Journal of Naval Sciences and Engineering

3-17

Authors: Yasemin TABAK Şeyda POLAT Ayşen KILIÇ Bayise KAVAKLI VATANSEVER

Alumina powders are utilized in many industries like electronics, metallurgy optoelectronics, and fine ceramic composites. In this study, non-aqueous-based tape casting of alumina was carried out in a non-continuous single-blade tape casting machine. A slurry of alumina powder in a solvent was cast on a stationary surface with additives like dispersants, binders, and plasticizers. After the green tapes were dried, they were sintered to obtain the final desired shape. The hydraulic pressing method was used to increase the density of the alumina tapes. Layered alumina ceramics were produced at 5 different temperatures by pressureless sintering method (1450°C, 1500°C, 1550°C, 1600°C and 1650°C) for 5 h to observe the effect of sintering temperature. Results revealed the sintering conditions for obtaining translucent alumina, with the utilized slurry composition. Translucent alumina ceramics have gained importance as parts of semiconductor devices, substrates for electric parts, as heat/corrosion materials in reaction tubes and crucibles, and are used in medical equipment.

35-51

Authors: Ahmet Yiğit ARABUL Celal Fadıl KUMRU

Submarine cables are critical assets that play an indispensable role in interconnected power systems, particularly in cross-sea energy transmission and offshore wind turbines. Their importance is further accentuated in exigent situations such as natural disasters and war, which emphasize the need for secure, reliable and uninterrupted energy supply. Furthermore, the investment and operating costs of submarine cables are relatively higher than other power system equipment, making it essential to operate them under the rated operating conditions to prevent possible faults and ensure power system stability. As thermal stress can lead to damage of cable insulation, it is an essential parameter to consider. Overloading increases thermal stress, resulting in rapid aging of the cable insulation and a shorter cable lifetime. Therefore, it is imperative to determine the maximum conductor temperatures and current carrying capacities of submarine cables under varying loading rates and ambient conditions using thermal analysis. In this study, thermal analyses are carried out for a three-phase, 220 kV HVAC, XLPE insulated submarine cable under different loading conditions. The findings demonstrate that the maximum temperature, current carrying capacity, and total losses of the cable are significantly impacted by loading rate, phase imbalance, and seawater temperature.

77-100

Authors: Alpay ACAR Murat URYAN Ali DOĞRUL Asım Sinan KARAKURT Doç. Dr. Cenk ÇELİK

HVAC system design and optimization of the ventilation and air-conditioning of indoor environments are crucial for human comfort. Especially in recent years, due to the Covid pandemic, the importance of this hot topic is noticed. This study aims to focus on the HVAC performance of a dorm compartment onboard a naval surface ship since the ship environment is a good example of indoor air ventilation problem. The HVAC performance was investigated using a RANS solver. The numerical analyses were conducted for different scenarios and the results were finally discussed in terms of HVAC system location, air temperature, air intake and outlet conditions. As a conclusion, the current HVAC system design was found insufficient and alternative solutions were proposed in order to improve indoor air quality and thermal comfort.