Yes, KELVINS is a Scrabble word!

Letter values in Scrabble US: K 5, E 1, L 1, V 4, I 1, N 1, S 1.

Is it a valid word?

KELVINS is a valid word in the official Scrabble dictionary (US), the UK Scrabble Dictionary and Words with Friends (ENABLE).

the basic unit of thermodynamic temperature adopted under the Systeme International d'Unites
British physicist who invented the Kelvin scale of temperature and pioneered undersea telegraphy (1824-1907)

Also: k, first baron kelvin, william thompson.