Mustafa Aktaş

Utilization of Fly Ash Nanofluids in Two-phase Closed Thermosyphon for Enhancing Heat Transfer

This study investigates how fly ash nanofluids affect the thermal performance of a two-phase closed thermosyphon at various states of operation. The utilization of nanofluids obtained from X2O3-type oxides, such as Al2O3, Fe2O3, or CuO, on the improvement of two-phase closed thermosyphon performance was reported in a number of studies in the literature. The present study experimentally demonstrated the effect of using a nanofluid obtained from fly ash comprised of various types of metal oxides in varying ratios on improving the performance of a two-phase closed thermosyphon. The fly ash was obtained from the flue gas that was captured in the cyclones of the Yatagan thermal power plant (Turkey). Triton X-100 (Dow Chemical Company) dispersant was used in the study to produce the 0.2% (wt) fly ash/water nanofluid via direct synthesis. A straight copper tube with an inner diameter of 13 mm, outer diameter of 15 mm, and length of 1 m was used as the two-phase closed thermosyphon. The nanofluid filled 33.3% (44.2 ml) of the volume ofthe two-phase closed thermosyphon. Three heating power levels (200, 300, and 400 W) were used in the experiments with three different flow rates of cooling water (5, 7.5, and 10 g/s) used in the condenser for cooling the system. A increase of 26.39% was achieved in the efficiency of the two-phase closed thermosyphon when 4% (wt) fly ash containing nanofluid was used to replace deionized water at a heat load of 200 W and with a cooling water flow rate of 5 g/s.

Experimental analysis and CFD simulation of infrared apricot dryer with heat recovery

ABSTRACT Drying is one of the easily accessible and the most widespread processing technologies that have been used since ancient times for preserving fruits. Drying is an energy-intensive and time-consuming process, so reducing energy demand is important. The main aim of this paper is to analyze the heat and mass transfer characteristics of product in the drying chamber and in addition to this, three-dimensional (3-D) computational fluid dynamic (CFD) simulation was performed. The analyses of heat and mass transfer were investigated theoretically and experimentally in infrared dryer (IRD). The dryer consists of air to air heat recovery unit and proportional temperature controller. Experiments were performed at 0.5 and 0.25 m/s air velocities and at 60 and 65°C apricot surface temperatures which were controlled by three thermocouples contacted on top side of the product. In order to use energy more effectively and improve the drying characteristics of apricot, analyses were performed under different drying conditions. Since the heat recovery unit has a key role in this system, the performance of this unit was investigated and recovered energy ratio was between 58 and 62%. The calculated moisture diffusivity values varied from 1.7 × 10−10 to 1.15 × 10−9 for apricot, and the highest value of average energy efficiency was obtained as 16.43% at 65°C temperature and 0.25 m/s air velocity. Theoretical and experimental results are in line with each other.

Testing of a Condensation-type Heat Pump System for Low-temperature Drying Applications

Abstract A closed-type water source heat pump dryer integrated with a drying programme (DP) was designed and tested. The DP was developed using psychometric conditions of desired drying air and thermodynamic balance of heat pump. A drying algorithm was developed according to the technical specification of the dryer. Drying air temperature, relative humidity and drying air volumetric flow rate were entered from a programmable logic controller (PLC) screen. In this study, the drying of mint leaves was examined. Mint leaves were dried at different temperatures (35°C, 40°C and 45°C) and at different volumetric flow rates 300 m3/h for a velocity of 0.75 m/s and 600 m3/h for a velocity of 1.5 m/s in the PLC-controlled heat pump dryer. The relative humidity of the drying air entering the dryer chamber was kept between 13.88% and 6.81% and the two air dampers were controlled according to predetermined value. The coefficient of performance (COPhp

ENERGY AND EXERGY ANALYSIS OF TIMBER DRYER ASSISTED HEAT PUMP

\rm CO{\rm P_{{\rm{hp}}}}

Modeling of a hazelnut dryer assisted heat pump by using artificial neural networks

) values obtained were between 3.81 and 2.29. The specific moisture extraction rate for the whole system (SMERws

Numerical simulation of the effects of plate separation and inclination on heat transfer in buoyancy driven open channels

\rm SME{\rm R_{{\rm{ws}}}}