Kalkan, Orhan; Celen, Ali; Bakirci, Kadir

This paper examines the thermal management of a commercial 20 A h lithium ferro phosphate battery with the cold plates containing the serpentine tube structure, which is frequently preferred in heat exchanger applications. A numerical analysis is performed to explore the battery surface temperature distribution under varying operating conditions. In the study, an experimentally verified electrochemical thermal compound model was created and temperature distributions at the end of discharge at 1C, 3C, and 5C rates are obtained. The effects of different inlet temperatures (15°C, 25°C, and 35°C) and volumetric flow rates (0.1 L/min, 0.6 L/min, and 1.1 L/min) of the coolant on the two vital parameters of battery thermal management –- maximum battery temperature and maximum battery temperature difference –- are investigated for each discharge rate. As a key finding in this study, there is an acceleration of temperature variation from the middle part of the battery with the minimum temperature to the terminals with the maximum temperature, at the end of the discharge, in the use of a serpentine cold plate. Under the conditions where the coolant flow rate is maximum and the inlet temperature is minimum, the highest maximum temperature difference is 14.4°C, while the lowest maximum temperature difference is 10.8°C under the conditions where the coolant flow rate is minimum and the inlet temperature is maximum. Besides, the correlation equations in which the adjusted R2 values for maximum battery temperature difference and maximum battery temperature are 98.0% and 99.6%, respectively, are developed.

Ata, İsmail; Tanürün, H. Erdi; Uzun, Sinem; Bayrak, Sebile; Acır, Adem

The exergy analysis and determination of irreversibility İ of a thermal power plant with 210 MW are presented in this study. The first- (ηI) and second-law (ηII) efficiencies, losses, and İ are computed for each component in the plant. The highest energy loss (43.538%) occurs with heat transfer to cooling water of the condenser, whereas the second loss (14.138%) occurs in the boiler. The highest İ value in the cycle (86.87%) occurs in the boiler followed by the turbine (5.95%). The ηI and ηII efficiencies of the whole plant are 38.64% and 31.68%, respectively. In addition, effects of the efficiencies in the temperature range from 5°C to 30°C are investigated. The ηI efficiency of the whole plant does not change, whereas the ηII efficiency decreases with increasing reference temperatures. In addition, the ηII efficiency is associated with environmental impact and sustainability.

Acir, Adem; Canli, Mehmet Emin; Ata, Ismail; Uzun, Sinem; Tanürün, Himmet Erdi

In this paper, the energy storage behavior of the thermal energy storage unit (TESU) using phase change material (PCM) and copper fi ns under artifi cial solar radiation was analyzed experimentally. The experimental tests of the TESU were performed at three diff erent fi n numbers (n = 3, 5, and 7) and fi n thickness (t = 1, 1.5, and 2 mm) under variable solar radiations (q = 800, 900, and 1000 W/m2). The stored thermal energy of each TESU was calculated and compared with solar energy coming from a solar lamp. The highest thermal energy storage effi ciency was computed as 95.08% in Type-VIII (n = 7, t = 1 mm) TESU below 1000 W/m2 solar fl ux. The thermal energy storage effi ciency enhancement ratio (TESEER) was defi ned to understand the eff ects of n and t of the thermal energy storage effi ciency of TESUs. The highest TESEER was calculated as 1.68 in Type-VIII (n = 7, t = 1 mm) TESU below 1000 W/m2 solar radiation. In conclusion, the TESEER values were decreased with increasing fi n thickness, whereas its values were usually increased with the increase number of fi ns.

Genc, Yasin; Uzun, Sinem; Acir, Adem

This study is aimed at investigation of the potential effects of various nanoparticles used in certain properties and ratios in the coolant of VVER-1200 power plant on thermal hydraulic performance. Criticality and thermal hydraulic analysis have been performed by using MCNP and COBRA-IV/PC code, respectively. The fuel ratio has been selected as 90% ThO2 + 10% reactor grade (RG)-PuO2. Al, Cu, Si, and Ag nanoparticles in proportions of 0.01% and 0.1% by volume have been mixed with reactor coolant water. The effects of adding nanoparticles into the coolant at two different ratios on the reactor criticality, departure from nucleate boiling ratio (DNBR), and thermal hydraulic performance have been investigated. It is observed that by adding nanoparticles into the coolant, the temperature rise along the hottest channel is higher compared to the case when only water is used as the coolant, whereas the criticality and DNBR have shown a decreasing trend. It can be concluded that combination of fuel made up of 90% ThO2 + 10% RG-PuO2 and nanofluid containing 0.1% volumetric ratio of Si nanoparticle could be used in VVER-1200 nuclear power plant and this combination could contribute to augmentation of thermal efficiency of the plant.

Acır, Adem; Uzun, Sinem; Genç, Yasin; Asal, Şulenur

The use of nanofluids has recently gained importance in studies carried out on increasing reactor efficiency with attention paid on safety factors in nuclear technology. Nanofluids used in reactor cooling water at certain properties and ratios generally use enriched UO2 as fuel. Through the discovery of thorium reserves and its use in nuclear technology, thorium has also become a candidate for being used as a fuel material in reactors. In this study, using ThO2 fuel and Al2O3, CuO, and TiO2 nanoparticles of the coolant in different ratios, the neutronic and thermal properties of the reactor, especially the criticality and temperature of coolant and DNBR as three leading parameters, were investigated. For the analyses, 5%, 10%, 15%, and 20% ThO2 was added to the reactor core containing 3.7% enriched UO2 fuel, and the analyses were performed adding 0.01%, 0.05%, and 0.1% volume of nanoparticles to the coolant water. Neutronic calculations were carried out with the help of MCNP code and COBRA-IV PC code was used for thermal analysis. The obtained results showed that by adding nanoparticles to coolant and using thorium as an additive to fuel the rise of coolant temperature can be augmented by 4.67 K compared to traditional combination of UO2 fuel and water while reactor remained within safety limits.