Analysis of a Convection Loop for GFR Post-LOCA Decay Heat Removal

2004 ◽  
Author(s):  
Wesley C. Williams ◽  
Pavel Hejzlar ◽  
Pradip Saha
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Flow Regime ◽  
Natural Circulation ◽  
Heat Removal ◽  
Computer Code ◽  
Steady State Analysis ◽  
Decay Heat ◽  
Cooling Loops ◽  
State Analysis

A computer code (LOCA-COLA) has been developed at MIT for steady state analysis of convective heat transfer loops. In this work, it is used to investigate an external convection loop for decay heat removal of a post-LOCA GFR. The major finding is that natural circulation cooling of the GFR is feasible under certain circumstances. Both helium and CO2 cooled system components are found to operate in the mixed convection regime, the effects of which are noticeable as heat transfer enhancement or degradation. It is found that CO2 outperforms helium under identical natural circulation conditions. Decay heat removal is found to have a quadratic dependence on pressure in the laminar flow regime and linear dependence in the turbulent flow regime. Other parametric studies have been performed as well. In conclusion, convection cooling loops are a credible means for GFR decay heat removal and LOCA-COLA is an effective tool for steady state analysis of cooling loops.

Jet Engine Gas Path Analysis Based on Takeoff Performance Snapshots

2017 ◽  
Vol 139 (11) ◽  
Author(s):  
A. Putz ◽  
S. Staudacher ◽  
C. Koch ◽  
T. Brandes
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Performance Model ◽  
Operating Conditions ◽  
Medium Size ◽  
Jet Engines ◽  
Transient Effects ◽  
Steady State Analysis ◽  
Simulation Results ◽  
State Analysis

Current engine condition monitoring (ECM) systems for jet engines include the analysis of on-wing gas path data using steady-state performance models. Such data, which are also referred to as performance snapshots, usually are taken during cruise flight and during takeoff. Using steady-state analysis, it is assumed that these snapshots have been taken under stabilized operating conditions. However, this assumption is reasonable only for cruise snapshots. During takeoff, jet engines operate in highly transient conditions with significant heat transfer occurring between the fluid and the engine structure. Hence, steady-state analysis of takeoff snapshots is subject to high uncertainty. Because of this, takeoff snapshots are not used for performance analysis in current ECM systems. We quantify the analysis uncertainty by transient simulation of a generic takeoff maneuver using a performance model of a medium size two-shaft turbofan engine with high bypass ratio. Taking into account the influence of the preceding operating regimes on the transient heat transfer effects, this takeoff maneuver is extended backward in time to cover the aircraft turnaround as well as the end of the last flight mission. We present a hybrid approach for thermal calculation of both the fired engine and the shutdown engine. The simulation results show that takeoff derate, ambient temperature, taxi-out (XO) duration and the duration of the preceding aircraft turnaround have a major influence on the transient effects occurring during takeoff. The analysis uncertainty caused by the transient effects is significant. Based on the simulation results, we propose a method for correction of takeoff snapshots to steady-state operating conditions. Furthermore, we show that the simultaneous analysis of cruise and corrected takeoff snapshots leads to significant improvements in observability.

scholarly journals FRAP-S2: a computer code for the steady state analysis of oxide fuel rods

1977 ◽  
Author(s):  
J. A. Dearien ◽  
M. P. Bohn ◽  
G. A. Berna ◽  
D. R. Coleman ◽  
E. T. Laats
Keyword(s):  
Steady State ◽  
Computer Code ◽  
Oxide Fuel ◽  
Fuel Rods ◽  
Steady State Analysis ◽  
State Analysis

Studies of the Deteriorated Turbulent Heat Transfer Regime for the Gas-Cooled Fast Reactor Decay Heat Removal System

2006 ◽  
Author(s):  
Jeong Ik Lee ◽  
Pavel Hejzlar ◽  
Mujid S. Kazimi ◽  
Pradip Saha
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Fast Reactor ◽  
Natural Circulation ◽  
High Surface ◽  
Heat Removal ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Convection Regime ◽  
Decay Heat

