scholarly journals Numerical Study of the Impingement of Water Film on a Small Attached Bulging Plate on a Vertical Plane

2021 ◽  
Vol 9 ◽  
Author(s):  
Po Hu ◽  
Zhen Hu
Keyword(s):  
Cooling System ◽  
Numerical Study ◽  
Plane Surface ◽  
Vertical Plane ◽  
Heat Removal ◽  
Water Film ◽  
Loss Ratio ◽  
Water Storage Tank ◽  
Inner Surface ◽  
Condensed Water

In the passive containment cooling system of AP1000, the condensed water is expected to flow down on the inner surface of the steel wall of the containment, and recover to the in-containment refueling water storage tank (IRWST), therefore, to maintain the long-term coolability of the passive residual heat removal system. However, there are attached bulging plates on the inner surface for various engineering needs, such as supporting, and the impingement of condensed water film on these bulging plates can reduce the amount of the recovered water. In this article, a 3-D Eulerian wall film model in FLUENT was used to study a series of flow behaviors when a water film impinged on the bulging plate on a plane surface. The loss ratio of falling film impinging on attached plates of different sizes under different flow rates were calculated and in good agreement with the experiment results. Four stages of the film behavior during the impingement were identified and analyzed; in addition, the influences of the bulging height of attached plate and flow rate were studied. And a correlation between the loss ratio of impinging water film, the bulging height of the attached plate, and the Weber number was obtained.

Validation of Film Evaporation Model in GASFLOW-MPI

2018 ◽  
Author(s):  
Li Yabing ◽  
Zhang Han ◽  
Xiao Jianjun
Keyword(s):  
Experimental Data ◽  
Wall Temperature ◽  
Cooling System ◽  
Numerical Study ◽  
Thermal Power ◽  
Heat Removal ◽  
Air Velocity ◽  
Evaporation Model ◽  
Film Evaporation ◽  
Test Region

A dynamic film model is developed in the parallel CFD code GASFLOW-MPI for passive containment cooling system (PCCS) utilized in nuclear power plant like AP1000 and CAP1400. GASFLOW-MPI is a widely validated parallel CDF code and has been applied to containment thermal hydraulics safety analysis for different types of reactors. The essential issue for PCCS is the heat removal capability. Research shows that film evaporation contributes most to the heat removal capability for PCCS. In this study, the film evaporation model is validated with separate effect test conducted on the EFFE facility by Pisa University. The test region is a rectangle gap with 0.1m width, 2m length, and 0.6m depth. The water film flowing from the top of the gap is heated by a heating plate with constant temperature and cooled by countercurrent air flow at the same time. The test region model is built and analyzed, through which the total thermal power and evaporation rate are obtained to compare with experimental data. Numerical result shows good agreement with the experimental data. Besides, the influence of air velocity, wall temperature and gap widths are discussed in our study. Result shows that, the film evaporation has a positive correlation with air velocity, wall temperature and gap width. This study can be fundamental for our further numerical study on PCCS.

AP1000® Passive Cooling Containment Analysis of a Double-Ended LBLOCA With a 3D Gothic Model

2018 ◽  
Author(s):  
Samanta Estevez-Albuja ◽  
Gonzalo Jimenez ◽  
Kevin Fernández-Cosials ◽  
César Queral ◽  
Zuriñe Goñi
Keyword(s):  
Cooling System ◽  
Heat Removal ◽  
Water Tank ◽  
Local Pressure ◽  
Water Storage Tank ◽  
Passive Safety Systems ◽  
Containment Model ◽  
Loss Of Coolant Accident ◽  
Ac Power ◽  
Safety Systems

In order to enhance Generation II reactors safety, Generation III+ reactors have adopted passive mechanisms for their safety systems. In particular, the AP1000® reactor uses these mechanisms to evacuate heat from the containment by means of the Passive Containment Cooling System (PCS). The PCS uses the environment atmosphere as the ultimate heat sink without the need of AC power to work properly during normal or accidental conditions. To evaluate its performance, the AP1000 PCS has been usually modeled with a Lumped Parameters (LP) approach, coupled with another LP model of the steel containment vessel to simulate the accidental sequences within the containment building. However, a 3D simulation, feasible and motivated by the current computational capabilities, may be able to produce more detailed and accurate results. In this paper, the development and verification of an integral AP1000® 3D GOTHIC containment model, taking into account the shield building, is briefly presented. The model includes all compartments inside the metallic containment liner and the external shield building. Passive safety systems, such as the In-containment Refueling Water Storage Tank (IRWST) with the Passive Residual Heat Removal (PRHR) heat exchanger and the Automatic Depressurization System (ADS), as well as the PCS, are included in the model. The model is tested against a cold leg Double Ended Guillotine Break Large Break Loss of Coolant Accident (DEGB LBLOCA) sequence, taking as a conservative assumption that the PCS water tank is not available during the sequence. The results show a pressure and temperature increase in the containment in consonance with the current literature, but providing a greater detail of the local pressure and temperature in all compartments.

