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OPTIMIZATION OF HUMIDIFIER DESIGN USING FIXED EFFECTIVENESS APPROACH FOR HDH SYSTEM

Ranjitha Raj P
Department of Mechanical Engineering, Amrita Vishwa Vidyapeetham, Amritapuri , India

J. S. Jayakumar
Department of Mechanical Engineering, Amrita Vishwa Vidyapeetham, Amritapuri, India

Balakrishnan Shankar
Department of Mechanical Engineering, Amrita Vishwa Vidyapeetham, Amritapuri, India

DOI: 10.1615/IHMTC-2017.2540
pages 1823-1829

摘要

Humidification dehumidification system (HDH) is widely accepted as an ideal method for solar water desalination and water purification at an affordable cost in coastal areas. HDH desalination cycle is an improvised form of natural rain cycle. The optimum performance of the whole system depends on the humidifier design to a large extend. Humidifier increases the amount of water vapor in air when it is brought in contact with water. The equipment is an example of direct contact heat and mass exchanging device (HME). Fixed effectiveness approach is one of the widely accepted techniques adopted in humidifier design. In general, fixing the effectiveness of the HME device does not explicitly define the component sizing. As a result, it become challenging to link the properties of fixed effectiveness model with the actual system characteristics. But if the model calculations are incorporated with the geometry factors of humidifier, fixed effectiveness approach can best explain the process stream properties of the equipment. The results so obtained can be used to design humidifier for a HDH solar desalination system with air as the carrier gas. In the present work humidity ratio profile of moist air is developed along the humidifier column using the computed values of column diameter and packing height. Mass transfer coefficient was assumed to vary with the humidity ratio along the humidifier. Random packing is used in the humidifier to increase the surface area of contact between hot feed saline water and cold dry air. The objective of the work is to optimize humidifier design for HDH system. Optimization was carried out using MATLAB® simulation. Diameter and packing height in the humidifier is optimized in such a way to get maximum humidity ratio for the exit air. Influence of mass flow rate ratio of water to air on the humidifier performance is detailed in the present study. Results obtained from the simulation shows that the outlet air humidity and water productivity decreases with increase in mass flow rate ratio of water to air.

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