The moisture sorption isotherms of some fruits namely pear and quince were determined at 15, 30, 45 and 60oC over a range of water activity from 0.110 to 0.920 using the standard, static-gravimetric method. The experimental sorption data were fitted with generated three-parameter sorption isotherm models on Mitrevski et al., and the referent Anderson model known in the scientific and engineering literature as Guggenheim-Anderson-de Boer (GAB) model. In order to find which models give the best results, large number of numerical experiments was performed. After that, several statistical criteria for estimation and selection of the best sorption isotherm model was used. The performed statistical analysis shows that the generated three-parameter model from Mitrevski et al. gave the best fit to the sorption data of pear and quince than the referent three-parameter Anderson model. Keywords: Sorption isotherms Pear Quince Statistical criteria

The novel segment electric in-line process electric heaters heater designed to heat various fluids analyzed in this work. The complete electric heater consists of several hollow cylindrical segment heating elements. The segment heating elements can vary positioned in relation to the fluid flow. The total power of the segment process heater is equal to the sum of the power of all heating segments and is 0.756kW. Volumetric air flow variations in the amount of 0.001m3s-1, 0.002m3s-1 and 0.003m3s-1. The heating elements are positioned in the three combinations in relation to the direction of the fluid flow. The comparative numeric analysis, conducted for this work, has the goal to determine the influence of the arrangement of segment heaters on the overall energy efficiency of the segment electric heater. In order to verify the results of the numeric simulations carried out and experimental investigations of the segment electric heater. Keywords: In-line heater Energy efficiency Segment elements Fluid flow, Convective heating

In this study, heat transfer and fluid flow characteristics of Ag-MgO/water hybrid nanofluid flow through a pipe were numerically investigated under turbulent regime at identical Reynolds number, velocity and pumping power. To model the flow, the standard k turbulence model was used. In the analyses, Reynolds number was in the range from Re=10000 to Re=100000 and velocity ranged from V=0.3 m/s to V=3.0 m/s. As a result, it was found that the enhancements in convective heat transfer coefficient were obtained to be 23.72% for identical Reynolds number, 6.27% for identical velocity and 0.44% for identical pumping power. Nanofluids had higher velocities compared to their base fluid to be able to compare them at identical Reynolds number. It was found that this velocity differences can already cause a convective heat transfer enhancement of 16.29% without nanoparticle addition. Nanofluids have higher performance evaluation criteria than unity at identical Reynolds number while they have lower values than unity at identical velocity and pumping power. It can be concluded that the results obtained for identical Reynolds number are extremely optimistic and not realistic. Nanofluids should be examined at identical velocity or pumping power for a fair comparison. Keywords: Entropy generation Heat convection Heat transfer enhancement Nanofluid Turbulence

In this numerical study, heat transfer characteristics and hydrodynamical analysis have been performed for a circular tube inserted with twisted tape, which has different twisted pitch ratios (TPR=0, 50, 100, and 200). As a working fluid Al2O3/water nanofluid is used which has different volumetric concentrations (0.0≤φ≤3.0 vol. %). The numerical analysis has been carried out under the constant wall heat flux (q′′) of 4357 W/m2 for laminar flow ranging the Reynolds (Re) number from 1000 to 2000. According to numerical results, the highest average Nusselt number (Nu) and average Darcy friction factor (ff) have realized in twisted pitch ratio (TPR) 50. The reason is that when the twisted pitch ratio gradually decreases, stronger secondary flows and a higher velocity can be obtained. When compared with water, the highest Nu for TPR=50 has been obtained at φ=3.0 vol. % concentration as 61.15%. Also, when compared with TPR=0, the highest thermal performance enhancement (TPE) was realized at φ=3.0 vol. % concentration and Re=2000 conditions as 61.15% for TPR=50. Keywords: CFD Convective heat transfer Laminar flow Al2O3/water Twisted tape

The main purpose of this study is to investigate the thermal efficiency of a Two-Phase Closed Thermosyphon (TPCT). For this purpose, initially, an experimental study was performed, then to predict the other experimental conditions ANN model which has used a wide range of thermal engineering systems was developed. A vertical copper pipe charged with different working fluids as pure water, ethanol, and ethylene glycol were used for TPCT. Impact of the various parameter such as heating power input, inclination angle, cooling water flow rate and working fluid type on the TPCT efficiency are examined. It is found that the increase in the inclination angle increased the TPCT efficiency while the increase in heating power input decreased efficiency. Regression analysis was applied to examine the performance of ANN between estimated and experimental data. The Mean Absolute Percentage Error (MAPE) was found to be less than 1.3 % for the training set and 3.1% for the test data set. The ANN predictions yield R2 in the range of 0.9998 for the training set and 0.9989 for the test data set. The obtained results from the experimental study and ANN were found in good agreement, and it is also concluded that from the study the ANN is a useful tool to estimate such thermal engineering problems. Keywords: Thermal efficiency Heat pipe Two-phase closed thermosyphon ANN