Heat Transfer Measurements and Correlations for Air-Water Two-Phase Slug Flow in a Horizontal Pipe

Volume 3 ◽  
2004 ◽  
Author(s):  
Afshin J. Ghajar ◽  
Kapil Malhotra ◽  
Jae-Yong Kim ◽  
Steve A. Trimble
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Slug Flow ◽  
Reynolds Numbers ◽  
Mean Deviation ◽  
Heat Transfer Correlation ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Transfer Data ◽  
Heat Transfer Coefficients

Local heat transfer coefficients and flow parameters were measured for air-water slug flow in a horizontal 25.4 mm stainless steel schedule 10S pipe with a length to diameter ratio of 100. For this systematic study, a total of 83 data points were taken by carefully coordinating the liquid and gas superficial Reynolds number combinations. The heat transfer data were measured under a uniform wall heat flux boundary condition ranging from about 3800 to 16000 W/m2. The superficial Reynolds numbers ranged from about 3160 to 30290 for water and from about 1480 to 5840 for air. Comparison of heat transfer data for slug flow revealed that the heat transfer results were significantly dependent on the liquid and gas superficial Reynolds numbers. Overall, the experimental heat transfer data showed that the liquid phase dominated the heat transfer. However, it was found that the heat transfer data having a fixed liquid superficial Reynolds number showed that the heat transfer coefficients decreased as the gas superficial Reynolds number increased. A general heat transfer correlation for two-phase gas-liquid flow was fitted to our experimental horizontal slug flow heat transfer data with a mean deviation of −2.77% and an RMS deviation of 9.92%. Furthermore, a simplified heat transfer correlation for slug flow was developed based on the trends of heat transfer coefficient over the superficial liquid and gas Reynolds numbers. The proposed correlation predicted the experimental data with a mean deviation of −1.44% and an RMS deviation of 5.15%.

Experimental Investigation of Local Heat Transfer Distribution on Smooth and Roughened Surfaces Under an Array of Angled Impinging Jets

2001 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Deborah A. Kaminski
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Flow ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Impinging Jets ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Roughened Surface

Abstract Measurements of the local heat transfer distribution on smooth and roughened surfaces under an array of angled impinging jets are presented. The test rig is designed to simulate impingement with cross-flow in one direction which is a common method for cooling gas turbine components such as the combustion liner. Jet angle is varied between 30, 60, and 90 degrees as measured from the impingement surface, which is either smooth or randomly roughened. Liquid crystal video thermography is used to capture surface temperature data at five different jet Reynolds numbers ranging between 15,000 and 35,000. The effect of jet angle, Reynolds number, gap, and surface roughness on heat transfer efficiency and pressure loss is determined along with the various interactions among these parameters. Peak heat transfer coefficients for the range of Reynolds number from 15,000 to 35,000 are highest for orthogonal jets impinging on roughened surface; peak Nu values for this configuration ranged from 88 to 165 depending on Reynolds number. The ratio of peak to average Nu is lowest for 30-degree jets impinging on roughened surfaces. It is often desirable to minimize this ratio in order to decrease thermal gradients, which could lead to thermal fatigue. High thermal stress can significantly reduce the useful life of engineering components and machinery. Peak heat transfer coefficients decay in the cross-flow direction by close to 24% over a dimensionless length of 20. The decrease of spanwise average Nu in the crossflow direction is lowest for the case of 30-degree jets impinging on a roughened surface where the decrease was less than 3%. The decrease is greatest for 30-degree jet impingement on a smooth surface where the stagnation point Nu decreased by more than 23% for some Reynolds numbers.