A Numerical Study of the Natural Convective Heat Transfer From a Partially Covered Recessed Isothermal Vertical Surface

2005 ◽  
Author(s):  
Patrick H. Oosthuizen
Keyword(s):  
Heat Transfer ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Numerical Study ◽  
Plane Surface ◽  
Vertical Wall ◽  
Vertical Plane ◽  
Adiabatic Wall ◽  
Isothermal Surface ◽  
Resistance To Heat

A numerical study of natural convective heat transfer from a heated isothermal vertical plane surface has been considered. There are relatively short horizontal adiabatic surfaces normal to the isothermal surface at the top and bottom of this isothermal surface these horizontal adiabatic wall surfaces then being joined to vertical adiabatic surfaces. There is a thin surface that offers no resistance to heat transfer that is parallel to the vertical isothermal surface and which partly covers this surface. The situation considered is a simplified model of a window, which is represented by the vertical isothermal wall section, that is recessed in a frame, which is represented by the horizontal adiabatic surfaces, which is mounted in a vertical wall, which is represented by the vertical adiabatic surfaces, and which is exposed to a large surrounding room. The window is covered by a partially open plane blind which is represented by the vertical thin surface that offers no resistance to heat transfer. The flow has been assumed to be laminar and two-dimensional. Fluid properties have been assumed constant except for the density change with temperature that gives rise to the buoyancy forces. The governing equations, written in dimensionless form, have been solved using a commercial finite-element based code. Results have only been obtained for a Prandtl number of 0.7.

A Numerical Study of Flow and Temperature Maldistribution in a Parallel Microchannel System for Heat Removal in Microelectronic Devices

2012 ◽  
Author(s):  
Manoj Siva ◽  
Arvind Pattamatta ◽  
Sarit Kumar Das
Keyword(s):  
Heat Exchanger ◽  
Cross Section ◽  
Design Theory ◽  
Cooling System ◽  
Search Algorithm ◽  
Numerical Study ◽  
Heat Removal ◽  
Flow Distribution ◽  
Microchannel Cooling ◽  
Flow Maldistribution

A common assumption in basic heat exchanger design theory is that fluid is distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. However in reality, uniform flow distribution is never achieved in a heat exchanger and is referred to as flow maldistribution. Flow maldistribution is generally well understood for the macrochannel system. But it is still unclear whether the assumptions underlying the flow distribution in conventional macrochannel heat exchangers hold good for microchannel system. In this regard, extensive numerical simulations are carried out in a ‘U’ type parallel micro-channel system in order to study flow and heat transfer maldistribution and validated with in-house experimental data. A detailed parametric analysis is carried out to characterize flow maldistribution in a microchannel system and to study the effect of geometrical factors such as number of channels, n, Area of cross section of the channel Ac, manifold cross section area Ap, and flow parameter such as Reynolds number, Re, on the pressure and temperature distribution. In order to minimize the variation in pressure and to reduce temperature hot spots in the microchannel, a Response surface based surrogate approximation (RSA) and a gradient based search algorithm are used to arrive at the best configuration of microchannel cooling system. A three level factorial design involving three parameters namely Ac/Ap, Re, n are considered. The results from the optimization indicate that the case of n = 5, Ac/Ap = 0.12, and Re = 100 is the best possible configuration to alleviate flow maldistribution and hotspot formation in microchannel cooling system.

A Numerical Study of Flow and Temperature Maldistribution in a Parallel Microchannel System for Heat Removal in Microelectronic Devices

2013 ◽  
Vol 5 (4) ◽  
Author(s):  
V. Manoj Siva ◽  
Arvind Pattamatta ◽  
Sarit Kumar Das
Keyword(s):  
Heat Exchanger ◽  
Cross Section ◽  
Design Theory ◽  
Cooling System ◽  
Search Algorithm ◽  
Numerical Study ◽  
Heat Removal ◽  
Flow Distribution ◽  
Microchannel Cooling ◽  
Flow Maldistribution

A common assumption in basic heat exchanger design theory is that fluid is distributed uniformly at the inlet of the exchanger on each fluid side and throughout the core. However, in reality, uniform flow distribution is never achieved in a heat exchanger and is referred to as flow maldistribution. Flow maldistribution is generally well understood for the macrochannel system. But it is still unclear whether the assumptions underlying the flow distribution in conventional macrochannel heat exchangers hold good for microchannel system. In this regard, extensive numerical simulations are carried out in a “U” type parallel microchannel system in order to study flow and heat transfer maldistribution and validated with in-house experimental data. A detailed parametric analysis is carried out to characterize flow maldistribution in a microchannel system and to study the effect of geometrical factors such as number of channels, n, Area of cross section of the channel Ac, manifold cross section area Ap, and flow parameter such as Reynolds number, Re, on the pressure and temperature distribution. In order to minimize the variation in pressure and to reduce temperature hot spots in the microchannel, a response surface based surrogate approximation and a gradient based search algorithm are used to arrive at the best configuration of microchannel cooling system. A three level factorial design involving three parameters namely Ac/Ap, Re, n are considered. The results from the optimization indicate that the case of n = 7, Ac/Ap = 0.69, and Re = 100 is the best possible configuration to alleviate flow maldistribution and hotspot formation in microchannel cooling system.

