Analysis of bubble translation during transient flash evaporation

نویسنده

  • SRIDHAR GOPALAKRISHNA
چکیده

An analysis was performed of the rise characteristics of bubbles, which are also growing, in a pressure Iield which is decreasing exponentially with time. The bubble rise and growth occur due to flash evaporation caused by reducing the pressure in the vapor space above a pool of liquid. Basset’s bubble momentum equation was modified to include the effects of the generated pressure wave, and to include bubble growth. The solution of the differential equation was obtained for three different expressions for the bubbb drag, for pressure ratios of 0.1-0.9, Jakob numbers of 5-l 13, Weber numbers of O-0.16, and time constants of the pressure transient down to 5 ms. Results indicate &hat different bubble drag expressions give bubble velocities which differ by as much as 100%. The pressure term introduced by the authors has a negligible effect in the range of parameters considered here but becomes significant for very rapid depressurization rates, and the initial velocity of the bubble has little effect on the bubble’s subsequent rise velocity.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Rapid evaporation at the superheat limit

In an experimental investigation of the transient processes that occur when a single droplet of butane at the superheat limit vaporizes explosively, short-exposure photographs and fast-response pressure measurements have been used to construct a description of the complete explosion process. It is observed that only a single bubble forms within the drop during each explosion, and that the growt...

متن کامل

Exploration of Impinging Water Spray Heat Transfer at System Pressures near the Triple Point

The heat transfer of a water spray impinging upon a surface in a very low pressure environment is of interest to cooling of space vehicles during launch and re-entry, and to industrial processes where flash evaporation occurs. At very low pressure, the process occurs near the triple point of water, and there exists a transient multiphase transport problem of ice, water and water vapor. At the i...

متن کامل

The importance of liquid evaporation on rectified diffusion processes

This paper unveils the basic mechanisms underlying rectified diffusion processes. The exact solution of the radial transport of species in both phases, gas and liquid, turns to be crucial to accurately predict the growthrate in the context of lithotripsy. The Direct Numerical Simulation of the temporal evolution of an spherical bubble is used to gain new insight on the effect of two phenomena: ...

متن کامل

Scale effects on flow boiling heat transfer in microchannels: A fundamental perspective

Flow boiling in microchannels has received considerable attention from researchers worldwide in the last decade. A scaling analysis is presented to identify the relative effects of different forces on the boiling process at microscale. Based on this scaling analysis, the flow pattern transitions and stability for flow boiling of water and FC-77 are evaluated. From the insight gained through the...

متن کامل

Analysis of pool boiling heat transfer: effect of bubbles sliding on the heating surface

Pool boiling on surfaces where sliding bubble mechanism plays an important role has been studied. The heat transfer phenomenon for such cases has been analysed. The model considers different mechanisms such as latent heat transfer due to microlayer evaporation, transient conduction due to thermal boundary layer reformation, natural convection and heat transfer due to the sliding bubbles. Both m...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2002