Spout Nozzle Research Articles

Experimental study on the effect of feed water nozzles on non-equilibrium temperature difference and flash evaporation in a single-stage evaporator and an investigation of effect of process parameters on the liquid flashing in a LTTD desalination process

Low temperature thermal desalination (LTTD) process involves flash evaporation of a seawater at 28–29°C in a single-stage evaporator maintained at a vacuum of around 25–27 m bar (abs). The seawater was splashed inside an evaporator through a 0.1 m diameter upward facing nozzles of around 24 nos arranged evenly throughout the evaporator and generated vapour was condensed in the shell and tube condenser using cooling water available at 12–13°C sucked from the deep sea through a long HDPE pipe. The main objective of this study was to find out the effect of geometry of the upward facing nozzles on the flash evaporation rate as well as on the non-equilibrium temperature difference (NETD) of the flashing process. Two different spout nozzle geometries with 0.37–0.87 m height were used in the experiment. The study indicated that the flashing rate increased by 0.9% (average) and and the NETD (Two – Tsat) decreased by 0.7°C (average), respectively, when nozzle height was increased by 0.87 m. Mechanism that controlled these two factors were identified and discussed in this paper. Drawbacks of 0.37 m nozzle geometry was also discussed. It was reported in literature that 4% yield ratio was obtained for a nozzle injection pressure of 1 bar for a similar desalination process. But in the present study, a maximum of 1.12% yield ratio was obtained with a nozzle injection pressure of around 0.17 bar. In this work,the effect of the process parameters on the liquid flashing in a LTTD desalination process was investigated and discussed. In order to fine tune the evaporator design for the future LTTD plants, the experimental results of flash evaporation were compared with two mathematical models obtained from the literature. While comparing the results, it was observed that the model which used actual heat (Twi – Two) made a good agreement with the experimental data compared to the other model that used superheat (Twi – Tsat). From the experimental study, it was observed that the NETD (i.e. thermal loss) measured was found to be higher than the predicted value. The reason that caused the difference in the NETD value was investigated and discussed. Suitable suggestions to reduce these NETD in the flashing process were also presented.

ラマン散乱光計測による容器内に高速で噴出した水素ガスの挙動に関する研究

New equipment to measure concentration and position of gases in a space from remote position was developed. The measurement principle is to detect Raman scattering light emitted when laser light is irradiated to gases. In these years, hydrogen is expected as a next-generation energy carrier, but it becomes a key issue to secure safety at the time of the use. The behavior of hydrogen in a space is not examined enough experimentally yet. The present research is intended to know what kind of behavior of hydrogen is shown in the 30cm×30cm×30cm container by detecting Raman scattering from hydrogen. A Raman scattering occur by irradiating a material with light and the wavelength is different from the one of the original light. The wavelengths are different for each gas class. The strength of light is known to be proportional to concentration. Therefore, it is possible to distinguish a gas class and can calculate gas concentration. Generally, some amount of delay occurs for detection time when using conventional sensors, but there are almost no delays by the new Raman sensor. 6mm & 1mm diameter holes are used as a spout nozzle to change initial velocities. To ensure the result, we used a special sheet which changes its color when it detected hydrogen, and visualized the hydrogen behavior. As a result, the behavior of the hydrogen gas in the small space was observed.

Spouting Characteristics of Wet Particles in a Conical-Cylindrical Spouted Bed

Spout characteristics, such as flow pattern, minimum spouting velocity, and maximum spoutable bed height, are investigated in a wet conical-cylindrical spouted bed. Water and glass beads (Geldart D type) are adopted as the liquid and solid phases, respectively. The evolution of flow pattern of a wet spouted bed is captured by a CCD camera. The experimental results indicate that the minimum spouting velocity decreases when increasing the liquid saturation. The increase of initial bed height, particle size, or spout nozzle size leads to increased minimum spouting velocities. A correlation is formulated based on the experiments results for the prediction of minimum spouting velocities of wet spouted beds. Moreover, it is found that the maximum spoutable bed height Hmax decreases as particle size or spout nozzle diameter increases. However, Hmax is almost constant, approximately 1.5 times higher than that of its corresponding dry spouted bed, when increasing the liquid saturation.

