Combined Heat and Power and Combined Cycles Tutorial Solutions

1)Exhaust gas outlet temperature may be governed by the minimum allowable temperature difference in the heat exchanger or by the Acid Dew Point. In this case the Acid Dew Point is 110oC. The minimum outlet temperature governed by the minimum temperature difference may be calculated:

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2)Exhaust gas outlet temperature may be governed by the minimum allowable temperature difference in the heat exchanger or by the Acid Dew Point. In this case the Acid Dew Point is 110oC. The minimum outlet temperature governed by the minimum temperature difference may be calculated:

148>110 therefore the outlet temperature must be 148oC to meet both criteria.

3) The procedure for solving this question is: i) Analyse gas turbine cycle to obtain gas exhaust temperature, power output and rate of heat input to plant. ii) Analyse steam cycle to determine work output/kg of steam iii) Analyse heat exchanger between cycles to determine steam flow rate and hence Steam cycle power output. (note subscripts identifying points are not unique, but are recycled in each piece of analysis) Gas Turbine

Steam Cycle

Heat Exchanger

(Note these differ slightly from numbers printed on question sheet)