How to distinguish 영 & 공?
공 is used to speak the number phone, for ex 0905-...:(공구공오).
영 is used to speak the degree Celsius, for ex 영 도

Is there any case?

Question

How to distinguish 영 & 공? 
공 is used to speak the number phone, for ex 0905-...:(공구공오).
영  is used to speak the degree Celsius, for ex 영 도

Is there any case?

Answer

"영" is also used for...
1. arithmetic.
e.g.
0*1 = 0 (영 곱하기 일은 영, zero multiplied by one is zero)

2. hours in the 24-system.
00:35(영[시] 삼십오[분] or 공공[시] 삼십오[분], 12:35 am)
03:35(공삼[시] 삼십오[분], not 영삼[시] 삼십오[분]. 3:35 am)

3. numbers with a decimal point
0.35 (영[점] 삼오, 점 ☞ dot )
0.0001 (영[점] 영영영일)

\^o^/