A new empirical equation for minimum spouting/spout‐fluidization velocity in draft tube spout‐fluid beds at elevated temperature

Draft tube spout‐fluid beds have been widely used in drying, coating, and granulation processes. In these processes, the spout‐fluid reactor is always operated at gas temperatures that exceed ambient conditions. Therefore, one objective of draft tube spout‐fluid bed research is to determine the critical factors that affect the minimum spouting velocity (Ums) and the minimum spout‐fluidization velocity (Umsf) at high temperatures. In this study, four types of particles were used to study the resulting pressure drops. Ums and Umsf were used in a conical draft tube spout‐fluid bed at temperatures of 293–500 K. In addition, a series of operating conditions and geometric configurations were investigated to systematically study the factors that affect Ums and Umsf. Overall, Ums and Umsf increased as the static bed height, entrainment zone height, draft tube diameter, and particle diameter increased. In contrast, Ums decreased as the superficial fluidizing gas velocity and spout nozzle diameter increased. In addition, Umsf increased as the superficial fluidizing gas velocity, spout nozzle diameter, and temperature increased. Furthermore, as the fluidizing gas flow increased, the minimum spouting velocity shifted from increasing to decreasing as the temperature gradually increased. Two general correlations between the Ums and Umsf values and the above factors were proposed. In addition, the influences of operating conditions and geometrical parameters on the minimum spouting velocity should be considered in the design and use of draft tube spout‐fluid beds.

Prediction of the Minimum Spouting Velocity by Genetic Programming Approach

A genetic programming (GP) algorithm is developed to estimate the minimum spouting velocity (Ums) in the spouted beds with a cone base. In order to have a general model, five dimensionless variables including seven critical geometric and operating parameters of spouted beds, namely, column diameter, spout nozzle diameter, base angle, static bed height, particle diameter, particle density, and gas density, have been taken as model inputs. A general correlation including nearly all fundamental and operating variables has been obtained based on the GP approach. The Ums values predicted by the GP are in fair agreement with those obtained by experiments, with a root-mean-square error of 0.1329 m/s. The model results show that GP can be used as an effective tool to provide relatively accurate information on minimum spouting velocity in conical spouted beds.

Intelligent prediction of minimum spouting velocity of spouted bed by back propagation neural network

A back-propagation neural network (BP-neural network) model was developed to predict the minimum spouting velocity (Ums) in spouted beds. Five dimensionless variables involving seven key geometric and operating parameters of spouted beds, i.e. column diameter, spout nozzle diameter, base angle, static bed height, particle diameter, particle density and gas density, were constructed as model inputs. An adaptive genetic algorithm was used to determine the nuclear parameters in a BP-neural network. 164 experimental data from the published literature were divided into two equal groups, for training and validating the neural network model, respectively. Comparisons of predictions by the BP-neural network and existing empirical equations with experimental data showed that Ums values predicted by the BP-neural network were in good agreement with experimental values, with a mean relative error of 12.9%, somewhat better than calculations by existing empirical equations. This indicates that an artificial neural network is a useful and promising way to predict Ums as an alternative to empirical equations, especially when the relationship of geometric and operating parameters to Ums is complex and difficult to describe.

Investigation on Flow Patterns and Transitions in a Multiple-Spouted Bed

Experimental studies on flow patterns and transitions were carried out in a visible multiple-spouted bed. The bed combines three spouted bed cells, each with a cross-section of 100 × 30 mm, and each cell has an independent spout nozzle of 10 mm in width. Polypropylene beads with a density of 900 kg/m3 and mean diameter of 2.8 mm were used as bed materials. Six distinct flow patterns, i.e., fixed bed (FB), internal jet (IJ), internal jet with bubble (IJB), single spouting (SS), multi-spouting (MS), and internal jet with slugging (IJS), were determined on the basis of criteria as well as schematic diagrams and typical flow pattern images obtained from a high-resolution digital charge coupled device (CCD) camera. Typical flow regime maps at three static bed heights were plotted to describe the transitions of flow patterns with central and auxiliary spouting gases. Besides, some important flow characteristics associated with flow patterns and transitions, i.e., minimum spouted velocity and pressure drop, were...

Minimum spouting velocity in a spout‐fluid bed with a draft tube

AbstractMinimum spouting velocity was measured in a 0.12 m cylindrical spout‐fluid bed with a draft tube. The effects of fluidizing gas flow rate, entrainment height, and spout nozzle diameter on minimum spouting velocity were discussed. A correlation on minimum spouting velocity has been proposed based on the present experimental data.

