Is there any way that I run 2 cfx solver analysis at a time in a single machine ?

It depends on you machine (actually the memory capacity of it): what is your number or processors and their capacity?

hp linux work station(xw series machine). it has 2 dual core processors. for my problem it uses only 50% of the RAM. i want to utlize the remaining.

So you just have to set 'local parallel run' and in CFX solver and set it to 2 (your number of processor). If it still doesnt run, read the manual, or check other topics of this forum.