openERP 7 need to export data in UTF-8 CSV , but how?
Encodings are a complicated thing, and it is difficult to answer an encoding-related question without precise facts. ANSI is not an encoding, I assume you actually mean ASCII. And ASCII itself can be seen as a subset of UTF-8, so technically ASCII is valid UTF-8.
OpenERP 7.0 only exports CSV files in UTF-8, so if you do not get the expected result you are probably facing a different kind of issue, for example:

The original data was imported using a wrong encoding (you can choose the encoding when you import, but again the default is UTF-8), so it is actually corrupted in the database, and OpenERP cannot do anything about it
The CSV file might be exported correctly in UTF-8 but you are opening it with a different encoding (for example on Windows most programs will assume your files are ISO-8859-1/Latin-1/Windows-1252 encoded). Double-check the settings of your program.

If you need more help you'll have to be much more specific: what result do you get (what does the data look like), what did you expect, etc.
I can export a CSV with openERP 7 , but it is encoded in ANSI. I would like to have it as a UTF-8 encoded file. How can I achieve this ? The default export option in openERP doesn"t have any extra options. What files should be modified ? Or is there an app for this matter ? Any help would be appreciated.