Steam Condensation Heat Transfer in the Presence of Noncondensable Gases (NCGs) in Nuclear Power Plants (NPPs): A Comprehensive Review of Fundamentals, Current Status, and Prospects for Future Research

Table 4

Physical properties and dimensionless ratios of hydrogen (H₂) and helium (He) at a pressure of 1 atm and a temperature of 20°C.

Parameter	H2	He
Kinematic viscosity () (m^2/s)
Diffusion coefficient () (m^2/s)
Sonic speed () (m/s)
Density () (kg/m^3)
	0.91
	1.17
	1.3
	0.46
	2.0