A Mechanistic Heat Transfer Correlation for Non-Boiling Two-Phase Flow in Horizontal, Inclined and Vertical Pipes

2011 ◽  
Author(s):  
Clement C. Tang ◽  
Afshin J. Ghajar
Keyword(s):  
Heat Transfer ◽  
Friction Factor ◽  
Two Phase Flow ◽  
Mechanistic Model ◽  
Local Heat Transfer ◽  
Phase Flow ◽  
Heat Transfer Correlation ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Transfer Data

A mechanistic heat transfer correlation is proposed to estimate heat transfer coefficient for non-boiling two-phase flow in horizontal, slightly inclined, and vertical pipes using the analogy between friction factor and heat transfer. Local heat transfer coefficients, pressure drops and flow parameters were measured for air-water flow in a 27.9 mm stainless steel pipe. The heat transfer and pressure drop data were collected by carefully coordinating the gas and liquid superficial Reynolds numbers. The proposed mechanistic correlation is validated by using experimentally measured heat transfer data. Evaluation of the mechanistic correlation with the measured heat transfer data indicated that the analogy between friction factor and heat transfer can be used with reasonable accuracy for heat transfer predictions in non-boiling two-phase pipe flow. Comparison with experimental results showed that the bulk of the data points were predicted within ±30% by the mechanistic model.

Heat Transfer and Pressure Drop Correlations for Square Channels With V-Shaped Ribs at High Reynolds Numbers

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Nawaf Y. Alkhamis ◽  
Akhilesh P. Rallabandi ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Friction Factor ◽  
Thermal Performance ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
High Reynolds Numbers ◽  
High Reynolds ◽  
Rib Roughened

Heat transfer coefficients and friction factors are measured in a 45 deg V-shaped rib roughened square duct at high Reynolds numbers, pertaining to internal passages of land-based gas turbine engines. Reynolds numbers in this study range from 30,000 to 400,000, which is much higher than prior studies of V-shaped rib roughened channels. The dimensions of the channel are selected to ensure that the flow is in the incompressible regime. Blockage ratio e/D ranges from 0.1 to 0.18 and the spacing ratio P/e ranges from 5 to 10. Reported heat transfer coefficients are regionally averaged, measured by isothermal copper plates. Results show that the heat transfer enhancement decreases with increasing Reynolds number. The friction factor is found to be independent of the Reynolds number. The thermal performance decreases when the Reynolds number increases. 45 deg V-shaped ribs show a higher thermal performance than corresponding 45 deg angled ribs, consistent with the trend established in literature. Correlations for the Nusselt number and the friction factor as function of Re, e/D, and P/e are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+).

Prediction of Two-Phase Heat Transfer Coefficients in a Horizontal Pipe for Different Inclined Positions With Artificial Neural Networks

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Najmeh Sobhanifar ◽  
Ebrahim Ahmadloo ◽  
Sadreddin Azizi
Keyword(s):  
Neural Network ◽  
Heat Transfer ◽  
Experimental Data ◽  
Neural Networks ◽  
Two Phase Flow ◽  
Reynolds Numbers ◽  
Phase Flow ◽  
Transfer Coefficients ◽  
Two Phase ◽  
Heat Transfer Coefficients

This paper presents the application of artificial neural network (ANN) in prediction of heat transfer coefficients (HTCs) of two-phase flow of air–water in a pipe in the horizontal and slightly upward inclined (2, 5, and 7 deg) positions. For this purpose, the superficial liquid and gas Reynolds numbers and the inclination of the pipe were used as input parameters, while the HTCs of two-phase flow were used as output parameters in training and testing of the multilayered, feedforward, backpropagation neural networks. In this present study, experimental data were taken from literature and then used for the ANN model. The superficial liquid and gas Reynolds numbers ranged from 740 to 26,100 and 560 to 47,600 for water and air, respectively. The mean deviations against experimental data were determined for the model. Results showed that the network predictions were in very good agreement with the experimental HTC data, whereas the correlation showed more deviations. Finally, results showed that the accuracy between the neural network predictions and experimental data was achieved with mean relative error (MRE) of 2.92% and correlation coefficient (R) that was 0.997 for all datasets, which suggests the reliability of the ANNs as a strong tool for predicting HTCs with two-phase flows.

