Hello Rohan
I think that the hot side is modelled as fluid flowing from a reservoir, through the exchanger and then ending in a second reservoir. This is correct.
On the cold side, you have accidentally fluid circulating in a steady state at a temperature determined by Simscape (looks like 293.15k often default temperature in the exchanger).This fluid cools down the hot one until equilibrium is reached.
Try setting two reservoirs in the cold side and adjust the temperature accordingly.
BR Juan
