Numerical method was used to study the heat transfer of heat collector of a domestic heating power cooling integrated utilization system (DHPCIUS).The unsteady forced convection of two heated horizontal cylinders confined in a 2-D squared enclosure was studied and abstracted to a model by using the DHPCIUS.The simulations were carried out under different Reynolds number Re and cylinders spacing s.The results show that when the Re is smaller,the fluid flow and heat transfer finally tend to a stable and symmetrical state.When the Re increases to a certain value,the fluid flow and heat transfer change over time,being in an asymmetric state.The flow fluid and the heat transfer on the cylinders surfaces are enhanced when the Re increases.The calculations got a stable solution,a periodic oscillation and a direct entering into chaos along with the increase of Re.The cylinder spacing s has a little influence on the flow and heat transfer when Re≤150,while has a great influence on the flow and heat transfer when 200≤Re<300.But when Re≥300,the cylinder spacing affects less on heat-exchange.