ρ s	Density (Kg/m3)
k s	Thermal conductivity (J/m·K)
E	Modulus of elasticity (GPa)
σs	Yield strength (Mpa)
ν	Poisson’s ratio
t	heat pipe flattening thickness
dp	copper powder particle size
h	maximum thickness of the absorbent wick
∆Pc,max	maximum capillary pressure of the wick
σ	surface tension of the working liquid
θ	contact angle of the working liquid
reff	effective capillary radius of the wick
Rer	radial Reynolds number
mv	mass flow rate of the steam
μv	viscosity of the steam
∆Pl	working liquid flow pressure drop in the wick from the condenser to the evaporator section
∆Pv	total vapor flow pressure drop in the ultra-thin heat pipe
∆Pevp	interface pressure drops due to vapor
∆Pcon	interface pressure drops due to condensation
∆Pg	gravitational pressure drop
Q′max	capillary limit of the ultra-thin heat pipe
ρv	vapor density
rv	radius of the vapor space
Av	vapor passage area
hlv	latent heat of the liquid
Leff	effective length of the ultra-thin heat pipe
Dh	hydraulic diameter of the ultra-thin heat pipe
∆Pw	flow pressure drop in the evaporator
μl ,w	magnetic permeability
∆Pbuoy,v	buoyancy force exerted on the water vapor by the temperature difference between the evaporating and condensing sections under gravity
∆Pentrainment	additional pressure drop caused by the shear stress generated by the liquid-vapor counterflow at the interface of the two phases
$\xi$	ratio of wetted to non-wetted surfaces at the boundary of the wick
L	heat transfer length
k	thermal conductivity
A	heat transfer area
Rvapor	thermal resistance of evaporator section
R liquidbridge	additional thermal resistance when liquid bridges occur in the evaporator
R 1	radial heat conduction and thermal resistance of pipe wall of evaporation section
R 2	radial heat conduction and thermal resistance of the wick in the evaporation section
R 3	phase change heat transfer thermal resistance at the vapor-liquid interface in the evaporation section
R 4	thermal resistance caused by steam axial flow heat transfer
Lbridge	length of the liquid bridge
kwall	thermal conductivity of the heat pipe wall
d0	outer diameter of the heat pipe
di	inner diameter of the heat pipe
λw	thermal conductivity of the pipe wall
L 1	length of the evaporation section
dv	diameter of the vapor space inside the pipe
λe	thermal conductivity of the wick compound
R	vapor gas constant
Tv	vapor temperature
r	latent heat of vaporization
p	vapor pressure
Leq	effective length of the heat pipe
Ti	central temperature of the thermal resist block
λi	thermal conductivity thickness of the thermal resist block