scholarly journals Experimental Study of HFE 7000 Refrigerant Condensation in Horizontal Pipe Minichannels

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 6886
Author(s):  
Małgorzata Sikora ◽  
Tadeusz Bohdal ◽  
Karolina Formela
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flux Density ◽  
Mass Flux ◽  
Internal Diameter ◽  
Two Phase ◽  
Horizontal Pipe

This article presents the results obtained from our own experimental investigations on heat exchange and pressure drop during the condensation flow of the HFE 7000 refrigerant in pipe minichannels with an internal diameter of di = 1.2–2.5 mm. The influence of vapor quality x and the mass flux density G on the two-phase flow pressure drops and heat transfer is presented. The tests were performed for the mass flux density range of G = 110–4700 kg/m2s, saturation inlet temperature of Ts = 36–43 °C and heat flux density of q = 1 ÷ 20 kW/m2. The pressure drop characteristics and heat transfer coefficient as a function of the internal diameter of minichannels are illustrated. The results of experimental research on the heat transfer coefficient and two-phase pressure drop are compared with correlations developed by other authors. The best accuracy has a comparison of experimental study with correlation of Rahman-Kariya-Miyara et al. and Mikielewicz et al.

Effect of the Pressure Drop Oscillation on the Local Heat Transfer Coefficient in a Heated Horizontal Pipe

2018 ◽  
Author(s):  
Il Woong Park ◽  
Maria Fernandino ◽  
Carlos Alberto Dorao
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Local Heat Transfer ◽  
Negative Slope ◽  
Working Fluid ◽  
Two Phase ◽  
Horizontal Pipe ◽  
The Heat Transfer Coefficient

Two-phase flow instabilities have been studied during the past decades. Pressure drop oscillation (PDO) shows a relatively larger amplitude oscillation compared with other instabilities. This oscillation typically occurs when the system has compressible volume and operates in a negative slope region of the pressure drop versus flow rate curve. The characteristics of the PDO has been studied experimentally and theoretically. Even though research has been performed for identifying the characteristics of the PDO, how the PDO affects the heat transfer coefficient (HTC) remain unclear. In this study, the heat transfer coefficient is experimentally studied during pressure drop oscillation. The experiment is conducted with a heated horizontal tube with 5 mm inner diameter and 2.0 meters in length, and the R-134a is used a working fluid. For the cases studied, no significant effect of the PDO on the average heat transfer coefficient was observed.

Two Phase Pressure Drop and Boiling Heat Transfer in Micro Pin Fin Channel

2016 ◽  
Author(s):  
Ki Moon Jung ◽  
Hee Joon Lee
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Pin Fin ◽  
Boiling Heat Transfer Coefficient

In this paper, boiling experiments were conducted to study two-phase pressure drop and the heat transfer coefficient in a staggered array micro pin fin channel of degassed water at a mass flux range of 9.3 to 46.6 kg/m2s and a heat flux of 0.5 to 0.9 W/cm2. Copper was used for the pin fin array microchannel heat sink, which was 31 mm in width and 82 mm in length. Micro pin fins, of 400 μm in diameter and 700 μm in height, were manufactured using a micro milling machine on the channel block. The distance between two pin fin surfaces is 300 μm. A thin film heater, which supplies a maximum constant heat flux of 1.55 W/cm2, was attached underneath the heat sink. From the experimental results, at a vapor quality of up to 0.04, the boiling heat transfer coefficient decreased as the quality increased. Results show that the heat transfer coefficient is dependent on the mass flux. The data also showed that the pressure drop increased with increasing mass flux. The data obtained in this study were compared to the existing correlations of boiling pressure drop and heat transfer coefficients. Results showed that the correlation with boiling pressure drop of Qu and Siu-Ho[22] yielded a prediction of 21.3% average error Additionally, as a result of comparison with the four existing correlations of boiling heat transfer coefficient, all correlations had a lower prediction for the heat transfer coefficients obtained in this study. Through visualization, it was found that the bubbles generated between the fins began to grow and moved downstream. We observed a stationary vapor pocket in which bubbles did not flow.

