Experimental Study on Post-Dryout Heat Transfer of Dispersed Flow in Vertical Narrow Annuli

2004 ◽  
Author(s):  
Aye Myint ◽  
Wenxi Tian ◽  
Zhihui Li ◽  
Suizheng Qiu ◽  
Dounan Jia ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Velocity ◽  
Narrow Channel ◽  
Empirical Correlations ◽  
Annular Gap ◽  
Low Mass ◽  
Narrow Annuli ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

Forced convective post dryout heat transfer in narrow channel with 1.2 mm gap has been experimentally investigated with deionized water. The experiment was carried out with pressure ranging from 1.38 to 5.9 MPa and low mass velocity from 52.9 to 84.2 kg/m2 s. The experimental data were compared with well known empirical correlations such as Groeneveld, Polimik, Miropolskiy and Slaughterbeck and it was found that these correlations could not predict very well in narrow annular gap at low mass velocity. Based on the experimental data, the heat transfer coefficient increases with increasing heat flux, mass flux and pressure. A new empirical correlation for narrow annuli at low mass velocity was then developed which has a good agreement with the experimental data.

scholarly journals Influence of fin thickness on heat transfer and flow performance of a parallel flow evaporator

2019 ◽  
Vol 23 (4) ◽  
pp. 2413-2419 ◽  
Author(s):  
Haijun Li ◽  
Enhai Liu ◽  
Guanghui Zhou ◽  
Fengye Yang ◽  
Zhiyong Su ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Comprehensive Evaluation ◽  
Reynolds Numbers ◽  
Parallel Flow ◽  
Heat Transfer Factor ◽  
Heat Transfer Capacity ◽  
Fin Thickness ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

This paper studies numerically the influence of the louver?s fin thickness on heat transfer and flow performance of a parallel flow evaporator, a comprehensive evaluation and analysis of the five structures at different Reynolds numbers are systematically carried out. Comparison of the numerical results with the experimental data shows good agreement with maximal errors of 12.16% and 5.29% for the heat transfer factor and the resistance factor, respectively. The results show that the heat transfer coefficient and the pressure drop increase with the increase of the thickness of the louver fins when the Reynolds number is a constant. The analysis of the comprehensive evaluation factor shows that the A-type fin is the best, and it can effectively strengthen the heat exchange on the air side and improve the heat transfer capacity of the system. The research results can provide reference for the structural optimization of the louver fins.

Diameter Effects on Nucleate Pool Boiling for a Vertical Tube

2000 ◽  
Vol 123 (2) ◽  
pp. 400-404 ◽  
Author(s):  
Myeong-Gie Kang
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Heat Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Pool Boiling ◽  
Vertical Tube ◽  
Nucleate Pool Boiling ◽  
Vertical Orientation ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

Diameter effects on nucleate pool boiling heat transfer for a tube with vertical orientation have been obtained experimentally. According to the results (1) the heat transfer coefficient decreases as the tube diameter increases and the trend is more notable with a rougher surface, and (2) the experimental data is in good agreement with the Cornwell and Houston’s correlation within a ±20 percent scatter range.

Experimental Research on Dryout Point of Flow Boiling in Narrow Annuli

2006 ◽  
Author(s):  
Ge Ping Wu ◽  
Sui Zheng Qiu ◽  
Guang Hui Su ◽  
Dou Nan Jia
Keyword(s):  
Experimental Data ◽  
Heat Flux ◽  
Experimental Research ◽  
Mass Flux ◽  
Flow Boiling ◽  
Distilled Water ◽  
Empirical Correction ◽  
Low Mass ◽  
Narrow Annuli ◽  
Good Agreement

An experimental research on the dryout point of flow boiling in narrow annuli is conducted under low mass flux with 1.5mm and 1.0mm gap, respectively. Distilled water is used as work fluid, the range of pressure is from 2.0 to 4.0MPa and that of mass flux is 26.0∼69.0 kg/(m2 · s). The relation of CHF and critical qualities with mass flux and pressure are revealed. It is found that the critical qualities decrease with the mass flux and increase with the inlet qualities in externally heated annuli. Under the same conditions critical qualities in outer tube are always larger than that in inner tube. Кутателадзе’s correlations is cited and modified to predict the location of dryout and proved to be not a proper one. Considering in detail the effects of the geometry of annuli and heat flux on dryout, an empirical correction is finally developed to predict dryout point in narrow annuli under low mass flux condition which has a good agreement with experimental data.

