Experimental Investigation on Flow Characteristics of Supercritical CO2 in a Helically Coiled Tube

2013 ◽  
Vol 368-370 ◽  
pp. 631-635
Author(s):  
Shu Xiang Wang ◽  
Wei Zhang ◽  
Jin Liang Xu
Keyword(s):  
Heat Flux ◽  
Fluid Flow ◽  
Mass Flux ◽  
Flow Characteristics ◽  
Experimental Investigations ◽  
Coiled Tube ◽  
Frictional Pressure Drop ◽  
Helically Coiled Tube ◽  
Coil Diameter ◽  
Fluid Flow Characteristics

Under the background of global warming, carbon dioxide among natural refrigerants has attracted considerable attention as an alternative refrigerant. In the present study, experimental investigations of the fluid flow characteristic of supercritical CO2in a helically coiled tube with the inner diameter 9.0 mm, coil diameter 283 mm and coil pitch 32 mm were carried out. Both frictional pressure drop and friction factor were obtained under the pressure of 8.0 MPa, mass flux from 0 to 600 kg/m2s and inner heat flux from 0 to 20 kW/m2. The results indicate that inner wall heat flux and mass flux had significant effects on fluid flow characteristics. The study provides experimental data that could be used for the design and development of more efficient exchangers for refrigeration conditioning, heat pump and some other systems.

Convective Boiling Heat Transfer and Pressure Drop Characteristics of R134a in a Microfinned Helically Coiled Tube

2005 ◽  
Author(s):  
Wenzhi Cui ◽  
Longjian Li ◽  
Mingdao Xin ◽  
Qinghua Chen ◽  
Quan Liao ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Pressure Drop ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Annular Flow ◽  
Convective Boiling ◽  
Coiled Tube ◽  
Frictional Pressure Drop ◽  
Helically Coiled Tube

The main purpose of this paper was to experimentally study the heat transfer and pressure drop characteristics of refrigerant R134a boiling inside a new geometry microfin helically coiled tube. Experiments were performed in a range of mass quality from 0.05 up to 0.9, mass velocity 70 ∼ 380 kg/m2s and heat flux 2.0 ∼ 21.8 kW/m2. The local and average convective boiling heat transfer coefficients were reported in this paper, which were found to be dependent on both of mass flux and heat flux. Compared with corresponding smooth helically coiled tube, the microfin helically coiled tube could enhance the convective boiling heat transfer very well. The enhancement factor was up to 2.2 with the variety of mass flux and heat flux. Heat transfer in annular flow was specially studied. A flow boiling heat transfer correlation was presented for the annular flow regime, which had a mean deviation of 9.1%. The frictional pressure drop values were obtained by subtracting acceleration pressure drop and gravitational pressure drop from the measured total pressure drop. The frictional pressure drop data can be well correlated by Lockhart-Martinelli parameter. Considering the corresponding flow regimes, i.e., stratified and annular flow, two frictional pressure drop correlations were proposed, and showed a good agreement with the respective experimental data.

Fluid Flow Characteristics of a Confined Slot Jet Without or With a Target Surface

2005 ◽  
Author(s):  
L. K. Liu ◽  
C. J. Fang ◽  
M. C. Wu ◽  
C. Y. Lee ◽  
Y. H. Hung
Keyword(s):  
Reynolds Number ◽  
Fluid Flow ◽  
Fluid Velocity ◽  
Flow Characteristics ◽  
Target Surface ◽  
Streamwise Velocity ◽  
Separation Distance ◽  
Experimental Investigations ◽  
Flow Parameters ◽  
Fluid Flow Characteristics

A series of experimental investigations with a stringent measurement method on the fluid flow characteristics of slot jet without or with a target surface have been successfully conducted. From all the fluid velocity data measured in the present study, the experimental conditions have been verified to be spanwise-symmetrically maintained and the results have been achieved in a spanwise-symmetric form. Three types of jet configuration without or with target surface are investigated: (A) Confined Slot Jet without Target Surfaces – the fluid flow parameters studied in the present investigation is the jet Reynolds number (ReD). Its ranges are ReD=506-1517. (B) Confined Slot Jet with Smooth Surfaces – the fluid flow parameters studied in the present investigation include the ratio of jet separation distance (H) to nozzle width (W) and the jet Reynolds number (ReD). The ranges of the relevant parameters are H/W=2–10 and ReD=504–1526. (C) Confined Slot Jet with Extended Surfaces – the fluid flow parameters studied include the ratio of jet separation distance (H) to nozzle width (W), the Reynolds number (ReD) and the ratio of extended surface height (Hes) to nozzle width (W). Their ranges are H/W=3–10, Hes/W=0.74-3.40 and ReD=501–1547. The flow characteristics such as the local mean streamwise velocity distribution, mean streamwise velocity decay along jet centerline, local jet turbulence intensity distribution, and turbulence intensities along jet centerline have been presented and discussed in the study.

