Page 255 - Handbook of Energy Engineering Calculations

absorbs heat from the NaK coolant, leaving the evaporator at 607°F
(319.4°C).
Draw a line vertically downward from point 3 until the liquid enthalpy
curve is intersected, point 4. Point 4 represents the boiler feedwater inlet
temperature, or 442°F (227.8°C), based on the valid assumption that the

feedwater leaving the condenser hot well is in the saturated state.

5. Compute the reactor coolant flow rate
Sodium enters the reactor at 600°F (315.6°C) and leaves at 1000°F
(537.8°C), Fig. 1. Thus, the temperature rise of the Na during passage

through the reactor is 1000 − 600 = 400°F (222.2°C). Also, the average
specific heat of Na is 0.306 Btu/(lb · °F) [1.28 kJ/(kg · °C)], found from a
tabulation of Na properties in an engineering handbook.
Compute the Na flow from f = 3413 kw/Δtc, where f = Na flow rate, lb/h;

kw = reactor heat rating, kW; Δt = Na temperature rise during passage
through the reactor, °F; c = specific heat of the Na coolant, Btu/(lb · °F).
Substituting gives us f = 3413(400,000)/[400(0.306)] = 11,130,000 lb/h
(1402.4 kg/s).

6. Compute the boiler heating liquid flow rate
Use the same relation as in step 5, substituting the temperature change and
specific heat of NaK. Since the NaK enters the boiler at 950°F (510.0°C) and
leaves at 550°F (287.8°C), its temperature change is 950 − 550 = 400°F
(222.2°C). Also, the specific heat of NaK is 0.251 Btu/(lb · °F) [1.05 kJ/(kg ·

°C)], as found from NaK properties tabulated in an engineering handbook. So
f = 3413(400,000)/[400(0.251)] = 13,600,000 lb/h (1713.6 kg/s).

7. Compute the plant thermal efficiency
The net station output kw = gross output of turbine, kW, minus the total plant

auxiliary demand, kW = 155,000 − 12,000 = 143,000 kW. Then overall plant
thermal efficiency = net station output, kW/reactor heat output, kW =
143,000/400,000 = 0.357, or 35.7 percent.

Related Calculations. This analysis is valid for a cycle in which the reactor
coolant does not do work in the turbine. In general, designers prefer to avoid

using the reactor coolant in the turbine. Although the thermodynamic aspects