Abstarct: Nanofluid is a suspension of nanoparticles (10-100 nm) in a conventional basic fluid such as water, oil and ethylene glycol and enhances the heat transfer. In this paper, cu-water nanofluid flow in a horizontal channel with infinite depth was investigated. Equal, non-equal constant flux and constant temperature as boundary conditions on the channel walls were considered. The governing equations, continuity, momentum and energy for laminar flow in non-dimensional form are being discretized using finite volume approach using power-low profile approximation. Well-Known SIMPLER algorithm by “Patankar” is employed to solving the equations in implicit scheme using iterative method. Thermal conductivity of Nanofluid is a function of temperature. Results are presented for wide range of Reynolds numbers, 20<Re<1500, and different volume fractions of nanoparticles, 0<∅<0.05. It has been observed that increasing the volume fraction of nanoparticles causes to increase the heat transfer rate. Heating by electrical resistant, radiation and nuclear activities in nuclear reactors are important applications of constant heat flux boundary conditions. Also kinds of heat exchangers like evaporators and condensers are examples of constant temperature boundary conditions.