Void Fraction

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Pega Hrnjak - One of the best experts on this subject based on the ideXlab platform.

  • design and calibration of capacitive sensors for measuring Void Fraction in vertical headers of microchannel heat exchangers
    International Journal of Refrigeration-revue Internationale Du Froid, 2021
    Co-Authors: Hongliang Qian, Pega Hrnjak
    Abstract:

    Abstract This paper presents new capacitive sensors built and calibrated to measure cross-sectional Void Fraction between tubes in vertical headers of microchannel heat exchangers (MCHEs). Eleven individual sensors are assembled into one test header to measure local capacitance independently in real-time. A calibration procedure based on visualization, pressure drop, signal patterns, and mass measurement (quick-closing valve technique, QCV) is proposed. After the calibration, most Void Fraction data predicted by all eleven sensors fall into ±10% deviations of the experimental results by QCV. The sensors are ready to be utilized to measure local Void Fraction along vertical inlet or intermediate headers of MCHEs in future studies.

  • mass measurement based calibration of a capacitive sensor to measure Void Fraction for r134a in smooth tubes
    International Journal of Refrigeration-revue Internationale Du Froid, 2020
    Co-Authors: Hongliang Qian, Pega Hrnjak
    Abstract:

    Abstract This paper presents a new capacitive sensor built and used to measure Void Fraction of both horizontal and vertical upward flow in the low mass flux range in circular tubes with an inner diameter of 7 mm. Three sensors with different axial lengths (D, 2D/3, and D/2) are built and evaluated to examine the possibility of utilizing shorter sensors in applications with space limitations. Results show all three sensors have the capability to measure Void Fraction. Due to the nonlinear relation between capacitive signals and Void Fraction, a calibration procedure based on mass measurement (quick-closing valve technique, QCV) is proposed. After the calibration procedure, most Void Fraction data measured by the sensor falls into the ±15% deviations of the experimental results by QCV for horizontal flow and ±10% for vertical upward flow. Sensors with the same design can be utilized directly to measure Void Fraction for the similar test conditions in the future studies.

  • Void Fraction measurement and flow regimes visualization of r134a in horizontal and vertical id 7 mm circular tubes
    International Journal of Refrigeration-revue Internationale Du Froid, 2019
    Co-Authors: Hongliang Qian, Pega Hrnjak
    Abstract:

    Abstract Flow regimes and Void Fraction in horizontal and vertical round smooth tubes ID 7 mm with R134a in the adiabatic conditions (saturation temperature at 33 °C) and low mass flux (40–150 kg/m2 s for horizontal tubes and 65–115 kg/m2 s for vertical tubes) are presented in this paper. Flow regimes are captured by a high-speed camera while Void Fraction is measured by quick-closing valve method. The horizontal flow patterns are compared to Wojtan et al. (2005a) flow-regime map and some modifications based on visualization results are proposed. Void Fraction results for both horizontal and vertical flows are compared to some widely used correlations. Influences of tube orientation and mass flux on Void Fraction are discussed. When the vapor quality keeps constant, Void Fraction of horizontal tubes is larger than that of vertical tubes. Higher mass flux also results in larger Void Fraction compared that of lower mass flux.

Suresh V Garimella - One of the best experts on this subject based on the ideXlab platform.

  • Design of a non-intrusive electrical impedance-based Void Fraction sensor for microchannel two-phase flows
    Measurement Science and Technology, 2014
    Co-Authors: P. Valiorgue, Susan N Ritchey, Justin A. Weibel, Suresh V Garimella
    Abstract:

    A non-intrusive electrical impedance-based sensor is developed for measurement of local Void Fraction in air–water adiabatic flow through rectangular microchannels. Measurement of the Void Fraction in microchannels is essential for the formulation of two-phase flow heat transfer and pressure drop correlations, and may enable real-time flow regime control and performance prediction in the thermal regulation of high-heat-flux devices. The impedance response of the sensor to a range of flow regimes is investigated for a configuration with two aligned electrodes flush-mounted on opposing microchannel walls. Numerical simulations performed on a multi-phase domain constructed from three-dimensional reconstruction of experimentally observed phase boundaries along with the corresponding experimental results serve to establish the relationship between Void Fraction and dimensionless impedance for this geometric configuration. A reduced-order analytical model developed based on an assumption of stratified gas–liquid flow allows ready extension of these calibration results to different working fluids of interest.

