D	relative uncertainty
Dt	temperature nonuniformity, °C
Gr	Grashof number
H	height, m
h*	convective heat transfer coefficient, W·m−2·K−1
h fg	latent heat, J·kg−1
l	length, m
N	merit factor
Nu	Nusselt number
Pr	Prandtl number
Q	input heat, W
Q’	heat transfer amount, W
R	thermal resistance, K·W−1
S	uncertainty
S	thickness, m
T	temperature, °C
$\overline{\mathit{T}}$	average temperature, °C
V	volume, m3
W	width, m
Greek symbols
α	half V-type angle value, °
α*	volume expansion coefficient, K−1
η	filling ratio of working fluid
λ	thermal conductivity coefficient, W·m−1·K−1
μ	dynamic viscosity coefficient, N·s·m−2
ρ	density, kg·m−3
σ	surface tension, N·m−1
Subscripts
adia	adiabatic
ave	average
b	boss
con	condensation
eva	evaporation
f	fluid
g	groove
I	current
I	order of number
L	liquid
Max	maximum
Q	input heat
Qloss	heat loss
R	thermal resistance
T	temperature
U	voltage
V	vapor
W	wall