Increased reliance on passive emergency cooling using natural circulation of gas at elevated pressure is one of the major goals for the Gas-cooled Fast Reactor (GFR). Since GFR cores have high power density and low thermal inertia, the decay heat removal (DHR) in depressurization accidents is a key challenge. Furthermore, due to its high surface heat flux and low velocities under natural circulation in any post-LOCA scenario, three effects impair the capability of turbulent gas flow to remove heat from the GFR core, namely: (1) Acceleration effect (2) Buoyancy effect (3) Properties variation. This paper reviews previous work on heat transfer mechanisms and flow characteristics of the Deteriorated Turbulent Heat Transfer (DTHT) regime. It is shown that the GFR’s DHR system has a potential for operating in the DTHT regime by performing a simple analysis. A description of the MIT/INL experimental facility designed and built to investigate the DTHT regime is provided together with the first test results. The first runs were performed in the forced convection regime to verify facility operation against well-established forced convection correlations. The results of the three runs at Reynolds numbers 6700, 8000 and 12800 showed good agreement with the Gnielinsky correlation [4], which is considered the best available heat transfer correlation in the forced convection regime and is valid for a large range of Reynolds and Prandtl numbers. However, even in the forced convection regime, the effect of heat transfer properties variation of the fluid was found to be still significant.

Plant Dynamics Evaluation of a Monju Ex-Vessel Fuel Storage System During a Station Blackout

2012 ◽  
Author(s):  
Takero Mori ◽  
Masutake Sotsu ◽  
Kei Honda ◽  
Satoshi Suzuki ◽  
Hiroaki Ohira
Keyword(s):  
Structural Integrity ◽  
Cooling System ◽  
Natural Circulation ◽  
Heat Removal ◽  
Spent Fuel ◽  
Decay Heat ◽  
Plant Dynamics ◽  
Fuel Storage ◽  
Cooling Coils ◽  
Cooling Loops

The prototype fast breeder reactor “Monju” has an ex-vessel fuel storage system (EVSS) which consists mainly of an ex-vessel fuel storage tank (EVST) and an EVST sodium cooling system. EVST uses natural circulation of sodium for decay heat removal. Natural circulation in the EVST is generated by the decay heat from the spent fuel assemblies and the cooling of the cooling coils installed in the EVST. The EVST sodium cooling system consists of three independent loops. In each loop, sodium is circulated by electromagnetic pumps and the heat is removed by an air cooler with blowers. This system has the ability to remove the maximum decay heat using two loops, and thus, it uses two of the three loops for normal operation. During a station blackout (SBO), the pumps and blowers are stopped. However, the three air coolers are installed about 13.5 m higher than the cooling coils, and therefore, the EVST sodium cooling system potentially retains some cooling ability because of natural circulation. In this study, an analysis and evaluation of the plant dynamics for the spent fuel and the EVSS structural integrity during an SBO were performed. The ultimate heat sink for the EVST sodium cooling system is the atmosphere, and the air coolers have an exhaust stack for efficient natural circulation caused by the chimney effect. However, the EVST sodium cooling system loses pressure and the heat transfer characteristics change if the flow rate is low. It was, therefore, necessary to confirm the temperature and flow rate behavior of EVSS in this analysis. In the present calculations, the plant dynamics analysis program “Super-COPD” was used. The factors affecting the cooling ability were investigated and analytical cases were determined. In one case, the two operated loops were switched to natural circulation after an SBO. The number of cooling loops was then changed from two to three by having an operator open the vane and dampers of the standby loop. In this case, sodium temperature in the EVST increased to approximately 320°C. When the number of cooling loops was not changed and natural circulation occurred in only two loops, the sodium temperature in the EVST increased to approximately 450°C. In both cases, however, the structural integrity of the EVSS was maintained. These analytical results, therefore, help clarify the number of necessary cooling loops for efficient decay heat removal and sodium temperature behavior in an SBO.

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