  • electrical impedance based Void Fraction measurement and flow regime identification in microchannel flows under adiabatic conditions
    International Journal of Multiphase Flow, 2012
    Co-Authors: Sidharth Paranjape, Susan N Ritchey, Suresh V Garimella
    Abstract:

    Abstract Electrical impedance of a two-phase mixture is a function of Void Fraction and phase distribution. The difference in the specific electrical conductance and permittivity of the two phases is exploited to measure electrical impedance for obtaining Void Fraction and flow regime characteristics. An electrical impedance meter is constructed for the measurement of Void Fraction in microchannel two-phase flow. The experiments are conducted in air–water two-phase flow under adiabatic conditions. A transparent acrylic test section of hydraulic diameter 780 μm is used in the experimental investigation. The impedance Void meter is calibrated against the Void Fraction calculated using analysis of images obtained with a high-speed camera. Based on these measurements, a methodology utilizing the statistical characteristics of the Void Fraction signals is employed for identification of microchannel flow regimes. A self-organizing neural network is used for classification of the flow regimes.

Baoliang Wang - One of the best experts on this subject based on the ideXlab platform.

  • a new contactless impedance sensor for Void Fraction measurement of gas liquid two phase flow
    Measurement Science and Technology, 2016
    Co-Authors: Ya Chang, Zhiyao Huang, Baoliang Wang
    Abstract:

    With impedance elimination principle and phase sensitive demodulation (PSD) technique, this work aims to develop a new contactless impedance sensor, which is suitable for the Void Fraction measurement of gas–liquid two-phase flow. The impedance elimination principle is used to overcome the unfavorable influences of the coupling capacitances, i.e. the capacitive reactances of the coupling capacitances are eliminated by the inductive reactance of an introduced inductor. PSD technique is used to implement the impedance measurement. Unlike the conventional conductance/impedance sensors which use the equivalent conductance (the real part of the impedance) or the amplitude of the impedance of gas–liquid two-phase flow, the new contactless impedance sensor makes full use of the total impedance information of gas–liquid two-phase flow (including the amplitude, the real part and the imaginary part of the impedance, especially the imaginary part) to implement the Void Fraction measurement. As a preliminary study, to verify the effectiveness of the new contactless impedance sensor, two prototypes (with different inner diameters of 17.0 mm and 22.0 mm) are developed and experiments are carried out. Two typical flow patterns (bubble flow and stratified flow) of gas–liquid two-phase flow are investigated. The experimental results show that the new contactless impedance sensor is successful and effective. Compared with the conventional conductance/impedance sensors, the new contactless impedance sensor can aVoid polarization effect and electrochemical erosion effect. The total impedance information is used and the Void Fraction measurement performance of the new sensor is satisfactory. The experimental results also indicate that the imaginary part of the impedance of gas–liquid two-phase flow is very useful for the Void Fraction measurement. Making full use of the total impedance information of gas–liquid two-phase flow can effectively improve the Void Fraction measurement accuracy.

  • a new Void Fraction measurement method for gas liquid two phase flow in small channels
    Sensors, 2016
    Co-Authors: Zhiyao Huang, Baoliang Wang
    Abstract:

    Based on a laser diode, a 12 × 6 photodiode array sensor, and machine learning techniques, a new Void Fraction measurement method for gas-liquid two-phase flow in small channels is proposed. To overcome the influence of flow pattern on the Void Fraction measurement, the flow pattern of the two-phase flow is firstly identified by Fisher Discriminant Analysis (FDA). Then, according to the identification result, a relevant Void Fraction measurement model which is developed by Support Vector Machine (SVM) is selected to implement the Void Fraction measurement. A Void Fraction measurement system for the two-phase flow is developed and experiments are carried out in four different small channels. Four typical flow patterns (including bubble flow, slug flow, stratified flow and annular flow) are investigated. The experimental results show that the development of the measurement system is successful. The proposed Void Fraction measurement method is effective and the Void Fraction measurement accuracy is satisfactory. Compared with the conventional laser measurement systems using standard laser sources, the developed measurement system has the advantages of low cost and simple structure. Compared with the conventional Void Fraction measurement methods, the proposed method overcomes the influence of flow pattern on the Void Fraction measurement. This work also provides a good example of using low-cost laser diode as a competent replacement of the expensive standard laser source and hence implementing the parameter measurement of gas-liquid two-phase flow. The research results can be a useful reference for other researchers’ works.

