Numerical Study of Natural Circulation Flow in Reactor Coolant System during a Severe Accident

Table 3

Comparison of the main evaluation factors for each model.

Contents			Symbol or eq.	Experiment	Model 1; Original tube; 1 : 1	Model 2; Tube simplification; 6 : 1	Model 3; Tube simplification; 12 : 1
End of hot leg	Mass flow rate at the end of hot leg (kg/s)		m	0.061; (0.00%)	0.0610; (1.84%)	0.0635; (6.01%)	0.0668; (11.49%)
	Average temperature (°C)	Hot flow	Th	153.1; (0.00%)	153.1; (−3.89%)	154.3; (−3.14%)	151.0; (−5.24%)
		Cold flow	Tc	86.8; (0.00%)	80.4; (−7.37%)	87.2; (0.46%)	89.0; (2.52%)
Tube bundle	Number of hot tubes		—	75.0; (0.00%)	70.0; (−6.67%)	78.0; (4.00%)	84.0; (12%)
	Number of cold tubes		—	146; (0.00%)	146; (3.55%)	138; (−2.13%)	132; (−6.38%)
	Mass flow rate at tubes (kg/s)		mt	0.120; (0.00%)	0.120; (0%)	0.126; (4.93%)	0.129; (7.22%)
	Heat transfer rate (W)		—	3,560; (0.00%)	3591; (0.87%)	3,603; (1.2%)	3,473; (−2.44%)
	Average temperature (°C)	Hot tube	Tht	100.8; (0.00%)	101.2; (0.4%)	99.5; (−1.3%)	97.5; (−3.23%)
		Cold tube	Tct	64.7; (0.00%)	64.7; (0%)	64.7; (0%)	64.7; (0.05%)
Ratio of mass flow rate			mt/m	2.00; (0.00%)	1.97; (−1.5%)	1.98; (−0.85%)	1.93; (−3.67%)
Mixed temperature (°C)			Tm	96.2; (0.00%)	94.5; (−1.77%)	94.7; (−1.52%)	94.2; (−2.08%)
Mixing fraction			f	0.85; (0.00%)	0.77; (−9.41%)	0.84; (−0.97%)	0.89; (4.28%)