RICERCA ITALIANA     

HEAT TRANSFER IN MICRODEVICES: EXPERIMENTAL AND THEORETICAL INVESTIGATIONS FOR INNOVATIVE SOLUTIONS

Università degli Studi di Parma

Abstract

The proposed research project aims at analyzing the transport phenomena in single-phase and two-phase flows, in minichannels and microchannels having an equivalent diameter less than 4 mm. The goal is the determination of correlations needed for the correct design and sizing of micro-components in microfluidics. The present project is to be considered the natural carrying on and completion of the previous PRIN projects 2003 (Heat Transfer and Fluid Flow in Single-phase and two-phase flows in microchannels) and 2005 (Technological Applications of Microfluidics).
The research will have a spread technological spin-off related to the best understanding of the influence of the microscale effects on the heat transfer phenomena for single-phase and two-phase flows.
The technological impact of the proposed research will be addressed to enhance the energy efficiency and the thermal features of the microfluidic components such as:

• Fluidic microactuators for active control of aerodynamic flows;
• Vacuum generators for extracting biological samples;
• Mass flow and temperature micro-sensors, pressure gauges;
• Micro heat-exchangers for the cooling of electronic components or for chemical applications;
• Micropumps and microsystems for mixing or separation for local gas analysis;
• Mass spectrometers;
• Vacuum and dosing valves.

It is interesting to observe that in 2005 the gas sensor market, a key >>>

Principal Investigator

Marco Spiga Università degli Studi di PARMA

Research Objectives

Microfluidics, involving fluid-dynamics and heat transfer in microchannels, is a paramount topic for scientists and technicians. This is proved by the many papers published in this area, by the birth of several new International Journals (since Microscale Thermophysical Engineering in 1998, to Microfluids & Nanofluids in 2004), by several International Conferences (since Int. Conference on Heat Transfer and Transport Phenomena in Microscale, Banff 2000, to the fifth edition of Int. Conference on Microchannels and Minichannels which will be held in Puebla, in June 2007).
In this last decade, the papers appeared in literature highlights how the classical correlations used in macro-scale to evaluate the pressure drops and the convective heat transfer coefficients can predict values well different from those obtained experimentally. The reason for these discrepancies can be explained, because the miniaturization is responsible for scale-effects which imply the correction of classical models or the proposal of new models to represent the fluid-mechanics and heat transfer in isothermal and non-isothermal flows. The continuum flow theory, based on the Navier-Stokes and energy equations with no-slip boundary conditions for velocity and temperature, must be revised.
The research work developed during the past PRIN grants has been devoted to clarify how and when the micro scale-effects and the micro-effects play a significant role on the transport phenomena in >>>

First Results

The proposed research will have a spread technological spin-off related to the improvement of the understanding of the role played by the microscale on the heat transfer phenomena for single-phase and two phase flows.
The main expected results from this research project can be summarized as follows:

1. Analysis of the heat transfer characteristics of nanofluids (pure liquids with suspended metallic nanoparticles) in order to individuate new and more efficient cooling fluids. This will enable to build more compact microfluidic systems able to evacuate large values of the heat power. The research for new enhanced cooling fluids is an extremely promising field having an immediate technological impact and this research could carry to interesting patents in this field.

2. Development of specific numerical codes for the CFD design of micro-exchangers and for the sizing of the thermal control systems for microdevices.

3. Set-up of new theoretical models for the analysis of the fluid-wall interaction in microchannels of complex geometry in the case of internal rarefied flows. The setting up of these models will improve the predicting capability of the classical models validated only for simple geometries extending their use to the real geometries commonly met in the real technological applications. The use of these models within commercial numerical codes will improve the analysis of the thermal and fluid dynamic aspects of >>>

Timescale

24 months

National and international background

In these last years, the study of fluid dynamics and heat transfer in miniaturized ducts have attracted the attention of several research centres and industries all over the world. The reduced dimensions of the components in microfluidics, equipped with ducts having equivalent diameters less than 1 mm, heighten the scale effects and the micro effects at stake in transport phenomena, introducing essential discrepancies in the heat transfer behaviour.
The subjects of microfluidics has been shared by the research group in the previous two PRIN Projects.
The work carried out in the frame of the PRIN03 and PRIN05 by the
research Units (the same participating in this last project) has conducted to an accurate theoretical and experimental investigation about the main
scale and micro-effects, aimed at singling out correlations and models useful for the correct design of components in microfluidics.
The financial aids have permitted to set up new university laboratories devoted to the study of microfluidics (Bologna: Laboratory of Microfluidics at the DIENCA Department, Bergamo: Laboratory of Microfluidics and Interfaces at the Department of Engineering). These Laboratories arose and quickly developed from the effective collaboration with other research Laboratory (not university), such as the Laboratory of Thermofluid-Dynamics of ENEA Casaccia (Rome), directed by Dr. Gian Piero Celata, who was already greatly involved in the PRIN03 and PRIN05 >>>