Condensation Heat Transfer and Pressure Drop of R-134a Flowing in Annular Helical Pipes at Different Orientations

2003 ◽  
Author(s):  
B. Yu ◽  
C. X. Lin ◽  
M. A. Ebadian ◽  
R. C. Prattipati
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Cooling Water ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Cooling Water Temperature ◽  
Helical Pipe ◽  
R 134A

This paper presents an experimental investigation of condensation heat transfer and pressure drop characteristics of refrigerant R-134a flowing through an annular helicoidal passage with the hydraulic diameter of 8.5 mm. The angles of helix axis are oriented at 0, 45, 90 degrees to gravity. The overall and refrigerant-side heat transfer coefficients and pressure drops are experimentally determined at saturation temperature 35°C, refrigerant mass flux 35–180 kg/s·m2, and cooling water temperature 27°C. The results show that orientation has significant influence on the thermal and hydraulic behaviors of the helical pipe. The results can be employed for reference in the effective design of annular helicoidal heat exchangers with R-134a as the working fluid.

Predicting Heat Transfer in Long R-134a Filled Thermosyphons

2009 ◽  
Vol 131 (5) ◽  
Author(s):  
M. H. M. Grooten ◽  
C. W. M. van der Geld
Keyword(s):  
Heat Transfer ◽  
Saturation Temperature ◽  
Good Alternative ◽  
Condensation Heat Transfer ◽  
Air Cooling ◽  
Transfer Coefficients ◽  
Reduced Pressure ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer ◽  
R 134A

When traditional air-to-air cooling is too voluminous, heat exchangers with long thermosyphons offer a good alternative. Experiments with a single thermosyphon with a large length-to-diameter ratio (188) and filled with R-134a are presented and analyzed. Saturation temperatures, filling ratios, and angles of inclination have been varied in wide ranges. A higher sensitivity of evaporation heat transfer coefficients on reduced pressure than in previous work has been found. Measurements revealed the effect of pressure or the saturation temperature on condensation heat transfer. The condensate film Reynolds number that marks a transition from one condensation heat transfer regime to another is found to depend on pressure. This effect was not accounted for by correlations from the literature. New correlations are presented to predict condensation and evaporation heat transfer rates.

Experimental Investigation of Condensation Heat Transfer and Adiabatic Pressure Drop Characteristics Inside a Microfin and Smooth Tube

2017 ◽  
Vol 25 (03) ◽  
pp. 1750027 ◽  
Author(s):  
M. Mostaqur Rahman ◽  
Keishi Kariya ◽  
Akio Miyara
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Frictional Pressure Drop

Experiments on condensation heat transfer and adiabatic pressure drop characteristics of R134a were performed inside smooth and microfin horizontal tubes. The tests were conducted in the mass flux range of 50[Formula: see text]kg/m2s to 200[Formula: see text]kg/m2s, vapor quality range of 0 to 1 and saturation temperature range of 20[Formula: see text]C to 35[Formula: see text]C. The effects of mass velocity, vapor quality, saturation temperature, and microfin on the condensation heat transfer and frictional pressure drop were analyzed. It was discovered that the local heat transfer coefficients and frictional pressure drop increases with increasing mass flux and vapor quality and decreasing with increasing saturation temperature. Higher heat transfer coefficient and frictional pressure drop in microfin tube were observed. The present experimental data were compared with the existing well-known condensation heat transfer and frictional pressure drop models available in the open literature. The condensation heat transfer coefficient and frictional pressure drop of R134a in horizontal microfin tube was predicted within an acceptable range by the existing correlation.

