Desiccation Research Articles (Page 1)

Experimental investigation on LiCl-KCOOH blend for enhancing hybrid liquid desiccant–vapour compression system performance

ABSTRACTThis research investigates an alternative approach to conventional methods of dehumidification to reduce the consumption of electricity and its negative impact on the environment. Alternative methods such as chemical dehumidification using desiccant materials were found to be highly effective. Due to the limitations of the currently used solid and liquid desiccants, biopolymer beads could be used as an effective solution. In this study, spherical beads were developed using sodium alginate, a non‐toxic biopolymer, and desiccant salts were incorporated by ion‐induced gelation. Three different salt combinations in various concentrations were tested and optimized, and six were selected among them for further characterization and assay. Fourier transform infrared spectroscopy studies confirmed the bond formation of these cations with COO− groups of alginate. High moisture absorption rates of zinc–magnesium 15% (ZM15) and zinc–aluminum 15% (ZA15) samples at 78.5% and 67.8%, respectively, were observed. The maximum regeneration temperature of the ZM15 sample was determined as 66.8°C from thermogravimetric analysis, which is in the range of currently used liquid desiccant materials. Antibacterial activity tests showed promising results for all the experimented samples with prominent inhibition zones. These findings indicate that the developed beads are suitable for utilization in air dehumidification and purification systems.

Demand for air conditioning is rising exponentially due to improving economic conditions of large population of the world, growth of built-up space, changing lifestyles of people and higher comfort expectations. Most of the air conditioning systems use vapor compression refrigeration technology which needs electrical power to run. This has resulted in issues like higher peak demands for electrical power and higher direct and indirect emissions of greenhouse gases as well as other pollutants. The above issues can be alleviated by developing thermally activated air conditioning technologies, which use heat as the main energy source. Out of various thermally activated air conditioning technologies, liquid desiccant-based air conditioning (LDAC) systems are very attractive due to their adaptability for solar thermal energy. In LDAC systems the dehumidifier provides cooling using concentrated LD solution. This solution gets diluted there by absorbing moisture. The regenerator of LDAC systems utilizes thermal energy to remove water from the dilute LD solution to concentrate it and thus complete the cycle. The performance of the solar regenerators may be evaluated in terms of regeneration rate (moisture removal rate in ml/m2·h) and regeneration efficiency (useful heat/ solar energy input, unitless). Weather parameters like solar insolation, wind velocity, ambient temperature and system parameter like concentration affect the performance of the regenerator. The regenerator used in the current study is ‘passive solar’, meaning that no fan or pump is used in the device and solar thermal energy is the source of energy. Regression analysis of full factorial study was done using MinitabTM software to understand the effect of various parameters on performance of the passive solar regenerator. It is observed that as independent parameters, solar insolation, ambient temperature and concentration of LD have significant effect on the performance of the solar passive regenerator. The pareto chart shows that solar insolation has the most prominent effect on performance followed by the concentration of LD. Solar insolation has a positive effect on performance while higher concentration affects the performance negatively. The interaction plot for regeneration rate shows that solar insolation, when paired with other parameters, also has a considerable effect on the performance. The two-way interaction of wind velocity and concentration also has significant effect on the performance. Using ANOVATM, it was seen that the full factorial experiment design is linear. The insights developed in current work would help decide viability of using the passive solar regenerator at a given location and deciding the concentration range to be used in LDAC systems.

ABSTRACTThis study analyses the feasibility of a LDD system for the drying process of vegetables and fruits. An experimental setup was fabricated to observe the correlation between the relative humidity and airflow velocity. In this investigation, the influence of airflow velocity on relative humidity at the outlet and the moisture extraction rate is analyzed. Results indicate that an increase in air velocity enhances the drop in relative humidity, which is very essential for the drying of products. However, beyond a particular limit of air velocity, the moisture extraction rate demonstrates a decrease. This decrease is due to the diminishing quantity of liquid desiccant solution necessary in relation to the escalating air velocity. Achieving a relative humidity of 25.66% requires a temperature rise of 34.8°C in the convective system, while the LDD system achieves the same with a lower temperature rise of 32.2°C under identical inlet conditions. This indicates that the LDD system provides better drying conditions compared to conventional methods. Hence, the LDD system proves to be superior in preserving quality, texture, and other essential properties of perishable products in the drying process. These findings contribute to the usefulness of the LDD system for drying operations at low temperatures.

