Analysis and Design of Efficient Absorbers for Low-Temperature Desiccant Air Conditioners

Abstract

Desiccant dehumidification and air-conditioning systems require careful design to minimize large parasitic power requirements for pumps and blowers. Each component depends to some extent on overall system characteristics, yet each component must be carefully modeled in itself. The most challenging part of optimizing a system is the absorber design. In order to increase the heat and mass transfer rate while minimizing the pressure loss in the absorber, a direct contact falling film fin-tube heat exchanger is analyzed with water flowing on the tube side and desiccant flowing as a falling film on the fin side. Air is cooled and dehumidified by the water and desiccant as it is circulated through the absorber. A model to analyze the heat and mass transfer in the absorber has been developed. An optimum design has been selected based on not only thermal performance but also practical and economic considerations. Application of the absorber design is then made to design of a complete desiccant system for use with low-temperature heat as an energy source.

Cosorption Processes of Triethylene Glycol in a Packed-Bed Liquid Desiccant Dehumidifier

“…The effect of relative flow rates of liquid desiccant to air (i.e., liquid-to-gas flow ratios) has always been identified to exert great influence on the dehumidification performance of dehumidifiers (Peng and Howell 1981;Perry and Green 1982;Lowenstein and Gabruk 1992). However, the effect of liquid-to-gas flow ratios on the removal rates and efficiencies of binary air components (i.e., water and toluene vapors) was not examined in these papers.…”

“…The integral heat of solution in Equation 21, ΔH s , can be determined by the following curvefitted equations using the data given by Konnecke et al (1958) and Peng and Howell (1981): (Reid et al 1987) …”

“…Although research on the absorption properties of TEG for water and various VOCs have been ongoing for some time (Peng and Howell 1981;Ng et al 1983;Grasso et al 1994), there is no published experimental or numerical data on the simultaneous absorption of water vapor and air contaminants by TEG. Chau and Worek (2007) developed a numerical model to simulate the cosorptive characteristics of TEG solutions for both water vapor and VOC air contaminants under various operating conditions through packed-bed absorbers.…”

Predictions of moisture removal rate and dehumidification effectiveness for structured liquid desiccant air dehumidifier

“…For example, Chen et al [15], Patnaik et al [16], McDonald et al [17], Chung et al [18], Potnis and Lenz [19], and Ullah et al [20] carried out experiments on packed bed dehumidifiers, using salt solutions as the desiccants. Chung et al [21], Oberg and Goswami [1], Martin and Goswami [22], Park et al [23], Peng and Howell [24], Chebbah [25], Park et al [26,27], Chung and Luo [28], and Chung and Wu [29] reported some experimental findings using triethylene glycol as the desiccant. Furthermore, Zurigat et al [30] carried out experiments on dehumidifiers with structured packing, using triethylene glycol as the desiccant.…”

Modelling and parametric analysis of heat and mass transfer performance of refrigerant cooled liquid desiccant absorbers

“…Analytical models for packed or water-cooled absorbers and regenerators, based upon conservation of mass and energy equations to study the one-dimensional air temperature and humidity distribution and solution temperature and concentration distribution, are available in the literature (Factor and Grossman, 1980;Peng and Howell, 1981;Scalabrin and Scaltriti, 1988). However, no information is available on the performance of a refrigerant-cooled liquid desiccant absorber in the literature.…”