scholarly journals Pressure drop during evaporation of 1,1,1,2-tetrafluoroethane (R-134a)in a plate heat exchanger

2007 ◽  
Vol 72 (10) ◽  
pp. 1015-1022 ◽  
Author(s):  
Emila Djordjevic ◽  
Stephan Kabelac ◽  
Slobodan Serbanovic
Keyword(s):  
Heat Exchanger ◽  
Pressure Drop ◽  
Plate Heat Exchanger ◽  
Graphical Form ◽  
Vapor Quality ◽  
Two Phase ◽  
Plate Heat ◽  
Frictional Pressure Drop ◽  
The Mean ◽  
R 134A

Experimental results for the pressure drop during the evaporation of the refrigerant 1,1,1,2-tetrafluoroethane (R-134a) in a vertical plate heat exchanger are presented in this paper. The influences of mass flux, heat flux and vapor quality on the two-phase pressure drop are specially analyzed and compared with previously published experimental data and literature correlations. All results are given in graphical form as the dependency of the frictional pressure drop on the mean vapor quality. .

Evaporation Heat Transfer and Pressure Drop of Refrigerant R-134a in a Plate Heat Exchanger

1999 ◽  
Vol 121 (1) ◽  
pp. 118-127 ◽  
Author(s):  
Y.-Y. Yan ◽  
T.-F. Lin
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Plate Heat Exchanger ◽  
Vapor Quality ◽  
Plate Heat ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer ◽  
R 134A

The evaporation heat transfer coefficient and pressure drop for refrigerant R-134a flowing in a plate heat exchanger were investigated experimentally in this study. Two vertical counterflow channels were formed in the exchanger by three plates of commercial geometry with a corrugated sine shape of a chevron angle of 60 deg. Upflow boiling of refrigerant R-134a in one channel receives heat from the hot downflow of water in the other channel. The effects of the mean vapor quality, mass flux, heat flux, and pressure of R-134a on the evaporation heat transfer and pressure drop were explored. The quality change of R-134a between the inlet and outlet of the refrigerant channel ranges from 0.09 to 0.18. Even at a very low Reynolds number, the present flow visualization of evaporation in a plate heat exchanger with the transparent outer plate showed that the flow in the plate heat exchanger remains turbulent. It is found that the evaporation heat transfer coefficient of R-134a in the plates is much higher than that in circular pipes and shows a very different variation with the vapor quality from that in circular pipes, particularly in the convective evaporation dominated regime at high vapor quality. Relatively intense evaporation on the corrugated surface was seen from the flow visualization. Moreover, the present data showed that both the evaporation heat transfer coefficient and pressure drop increase with the vapor quality. At a higher mass flux the pressure drop is higher for the entire range of the vapor quality but the evaporation heat transfer is clearly better only at the high quality. Raising the imposed wall heat flux was found to slightly improve the heat transfer, while at a higher refrigerant pressure, both the heat transfer and pressure drop are slightly lower. Based on the present data, empirical correlations for the evaporation heat transfer coefficient and friction factor were proposed.

Heat transfer coefficient and pressure drop during refrigerant R-134a condensation in a plate heat exchanger

2008 ◽  
Vol 62 (1) ◽  
Author(s):  
Emila Djordjević ◽  
Stephan Kabelac ◽  
Slobodan Šerbanović
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Plate Heat Exchanger ◽  
Vapor Quality ◽  
Plate Heat ◽  
R 134A ◽  
The Heat Transfer Coefficient

AbstractThe condensation heat transfer coefficient and the two-phase pressure drop of refrigerant R-134a in a vertical plate heat exchanger were investigated experimentally. The area of the plate was divided into several segments along the vertical axis. For each of the segments, local values of the heat transfer coefficient and frictional pressure drop were calculated and presented as a function of the mean vapor quality in the segment. Owing to the thermocouples installed along the plate surface, it was possible to determine the temperature distribution and vapor quality profile inside the plate. The influences of the mass flux and the heat flux on the heat transfer coefficient and the pressure drop were also taken into account and a comparison with previously published experimental data and literature correlations was carried out.

scholarly journals Mean heat transfer coefficients during the evaporation of 1,1,1,2-tetrafluoroethane (R-134a) in a plate heat exchanger

2007 ◽  
Vol 72 (8-9) ◽  
pp. 833-846 ◽  
Author(s):  
Emila Djordjevic ◽  
Stephan Kabelac ◽  
Slobodan Serbanovic
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Transfer Coefficient ◽  
Plate Heat Exchanger ◽  
Transfer Coefficients ◽  
Plate Heat ◽  
Evaporation Heat ◽  
The Mean ◽  
R 134A

In this study the transfer coefficient of evaporation heat of the refrigerant 1,1,1,2-tetrafluoroethane (R-134a) in a vertical plate heat exchanger was experimentally investigated. The results are presented as the dependancy of the mean heat transfer coefficient for the whole heat exchanger on the mean vapor quality. The influences of mass flux, heat flux and flow configuration on the heat transfer coefficient were also taken into account and a comparison with previously published experimental data and literature correlations was made. .

