scholarly journals Prediction of Heat Transfer during Condensation in Non-Circular Channels

Inventions ◽  
2019 ◽  
Vol 4 (2) ◽  
pp. 31
Author(s):  
Mirza M. Shah
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Mass Flux ◽  
Entire Range ◽  
Hydraulic Diameter ◽  
The Other ◽  
Mean Absolute Deviation ◽  
Absolute Deviation ◽  
Reduced Pressure ◽  
Data Points

It is desirable to know whether correlations for condensation in round tubes can be used for non-circular channels. To investigate this matter, a number of well-known correlations for mini and macro channels as well as some for flattened channels were compared to a database for condensation in non-circular channels. Data included square, rectangular, triangular, semi-circular, drum, N, and W shaped channels as well as flattened tubes. The data included 15 fluids, hydraulic diameter 0.067 to 1.46 mm, aspect ratio 0.14 to 7, reduced pressure 0.045 to 0.77, and mass flux from 48 to 1000 kgm−2s−1. None of the correlations worked well for flattened tubes. Data for all other shapes were best predicted by the Shah correlation with mean absolute deviation of 20.1% with 1120 data points from 22 sources. None of the other correlations was found satisfactory over the entire range.

Improved General Correlation for Heat Transfer During Gas–Liquid Flow in Horizontal Tubes

2018 ◽  
Vol 10 (5) ◽  
Author(s):  
Mirza M. Shah
Keyword(s):  
Heat Transfer ◽  
Liquid Mixtures ◽  
Mean Absolute Deviation ◽  
Absolute Deviation ◽  
Earth Gravity ◽  
Horizontal Tubes ◽  
New Correlation ◽  
Wide Range ◽  
Data Points ◽  
Gas Liquid Flow

Heat transfer to two-component gas–liquid mixtures is needed in many industries but there is lack of a well-verified predictive method. A correlation is presented for heat transfer during flow of gas–liquid nonboiling mixtures in horizontal tubes. It has been verified with a wide range of data that includes tube diameters of 4.3–57 mm, pressures from 1 to 4.1 bar, temperatures from 12 to 62 °C, gravity <0.1% to 100% earth gravity, liquid Reynolds number from 9 to 1.2 × 105, and ratio of gas and liquid velocities from 0.24 to 9298. The 946 data points from 18 sources are predicted with mean absolute deviation (MAD) of 19.2%. The same data were compared to five other correlations; they had much larger deviations. Therefore, the new correlation is likely to be helpful in more accurate designs.

Prediction of Heat Transfer During Saturated Boiling in Helical Coils

2019 ◽  
Vol 11 (3) ◽  
Author(s):  
Mirza M. Shah
Keyword(s):  
Heat Transfer ◽  
Heat Exchangers ◽  
Absolute Deviation ◽  
Reduced Pressure ◽  
Flow Rates ◽  
Data Points ◽  
Comprehensive Comparison ◽  
Helical Coils ◽  
Saturated Boiling ◽  
Good Agreement

Heat exchangers with boiling in coils are widely used in the industry. Various researchers have recommended different correlations for heat transfer but there has been no comprehensive comparison of data and correlations to identify the most reliable ones. This was done in the present study. Eight correlations for straight tubes and six for coils were compared with data from 12 studies. The data included four fluids, tube diameters 2.8–14.5 mm, coil to tube diameter ratios 12–107, reduced pressure 0.0046–0.7857, flow rates 80–1200 kg m−2 s−1, and boiling number 0.16–13.6 × 104. None of the correlations for coils were found satisfactory. Four general correlations for straight tubes gave good agreement with the 484 data points, mean absolute deviation (MAD) being 19.8–22.6%.

A Correlation for Heat Transfer to Two-Component Gas-Liquid Flowing in Vertical Channels

2018 ◽  
Author(s):  
Mirza M. Shah
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Liquid Mixtures ◽  
Mean Absolute Deviation ◽  
Absolute Deviation ◽  
New Correlation ◽  
Rectangular Channels ◽  
Wide Range ◽  
Two Component ◽  
Data Points

A general correlation is presented for heat transfer during flow of gas-liquid mixtures flowing in vertical channels prior to dryout. It has been verified with a wide range of data that include upwards and downwards flow in heated and cooled tubes, annuli, and rectangular channels. The data are from 19 studies and include 14 gas-liquid mixtures with a very wide range of properties. The parameters include pressure 1 to 6.9 bars, temperature 16 to 115 oC, liquid Reynolds number from 2 to 127231, superficial gas and liquid velocities up to 87 and 13 m/s respectively, and ratio of superficial gas and liquid velocities 0.03 to 1630. The 1022 data points are predicted by the new correlation with mean absolute deviation (MAD) of 18.1 %. Several other correlations were also compared to the same data and had much larger deviations.

