Helical channels are widely applied in different application areas. In a converging diverging nozzle, helical channels are mainly used for cooling of its wall. The characteristics of fluid flow and heat transfer inside helical duct for a converging diverging nozzle is not commonly dealt in present literatures. In this paper CFD simulations are carried out for a helical rectangular duct of a converging diverging nozzle. In the present study the nozzle is oriented horizontally as a counter flow heat exchanger and analysis is done on ten helical ducts by changing the flow rates of four different fluids like water, ethanol, kerosene and Nano fluid. The fluid flow and heat transfer characteristics for the above fluids are studied along with the correlations for the prediction of Nusselt number for each fluid.