A New Heat Transfer Correlation and Flow Regime Map for Tube Bundles

1990 ◽  
Vol 112 (1) ◽  
pp. 150-156 ◽  
Author(s):  
Y. A. Hassan ◽  
T. K. Blanchat
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Steam Generator ◽  
Tube Bundle ◽  
Nucleate Boiling ◽  
Heat Transfer Correlation ◽  
Transfer Coefficients ◽  
Tube Bundles ◽  
Regime Map ◽  
Flow Regime Map

A RELAP5/MOD2 computer code model for a once-through steam generator has been developed. The calculated heat transfer in the nucleate boiling flow was underpredicted as shown by a predicted superheat of only 11°C (20°F), whereas plant values range from 22–30°C (40–60°F). Existing heat transfer correlations used in thermal-hydraulic computer codes do not provide accurate predictions of the measurement-derived secondary convective heat transfer coefficients for steam generators because they were developed for flow inside tubes, not tube bundles. The RELAP5/MOD2 flow regime map was modified to account for flow across bundles. This modified flow regime map predicts better transition criteria between bubbly-to-slug and slug-to-annular flow. Consequently, improved saturated conditions for the fluid flow at the entrance to the boiler were obtained. A modified Chen-type heat transfer correlation was developed to predict the boiling heat transfer for steam generator tube bundle geometries. This correlation predicts better superheat.

An Experimental Investigation of Flow Patterns During Condensation of HFC Refrigerants in Horizontal Micro-Fin Tubes

2019 ◽  
Vol 27 (01) ◽  
pp. 1950010
Author(s):  
Sanjeev Singh ◽  
Rajeev Kukreja
Keyword(s):  
Heat Transfer ◽  
Flow Regime ◽  
Flow Regimes ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Horizontal Tubes ◽  
Regime Map ◽  
Fin Tubes ◽  
Flow Regime Map

Condensation heat transfer coefficients and flow regimes in two different horizontal micro-fin tubes are examined during the condensation of refrigerants R-134a and R-410A. The present investigation has focused on determination and prediction of condensation heat transfer coefficients and finding the interrelation between heat transfer coefficients and the prevailing flow regimes. During flow visualization, flow regimes have been captured using borosilicate glass tube at inlet and outlet of the test condenser using high speed digital camera. Stratified, stratified wavy, wavy annular, annular, slug and plug flows have been observed at different mass fluxes and vapor qualities of the refrigerants. The observed flow regimes are compared with the existing flow regime maps proposed by Breber et al. [Prediction of horizontal tube side condensation of pure components using flow regime criteria, J. Heat Transfer 102 (1980) 471–476], Tandon et al. [A new flow regime map for condensation inside horizontal tubes, J. Heat Transfer 104 (1982) 763–768.] and Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] Thome et al. [Condensation in horizontal tubes, part 2: New heat transfer model based on flow regimes, Int. J. Heat Mass Transfer 46 (2003) 3365–3387.] flow regime map shows good agreement with experimental data.

Condensation Heat Transfer of Soliman Flow Pattern in Mini-Channel

2006 ◽  
Author(s):  
Q. Chen ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Flow Pattern ◽  
Flow Regime ◽  
Flow Region ◽  
Condensation Heat Transfer ◽  
Heat Transfer Correlation ◽  
Transfer Coefficients ◽  
Annular Regime ◽  
Fin Tubes

The condensation heat transfer for R134a in the two kinds of in-tube three-dimensional (3-D) micro-fin tubes with different geometries is experimentally investigated. Based on the flow pattern observations, the flow patterns in the Soliman flow regime map are divided into two-flow regimes; one with the vapor-shear-dominant annular regime and the other with the gravitational-force-dominant stratified-wavy regime. In the annular regime, the heat transfer coefficients of the two kinds of in-tube 3-D micro-fin tubes decreases as the vapor quality decreases. The regressed condensation heat transfer correlation from the experimental data of the annular flow region is obtained. The dispersibility of the experimental data is inside the limits of ±25%. In the stratified-wavy regime, the average heat transfer coefficient of the two kinds of in-tube 3-D micro fin tubes increases as the mass flux increases and the number of micro fins in the 3-D micro-fin tube is not the controlling factor for performance of a condensation heat transfer. The regressed condensation heat transfer correlation of the stratified-wavy flow regime is experimentally obtained. The dispersibility of the experimental data is inside the limits of ±22%. Combined with the criteria of flow pattern transitions, the correlations can be used for the design of a condenser with 3-D micro fin tubes.

