Thanks a lot to all Masters for guiding me!

I went through URL's given by you all and used below query to find out how much disk space tempDB has and how much free:

SELECT SUM(unallocated_extent_page_count) AS [free pages],

(SUM(unallocated_extent_page_count)*1.0/128) AS [free space in MB]

FROM sys.dm_db_file_space_usage;

And I came to know currently TempDB has 150966 MB and out of it TempDB has about 150199MB free space!!! that means TempDB currently using only around 46MB!!!!!!!

Now my concern is "How to release this free space from TempDB?" I tried to shrink file but it showing just 8MB assigned to tempdb.mdf file and .50MB to tempdb.ldf. I am confused. Please help me to release this free TempDB disk space.