsequently, the bottom (downward-facing) heaters, followed by the other heaters, were wetted with liquid before the nucleation/coalescence/stratification/release process repeated itself. Prior to CHF, the surface was adequately cooled by the liquid wetting. At CHF, the surface was still wetted for a brief period, but the wetting time was too short to allow adequate cooling of the downward-facing heaters, and the temperature of these heaters began to rise. This study proves that despite the pronounced thickening of the vapor layer as it propagates upwards along the convex surface, CHF always commences on the downward-facing heaters.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"162 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128222980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A growing number of multiphase technology applications stimulate the development of reliable methods for modeling transient processes in two-phase systems in which the temperature field in the moving fluid and the temperature field in the bounding walls are directly dependent on each other. This situation presents a conjugate heat-transfer problem since the heat-transfer rate at the wall-fluid interface and local fluid conditions are not known a priori, and therefore need to be simultaneously calculated. Examples of such processes include the direct heating of multiphase pipelines, a change of heat load in evaporators of two-phase thermal control systems, startup or shutdown of systems with a two-phase working fluid. In this paper, direct electrical heating of a long two-phase pipeline has been modeled. The modeling of transient two-phase flow and heat transfer in the pipeline is based on two different mathematical formulations. In the first formulation, the transient heat conduction and the forced convection effects are rigorously taken into account. The second formulation assumes that the pipe wall and the fluid are in local thermal equilibrium. The effect of the thermal capacity of the pipe wall is taken into account by an additional term in the energy equation for the fluid flow. Such an approach allows significant simplifying the problem and reducing the computer running time. Numerical simulation of the sudden heat input to the pipe wall has been performed using both formulations of field equations. The practical significance of the results obtained is discussed.
{"title":"Numerical Study of Transient Conjugate Heat Transfer in a Long Two-Phase Pipeline","authors":"Y. Fairuzov, Hector Arvizu Dal Piaz","doi":"10.1115/imece2000-1536","DOIUrl":"https://doi.org/10.1115/imece2000-1536","url":null,"abstract":"\u0000 A growing number of multiphase technology applications stimulate the development of reliable methods for modeling transient processes in two-phase systems in which the temperature field in the moving fluid and the temperature field in the bounding walls are directly dependent on each other. This situation presents a conjugate heat-transfer problem since the heat-transfer rate at the wall-fluid interface and local fluid conditions are not known a priori, and therefore need to be simultaneously calculated. Examples of such processes include the direct heating of multiphase pipelines, a change of heat load in evaporators of two-phase thermal control systems, startup or shutdown of systems with a two-phase working fluid. In this paper, direct electrical heating of a long two-phase pipeline has been modeled. The modeling of transient two-phase flow and heat transfer in the pipeline is based on two different mathematical formulations. In the first formulation, the transient heat conduction and the forced convection effects are rigorously taken into account. The second formulation assumes that the pipe wall and the fluid are in local thermal equilibrium. The effect of the thermal capacity of the pipe wall is taken into account by an additional term in the energy equation for the fluid flow. Such an approach allows significant simplifying the problem and reducing the computer running time. Numerical simulation of the sudden heat input to the pipe wall has been performed using both formulations of field equations. The practical significance of the results obtained is discussed.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"46 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122961359","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Doerffer, D. Groeneveld, K. F. Rudzinski, I. Pioro, J. Martin
This paper summarizes the effects of various types or numbers of critical-heat-flux (CHF)-enhancing inserts in tubular geometries. The impact of inserts on CHF is frequently expressed by an enhancement ratio K: the ratio of CHF with an insert to the CHF in a bare tube for the same local flow conditions. The impact on K of the following parameters was investigated: (i) fluid type (Freon-134a, water), (ii) axial spacing between inserts, (iii) shape of the insert, (iv) flow blockage of the insert, (v) number of similar/dissimilar insert planes upstream, and (vi) impact of flow conditions. The spacing and flow-obstruction area were found to be the major geometric factors that affected K: by decreasing the relative spacing, L/D, to 16, K can reach a value of from 2 to 3, depending on the flow-obstruction area. Among flow parameters, the critical quality, xc, usually has a strong effect on K: K can increase from a value of 1 to 3, when xc increases from 0 to 0.4 for a mass flux G ≥ 2 Mg/m2s. For G < 2 Mg/m2s, CHF enhancement can disappear or become negative (K < 1). No cumulative effect was found on K for a series of upstream insert planes. CHF enhancement does not depend on fluid type, provided that the conditions in the fluids meet the CHF fluid-to-fluid modelling requirements.
