Abstract
A solar-fired liquid desiccant cooling and dehumidification system has been proposed, analyzed and simulated on a digital computer. The entire study comprised of three distinct but related stages. The first phase of the study dealt with modeling a modified version of a roof-pool that works as an indirect evaporative cooler. A one-dimensional analysis performed on the adiabatic counter-flow plate heat exchanger indicated that the proposed cooler affords satisfactory performance. The next phase of the study was extensive and dealt with analyzing and modeling the behavior of an air dehumidification unit, the packed tower absorber. The study began with the derivation of heat and mass transfer coefficients, in the form of correlations, suitable for use with detailed computer models. Two packing materials, Raschig rings and Berl saddles, with the liquid desiccant being CaCl₂, were studied. Then an analytical investigation of the dehumidification of air occurring in a packed bed was carried out, by solving one-dimensional material- and energy-balance equations on a differential control-volume of the tower. The concept of a "moisture removal effectiveness", for a mass exchanger with heat effects, has been defined in this work, which is analogous to the thermal effectiveness approach used to model sensible heat exchangers. All the tower outlet conditions can be predicted via the effectiveness approach, making the modeling very appealing for transient simulation codes. The final phase of the work centered around modeling the remaining components of the proposed liquid desiccant system: open flow regenerator, sensible heat exchanger and liquid desiccant storage tank; calculating the space cooling load; and finally integrating all the subsystem models via an executive routine into an overall transient systems model. A detailed analysis revealed that a liquid desiccant system would be useful in high ventilation areas and where instead of the ARI room conditions one is satisfied with relatively higher room temperatures (say 80°F) which are nearly offset by relatively lower room humidities (say in the 50's). Also, a system performance for Houston, Texas, yielded seasonal thermal COP's of around 0.90; with electrical COP estimated at around 0.60, suggesting room for further research when compared with typical vapor compression electrical COP's of around 2.50.
Ullah, Mohammad Rifat (1986). Analysis of a counterflow indirect evaporative cooling and liquid desiccant dehumidification system. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -17121.