Boiling Heat Transfer in a Horizontal Small-Diameter Tube

1993 ◽  
Vol 115 (4) ◽  
pp. 963-972 ◽  
Author(s):  
M. W. Wambsganss ◽  
D. M. France ◽  
J. A. Jendrzejczyk ◽  
T. N. Tran
Keyword(s):  
Heat Transfer ◽  
Flow Pattern ◽  
Slug Flow ◽  
Boiling Heat Transfer ◽  
Small Diameter ◽  
Heat Fluxes ◽  
Mean Deviation ◽  
Physical Parameters ◽  
Transfer Coefficients ◽  
Two Phase

Results of a study on boiling heat transfer of refrigerant R-113 in a small-diameter (2.92 mm) tube are reported. Local heat transfer coefficients are measured for a range of heat flux (8.8–90.75 kW/m2), mass flux (50–300 kg/m2s), and equilibrium mass quality (0–0.9). The measured coefficients are used to evaluate 10 different heat transfer correlations, some of which have been developed specifically for refrigerants. High heat fluxes and low mass fluxes are inherent in small channels, and this combination results in high boiling numbers. In addition, based on a flow pattern map developed from adiabatic experiments with air-water mixtures, it has been shown that small-diameter channels produce a slug flow pattern over a large range of parameters when compared with larger-diameter channels. The effects of high boiling number and slug flow pattern lead to domination by a nucleation mechanism. As a result, the two-phase correlations that predicted this dominance also predicted the data the best when they properly modeled the physical parameters. The correlation of Lazarek and Black (1982) predicted the data very well. It is also shown that a simple form, suggested by Stephan and Abdelsalam (1980) for nucleate pool boiling, correlates the data equally well; both correlations are within a mean deviation of less than 13 percent. Results are applicable to boiling in compact heat exchangers.

scholarly journals Effect of Integrating Metal Wire Mesh with Spray Injection for Liquid Piston Gas Compression

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3723
Author(s):  
Barah Ahn ◽  
Vikram C. Patil ◽  
Paul I. Ro
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Heat Transfer Enhancement ◽  
Metal Wire ◽  
Wire Mesh ◽  
Transfer Enhancement ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Gas Compression ◽  
Liquid Piston

Heat transfer enhancement techniques used in liquid piston gas compression can contribute to improving the efficiency of compressed air energy storage systems by achieving a near-isothermal compression process. This work examines the effectiveness of a simultaneous use of two proven heat transfer enhancement techniques, metal wire mesh inserts and spray injection methods, in liquid piston gas compression. By varying the dimension of the inserts and the pressure of the spray, a comparative study was performed to explore the plausibility of additional improvement. The addition of an insert can help abating the temperature rise when the insert does not take much space or when the spray flowrate is low. At higher pressure, however, the addition of spacious inserts can lead to less efficient temperature abatement. This is because inserts can distract the free-fall of droplets and hinder their speed. In order to analytically account for the compromised cooling effects of droplets, Reynolds number, Nusselt number, and heat transfer coefficients of droplets are estimated under the test conditions. Reynolds number of a free-falling droplet can be more than 1000 times that of a stationary droplet, which results in 3.95 to 4.22 times differences in heat transfer coefficients.

Heat Transfer in a Surfactant Drag-Reducing Solution—A Comparison With Predictions for Laminar Flow

2005 ◽  
Vol 128 (6) ◽  
pp. 557-563 ◽  
Author(s):  
Paul L. Sears ◽  
Libing Yang
Keyword(s):  
Heat Transfer ◽  
Laminar Flow ◽  
Reynolds Numbers ◽  
High Heat ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Nusselt Numbers ◽  
Drag Reducing Additive ◽  
Good Agreement

Heat transfer coefficients were measured for a solution of surfactant drag-reducing additive in the entrance region of a uniformly heated horizontal cylindrical pipe with Reynolds numbers from 25,000 to 140,000 and temperatures from 30to70°C. In the absence of circumferential buoyancy effects, the measured Nusselt numbers were found to be in good agreement with theoretical results for laminar flow. Buoyancy effects, manifested as substantially higher Nusselt numbers, were seen in experiments carried out at high heat flux.

