NOMENCLATURE Q = heat loss rate, W Ø = volume fraction K = Thermal Conductivity, W/m∙K h = Convective heat transfer coefficient, W/m2∙K T = Temperature, K c = specific heat capacity, J/kg∙K Î = effectiveness Nu = Nusselt Number C = heat capacity, J/K∙s Pr = Prandtl Number m = mass flow rate, kg/s U = overall heat transfer coefficient, W/m2∙K r2 = inner diameter of spiral tube, m r1 = outer diameter of spiral tube, m d = average diameter of tube, m A1 = inner surface area of spiral tube, m2 A2 = outer surface area of spiral tube, m2 L = Length of the tube, m Re = Reynolds Number NTU = Numbers of Transfer Units μ = Viscosity, m2/s ρ = Density, kg/m3 Subscripts a = air w = water p = nanoparticle f = fluid i = inlet o = outlet m = mean t = spiral tube min = minimum max = maximum |