rostam akbari kangarluei

Due to the importance of using nanofluids in heat pipes and not providing a report on the use of nanofluids in inner groove pulsating heat pipe (IGPHP), In this research, the thermal performance of IGPHP investigated using water- MWCNT (Multi-walled carbon nanotube) nanofluid as a working fluid. Experiments were performed on the optimal filling ratio (60%) and the input heat range of 50-300W in the vertical position in four volume fractions of 0.05, 0.1, 0.2, 0.4% with MWCNT nanofluid. The results showed that the lowest thermal resistance was obtained in the volume fraction of 0.1% and then increasing the concentration of nanofluid increases the thermal resistance of IGOHP, which seems to be the main reason for increasing the viscosity of nanofluid. The results showed that the use of MWCNT 0.1% nanofluid reduced the thermal resistance about 11% and increased the effective thermal conductivity about 12%.The results showed that the fluctuations in nanofluids started earlier than distilled water and the best performance occurred at higher input heat, which can be attributed to the large number of continuous fluctuations.

In this study, the thermal performance of inner groove oscillating heat pipes (IGOHP) with deionized water as a working fluid has been experimentally investigated. The results showed that in the filling ratio, 60% of the IGOHP has the lowest thermal resistance and the highest thermal conductivity. Then at the best filling ratio (60%) the IGOHP was investigated at different heating powers and also at different inclination angles. The achieved results indicated that in heating power of less than about 75 watts in 70° and 90°, thermal resistance is higher than angles of 5°, 15° and 30°, and among them, the angle of 15° had the lowest thermal resistance, but in heating power of more than 100 watts The performance of the IGOHP at 90° was better than the other angles, Also, the start-up of the IGOHP at an inclination angle of 15° occurred earlier than the vertical position. In this research more remarkable result is that at heating power above 200 watts, the thermal resistance of the IGOHP at an angle 15° is approximately equal to the angle of 90°, which in turn is a point for the IGOHP, which can promise to solve the problem of oscillating heat pipes at angles close to the horizon.

Pulsating heat pipes (PHPs) are one of the devices that can transfer a lot of heat while being simple and inexpensive. in industrial applications one of the major weaknesses of PHPs is their poor performance at angles close to the horizon. Previous studies have mostly been at 90, 60, 30, and 0 degree angles and have reported the weakness of PHPs in the 30 to zero angle range, but detailed studies has not been performed in this range. Therefore, the main purpose of this study is to experimentally investigate the performance of PHP at angles of deviation close to the horizon and to provide a more accurate critical inclination angle. the performance of PHPs was evaluated for the best filling percentage (60%) at different angles 0 to 90 degrees. the results showed that by reducing the PHP angle from 90 degrees to 15 degrees, the difference in thermal resistance for different heat input powers was very small, but this difference increased from angle of 10 to 0 degrees. Further studies showed that the percentage of difference in thermal resistance between angles 15, 10 and 5 with the average value of thermal resistance is 3%, 12% and 36%, respectively. Thus, it was found that the main weakness of pulsating heat pipes is from an angle of about 10 to 0 degrees.

This research deals with heat and mass transfer in biscuit industrial baking ovens. In these ovens, heat reaches biscuits indirectly by radiation, convection and conduction. The method for numerical solution is that we first provide the related equations, then they are discretized by finite difference method (FDM), and finally, after encoding and writing a program for the computer, we run it. The Obtained results indicate that biscuit heat absorption occurs 69 % through radiation, 28% convection and 3 % conduction. This percent of conduction depends on the type of band conveyor. Baking time depends on temperature of the baking chamber. For example, it takes 7 minutes for biscuits to reach 4% of moisture in 2000C.By increasing temperature of the baking chamber, the cooking time is decreased. Based on obtained results, there is a balance between heat and mass transfer rate. Results obtained from solving the equations indicates that maximum temperature of biscuits reaches 1500C and the highest moisture of baking chamber is almost at the middle of the oven. Vapors generated by this procedure are sent out by several fans, installed inside the baking chamber at the same distance. Simulated data of heat and mass transfer equations are in good agreement with experimental results. Obtained results can be used to control baking time and to production good quality for biscuits.