Desiccant Temperature Research Articles

Study of Desiccant Regeneration in a Structured Packed Tower

The performance of a liquid desiccant regenerator, equipped with structured packing made of wood, was investigated for the regeneration of triethylene glycol (TEG). The effects of air and desiccant flow rates, air and desiccant temperature, and desiccant concentration were studied to assess their impact on the regeneration process. The influence of these parameters on the performance of the desiccant regenerator was evaluated in terms of the rate of water evaporation and the effectiveness of the regeneration process. It was found that under the conditions of this study, the desiccant inlet temperature was the most favorable variable, while the inlet desiccant concentration was the least favorable with respect to the regeneration process. The air mass flux increased the rate of water evaporation, but reduced the regenerator effectiveness significantly. The other parameters had a negligible effect. The results of this study were in agreement with the Chung and Luo correlation and published literature.

Performance study on a structured packed liquid desiccant regenerator

The solution carryover in traditional desiccant regeneration towers is of serious concern in real applications especially when using triethylene glycol (TEG) as a desiccant. In this study, the cellulose rigid media pads are used as the structured packing. The packing arrangements have provided minimum carryover of TEG. A performance study of the simultaneous heat and mass transfer between air and desiccant in a structured packed-stripping tower is conducted. Through the study of the regenerator, important design variables are defined and the regenerator performance is compared with the previous studies. The effects of air and liquid flow rates, air humidity, desiccant temperature and desiccant concentration have been reported on the evaporation rate and humidity effectiveness of the column. It is found that high liquid flow rates do not have a significant effect on the performance variables.

Study of an aqueous lithium chloride desiccant system: air dehumidification and desiccant regeneration

Desiccant systems have been proposed as energy saving alternatives to vapor compression air conditioning for handling the latent load. Use of liquid desiccants offers several design and performance advantages over solid desiccants, especially when solar energy is used for regeneration. For liquid–gas contact, packed towers with low pressure drop provide good heat and mass transfer characteristics for compact designs. This paper presents the results from a study of the performance of a packed tower absorber and regenerator for an aqueous lithium chloride desiccant dehumidification system. The rates of dehumidification and regeneration, as well as the effectiveness of the dehumidification and regeneration processes were assessed under the effects of variables such as air and desiccant flow rates, air temperature and humidity, and desiccant temperature and concentration. A variation of the Öberg and Goswami mathematical model was used to predict the experimental findings giving satisfactory results.

Heat and Mass Transfer in Packed Bed Liquid Desiccant Regenerators—An Experimental Investigation

Liquid desiccant cooling can provide control of temperature and humidity, while at the same time lowering the electrical energy requirement for air conditioning. Since the largest energy requirement associated with desiccant cooling is low temperature heat for desiccant regeneration, the regeneration process greatly influences the overall system performance. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer on the regeneration process are of great interest. Due to the complexity of the regeneration process, which involves simultaneous heat and mass transfer, theoretical modeling must be verified by experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed regenerator using high liquid flow rates. To regenerate the desiccant, it is heated to temperatures readily obtainable from flat-plate solar collectors. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of water evaporation, as well as the effectiveness of the regeneration process is assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, the findings in the present study are compared to findings previously reported In the literature. Also, the results presented here characterize the important variables that impact the system design.

Experimental Study of the Heat and Mass Transfer in a Packed Bed Liquid Desiccant Air Dehumidifier

Desiccant cooling systems have the ability to provide efficient humidity and temperature control while reducing the electrical energy requirement for air conditioning as compared to a conventional system. Naturally, the desiccant air dehumidification process greatly influences the overall performance of the desiccant system. Therefore, the effects of variables such as air and desiccant flow rates, air temperature and humidity, desiccant temperature and concentration, and the area available for heat and mass transfer are of great interest. Due to the complexity of the dehumidification process, theoretical modeling relies heavily upon experimental studies. However, a limited number of experimental studies are reported in the literature. This paper presents results from a detailed experimental investigation of the heat and mass transfer between a liquid desiccant (triethylene glycol) and air in a packed bed absorption tower using high liquid flow rates. A high performance packing that combines good heat and mass transfer characteristics with low pressure drop is used. The rate of dehumidification, as well as the effectiveness of the dehumidification process are assessed based on the variables listed above. Good agreement is shown to exist between the experimental findings and predictions from finite difference modeling. In addition, a comparison between the findings in the present study and findings previously reported in the literature is made. The results obtained from this study make it possible to characterize the important variables which impact the system design.

