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[en] This paper presents a study on the regeneration performance characteristics of an internally heated regenerator applicable to a liquid desiccant system. The internally heated regenerator used in this study was designed and manufactured to provide better regeneration performance. An experimental setup was established to examine the regeneration performance. LiCl aqueous solution was used as working fluid. Variables to evaluate regeneration performance characteristics of the internally heated regenerator were dry bulb temperature, relative humidity and velocity of regeneration air, mass flow rate, temperature and concentration of the LiCl aqueous solution. The experimental conditions were chosen by using a 1/2 fractional factorial DOE. Regeneration rate and regeneration effectiveness were taken as results. From the results, solution concentration and regeneration air relative humidity have strong effects on the regeneration rate. The regeneration effectiveness was affected mostly by regeneration air velocity.
[en] A method and apparatus are disclosed for continuously drying and regenerating ceramic beads for use in process gas moisture drying operations such as glove boxes. A microwave energy source is coupled to a process chamber to internally heat the ceramic beads and vaporize moisture contained therein. In a preferred embodiment, the moisture laden ceramic beads are conveyed toward the microwave source by a screw mechanism. The regenerated beads flow down outside of the screw mechanism and are available to absorb additional moisture
[en] Drying agricultural produce using renewable sources of energy has recently been receiving widespread attention. Many different approaches to this diverse problem are reported in the literature. The present study deals with the novel approach of using a desiccant adsorbent as a drying medium for grains. The general idea studied involves placing moisture-saturated grain of relatively high vapour pressure in intimate contact with an adsorbent of relatively low vapour pressure. The resulting vapour pressure gradient serves to force the migration of moisture from the saturated grain to the desiccant environment. Once the desiccant becomes saturated during drying, it can be thermally regenerated and used again. This regeneration process could be affected by using solar energy. (author)
[en] A theoretical model is developed to simulate the heat and mass transfer processes in a cross flow dehumidifier/regenerator using liquid desiccant. The model depends on NTU as input parameter, and NTU can be correlated based on the corresponding experimental data. The model is able to predict the air and desiccant parameters inside the dehumidifier/regenerator, as well as the outlet parameters, with known inlet parameters. The calculated results are compared with the experimental findings. For the total 284 groups of dehumidification experimental data with different module sizes, the average absolute discrepancies for enthalpy effectiveness and moisture effectiveness are 7.9% and 8.5%, respectively. For the 82 groups of regeneration experimental results, the average discrepancies for enthalpy and moisture effectiveness are 5.8% and 6.9%, respectively. The distributions of desiccant outlet temperatures are measured during both the dehumidification and regeneration processes, and the temperatures predicted by the theoretical model agree well with the experimental results
[en] Highlights: • A ground-coupled desiccant assisted air conditioning system is evaluated experimentally. • The evaluation is carried out for steady state operation and the cooling period as a whole. • The suitability of the system to provide comfort conditions is examined demonstrated. • Energy comparisons with other air-conditioning systems are performed. • The performance of the borehole heat exchangers for cooling is evaluated. - Abstract: In a pilot installation at Hamburg University of Technology the coupled operation of an open cycle desiccant assisted air conditioning system with borehole heat exchangers is investigated. The paper presents experimental data recorded during the cooling period 2014. Results show that the electricity demand of the system can be reduced to the parasitic consumption of the fans, wheels and pumps. An electric energy efficiency ratio of 6.63 is achieved, enabling electricity savings of more than 70% compared to a conventional reference system and 54% compared to a desiccant assisted hybrid system relying on an electric chiller. Comfort conditions can be maintained during the whole cooling period. The borehole heat exchangers work highly efficient, exhibiting a seasonal performance factor of 192.
[en] As fusion research facilities and power plants are sure to require a large atmospheric-detritiation system (ADSs) to mitigate the tritium releases and to recover the heavy water vapor. The best available technology for these systems is the oxidized-and-adsorb process, where tritiated species are converted to tritium oxide (HTO) and adsorbed onto an atmospheric-detritiation dryer (ADD). Conventional ADDs use synthetic zeolites as the adsorbent and rely on a thermal swing cycle. This permits a continuous detritiation of a gas by using multiple desiccant beds, each bed being regenerated following a period of moisture removal (adsorption). The performance of a desiccant dryer depends on the simultaneous transfer of the mass and energy between the flowing gas and solid desiccant. In designing a fixed bed dryer and preparing an advanced dryer control, it is necessary to quantify the bed utilization and dynamic behavior against inlet humidity and flow rate. In this study, a quantitative evaluation based on an adsorption test was carried out to evaluate the adsorption characteristics and the operating performance of an atmospheric detritiation dryer
[en] Highlights: •Thermodynamic principles are applied to systematically compare three technologies. •Merits and limits of standalone versus integrated designs are identified. •Effect of climate conditions on performance and technology selection is evaluated. •Integrated desiccant/membrane technologies outperform current state-of-the-art VCS. -- Abstract: Recently, next-generation HVAC technologies have gained attention as potential alternatives to the conventional vapor-compression system (VCS) for dehumidification and cooling. Previous studies have primarily focused on analyzing a specific technology or its application to a particular climate. A comparison of these technologies is necessary to elucidate the reasons and conditions under which one technology might outperform the rest. In this study, we apply a uniform framework based on fundamental thermodynamic principles to assess and compare different HVAC technologies from an energy conversion standpoint. The thermodynamic least work of dehumidification and cooling is formally defined as a thermodynamic benchmark, while VCS performance is chosen as the industry benchmark against which other technologies, namely desiccant-based cooling system (DCS) and membrane-based cooling system (MCS), are compared. The effect of outdoor temperature and humidity on device performance is investigated, and key insights underlying the dehumidification and cooling process are elucidated. In spite of the great potential of DCS and MCS technologies, our results underscore the need for improved system-level design and integration if DCS or MCS are to compete with VCS. Our findings have significant implications for the design and operation of next-generation HVAC technologies and shed light on potential avenues to achieve higher efficiencies in dehumidification and cooling applications.
[en] Full text: The complex coating dryers are produced with good 2-Ethylhexanoic acid, rare earths and other metals. Simply using such a complex drier can get the total effect instead of the traditional dryers such as Co, Mn, Pb, Zn, Ca etc. It has advantages of saving quantity, decreasing cost, simplifying process, making the operation convenient, good quality, good stability and without Pb. Invention patent of China requisition number is 95119867.X
[en] Regenerator is major component of liquid desiccant regeneration system. The influence of operating parameters; air flow rate, solution flow rate and concentration of desiccant is investigated experimentally on the performance parameters; outlet specific humidity, evaporation rate, air outlet temperature, mass transfer coefficient and effectiveness of the regenerator. Air and desiccant solution flow in counter direction with celdek pads as packing material. It is concluded that evaporation rate increases with increasing solution temperature, air flow rate and solution flow rate whereas same decreases with increasing concentration of desiccant. The effectiveness of regenerator is increased by 99 % with increase in air flow rate. A comparison of present finding with those available in the literature is presented in the last. Simulation results have revealed good agreement between the present experimental results.
[en] A frequently used method in determining the radium concentration of water is the radon emanation method. When radon gas is transferred to the Lucas-cell usually CaCl2 is used to remove the water traces. When the background of the system was measured using ultra clear distilled water the results were astonishing. The detailed investigation has shown that the unwanted radon originated from the CaCl2, contained about 1000 Bq/kg of 226Ra. Depending on the time interval between two measurement, the radon deriving from the CaCl2 disturbed the measurements. (author)