Numerical Investigation of Subcooled Boiling Heat Transfer in Helically-Coiled Tube

2020 ◽  
Vol 17 (1) ◽  
pp. 7675-7686
Author(s):  
Luthfi A. F. Haryoko ◽  
Jundika C. Kurnia ◽  
Agus P. Sasmito
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Operating Pressure ◽  
Subcooled Boiling ◽  
Coiled Tube ◽  
Helically Coiled Tube

Subcooled boiling heat transfer in helically-coiled tubes offers better heat transfer performance than any other types of boiling processes due to its ability to capture high heat flux with a relatively low wall superheat. This study investigates turbulent subcooled forced convection boiling performances of water-vapour in a helically-coiled tube with various operating conditions i.e. operating pressure, heat, and mass flux. Developed CFD model is validated against previously published experimental results using the RPI model. The model is developed based on the Eulerian-Eulerian framework coupled with k-ε RNG turbulence model and Standard Wall-Function. A good agreement is found between numerical prediction and experimental counterpart for the bulk fluid temperature and non-dimensional length. The result indicates that the subcooled boiling heat transfer in a helically-coiled tube tends to improve heat transfer coefficient and pressure drop in the domain. Subcooled boiling starts at the inner side of the helically-coiled tube (f=9900) due to the existence of secondary flow that comes from the coil curvature. Heat transfer coefficient and pressure drop increased with increasing heat flux and decreasing mass flux, and operating pressure. This is caused by the bubble movement and convective heat transfer phenomena in a helically-coiled tube. Finally, this study can provide a guideline for future research of the subcooled boiling in a helically-coiled tube.

scholarly journals Influence of fluid flow characteristics and heat transfer in a tube heat exchanger using H-shape inserts with circular ring

2021 ◽  
Author(s):  
Satyendra Singh ◽  
◽  
Tarun Joshi ◽  
Himanshi Kharkwal ◽  
◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Heat Exchanger ◽  
Thermal Performance ◽  
Flow Characteristics ◽  
Circular Ring ◽  
Main Section ◽  
Tube Heat Exchanger ◽  
Fluid Flow Characteristics

The heat transfer and fluid flow characteristics in a tube heat exchanger using H-shape inserts with circular ring (CRWHS) has been done by computationally and experimentally. In this investigation parameters like ratio of the diameters and pitches are considered. The value of diameter and pitch ratios are (DR=0.8, 0.9), (PR=3, 4) respectively. The main section in which investigation was done is 1.5m long and the hydraulic diameter of the tube is 68.1mm. 1000 W/m2 heat flux was provided in the main section. Heat flux was constant throughout the investigation. Air is used as a working medium in which 6000 to 21000 Reynolds number was used for the investigation. The observation revealed that the increment in heat transfer rate is 4.56 times as compare to smooth tube for the circular ring with H-shape inserts. In case of DR=0.8 and PR=3, maximum thermal performance factor was obtain which is 3.24. In GIT the deviation in Nusselt number & friction factor is limited to ±0.4% & ±0.1% respectively. CFD analysis result comparisons with experimental one are presented in which the maximum deviations for thermal performance factor are limited to ±3.6%.

Numerical study on significance of wave amplitude, wavelength and aspect ratio on heat transfer and fluid flow characteristics in circular wavy MC heat sink design

2021 ◽  
pp. 095440622198937
Author(s):  
Valaparla Ranjith Kumar ◽  
Karthik Balasubramanian ◽  
K Kiran Kumar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Fluid Flow ◽  
Aspect Ratio ◽  
Wave Amplitude ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Uniform Heat Flux ◽  
Uniform Heat ◽  
Fluid Flow Characteristics

In this study, hydrothermal characteristics in a circular wavy microchannel (CWMC) design under laminar flow conditions with uniform heat flux is numerically studied. Parametric studies in an innovative CWMC design were carried out at various wave amplitudes, wavelengths and aspect ratios. Three dimensional numerical study was performed in the Reynolds number (Re) range from 100 to 300 with uniform heat flux (50 W/cm2) applied at bottom of the channel, treating copper as channel material and water as working fluid. The obtained results were compared to sinusoidal wavy microchannel (SWMC).The results showed that heat transfer and fluid flow characteristics were significantly influenced by wave amplitude, wavelength and aspect ratio. Velocity vectors and contours were presented to understand the heat transfer and fluid flow characteristics. Stream-wise local Nusselt number, overall performance factor, span-wise velocity and temperature variation are also presented. It is concluded that CWMC with higher wave amplitude, smaller wave length and smaller aspect ratio gives higher heat transfer augmentation with corresponding pressure drop penalty.

