I don't think there is an accent when written - it is like slang. It is very commonly used.
"Refrigerador" is most common in modern usage. "Nevera" translates most closely to "icebox."
There is no particular reason for that. "Fridge" should be accepted in both cases.
"She has two fridges in the kitchen." was accepted for me on Sep 8, 2018. I don't think I've ever heard anyone use 'fridges' in real life, the plural I mean. Singular, all the time; plural, maybe never. Something about it doesn't sound right, but I can't say there's anything wrong with the word technically.
Are you asking about the pluralisation of the English words? It works just like with any other regular noun:
- one fridge - two fridges
- one refrigerator - two refrigerators