Advanced Microchannel Heat Exchangers
Why is this technology needed?
Energy conversion, recovery and generation often require high effectiveness heat exchangers. Functions can include recuperation, waste heat recovery, boiling a working fluid, condensation, evaporation in cooling systems and high flux heat removal. In many applications, emphasis is placed on small, light-weight and high-performance devices, especially if the overall systems using heat exchangers are meant for portability, must be air-lifted or for retro fitting existing systems where space constraints are dictated.
How does this technology address the need?
Microchannel heat transfer devices rely on process intensification afforded by the use of smaller fluid channels than are traditionally used, for example under 1 mm in characteristic diameter. For counter- and cross-flow heat exchangers, scaling rules can dictate a variety of performance features and pressure drop considerations. For example, if the cross-section area of a counter-flow heat exchanger is to remain constant, using smaller fluid channels results in a shorter device that uses less material (hence is lighter) and is more compact without a penalty in pressure drop. Other scaling rules do affect the pressure drop, and each case must be carefully considered for the approach to be used.
A listing of attributes for microchannel heat exchangers when used in a variety of applications include:
- Process Intensification (heat and mass transfer): Volume reduction factors of 5 to 10; weight reduction factors of 2 to 5.
- Low Pressure Drop: Constant or reduced pumping power for same process duty.
- Safety in Reactions: Low fluid inventory; fast quench, if combustion is present, low flame propagation.
- Good Reaction Control: Minimize undesirable side and back reactions; can process highly energetic reactions.
- Can be Gravity Insensitive: Orientation independence.
- High Integration Possible: Enables complex processes in single device with higher efficiency.
- Modular & Reconfigurable: Enhances reliability, configurable in broad range of capacities, enables incremental capacity growth, testing at small capacities and more predictable scale up.
- Mass Production: Microlamination architecture is amenable to mass production if suitable platforms are developed.
How is MBI contributing to the solution?
The team made up of PNNL and OSU has established a significant presence in the field of microchannel heat exchanger technology with basic research papers and successful component development projects for both federal agencies (DoE, DoD, NASA and others) and commercial clients. The MBI has also developed relationships with providers of services for chemical etching and bonding for making heat exchanger components.
Work on developing microchannel heat transfer components is performed by several groups within the MBI and at PNNL in Richland, Washington. The MBI has laboratory facilities where microchannel heat transfer devices are designed, built and tested. Chemical etching and diffusion bonding are typically contracted for with an outside company having an established relationship with the MBI. Laboratory facilities allow testing of new microchannel device performance with stand-alone components or when integrated into a larger system.
- Richard B. Peterson, Director of the Tactical Energy Systems Program
- Ward TeGrotenhuis, Co-Director of the MBI
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