Heat Transfer and Pressure Drop Correlations for Square Channels With 45 Deg Ribs at High Reynolds Numbers

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Huitao Yang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Cooling Passage

Systematic experiments are conducted to measure heat transfer enhancement and pressure loss characteristics on a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 45 deg parallel ribs. Copper plates fitted with a silicone heater and instrumented with thermocouples are used to measure regionally averaged local heat transfer coefficients. Reynolds numbers studied in the channel range from 30,000 to 400,000. The rib height (e) to hydraulic diameter (D) ratio ranges from 0.1 to 0.18. The rib spacing (p) to height ratio (p/e) ranges from 5 to 10. Results show higher heat transfer coefficients at smaller values of p/e and larger values of e/D, though at the cost of higher friction losses. Results also indicate that the thermal performance of the ribbed channel falls with increasing Reynolds numbers. Correlations predicting Nusselt number (Nu) and friction factor (f¯) as a function of p/e, e/D, and Re are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+), p/e, and e/D.

A Numerical and Experimental Investigation of Turbulent Heat Transport Downstream From an Abrupt Pipe Expansion

1983 ◽  
Vol 105 (4) ◽  
pp. 862-869 ◽  
Author(s):  
R. S. Amano ◽  
M. K. Jensen ◽  
P. Goel
Keyword(s):  
Heat Transfer ◽  
Numerical Solutions ◽  
Numerical Study ◽  
Separated Flow ◽  
Flow Region ◽  
Reynolds Numbers ◽  
Turbulent Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Pipe Expansion

An experimental and numerical study is reported on heat transfer in the separated flow region created by an abrupt circular pipe expansion. Heat transfer coefficients were measured along the pipe wall downstream from an expansion for three different expansion ratios of d/D = 0.195, 0.391, and 0.586 for Reynolds numbers ranging from 104 to 1.5 × 105. The results are compared with the numerical solutions obtained with the k ∼ ε turbulence model. In this computation a new finite difference scheme is developed which shows several advantages over the ordinary hybrid scheme. The study also covers the derivation of a new wall function model. Generally good agreement between the measured and the computed results is shown.

Heat Transfer and Friction in Channels With Very High Blockage 45° Staggered Turbulators

2003 ◽  
Author(s):  
Jeremy C. Bailey ◽  
Ronald S. Bunker
Keyword(s):  
Heat Transfer ◽  
Reynolds Numbers ◽  
Transfer Coefficients ◽  
Flow Area ◽  
Test Technique ◽  
Heat Transfer Coefficients ◽  
Smooth Channel ◽  
Constant Pitch ◽  
Transfer Behavior ◽  
Very High

Heat transfer and friction coefficients have been measured within a rectangular passage of aspect ratio 0.4 containing 45-degree staggered turbulators of very high blockage. Using a constant pitch-to-height ratio of 10 for all geometries, turbulator height-to-channel hydraulic diameter ratios from 0.193 to 0.333 were investigated. This range of e/D creates actual channel blockage ratios e/H from 0.275 to 0.475, presenting significant flow area restrictions. A liquid crystal test technique is used to obtain both detailed heat transfer behavior on the surfaces between turbulators, as well as averaged fully developed heat transfer coefficients. Reynolds numbers from 20000 to 100000 were tested. Nusselt number enhancements of up to 3.6 were obtained over that of a smooth channel, with friction coefficient enhancements of as much as 65. In contrast to low-blockage turbulated channels, the 45-degree turbulated Nu is found to be lower than that at 90-degree orientation, given very similar e/D and e/H values.

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