Coiled Tube Gas Heaters For Nuclear Gas-Brayton Power Conversion

Abstract

Additionally, THERMOFLEX has the capability of estimating sizes of shell-and-tube heat exchangers, which although are not anticipated for use in our reference design, give an upper bound on component sizes, and are presented in Table 2. The high temperature recuperator requires approximately 14,000 m 2 of surface area given an overall heat transfer coefficient of 500 W/°C•m², which translates to a size of 4.9 by 23.6 m. As mentioned earlier this is about twice or more the size of the other heat exchangers, and also points to the need for a more compact design due to the low overall heat transfer coefficient. Spiral wound heat exchangers have overall heat transfer coefficients in the range of 700-2500 W/°C•m² [3], implying that the calculated volumes (lengths) in Table 2 can be reduced by a factor of 2 to 5. Component HT Recoup LT Recoup Water Cooler U 500.1 525.6 889.7 W/°C•m² A 13,859 6,387 4,299 m² D 4.864 4.22 3.183 m L 23.6 18.28 13.56 m V 438.5 255.7 107.9 m³ A/V 31.6 25.0 39.8 m²/m³ The development of a "high temperature" (700°C) CTGH design was deemed to be impractical due to the low allowable stresses of current code qualified materials at the anticipated operating point conditions. As such, a CTGH design and component sizing for the "medium-high temperature" (550°C) operating conditions appropriate for application to SFR's is being pursued. An "unconstrained" CAD model of the integral power conversion unit (PCU) was created, allowing for design flexibility based on estimated sizes of components. The major constraints imposed are simply the outer diameter of the vessel to maintain rail transportability. Figure 3 depicts the initial PCU design, including the turbomachinery, generator, external ducting with flow paths, recuperators and cooler. More detail will be added, including appropriate sizes for the heat exchangers, flow paths, insulation, etc. during the coming quarter.