The pressure characteristics inside single loop oscillating heat pipe(OHP) having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed.Distilled water was used as working fluid inside the OH...The pressure characteristics inside single loop oscillating heat pipe(OHP) having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed.Distilled water was used as working fluid inside the OHP with different filling ratios of 40%,60% and 80% of total inside volume.Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency.And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60?96 °C.Piezoresistive absolute pressure sensor(Model-Kistler 4045A5) was used to take data.The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.展开更多
Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experimen...Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.展开更多
基金Project(2011-0009022) supported by Basic Science Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education,Science and Technology of Korea
文摘The pressure characteristics inside single loop oscillating heat pipe(OHP) having 4.5 mm inner diameter copper tube with the loop height of 440 mm were addressed.Distilled water was used as working fluid inside the OHP with different filling ratios of 40%,60% and 80% of total inside volume.Experimental results show that the thermal characteristics are significantly inter-related with pressure fluctuations as well as pressure frequency.And the pressure frequency also depends upon the evaporator temperature that is maintained in the range of 60?96 °C.Piezoresistive absolute pressure sensor(Model-Kistler 4045A5) was used to take data.The investigation shows that the filling ratio of 60% gives the highest inside pressure magnitude at maximum number of pressure frequency at any of set evaporator temperature and the lowest heat flow resistance is achieved at 60% filling ratio.
基金supported by Basic Science Research Program through the National Research Foundation of Korea (NRF)funded by the Ministry of Education, Science and Technology (No.2012-0004544)
文摘Nano fluid is considered to be a class of high efficient heat transfer fluid created by dispersing some special solid nanoparticles (normally less than 100 nm) in traditional heat transfer fluid. The present experiment was conducted aiming at investigating the forced heat transfer characteristics of aqueous copper (Cu) nanofluid at varying concentration of Cu nano-particles in different flow regimes (300<Re≤16 000). The forced convective heat transfer enhancement is available both in the laminar and turbulent flow with increasing the concentration. Especially, the enhancement rate increases dramatically in laminar flow regime, for instance, the heat transfer coefficient of Cu/water nanofluid increases by two times at around Re=2 000 compared with that of base fluid water, and averagely increases by 62% at 1% volume fraction. However, the heat transfer coefficient of Cu/water decreases sharply in the transition flow regime. Furthermore, it has the trend that the heat transfer coefficient displays worse with increasing the concentration.
