Characterization of Geometric Effects Induced by 90 Vertical Elbows in Air-water Two-phase Flow PDF Download
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Author: Shouxu Qiao Publisher: ISBN: Category : Languages : en Pages :
Book Description
Conventional modeling of two-phase flows is typically based on experimental data acquired in straight flow channels of different flow orientations with no flow restrictions. No model is currently available to dynamically predict the transition between different flow orientations. To bridge this gap, it is important to characterize and model the geometric effects induced by flow restrictions or junctions in air-water two-phase flows. The present work investigates the effects of a 90 vertical-upward to horizontal and a 90 horizontal to vertical-downward elbow on two-phase flow and establishes the interfacial area transport equation (IATE) applicable to air-water two-phase flow influenced by the 90 elbows. A detailed database for the local and global two-phase flow parameters in different flow orientations and across vertical elbows is established with state-of-the-art four-sensor conductivity probes, a pressure transducer, and a high-speed video camera. The elbow effects are characterized by investigating the evolution of void fraction, interfacial area concentration, bubble velocity and two-phase pressure drop across and downstream of elbows. The degree of influence made by the elbow is characterized by the variance of void fraction. The axial development of the flow downstream of the elbow is modeled by an exponential function of the axial length based on the experimental data. Then, the dissipation length of the elbow is determined by characterizing the evolution of the elbow strength parameter. The elbow strength parameter is also used to correlate the void-weighted bubble velocity and covariance terms in the IATE. The two-phase pressure drop across the vertical elbows is modeled with a modified Lockhart-Martinelli correlation that considers the minor loss induced by these elbows. The developed models and correlations are implemented into the IATE to establish a model that is applicable to the region influenced by the elbow. The established IATE is evaluated by the data obtained in different flow orientations and across elbows in bubbly flow. The newly developed IATE can predict the interfacial area concentration with an average percent difference of 6% compared with the experimental data, demonstrating that the models and correlations developed in this work for the two-phase flow parameters in elbow influenced regions are reliable.
Author: Shouxu Qiao Publisher: ISBN: Category : Languages : en Pages :
Book Description
Conventional modeling of two-phase flows is typically based on experimental data acquired in straight flow channels of different flow orientations with no flow restrictions. No model is currently available to dynamically predict the transition between different flow orientations. To bridge this gap, it is important to characterize and model the geometric effects induced by flow restrictions or junctions in air-water two-phase flows. The present work investigates the effects of a 90 vertical-upward to horizontal and a 90 horizontal to vertical-downward elbow on two-phase flow and establishes the interfacial area transport equation (IATE) applicable to air-water two-phase flow influenced by the 90 elbows. A detailed database for the local and global two-phase flow parameters in different flow orientations and across vertical elbows is established with state-of-the-art four-sensor conductivity probes, a pressure transducer, and a high-speed video camera. The elbow effects are characterized by investigating the evolution of void fraction, interfacial area concentration, bubble velocity and two-phase pressure drop across and downstream of elbows. The degree of influence made by the elbow is characterized by the variance of void fraction. The axial development of the flow downstream of the elbow is modeled by an exponential function of the axial length based on the experimental data. Then, the dissipation length of the elbow is determined by characterizing the evolution of the elbow strength parameter. The elbow strength parameter is also used to correlate the void-weighted bubble velocity and covariance terms in the IATE. The two-phase pressure drop across the vertical elbows is modeled with a modified Lockhart-Martinelli correlation that considers the minor loss induced by these elbows. The developed models and correlations are implemented into the IATE to establish a model that is applicable to the region influenced by the elbow. The established IATE is evaluated by the data obtained in different flow orientations and across elbows in bubbly flow. The newly developed IATE can predict the interfacial area concentration with an average percent difference of 6% compared with the experimental data, demonstrating that the models and correlations developed in this work for the two-phase flow parameters in elbow influenced regions are reliable.
Author: Christopher J. Ulmer Publisher: ISBN: Category : Languages : en Pages : 50
Book Description
Pressure measurements are taken for single-phase water and two-phase air-water flow at the Advanced Multi-Phase Flow Laboratory. Vertical and horizontal flow sections are available for measurement. The test section incorporates minor losses via 90-degree elbow. Pressure drop data is compared with predictions given by established models. Increased pressure losses are found with increasing liquid and gas flow rates. Geometric effects of elbows are observed as minor loss. Six single-phase flow conditions are considered. Single-phase pressure models include both major and minor losses. An average error of 7.6% is found for the pressure drop across the test section for all flow conditions. Five two-phase flow conditions are considered. The effects of phase interaction on pressure loss are observed. An average error between model and data is found to be 4.8% across the vertical section and 1.4% across the entire test section for all flow conditions.
Author: Mohan Singh Yadav Publisher: ISBN: Category : Languages : en Pages : 193
Book Description
This study investigates the geometric effects of flow restrictions and flow configurations on two-phase flow parameters. Experiments are conducted in two distinct experimental setups employing different flow configurations and flow restrictions. In the first experiment, comparison of the effects of 90-degree and 45-degree elbows on interfacial structures and their transport characteristics in horizontal two-phase bubbly flow is investigated. The setup is made out of 50.3 mm inner diameter glass tubes and a double-sensor conductivity probe is used to collect time averaged local data. Experimental results show that both elbows have significant effect on the development of interfacial structures as well as the bubble interaction mechanisms. Furthermore, there are characteristic similarities and differences between the effects of two elbows. While the effect of the 45-degree elbow is evident immediately after the elbow, the 90-degree elbow effect is propagated further downstream of the elbow. Moreover, it is shown that both the elbows induce oscillations in the interfacial structures and two-phase flow parameters, but the degree and the nature of oscillation differ. Comparison of the elbow effect on the axial transport of two-phase flow parameters is also investigated. The second set of experiments is performed in combinatorial two-phase flow facility to study the effects of 90-degree vertical elbow and geometric configuration on two-phase bubbly flow. The elbow has a significant effect on two-phase flow regime transition boundaries at measurement locations downstream of the elbow. Modified two-phase flow regime maps based on the extensive flow visualization studies are suggested for both vertical and horizontal test sections. A four-sensor conductivity probe is employed to measure time averaged two-phase local parameters as the flow develops along vertical upward to horizontal section across the 90-degree vertical elbow. The elbow causes the bubbles to align along the horizontal radius of the pipe cross-section, creating a bi-peaked profile in void fraction and interfacial area concentration. One dimensional transport of area averaged two-phase flow parameters shows that the elbow promotes bubble interaction mechanism.
Author: Shouxu Qiao
Author: Shouxu Qiao
Author: Christopher J. Ulmer
Author: Mohan Singh Yadav
Author: Ali Cemal Benim
Author: Thomas M. Aidich
Author: 
Author: United States. National Bureau of Standards
Author: 
Author: United States. National Bureau of Standards
Author: United States. National Bureau of Standards