OPTIMIZATION OF HUMIDIFIER DESIGN USING FIXED EFFECTIVENESS APPROACH FOR HDH SYSTEM
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.