nly - You can't save changes to this file. 4. We are trying to design a Heat recovery steam generator (HRSG) heat exchanger. This is to recover heat from the exhaust of a gas turbine and use it to create steam in a Rankine cycle. The exhaust gases from the gas turbine are at a temperature of 620°C and the mass flow rate is mair =190kg/s. The liquid water enters the HRSG at a temperature of 50°C. As the water flows through the economizer it gets heated and then enters the evaporator. The gas temperature at this point (T3) is 200°C as shown in Figure 1. You may assume that both pinch points are approximately 20°C. Save a Temperature T₁ = 620°C T mair-190 kg/s Gas Flow =600°C T₂ Tw4 T,-200°C 180°C T₁ Tw Twi Super- Water/Steam Flow heater Evaporator Econo-T- = 50°C mizer Length Figure 1: Flow through a HRSG heat exchanger (a) of the three heat exchangers inside the HRSG, the economizer, evaporator and superheater, which one do you think is the most expensive and why? (b) What is the pressure of the water? (c) What was the mass flow rate of the water/steam (mwater)? (d) What is the exit temperature of the gas, T₁? (e) Make an estimate of the maximum power output of the turbine used in the Rankine cycle if the turbine exit pressure is 10kPa.