Fundamental study of key issues related to advanced sCO₂ Brayton cycle: Prototypic HX development and cavitation

Abstract

Chapter 1 Compact discontinuous fin style diffusion bonded heat exchangers for the sCO 2 Brayton cycles Abstract Diffusion bonded heat exchangers are the leading candidates for the sCO 2 Brayton cycles in next generation nuclear power plants. Commercially available diffusion bonded heat exchangers utilize set of continuous semi-circular zigzag micro channels to increase the heat transfer area and enhance heat transfer through increased turbulence production. Such heat exchangers can lead to excessive pressure drop as well as flow maldistribution in the case of poorly designed flow distribution headers. The goal of the current project is to fabricate and test potential discontinuous fin patterns for diffusion bonded heat exchangers; which can achieve desired thermal performance at lower pressure drops. Prototypic discontinuous offset rectangular and Airfoil fin surface geometries were chemically etched on to 316 stainless steel plate and sealed against an un-etched flat pate using O-ring seal emulating diffusion bonded heat exchangers. Thermal-hydraulic performance of these prototypic discontinuous fin geometries was experimentally evaluated and compared to the existing data for the continuous zigzag channels. The data generated from this project will serve as the database for future testing and validation of numerical models. Re High zigzag Medium zigzag Low zigzag Desgined rectangular Offset fins Chapter 4 Techno-economic analysis of heat rejection options for the sCO 2 Brayton cycles Abstract Techno-economic feasibility of dry air cooling the supercritical carbon dioxide (S-CO 2) Brayton cycle has been investigated. A radiator type CO 2-to-air heat exchanger has been identified in the current market in an attempt to reduce the capital cost of the power plant. A quotation for the same is obtained and the heat exchanger was modeled in engineering equation solver (EES) to confirm the quoted heat exchanger performance and sizing. A cost-based optimization procedure was employed to identify the cycle optimum operating conditions with the goal of minimizing the plant capital cost per unit electrical output ($/kWe) for the Advanced Fast reactor (AFR) with 250 MW th heat input. Cycle operating conditions such as minimum temperature, minimum pressure, and maximum pressure are chosen as the parameters to be optimized. Minimum pressure and minimum temperature are selected to be in the vicinity of pseudo-critical line to take advantage of the high fluid density near the pseudo-critical point while an increasing minimum CO 2 temperature is dictated by the ambient air temperature. The cycle maximum pressure is varied from 18 to 30 MPa. The mechanical design of the cycle heat exchangers (reactor intermediate sodium-to-CO 2 heat exchanger, high temperature recuperator, and the low temperature recuperator) and the piping are modified as per ASME code requirements to withstand the higher cycle design pressures. The associated change in the cost of components is also taken into account. All the calculations are performed using th...

Integrated Heat Exchanger-Phase Change Material Thermal Energy Storage System

“…These HXs generally have compact plate-fin structures [23][24][25]. Among them, the diffusionbonded, printed-circuit HX, with a very high power density, can operate at high pressures and high temperatures [26]. These high-efficiency HX approaches can generally be adopted for TES system applications.…”