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Josua P. Meyer - One of the best experts on this subject based on the ideXlab platform.
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A Review of Flow Pattern-Based Predictive Correlations during Refrigerant Condensation in Horizontally Smooth and Enhanced Tubes
Heat Transfer Engineering, 2008Co-Authors: Leon Liebenberg, Josua P. MeyerAbstract:A state-of-the-art review of recent work on flow pattern-based predictive correlations during Refrigerant Condensation in horizontally smooth and enhanced tubes is presented. The review focuses primarily on correlations for heat transfer coefficient and pressure drop during flow Condensation that ignored flow regime effects and treated flows as either annular or non-stratified flow, or as stratified flow. This resulted in correlations of poor accuracy and limited validity and reliability. Current heat transfer coefficient, pressure drop, and void fraction models are based on the local flow pattern, resulting in deviations of around 20% from experimental data. There are, however, several inconsistencies and anomalies regarding these models that are addressed in this paper. A generalized solution methodology for two-phase flow problems still remains an elusive goal, mainly because gas-liquid flow systems combine the complexities of turbulence with those of deformable vapor-liquid interfaces. The paper focus...
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Refrigerant Condensation Flow Regimes in Enhanced Tubes and Their Effect on Heat Transfer Coefficients and Pressure Drops
Heat Transfer Engineering, 2008Co-Authors: Leon Liebenberg, Josua P. MeyerAbstract:Flow regimes influence the heat and mass transfer processes during two-phase flow, implying that any statistically accurate and reliable prediction of heat transfer and pressure drop during flow Condensation should be based on the analysis of the prevailing flow pattern. Many correlations for heat transfer coefficient and pressure drop during flow Condensation completely ignored flow regime effects and treated flows as either annular or non-stratified flow or as stratified flow. This resulted in correlations of poor accuracy and limited validity and reliability. Current heat transfer coefficient, pressure drop, and void fraction models are based on the local flow pattern, though, resulting in deviations of around 20% from experimental data. There are, however, several inconsistencies and anomalies regarding these models, which are discussed in this paper. A generalized solution methodology for two-phase flow problems still remains an elusive goal, mainly because gas-liquid flow systems combine the complex...
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heat transfer pressure drop and flow pattern recognition during Condensation inside smooth helical micro fin and herringbone tubes
International Journal of Refrigeration-revue Internationale Du Froid, 2007Co-Authors: Jonathan Olivier, Leon Liebenberg, John R. Thome, Josua P. MeyerAbstract:Abstract This paper presents a study of flow regimes, pressure drops, and heat transfer coefficients during Refrigerant Condensation inside a smooth, an 18° helical micro-fin, and a herringbone tubes. Experimental work was conducted for condensing Refrigerants R-22, R-407C, and R-134a at an average saturation temperature of 40 °C with mass fluxes ranging from 400 to 800 kg m −2 s −1 , and with vapour qualities ranging from 0.85 to 0.95 at condenser inlet and from 0.05 to 0.15 at condenser outlet. These test conditions represent annular and intermittent (slug and plug) flow conditions. Results showed that transition from annular flow to intermittent flow, on average for the three Refrigerants, occurred at a vapour quality of 0.49 for the smooth tube, 0.29 for the helical micro-fin tube, and 0.26 for the herringbone tube. These transition vapour qualities were also reflected in the pressure gradients, with the herringbone tube having the highest pressure gradient. The pressure gradients encountered in the herringbone tube were about 79% higher than that of the smooth tube and about 27% higher than that of the helical micro-fin tube. A widely used pressure drop correlation for Condensation in helical micro-fin tubes was modified for the case of the herringbone tube. The modified correlation predicted the data within a 1% error with an absolute deviation of 7%. Heat transfer enhancement factors for the herringbone tube against the smooth tube were on average 70% higher while against the helical micro-fin tube it was 40% higher. A correlation for predicting heat transfer coefficients inside a helical micro-fin tube was modified for the herringbone tube. On average the correlation predicted the data to within 4% with an average standard deviation of 8%.
