Question

What is the thermal efficiency of this reheat cycle in terms of enthalpies?

Answer 1

Answer:

   $\eta =\dfrac{\left (h_3-h_4\right )+(h_5-h_6)-(h_2-h_1)}{(h_3-h_2)+(h_5-h_4)}$

Explanation:

For close gas turbine:

       Gas turbine works on Brayton cycle.Gas turbine have lots of applications like ,it is use in aircraft,in land applications etc.

Reheating is the method to improve the efficiency of the gas turbine.In reheating gas is expanding in two turbine instead of one turbine alone.Two turbine like high pressure turbine and low pressure turbine are used for expansion.

In the above diagram 1-2 is a compressor,2-3 heat addition,3-4 high pressure turbine,4-5 reheating of cycle 5-6 low pressure turbine,6-1 heat rejection,

We know that    $\eta =\frac{W_{net}}{Q_{s}}$

Now take $h_{1},h_{2},,h_{3},h_{4},h_{5},h_{6}$ represent the enthalpy of point 1,2,3,4,5,6 in the cycle respectively.

So total heat supplied $Q_S$=

$\left (h_3-h_2\right )+\left (h_5-h_4\right )$

Net work out put

$W_{net}$=$\left (h_5-h_6\right )-\left (h_2-h_1\right )$

So efficiency   $\eta =\frac{W_{net}}{Q_{s}}$

      $\eta =\dfrac{\left (h_3-h_4\right )+(h_5-h_6)-(h_2-h_1)}{(h_3-h_2)+(h_5-h_4)}$