  • application of electrical capacitance tomography to the Void Fraction measurement of two phase flow
    IEEE Transactions on Instrumentation and Measurement, 2003
    Co-Authors: Zhiyao Huang, Baoliang Wang, Haiqing Li
    Abstract:

    Based on the electrical capacitance tomography technique, a new method for the Void Fraction measurement of two-phase flow is proposed. A 12-electrode Void Fraction measurement system is established. A mathematical model of image reconstruction of electrical capacitance tomography is developed. To obtain the quantitative information of two-phase flow, combining the Tikhonov regularization principle and the algebraic reconstruction technique algorithm, a new image reconstruction algorithm is presented. The experimental results show that the accuracy of Void Fraction measurement is satisfactory. The proposed method is suitable for the Void Fraction measurement of many kinds of two-phase flow.

  • application of electrical capacitance tomography to the Void Fraction measurement of two phase flow
    Instrumentation and Measurement Technology Conference, 2001
    Co-Authors: Zhiyao Huang, Baoliang Wang, Haiqing Li
    Abstract:

    Based on electrical capacitance tomography technique, a new method for the Void Fraction measurement of two-phase flow is proposed. A Void function measurement system is established, A mathematical model of image reconstruction of electrical capacitance tomography is developed. To obtain the quantitative information of two-phase flow, a new image reconstruction algorithm is presented. The experimental results show that the accuracy of Void Fraction measurement is satisfactory. The proposed method is suitable for the Void Fraction measurement of many kinds of two-phase flow.

Zhiyao Huang - One of the best experts on this subject based on the ideXlab platform.

  • a new contactless impedance sensor for Void Fraction measurement of gas liquid two phase flow
    Measurement Science and Technology, 2016
    Co-Authors: Ya Chang, Zhiyao Huang, Baoliang Wang
    Abstract:

    With impedance elimination principle and phase sensitive demodulation (PSD) technique, this work aims to develop a new contactless impedance sensor, which is suitable for the Void Fraction measurement of gas–liquid two-phase flow. The impedance elimination principle is used to overcome the unfavorable influences of the coupling capacitances, i.e. the capacitive reactances of the coupling capacitances are eliminated by the inductive reactance of an introduced inductor. PSD technique is used to implement the impedance measurement. Unlike the conventional conductance/impedance sensors which use the equivalent conductance (the real part of the impedance) or the amplitude of the impedance of gas–liquid two-phase flow, the new contactless impedance sensor makes full use of the total impedance information of gas–liquid two-phase flow (including the amplitude, the real part and the imaginary part of the impedance, especially the imaginary part) to implement the Void Fraction measurement. As a preliminary study, to verify the effectiveness of the new contactless impedance sensor, two prototypes (with different inner diameters of 17.0 mm and 22.0 mm) are developed and experiments are carried out. Two typical flow patterns (bubble flow and stratified flow) of gas–liquid two-phase flow are investigated. The experimental results show that the new contactless impedance sensor is successful and effective. Compared with the conventional conductance/impedance sensors, the new contactless impedance sensor can aVoid polarization effect and electrochemical erosion effect. The total impedance information is used and the Void Fraction measurement performance of the new sensor is satisfactory. The experimental results also indicate that the imaginary part of the impedance of gas–liquid two-phase flow is very useful for the Void Fraction measurement. Making full use of the total impedance information of gas–liquid two-phase flow can effectively improve the Void Fraction measurement accuracy.

  • a new Void Fraction measurement method for gas liquid two phase flow in small channels
    Sensors, 2016
    Co-Authors: Zhiyao Huang, Baoliang Wang
    Abstract:

    Based on a laser diode, a 12 × 6 photodiode array sensor, and machine learning techniques, a new Void Fraction measurement method for gas-liquid two-phase flow in small channels is proposed. To overcome the influence of flow pattern on the Void Fraction measurement, the flow pattern of the two-phase flow is firstly identified by Fisher Discriminant Analysis (FDA). Then, according to the identification result, a relevant Void Fraction measurement model which is developed by Support Vector Machine (SVM) is selected to implement the Void Fraction measurement. A Void Fraction measurement system for the two-phase flow is developed and experiments are carried out in four different small channels. Four typical flow patterns (including bubble flow, slug flow, stratified flow and annular flow) are investigated. The experimental results show that the development of the measurement system is successful. The proposed Void Fraction measurement method is effective and the Void Fraction measurement accuracy is satisfactory. Compared with the conventional laser measurement systems using standard laser sources, the developed measurement system has the advantages of low cost and simple structure. Compared with the conventional Void Fraction measurement methods, the proposed method overcomes the influence of flow pattern on the Void Fraction measurement. This work also provides a good example of using low-cost laser diode as a competent replacement of the expensive standard laser source and hence implementing the parameter measurement of gas-liquid two-phase flow. The research results can be a useful reference for other researchers’ works.