Experimental Investigation of Heat Transfer Enhancement of Shell and Tube Heat Exchanger Using SnO2-Water and Ag-Water Nanofluids

2019 ◽  
Vol 12 (4) ◽  
Author(s):  
S. V. Sridhar ◽  
R. Karuppasamy ◽  
G. D. Sivakumar
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Convective Heat Transfer Coefficient ◽  
Two Phase ◽  
Tube Heat Exchanger ◽  
Shell And Tube

Abstract In this investigation, the performance of the shell and tube heat exchanger operated with tin nanoparticles-water (SnO2-W) and silver nanoparticles-water (Ag-W) nanofluids was experimentally analyzed. SnO2-W and Ag-W nanofluids were prepared without any surface medication of nanoparticles. The effects of volume concentrations of nanoparticles on thermal conductivity, viscosity, heat transfer coefficient, fiction factor, Nusselt number, and pressure drop were analyzed. The results showed that thermal conductivity of nanofluids increased by 29% and 39% while adding 0.1 wt% of SnO2 and Ag nanoparticles, respectively, due to the unique intrinsic property of the nanoparticles. Further, the convective heat transfer coefficient was enhanced because of improvement of thermal conductivity of the two phase mixture and friction factor increased due to the increases of viscosity and density of nanofluids. Moreover, Ag nanofluid showed superior pressure drop compared to SnO2 nanofluid owing to the improvement of thermophysical properties of nanofluid.

Two Phase Heat Transfer of Ammonia in a Mini/Micro Channel

2010 ◽  
Author(s):  
M. Hamayun Maqbool ◽  
Bjo¨rn Palm ◽  
R. Khodabandeh ◽  
Rashid Ali
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Experimental Results ◽  
Working Fluid ◽  
Internal Diameter ◽  
Vapour Quality ◽  
The Heat Transfer Coefficient

Experiments have been performed to investigate heat transfer in a circular vertical mini channel made of stainless steel (AISI 316) with internal diameter of 1.70 mm and a uniformly heated length of 245 mm using ammonia as working fluid. The experiments are conducted for a heat flux range of 15 to 350 kW/m2 and mass flux range of 100 to 500 kg/m2s. The effects of heat flux, mass flux and vapour quality on the heat transfer coefficient are explored in detail. The experimental results show that the heat transfer coefficient increases with imposed wall heat flux while mass flux and vapour quality have no considerable effect. Experimental results are compared to predictive methods available in the literature for boiling heat transfer. The correlations of Cooper et al. [1] and Shah [3] are in good agreement with our experimental data.

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.

Microchannel Size Effects on Two-Phase Local Heat Transfer and Pressure Drop in Silicon Microchannel Heat Sinks With a Dielectric Fluid

2007 ◽  
Author(s):  
Tannaz Harirchian ◽  
Suresh V. Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Flow Boiling ◽  
Heat Sinks ◽  
Dielectric Fluid ◽  
Two Phase ◽  
Microchannel Heat Sinks ◽  
The Heat Transfer Coefficient

Two-phase heat transfer in microchannels can support very high heat fluxes for use in high-performance electronics-cooling applications. However, the effects of microchannel cross-sectional dimensions on the heat transfer coefficient and pressure drop have not been investigated extensively. In the present work, experiments are conducted to investigate the local flow boiling heat transfer in microchannel heat sinks. The effect of channel size on the heat transfer coefficient and pressure drop is studied for mass fluxes ranging from 250 to 1600 kg/m2s. The test sections consist of parallel microchannels with nominal widths of 100, 250, 400, 700, and 1000 μm, all with a depth of 400 μm, cut into 12.7 mm × 12.7 mm silicon substrates. Twenty-five microheaters embedded in the substrate allow local control of the imposed heat flux, while twenty-five temperature microsensors integrated into the back of the substrates enable local measurements of temperature. The dielectric fluid Fluorinert FC-77 is used as the working fluid. The results of this study serve to quantify the effectiveness of microchannel heat transport while simultaneously assessing the pressure drop trade-offs.

