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This paper presents the development of a miniaturization technology for heat and mass exchangers used in absorption heat pumps. Short lengths of microchannel tubes are placed in a square array, with several such arrays being stacked vertically. Successive tube arrays are oriented in a transverse orientation perpendicular to the tubes in adjacent levels. In an absorber application, the liquid solution flows in the falling-film mode countercurrent to the coolant through the tube rows. Vapor flows upward through the lattice formed by the tube banks, countercurrent to the falling solution. The effective vapor-solution contact minimizes heat and mass transfer resistances, the solution and vapor streams are self-distributing, and wetting problems are minimized. Coolant-side heat transfer coefficients are extremely high without any passive or active surface treatment or enhancement, due to the small tube diameter. A preliminary model of the absorption process for ammonia-water absorbers using this configuration under typical operating conditions demonstrates the potential for extremely small absorption system components. This novel concept is compact, modular, and versatile and easy to design and fabricate. The technology is suitable for almost all absorption heat pump components (absorbers, desorbers, condensers, rectifiers, and evaporators) and for several industries involved in binary-fluid processes.

Units: SI

Citation: Symposium, ASHRAE Transactions, vol. 106, pt. 1