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[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] 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] 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] This paper describes the preliminary structural concept design for the mechanical system, structures and equipment of KALIMER-600, 600MWe pool type liquid metal reactor with sodium coolant. The key contents are new conceptual design for the mechanical structures, the reactor internal structures, reactor head and piping systems, reactor containment structures in points of economical improvement. The thermal protection devices of reactor vessel and the refueling system have been conceptually established
[en] The concept of dehumidification between air and liquid desiccant for the improvement of the efficiency of heating and cooling fluids in industrial applications was discussed. The use of solid/liquid desiccants has received much attention in recent years because liquid desiccants can take moisture from surrounding air at low temperature and then release the moisture at high temperature to provide a continuous process of dehumidification of air and regeneration of liquid desiccant. This process can be used with conventional vapor compression cycles. This paper presented a comparative numerical study between parallel and counter flow configurations that examined the effects of various parameters on heat and mass transfer for the dehumidification and cooling processes of air and regeneration rate of liquid desiccant. Ultrafine particles were added to the falling film desiccant to investigate heat and mass transfer enhancement for both parallel and counter flow channels. The Cu-volume fraction in the falling film desiccant and dispersion effect were the important parameters. A mathematical model was therefore developed to account for the addition of Cu-ultrafine particles into the film desiccant. The dehumidification and cooling rate processes were found to improve with an increase in the Cu-ultrafine particles and dispersion effect. The new hybrid AC system was shown to improve indoor air quality, reduce energy consumption, and be environmentally safe. It was concluded that although the volume fraction and dispersion factor improve the dehumidification and cooling processes of the air, the improvements are not significant due to the small thickness of the falling-film desiccant. The regeneration process did not improve for either controlling parameter because of the small thickness of the film desiccant. 14 refs., 10 figs
[en] The effects on the performance of an air-detritiation dryer (ADD) of inlet-gas humidity and residual tritiated water (HTO) left on the desiccant following regeneration were demonstrated. Residual HTO significantly reduced the detritiation factor (DFSP) of an ADD from clean-bed values. In addition, HTO/H2O separation occurred in the ADD, with H2O leading HTO. HTO roll-up may also have occurred. Finally, an increase in the inlet-gas humidity at constant inlet HTO concentration decreased the DFSP while increasing the humidity-reduction factor (HRFSP)
[en] Highlights: ► A novel desiccant based evaporative cooling system is developed and tested. ► Cooling capacity, COP and energy consumption of the system are evaluated. ► Indoor air conditions are in the range of thermal comfort zone and expanded comfort zone. ► Designing of the system have considerable effect on the energy consumption. - Abstract: A novel configuration of desiccant based evaporative cooling system for air conditioning application is developed and tested. At the beginning of the design stage of the system, an analysis is carried out in order to maximize the performance of the system. It is found based on configuration that outdoor air must be used for regeneration to increase performance of the system and so three air channels are used. Experiments are carried out to investigate the total performance of the system and performance of the components used during summer season in a hot and humid climate. Effectiveness values for both heat exchangers and evaporative coolers are calculated through this work. In addition to the cooling capacity, coefficient of performance (COP) and energy consumption of the system are also evaluated. Results show that the effectiveness for the heat exchangers and evaporative coolers are very high under different outdoor conditions. It is also shown from the results that indoor air conditions are in the range of thermal comfort zone defined by ASHRAE and expanded comfort zone for evaporative air conditioning applications.
[en] Highlights: ► We studied a new process combining liquid desiccants and evaporative cooling. ► We modeled the process using a finite-difference numerical model. ► We measured the performance of the process with experimental prototypes. ► Results show agreement between model and experiment of ±10%. ► Results add confidence to previous modeled energy savings estimates of 40–85%. - Abstract: This article presents modeling and experimental results on a recently proposed liquid desiccant air conditioner, which consists of two stages: a liquid desiccant dehumidifier and an indirect evaporative cooler. Each stage is a stack of channel pairs, where a channel pair is a process air channel separated from an exhaust air channel with a thin plastic plate. In the first stage, a liquid desiccant film, which lines the process air channels, removes moisture from the air through a porous hydrophobic membrane. An evaporating water film wets the surface of the exhaust channels and transfers the enthalpy of vaporization from the liquid desiccant into an exhaust airstream, cooling the desiccant and enabling lower outlet humidity. The second stage is a counterflow indirect evaporative cooler that siphons off and uses a portion of the cool-dry air exiting the second stage as the evaporative sink. The objectives of this article are to (1) present fluid-thermal numerical models for each stage, (2) present experimental results of prototypes for each stage, and (3) compare the modeled and experimental results. Several experiments were performed on the prototypes over a range of inlet temperatures and humidities, process and exhaust air flow rates, and desiccant concentrations and flow rates. The model predicts the experiments within ±10%.
[en] The feasibility of using solar energy instead of electricity for air conditioning and refrigeration has been investigated as part of a trend to explore sustainable and low-carbon technologies that minimize the use of fossil fuels. Solar desiccant cooling systems provide direct air conditioning for indoor spaces using solar energy, with the added benefit of full outdoor air provision. The system can handle the space sensible and latent loads while achieving good indoor air quality. This paper proposed an effective optimization method for a solar desiccant cooling system developed by a simulation model. The parameters for suitable operation and control were determined. The objective of optimization is to maximize the solar fraction against the involvement of auxiliary electric heating. This is a constrained optimization problem since the room temperature should be maintained within a comfortable range. As such, traditional numerical optimization methods cannot be used. However, the evolutionary algorithm (EA) can effectively handle the constrained, nonlinear and multidimensional engineering problems such as those encountered in this solar desiccant cooling system. This study included a comparative evaluation of the 3 major paradigms of the EA in an effort to evaluate a suitable approach for the current engineering application with demanding computational function calls. A model of the solar desiccant cooling system was built and its year-round performance was maximized. 17 refs., 2 tabs., 10 figs
[en] Highlights: ► We present theoretical and experimental investigation of desiccant bed. ► Transient coupled heat and mass transfer in a radial flow desiccant packed bed has been reported. ► A real-time model is used. ► The prediction of air exit conditions from the bed is carried out. - Abstract: Theoretical and experimental investigation on the transient coupled heat and mass transfer in a radial flow desiccant packed bed has been reported in the present work. An experimental test rig has been designed and constructed to carry out the required experimental measurements. System parameters and flowing air conditions (bed weight, air velocity, air conditions – dry and wet bulb temperatures- at exit of test rig components) are measured and analyzed. A hollow cylindrical packed bed has been used as a desiccant dehumidifier. This configuration decreases the required power to blow air through the bed. In the theoretical study, prediction of air exit conditions from the bed is carried out based on the model of Barlow for the analysis of adsorption and regeneration processes in the desiccant bed. This model uses simple effectiveness equations for steady-state heat and mass exchangers within a finite difference procedure. Air at different conditions of temperature and humidity enters the regenerated bed and the exit temperature and humidity are plotted with time. Acceptable agreement is found between the theoretical and experimental results. The most effective parameters on the system performance are the initial water content of the bed and its initial temperature. Bed cooling during adsorption improves the system performance.