Experimental Study on Condensation in the Outer Annular Region Outside Horizontal Enhanced Tubes

2020 ◽  
Author(s):  
Zeguan Dong ◽  
Jianghui Zhang ◽  
Zhen Li ◽  
Yan He ◽  
David J. Kukulka ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Surface Structures ◽  
Annular Region ◽  
Diagram Method ◽  
Enhanced Tubes ◽  
Heat Transfer Capacity

Abstract Single-phase and flow condensation experiments were performed using refrigerant R410A in the outer annular region of horizontal enhanced tube with different enhanced surfaces at a saturation temperature of 45°C in the range of mass flux 44.43–102.23kg/(m2s). The vapor quality ranges from 0.8 to 0.2. The outer diameters of the tubes are all 19.05mm, but the inner diameters are slightly different due to different surface structures. The surface structures of the three enhanced tubes are fins(EHT1 tube), toothed structures (EHT2 tube) and fine cavities(EHT3 tube) of different sizes and densities. Among them, the EHT3 tube has internal threads. Wilson diagram method was used to determine the enhancement ratio of the water side heat transfer coefficient of EHT3 tube. It was found that the pressure drop increased with the increase of mass flux, while the heat transfer coefficient showed different trends, and the smooth tube was always the lowest of the four tubes. A comprehensive evaluation factor α combining heat transfer enhancement factor (EF) and pressure drop penalty factor (PF) was defined, in which EHT2 tube (1.38–1.75) was the largest, with strong heat transfer capacity and small pressure drop, so the condensing heat transfer capacity of EHT2 tube was the best.

Experiment study on condensation heat transfer and pressure drop of steam flow inside rectangular tube with different aspect ratio

2020 ◽  
pp. 095765092097222
Author(s):  
Yan Yan ◽  
Jixian Dong ◽  
Tong Ren ◽  
Shiyu Feng
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Aspect Ratio ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Condensation Heat Transfer ◽  
Aspect Ratios ◽  
Rectangular Tubes ◽  
Condensation Heat Transfer Coefficient

In this study, the condensation heat transfer coefficient and pressure drop of steam are obtained in small rectangular tubes with different aspect ratios. The experiments were carried out on three rectangular tubes with aspect ratios of 1:2, 1:3 and 1:5, with mass flux between 25 and 45 kg/m2s, and vapor qualities between 0.1 and 0.8. The experimental data were analyzed to determine the effect of vapor quality, mass flux, and aspect ratio on the heat transfer coefficient and pressure drop. The results showed that the effect of aspect ratio on condensation heat transfer coefficient appears to be dependent on the flow pattern. For stratified flow, the condensation heat transfer coefficient increases as the mass flux increases. For annular flow, the condensation heat transfer coefficient hardly changed. The pressure drop always increases as the aspect ratio increases. Previous studies on round tube heat transfer and pressure drop correlations have not successfully predicted the small rectangular tube data; therefore, modified Shah correlation and Lockhart & Martinelli correlation are proposed, which predict the data with 20% and 23% RMS error, respectively.

Impact of Channel Geometry on Two-Phase Flow Heat Transfer Characteristics of Refrigerants in Microchannel Heat Exchangers

1998 ◽  
Vol 120 (2) ◽  
pp. 485-491 ◽  
Author(s):  
T. S. Ravigururajan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Two Phase Flow ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Heat ◽  
The Heat Transfer Coefficient

Microchannel surfaces, often machined to 20 to 1000 μm in width and depth, are employed in high-heat-flux applications. However, a large number of variables, control the two-phase flow heat transfer coefficient. The pressure, the surface heat flux, and the mass flux significantly affect the thermal transport. Experiments were conducted on a setup that was built for testing microchannel heat exchanges. The parameters considered in the study are power input: 20 to 300 W, volume flow rate: 35 to 300 ml/min, quality: 0 to 0.5, inlet subcooling: 5 to 15°C. The results indicate that the heat transfer coefficient and pressure drop are functions of the flow quality, the mass flux, and, of course, the heat flux and the related surface superheat. The heat transfer coefficient decreases from a value of 12,000 W/m2-K to 9000, W/m2-K at 80°C, when the wall superheat is increased from 10 to 80°C. The coefficient decreases by 30 percent when the exit vapor quality is increased from 0.01 to 0.65.

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