{"title":"Some Aspects of Critical-Heat-Flux Enhancement in Tubes","authors":"S. Doerffer, D. Groeneveld, K. F. Rudzinski, I. Pioro, J. Martin","doi":"10.1115/imece2000-1518","DOIUrl":"https://doi.org/10.1115/imece2000-1518","url":null,"abstract":"\u0000 This paper summarizes the effects of various types or numbers of critical-heat-flux (CHF)-enhancing inserts in tubular geometries. The impact of inserts on CHF is frequently expressed by an enhancement ratio K: the ratio of CHF with an insert to the CHF in a bare tube for the same local flow conditions. The impact on K of the following parameters was investigated: (i) fluid type (Freon-134a, water), (ii) axial spacing between inserts, (iii) shape of the insert, (iv) flow blockage of the insert, (v) number of similar/dissimilar insert planes upstream, and (vi) impact of flow conditions. The spacing and flow-obstruction area were found to be the major geometric factors that affected K: by decreasing the relative spacing, L/D, to 16, K can reach a value of from 2 to 3, depending on the flow-obstruction area. Among flow parameters, the critical quality, xc, usually has a strong effect on K: K can increase from a value of 1 to 3, when xc increases from 0 to 0.4 for a mass flux G ≥ 2 Mg/m2s. For G < 2 Mg/m2s, CHF enhancement can disappear or become negative (K < 1). No cumulative effect was found on K for a series of upstream insert planes. CHF enhancement does not depend on fluid type, provided that the conditions in the fluids meet the CHF fluid-to-fluid modelling requirements.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"391 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115308699","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The behaviors of the rewetting on pool film boiling, focusing on observations of a collapse of a vapor film, a wetted area and a contact angle on a superheated surface were investigated experimentally. Using a U-shaped platinum wire with 2 mm diameter and 140 mm long, pool film-boiling experiments were performed for saturated water at atmospheric pressure. After a stable film-boiling state at a prescribed initial wall temperature was established, saturated water from a nozzle, set above the test wire, was injected on the superheated surface in the stable film-boiling, then artificial rewetting was forced on the superheated surface. During forming the artificial rewetting, the temperature fluctuation right under the liquid injection and the behavior of the rewetting were obtained for the initial wall temperatures of 600, 420, 400 and 300 degree-C, respectively. The present experimental results showed that the propagative collapse of the vapor film occurred when the initial wall superheat was below 300 K. On the other hand, above the initial wall superheat of 320 K, the rewetting declined after liquid injection was finished then film boiling recovered. The temperature was related to the thermodynamic limit of superheat, according to the measured temperature fluctuation during supplying the liquid. The wetted area right after liquid-wall contact and the advancing velocity of the rewetting front increased as the initial wall superheat decreased. The measured angles between the liquid-vapor interfacial line and the heated wall corresponded to dynamic contact angles were close to the dynamic advancing contact-angles in room temperature.
{"title":"Study on the Behavior of a Wetted Area Right After Liquid-Wall Contact in Pool Film Boiling","authors":"H. Ohtake, A. Murakami, Y. Koizumi","doi":"10.1115/imece2000-1507","DOIUrl":"https://doi.org/10.1115/imece2000-1507","url":null,"abstract":"\u0000 The behaviors of the rewetting on pool film boiling, focusing on observations of a collapse of a vapor film, a wetted area and a contact angle on a superheated surface were investigated experimentally. Using a U-shaped platinum wire with 2 mm diameter and 140 mm long, pool film-boiling experiments were performed for saturated water at atmospheric pressure. After a stable film-boiling state at a prescribed initial wall temperature was established, saturated water from a nozzle, set above the test wire, was injected on the superheated surface in the stable film-boiling, then artificial rewetting was forced on the superheated surface. During forming the artificial rewetting, the temperature fluctuation right under the liquid injection and the behavior of the rewetting were obtained for the initial wall temperatures of 600, 420, 400 and 300 degree-C, respectively. The present experimental results showed that the propagative collapse of the vapor film occurred when the initial wall superheat was below 300 K. On the other hand, above the initial wall superheat of 320 K, the rewetting declined after liquid injection was finished then film boiling recovered. The temperature was related to the thermodynamic limit of superheat, according to the measured temperature fluctuation during supplying the liquid. The wetted area right after liquid-wall contact and the advancing velocity of the rewetting front increased as the initial wall superheat decreased. The measured angles between the liquid-vapor interfacial line and the heated wall corresponded to dynamic contact angles were close to the dynamic advancing contact-angles in room temperature.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"21 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123410239","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper summarizes the mass transfer modeling that can simulate the process of gaseous carbon dioxide dissolution into water in an orifice mixing system. In order to establish the operating characteristics of the orifice mixing system, ordinary tap water and pure carbon dioxide were used as the liquid-gas system. Using the model, computations were performed for an orifice mixing system to better understand the mass transfer process of gaseous carbon dioxide into water through both the elbow tube and the junction Venturi-tube. All computed results show different performance of the carbon dioxide dissolution rates for the given inlet water and carbon dioxide conditions of the four different designs of the junction type Venturi-tubes and an orifice mixing system. After examining the computed results it was found that the mass transfer efficiency of gaseous carbon dioxide into the water stream through the orifice mixing system was superior to that through the junction Venturi-tubes.
