Dunno, but the best way to reheat tempura is in an oven. Put the tempura on a non-stick baking tray (or use baking parchment); preheat the oven to 450°F (505°K); bake the tempura for 3 minutes; flip it; bake it for another 3 minutes; drain the tempura on paper towel.
@Oeconomist
I have literally never seen anybody use Kelvin when talking about normal (non-scientifically driven) cooking-related stuff.
Heck, I don't think anything in my kitchen even includes °K, despite it being the SI unit of temperature.
@Echonic
You MOCK me? A wager made with food on the line is clearly NEVER trivial!