what will be the exhaust pressure of gt? in our m/c, in simple cycle gt exhaust pressure is coming around 45mmwc at baseload but in combined cycle why the same thing increasing up to 250mmwc........

 

The exhaust back pressure is higher in combined cycle due to the heat recovery equipment in the exhaust path. Treat the heat recovery equipment as an orifice. In simple cycle operation you are bypassing the orifice.