This study presents the development of a multi-objective adaptation of the set trimming method (multi-objective set trimming [MOST]), designed as a reliable and globally efficient optimization approach. Then, its application to shell and tube heat exchangers is presented, and the results are compared with those of the fast and elitist nondominated sorting genetic algorithm (nondominated sorting genetic algorithm II [NSGA-II]) and exhaustive search in terms of both computational time and convergence. Effectiveness and annual cost are considered as the fitness functions, and the heat exchanger geometric parameters, including eight design parameters, are selected. The optimization results revealed that the optimum Pareto fronts in the case of NSGA-II are totally dominated by the results obtained using MOST in all studied cases. In addition, using MOST, the effectiveness of the final optimum solution is improved by 0.94-2.10% as compared with NSGA-II. On the other hand, as well as effectiveness, the annual cost is also improved simultaneously as compared with NSGA-II, with the percentage in the range of 1.07-5.41%.
Buoyancy-driven fluid movement gives rise to free or natural convection, which occurs without external influences. This study numerically examines free convection within an air-saturated square porous enclosure featuring a vertical wavy wall. Heat is applied linearly from the bottommost boundary, while the upper boundary is adiabatic and the side boundaries are at a lower temperature. The study examines the effects of varying Rayleigh number, Ra (103-106), Darcy number, Da (10-4-10-1), and wavy numbers (2, 4, and 8) on thermofluid properties with the support of entropy generation, stream functions, isotherms, and Nusselt number (Nu). The SIMPLE algorithm is used to solve the governing differential equations generated through a numerical route using ANSYS Fluent. Results demonstrate that at higher Ra (105 and 106), flow circulation intensifies significantly due to augmented buoyancy forces, particularly at Da 10-2, where the values of circulation strength at the center reach 4.51 and 10.33, respectively. Additionally, higher wavy numbers lead to the augmentation of Nu. Circulation strengths of 0.0828, 0.0911, and 0.112 are observed for wavy numbers of 2, 4, and 8, respectively.
The rising global demand for energy-efficient heating systems has increased interest in [Formula: see text]-based transcritical heat pumps due to their unique thermodynamic behavior and environmental advantages. However, conventional models struggle with the nonlinear nature of transcritical cycles, and existing artificial neural network (ANN) approaches often fail to capture key interacting parameters under varying conditions. This study presents an advanced ANN-based model to accurately predict the performance of a [Formula: see text] transcritical heat pump, validated against experimental data. A feed-forward neural network is developed to analyze nonlinear system relationships using six input parameters: initial charge state, throttle valve opening, evaporator and gas cooler water flow rates, and their respective temperatures. Five performance metrics are predicted: coefficient of performance, cooling capacity, heating capacity, compressor work input, and discharge pressure. The model is trained and validated using experimental data from 36 operating conditions, with dataset size determined through statistical power analysis to prevent overfitting. High prediction accuracy is achieved, with [Formula: see text] values ranging from 0.956 to 0.986 and MSE between [Formula: see text] and [Formula: see text]. Compared to conventional methods, the ANN model is more accurate, efficient, and practical and can be extended to optimize and analyze various transcritical [Formula: see text] system configurations.
Waveriders achieve high aerodynamic efficiency by sustaining an attached shock along the lower surface. However, the proximity of the shock and sonic surface (M=1) to the body results in significant thermal loading due to entropy confinement. This study investigated an integrated passive-active aerothermal control strategy for a hypersonic waverider at Mach 6 under high-altitude conditions using design-oriented Reynolds-averaged Navier-Stokes simulations. This approach combines blunt-nose shaping, sonic jet injection, and geometric surface modification to influence shock-entropy coupling and surface pressure distribution. A gas mixture with a high heat-capacity ratio (80% helium and 20% argon) was injected sonically through the nose to modify local thermoacoustic properties associated with Sanal flow choking, displace the sonic surface outward, and reduce entropy transport toward the wall. Surface shaping induced streamtube divergence, which led to controlled Prandtl-Meyer expansion and improved aerodynamic load distribution. Results show that increasing sonic-surface standoff distance is associated with increased shock standoff distance and reduced aerodynamic heating potential while maintaining or improving lift-to-drag ratio. The analysis includes quantitative evaluation of sonic-surface standoff distance and nondimensional Vinay-layer thickness. Although configuration-specific, the results establish a design-oriented framework linking thermoacoustic effects and surface shaping for coupled aerodynamic and thermal performance improvement.
To address the thermal management challenges of the rudder shaft of hypersonic vehicles in extreme thermal environments ranging from 900 to 1100 degrees C, this study proposes an active cooling system based on internal thread-smooth composite microchannels, which enhances cooling efficiency by intensifying phase-change heat transfer. To verify the system performance, dual experimental platforms for electrical heating (double left arrow 600 degrees C) and electromagnetic heating (double left arrow 1100 degrees C) were established, and cross-scale verification was completed in combination with numerical simulation (experiment-simulation error <3%). The influence of contact thermal resistance (CTR=0.008 (m2 & sdot;K)/W) and three flow rates (5.5, 7, and 10 mL/min) on the temperature field was analyzed. Compared with smooth channels, the M1 internal-thread composite channel increases the heat transfer coefficient from 3200 to 3780 W/(m2 & sdot;K) (18%) and reduces the rudder-shaft temperature by 44-55 degrees C under a 1039-1043 degrees C heat source. The pressure drop rises from 0.04 to 0.06 MPa, but the additional hydraulic power remains very small at the present flow rates, while the coolant demand is markedly reduced. In this study, the term lightweight refers to reduced coolant inventory and a compact embedded cooling architecture rather than a full vehicle-level mass audit.
