OK,
Look at it slightly different...

If you got a weight and you move it a distance, you agree that the work you carry out could be described as kg x m?

Now, the flow multiplied by the specific gravity is your weight and the temperature differential (Delta T) is your distance.

The easier way to look at your formula is:
kW = ( l/s x 4.186 ) x K
or
Work carried out = weight x distance.



.