ABSTRACTA desiccant cooling system is a promising, effective, energy‐conserving, and eco‐friendly technology that reduces the heat load of vapor compression refrigeration (VCR)‐based cooling systems when integrated into LDVC systems. In this study, a liquid desiccant dehumidification system combined with a VCR‐based air conditioning system (LDVC) with a cooling capacity of 5 kW was experimentally investigated using calcium chloride as a liquid desiccant solution. An uncertainty analysis was conducted to ensure the sensitivity and accuracy of the obtained results. For the investigation, three factors, airflow rate, desiccant flow rate, and desiccant concentration, with four input levels, were selected. Various combinations of these factors and levels used the Taguchi method to determine their effects on relative humidity difference, absorber heat load, coefficient of performance of the LDVC, and energy savings. Regression corrections for all responses were also determined. The performance of the LDVC was compared with that of a standalone VCR system under identical input conditions and cooling effects. Based on the TOPSIS results, the experimental outcomes achieved a reduction in specific humidity by 9.8 g/kg of dry air, an absorbed heat load of 1.23 kW, a COP of 2.23, and an energy saving of 49%. Compared to the standalone VCR system, the COP increased by 26%, with the dehumidifier sharing 49% of the latent heat load. Exergy analysis revealed that the compressor and absorber exhibited low exergy efficiency, highlighting the potential for performance improvement. Economic analysis indicated a payback period of 3.6 years. Overall, the experimental results demonstrated that the LDVC system offers superior performance compared to the standalone VCR system.

An aluminum finned-tube type internally-cooled deep dehumidifier using ionic liquid desiccant for low-humidity industries: Modelling and case study

Development of a Liquid Desiccant Air Conditioning System Using Ionic Liquids

In this study, improvement was made for the liquid desiccant air-conditioning (LDAC) system by incorporating the embossed stainless-steel plates to a typical plate-type liquid desiccant dehumidification system. Through experimental studies, the performances of the plate-type LDAC system were evaluated. In addition, the effect of two embossed stainless-steel plates, diamond checkered, and rice stamping was assessed and compared. It was found that the performance of the dehumidification system was enhanced, and the energy consumption of the system was decreased for all the two embossed plates, in which the degree of enhancement form rice stamping plate was the most significant. With appropriate simulation parameters and embossed plates selection of the dehumidification system, the enhancement potential of system could have energy saving of 71% against the original one. This design would be certainly helpful in promoting the application of liquid desiccant air-conditioning systems in hot and humid climates.

Improving Liquid Desiccant Dehumidifiers through Square Baffle Plate Design and Nanofluid Innovation

Low corrosive dual desiccant air conditioning: Antimicrobial activity, performance characteristics, and economic valuation with traditional VCRS

Withdrawal notice to: “Improving Liquid Desiccant Dehumidifiers through Square Baffle Plate Design and Nanofluid Innovation” [International Journal of Refrigeration 170 (2025) 398

ABSTRACT A photovoltaic/thermal (PV/T) based solar-regenerated liquid desiccant hybrid air-conditioning systems is being established and trials were performed over a time frame of 9 months, encompassing rainy, cold, and hot weather in a dry and hot region in central India. The desiccant equipment is paired with a sensible cooling system that cools the desiccant as well as the air. For increment in the performance, the application of microencapsulated phase change material is employed with liquid desiccant as working fluid for dehumidification. The system is entirely devoted to outside air. Lithium chloride solution is employed for the purpose of basic liquid desiccant. A comparative analysis has been carried out for with and without phase change material. The developed cooling system effectively regulates room temperature within the human thermal comfort range (20–27°C summer, 42.2°C monsoon), with 60% relative humidity and 16–18°C with 55% average humidity. The addition of PCM improves MRR by 37.5% and 22.2% and enhances dehumidifier effectiveness by 15.4% and 14.7% for the summer and monsoon seasons. The whole system’s effectiveness is described as a function of dehumidification efficiency, removal of moisture rate, ability to cool, and thermal coefficient of performance (COP). The results of the study were additionally assessed against models in the published work.