Heat Transfer for High Aspect Ratio Rectangular Channels in a Stationary Serpentine Passage With Turbulated and Smooth Surfaces

2013 ◽  
Author(s):  
Matthew A. Smith ◽  
Randall M. Mathison ◽  
Michael G. Dunn
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Aspect Ratio ◽  
Flow Behavior ◽  
Reynolds Numbers ◽  
Hydraulic Diameter ◽  
Internal Cooling ◽  
Number Range ◽  
Aspect Ratios ◽  
Parallel Configuration

Heat transfer distributions are presented for a stationary three passage serpentine internal cooling channel for a range of engine representative Reynolds numbers. The spacing between the sidewalls of the serpentine passage is fixed and the aspect ratio (AR) is adjusted to 1:1, 1:2, and 1:6 by changing the distance between the top and bottom walls. Data are presented for aspect ratios of 1:1 and 1:6 for smooth passage walls and for aspect ratios of 1:1, 1:2, and 1:6 for passages with two surfaces turbulated. For the turbulated cases, turbulators skewed 45° to the flow are installed on the top and bottom walls. The square turbulators are arranged in an offset parallel configuration with a fixed rib pitch-to-height ratio (P/e) of 10 and a rib height-to-hydraulic diameter ratio (e/Dh) range of 0.100 to 0.058 for AR 1:1 to 1:6, respectively. The experiments span a Reynolds number range of 4,000 to 130,000 based on the passage hydraulic diameter. While this experiment utilizes a basic layout similar to previous research, it is the first to run an aspect ratio as large as 1:6, and it also pushes the Reynolds number to higher values than were previously available for the 1:2 aspect ratio. The results demonstrate that while the normalized Nusselt number for the AR 1:2 configuration changes linearly with Reynolds number up to 130,000, there is a significant change in flow behavior between Re = 25,000 and Re = 50,000 for the aspect ratio 1:6 case. This suggests that while it may be possible to interpolate between points for different flow conditions, each geometric configuration must be investigated independently. The results show the highest heat transfer and the greatest heat transfer enhancement are obtained with the AR 1:6 configuration due to greater secondary flow development for both the smooth and turbulated cases. This enhancement was particularly notable for the AR 1:6 case for Reynolds numbers at or above 50,000.

A Correlation for Heat Transfer to Gas–Solid Suspensions Flowing in Pipes

2019 ◽  
Vol 12 (2) ◽  
Author(s):  
Mirza M. Shah
Keyword(s):  
Heat Transfer ◽  
Chemical Processing ◽  
Absolute Deviation ◽  
Solids Loading ◽  
New Correlation ◽  
Accurate Design ◽  
Wide Range ◽  
Data Points ◽  
Loading Ratio ◽  
Vertical Up

Abstract Heat transfer to flowing gas–solid mixtures in pipes is required in many applications including chemical processing, pneumatic transport, and nuclear reactors but no well-verified method for predicting heat transfer is available. A new correlation is presented, which has been validated with a wide range of data that includes a variety of particles (minerals, metals) in several gases. Particle diameters range from 13 to 1130 µm, pipe diameters 5.1 to 77 mm, and the solids loading ratio of 0–520. Flow orientations include horizontal, vertical up, and vertical down. The new correlation has a mean absolute deviation (MAD) of 18.9% with 630 data points from 20 studies. The same data were also compared with six published correlations. Their MAD ranged from 35% to 57%. Hence, the new correlation is likely to help in more accurate design.

General Correlation for Heat Transfer During Two-Component Gas-Liquid Flow in Horizontal Pipes

2018 ◽  
Author(s):  
Mirza M. Shah
Keyword(s):  
Heat Transfer ◽  
Liquid Mixtures ◽  
Absolute Deviation ◽  
Horizontal Pipes ◽  
Earth Gravity ◽  
Horizontal Tubes ◽  
Wide Range ◽  
Two Component ◽  
Data Points ◽  
Gas Liquid Flow

Heat transfer to two-component gas-liquid mixtures is needed in many industries but there is lack of a well-verified predictive method. A correlation is presented for heat transfer during flow of gas-liquid non-boiling mixtures in horizontal tubes. It has been verified with a wide range of data that includes: tube diameters 4.3 to 57 mm, pressures from 1 to 4.1 bar, temperatures from 12 to 62 °C, gravity < 0.1 % to 100 % earth gravity, liquid Reynolds number from 9 to 1.2E5, and ratio of gas and liquid velocities from 0.24 to 9298. The 946 data points from 18 sources are predicted with mean absolute deviation of 19.2 %. The same data were compared to several other correlations; they had much larger deviations.

