Condensation Heat Transfer and Pressure Drop of R-404A in 7.0 mm O.D. Smooth and Microfin Tube at Low Mass Fluxes

2018 ◽  
Vol 26 (01) ◽  
pp. 1850005 ◽  
Author(s):  
Nae-Hyun Kim ◽  
Hyung-Ho Gook ◽  
Byung-Moo Lee
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Mass Flux ◽  
Enhancement Factor ◽  
Condensation Heat Transfer ◽  
Transfer Enhancement ◽  
Mass Fluxes ◽  
Penalty Factor ◽  
Low Mass

R-404A condensation heat transfer and pressure drop data are provided for 7.0[Formula: see text]mm O.D. smooth and microfin tubes. Tests were conducted for a range of mass fluxes (from 80 to 200[Formula: see text]kg/m2s) and quality (from 0.2 to 0.8). The heat flux was 6[Formula: see text]kW/m2 and saturation temperature was 45[Formula: see text]C. It was found that both the heat transfer enhancement factor and the pressure drop penalty factor increase as mass flux increases. The range of pressure drop penalty factor (0.99–1.27) was smaller than that of heat transfer enhancement factor (1.21–1.96). Smooth tube heat transfer coefficients and pressure drops are reasonably predicted by Shah [An improved and extended general correlation for heat transfer during condensation in plain tubes, Int. J. HVAC&R Res. 15 (2009) 889–913] and Jung and Radermacher [Prediction of pressure drop during horizontal annular flow boiling of pure and mixed refrigerants, Int. J. Heat Mass Transfer 32 (1989) 2435–2446] correlation, respectively. For the microfin tube, however, all the existing correlations do not adequately predict the present data. Poor predictions may be attributed to the lack of R-404A and low mass flux data in their database.

CONDENSATION HEAT TRANSFER AND PRESSURE DROP OF R-410A IN A 5.0 MM O.D. SMOOTH AND MICROFIN TUBE

2013 ◽  
Vol 21 (03) ◽  
pp. 1350018 ◽  
Author(s):  
HO-WON BYUN ◽  
EUL-JONG LEE ◽  
YONG-SUP SIM ◽  
JEONG-KUN LEE ◽  
NAE-HYUN KIM
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Enhancement Factor ◽  
Saturation Temperature ◽  
Helix Angle ◽  
Apex Angle ◽  
Condensation Heat Transfer ◽  
Transfer Enhancement ◽  
Penalty Factor

R-410A condensation heat transfer and pressure drop data are provided for a 5.0 mm O.D. microfin tube having 40 fins with 18 degree helix angle and 40 degree fin apex angle. Tests were conducted for a range of quality (0.2 ~ 0.8), mass flux (346 ~ 692 kg/m2s) and saturation temperature (45 ~ 55°C). Data are compared with smooth tube counterpart. It was found that both heat transfer coefficient and pressure drop increased as mass flux increased. The range of pressure drop penalty factor (1.83 ~ 2.62) was slightly larger than that of heat transfer enhancement factor (1.24 ~ 1.66). Data are compared with available heat transfer and pressure drop correlations.

Condensation Pressure Drop and Heat Transfer in 5-mm-OD Micro-Fin Tubes

2012 ◽  
Author(s):  
Wei Li ◽  
Dan Huang ◽  
Zan Wu ◽  
Hong-Xia Li ◽  
Zhao-Yan Zhang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Heat Transfer Enhancement ◽  
Condensation Heat Transfer ◽  
Transfer Enhancement ◽  
Mass Fluxes ◽  
Fin Tubes ◽  
Condensation Heat Transfer Coefficient

An experimental investigation was performed for convective condensation of R410A inside four micro-fin tubes with the same outside diameter (OD) 5 mm and helix angle 18°. Data are for mass fluxes ranging from about 180 to 650 kg/m2s. The nominal saturation temperature is 320 K, with inlet and outlet qualities of 0.8 and 0.1, respectively. The results suggest that Tube 4 has the best thermal performance for its largest condensation heat transfer coefficient and relatively low pressure drop penalty. Condensation heat transfer coefficient decreases at first and then increases or flattens out gradually as G decreases. This complex mass-flux effect may be explained by the complex interactions between micro-fins and fluid. The heat transfer enhancement mechanism is mainly due to the surface area increase over the plain tube at large mass fluxes, while liquid drainage and interfacial turbulence play important roles in heat transfer enhancement at low mass fluxes. In addition, the experimental data was analyzed using seven existing pressure-drop and four heat-transfer models to verify their respective accuracies.

Heat Transfer Enhancement and Pressure Drop for R417A Flow Boiling in Internally Grooved Tubes

2011 ◽  
Vol 354-355 ◽  
pp. 732-738
Author(s):  
Xiao Yan Zhang
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Mass Flux ◽  
Flow Boiling ◽  
Enhancement Effect ◽  
Transfer Enhancement ◽  
Pressure Drops ◽  
Mass Fluxes ◽  
Enhancement Factors

An experimental investigation of evaporation for R417A in horizontal smooth and internally grooved tubes has been carried out. Based on the experimental results, performance of heat transfer and pressure drop for R417A flow boiling in different tubes was analyzed, and the influences of micro-fin parameters and mass fluxes on heat transfer enhancement factors and pressure drops were discussed. The results indicate: the enhancement effect of Tube III having the narrower spirally grooves excels than Tube II, and the enhancement factors increase with the increasing mass flux. R417A produces slightly bigger pressure drops in Tube II than Tube III, and the pressure drops increase with the increasing mass flux and vapor quality, this increase is more obvious in internally grooved tubes.

