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dr. S. Vanapalli (Srini)

Associate Professor

About Me

Srinivas Vanapalli’s  academic roots are from the Indian Institute of Technology, Madras with a bachelor degree in Mechanical Engineering. He later received an electrical engineering  master’s degree (cum laude) from the University of Twente. He received his PhD title for 'High frequency operation and miniaturization aspects of cryocoolers' at UT, a major part of this work is carried out at National Institute of Standards and Technology, Boulder, USA.

Srini has a mix of industrial and academic experience and has worked so far in three continents. His research interest is cryogenics where disciplines thermodynamics, material sciences, fluid, and heat transfer meet. He received the 2019 Mulholland award for excellence in cryogenic engineering which is given to recognize significant achievement in a particular areas of cryogenics.

Srini leads the Applied Thermal Sciences lab within the Energy Materials and Systems cluster where his team explores fundamentals and applications of thermal sciences in both space and time domains. The core competence of his group is heat and mass transfer phenomena in the cryogenic temperature range from 200 K to 4 K.  His approach combines formulation of conceptual models, experiments and numeric. The topics of his research are problem-driven and his team seek to solve grand societal challenges related to energy and life sciences.

Srini is successful in obtaining grant income from various sources, both government and industry. So far he generated 2.9 million euro income since 2015.

 

For more info about Srinivas Vanapalli on the 'Featured Scientists' page, click below:

 


 

Expertise

Engineering & Materials Science
Cooling
Cryogenics
Liquid Nitrogen
Chemistry
Cooling
Cryogenics
Physics & Astronomy
Coolers
Cooling
Tubes

Research

RESEARCH INTERESTS

  • Thermodynamics
  • Heat transfer, Thermal properties
  • Evaporation
  • Cryogenic technology & Cryogenics, Liquid nitrogen cooling
  • Cryo-transmission electron microscopy, sample preparation
  • Cryoablation 

RESEARCH HIGHLIGHTS

please see the home page of Applied Thermal Sciences lab

 

research highlights before 2015

Multi-bilayer thermal storage
A multi-bilayer thermal storage system, consisting of alternate layers of phase change material and thermal insulation decreases the overall thermal diffusivity. Multi-bilayers are experimentally proven to have more than 200 % increase in hold time for a three bilayer system compared to a single bilayer system, considering the same weight for both systems. 

Vanapalli, S. & van der Leij, T., WO 2016/162451, International patent, October 13, 2016.

Compact additive manufactured thermal device
A compact flat-panel gas-gap heat switch is developed with additive manufacturing. The novelty in this approach is that several components can be produced simultaneously (e.g. fluidic interconnects and heat sink), and allows three dimensional flexibility in the design of the outer structure to tailor the device for any intended application (either flat, cylindrical or any other shape). It has clear potential for quick adoption by stringent markets, because of its low footprint and mass, and without moving parts or welds.

Vanapalli, S.  et al. Cryogenics 78, 2016; 
Krielaart, M.A.R., Vermeer, C.H., Vanapalli, S., Review of Scientific Instruments 86, 2015.

Cryogenic optical microscopy
A tool to visualize the deposition and sublimation of impurities (water vapour) in a narrow slit of 1 micron depth at cryogenic temperature (around 150 K) is developed. A tailor made glass cryostat and a glass micro-machined Joule Thomson cold stage is used to study the heat and mass transfer process in the microchannels. For the first time, such visualization experiments are performed in the context of cryogenic coolers. The optical images, temperature recording and the mass flow data gives insight into the physical process that influence the (de-) sublimation process.

Phd thesis: Cao, H.S., University of twente, 2013;
Cao, H.S., Vanapalli, S.  et al., Applied Physics letters 103, (2013)

An apparatus to measure thermal conductivity of insulation panels at sub-ambient temperature
A single-sided guarded-plate apparatus has been developed to measure the thermal conductivity of insulation panels of sub-meter size at sub-ambient temperatures ranging from 250 to 300 K. This apparatus allows thermal conductivity measurements to be performed at large temperature differences simulating the actual operating conditions in an application and can accommodate panels of various thickness. The cold plate in the apparatus is cooled with a flow thermostat.

Vanapalli, S. et al. International Journal of Refrigeration 74, 2017.

Assessment model for nanofluids
Nanofluid is a suspension of nanoparticles in a carrier fluid. A simple thermal performance assessment model based on first principles is developed that can be used by industry to rapidly evaluate the thermal performance of a nanofluid in comparison to its base or carrier liquid in convective systems. The model takes into consideration a number of key properties of the base liquid and the nanoparticles dispersed including changes in viscosity, thermal conductivity, specific capacity and concentration of the nanoparticles, density as well as the flow rate, geometry and flow conditions. Hence, the model can be used by industry to optimize both the formulation of the nanofluid and geometry of the heat transfer unit deployed to harness the benefits.