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.

General Correlation for Heat Transfer to Gas–Liquid Flow in Vertical Channels

2018 ◽  
Vol 10 (6) ◽  
Author(s):  
Mirza M. Shah
Keyword(s):  
Heat Transfer ◽  
Liquid Mixtures ◽  
Absolute Deviation ◽  
General Correlation ◽  
New Correlation ◽  
Rectangular Channels ◽  
Wide Range ◽  
Data Points ◽  
Gas Liquid Flow ◽  
Dry Out

Abstract A general correlation is presented for heat transfer during flow of gas–liquid mixtures flowing in vertical channels prior to dry out. It has been verified with a wide range of data that include upward and downward flow in heated and cooled tubes, annuli, and rectangular channels. The data are from 19 studies and include 14 gas–liquid mixtures with a wide range of properties. The parameters include pressure 1–6.9 bar, temperature 16–115 °C, liquid Reynolds number from 2 to 127,231, superficial gas and liquid velocities up to 87 and 13 m/s, respectively, and ratio of superficial gas and liquid velocities 0.03–1630. The 1022 data points are predicted by the new correlation with mean absolute deviation (MAD) of 18.1%. Several other correlations were also compared to the same data and had MAD of 28.6–45.5%.

Measurement of Condensation Heat Transfer Coefficients at Near-Critical Pressures in Refrigerant Blends

2006 ◽  
Vol 129 (8) ◽  
pp. 958-965 ◽  
Author(s):  
Yirong Jiang ◽  
Biswajit Mitra ◽  
Srinivas Garimella ◽  
Ulf C. Andresen
Keyword(s):  
Heat Transfer ◽  
Mass Flux ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Condensation Heat Transfer ◽  
Liquid Region ◽  
Transfer Coefficients ◽  
Reduced Pressure ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes

This paper presents the results of an experimental study on condensation heat transfer of refrigerant blends R404A and R410A flowing through horizontal tubes of 9.4 and 6.2mm inner diameter at nominal pressures of 80% and 90% of the critical pressure. Local heat transfer coefficients were measured for the mass flux range 200<G<800kg∕m2‐s in small quality increments over the entire vapor-liquid region. Heat transfer coefficients increased with quality and mass flux, while the effect of reduced pressure was not very significant within this range of pressures. The heat transfer coefficients increased with a decrease in diameter.

scholarly journals Review of the Wall Temperature Prediction Capability of Available Correlations for Heat Transfer at Supercritical Conditions of Water

2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
Dhanuskodi Ramasamy ◽  
Arunagiri Appusamy ◽  
Anantharaman Narayanan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Wall Temperature ◽  
Mass Flux ◽  
Flux Ratio ◽  
Temperature Prediction ◽  
Heat Transfer Deterioration ◽  
Error Band ◽  
Wide Range ◽  
Data Points

The validity of the wall temperature predictions by 18 correlations available in the literature for supercritical heat-transfer regimes of water was verified for 12 experimental datasets consisting of 355 data points available in the literature. The correlations were ranked based on criteria like % data with <5% error, % data with <10°C error and minimum error band in temperature prediction. Details of the best fitting correlations were tabulated. The analysis indicated that for normal heat-transfer conditions, most of the correlations give close predictions. However, at deteriorated heat transfer regimes, only very few prediction points are closer to experimental value. Also, in the ranking process, the first position keeps varying, and no one correlation shall be said as the best for all experiments. Evaluation of the applicability of heat flux to mass-flux-ratio-based prediction of heat-transfer deterioration indicated 75% agreement. The empirical formulae linking mass flux for the prediction of the starting heat flux for heat-transfer deterioration indicated 58.33% of agreement. This review indicated that continued precise experimentation covering wide range of parameter conditions near pseudocritical regime and development of correlations is felt necessary for the accurate prediction of supercritical fluid heat transfer.

Sign in / Sign up

Export Citation Format

Share Document