Convective Boiling of R-134a Near the Micro-Macroscale Transition Inside a Vertical Brazed Plate Heat Exchanger

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Hyun Jin Kim ◽  
Leon Liebenberg ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Mass Flux ◽  
Saturation Pressure ◽  
Plate Heat Exchanger ◽  
Vapor Quality ◽  
Two Phase ◽  
Convective Boiling ◽  
Brazed Plate Heat Exchanger ◽  
R 134A

Heat transfer and pressure drop characteristics of R-134a boiling in a chevron-patterned brazed plate heat exchanger (BPHE) are studied experimentally. With corrugated BPHE channels having hydraulic diameter of 3.4 mm and low refrigerant mass flux, boiling near the micro-macroscale transition is speculated. Heat exchanger performance is characterized with varying mass flux (30–50 kgm−2s−1), saturation pressure (675 kPa and 833 kPa), heat flux (0.8 and 2.5 kWm−2), and vapor quality (0.1–0.9). The two-phase refrigerant heat transfer coefficient increases with heat flux as often observed during nucleate boiling. It also weakly increases with saturation pressure and the associated lower latent heat during convective boiling; heat transfer is improved by the decreased liquid film thickness surrounding confined bubbles inside the narrow BPHE channels, which is the main characteristic of microscale boiling. As often observed in macroscale boiling, the inertial forces of the liquid and vapor phases cause an unsteady annular film, leading to premature partial dryout. The onset of dryout is accelerated at the lower saturation pressure, due to increased surface tension, another microscale-like characteristic. Higher surface tension retains liquid in sharp corners of the corrugated channel, leaving lateral surface areas of the wall dry. Two-phase pressure drop increases with mass flux and vapor quality, but with decreasing saturation pressure. Dryout decreases the friction factor due to the much lower viscosity of the gas phase in contact with the wall. Several semi-empirical transition criteria and correlations buttress the current analyses that the thermal-fluidic characteristics peculiar to BPHEs might be due to macro-microscale transition in boiling.

scholarly journals Numerical and Experimental Study of Air-to-Air Plate Heat Exchangers with Plain and Offset Strip Fin Shapes

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5710
Author(s):  
Kyung Rae Kim ◽  
Jae Keun Lee ◽  
Hae Do Jeong ◽  
Yul Ho Kang ◽  
Young Chull Ahn
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Predictive Model ◽  
Plate Heat Exchanger ◽  
Experimental Results ◽  
Plate Heat ◽  
Frictional Pressure Drop ◽  
The Difference ◽  
Control Volumes

This study evaluates the performance of a plate heat exchanger numerically and experimentally. The predictive model for estimating the heat transfer and frictional pressure drop across the plain and offset strip fins is compared with the experimental results with the parameters of Reynolds number and fin pitch. The heat transfer of the offset fin shape is 13.4% higher than that of the plain fin in the experiment in the case of Re = 6112 for the hot airflow and Re = 2257 for the cold airflow. A predictive model uses the effectiveness-Number of Transfer Units (NTU) method with the discretization in the segments divided into small control volumes in the heat exchanger. The difference of heat transfer and pressure drop for the plain fin between the numerical and the experimental results are approximately 1.9% and 5.9%, respectively. Thus, the results indicate that the predictive model for estimating the heat transfer is useful for evaluating the performance of the plate heat exchanger in the laminar-to-transition regions.

scholarly journals Evaporation Heat Transfer and Pressure Drop of Refrigerant R134a in a Plate Heat Exchanger

1997 ◽  
Author(s):  
Yi-Yie Yan ◽  
Tsing-Fa Lin ◽  
Bing-Chwen Yang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Plate Heat Exchanger ◽  
Vapor Quality ◽  
Plate Heat ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer

The characteristics of evaporation heat transfer and pressure drop for refrigerant R134a flowing in a plate heat exchanger were investigated experimentally in this study. Two vertical counter flow channels were formed in the exchanger by three plates of commercialized geometry with a corrugated sine shape of a chevron angle of 60°. Upflow boiling of refrigerant R134a in one channel receives heat from the hot downflow of water in the other channel. The effects of the heat flux, mass flux, quality and pressure of R134a on the evaporation heat transfer and pressure drop were explored. The preliminary measured data for the water to water single phase convection showed that the heat transfer coefficient in the plate heat exchanger is about 9 times of that in a circular pipe at the same Reynolds number. Even at a very low Reynolds number, the present flow visualization in a plate heat exchanger with the transparent outer plate showed that the flow in the plate heat exchanger remains turbulent. Data for the pressure drop were also examined in detail. It is found that the evaporation heat transfer coefficient of R134a in the plates is quite different from that in circular pipe, particularly in the convective evaporation dominated regime at high vapor quality. Relatively intense boiling on the corrugated surface was seen from the flow visualization. More specifically, the present data showed that both the evaporation heat transfer coefficient and pressure drop increase with the vapor quality. At a higher mass flux the pressure drop is higher for the entire range of the vapor quality but the heat transfer is only better at high quality. Raising the imposed wall heat flux was found to slightly improve the heat transfer. While at a higher system pressure the heat transfer and pressure drop are both slightly lower.

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