  • application of electrical capacitance tomography to the Void Fraction measurement of two phase flow
    IEEE Transactions on Instrumentation and Measurement, 2003
    Co-Authors: Zhiyao Huang, Baoliang Wang, Haiqing Li
    Abstract:

    Based on the electrical capacitance tomography technique, a new method for the Void Fraction measurement of two-phase flow is proposed. A 12-electrode Void Fraction measurement system is established. A mathematical model of image reconstruction of electrical capacitance tomography is developed. To obtain the quantitative information of two-phase flow, combining the Tikhonov regularization principle and the algebraic reconstruction technique algorithm, a new image reconstruction algorithm is presented. The experimental results show that the accuracy of Void Fraction measurement is satisfactory. The proposed method is suitable for the Void Fraction measurement of many kinds of two-phase flow.

  • application of electrical capacitance tomography to the Void Fraction measurement of two phase flow
    Instrumentation and Measurement Technology Conference, 2001
    Co-Authors: Zhiyao Huang, Baoliang Wang, Haiqing Li
    Abstract:

    Based on electrical capacitance tomography technique, a new method for the Void Fraction measurement of two-phase flow is proposed. A Void function measurement system is established, A mathematical model of image reconstruction of electrical capacitance tomography is developed. To obtain the quantitative information of two-phase flow, a new image reconstruction algorithm is presented. The experimental results show that the accuracy of Void Fraction measurement is satisfactory. The proposed method is suitable for the Void Fraction measurement of many kinds of two-phase flow.

Hongliang Qian - One of the best experts on this subject based on the ideXlab platform.

  • design and calibration of capacitive sensors for measuring Void Fraction in vertical headers of microchannel heat exchangers
    International Journal of Refrigeration-revue Internationale Du Froid, 2021
    Co-Authors: Hongliang Qian, Pega Hrnjak
    Abstract:

    Abstract This paper presents new capacitive sensors built and calibrated to measure cross-sectional Void Fraction between tubes in vertical headers of microchannel heat exchangers (MCHEs). Eleven individual sensors are assembled into one test header to measure local capacitance independently in real-time. A calibration procedure based on visualization, pressure drop, signal patterns, and mass measurement (quick-closing valve technique, QCV) is proposed. After the calibration, most Void Fraction data predicted by all eleven sensors fall into ±10% deviations of the experimental results by QCV. The sensors are ready to be utilized to measure local Void Fraction along vertical inlet or intermediate headers of MCHEs in future studies.

  • mass measurement based calibration of a capacitive sensor to measure Void Fraction for r134a in smooth tubes
    International Journal of Refrigeration-revue Internationale Du Froid, 2020
    Co-Authors: Hongliang Qian, Pega Hrnjak
    Abstract:

    Abstract This paper presents a new capacitive sensor built and used to measure Void Fraction of both horizontal and vertical upward flow in the low mass flux range in circular tubes with an inner diameter of 7 mm. Three sensors with different axial lengths (D, 2D/3, and D/2) are built and evaluated to examine the possibility of utilizing shorter sensors in applications with space limitations. Results show all three sensors have the capability to measure Void Fraction. Due to the nonlinear relation between capacitive signals and Void Fraction, a calibration procedure based on mass measurement (quick-closing valve technique, QCV) is proposed. After the calibration procedure, most Void Fraction data measured by the sensor falls into the ±15% deviations of the experimental results by QCV for horizontal flow and ±10% for vertical upward flow. Sensors with the same design can be utilized directly to measure Void Fraction for the similar test conditions in the future studies.

  • Void Fraction measurement and flow regimes visualization of r134a in horizontal and vertical id 7 mm circular tubes
    International Journal of Refrigeration-revue Internationale Du Froid, 2019
    Co-Authors: Hongliang Qian, Pega Hrnjak
    Abstract:

    Abstract Flow regimes and Void Fraction in horizontal and vertical round smooth tubes ID 7 mm with R134a in the adiabatic conditions (saturation temperature at 33 °C) and low mass flux (40–150 kg/m2 s for horizontal tubes and 65–115 kg/m2 s for vertical tubes) are presented in this paper. Flow regimes are captured by a high-speed camera while Void Fraction is measured by quick-closing valve method. The horizontal flow patterns are compared to Wojtan et al. (2005a) flow-regime map and some modifications based on visualization results are proposed. Void Fraction results for both horizontal and vertical flows are compared to some widely used correlations. Influences of tube orientation and mass flux on Void Fraction are discussed. When the vapor quality keeps constant, Void Fraction of horizontal tubes is larger than that of vertical tubes. Higher mass flux also results in larger Void Fraction compared that of lower mass flux.