Maximum spoutable bed height of spout-fluid bed

Experimental study on the maximum spoutable bed height of a spout-fluid bed (cross-section of 0.3 m × 0.03 m and height of 2 m) packed with Geldart group D particles has been carried out. The effects of particle size, spout nozzle size and fluidizing gas flow rate on the maximum spoutable bed height were studied. Experimental data were compared to some published experiments and predictions. The results show that the maximum spoutable bed height of spout-fluid bed decreases with increasing particle size and spout nozzle size, which appears the same trend to that of spouted beds. The increasing of fluidizing gas flow rate leads to a sharply decrease in the maximum spoutable bed height. The existent correlations of the maximum spoutable bed height in the literature were observed to involve large discrepancies. Additionally, the flow characteristics when bed materials deeper than the maximum spoutable height were summarized. Under this condition, the spout-fluid bed operated without a stable and coherent spout or fountain assembles the characteristics of jetting fluidized bed. Besides, the mechanisms of spout termination were investigated. It was found that slugging in the spout and growth of instabilities would cause the spout termination in spout-fluid bed.

Hydrodynamic characteristics of spout-fluid bed: Pressure drop and minimum spouting/spout-fluidizing velocity

Experimental investigations on the hydrodynamic characteristics were carried out in a two-dimensional spout-fluid bed with cross section of 300 mm × 30 mm and height of 2000 mm. Six kinds of Geldart group D particles were used as bed materials. The effects of static bed height, particle property, spout nozzle width and fluidizing gas velocity on the pressure drop, maximum spouting pressure drop, minimum spouting velocity and minimum spout-fluidizing velocity were systematically studied. The results show that the total bed pressure drop appears a spouted bed characteristic when increasing the spouting gas velocity and keeping the fluidizing gas velocity constant, while it appears a fluidized bed characteristic when increasing the fluidizing gas velocity and keeping the spouting gas velocity constant. The maximum spouting pressure drop required to initiate spouting increases with static bed height and particle density, but decreases with particle diameter, spout nozzle width and fluidizing gas velocity. The minimum spouting and spout-fluidizing velocities both increase with static bed height, particle diameter, spout nozzle width. The minimum spout-fluidizing velocity increases while the minimum spouting velocity decreases with fluidizing gas velocity. Additional, correlations considered all of the above effects were developed to predict the minimum spout-fluidizing and spouting velocities of the spout-fluid bed, which were in satisfied agreement with the present experiments and some published experimental results.

Jet penetration depth in a two-dimensional spout–fluid bed

The jet penetration depth was proposed to be an important parameter to describe the jet action during the chemical process of spout–fluid bed coal gasification. A two-dimensional cold model of a spout–fluid bed coal gasifier with its cross section of 300 mm × 30 mm and height of 2000 mm was established to investigate the jet penetration depth. Four types of Geldart group D particles were used as bed materials. A multi-channel pressure sampling system and a high-resolution digital CCD camera were employed for experimental investigations. The effects of spouting gas velocity, spout nozzle diameter, static bed height, particle property and fluidizing gas flow rate on the jet penetration depth have been systematically studied by pressure signal analysis and image processing. Experimental results indicate that the jet penetration depth increases with increasing spouting gas velocity and spout nozzle diameter, while it decreases with increasing particle density, particle diameter, static bed height and fluidizing gas flow rate. Additional, a new correlation considered all of the above effects especially static bed height and fluidizing gas flow rate, was developed for predicting the jet penetration depth in spout–fluid beds. The correlation was compared with published experimental data or correlations, which was in well agreement with the present experimental results and some other references.

Automatic micro dimension measurement using image processing methods

In this paper, a technique to measure the locations and orientations of apertures, and their diameters, on the spout nozzle of an engine is presented and a complex measuring apparatus designed for the purpose is discussed. This consists of an area CCD camera, an image acquisition card, stepper motors, optical and mechanical units and a computer system for data acquisition and control. Results on the performance of the system are presented.

The efficiency of a drinking fountain

In this experiment the efficiency of a water drinking fountain was studied. Efficiency was defined in terms of the percentage of water actually consumed in relation to the water that flows from the drinking fountain, the dringing time, the water consumed per user and the electricity required to cool the water. For this purpose four different spout diameters were used and the water pressure was regulated to give two different water trajectory heights for each spout diameter setting. This resulted in eight different flow rates. The results of the study indicated that the water fountain is a highly inefficient water transfer mechanism and that extreme flow rates worsened the efficiency of the system. The intermediate spout nozzle diameters proved to be superior with regard to all the effeciency statistics.