'hier' isn't a noun. It's an adverb like 'yesterday'. 'C'est beau hier.' is incorrect but you can say 'C'était beau, hier.'
As explained by the others, here are some examples :
Un beau camion (M) (consonant)
Un bel avion (M) (vowel)
Un bel homme (M) (silent H so like a vowel) -> l'homme
un beau homard (M) (aspirate h so like a consonant) -> le hommard
Une belle voiture (F)
Aspirate h aren't really pronounced by French speakers nowadays but are important to determinate the spelling of the masculine definite article (le, l') or the masculine adjective (beau, bel;vieux, vieil) and the pronouncing of liaisons. In French dictionary, words with an aspirate h are indicated by a * before the h. This is sometimes confusing for French speakers too. If you have a doubt, use the silent h even if it's a mistake, your mistake will be less noticeable. So a common mistake of French speakers is to say the liaison in 'les haricots' where the sound Z shouldn't be pronounced.