Thermodynamics FIRST LAW OF THERMODYNAMICSA thermodynamic balance across the reactor core gives an indication of the amount ofheat removed by the coolant that is given off by the fuel rods.Example 4: Thermodynamic Balance across Heat SourceIn a particular facility, the temperature leaving the reactor core is 612°F, while thatentering the core is 542°F. The coolant flow through the heat source is 1.32 x 108lbm/hr. The cp of the fluid averages 1.47 Btu/lbm°F. How much heat is being removedfrom the heat source? The pe and ke energies are small compared to other terms andmay be neglected.Solution:m(hpeke)inQm(hpeke)outWQm(houthin)1) Substituting where cp = specific heat capacity.QmcpDT=Qm(cp) (ToutTin)= 1.32 x 108 lbm/hr (1.47 Btu/lbm -oF) (612 - 542oF)Q= 1.36 x 1010 Btu/hrQFor this example has been used to calculate the heat transfer rate since noQmcpDTphase change has occurred. However, (hout-hin) could also have been used hadQmthe problem data included inlet and outlet enthalpies.The individual principal components of a reactor system have been thermodynamicallyanalyzed. If all components were combined into an overall system, the system could beanalyzed as a "closed" system problem. Such an analysis is illustrated in the followingexample.Rev. 0 Page 65 HT-01
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