Chao Yu

An efficient and accurate method for optimizing capsule-type plate heat exchangers is proposed in this paper. This method combines computational fluid dynamics simulation, a backpropagation algorithm and multi-objective optimization to obtain better heat transfer performance of heat exchanger structures. For plate heat exchangers, the heat transfer coefficient j and friction coefficient f are a pair of contradictory objectives. The optimization of capsule-type plate heat exchangers is a multi-objective optimization problem. In this paper, a backpropagation neural network was used to construct an approximate model. The plate shape was optimized by a multi-objective genetic algorithm. The optimized capsule-type plate heat exchanger has lower flow resistance and higher heat exchange efficiency. After optimization, the heat transfer coefficient is increased by 8.3% and the friction coefficient is decreased by 14.3%, and the heat transfer effect is obviously improved. Further, analysis of flow field characteristics through field co-ordination theory provides guidance for the further optimization of plates.

A venous retention needle, as an implanted device, is very likely to cause thrombosis. In view of the thrombosis phenomenon caused by retention needles, this paper compares the influence of different superhydrophobic surface retentions on blood flow. Compared with other superhydrophobic bulges, the fluid velocity of the four-prism bulge is the highest (0.08 m/s), and the vorticity and shear force of the hemispherical bulge are higher. A large number of vortices can inhibit thrombosis better. The tire vortices generated in the superhydrophobic convex grooves are important vortices to inhibit thrombosis. The enhancement and development of the tire vortex weakens the resistance near the wall of the needle and reduces the probability of platelet aggregation. The superhydrophobic surface structure studied in this paper can not only provide guidance for the design of venous retention needles with better performance but also provide corresponding technical support for the development of human implantation devices. Graphical Abstract

With the incremental power of construction machinery diesel engines, the power performance of diesel engines and the pollutant emissions from the exhaust gas have imposed increasingly stringent requirements on the intake cooling system of diesel engines. This paper compared the j/f evaluation factors for fin unit bodies of water-cooled intercooler (including straight fins and rectangular misaligned fins) by means of CFD simulation, and found that the rectangular misaligned fins had an 8% advantage in comprehensive performance. With the rectangular staggered fin intercooler, it was found that under the same conditions, the cooling efficiency of the dual-pass water-cooled intercooler is higher than that of the single-pass water-cooled intercooler, and the uniformity factor of the temperature difference field of the dual-pass water-cooled intercooler is 1.5% higher than that of the latter. The accuracy of the overall simulation of the intercooler is verified by the field test. The dual-pass and single-pass water-cooled intercooler both can maintain heat balance under working conditions, and its average air inlet temperature is 10 °C lower than that of the original air-cooled intercooler, which provides support for further reducing the engine air inlet temperature. The results provide a theoretical basis for the performance improvement of water-cooled intercoolers.

This article presents an accurate and efficient optimization method for heat exchanger. The structure of the original heat exchanger was optimized by combining LHS sampling, CFD simulation, radical basis function, and multi‐objective optimization. Since the Colburn factor j and the friction factor f are a pair of conflicting goals, so the multi‐objective optimization is adopted. The optimization results showed that the Colburn factor j increased by 5.43% and the friction factor f decreased by 23.31%, indicating that the optimized structure had higher heat transfer efficiency and lower resistance performance. The heat transfer mechanism and optimization effect of heat exchanger are explained by using the field synergy principle, which provides a theoretical basis for the structural design optimization of heat exchanger.

This paper presents a method for optimizing wavy plate-fin heat exchangers accurately and efficiently. It combines CFD simulation, Radical Basis Functions (RBF) with multi-objective optimization to improve the performance. The optimization of the Colburn factor j and the friction coefficient f is regarded as a multi-objective optimization problem, due to the existence of two contradictory goals. The approximation model was obtained by Radical Basis Functions, and the shape of the heat exchanger was optimized by multi-objective genetic algorithm (MOGA). The optimization results showed that j increased by 17.62% and f decreased by 20.76%, indicating that the heat exchange efficiency was significantly enhanced and the fluid structure resistance reduced. Then, from the aspects of field synergy and tubulence energy, the performance advantage of the optimized structure was further confirmed.

This paper compares the performances of three Computational Fluid Dynamics (CFD) turbulence models, Reynolds Average Navier-Stokes (RANS), Detached Eddy Simulation (DES), and Large Eddy Simulation (LES), for simulating the flow field of a wheel loader engine compartment. The distributions of pressure fields, velocity fields, and vortex structures in a hybrid-grided engine compartment model are analyzed. The result reveals that the LES and DES can capture the detachment and breakage of the trailing edge more abundantly and meticulously than RANS. Additionally, by comparing the relevant calculation time, the feasibility of the DES model is proved to simulate the three-dimensional unsteady flow of engine compartment efficiently and accurately. This paper aims to provide a guiding idea for simulating the transient flow field in the engine compartment, which could serve as a theoretical basis for optimizing and improving the layout of the components of the engine compartment.

To improve the accuracy of heat exchanger computational fluid dynamics (CFD) simulations, the transverse resistance coefficient of the cold side and the hot side of the water-cooled charge air cooler (WCCAC) is calculated using the fin element method, and the influence of several common factors on the resistance coefficient of the fin element is analyzed. The transverse resistance coefficient obtained from the simulation of the fin element is substituted into the WCCAC model and compared with experimental data. It was found that the fin element method can simulate the flow field of the WCCAC accurately, and the simulation results were closer to the experimental curve compared with the empirical method. This study provides guidance for the optimal design of the heat exchanger and is helpful to shorten the development time and to save costs.

To improve the efficiency of heat transfer from the cooling system of non-road mobile machinery, a modification has been made to the classic cooling system. Specifically, we divide the classic cooling system into two independent cooling loops, namely, the high-temperature cooling loop and the low-temperature cooling loop. Through simulation and experimentation, the dual-loop cooling system was systematically studied, and it was found that the heat dissipation of the dual-loop cooling system was better than that of the single-loop cooling system. In comparison with the classic cooling system, the volume factor of our system increased by 49.3%, the power factor increased by 24.5%, the effective drag coefficient increased by 5.8%, and the compressed air loop length was shortened by 54.5%. In addition, the dual-loop cooling system can greatly reduce the temperature of pressurized air. The proposed new system can better meet the cooling needs of non-road mobile machinery.