A turbulence inducing fan blows cold gaseous nitrogen through ducts disposed to either side of a conveyor carrying product to be frozen through a freezing tunnel. The cold gaseous nitrogen is deflected downwardly onto product on the conveyor by a baffle having, in cross section, the form of a cusp. The cold gaseous nitrogen forms two counter-rotating vortex. The cold gaseous nitrogen travels across the product and then passes into an intake cowl primarily via inlets disposed adjacent both edges of the conveyor. The intake cowl collects the cold gaseous nitrogen which is sucked into the intake of the turbulence inducing fan. This arrangement provides excellent heat transfer to the product being frozen.