Problem Statement:
The ML-1 reactor (mobile low power reactor 1) was a Brayton cycle nitrogen-cooled, water-moderated reactor designed by Aerojet-General Corporation. This was part of the United States Army Nuclear Power Plant Program (USANPP) and like many reactors in this program; it had a power rating less than 2 MWe. This reactor plant was transported on standard army trailers. The purpose of the ML-1 power plant was to provide electrical power to remote locations. It was intended to provide power to run a field hospital. The ML-1 reactor was during the years of 1961-1964. By 1965, all power plants of the USANPP had been phased out. Figure 1 shows a schematic of the ML-1 plant system. In Tables 1-4 show some relevant data pertaining to the ML-1 design.
Figure 1. Schematic of ML-1 plant system
Table 1. General information on temperatures, pressures, etc
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Particulars
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Information
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Design ambient temperature
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100 °F
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Coolant
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Nitrogen gas
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Coolant flow
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95000 lb/hr
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Compressor inlet temperature
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132 °F
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Compressor inlet pressure
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117 Psia
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Compressor outlet temperature
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366 °F
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Compressor outlet pressure
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320 Psia
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Reactor inlet temperature
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791 °F
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Reactor inlet pressure
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313 Psia
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Turbine inlet temperature
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1200 °F
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Turbine inlet pressure
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289 Psia
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Turbine outlet temperature
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901 °F
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Turbine outlet pressure
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120 Psia
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Pre-cooler inlet temperature
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479 °F
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Pre-cooler inlet pressure
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118 Psia
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Table 2. Turbine-compressor set details
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Particulars
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Radial Flow Compressor
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Speed
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Turbine stages
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Turbine rotor material
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Turbine blade material
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Turbine stator blade material
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Expansion ratio
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Compressor stages
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Compression ratio
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Table 3. Recuperator details
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Particulars
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Details
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Length
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81 inches (with external insulation)
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Outside diameter
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45 inches (with external insulation)
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High pressure inlet (header dimension)
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8 inches
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High pressure outlet (header dimension)
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8 inches
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Low pressure inlet (header dimension)
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20 inches
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Low pressure outlet (header dimension)
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14 inches
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Effectiveness
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80.75%
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High pressure loss percentage Δp/p
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1.61%
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Low pressure loss percentage Δp/p
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1.06%
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Type
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Shell and tube regenerator
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Table 4. Pre-cooler details
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Particulars
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Details
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Pre-cooler length
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128 inches
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Width
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113 inches
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Thickness of pre-cooler core
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15 inches
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Thickness of fans and plenums
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17 inches
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Material of tubes and fins
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Series 1100 aluminum
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Material of headers
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Series 2219 aluminum
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Pre-cooler header, inlet
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14 inches
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Pre-cooler header, outlet
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10 inches
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Effectiveness
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93%
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Total Δp/p
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1.55%
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Air flow
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289,000 lb/hr
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Type
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Fin fan air-to-gas exchanger
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Tubes
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1131 tubes, single pass
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Surface
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Internal and external fins
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Question 1:
Calculate the thermal efficiency of the ML-1 nuclear plant using the information provided in Table 1-4. Please note that you may not need to use all the information provided. Figure 2 shows a simplified version of Figure 1. Figure 3 shows a T-S diagram that corresponds with Figure 2. Please show all work.
Figure 2. Simplified diagram of ML-1 plant system
Figure 3. Temperature-entropy (T-S) diagram of ML-1 plant system
Question 2:
In Figure 4, a 2nd recuperator (R2) of the same model has been added. Flow control valves have been added to divide the flow going to R1 and R2 from the turbine and the compressor. Find values of the mass flow rates such that the thermal efficiency is greater than that of Question 1.
Figure 4. ML-1 plant system with an additional recuperator