Numerical Investigation of the Thermo-Hydraulic Performance of Water-Based Nanofluids in a Dimpled Channel Flow using Al₂O₃, CuO, and Hybrid Al₂O₃-CuO as Nanoparticles

In this study, the authors study the impact of spherical dimple surfaces and nanofluid coolants on heat transfer and pressure drop. The main objective of this paper is to evaluate the thermal performance of nanofluids with respect to different Reynolds numbers (Re) and nanoparticle compositions in dimpled channel flow. Water-based nanofluids with Al2O3, CuO, and Al2O3-CuO nanoparticles are considered for this investigation with 1%, 2%, and 4% volume fraction for each nanofluid. The simulations are conducted at low Reynolds numbers varying from 500 to 1250, assuming constant and uniform heat flux. The effective properties of nanofluids are estimated using models proposed in the literature and are combined with the computational fluid dynamics solver ANSYS Fluent for the analysis. The results are discussed in terms of heat transfer coefficient, temperature distributions, pressure drop, Nusselt number, friction factors, and performance criterion for all the cases. For all cases of different nanoparticle compositions, the heat transfer coefficient was seen as 35%-46% higher for the dimpled channel in comparison with the smooth channel. Besides, it was observed that with increasing volume fraction, the values of heat transfer and pressure drop were increased. With a maximum of 25.18% increase in the thermal performance, the 1% Al2O3/water was found to be the best performing nanofluid at Re = 500 in the dimpled channel flow

State-Of-The-Art and Review of Condensation Heat Transfer for Small Modular Reactor Passive Safety: Experimental Studies

This study focused on state-of-the-art and review of condensation heat transfer for small modular reactors (SMR). Nuclear reactors adopt passive containment cooling systems (PCCS) for accident mitigation, containment integrity, and primarily to maintain the last barrier for radioactive particle release to the environment during and beyond design-basis accidents. However, improving the effectiveness of the PCCS is more critical for the SMR than for commercial reactors to ensure higher safety margins and compactness. In the PCCS of SMR, due to its smaller size containment, the filmwise condensation (FWC) is dominant. Therefore, this study emphasized the FWC. Earlier condensation studies for the PCCS did not make SMR the primary focus, so a critical review for formulating the state-of-the-art was necessary. Part-1 of this study covered the review of physics phenomena, previous experimental studies with a brief overview of associated test facilities and empirical correlations. This study identified a research gap with the condensation test data scaling relations by using the information and findings of the previous PCCS studies and applied them to the SMR system

Film Condensation with High Heat Fluxes and Scaled Experiments using Pure Steam for Reactor Containment Cooling

Condensation Tests Were Performed using a Newly Developed Test Facility for Scaling the Passive Containment Cooling System (PCCS) to a Small Modular Reactor (SMR). the PCCS of the SMR Plays a Pivotal Role in Ensuring Greater Safety, Reliability, and Compactness Than What is Afforded by Traditional Reactors. Therefore, a Well-Designed PCCS is Essential to SMRs. However, Previous Studies and Test Data Were Unsuitable for Scaling, Due to High Variation in the Test Geometry and Operating Conditions. This Study Intends to Close This Research Gap by using a Novel Designed Scaled Test Facility Consisting of Vertical Condensing Test Sections Featuring 1-, 2-, and 4-Inch-Diameter Condensing Tubes with Annular Water Cooling, and by Applying Superheated and Saturated Steam with Different Steam Mass Flow Ranges of 5–25 G/s. the Primary Test Data, Including Axial Temperatures, Mass Flow Rates, and Pressures, Were Used in Conjunction with a Standard Data Reduction Method to Estimate Critical Parameters Such as Heat Fluxes, Heat Transfer Coefficients, and Condensation Rates. These Scaled Test Data Would Support Improving Empirical Correlations and Validating Condensation Models to Identify Scaling Distortion for SMR PCCSs

Design of Condensation Heat Transfer Experiment to Evaluate Scaling Distortion in Small Modular Reactor Safety Analysis

Designing a novel scaled modular test facility as a part of an experiment for condensation heat transfer (CHT) in small modular reactors (SMRs) is the main focus of this study. This facility will provide data to evaluate models\u27 scalability for predicting heat transfer in the passive containment cooling system (PCCS) of SMR. The nuclear industry recognizes SMRs as future candidates for clean, economic, and safe energy generation. However, licensing requires proper evaluation of the safety systems such as PCCS. The knowledge gap from the literature review showed a lack of high-resolution experimental data for scaling of PCCS and validation of computational fluid dynamics tools. In addition, the presently available test data are inconsistent due to unscaled geometric and varying physics conditions. These inconsistencies lead to inadequate test data benchmarking. To fill this research gap, this study developed three scaled (different diameters) condensing test sections with annular cooling for scale testing and analysis. This facility considered saturated steam as the working fluid with noncondensable gases like nitrogen and helium in different mass fractions. This facility also used a precooler unit for inlet steam conditioning and a postcooler unit for condensate cooling. The high fidelity sensors, instruments, and data acquisition systems are installed and calibrated. Finally, facility safety analysis and shakedown tests are performed

Computational Assessment of Thermo-Hydraulic Performance of Al₂O₃-Water Nanofluid in Hexagonal Rod-Bundles Subchannel

This study investigated alumina nanofluid\u27s thermo-hydraulic performance as a coolant in the subchannel geometry of a hexagonal rod-bundle reactor core using the computational fluid dynamics (CFD) tools. This study analyzed the critical thermo-hydraulic performance-the heat transfer enhancement for an permissible increased pressure drop limit while considering the variation in the volume of nanoparticles concentrations, consistent with the previous related studies. The simulation model was developed for single-phase, forced, and turbulent flow conditions with a homogeneous mixture of species. The simulation results compared with the relevant standard correlations for the inlet Reynold number range of 20,000 to 80,000. Our study exhibited that heat transfer can be improved significantly with the addition of nano-size particles. This rise in heat transfer decreased the fuel clad surface temperature, improving the reactor fuel-clad temperature safety margin. However, the pressure drop also increased considerably, which needed to be within the permissible limit. Therefore, a trade-off between the heat transfer enhancement and drawback of the increased pressure drop within the reactor design limit is recommended