CRITICAL HEAT FLUX FOR LARGE DIAMETER STEAM GENERATING TUBES WITH CIRCUMFERENTIALLY VARIABLE AND UNIFORM HEATING

1974 ◽  
Author(s):  
B. Chojnowski ◽  
P. W. Wilson
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Large Diameter ◽  
Uniform Heating

Study on DNB-Type Critical Heat Flux With Chopper-Cosine Axial Heat Flux Distributions

2014 ◽  
Author(s):  
Dawei Zhao ◽  
Wanyu Xiong ◽  
Wenxing Liu ◽  
Jianjun Xu
Keyword(s):  
Heat Flux ◽  
Critical Heat Flux ◽  
Present Model ◽  
Reactor Design ◽  
Nucleate Boiling ◽  
Uniform Heat Flux ◽  
Good Prediction ◽  
Uniform Heating ◽  
Comparison Results ◽  
Axial Heat

Departure from nucleate boiling (DNB) type critical heat flux (CHF) is one of most important thermal criteria for nuclear reactor design. Concerning on the typical chopper-cosine heat flux profile at reactor core, it is of great significance to predict the CHF under non-uniform heating conditions for reactor design and the performance promotion of reactor system. Some correction factors are proposed for the prediction of CHF with non-uniform axial power shapes. In this study, a mechanistic DNB-type CHF model has been developed on the basis of liquid sublayer dryout mechanism. The non-uniform axial heat flux is taken into account of upstream memory effect on boiling crisis in this model. The predictions of present model and Tong’s non-uniform heat flux shape factor method are compared with the experimental results in the vertical tube with chopper-cosine axial heat flux distributions. The comparison results show the present model has fairly good prediction capability for DNB-type CHF under non-uniform heating condition.

scholarly journals Critical Heat Flux of Flowing Water in Tube for Pressure Up to Near Critical Point—Experiment and Prediction

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Yuzhou Chen ◽  
Minfu Zhao ◽  
Keming Bi ◽  
Bin Yang ◽  
Dongxu Zhang ◽  
...  
Keyword(s):  
Heat Flux ◽  
Critical Point ◽  
Critical Heat Flux ◽  
Previous Experiment ◽  
Empirical Relation ◽  
Total Power ◽  
Uniform Heating ◽  
Local Quality ◽  
Inner Diameter ◽  
Heated Length

Critical heat flux (CHF) experiment with uniform heating was performed in a tube of 8.2 mm in inner diameter and 2.4 m in heated length. The water flowed upward through the test section. The pressure covered the range from 8.6 to 20.8 MPa, mass flux 1157 to 3776 kg/m2s, inlet quality −2.79 to −0.08 (subcooling 19–337 °C), and local quality −0.97 to 0.53. For the pressure close to the near-critical point, the CHF decreased substantially with the pressure increasing. For the subcooling larger than a certain value, the CHF was related to the local condition. But for low subcooling and saturated condition, the CHF was related to the total power. The present results were in agreement with the previous experiment for the same local subcooled condition. Based on the present experimental results with subcooled and saturated conditions an empirical relation of the CHF was presented.

Experimental Evaluation of Critical Heat Flux in Downward-Facing Boiling on SS304 L Flat Plate Relevant to In-Calandria Retention in PHWRs

2020 ◽  
Vol 6 (3) ◽  
Author(s):  
Sumit V. Prasad ◽  
A. K. Nayak
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Natural Convection ◽  
Flat Plate ◽  
Critical Heat Flux ◽  
Outer Surface ◽  
Flat Surface ◽  
Large Diameter ◽  
Convection Heat Transfer ◽  
Heat Removal

Abstract Retention of corium inside the calandria vessel (CV) by externally cooling it by calandria vault water is essential to mitigate severe accidents in pressurized heavy water reactor (PHWR). The thermal failure of CV can be prevented by effective decay heat removal on the outer surface of CV using vault water, which depends on the heat transfer behavior from the outer surface of CV to the vault water. Determination of limiting heat removal capability of vault subcooled water through outer surface of CV is very important. Since the CV has a very large diameter and length, the bottom most part of the CV almost behaves as a flat plate with downward natural convection boiling heat transfer. The natural convection heat transfer is lesser on the flat surface as compared to the curved surface of the CV. Thus, the critical heat flux (CHF) on the flat surface under downward boiling condition is the limiting CHF of the CV under external surface boiling scenario. In order to estimate CHF in this configuration with local boiling, experiments were carried out on a downward facing SS304 L flat plate simulating the conditions of CV of 700 MWel Indian PHWR. The pool boiling CHF obtained in this study is also compared with other earlier works.

Effects of Non-Uniform Circumferential Heating and Inclination on Critical Heat Flux in Smooth Round Tubes

2013 ◽  
Vol 291-294 ◽  
pp. 1657-1660
Author(s):  
Zhi Hong Hu ◽  
Ting Kuan Chen
Keyword(s):  
Heat Flux ◽  
Experimental Investigation ◽  
Critical Heat Flux ◽  
Mass Flux ◽  
Flux Ratio ◽  
Test Results ◽  
Uniform Heating ◽  
Average Heat ◽  
Peak Heat Flux ◽  
Vertical Tubes

Experimental investigation of the critical heat flux (CHF) in smooth round tubes with circumferentially variable heating was carried out. The riser tubes with 0, 20, 90-degree inclinations from the horizontal were electrically heated. The measurements were carried out for pressure between 13 and 21MPa, mass flux between 600 and 900kg/m2s. The peak-to average heat flux ratio was amounted to 1.6. CHF data of uniform heating were also tested. The test results show that the initial CHF is always observed at location of peak heat flux in vertical tubes with non-uniform heating. In horizontal and inclined tubes with side-heating the transit from a top to side initial indication of CHF occurs by increasing the mass flux and the pressure to certain values. The Initial CHF of non-uniformly heated tubes is fairly agreement with the values of uniformly heated tubes.

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