Celen, Ali; Budak, Selahattin; Celen, Pınar; Dalkılıç, Ahmet Selim

Many applications use metallic heat exchangers, but some operating conditions, such as desalination, exhibit wear and corrosion problems. Thus, it is important to develop and use alternative materials to metals for such conditions. Although polymers have low thermal conductivity, corrosion resistance, cost-effectiveness, and lightweight, polymer heat exchangers can be constructed to overcome this problem. They were introduced in the last decades; advancements in 3D printing technology help manufacture complex, novel, and thin heat transfer surfaces. Although review studies are limited, recent research has not explored heat transfer-based reviews of heat exchangers produced by additive manufacturing and polymer hollow fibre methods. In this study, polymer heat exchanger works were reviewed and classified according to tube diameter as polymer and polymeric hollow fibre heat exchangers as the most updated ones. Generally, the studies focused on the thermal performance of heat exchangers constructed with metal and polymer materials, and the results were compared to determine the usability of polymer-based ones. As a result, polymeric hollow fibre heat exchangers may compete with metallic ones due to low wall resistance and enhanced heat transfer surface area because of the development of manufacturing technology. Also, the cost and weight of polymeric hollow fibre exchangers are lower, and they can be operated under corrosive conditions. Finally, it is obvious that increased research is needed to enhance the properties of polymer materials to increase the performance of this type of heat exchanger.

Kuleyin, Hamdi; Budak, Selahattin; Yasan, Ömer Barışkan; Gümrük, Recep

The polymer blending method is widely used to obtain balanced mechanical properties and structural performance in many engineering applications. This study investigates the influence of Ethylene-Vinyl Acetate (EVA), and Thermoplastic Polyurethane (TPU) composition ratios on the thermal, chemical, viscoelastic, mechanical, and fatigue life behavior of Acrylonitrile-Butadiene-Styrene (ABS) based elastomeric blends. For this purpose, structural and mechanical properties of the blend material depending on their composition ratio were carried out through a series of characterization analyses, and tensile and fatigue tests. The findings indicated that ABS/EVA and ABS/TPU blends formed an immiscible structure. In addition, it was determined that the storage modulus of the blend with 10 % TPU improved because of the presence of new absorption peaks in the structure. The mechanical properties such as elastic modulus, yield strength, and ultimate tensile strength decreased concerning neat ABS with an increase in the EVA and TPU composition ratio for blend materials. However, the elongation to break was achieved approximately 6 times increasing with an increase in the TPU ratio for ABS/TPU blends. It was determined that the fatigue strength value in ABS/EVA and ABS/TPU blends decreased with the decrease in ABS composition ratio in the blend system. However, it was found that fatigue life improved by 25 % compared to ABS at low-stress amplitude for 10 % TPU additive. Finally, it can be revealed that the ABS-based elastomeric blends can be used to obtain desired properties according to their composition ratios for different applications.

Budak, Selahattin; Çolak, Harun; Yakut, Yusuf

In this study, the effect of aging at different temperatures and times on the properties of AA7075-T6 alloy was investigated. The samples prepared for the experimental studies were subjected to the solution, quenching, and then aging heat treatment at 100 °C and 200 °C for different periods (42-66-90 hours). The properties of the experimental samples were investigated by hardness, compression test, and scanning electron microscope (SEM). As a result of the studies, it was determined that the aging heat treatment had a positive effect on the microstructure and mechanical properties of the AA7075 alloy compared to the reference sample. Especially as a result of the heat treatments at 100 °C, higher results were obtained in hardness and compression strength compared to the initial values.