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Flow pattern-based heat transfer correlation for condensing R-22 in a smooth tube
2007Co-Authors: M. Christians-lupi, Eugene Van Rooyen, Leon Liebenberg, Josua P. MeyerAbstract:This paper presents a study of probabilistic flow regime-based heat transfer coefficients during Refrigerant Condensation inside a smooth tube. Experimental work was conducted using Refrigerant R-22, at an average saturation temperature of 40 o C, with mass fluxes ranging from 250650 kg/m 2 s, and with test section inlet vapor qualities ranging from 0.65 down to 0.10. These tests conditions represent mostly Intermittent flow, with some data points in the Annular and Stratified-wavy flow regimes. Utilizing time fraction data gathered in this experimental setup, a new time fraction-corrected flow regime-based heat transfer correlation, heavily based on the Thome et al. (J.R. Thome, J. El Hajal and A. Cavallini, Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, International Journal of Heat and Mass Transfer, 46:3365-3387, 2003) correlation was developed for use in the Intermittent flow regime. The modified correlation predicted the experimental data with a mean absolute deviation of 10%.
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In-tube passive heat transfer enhancement in the process industry
Applied Thermal Engineering, 2007Co-Authors: Leon Liebenberg, Josua P. MeyerAbstract:Abstract Enhanced heat transfer surfaces are used in heat exchangers to improve performance and to decrease system volume and cost. In-tube heat transfer enhancement usually takes the form of either micro-fin tubes (of the helical micro-fin or herringbone varieties), or of helical wire inserts. Despite a substantial increase in heat transfer, these devices also cause non-negligible pressure drops. By making use of well-proven flow pattern maps for smooth tubes and the new ones for smooth and enhanced tubes, it is shown from the Refrigerant Condensation data that flow patterns have a strong influence on heat transfer and pressure drop. This is done for data obtained from in-tube Condensation experiments for mass fluxes ranging from 300 to 800 kg/m 2 s at a saturation temperature of 40 °C, for Refrigerants R-22, R-134a, and R-407C. The flow regimes, pressure drops, heat transfer coefficients, and the overall performance of three different tubes, namely a smooth-, 18° helical micro-fin-, and a herringbone micro-fin tube (each having a nominal diameter of 9.51 mm), are presented and compared to the performance of smooth tubes with helical wire inserts (with pitches of 5 mm, 7.77 mm and 11 mm corresponding to helical angles of 78.2°, 72°, and 65.3°, respectively).
Leon Liebenberg - One of the best experts on this subject based on the ideXlab platform.
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A Review of Flow Pattern-Based Predictive Correlations during Refrigerant Condensation in Horizontally Smooth and Enhanced Tubes
Heat Transfer Engineering, 2008Co-Authors: Leon Liebenberg, Josua P. MeyerAbstract:A state-of-the-art review of recent work on flow pattern-based predictive correlations during Refrigerant Condensation in horizontally smooth and enhanced tubes is presented. The review focuses primarily on correlations for heat transfer coefficient and pressure drop during flow Condensation that ignored flow regime effects and treated flows as either annular or non-stratified flow, or as stratified flow. This resulted in correlations of poor accuracy and limited validity and reliability. Current heat transfer coefficient, pressure drop, and void fraction models are based on the local flow pattern, resulting in deviations of around 20% from experimental data. There are, however, several inconsistencies and anomalies regarding these models that are addressed in this paper. A generalized solution methodology for two-phase flow problems still remains an elusive goal, mainly because gas-liquid flow systems combine the complexities of turbulence with those of deformable vapor-liquid interfaces. The paper focus...
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Refrigerant Condensation Flow Regimes in Enhanced Tubes and Their Effect on Heat Transfer Coefficients and Pressure Drops
Heat Transfer Engineering, 2008Co-Authors: Leon Liebenberg, Josua P. MeyerAbstract:Flow regimes influence the heat and mass transfer processes during two-phase flow, implying that any statistically accurate and reliable prediction of heat transfer and pressure drop during flow Condensation should be based on the analysis of the prevailing flow pattern. Many correlations for heat transfer coefficient and pressure drop during flow Condensation completely ignored flow regime effects and treated flows as either annular or non-stratified flow or as stratified flow. This resulted in correlations of poor accuracy and limited validity and reliability. Current heat transfer coefficient, pressure drop, and void fraction models are based on the local flow pattern, though, resulting in deviations of around 20% from experimental data. There are, however, several inconsistencies and anomalies regarding these models, which are discussed in this paper. A generalized solution methodology for two-phase flow problems still remains an elusive goal, mainly because gas-liquid flow systems combine the complex...
