Advances in heat and mass transfer in gas-based microscale processes
The EU-funded MIGRATE project addressed current challenges to innovation facing European industry with regard to heat and mass transfer in gas-based microscale processes. This included modelling of heat transfer processes and devices, and development and characterisation of sensors and measurement systems for heat transfer in gas flows as well as thermally driven micro gas separators for microscale devices for improved heat recovery. Developing compact micro gas analysers requires a comprehensive understanding of the unsteady thermal behaviour of the gas flow with non-negligible compressibility effects, as well as effects associated with adsorption/desorption and longitudinal and transversal heat transfer. Integrated sensors are also needed to provide rapid feedback loops for the optimised control of processes, leading to higher thermal efficiency and less demand for resources.
New approaches to modelling
Researchers therefore developed several new modelling methodologies and precise descriptions of gas micro flow heat transfer in miniaturised devises, including gas-liquid contacting and phase transition. They also designed several measurement methods and a miniaturised wireless pressure sensor with increased range and miniaturised temperature and heat flux sensor for gas flows based on thermochromic particles. The wireless pressure sensor’s range was from a high vacuum to elevated pressure, a range normally only seen when using several sensors in combination. In addition, MIGRATE built different types of ultraviolet optical sensors for the quantification of volatile organic compounds (VOCs). Several sensor systems for VOCs based on photoelectric effect, photo ionisation effects in liquids and gas-liquid contacting were developed and tested. “This is important for future environmental analysis, since the EU has drastically reduced the permissible limits allowed in air quality sampling,” says project coordinator Jürgen Brandner. In addition, the project created or improved upon mathematical models for describing heat transfer, gas-liquid contacting and phase transition that are now ready for use. “In addition, a reduced order model for heat transfer enhancement and perturbation of flows in highly efficient gas heat exchangers has been developed and successfully applied. The corresponding heat exchanger devices have been built and tested for high-temperature gas turbines, which might be useful for future energy applications,” Brandner explains.
Increased knowledge
MIGRATE provided a deeper understanding of heat transfer performance at the microscale and developed and characterised high-performance gas-to-gas heat exchanger devices for application in decentralised energy applications and energy harvesting from waste heat, among others. In addition, scientists will benefit from improvements in modelling and new simulation codes plus new designs for microfluidic systems and devices. Application of the environmental sensors developed by MIGRATE will also help to monitor VOCs, thereby benefitting society as a whole. “Miniaturised devices will play a key role in future industrial applications and transport systems as well as in the redesign of existing processes, ranging from industrial technologies to personal equipment,” Brandner points out. Finally, the initiative’s combination of university research, SME and world-leading industrial stakeholders will make a significant contribution to knowledge about microscale gas flow heat transfer problems and industrial applications of highly efficient miniaturised devices. The research was undertaken with the support of the Marie Skłodowska-Curie programme.
Keywords
MIGRATE, heat transfer, miniaturised, mass transfer, volatile organic compounds, heat transfer, pressure sensor, thermochromic, micro gas analyser