Experimental Investigations on the Performance of a Packed Bed Dehumidifier for Various Climatic Conditions

ABSTRACT To simulate space cooling or drying systems for various geographical regions (low, moderate, and high humidity regions) a liquid desiccant system consisting of a humidifier and dehumidifier has been designed and constructed. This system consists of two coupled humidifying and dehumidifying packed columns filled with plastic Intalox Snowflake packing material. Experimental measurements of the dehumidifier performance utilizing a new effective liquid desiccant mixture (CELD) total desiccant salt content 40%wt.to 45%wt (salt comprised of equal portions by weight of lithium chloride and calcium chloride ), have. been carried out, The effect of different independent variables such as packing height, air inlet temperature and humidity ratio, and liquid desiccant inlet temperature, flow rate and concentration on the performance of the dehumidifier has been investigated. Experimental results demonstrate that the CELD is a promising desiccant for cooling and drying operations.

Concentration of liquid foods using desiccants: An experimental study

Liquid foods are often partially dehydrated to reduce their water content so as to enhance their storage stability. Evaporation, which consumes large amounts of energy, is the most widely used operation for concentrating liquid foods. The paper describes a novel system to concentrate liquid foods by using liquid desiccants. In the proposed system, water vapour, evaporated from the liquid food at reduced pressure, passes to the liquid desiccant, where it is absorbed while liberating its latent heat. The liquid desiccant temperature thereby increases. The warm liquid desiccant can then be used to provide a portion of the thermal energy for the evaporation of the water in the liquid food. A vertical, double-falling-film evaporator which uses calcium chloride solution was built and was used to concentrate liquid foods. The experimental set-up was tested to study the influence of the liquid-desiccant flow rate, the liquid-food flow rate, and the liquid-desiccant concentration and temperature. Some of the experimental results are discussed in this paper.

The Performance of Various Types of Regenerators for Liquid Desiccants

A solar-assisted cooling system is very attractive because the available solar energy and the required cooling load are generally in phase. Of all the solar-assisted cooling methods developed to date, the absorption cooling system and the desiccant dehumidification/evaporative cooling system are considered most suitable for solar or other low-grade thermal energy applications. An efficient liquid desiccant cooling/dehumidification system has been proposed and analyzed by the authors. This system promises low operating parasitic power requirements, and it accepts thermal energy at a temperature as low as 60/sup 0/C, which can be efficiently obtained in a flat-plate solar collector. A schematic diagram of this system is shown. Briefly, this system operates by bringing outside air plus recycled air in contact with a liquid desiccant solution (triethylene glycol, in this case) in the absorber unit. A portion of the dried air is then cycled through the evaporator in contact with the falling water film, thus cooling the water. Cooled water from the evaporator is recycled to cool the absorber unit and hold down the desiccant temperature, and and thereby produce cool and dry air.

Design and Testing of a Liquid Desiccant Dehumidifier

ABSTRACT A dehumidification system employing liquid desiccant was designed, constructed, and tested to determine the effect desiccant and air temperatures have on water vapor absorption rate. Calcium chloride desiccant was used for experimentation. A linear mathematical equation expressing concentration and concentration ratio as a function of time described the sorption process. The slope of this line, termed the sorption constant, increased with increasing air temperature and/or decreasing desiccant temperature. Air temperature had a more significant effect on the sorption constant than did desiccant temperature. The sorption constant can be adequately described as a logarithmic function of initial vapor pressure difference between the air and desiccant solution.

Recoveries of Salmonella ndolo from desiccates exposed to 100 degrees C under various conditions with respect to desiccant, desiccant temperature and atmosphere.

Desiccates of Salmonella ndolo dried in sodium glutamate have been exposed to 100 degrees C. in air or in vacuo; in the presence of wet or dry P(2)O(5); and with desiccant maintained at either 25 degrees or 100 degrees C. Of the eight treatments thus compared, rapid killing occurred where the desiccate was heated in vacuo and in the presence of dry P(2)O(5) maintained at 100 degrees C. There was little difference among the death-rates of the other seven treatments. Sublimation of the P(2)O(5) with resultant attack on the desiccate would appear to be responsible for the rapid killing in the treatment where it was observed.