You need 15"-20" (over a foot) between a freezer/fridge & a radiator. The appliance would have to work much harder, it'd be marked dthr electrical wires would possibly melt. It's a big No No! Sorry - but there are rules in a kitchen for a reason - mainly fire hazards.
Fridges & freezers aren't to be put near any heat, ie. cookers & not in direct sunlight either. Ok?