Experimental and Numerical Characterization of Heat Transfer Behavior and Crown Propagation Dynamics Induced by Droplet Impingement

Jorge L. Alvarado, Ph.D.
Department of Engineering Technology and Industrial Distribution
Department of Mechanical Engineering (joint-appointment)
Texas A&M University, College Station, 77843, TX 

In this study, hydrodynamics and heat transfer characteristics of a liquid droplet train impinging on a pre-wetted solid surface have been investigated experimentally and numerically. Specifically, the effects of high Weber number, droplet impingement frequency, droplet diameter and droplet velocity on  liquid  film  hydrodynamics  and  heat  transfer  have  been  evaluated  using  state-of-the-art experimental instrumentation. Recently, crown propagation events were imaged using a high-speed camera system  given the  high  frequency  of droplet impingement.   The  high-frequency  droplet impingement process  was  also  simulated  numerically  using  CFD  software.  Crown  propagation dynamics  were evaluated  and  analyzed  experimentally  and  numerically.  As  a  result,  a  revised theoretical crown propagation model based on numerical results has been proposed, which takes into account the radial velocity distribution within the impinged liquid film at the moment of initial spot formation. The revised theoretical crown propagation model gives accurate predictions, which are in good agreement with the experimental results. Recently, the effects of double droplet streams on heat transfer and film hydrodynamics have been studied experimentally and computationally.  Results to date show that Weber number and droplet spacing are key parameters in the development of effective droplet impingement schemes for a host of applications.

Dr. Jorge Alvarado is an associate professor in the Department of Engineering Technology and Industrial Distribution at Texas A&M University (TAMU).  He holds a joint-appointment in the Department of Mechanical Engineering at TAMU.  He teaches courses in the areas of thermal  sciences, fluid  mechanics,  and  fluid  power.    Dr.  Alvarado’s  research  interests  are  in  the  areas  of nanotechnology, nano- and micro-scale heat transfer, electronic cooling, phase change materials, thermal storage, bio-fuel combustion, and energy conservation in buildings.  He received his BS degree in mechanical engineering (1991) from the University of Puerto Rico at Mayagu ez; MS (2000) and  PhD  (2004)  degrees  in  mechanical  engineering  from  the  University  of  Illinois  at Urbana-Champaign.

He has worked and collaborated with the U. S. Army Corps of Engineers, Office of Naval Research (ONR), Kobe University, and the University of Wisconsin at Madison, among others.  Recent research work involves enhanced condensation using hybrid surfaces with hydrophobic and hydrophilic properties, characterization of microencapsulated phase change material slurry and nanofluids as heat  transfer  fluids,  as  well  as  the  study  of  spray  and  droplet  impingement  cooling  using nanostructured surfaces. His publication record includes scholarly articles in journals such as Applied Physics Letters, International Journal of Heat and Mass Transfer, Journal of Heat Transfer and Numerical Heat Transfer among others.  He is a member of the American Society of Mechanical Engineers (ASME), American Society of Thermal and Fluid Engineers (ASTFE), and the American Physical Society (APS).