A parametric study on optimization of ring inserted heat exchanger tube

This study presents a parametric optimization of ring inserted heat exchanger tube according toNusselt number and friction factor. The heat exchanger tube was heated with constant heat flux and flowconditions is turbulent corresponding to Reynolds number of 25,000. Inner diameter, thickness and pitchlengths of the rings were considered as factors and each factor is composed of five various levels. The studywas carried out by using a computational fluid dynamics program that is Ansys-Fluent 18.0. Realizable kepsilon turbulence model is employed to simulate the turbulent flow condition. The results showed thatinner diameter, thickness and pitch length of the rings increases, the Nusselt number and the friction factortend to decrease. The configuration of the ring inserted heat exchanger tube provides the highest Nusseltnumber which is the inner diameter of 17mm, the thickness of 4 mm and the pitch length of 50 mm. On theother hand, the configuration of the ring inserted heat exchanger tube provides the lowest friction factorwhich is the inner diameter of 25 mm, the thickness of 10 mm and the pitch length of 250 mm. When theresults are simultaneously optimized according to both the Nusselt number and the friction factor, it wasfound that the best configuration is the inner diameter of 25 mm, the thickness of 2 mm and the pitch lengthof 50 mm.&nbsp;</p

Numerical investigation of battery thermal management by using different phase change materials under extreme working conditions

Owing to increasing globally interest on electrical vehicles, battery thermal management (BTM) issue has critically importance in increasing the life time and safety, decreasing the charging time and cost and weight of the electrical vehicles. Li-ion cells are preferred due to high energy density and lo self-discharge rate, long cycle life. BTM by using phase change materials (PCMs) is sensible due to the melting temperature of PCM is in the range of desired temperature of Li-ion cells. This study aims to compare the performance of different PCMs such as paraffin and n-octadecane to cool a Li-ion cell which are used in electrical vehicles. Time dependent numerical analyzes were conducted to show the performance of PCMs on the BTM at cycle time of 20,000. Boundary condition for the numerical analyzes were considered as different discharging time such as 1C, 3C and 5C. As a result, paraffin appears to undergo a phase change longer than n-octadecane. This is because the paraffin has a higher latent heat value compared to n-octadecane. According to the results, it was able to keep cell temperature between 258-313K by using paraffin at a discharge rate of 1C and 3C. However, n-octadecane was not able to keep the temperature of the cell at desired range at discharge rate of 3C. At 5C discharge rate, neither paraffin nor octadecane could provide the desired cell temperatures. On the other hand, both paraffin and n-octadecane ensured that the temperature difference in the cell remained below 2.5K at all discharge rates.</p

A Brief Review of PCM Based Battery Thermal Management Systems

Battery thermal management (BTM) is a critical issue of modern energy systems, particularly in applications of electrical vehicles (EV). If the heat produced by the batteries is not properly managed, it causes to affect their performance negatively, safety, and overall lifespan. Effective BTM systems (BTMS) are essential to ensure optimal battery operation, prevent thermal runaway events, and maximize energy efficiency. BTMS includes strategies used to control the temperature of the battery, dissipate heat and maintain temperature balance. These strategies are designed to effectively direct and dissipate the heat inside the battery. Thermal management techniques include active and passive cooling methods. Active cooling methods enable to effectively manage the heat inside the battery using cooling systems. These may include methods such as liquid cooling systems, air blast systems, or thermoelectric cooling. Passive cooling methods, on the other hand, aim to dissipate heat by using the thermal properties of the environment around the battery. These methods include heat dissipation plates, thermal interface materials, and phase change materials. This paper presents a brief review of phase change materials (PCM) – based BTMS. The importance of thermal management, the techniques and strategies used, its advantages and challenges are discussed and information is given about research and developments in BTM. In addition, the performances of different composite phase change materials (CPCM) on BTMS are highlighted and recommendations for future work were presented.</p

Multi-objective optimization of geometrical parameters of dimples on a dimpled heat exchanger tube by Taguchi based Grey relation analysis and response surface method

Taguchi based grey relation analysis (GRA) is performed on the numerical analysis of the dimpled heat exchanger tube for considering various dimple parameters. Dimple diameter (D-d) (3-7 mm), dimple pitch length (PL) (10-30 mm) and dimple height (H) (1.0-1.4 mm) are considered to achieve the highest convective heat transfer coefficient (h) and the lowest pressure drop (Delta P). The analyses are conducted under flow condition that is Reynolds number of 3000. The single-objective optimization is performed by Taguchi analysis, while GRA is used for the multi-objective optimization. Experimental plan is created according to L-25 orthogonal array given by Taguchi method. The relatively contribution levels of the parameters on the h and the Delta P are also figure out. Validation of the optimization methodology is ensured by performing a confirmation test. It is resulted that the PL. has higher influence on the both h and the Delta P followed by H and D-d in the decreasing order. Dimpled tube configuration having D-d = 7 mm, PL = 30 mm and H = 1.0 mm is found as the optimum configuration giving the highest the h and the lowest Delta P, simultaneously

Optimization of process parameters in terms of stabilization and thermal conductivity on water based TiO2 nanofluid preparation by using Taguchi method and Grey relation analysis

This paper presents an optimization of the water based TiO2nanofluid preparation process for thermal conductivity and zeta potential byusing Taguchi method for single-objective and Grey relation analyses for multi-objectiveoptimization. Stirring time, sonication time, mass ratio of surfactant toparticle and sonication power are selected as optimization factors to obtainhigher thermal conductivity and zeta potential. Sixteen different nanofluidsamples having various preparation parameters are determined and preparedwithin the scope of the Taguchi method. The thermal conductivity and the zetapotential of the samples are measured under constant temperature of 20℃. &nbsp;The contribution levels of the consideredparameters on the thermal conductivity and the zeta potential are respectivelyordered as the surfactant to particle ratio, the sonication time, thesonication power and the stirring time, by using analysis of variance (ANOVA).A confirmation test is carried out with optimized parameters and also ensuredthe confidence of the method.</p

An experimental study on heat transfer enhancement and flow characteristics of a tube with plain, perforated and dimpled twisted tape inserts

© 2020 Elsevier Masson SASIn order to increase the performance of a heat exchanger flowing ethylene glycol (EG) and water (W) mixtures, the effects of different twisted tapes on heat transfer and flow characteristics in a heat exchanger tube is experimentally investigated. Material of the twisted tapes and the tube is selected as stainless steel. Three different volumetric ratios of EG and W mixtures are used with the volumetric ratio of (0:100), (20:80) and (40:60). The twisted tapes having twist ratio of 5.88 are perforated and dimpled with pitch ratio of (Pp/y and Pd/y) of 0.25, 0.5 and 1.0. The experiments are conducted under constant heat flux and Reynold number ranging from 5217 to 22,754. The experiments for both the smooth tube and the typical twisted tape inserted tube are validated with the literature. The results indicated that the use of twisted tape inserts enhances the heat transfer performance. Experimental results revealed that novelty dimpled twisted tape insert provides higher heat transfer performance than the others. Adding the ethylene glycol on pure water has not major role on increase in the friction factor. As the amount of ethylene glycol in the mixture increases, thermo hydraulic performance decreases. The best thermo-hydraulic performance results are obtained as 1.42, 1.17 and 1.05 for dimpled twisted tape (Pd/y = 0.25) inserted tube at the lowest Reynolds numbers for the fluids which are (0:100), (20:80) and (40:60), respectively