Nucleate Boiling in Thermally Developing and Fully Developed Laminar Falling Water Films

1988 ◽  
Vol 110 (1) ◽  
pp. 221-228 ◽  
Author(s):  
M. Cerza ◽  
V. Sernas
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Nucleate Boiling ◽  
Heat Transfer Correlation ◽  
Transfer Coefficients ◽  
Number Range ◽  
Flow Rates ◽  
Entry Length ◽  
Heat Transfer Coefficients ◽  
Water Films

This paper reports an experimental investigation of nucleate boiling in thin water films falling down the outside of a cylindrical heated tube. A mathematical model for the convective (nonboiling) heat transfer coefficient in the laminar thermal entry length was developed and used as a comparison to the experimental boiling heat transfer coefficients. A heat transfer correlation based on mechanistic arguments is presented and is shown to represent the experimental data fairly well. The experimental data were also compared with existing heat transfer data in the literature. The flow rates utilized in this study corresponded to a Reynolds number range from 670 and 4300 and the heat flux range was 6 to 70 kW/m2.

scholarly journals Influence of Coiling Direction of Helical Tube Bundles on the Thermal-Hydraulics of the HTGR Steam Generator

2021 ◽  
Vol 2048 (1) ◽  
pp. 012032
Author(s):  
Weikai Gao ◽  
Xiaoyang Xie ◽  
Xiaowei Li ◽  
Xinxin Wu
Keyword(s):  
Heat Transfer ◽  
Opposite Direction ◽  
Tube Bundle ◽  
Tangential Velocity ◽  
Transfer Coefficients ◽  
Direction Parallel ◽  
Helical Tube ◽  
Tube Bundles ◽  
Parallel Tube ◽  
Coiling Direction

Abstract Helical tube bundles were usually adopted in the steam generators (SGs) or intermediate heat exchangers (IHXs) of high temperature gas-cooled reactors (HTGRs). Heat transfer tubes in neighboring tube layers can be coiled in the same direction or in the opposite direction. The coiling direction has influences on the thermal-hydraulic performances of the SGs or IHXs. The cross flow convection over helical tube bundles with neighboring tube layers having the same coiled direction and opposite coiled direction were numerically investigated. Reynolds stress model with standard wall functions was used for the turbulence modeling. For a helical tube bundle with neighboring layers coiled in the same direction (parallel tube layers), the tangential velocity along the coiled circumferential direction could be observed obviously. For a helical tube bundle with neighboring layers coiled in the opposite direction (crossed tube layers), there is no average tangential velocity of the whole flow filed. And the streamlines of the fluid are very complex. The flow resistances and heat transfer coefficients over helical tube bundle with parallel tube layers and crossed tube layers were compared. Although the heat transfer over helical tube bundles with crossed tube layers was 9.39% smaller than that with parallel tube layers, the pressure drop over tube bundle with crossed tube layers was much smaller compared with those with parallel tube layers.

Boiling Characteristics of Small Multitube Bundles

1987 ◽  
Vol 109 (3) ◽  
pp. 753-760 ◽  
Author(s):  
A. M. C. Chan ◽  
M. Shoukri
Keyword(s):  
Heat Transfer ◽  
Tube Bundle ◽  
Power Input ◽  
Nucleate Boiling ◽  
Heat Fluxes ◽  
Tube Surface ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Lower Heat

Boiling characteristics of multitube bundles have been investigated experimentally. Small bundles of up to nine rows were used. Void fraction profiles in the test vessel, tube surface temperatures, power input to individual tubes, and critical heat fluxes were measured for different bundle arrangements and boiling conditions. The data were used to study the system hydrodynamics, bundle heat transfer coefficients, and bundle critical heat flux. The data showed that for lower heat fluxes, the heat transfer characteristics are affected by the system hydrodynamics resulting in higher heat transfer coefficients, whereas at higher heat fluxes nucleate boiling is the dominant mechanism. The data also showed that within a tube bundle, the vapor rising from lower tubes enhances the CHF characteristics of the upper tubes.

EHD-Enhanced Boiling Coefficients and Visualization of R-134a Over Enhanced Tubes

1997 ◽  
Vol 119 (2) ◽  
pp. 332-338 ◽  
Author(s):  
K. Cheung ◽  
M. M. Ohadi ◽  
S. Dessiatoun ◽  
A. Singh
Keyword(s):  
Heat Transfer ◽  
Flow Visualization ◽  
Boiling Heat Transfer ◽  
Tube Bundle ◽  
Pool Boiling ◽  
Nucleate Boiling ◽  
Transfer Coefficients ◽  
Surface Geometry ◽  
Pool Boiling Heat Transfer ◽  
R 134A

In an earlier study by the authors, the applicability of the EHD technique for augmentation of pool boiling heat transfer of R-134a in a tube bundle was demonstrated. This paper reports additional experiments involving optimization of the electrode/heat transfer surface geometry as well as flow visualization studies that provide improved understanding of the EHD-enhanced pool boiling heat transfer in a tube bundle. Utilizing the flow visualization studies, it is demonstrated that combined electroconvection and improved nucleate boiling dynamics give rise to the augmented heat transfer coefficients.

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