When Delta T is 6 Degree centrigate then how much in Liter per minute
Degrees C and Liters per minute are totally different physical properties. You cannot convert one to the other.
That is even worse than comparing apples to oranges.
If you knew how fast heat was being added to a flow of water in steady state, you could calculate the temperature rise as a function of flow rate. (The would be inversely proportional). However, you provided no such information.