Demir, Fatih

Effective temperature management is crucial to ensuring the safety, performance, and lifespan of lithium-ion batteries, especially as electric vehicles become more prevalent globally as part of sustainable transport efforts. Significant temperature increases during cycling may reduce efficiency, promote irregular aging, and raise safety concerns. This study aims to improve heat transfer for batteries operating under natural convection at reliable operating temperatures, without requiring maintenance or additional costs at high discharge rates of 7C to 10C. First, the numerical models of the lithium-ion battery and the metal foam are validated through experimental studies. After that, an innovative approach is presented that uses a heat spreader plate and heat spreader metal foam, either separately or in a hybrid, for battery thermal management. It investigates the effect of heat spreader plate thickness (0.5–2 mm), heat spreader metal foam thickness (0.5–2 mm), porosity (5–40), pore per inch (0.899–0.958), hybrid structures (1 to 8 cases), and different coolants (air, mineral oil, synthetic, and natural esters) on battery thermal management. The thermocouple measurements and infrared camera images are evaluated in the experimental study. At the same time, the battery surface temperatures, temperature homogeneity, temperature contours, and velocity vectors are discussed in the numerical model. The results show that increasing the thickness of the heat spreader plate from 0.5 to 2 mm leads to 17.5% and 16% decreases in maximum temperatures at 7C and 10C discharge rates, respectively, at 100% discharge depth. The battery temperatures depend on the varying thicknesses rather than the changing positions of the heat spreader plate and heat spreader metal foam that form the hybrid structures. On the battery surface with a heat spreader plate and with a heat spreader foam, mineral oil reduces the maximum battery surface temperature by factors of 1.6 and 1.92, respectively, compared to air. Increasing the pore per inch at a given ε reduces temperature homogeneity on the battery surface.

Karakoyun, Yakup; Katipoğlu, Okan Mert; Dogan, Ahmet; Canbaz, Ali

PV systems meet energy demand, but environmental and operational factors affect their performance. This study used a three-scenario ablation framework to predict PV power from baseline meteorological and operational variables to under-panel temperature and finally to the full thermal configuration, including water temperature (a newly studied variable). Scenario 1 included time, air temperature, panel angle, relative humidity, and average wind speed; Scenario 2 added under-panel temperature; and Scenario 3 added water temperature. Direct thermal predictors were evaluated separately from meteorological inputs using this design. Four sophisticated ML algorithms, Random Forest (RF), CatBoost, Support Vector Machine (SVM), and one-dimensional Convolutional Neural Network (1D CNN), were refined by Randomized Search (RS) and evaluated using metrics. According to the first group of power prediction results under the full Scenario 3 configuration, the CatBoost-RS model demonstrated superior performance with RMSE = 10.61, MAE = 8.41, AIC = 222.22, KGE = 0.957, and R2 = 0.99. For the second group, the SVM-RS model outperformed others, achieving RMSE = 8.02, MAE = 5.50, AIC = 200.36, KGE = 0.994, and R2 = 0.992. Comparative analysis showed that CatBoost-RS was the most robust predictor, while RF exhibited proficiency in managing nonlinearity in this experimental setting. One-way ANOVA, paired t -test, Wilcoxon signed-rank test, bootstrap confidence intervals, and effect size (Cohen’s d) analyses across both groups show that optimised ensemble and kernel-based models outperform the convolutional approach in predictive performance. Experimental validation and high predictive accuracy improve PV performance prediction in the proposed method.