Experimental Investigation of Flow Boiling Inside Three Three-Dimensional Surface Enhanced Heat Transfer Tubes

2017 ◽  
Author(s):  
Weiyu Tang ◽  
Zhengjiang Zhang ◽  
Jincai Du ◽  
Wei Li ◽  
Jincheng Han ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Experimental Investigation ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Velocity ◽  
Enhanced Heat Transfer ◽  
Low Mass ◽  
Respective Surface ◽  
Enhanced Surface ◽  
The Heat Transfer Coefficient

An Experimental investigation was conducted to compare the evaporation characteristics of R410A inside three newly developed horizontal enhanced heat transfer (EHT) tubes with the same OD12.70mm and ID11.50mm, and the result of them are compared with that of a plain tube. The inner enhanced surface of 1EHT tube consists of dimples/protrusions and petal arrays, while that of 2EHT-1 tube and 2EHT-2 tube is composed by longitudinal grooves and dimples of different depths. The mass velocities are in the range of 70kg/m2s-200kg/m2 s with a nominal saturation temperature fixed at 279K and the vapor quality in the test section varies from 0.2∼0.9. As the mass flux increases, both the heat transfer coefficient and pressure penalty increase accordingly. The heat transfer coefficient of EHT tubes can achieve 1.14–1.53 times higher than that of the smooth tube while the pressure gradients is 1.43–1.83 times larger than that of smooth tubes. Besides, the enhancement ratios of all the enhanced surface tubes are larger than their respective surface area ratio, and the enhancement ratio comparisons of heat transfer coefficient are made to obtain the enhancing mechanism. The results show that the EHT tubes appear higher performance at low mass fluxes. In all, the EHT1 tube has the best heat transfer performance at low mass velocity, which can be attributed to its special enhanced inner surface, resulting in the increase of nucleation sites, flow separation and turbulent fluctuations. The other two 2EHT tubes can enhance the evaporation greatly with small respective surface ratios as well as relatively little pressure drop penalty, and them shows outstanding performance especially at high mass velocity.

A Model for Convective Boiling in a Narrow Eccentric Annular Gap

1985 ◽  
Vol 107 (3) ◽  
pp. 613-619 ◽  
Author(s):  
C. R. Tong ◽  
M. J. Tan ◽  
S. G. Bankoff
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Steady State ◽  
Outer Wall ◽  
Line Contact ◽  
Convective Boiling ◽  
Eccentric Annulus ◽  
Annular Gap ◽  
Steady State Model ◽  
Good Agreement

A steady-state model is developed for convective boiling and dryout in an eccentric annulus with line contact between the heated inner wall and the adiabatic outer wall. The geometry and heat transfer conditions resemble those in a PWR steam generator, except for the lower pressure. Good agreement is shown with experimental data reported elsewhere.

Convective Heat Transfer at Minimum Fluidization Velocity for Gas-Solid Fluidized Beds

1999 ◽  
Author(s):  
Kal R. Sharma
Keyword(s):  
Heat Transfer ◽  
Fluidized Beds ◽  
Empirical Correlations ◽  
Transfer Coefficients ◽  
Minimum Fluidization Velocity ◽  
Heat Transfer Coefficients ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Semi Empirical ◽  
The Heat Transfer Coefficient

Abstract Experimentally measured values for the minimum fluidization velocities and time averaged local surface heat transfer coefficients are provided for 16 different cases of fluidizing conditions for gas-solid dense fluidized beds. Semi-empirical Correlations for the minimum fluidization velocity and the heat transfer coefficient at minimum fluidization velocities are provided. The implications of the Peclet number dependence in terms of diffusion and convection is discussed.