Vanapalli, S. & ter Brake, H.J.M., International journal of heat and mass transfer 64, 2013.
Vanapalli, S. et al. International Journal of Refrigeration 74, 2017.

Micro cryogenic Joule Thomson cryocoolers
Using the state-of-the-art glass microsystems technology (isotropic chemical etching and bonding wafers), a two stage Joule Thomson cold stage (PhD work of H.S.Cao) with a temperature of 30 K is developed, and have demonstrated the application of this cooler by attaining superconductivity of a thin film device.

Cao, H.S., et al., Int. J. Refrigeration, 2016.
Cao, H.S., et al., Journal of Micromechanics and Microengineering, 23, 2013.
Cao, H.S., et al., Cryogenics, 52, 2012.

Thermoacoustic heat pump
A system for a dwelling, which is based on thermoacoustics and can be used to switch the role between a heat pump and a cooler as the need arises, has been developed. The system uses an environment friendly working medium and was shown to have a reasonably good performance. This work is performed at the Energy research Center of the Netherlands.

Vanapalli, S., Tijani, M.E.H., Spoelstra, S., ASME 2010 Summer meeting.

High frequency pulse tube cryocooler
A pulse tube cryocooler operating at 120 Hz with 3.5 MPa average pressure achieved a no-load temperature of about 49.9 K and a cooldown time to 80 K of 5.5 min. The net refrigeration power at 80 K was 3.35 W with an efficiency of 19.7% of Carnot when referred to input pressure-volume (PV or acoustic) power. Such low temperatures have not been previously achieved for operating frequencies above 100 Hz. The high frequency operation leads to reduced cryocooler volume for a given refrigeration power, which is important to many applications.

Vanapalli, S., Lewis, M., Gan, Z., Radebaugh, R.,Applied Physics Letters 90, 2007.

Publications

Recent

UT Research Information System

Education

What defines me as a teacher?

  • Experiment with better ways to achieve success
  • Value the students and respect them.
  • Inspire students by drawing parallels between the subject matter and students everyday experiences. Also walking through several examples.
  • Belief in mentoring students and showing them the path to learn themselves.
  • Provide thought provoking examples (not just a text book).

Affiliated Study Programmes

Bachelor

Master

Courses Academic Year  2022/2023

Courses in the current academic year are added at the moment they are finalised in the Osiris system. Therefore it is possible that the list is not yet complete for the whole academic year.
 

Courses Academic Year  2021/2022

Projects

My research is supported by national, european funding agencies and industry. 

Funding entities: NWO-TTW, EUreka, TKI-HTSM, TKI-Urban Energy, ZonMW, ESA, Air Liquide

Project  Funding source Amount
(Euros)
Period Role of the PI
CETFlow EU 110k 2019-2022 Co-applicant
CryoON NWO-TTW 810k 2016-2021 Main applicant
CryoSponge TKI-HTSM 660k 2019-2023 Only applicant
Cooling Leidenfrost TKI-HTSM 770k 2020-2024 Only applicant
High frequency Stirling  TKI-Urban energy 186k 2019-2020 Only applicant
Smartbox Air Liquide 200k 2019-2021 Only applicant
Cryopsy ZonMW/DBT 25k 2018-2020 Main applicant
Internal grant: University of Twente SBE/UT 40k 2018-2019 Only applicant
Faculty of Science and Technology, University of Twente S&T/UT 160k 2019 Package to support tenure track

 

various industrial consultancy activities.

Media

What drives me as a scientist is the exciting wealth of knowledge and surprises I come across in my research, either in the lab or in discussions with my team. We built a little cryogenic fluids playground and often me and my students try things out of curiosity, very often transforming into serious multi-year projects. I believe in sharing this curiosity with the general public and to high-school students, with a hope to ignite the STEM flame in them. My outreach efforts were recognized recently by the MESA+ Dave Blank Outreach Award

In the press

News feature in Physicsworld (IOP publishing)

09 July 2020: Why insulated metals cool down faster than their bare counterparts

https://physicsworld.com/a/why-insulated-metals-cool-down-faster-than-their-bare-counterparts/

30 December 2019: Study of liquid-nitrogen droplets gives new insight into cryogenic spray-cooling

https://physicsworld.com/a/study-of-liquid-nitrogen-droplets-gives-new-insight-into-cryogenic-spray-cooling/

 

17 December 2019 UToday: Freeze!

https://www.utoday.nl/science/67723/freeze

August and October 2019 COLDFACTS issue (https://cryogenicsociety.org/cold_facts/)


News on utwente.nl

Contact Details

Visiting Address

University of Twente
Faculty of Science and Technology
Carré (building no. 15), room C2049
Hallenweg 23
7522NH  Enschede
The Netherlands

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Mailing Address

University of Twente
Faculty of Science and Technology
Carré  C2049
P.O. Box 217
7500 AE Enschede
The Netherlands

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