An Experimental Investigation of Condensation Heat Transfer Coefficients and Pressure Drops of Refrigerants Inside Multiport Mini-channel Tubes

2017 ◽  
Vol 25 (02) ◽  
pp. 1750013 ◽  
Author(s):  
Pham-Quang Vu ◽  
Kwang-Il Choi ◽  
Jong-Taek Oh ◽  
Honggi Cho
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Condensation Heat Transfer ◽  
Working Fluid ◽  
Vapor Quality ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Heat Transfer Coefficients

The condensation heat transfer coefficients and pressure drops of R410A and R22 flowing inside a horizontal aluminum multiport mini-channel tube having 18 channels are investigated. Experimental data are presented for the range of vapor quality from 0.1 to 0.9, mass flux from 50 to 500[Formula: see text]kg/m2s, heat flux from 3 to 15[Formula: see text]kW/m2 and the saturation temperature at 48[Formula: see text]C. The pressure drop across the test section was directly measured by a differential pressure transducer. At a small scale, the noncircular cross-sections can enhance the effect of the surface tension. The average heat transfer coefficient increased with the increase of vapor quality, mass flux and heat flux. Under the same test conditions, the heat transfer coefficients of R22 are higher than those for R410A, the pressure drops for R410A are 7–19% lower than those of R22. The lower pressure drop of R410A has an important advantage as an alternative working fluid for R22 in air-conditioning and heat pump systems.

scholarly journals A Comparative Study on the Condensation Heat Transfer of R-513A as an Alternative to R-134a

Machines ◽  
2021 ◽  
Vol 9 (6) ◽  
pp. 114
Author(s):  
Andreas Karageorgis ◽  
George Hinopoulos ◽  
Man-Hoe Kim
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Mass Flux ◽  
Condensation Heat Transfer ◽  
Test Facility ◽  
Condensation Temperature ◽  
Transfer Coefficients ◽  
Active Length ◽  
Heat Transfer Coefficients ◽  
R 134A

This paper presents the two-phase condensation heat transfer and pressure drop characteristics of R-513A as an alternative refrigerant to R-134a in a 9.52-mm OD horizontal microfin copper tube. The test facility had a straight, horizontal test section with an active length of 2.0 m and was cooled by cold water circulated in a surrounding annular space. The annular-side heat transfer coefficients were obtained using the Wilson plot method. The average heat transfer coefficient and pressure drop data are presented at the condensation temperature of 35 °C in the range of 100–440 kg·m−2·s−1 mass flux. The test data of R-513A are compared with those of R-134a, R-1234yf, and R-1234ze(E). The average condensation heat transfer coefficients of the R-513A and R-1234ze(E) refrigerants were similar to R-134a at the lower mass flux (100~150 kg·m−2·s−1), while they were up to 10% higher than R-134a as the mass flux increased. The pressure drop of R-513A was similar to R-1234yf and 10% lower than that of R-134a at the higher mass flux. The R-1234ze(E) pressure drops were 20 % higher compared to those of R-134a at the higher mass flux.

Experimental Investigation of Condensation Heat Transfer in Annular Helicoidal Pipes at Different Orientations

Volume 3 ◽  
2004 ◽  
Author(s):  
H. L. Mo ◽  
R. Prattipati ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Cooling Water ◽  
Saturation Temperature ◽  
Experimental Investigations ◽  
Percentage Increase ◽  
Transfer Coefficients ◽  
Cooling Water Temperature ◽  
Heat Transfer Coefficients ◽  
Mass Flow Rates

Experimental investigations were conducted on condensation of R134a in annular helicoidal pipes with three orientations, 0°, 45° and 90°. The experimental results indicated that the refrigerant heat transfer coefficients increased with the increase of cooling water temperature, mass flow rates of refrigerant and cooling water, and decreased with the increase of saturation temperature of R134a. When the orientation increased from 0° to 90°, the refrigerant Nusselt number increased around 11% at refrigerant Reynolds number of 80, and around 16% at 200, the percentage increase of refrigerant Nusselt number from 0° to 45° accounted for more than two times of that from 45° to 90°. The performance of annular helicoidal pipe was evaluated by comparing with equivalent smooth straight pipe and identical helicoidal pipe.

scholarly journals Experimental validation of pressure drop models during flow boiling of R134a – effect of flow acceleration and entrainment

2018 ◽  
Vol 240 ◽  
pp. 03010
Author(s):  
Tomasz Muszynski ◽  
Rafal Andrzejczyk ◽  
Carlos Dorao
Keyword(s):  
Heat Transfer ◽  
Pressure Drop ◽  
Flow Boiling ◽  
Saturation Temperature ◽  
High Heat ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Flow Acceleration ◽  
High Heat Transfer