Heat Transfer Evaluation for a Two-Pass Smooth Wall Channel: Stationary and Rotating Cases

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Mandana S. Saravani ◽  
Nicholas J. DiPasquale ◽  
Ahmad I. Abbas ◽  
Ryoichi S. Amano
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Rotational Speed ◽  
Numerical Study ◽  
Flow Behavior ◽  
Smooth Wall ◽  
Eddy Simulation ◽  
Large Eddy ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

Abstract This study presents findings on combined effects of Reynolds number and rotational effect for a two-pass channel with a 180-deg turn, numerically and experimentally. To have a better understanding of the flow behavior and to create a baseline for future studies, a smooth wall channel with the square cross section is used in this study. The Reynolds number varies between 6000 and 35,000. Furthermore, by changing the rotational speed, the maximum rotation number of 1.5 is achieved. For the numerical investigation, large eddy simulation (LES) is utilized. Results from the numerical study show a good agreement with the experimental data. From the results, it can be concluded that increasing both Reynolds number and rotational speed is in favor of the heat transfer coefficient enhancement, especially in the turn region.

Post-Test Investigations of BFBT Critical Power Tests With Trace

2009 ◽  
Author(s):  
Marc Thieme ◽  
Wolfgang Tietsch ◽  
Rafael Macian ◽  
Victor Hugo Sanchez Espinoza
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Critical Power ◽  
The Core ◽  
Fine Mesh ◽  
The Us ◽  
Post Test ◽  
Trace Model ◽  
Good Agreement ◽  
Transfer Models

The validation of heat transfer models of safety analysis codes such as TRACE is very important due to the strong interaction of the thermal hydraulics parameters with the core neutronics. TRACE is the reference system code of the US NRC for LWR. It is being developed and extensively validated within the international CAMP-program. In this paper, the validation of heat transfer models of TRACE related to the prediction of the critical power is presented. The validation is based on a large number of critical power tests performed in the NUPEC BFBT (BWR Full-Size Fine-Mesh Bundle Tests) facility in Japan. These tests were analysed with the TRACE Version 5 RC 2. The comparison of predictions with the experimental data shows good agreement. The developed TRACE model and the comparison of experimental data with code results will be presented and discussed.

Heat Transfer Experiments in a Confined Jet Impingement Configuration Using Transient Techniques

2010 ◽  
Author(s):  
Florian Hoefler ◽  
Nils Dietrich ◽  
Jens von Wolfersdorf
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Direction ◽  
Jet Impingement ◽  
Thermochromic Liquid Crystal ◽  
Transient Techniques ◽  
Nusselt Numbers ◽  
The Heat Transfer Coefficient ◽  
Good Agreement

A confined jet impingement configuration has been investigated in which the matter of interest is the convective heat transfer from the airflow to the passage walls. The geometry is similar to gas turbine applications. The setup is distinct from usual cooling passages by the fact that no crossflow and no bulk flow direction are present. The flow exhausts through two staggered rows of holes opposing the impingement wall. Hence, a complex 3-D vortex system arises, which entails a complex heat transfer situation. The transient Thermochromic Liquid Crystal (TLC) method was used to measure the heat transfer on the passage walls. Due to the nature of the experiment, the fluid as well as the wall temperature vary with location and time. As a prerequisite of the transient TLC technique, the heat transfer coefficient is assumed to be constant over the transient experiment. Therefore, additional measures were taken to qualify this assumption. The linear relation between heat flux and temperature difference could be verified for all measurement sites. This validates the assumption of a constant heat transfer coefficient which was made for the transient TLC experiments. Nusselt number evaluations from all techniques show a good agreement, considering the respective uncertainty ranges. For all sites the Nusselt numbers range within ±9% of the values gained from the TLC measurement.

Experimental and Numerical Studies of Heat Transfer in Human Uteri During Cryoablation

2002 ◽  
Author(s):  
Jim S. Chen ◽  
Kevin Agnissey ◽  
Marla Wolfson ◽  
Charles Philips ◽  
Thomas Shaffer
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Temperature History ◽  
Rubber Sheet ◽  
Numerical Studies ◽  
Numerical Predictions ◽  
Silicone Rubber Sheet ◽  
Nicolson Scheme ◽  
Sheet Good ◽  
Good Agreement

This paper presents experimental and numerical studies of transient heat transfer inside the uterus during application of a PFC (perfluorochemical) fluid into the endometrium cavity in order to achieve cryoablation. The numerical prediction is based on a 1-D finite difference method of the bio-heat equation using the Crank Nicolson scheme. The numerical method is first validated by a 1-D physical model by measuring temperature history at several locations within a silicone rubber sheet. Good agreement, thus positive predictability, was obtained by comparing numerical predictions with the experimental data obtained from eight intact, hysterectomized uteri during cryoablation.

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