Ab	total area of the heat sink base (m2)
Abg	area of background base (excluding hotspot area) (m2)
Ahs	area of single hotspot (m2)
Ac	microchannel cross-sectional area (m2)
BL	bottom layer
CF	counter flow
Cp	specific heat (J/kg·K)
Dh	hydraulic diameter of the channel (m)
hconv	convective heat transfer coefficient (W/m2·K)
Hc	microchannel height (m)
HS1, HS2, HS3	three random hotspot layout schemes
k	thermal conductivity (W/m·K)
LB	lower bound
Ls	length of hotspot (m)
Lx, Ly, Lz	length, total height, and total width of the heat sink, respectively (m)
$m_{\mathrm{tot}}$	total mass flow rate (kg/s)
$n_{\mathrm{ch}}$	total numbers of channels
Δpch	pressure drop in one channel (Pa)
Ptot	total pumping power required for a heat sink (W)
PF	parallel flow
$q_{\mathrm{hs}},q_{\mathrm{b}}$, $q_{\mathrm{bg}}$	heat fluxes applied at the hotspot, base, and background base, respectively (W/m2)
Qtot	total heat applied at the base (W)
Re	Reynolds number
Rth,tot	total thermal resistance (K/W)
T	temperature (K)
TL	top layer
TF	transverse flow
uavg	average fluid velocity (m/s2)
UB	upper bound
$\overline{V}$	velocity vector
Wb1	thickness of base at the bottom (m)
Wb2	thickness of base between the bottom and top layer (m)
Wc	microchannel width (m)
Wcp	thickness of the cover plate (m)
Ws	width of a hotspot (m)
Ww	width of microchannel walls (m)
X, Y, Z	orthogonal coordinate system