The shell-and-tube type heat exchangers have long been widely used in many fields of industry. These types of heat exchangers are generally easy to design, manufacturing, and maintenance, but require relatively large spaces to install. Therefore, the optimization of such heat exchangers from thermal and economical points of view is of particular interest. In this article, an optimization procedure based on the minimum total cost (initial investment plus operational costs) has been applied. Then the flow analysis of the optimized heat exchanger has been carried out to reveal possible flow field and temperature distribution inside the equipment using CFD. The experimental results were compared with CFD analyses results. It has been concluded that the baffles play an important role in the development of the shell side flow field. This prompted us to investigate new baffle geometries without compromising from the overall thermal performance. It has been found that the heat exchanger with the new baffle design gives rise to considerably lower pressure drops in the shell side, which in turn reducing operating cost. The new baffle design is particularly well suited for shell-and-tube heat exchangers, where a viscous fluid-flows through shell side with/out phase change.

In this study, the optimisation of a mixed flow fan, which is widely used in industrial applications has been made using computational fluid dynamics. In the optimisation process, the CAD file of the mixed flow fan, which can operate under the specific conditions, has been created and preliminary design has been realised. Blade angle, wall thickness and length parameters were taken, and the blades have been optimised by using Ansys/response surface optimisation (RSO) tool. Fans were produced in preliminary and optimised design, and experimental studies were carried out in a laboratory. As a result of optimisation, the maximum shaft power of the design-improved mixed flow fan was reduced by 8.62%, while an increase of 8.70% in total pressure value for the best operating point was achieved. In addition, the yield of the mixed flow fan was increased by 16.42%, while the sound pressure level has been decreased by 1.52%.

In this study, performance of a heat exchanger used in combi boilers was investigated numerically for different fin geometries. Analyses were performed at the boiler operation conditions. A commercial CFD software package, FLUENT, was used for numerical simulations. The 3-D steady-state turbulent flow field analysis was carried out and k-? model was preferred as the turbulence model. In the analysis, it was assumed that the heat transfer phenomenon occurred both by conduction and convection. Flat fin geometry was taken as a reference for the investigation. Variation of the heat transfer and pressure drop values for the wavy fin were compared with the reference geometry. The wave angle and wave radius were taken as the parameters for the wavy fins. For different fin geometries: the outlet temperaTure of the combustion gases, the heat transfer to the water, and the pressure drop were calculated and the results were presented. Compared with flat fin, average decrease for the outlet temperature of hot gases was obtained as 4 K and average increase for the heat transfer to the water was calculated as 0.68 W. On the other hand, the average pressure drop in the heat exchanger with wavy fins was about 70% higher than the flat fin.

В статье представлены результаты исследовательских работ по определению эффективных параметров ножа для обработки почвы и внесения жидких удобрений. В ходе исследования с помощью программы Ansys Fluent® была разработана модель области потока, проведены численные расчеты и путем оптимизации определены эффективные параметры микроканала ножа, результаты были проверены экспериментальным путем. Оптимальные размеры для ножа с эффективной рабочей шириной w = 150 мм являются: d = 4 мм, L = 20 мм, h = 0,1 мм. Хотя, применение Ansys Fluent® могло определить скорость на выходе (Vo) и количество истекающей жидкости из щели микроканала, давления области потока и другие параметры в пределах заданной скорости подачи Vi = 3 м/с, но получить ожидаемую модель жидкой пленки не было возможным. Скорости подачи, которой способен формировать полную пленку определена на основе экспериментов: Vi = 5-6 м/с для КАС-32, и 5-7 м/с для воды. В ходе исследования были выявлены факторы, влияющие на равномерность количества жидкости, вытекающей из щели микроканала. Были проанализированы выявленные отклонения и их причины. В опытах, проведенных с применением воды и КАС-32, где имеется разная плотность и вязкость, сравнивалось поведение потока, а также было проверено влияние температуры. Для будущих работ было предложено учитывать явление поверхностного натяжения в численных анализах, и уменьшить объем канала подачи с целью экономии расхода жидкого удобрения.

Heat exchangers are widely used in various fields, emphasizing the importance of efficiency and mass/dimensional improvements. Aluminium boiler heat exchangers play a crucial role in systems where the natural gas-air fuel mixture is burned, and heat transfer to water occurs. Today there are 2 most popular types of heat exchangers used in domestic type boilers: spiral-type and cast-type. In these heat exchanger designs, the region where the air-gas mixture burns is referred to as the "combustion chamber," and the thermal energy produced is transferred to the circulating water in the body.In this study, the innovative pin geometry of the DAIKIN NDJ 24 kW aluminium cast boiler heat exchanger is utilized. Feasibility and cleanability limits were defined, and the unique symmetric droplet model was optimized through a CFD-based RSM optimization approach. The thermal performance predicted by the CFD studies were then experimentally validated using the experimental setup existed at the DAIKIN’s factory in Sakarya/TÜRKİYE.