Overall Thermodynamic Balance

FIRST LAW OF THERMODYNAMICS Thermodynamics Example 5: Overall Thermodynamic Balance A nuclear facility (primary side) is to be studied as a complete system. The heat produced by the heat source is 1.36 x 10¹⁰ Btu/hr. The heat removed by the heat exchanger (steam generator) is 1.361 x 10¹⁰ Btu/hr. What is the required pump power to maintain a stable temperature? Solution: = pump work, = heat produced by the heat source, heat transferred W_p Q_c Q into steam generator m(h pe ke) W_p Q_c Q_sg m(h pe ke) 1) For a closed system, the mass entering and leaving the system is zero, therefore, is constant. The energy entering and leaving the system is zero, and you can m assume that the ke and pe are constant so that: _c+ _p= sg Q W Q 2) = W_p Q_sg Q_c = 1.361 x 10¹⁰ Btu/hr - 1.36 x 10¹⁰ Btu/hr = 1.0 x 10⁷ Btu/hr = 4007 hp W_p Of the examples just completed, emphasis should be placed on the heat exchanger analysis. Both the primary side and the secondary side have their own energy balances as the heat energy is transferred from one fluid to the other. In calculating heat exchanger heat transfer rates, we found that we could use the equations . Q mc_pDh Perhaps a short analysis of the secondary side of the heat exchanger will aid in understanding the heat exchanger’s importance in the energy conversion process. HT-01 Page 66 Rev. 0