Tempdb MDF file is increasing and not I am not able to shrink it.

Output of below query is

  SELECT session_id,
       SUM(internal_objects_alloc_page_count) AS task_internal_objects_alloc_page_count,
       SUM(internal_objects_dealloc_page_count) AS task_internal_objects_dealloc_page_count
     FROM sys.dm_db_task_space_usage  where internal_objects_alloc_page_count >10 and session_id> 50
     GROUP BY session_id; 

SELECT SUM(internal_object_reserved_page_count) AS [internal object pages used],
 (SUM(internal_object_reserved_page_count)*1.0/128) AS [internal object space in MB]
 FROM sys.dm_db_file_space_usage;

internal object pages used  internal object space in MB

3552     27.750000

----------------------------------

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;

 3559272    27806.812500

Database MDF is 27806 MB and I tried to shrink but unable to shrink. It is production server.I do not want Restart sql server.

There is no open transaction.

Any one suggestion