A combined plant with heat loss between two cyclic plants in series

A combined plant with heat loss between two cyclic plants in series 

Consider next two cyclic plants operating in series, but with unused heat Qun (or heat loss ) between the two plants, so that Qhr = 3l + Gun- shown in Fig. 7.2. 

The overall thermal elficiency of the combined plant is by definition 

However, the heat supplied to the lower cycle is now Gl = Ghr Gun = Gb( Vh) Gun-so that 

The most developed and commonly used combined power plant involves a combination of open circuit gas turbine and a closed cycle (steam turbine), the so-called CCGT. Many different combinations of gas turbine and steam turbine plant have been proposed. Seippel and Bereuter [3] provided a wide-ranging review of possible propo.sed plants, but essentially there are two main types of CCGT. 

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