In large steam power plants, the feedwater is often heated in closed feedwater heaters, which are basically heat exchangers, by steam extracted from the turbine at some stage. Steam enters the feedwater heater at 1.6 MPa and 250°C and leaves as saturated liquid at the same pressure. Feedwater enters the heater at 4 MPa and 30°C and leaves 10°C below the exit temperature of the steam. Neglecting any heat losses from the outer surfaces of the heater, determine the ratio of the mass flow rates of the extracted steam and the feedwater heater.

Compressor as the core part of a domestic air conditioner is using Refrigerant-134a as ns working fluid. The refrigerant enters the compressor at 140 kPa and –13°C with the required power input of 120 kW, and it is compressed to the condenser pressure and temperature of 1000 kPa and 60°C respectively. Evaluate if the adiabatic compressor is able to deliver compressed air at a minimum rate of 5 kg/s. Justify your answer with relevant calculations.

Steam at 1.6 MPa and 250°C is being throttled by an adiabatic steam valve to reduce its pressure to 0.5 MPa before it is being delivered to a heat exchanger (shown in Figure 1). At valve outlet, the steam at18,000 kg/hour flow into an adiabatic heat exchanger as hot fluid. Cooling water from water tap is used to cool the steam by circulating the water through the tubes inside the heat exchanger. At heat exchanger outlet, the cooling water temperature increased by 20°C as it passing through the heat exchanger, and steam leaves the heat exchanger as saturated vapor at 200 kPa. Determine: (a) the temperature of the steam at heat exchanger inlet; and (b) the mass flow rate of the cooling water required. (Note: Use specific heat of cooling water at constant pressure as 4.18 kJ/kg.C) Heat Exchanger Steam Steam valve Cooling Water

Air (cp = 1.005 kJ/kg·°C) is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. Air enters the heat exchanger at 95 kPa and 20°C at a rate of 0.75 m3/s. The combustion gases (cp = 1.10 kJ/kg·°C) enter at 160°C at a rate of 0.95 kg/s and leave at 95°C. Determine the rate of heat transfer to the air and its outlet temperature. The rate of heat transfer to the air is ___ kW. The outlet temperature is ___°C.