Refrigeration Cycle Based on a Membrane Separation Technology

This article introduces a tentative to modify an adsorption inverse cycle. In comparison to a classic absorption cycle, the difference is in the use of a membrane technology in order to separate the two fluids (refrigerant and absorbent), instead of a separation by distillation. In practice, the cycle is modified by inserting a hydrophobic Membrane Contactor in order to make a liquid-liquid extraction of a solute easily absorbed in water (solvent). In this way, the classical absorption cycle can be modified with the complete elimination of heat supply, used to separate the solute from solvent, replacing it with the pump work necessary to pressurize and circulate the fluids involved in the cycle. This is enabled because the separation of the two fluids in the Contactor Membrane is obtained thanks to a generation of a concentration gradient. The adopted membrane contactor, commercially available, is realized by means of hollow porous fiber of polypropylene (PP) positioned in an cartridge of polyethylene (PE). The concentration gradient is realized between the two size of the membrane, i.e. water at high concentration of the solute and the other size in which an organic solvent flows at low concentration of the solute. As secondary fluid, organic solvent, we adopted and tested diesel oil. The result demonstrates the technical feasibility of the proposed cycle through some preliminary results obtained adopting ethylic alcohol and acetaldehyde, both of them absorbed by water.