- Professor, Mechanical Engineering-Engineering Mechanics
- PhD, University of Minnesota
Professor Narain is a Fellow of the ASME, an Associate Editor of the Journal of Heat Transfer, and Director of the Energy-Thermo-Fluids area in his department. His current research areas deal with state-of-the-art experimental and computational techniques for single-phase and phase-change (flow-boiling and flow-condensation) flows, particularly those related to energy technologies such as thermal management and power generation applications. Dr. Narain’s research has received continuous funding from NSF or NASA since the year 2000. He is a PI or Co-PI on external grants totaling approximately $ 3 million (with about $1.85 million as PI). Dr. Narain has authored over 73 peer-reviewed articles. His recent research accomplishments have been highlighted through several keynote and invited lectures – including on national websites, such as by NSF in 2012 and by Research.Gov in 2013. He is very active in teaching and mentoring students (graduate and undergraduate), as well as in national-level professional service and international-level short courses. Dr. Narain has served on several government panels and on ASME committees: HTD-K8 (current Vice-chair and Chair-designate), HTD-K13, FED-Multi Phase Flow Committee, and AMD-Fluid Mechanics committee (Past Chair and Vice-Chair). Over the past twenty years, he has also been an active lead organizer as chairs of tracks, topics, or sessions for the conferences offered by ASME and other international organizations.
Current Research Interests
Long-term and current research deals with fundamentals and applications of phase-change flows for innovative millimeter-scale flow-boiler and flow-condenser operations discovered in our laboratory. Applications include addressing cooling requirements of next generation supercomputers, data centers, laser weapons, and many other new systems. The first innovative principle deals with these operations’ flow-control strategy. It involves setting up a controlled and passive recirculating vapor flow in a way that it results in annular liquid flows – of desired micrometer-scale thicknesses – over the entire heated/cooled surface of the devices. The second innovation imposes resonant pulsations on vapor and liquid flows in a way that large amplitude standing waves – with the help of enabling acoustics – form the annular flows' interface. As a result, when the troughs of these large amplitude standing interfacial waves come sufficiently close (within, say, 10 mm) to a wetting (or hydrophilic) boiling-surface, contact line flow-physics arise to create dynamic heat-flux enhancements that lead to desired time-averaged enhancements (by a factor of 4 – 20) over their corresponding steady non-pulsatile values.
For macro or cm-scale flow-boilers and condensers used in the energy sector, the research focuses on significant air-side heat-transfer enhancements without pressure-drop penalties. Innovative fins, dielectric barrier discharge (DBD) flows, humidity-controlled condensation and evaporation on the finned surfaces, etc. are being explored to propose breakthroughs in dry-cooling/dry-heating approaches for technological innovation of heat recovery steam generators (HRSGs), air-cooled condensers, etc. for next generation power plants. Some innovations for gravity-insensitive mode of HVAC operations (such as those for aircrafts or uses in zero/microgravity space environments) are among other possible applications.
The following existing and evolving tools support the above mentioned research: two modern state-of-the-art electronically-controlled flow-loops (with extensive electronic-sensing) for testing and developing innovative boiler and condenser operations (for mm-scale devices), testing and fabrication of 3-D printed innovative passive designs for air-heated/air-cooled fins (for significant reductions in gas-side thermal resistances encountered in the operation of industrial cm-scale devices), and synthesis of experimental results with our state-of-the-art scientific and engineering simulation tools (some of them are based on our own breakthrough algorithms).
Links of Interest
- MS, and Ph. D. students
- occasionally—post-docs, visiting faculty, consultants, and other faculty as collaborators
Current research team builds on works of earlier teams. Both current and past research teams, and their contributions, are described in Dr. Narain’s full CV.
Area of Expertise
- Fluid Mechanics (Theory, Experiments, and CFD). Example: thin-film (mm to mm-scale) flows, stability, pulsatile flows, larger (cm to m-scale) laminar/turbulent flows.
- Heat Transfer (Theory, Experiments, and Computations). Example: flow-condensation, flow-boiling, pulsatile flows, and contact-line flow-physics.
- System Design. Example: design of flow-loops with hardware fabrication (including components) and software (including flow-control, sensing, signal-processing, and DAQ), and development of new preliminary design approaches for thermal systems.
- Kivisalu, M. T., Gorgitrattanagul, P., and Narain, A., “Results for High Heat-Flux Flow Realizations in Innovative Operations of Milli-Meter Scale Condensers and Boilers.” International Journal of Heat and Mass Transfer, Vol. 75, 2014, pp. 381-398. Read More
- Ranga Prasad, H., Narain, A., Bhasme, S., Naik, R., “Shear Driven Suppressed Nucleation Annular Flow-boiling in Millimeter-scale Channels: Direct Numerical Solutions and Heat Transfer Correlations.” Submitted: International Journal of Transport Phenomena, 2016. Invited Paper. Accepted for publication. Submitted Nov 1, 2016. Read More
- Naik, R., Narain, A., Mitra, S., “Steady and Unsteady Simulations for Annular Internal Condensing Flows, Part I: Algorithm and its Accuracy.” Numerical Heat Transfer, Part B: Fundamentals., Vol. 69, No. 6, 2016, pp. 473-494. Read More
- Naik, R., Narain, A., “Steady and Unsteady Simulations for Annular Internal Condensing Flows, Part II: Instability and Flow Regime Transitions.” Numerical Heat Transfer, Part B: Fundamentals., Vol. 69, No. 6, 2016, pp. 495-510. Read More
- Narain, A., Ranga Prasad, H., and Koca, A.: “Internal Annular Flow-boiling and Flow-condensation: Context, Results, and Recommendations.” Handbook of Thermal Science and Engineering. Francis A. Kulacki. Springer. Invited. Submitted Nov 1, 2016. Read More
- Mitra, S., Narain, A., Naik, R., and Kulkarni, S. D., “A Quasi One-Dimensional Simulation Method and its Results for Steady Annular/Stratified Shear and Gravity Driven Condensing Flows.” International Journal of Heat and Mass Transfer, Vol. 54, No. 15, 2011, pp. 3761-3776. Read More
- Narain, A., Naik, R.R., Ravikumar, S., Bhasme, S.S., “Fundamental assessments and new enabling proposals for heat transfer correlations and flow regime maps for shear driven condensers in the annular/stratified regime.” Journal of Thermal Engineering, Vol. 1, No. 4, 2015, pp. 307-321. Read More
- Narain, A., Ajotikar, N., Kivisalu, M., Rice, A., Zhao, M. and Shankar, N., “Obtaining Time-Varying Flow-Rates for Pulsatile Gas Flows - with Assistance from Dynamic Pressure-Difference and Mean Mass Flow-Rate Measurements.” Journal of Fluids Engineering, Vol. 135, No. 4, 2013, pp. 041101-1 to -19. Read More