Abstract Advanced internally cooled liquid desiccant air dehumidifiers enhance overall air-conditioning efficiency by incorporating internal cooling mechanisms. Their existing simulation models require detailed dehumidifier information, are computationally expensive, and pose challenges in convergence, which makes them unsuitable for integration into Building Energy Simulation software for air-conditioning system simulation. This study aims to investigate a method to generate models with less computational demands during simulation using artificial neural networks to represent the operation of an internally cooled dehumidifier. A comprehensive finite difference model was used to generate a data set representative of the expected operation conditions of the device for training the neural network. Various network configurations were explored to assess their impact on prediction precision, following a trial-and-error approach. During the training process, the neural networks reached R values between 0.96 and 0.98 for the different variables. Then, the networks were implemented in a stand-alone code, independent from training, and using basic programming methods. In this implementation, the trained networks underwent a secondary evaluation for prediction accuracy using a distinct data set from the training stage, proving accurate to simulate the internally cooled dehumidifier, reaching values well below 10% for the five predicted outlet variables in comparison to the validated, detailed finite differences model. The overall best performance was found for a network comprising two hidden layers of ten neurons each. This is the initial step towards incorporating neural network models into specialized Building Energy Simulation software, as the foundation for conducting system-level, transient, and long-term simulations.

ABSTRACT This research project delves into the application of membrane-based dehumidification, employing a hydrophobic PVDF membrane in conjunction with a liquid desiccant. The experimental setup consists of acrylic sheets arranged in a cross-flow configuration to encase the membrane material. In this setup, MgCl2 functions as the desiccant, while zeolites serve as the enhancing additive. The experiments involve varying the air velocity within the range of 2m/s to 8m/s, adjusting the desiccant concentration from 20% to 40%, and exploring different zeolite concentrations at mass ratios ranging from 1:3 to 1:2 relative to the desiccant. The results showed that zeolites significantly enhance desiccant efficiency, with effectiveness ranging from 9.7% to 82.7%. Systems with zeolites exhibited efficiency gains of up to 82.7% compared to those without, especially at higher concentrations and velocities. The maximum COP of 2.1 was observed for 40% MgCl2 with (1:2) concentration and 8m/s velocity. The addition of zeolite caused a slight increase in the exit air temperature compared to the temperature rise observed with only the MgCl2 solution. In a 40% MgCl2 desiccant solution with zeolites, the temperature rise was 12% higher with a 1:2 zeolite ratio compared to a 1:3 ratio.

Experimental and 4NTU-Le heat and mass transfer model theoretical analysis based on a novel internally cooled liquid desiccant dehumidifier

Investigating the performance of direct contact membrane distillation for liquid desiccant regeneration and freshwater production: A CFD-based study

The increasing carbon footprint associated with conventional cooling methods underscores the urgent need for sustainable alternatives. This study investigates the economic and environmental advantages of various solar-thermal cooling systems, with a focus on optimizing their performance across different climate conditions. Employing a multi-objective approach, the research emphasizes exergy-economic indices to optimize selected cycles. The analysis covers multiple refrigeration technologies, including liquid absorption, solid adsorption, and solid desiccant cycles. Results indicate that the liquid absorption cycle performs optimally in hot, arid climates, reducing the payback period to approximately 8 years when optimized. In hot and humid regions, the solid desiccant cycle proves most effective due to its superior humidity control, yielding a payback period of 5.3 years. For cold and mountainous areas, the solid adsorption cycle is preferred, with a payback period of 13.5 years, while moderate and humid climates benefit from the solid desiccant cycle for both cooling and humidity regulation. The exergy-economic factors for the solar refrigeration systems across semi-arid, hot and arid, hot and humid, cold and mountainous, and moderate and humid climates are 0.758, 0.602, 0.698, 0.74, and 0.575, respectively.

Efficiency Analysis of a Developed Industrial Refrigerator Using Liquid Desiccant Cooling as Mode of Operation

Multi-hierarchical structured PTFE membrane for liquid desiccant dewatering via membrane distillation

Experimental performance investigation on a desiccant-assisted two-stage evaporative cooling system in hot and humid areas