Yilmaz, Harun; Schröder, Lukas; Hillenbrand, Thomas; Brüggemann, Dieter

The most important stages determining the qualitative and quantitative characteristics of a combustion process are mixture preparation, ignition, combustion itself and pollutant emissions. Among these, the ignition phenomenon stands out in terms of ensuring a reliable operation under every working condition (which also affects subsequent stages). In this study, the influence of the properties and the type of the ignition source on combustion and flame propagation characteristics of methane/air mixtures were investigated by using a passively Q-switched Nd:YAG crystal laser and a pre-chamber ignitor in a constant volume combustion chamber. The number of consecutive pulses and the air-fuel-equivalence ratio are studied parameters. With the laser ignition system, it was possible to ignite fuel-air mixtures at very lean conditions. However, as flow conditions in the combustion chamber varied due to the protruding part of the pre-chamber ignitor, ignition possibility decreased and combustion metrics worsened. The number of pulses affected combustion parameters such as the ignition delay time, the combustion duration, the rate of pressure rise etc. in a non-monotonic manner. Deteriorations and improvements on such parameters were detected depending on the air–fuel-equivalence ratio λ.

Çomakli, Kemal; Çakir, Uǧur; Kaya, Mehmet; Bakirci, Kadir

The most popular method to benefit from the solar energy is to use solar water heating systems since it is one of the cheapest way to benefit from the solar energy. The investment cost of a solar water heating system is very low, and the maintenance costs are nearly zero. Using the solar energy for solar water heating (SWH) technology has been greatly improved during the past century. A storage tank is used in many solar water heating systems for the conservation of heat energy or hot water for use when some need it. In addition, domestic hot water consumption is strongly variable in many buildings. It depends on the geographical situation, also on the country customs, and of course on the type of building usage. Above all, it depends on the inhabitants' specific lifestyle. For that reason, to provide the hot water for consumption at the desirable temperature whenever inhabitants require it, there must be a good relevance between the collectors and storage tank. In this paper, the optimum sizes of the collectors and the storage tank are determined to design more economic and efficient solar water heating systems. A program has been developed and validated with the experimental study and environmental data. The environmental data were obtained through a whole year of operation for Erzurum, Turkey.

Tandiroglu, Ahmet

The effect of flow geometry parameters on transient entropy generation for turbulent flow in a circular tube with baffle inserts has been investigated. Different flow geometry parameters of pitch to diameter ratio (H/D), baffle orientation angle (β), ratio of smooth to baffled cross-section area (So/Sa) and ratio of tube length to baffle spacing (L/H) were varied parametrically during the experiments. One smooth tube and nine different baffle inserted tubes geometries were tested. The characteristic parameters of the baffled tubes are pitch to tube inlet diameter ratio H/D = 1, 2 and 3; baffle orientation angle β = 45°, 90° and 180°. The time averaged entropy generation corresponding to the flow geometry parameters were compared under the condition of constant heat flux. Air having a Prandtl number of 0.71 was used as working fluid, while stainless steel was considered as the pipe and baffle material. Nine empirical equations were derived to correlate the time averaged entropy generation as a function of the Reynolds number and the other experimental individual flow geometry parameters, pitch to diameter ratio, baffle orientation angle, ratio of smooth to baffled cross section area and ratio of tube length to baffle spacing. Finally, the general empirical correlation of the time averaged entropy generation was developed and considered to be applicable within the range of Reynolds number 3000 ≤ Re ≤ 20,000 in the form ofSgenave (t) = 0.0054 Re- 0.793 Pr0.4 (H / D)- 0.656 (So / Sa)- 14.006 β- 0.0264 (L / H)- 0.6051 ..

Gürses, A; Doymus, K; Dogar, Ç; Yalçin, M

Oil agglomeration is an effective technique for recovering and reducing the ash of coal fines. In this study, the effects of some parameters that markedly influence the effectiveness of selective oil agglomeration, such as solids concentration, amount of agglomeration oil and agglomeration time, on the recovery of agglomerate and the ash and the pyritic sulphur content of the agglomerates were investigated. In order to delineate the relation between the formation rate of coal-oil agglomerates and the removal of ash and pyritic sulphur, the rates of agglomeration for Balkaya and Askale lignites were also calculated by using experimental data. It was found that the success of the process in terms of both recovery and selectivity for lignites was highly dependent on the parameters and control of the agglomeration rate. (C) 2002 Elsevier Science Ltd. All rights reserved.