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Experimental Apparatus for the Study of micro Heat Exchangers with Inlet Temperatures between -200 and 200 °C and Elevated Pressures
This paper was presented at the 4th Micro and Nano Flows Conference (MNF2014), which was held at University College, London, UK. The conference was organised by Brunel University and supported by the Italian Union of Thermofluiddynamics, IPEM, the Process Intensification Network, the Institution of Mechanical Engineers, the Heat Transfer Society, HEXAG - the Heat Exchange Action Group, and the Energy Institute, ASME Press, LCN London Centre for Nanotechnology, UCL University College London, UCL Engineering, the International NanoScience Community, www.nanopaprika.eu.The current paper presents a test bench for micro-fabricated Recuperative Counter Flow Heat
Exchanger (RCFHE). The bench is suitable for up to 200 K difference between inlets temperatures and
operating pressures up to 32 MPa. The experimental setup allows controlling the physical state of the gas
(i.e. temperature, pressure and flow rate) at the RCFHE inlets. The bench has 5 controlled parameters and 5
more that are monitored and enables studying each of the hot and cold channels separately. We demonstrate
a steady supply of liquid nitrogen into the device for 10 minutes without thermal insulation of the specimen.
Another run is a steady state experiment with a temperature difference of about 20-30 K between inlets.
These show that the apparatus is capable of characterizing heat exchangers and serve as preliminary results
Microvalve-Based Tunability of Electrically Driven Ion Transport Through a Microfluidic System with Ion-Exchange Membrane
Microfluidic channels with embedded ion permselective medium under the
application of electric current are commonly used for electrokinetic processes
as on-chip ion concentration polarization (ICP) and bioparticle
preconcentration to enhance biosensing. Herein, we demonstrate the ability to
dynamically control the electrically driven ion transport by integrating
individually addressable microvalves. The microvalves are located along a main
microchannel that is uniformly coated with a thin layer of an ion-exchange
membrane (IEM). The interplay of ionic transport between the solution within
the microchannel and the thin IEM, under an applied electric current, can be
locally tuned by the deformation of the microvalve. This tunability provides a
robust and simple means of implementing new functionalities into lab-on-a-chip
devices, e.g., dynamic control over multiple ICP layers and their associated
preconcentrated molecule plugs, multiplex sensing, suppression of biofouling as
well as plug dispersion, while maintaining the well-known application of
microvalves as steric filtration
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