{"title":"Mass Transfer Process of Gaseous Carbon Dioxide Into Water Jet Through Orifice Mixing System","authors":"Y. Zheng, R. Amano","doi":"10.1115/imece2000-1526","DOIUrl":"https://doi.org/10.1115/imece2000-1526","url":null,"abstract":"\u0000 This paper summarizes the mass transfer modeling that can simulate the process of gaseous carbon dioxide dissolution into water in an orifice mixing system. In order to establish the operating characteristics of the orifice mixing system, ordinary tap water and pure carbon dioxide were used as the liquid-gas system. Using the model, computations were performed for an orifice mixing system to better understand the mass transfer process of gaseous carbon dioxide into water through both the elbow tube and the junction Venturi-tube. All computed results show different performance of the carbon dioxide dissolution rates for the given inlet water and carbon dioxide conditions of the four different designs of the junction type Venturi-tubes and an orifice mixing system. After examining the computed results it was found that the mass transfer efficiency of gaseous carbon dioxide into the water stream through the orifice mixing system was superior to that through the junction Venturi-tubes.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"106 3","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114080245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. S. Lakshminarasimhan, D. K. Hollingsworth, L. Witte
Experiments were performed to investigate nucleate flow boiling and incipience in a flow channel, 1 mm high × 20 mm wide × 357 mm long, vertical, with one wall heated uniformly and others approximately adiabatic. Subcooled R-11 flowed upward through the channel; the mass flux varied from 60 to 4586 kg/(m2s). The inlet subcooling varied from 3.0 to 15.3 °C, and the inlet pressure ranged up to 0.20 MPa. Liquid crystal thermography was used to measure distributions of surface temperature from which the heat transfer coefficients on the heated surface were calculated. Observations of the boiling incipience superheat excursion and the hysteresis phenomenon are presented and discussed. In laminar flow, a boiling front was observed that clearly separated the region cooled by single-phase convection from the region experiencing nucleate boiling. A prediction for the wall temperature and heat flux at boiling incipience based on nucleation theory compared favorably with the data. An incipience turning angle was defined to describe the transition process from the point of incipience to fully developed nucleate boiling. Fully developed saturated nucleate boiling was correlated well by Kandlikar’s technique.
在高1 mm ×宽20 mm ×长357 mm的垂直通道中进行了实验，研究了一壁均匀加热，其他壁近似绝热的核流沸腾和初始现象。过冷的R-11向上流过通道;质量通量在60 ~ 4586 kg/(m2s)之间变化。进气过冷度范围为3.0 ~ 15.3℃，进气压力范围为0.20 MPa。利用液晶热像仪测量表面温度分布，计算受热表面的传热系数。介绍并讨论了沸腾起始过热偏移和滞后现象的观测结果。在层流中，观察到一个沸腾锋，将单相对流冷却区与核沸腾区明显分开。根据成核理论对沸腾初壁温度和热流密度的预测与实测数据比较吻合。定义了起始角来描述从起始点到充分发展的核沸腾的过渡过程。完全发育的饱和核沸腾用Kandlikar技术进行了很好的关联。
{"title":"Boiling Incipience in Narrow Channels","authors":"M. S. Lakshminarasimhan, D. K. Hollingsworth, L. Witte","doi":"10.1115/imece2000-1506","DOIUrl":"https://doi.org/10.1115/imece2000-1506","url":null,"abstract":"\u0000 Experiments were performed to investigate nucleate flow boiling and incipience in a flow channel, 1 mm high × 20 mm wide × 357 mm long, vertical, with one wall heated uniformly and others approximately adiabatic. Subcooled R-11 flowed upward through the channel; the mass flux varied from 60 to 4586 kg/(m2s). The inlet subcooling varied from 3.0 to 15.3 °C, and the inlet pressure ranged up to 0.20 MPa. Liquid crystal thermography was used to measure distributions of surface temperature from which the heat transfer coefficients on the heated surface were calculated. Observations of the boiling incipience superheat excursion and the hysteresis phenomenon are presented and discussed.\u0000 In laminar flow, a boiling front was observed that clearly separated the region cooled by single-phase convection from the region experiencing nucleate boiling. A prediction for the wall temperature and heat flux at boiling incipience based on nucleation theory compared favorably with the data. An incipience turning angle was defined to describe the transition process from the point of incipience to fully developed nucleate boiling. Fully developed saturated nucleate boiling was correlated well by Kandlikar’s technique.","PeriodicalId":120929,"journal":{"name":"Heat Transfer: Volume 4","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2000-11-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127672788","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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