Subscripts


o Out tot Total w Hot wall

NTU number of transfer unit Nu Nusselt number p Pressure, Pa

164 Heat Exchangers– Advanced Features and Applications

K/W

K

SF,<sup>i</sup> Momentum source along the ith Cartesian direction, Pa

/s

U Overall heat transfer coefficient, W/m<sup>2</sup>

/m3

Pr = υ/α the Prandtl number Q Heat transfer rate, W q Heat flux, W/m2 R Thermal resistance, m<sup>2</sup>

Re = uL/υ Reynolds number σ Thermal stress, Pa

SE Energy source, W T Temperature, K Td Mean temperature, K u Fluid local velocity, m/s

<sup>V</sup>\_ Volume flow rate, m<sup>3</sup>

Greek symbols

β Area density, m2

δij Kronecker symbol ε Effectiveness

Δp Pressure drop, Pa ρ Density, kg/m3

∞ Free stream

Subscripts

cond Conductive conv Convective c Cold h Hot

f Cooling air i Inlet

lm Logarithmic mean

x Cartesian coordinate, m

λ Thermal conductivity, W/m K μ Dynamic viscosity, Ns/m<sup>2</sup>

ξ Performance index, W/kPa τ Viscous stresses, Pa ΔT Different temperature, K
