جستجوی مقالات مرتبط با کلیدواژه « pulsating heat pipe » در نشریات گروه « مکانیک »

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.

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.

In this work، the performance of a flat plate solar collector operating in conjunction with a closed-loop pulsating heat pipe (CLPHP) is experimentally investigated. All the experiments are carried out at the Yazd، Iran. The experimental setup consists of a flat plate solar collector، pulsating heat pipe and a tank. The evaporator of the pulsating heat pipe is located inside the flat plate collector. In order to investigate the effect of the evaporator length on the efficiency of the system، three collectors are manufactured، which are different in the lengths of their evaporating section. Moreover، the effects of filling ratio of the pulsating heat pipe، inclination angle and flow rate are investigated for each collector separately. Although the increment in length of the evaporator negatively affects the convectional heat transfer، results do not show remarkable deterioration in the performance of flat plate solar collector. The optimum value for filling ratio of the pulsating heat pipe in all of three devices is measured as 30%، regardless of evaporator length. Finally، varying the inclination angle demonstrated that at angles between 0° and 20° degrees، the heat pipes exhibit unfavorable performance، while for angles between 30° and 50° degrees، the performances are favorable and almost similar. At the angle of 60 degrees، the performance is reduced due to excessive decrease in solar radiation.