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heat transfer pressure drop and flow pattern recognition during Condensation inside smooth helical micro fin and herringbone tubes
International Journal of Refrigeration-revue Internationale Du Froid, 2007Co-Authors: Jonathan Olivier, Leon Liebenberg, John R. Thome, Josua P. MeyerAbstract:Abstract This paper presents a study of flow regimes, pressure drops, and heat transfer coefficients during Refrigerant Condensation inside a smooth, an 18° helical micro-fin, and a herringbone tubes. Experimental work was conducted for condensing Refrigerants R-22, R-407C, and R-134a at an average saturation temperature of 40 °C with mass fluxes ranging from 400 to 800 kg m −2 s −1 , and with vapour qualities ranging from 0.85 to 0.95 at condenser inlet and from 0.05 to 0.15 at condenser outlet. These test conditions represent annular and intermittent (slug and plug) flow conditions. Results showed that transition from annular flow to intermittent flow, on average for the three Refrigerants, occurred at a vapour quality of 0.49 for the smooth tube, 0.29 for the helical micro-fin tube, and 0.26 for the herringbone tube. These transition vapour qualities were also reflected in the pressure gradients, with the herringbone tube having the highest pressure gradient. The pressure gradients encountered in the herringbone tube were about 79% higher than that of the smooth tube and about 27% higher than that of the helical micro-fin tube. A widely used pressure drop correlation for Condensation in helical micro-fin tubes was modified for the case of the herringbone tube. The modified correlation predicted the data within a 1% error with an absolute deviation of 7%. Heat transfer enhancement factors for the herringbone tube against the smooth tube were on average 70% higher while against the helical micro-fin tube it was 40% higher. A correlation for predicting heat transfer coefficients inside a helical micro-fin tube was modified for the herringbone tube. On average the correlation predicted the data to within 4% with an average standard deviation of 8%.
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Flow pattern-based heat transfer correlation for condensing R-22 in a smooth tube
2007Co-Authors: M. Christians-lupi, Eugene Van Rooyen, Leon Liebenberg, Josua P. MeyerAbstract:This paper presents a study of probabilistic flow regime-based heat transfer coefficients during Refrigerant Condensation inside a smooth tube. Experimental work was conducted using Refrigerant R-22, at an average saturation temperature of 40 o C, with mass fluxes ranging from 250650 kg/m 2 s, and with test section inlet vapor qualities ranging from 0.65 down to 0.10. These tests conditions represent mostly Intermittent flow, with some data points in the Annular and Stratified-wavy flow regimes. Utilizing time fraction data gathered in this experimental setup, a new time fraction-corrected flow regime-based heat transfer correlation, heavily based on the Thome et al. (J.R. Thome, J. El Hajal and A. Cavallini, Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, International Journal of Heat and Mass Transfer, 46:3365-3387, 2003) correlation was developed for use in the Intermittent flow regime. The modified correlation predicted the experimental data with a mean absolute deviation of 10%.
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In-tube passive heat transfer enhancement in the process industry
Applied Thermal Engineering, 2007Co-Authors: Leon Liebenberg, Josua P. MeyerAbstract:Abstract Enhanced heat transfer surfaces are used in heat exchangers to improve performance and to decrease system volume and cost. In-tube heat transfer enhancement usually takes the form of either micro-fin tubes (of the helical micro-fin or herringbone varieties), or of helical wire inserts. Despite a substantial increase in heat transfer, these devices also cause non-negligible pressure drops. By making use of well-proven flow pattern maps for smooth tubes and the new ones for smooth and enhanced tubes, it is shown from the Refrigerant Condensation data that flow patterns have a strong influence on heat transfer and pressure drop. This is done for data obtained from in-tube Condensation experiments for mass fluxes ranging from 300 to 800 kg/m 2 s at a saturation temperature of 40 °C, for Refrigerants R-22, R-134a, and R-407C. The flow regimes, pressure drops, heat transfer coefficients, and the overall performance of three different tubes, namely a smooth-, 18° helical micro-fin-, and a herringbone micro-fin tube (each having a nominal diameter of 9.51 mm), are presented and compared to the performance of smooth tubes with helical wire inserts (with pitches of 5 mm, 7.77 mm and 11 mm corresponding to helical angles of 78.2°, 72°, and 65.3°, respectively).