Experimental Study on the Performance of IIST Passive Core Cooling System

2002 ◽  
Author(s):  
Chin-Jang Chang ◽  
Chien-Hsiung Lee ◽  
Wen-Tan Hong ◽  
Lance L. C. Wang
Keyword(s):  
Nuclear Power ◽  
Cooling System ◽  
Heat Removal ◽  
General System ◽  
System Response ◽  
Water Storage Tank ◽  
The Core ◽  
Third Stage ◽  
Core Cooling

The purpose of this study is to conduct the experiments at the Institute of Nuclear Energy Research (INER) Integral System Test (IIST) facility for evaluation of the performance of the passive core cooling system (PCCS) during the cold-leg small break loss-of-coolant accidents (SBLOCAs). Five experiments were performed with (1) three different break sizes, 2%, 0.5%, and 0.2% (approximately corresponding to 1 1/4”, 2”, and 4” breaks for Maanshan nuclear power plant), and (2) 0.2% and 0.5% without actuation of the first-stage and third-stage automatic depressurization valve (ADS-1 and ADS-3) to initiate PCCS for assessing its capacity in accident management. The detailed descriptions of general system response and the interactions of core makeup tanks (CMTs), accumulators (ACCs), automatic depressurization system (ADS), passive residual heat Removal (PRHR), and in-containment refueling water storage tank (IRWST) on the core heat removal are included. The results show: (1) core long term cooling can be maintained for all cases following the PCCS procedures, (2) the core can be covered for the cases of the 0.2% and 0.5% breaks without actuation of ADS-1 and ADS-3.

Application of GOTHIC8.0 3D Model to Simulate Heat Removal Process in Containment Safety Verification via Integral Test (CERT)

2017 ◽  
Author(s):  
Guodong Wang ◽  
Shengjie Wei ◽  
Chenxiao Ni ◽  
Di Zhang ◽  
Zhe Wang
Keyword(s):  
3D Model ◽  
Cooling System ◽  
Heat Removal ◽  
Water Film ◽  
High Mass ◽  
Steel Shell ◽  
Safety Verification ◽  
Shell Surface ◽  
Integral Test ◽  
Removal Process

The purpose of this study is to establish a detailed three-dimensional (3D) model of containment safety verification via integral test (CERT) using the containment code GOTHIC 8.0. This paper presents the model construction and a typical CERT case for the model evaluation. In the typical CERT case, steam with high mass and energy is released to the test vessel to simulate the passive containment response during main steamline break (MSLB) accident. Heat removal process is accomplished primarily by absorption of energy by the gas volume and structures inside vessel, by condensation of steam on the inside shell surface, by heat conduction through the steel shell, and by evaporation of water film covered on the outer vessel shell surface. The main results of the typical CERT case are qualitatively compared with the results obtained from simulations with GOTHIC 8.0 code. From comparison, a verification of the code in terms of pressurization, temperature response, steam condensation and water film evaporation are carried out. The code analysis results are of significance on the research of thermal hydraulic phenomena which occur in the passive containment cooling system (PCS) during accidental sequences.

scholarly journals Numerical Study of a Cooling System Using Phase Change of a Refrigerant in a Thermosyphon

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3634
Author(s):  
Grzegorz Czerwiński ◽  
Jerzy Wołoszyn
Keyword(s):  
Mass Transfer ◽  
Phase Change ◽  
Heat Dissipation ◽  
Cooling System ◽  
Numerical Study ◽  
Relaxation Parameter ◽  
Phase Changes ◽  
Transfer Time ◽  
Two Phase ◽  
Time Relaxation

With the increasing trend toward the miniaturization of electronic devices, the issue of heat dissipation becomes essential. The use of phase changes in a two-phase closed thermosyphon (TPCT) enables a significant reduction in the heat generated even at high temperatures. In this paper, we propose a modification of the evaporation–condensation model implemented in ANSYS Fluent. The modification was to manipulate the value of the mass transfer time relaxation parameter for evaporation and condensation. The developed model in the form of a UDF script allowed the introduction of additional source equations, and the obtained solution is compared with the results available in the literature. The variable value of the mass transfer time relaxation parameter during condensation rc depending on the density of the liquid and vapour phase was taken into account in the calculations. However, compared to previous numerical studies, more accurate modelling of the phase change phenomenon of the medium in the thermosyphon was possible by adopting a mass transfer time relaxation parameter during evaporation re = 1. The assumption of ten-fold higher values resulted in overestimated temperature values in all sections of the thermosyphon. Hence, the coefficient re should be selected individually depending on the case under study. A too large value may cause difficulties in obtaining the convergence of solutions, which, in the case of numerical grids with many elements (especially three-dimensional), significantly increases the computation time.

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