Design and optimization of a humidifier for an HDH system

Abstract

Two billion people around the world do not access to clean drinking water. 98% of deaths caused by water related illness occur in the developing world. The humidification dehumidification desalination system currently being developed at the Lienhard Research Laboratory is a water treatment technology with low operational requirements that make it ideal for operation in the developing world. Researchers in the lab have just developed a novel design methodology for optimizing the performance of an HDH system based on thermal balancing, similar to the methodology used in heat exchanger design. An experimental pilot sized unit was built to test this methodology on a packed bed humidifier. Non-dimensional entropy generation was shown to have a minimum value for varied mass flow ratio as well as for varied water inlet temperature. At its optimal performance condition, the humidifier built for this thesis has a temperature pinch of 2.8 °C and an enthalpy pinch of 14.8 kJ/kg dry air. For the first time in literature, this thesis has experimentally shown that the balanced condition of HCR=1 corresponds to the condition of minimum entropy generation, validating the design methodology previously proposed at the Lienhard Lab.