Brian M. Fronk - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of in-tube Condensation of low GWP Refrigerant R450A using a fiber optic distributed temperature sensor
International Journal of Refrigeration-revue Internationale Du Froid, 2019Co-Authors: Tabeel A. Jacob, Ethan P. Matty, Brian M. FronkAbstract:Abstract Heat transfer coefficients and frictional pressure drop values are experimentally measured during Condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for a range of mass fluxes (100 kg m − 2 s − 1 to 550 kg m − 2 s − 1 ) and saturation conditions (45 ∘ C and 55 ∘ C). The measured pressure drop values and heat transfer coefficients were compared with established literature correlations. Good agreement indicates that existing correlations can be used for design of condensers with R450A as the working fluid. Additionally, this study evaluates the viability of using distributed fiber optic temperature sensors during Refrigerant Condensation experiments. The fiber sensor is installed in the annulus of a tube-in-tube heat exchanger and is used to obtain the axial temperature profile of the cooling water. The measurements from the distributed temperature sensors are compared with conventional RTD measurements co-located within the test section. The results (Average Deviation = ±0.26 ∘ C, Maximum Deviation = ±1.11 ∘ C) suggest that fiber optic measurement techniques can provide temperature data with accuracy and high spatial resolution (equal to 0.65 mm).
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Experimental investigation of in-tube Condensation of low GWP Refrigerant R450A using a fiber optic distributed temperature sensor
International Journal of Refrigeration-revue Internationale Du Froid, 2019Co-Authors: Tabeel A. Jacob, Ethan P. Matty, Brian M. FronkAbstract:Abstract Heat transfer coefficients and frictional pressure drop values are experimentally measured during Condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for a range of mass fluxes (100 kg m − 2 s − 1 to 550 kg m − 2 s − 1 ) and saturation conditions (45 ∘ C and 55 ∘ C). The measured pressure drop values and heat transfer coefficients were compared with established literature correlations. Good agreement indicates that existing correlations can be used for design of condensers with R450A as the working fluid. Additionally, this study evaluates the viability of using distributed fiber optic temperature sensors during Refrigerant Condensation experiments. The fiber sensor is installed in the annulus of a tube-in-tube heat exchanger and is used to obtain the axial temperature profile of the cooling water. The measurements from the distributed temperature sensors are compared with conventional RTD measurements co-located within the test section. The results (Average Deviation = ±0.26 ∘ C, Maximum Deviation = ±1.11 ∘ C) suggest that fiber optic measurement techniques can provide temperature data with accuracy and high spatial resolution (equal to 0.65 mm).
Tabeel A. Jacob - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of in-tube Condensation of low GWP Refrigerant R450A using a fiber optic distributed temperature sensor
International Journal of Refrigeration-revue Internationale Du Froid, 2019Co-Authors: Tabeel A. Jacob, Ethan P. Matty, Brian M. FronkAbstract:Abstract Heat transfer coefficients and frictional pressure drop values are experimentally measured during Condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for a range of mass fluxes (100 kg m − 2 s − 1 to 550 kg m − 2 s − 1 ) and saturation conditions (45 ∘ C and 55 ∘ C). The measured pressure drop values and heat transfer coefficients were compared with established literature correlations. Good agreement indicates that existing correlations can be used for design of condensers with R450A as the working fluid. Additionally, this study evaluates the viability of using distributed fiber optic temperature sensors during Refrigerant Condensation experiments. The fiber sensor is installed in the annulus of a tube-in-tube heat exchanger and is used to obtain the axial temperature profile of the cooling water. The measurements from the distributed temperature sensors are compared with conventional RTD measurements co-located within the test section. The results (Average Deviation = ±0.26 ∘ C, Maximum Deviation = ±1.11 ∘ C) suggest that fiber optic measurement techniques can provide temperature data with accuracy and high spatial resolution (equal to 0.65 mm).