A crucial step to assure proficient work of power and process apparatus is their proper design. A wide array of those devices operates within boiling or condensation of the working fluid to benefit from high heat transfer rates. Two-phase flows are associated with high heat transfer coefficients because of the latent heat of evaporation and high turbulence level between the liquid and the solid surface. Predicting heat transfer coefficient and pressure drop is a challenging task, and has been pursued by researchers for decades. In the case of diabatic flows, the total pressure drop is due to the change in kinetic and potential energy. The article presents detailed boiling pressure drops data for R134a at a saturation temperature of 19.4°C. Study cases have been set for a mass flux varying from 300 to 500 kg/m2s. Presented data along with the data reduction procedure was used to obtain the momentum pressure drop values during flow boiling. The study focuses on experimental values of momentum pressure drop component and its prediction based on various void fraction models and entrainment effects.

Heat Transfer During Condensation of a Low-GWP Refrigerant on an Enhanced Cylindrical Surface

2017 ◽  
Author(s):  
Tailian Chen
Keyword(s):  
Heat Transfer ◽  
Smooth Surface ◽  
Cooling Water ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Condensation Process ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cylindrical Tubes ◽  
Enhanced Tube

In this work, heat transfer coefficients during condensation of an environment-friendly refrigerant R-1233zd(e) on the outside surface of two cylindrical tubes are individually measured. The cooling water flows inside the tubes and provides cooling to the vapor refrigerant. One tube is a plain smooth tube (smooth both inside and outside) while the other tube is an enhanced tube, with the inside surface having 2D helical ridges and the outside surface having 3D extruded fins. The tests were conducted at the saturation temperature 36.1 °C, a typical temperature in chiller condensers. The results show the overall heat transfer coefficients of the enhanced tube are approximately 8.4 times higher as a result of the heat transfer enhancement on both sides. The condensation heat transfer degrades with an increase in the degree of subcooling, and the trend of degradation is the nearly the same for both the smooth and the enhanced tube, both is smaller than that in the Nusselt correlation. Compared with condensation on the smooth surface, the condensation heat transfer from the enhanced surface is enhanced approximately 10.8 times higher than that on the smooth surface. In addition to enlarged heat transfer area of the extruded fins, the enhancement in the condensation heat transfer is partly attributed to a better condensate draining mechanism of the 3D-structured fins where surface tension plays an important role. Further analysis reveals that heat transfer during the condensation process on the 3D low-fin surface follows the Nusselt correlation with a multiplier that accounts for the enhancement in heat transfer, which is desirably simple approach to modeling condensation heat transfer on the complex 3D enhanced surfaces. This work can lead to more insights into the physical mechanisms during the complex condensation process.

Experimental Study of Evaporation Heat Transfer Characteristics and Pressure Drops of R410A and R134a in a Multiport Mini-Channel

2009 ◽  
Author(s):  
Jatuporn Kaew-On ◽  
Somchai Wongwises
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Evaporation Heat ◽  
Evaporation Heat Transfer ◽  
R 134A

The evaporation heat transfer coefficients and pressure drops of R-410A and R-134a flowing through a horizontal-aluminium rectangular multiport mini-channel having a hydraulic diameter of 3.48 mm are experimentally investigated. The test runs are done at refrigerant mass fluxes ranging between 200 and 400 kg/m2s. The heat fluxes are between 5 and 14.25 kW/m2, and refrigerant saturation temperatures are between 10 and 30 °C. The effects of the refrigerant vapour quality, mass flux, saturation temperature and imposed heat flux on the measured heat transfer coefficient and pressure drop are investigated. The experimental data show that in the same conditions, the heat transfer coefficients of R-410A are about 20–50% higher than those of R-134a, whereas the pressure drops of R-410A are around 50–100% lower than those of R-134a. The new correlations for the evaporation heat transfer coefficient and pressure drop of R-410A and R-134a in a multiport mini-channel are proposed for practical applications.

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