Turbines, steam regenerative cycle

The thermal efficiency of the Rankine cycle can be increased by the use of regenerative heat exchange as shown in Fig. 2.15. In the regenerative cycle, a portion of the partially expanded steam is drawn off between the high-and low-pressure turbines. The steam is used to preheat the condensed... 

A four-stage turbine with reheat and three-stage regenerative steam Rankine cycle as shown in Fig. 2.36a was designed by a junior engineer. The following design information is provided ... 

A steam power plant operating on a regenerative cycle, as illustrated in Fig. 8.5, include feedwater heaters. Steam enters the turbine at 6,000 kPa and 500°C and exhausts at 10 kPa. St for the feedwater heaters is extracted from the turbine at pressures such that the feedwater is he to 180°C in two equal increments of temperature rise, with 5-°C approaches to the steam-condensa temperature in each feedwater heater. If the turbine and pump efficiencies are both 80 percent, is the thermal efficiency of the cycle and what fraction of the steam entering the turbine is extra for each feedwater heater ... 

Example 4.17 Ideal reheat regenerative cycle A steam power plant is using an ideal reheat regenerative Rankine cycle (see Figure 4.23). Steam enters the high-pressure turbine at 9000 kPa and 773.15 K and leaves at 850 kPa. The condenser operates at 10 kPa. Part of the steam is extracted from the turbine at 850 kPa to heat the water in an open heater, where the steam and liquid water from the condenser mix and direct contact heat transfer takes place. The rest of the steam is reheated to 723.15 K, and expanded in the low-pressure turbine section to the condenser pressure. The water is a saturated liquid after passing through the water heater and is at the heater pressure. The work output of the turbine is 75 MW. Determine the work loss at each unit. 

Regeneration In a regenerative cycle, steam extracted at intermediate pressures from various parts of the turbine is used in countercurrent heat exchangers (closed heaters) to heat the feed. Regeneration may increase the efficiency, help to deairate the water, and control the discharged steam flow rate. 

A steam power plant operates on a regenerative cycle. Steam enters the turbine at 700 psia and 800 °F and expands to 1 psia in the condenser. Part of the steam is extracted at 60 psia. The efficiencies of the turbine and pump are 0.80 and 0.95, respectively. The work output of the turbine is 4000 Btu/s. 

In electric utihty service, thousands of gas turbines around the world have been apphed to serve peak loads (up to 1500 h/yr) in the simple-cycle mode. Because of limited operation, fuel consumption is not as significant a factor as are capital costs, operating labor, and maintenance. Most gas turbines that are applied in midrange or base-load electric utility service combine steam and gas turbine cycles, but a small number also have used regenerative cycles. 

In Fig. 6.67 a regenerative-cycle gas turbine is followed by a low-pressure process steam generator. One of the consequences of the low fuel consumption of the regenerative-cycle gas turbine is a reduction of the regenerator exhaust gas temperature to approximately 600°F (316°C).This arrangement should be selected when only a relatively small amount of process steam is required. 

Simple Cycle Regenerative Steam Turbine Combined Cycle Advanced Gas Hybrid Power Plant... 

Determine the efficiency and power output of a regenerative Rankine cycle using steam as the working fluid and a condenser pressure of 80 kPa. The boiler pressure is 3 MPa. The steam leaves the boiler at 400° C. The mass rate of steam flow is 1 kg/sec. The pump efficiency is 85% and the turbine efficiency is 88%. After expansion in the high-pressure turbine to 400 kPa, some of the steam is extracted from the turbine exit for the purpose of heating the feed-water in an open feed-water heater, the rest of the steam is reheated to 400°C and then expanded in the low-pressure turbine to the condenser. The water leaves the open feed-water heater at 400 kPa as saturated liquid. Determine the steam fraction extracted from the turbine exit, cycle efficiency, and net power output of the cycle. 

In this ideal regenerative Rankine cycle, the steam extracted from the turbine heats the water from the condenser, and the water is pumped to the boiler. Sometimes, this occurs in several stages. The condensate from the feed water heaters is throttled to the next heater at lower pressure. The condensate of the final heater is flashed into the condenser... 

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