Studies on Fluid-to-Fluid Modeling of Critical Heat Flux in a Helically-Coiled Tube

2012 ◽  
Vol 588-589 ◽  
pp. 1777-1780 ◽  
Author(s):  
Lu Zhi Tan ◽  
Ji Tian Han ◽  
Chang Nian Chen ◽  
Peng Cheng Dou
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
High Mass ◽  
Coiled Tube ◽  
Fluid Modeling ◽  
Modeling Approaches ◽  
Flow Parameters ◽  
Helically Coiled Tube ◽  
R 134A

An experimental study on critical heat flux (CHF) in a helically-coiled tube cooled with R-134a has been completed in order to assess present fluid-to-fluid modeling approaches. The investigated range of flow parameters for R-134a was: pressure from 0.2 to 0.5 MPa, mass flux values from 50 to 1500 kg m-2 s-1 and inlet quality from -0.2 to 0.1. The CHF data of R-134a have been compared with that of water by applying the Ahmad and the Katto modeling. The water equivalent CHF data translated from R-134a CHF data by using the two modeling approaches have shown a good agreement with the actual water CHF data from previous studies when mass flux exceeds 600 kg m-2 s-1. The results indicate that both the Ahmad and the Katto modeling can be applied only for the high mass flux conditions in helically-coiled tubes.

Fluid Flow Characteristics for Partially-Confined Compact Plain-Plate-Fin Heat Sinks

2005 ◽  
Author(s):  
M. P. Wang ◽  
T. Y. Wu ◽  
J. T. Horng ◽  
C. Y. Lee ◽  
Y. H. Hung
Keyword(s):  
Experimental Data ◽  
Fluid Flow ◽  
Pressure Drop ◽  
Heat Sink ◽  
Flow Behavior ◽  
Flow Characteristics ◽  
Heat Sinks ◽  
Experimental Investigations ◽  
Channel Height ◽  
Fluid Flow Characteristics

A series of experimental investigations with a stringent measurement method on the study of the fluid flow behavior for confined compact heat sinks in forced convection have been successfully conducted. In the present study, a theoretical model to effectively predict the velocity and pressure drop for partially-confined heat sinks has been successfully developed. The air velocities flowing into heat sink Us through side bypass U1 and top bypass U2 for various 0.47<H/Hc<1 ratios are evaluated, where H/Hc is the ratio of the heat sink height to channel height. The maximum and average deviations of the velocities predicted by the present model from the experimental data are less than 20.31% and 13.13%, respectively, for confined compact heat sinks. Besides, the results show a good agreement between the predicted results and the experimental data of the pressure drop for the cases of H/Hc = 1. Nevertheless, the relative deviation of the predictions from the experimental data becomes more significant with decreasing H/Hc ratio, i.e., increasing the top bypass of confined compact heat sink. A new modified correlation of pressure drop including the H/Hc effect is presented. The maximum and average deviations of the results predicted by the new correlation from the experimental data are 14.48% and 7.72%, respectively.

Experimental study on critical heat flux during flow boiling of R134a in a vertical helically coiled tube

2020 ◽  
Vol 234 (15) ◽  
pp. 3094-3101
Author(s):  
Xiaojuan Niu ◽  
Huaijie Yuan ◽  
Liang Zhao
Keyword(s):  
Experimental Study ◽  
Heat Flux ◽  
Critical Heat Flux ◽  
Wall Temperature ◽  
Mass Flux ◽  
Flow Boiling ◽  
Vapor Quality ◽  
Coiled Tube ◽  
Helically Coiled Tube ◽  
System Pressure

This paper carried out an experimental study on the critical heat flux during flow boiling of R134a in a vertical helically coiled tube. The length, inner diameter, coil diameter, and pitch of the test tube were 1.85 m, 8 mm, 205 mm, and 25 mm, respectively. Experiments cover the mass flux range of 190–400 kg·m−2·s−1, heat flux of 15–55 kW·m−2, inlet pressure of 0.8–1.1 MPa, and inlet vapor quality of 0.01–0.35. The effects of critical heat flux identification method, mass flux, system pressure, and inlet vapor quality on critical heat flux were presented. The critical heat flux obtained by the wall temperature rise method was larger than that obtained by the wall temperature oscillation method. The deviation of the critical heat flux corresponding to two methods, including wall temperature rises sharply above 10 ℃ and wall temperature drastic oscillation, was about 20% under the present experimental conditions. The critical heat flux increased with mass flux while it decreased with the inlet vapor quality and pressure. The experiment data were compared with four existing empirical correlations. A new correlation is proposed for critical heat flux prediction in vertical helical tubes.

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