Thermal-Hydraulic Performance of R-134a Boiling at Low Mass Fluxes in a Small Vertical Brazed Plate Heat Exchanger

2017 ◽  
Author(s):  
Hyun Jin Kim ◽  
Leon Liebenberg ◽  
Anthony M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Nucleate Boiling ◽  
Plate Heat Exchanger ◽  
Two Phase ◽  
Mass Fluxes ◽  
Low Mass ◽  
Brazed Plate Heat Exchanger ◽  
R 134A

An experimental investigation was performed to study the heat transfer and pressure drop characteristics of refrigerant R-134a boiling in a chevron-patterned brazed plate heat exchanger (BPHE) at low mass flux. The heat transfer coefficient and pressure drop characteristics are analyzed in relation to 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 pressure drop shows a strong dependence on mass flux and significant saturation temperature drop at high mass flux. The two-phase heat transfer coefficient was both strongly dependent on heat flux (at vapor qualities below 0.4) and on mass flux (at vapor qualities above 0.4). There was also apparent dryout, as depicted by decreased heat transfer at high vapor qualities. These observations suggest that both nucleate and convective boiling mechanisms prevailed. Existing transition correlations however suggest that the experimental data is rather convection-dominant and not a mix of convection and nucleate boiling. The experimental data further strongly suggest the prevalence of both macrochannel and minichannel type flows. Several acknowledged semi-empirical transition criteria were employed to verify our observations. These criteria mostly support our observations that R-134a evaporating at low mass fluxes in a BPHE with a hydraulic diameter of 3.4 mm, has heat transfer and pressure drop characteristics typically indicative of macrochannel as well as minichannel flows. Disagreement however exists with accepted correlations regarding the prevalence of convective or nucleate boiling.

Effect of Inlet Restriction on Flow Boiling Heat Transfer in a Horizontal Microtube

2013 ◽  
Vol 135 (2) ◽  
Author(s):  
YanFeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Mass Fluxes ◽  
Flow Boiling Heat Transfer ◽  
Low Mass

Flow boiling heat transfer in a horizontal microtube with inlet restriction (orifice) under uniform heating condition is experimentally investigated using FC-72 as working fluid. A stainless steel microtube with an inner diameter of 889 μm is selected as main microtube. Two microtubes with smaller diameters are assembled at the inlet of main microtube to achieve the restriction ratios of 50% and 20%. The experimental measurement is carried out at mass fluxes ranging from 160 to 870 kg/m2·s, heat fluxes varying from 6 to 170 kW/m2, inlet temperatures of 23 and 35 °C, and saturation pressures of 10 and 45 kPa. The effects of the orifices on two-phase pressure drop, critical heat flux (CHF), and flow boiling heat transfer coefficient are studied. The results show that the pressure drop caused by the orifice takes a considerable portion in the total pressure drop at low mass fluxes. This ratio decreases as the vapor quality or mass flux increases. The difference of normal critical heat flux in the microtubes with different orifice sizes is negligible. In the aspect of flow boiling heat transfer, the orifice is able to enhance the heat transfer at low mass flux and high saturation pressure, which indicates the contribution of orifice in the nucleate boiling dominated regime. However, the effect of orifice on flow boiling heat transfer is negligible in the forced convective boiling dominated regime.

Numerical Analysis of Thermofluid Performance of Fin-and-Tube Heat Transfer Surface Using Rectangular Winglets

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Shailesh Kumar Sarangi ◽  
Dipti Prasad Mishra ◽  
Praveen Mishra
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Heat Transfer Enhancement ◽  
Enhancement Factor ◽  
Reynolds Numbers ◽  
Heat Transfer Surface ◽  
Major Influence ◽  
Transfer Enhancement ◽  
Maximum Enhancement ◽  
Streamwise Distance

AbstractThis paper numerically investigates the heat transfer enhancement using rectangular winglet pairs in a fin-and-tube type heat transfer surface having five inline rows of tubes. The influence of number of winglets, attack angles of the winglets, and their location has been analyzed under laminar flow conditions with Reynolds number ranging 400–1500. To account for the combined effect of heat transfer enhancement and pressure drop penalty, an enhancement factor is also discussed by changing the winglet pair's number and location. The numerical results show that pressure drop can be reduced significantly by placing the winglet more toward the exit of the flow channel. Streamwise distance and spanwise distance of the winglet pairs have been investigated for maximum enhancement factor. The numerically obtained results show that the winglets number and their placement at different locations have a major influence on enhancement factor. The results show that both the heat transfer and the pressure drop increase with an increase in attack angle of the winglets and best angle for the highest enhancement factor has been found out. Correlations have been developed for streamwise distance, spanwise distance, and angle of attack for different range of Reynolds numbers.

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