tailieunhanh - Heat Transfer Theoretical Analysis Experimental Investigations Systems Part 6

Tham khảo tài liệu 'heat transfer theoretical analysis experimental investigations systems part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 190 Heat T ransfer - Theoretical Analysis Experimental Investigations and Industrial Systems of ps the calculated values of the minimum velocity of the bubble wall the peak temperature and pressure are excellent agreement with the observed ones for the sonoluminescing xenon bubble in sulfuric acid solutions Kim et al. 2006 . Furthermore the calculated bubble radius-time curve displays alternating pattern of bubble motion which is apparently due to the heat transfer for the sonoluminescing xenon bubble as observed in experiment Hopkins et al. 2005 . The bubble dynamics model presented in this study has also revealed that the sonoluminescence for an air bubble in water solution occurs due to the increase and subsequent decrease in the bubble wall acceleration which induces pressure non-uniformity for the gas inside the bubble during ns range near the collapse point Kwak and Na 1996 . The calculated sonoluminescence pulse width from the instantaneous gas temperature for air bubble is in good agreement with the observed value of 150 ps Byun et al. 2005 . Due to enormous heat transfer the gas temperature inside the sonoluminescing air bubble at the collapse point is about 20000 40000 K instead of 107 K Moss et al. 1994 which is estimated to be in the adiabatic case. Molecular dynamics MD simulation results for the sonoluminescing xenon bubble were compared to the theoretical predictions and observed results Kim et al. 2007 Kim et al. 2008 . 2. Temperature profile in thermal boundary layer A sketch of the bubble model employed is given in which shows a spherical bubble in liquid temperature Teo and liquid pressure P . Heat transfer is assumed to occur through the thermal boundary layer of thickness S t . The temperature profile in this layer is assumed to be quadratic Theofanous et al. 1969 . T-T . 1- Ỉ 2 1 where Tbi is the temperature at the bubble wall and T is the ambient temperature in Eq. 1 . The parameter in Eq. 1 is given as r - Rb S and Rb t is the .