plate 190 vane portion 200 is bevelled having a generally frustoconical shape and defines an opening 188 at an end 189 thereof sides 202 of vane 200 are generally arcuate and taper from opening 188 to gradually merge with mounting plate 190 in operation air flow is directed to heat sink assembly 180 in direction a see fig8 c and 8d air is drawn through fins 184 and encounters vane 200 arcuate sides 202 of vane 200 direct air which has been heated by its passage through fins 184 away from heat sink assembly 180 in air flow direction c this configuration reduces the pressure drop required to pass the air through heat sink assembly 180 in order to encourage re direction of air flow across mounting plate 190 and laterally away from heat sink 182 the shape of vane 200 is not limited to the shape illustrated in fig8 a to 8 d any other shape may be used to encourage the flow of air in a desired direction in order to improve cooling of heat sink 182 and any associated electronic components for example vane portion 200 could have spiral grooves it could be cup shaped it could have generally straight sides or.