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Experimental investigation of in-tube Condensation of low GWP Refrigerant R450A using a fiber optic distributed temperature sensor
International Journal of Refrigeration-revue Internationale Du Froid, 2019Co-Authors: Tabeel A. Jacob, Ethan P. Matty, Brian M. FronkAbstract:Abstract Heat transfer coefficients and frictional pressure drop values are experimentally measured during Condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for a range of mass fluxes (100 kg m − 2 s − 1 to 550 kg m − 2 s − 1 ) and saturation conditions (45 ∘ C and 55 ∘ C). The measured pressure drop values and heat transfer coefficients were compared with established literature correlations. Good agreement indicates that existing correlations can be used for design of condensers with R450A as the working fluid. Additionally, this study evaluates the viability of using distributed fiber optic temperature sensors during Refrigerant Condensation experiments. The fiber sensor is installed in the annulus of a tube-in-tube heat exchanger and is used to obtain the axial temperature profile of the cooling water. The measurements from the distributed temperature sensors are compared with conventional RTD measurements co-located within the test section. The results (Average Deviation = ±0.26 ∘ C, Maximum Deviation = ±1.11 ∘ C) suggest that fiber optic measurement techniques can provide temperature data with accuracy and high spatial resolution (equal to 0.65 mm).
Ethan P. Matty - One of the best experts on this subject based on the ideXlab platform.
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Experimental investigation of in-tube Condensation of low GWP Refrigerant R450A using a fiber optic distributed temperature sensor
International Journal of Refrigeration-revue Internationale Du Froid, 2019Co-Authors: Tabeel A. Jacob, Ethan P. Matty, Brian M. FronkAbstract:Abstract Heat transfer coefficients and frictional pressure drop values are experimentally measured during Condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for a range of mass fluxes (100 kg m − 2 s − 1 to 550 kg m − 2 s − 1 ) and saturation conditions (45 ∘ C and 55 ∘ C). The measured pressure drop values and heat transfer coefficients were compared with established literature correlations. Good agreement indicates that existing correlations can be used for design of condensers with R450A as the working fluid. Additionally, this study evaluates the viability of using distributed fiber optic temperature sensors during Refrigerant Condensation experiments. The fiber sensor is installed in the annulus of a tube-in-tube heat exchanger and is used to obtain the axial temperature profile of the cooling water. The measurements from the distributed temperature sensors are compared with conventional RTD measurements co-located within the test section. The results (Average Deviation = ±0.26 ∘ C, Maximum Deviation = ±1.11 ∘ C) suggest that fiber optic measurement techniques can provide temperature data with accuracy and high spatial resolution (equal to 0.65 mm).
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Experimental investigation of in-tube Condensation of low GWP Refrigerant R450A using a fiber optic distributed temperature sensor
International Journal of Refrigeration-revue Internationale Du Froid, 2019Co-Authors: Tabeel A. Jacob, Ethan P. Matty, Brian M. FronkAbstract:Abstract Heat transfer coefficients and frictional pressure drop values are experimentally measured during Condensation of R134a and its proposed low global warming potential (GWP) replacement, R450A. R450A is a non-flammable zeotropic mixture of R134a and R1234ze (42/58% by mass). Experiments were conducted in a horizontal tube (ID = 4.7 mm) for a range of mass fluxes (100 kg m − 2 s − 1 to 550 kg m − 2 s − 1 ) and saturation conditions (45 ∘ C and 55 ∘ C). The measured pressure drop values and heat transfer coefficients were compared with established literature correlations. Good agreement indicates that existing correlations can be used for design of condensers with R450A as the working fluid. Additionally, this study evaluates the viability of using distributed fiber optic temperature sensors during Refrigerant Condensation experiments. The fiber sensor is installed in the annulus of a tube-in-tube heat exchanger and is used to obtain the axial temperature profile of the cooling water. The measurements from the distributed temperature sensors are compared with conventional RTD measurements co-located within the test section. The results (Average Deviation = ±0.26 ∘ C, Maximum Deviation = ±1.11 ∘ C) suggest that fiber optic measurement techniques can provide temperature data with accuracy and high spatial resolution (equal to 0.65 mm).