Moisture Removal Capacity Research Articles

Performance Analysis of Desiccant Dehumidifier with an Expanded Regeneration Section

Temperature and humidity are critical parameters for maintaining the storage conditions and ensuring the post-harvest quality and shelf life of agricultural products. This study evaluates the performance of a desiccant dehumidifier under varying conditions to optimize storage environments. The relative humidity of the process air ranges from 60% to 90%, while the regeneration air temperature varies from 60°C to 80°C. The flow rates of process air and regeneration air are fixed at 350 m³/h and 760 m³/h, respectively. The relative humidity of the process air is reduced from 61%–91% at the inlet to 33.5%–48.75% at the outlet. During the experiment, the process air inlet temperature varies between 27.75°C and 36°C, while the regeneration air outlet temperature ranges from 37.75°C to 57.5°C. Performance parameters such as dehumidification effectiveness (η), moisture removal capacity (MRC), coefficient of performance (COP), and sensible energy ratio (SER) were analyzed. At 90% relative humidity and 80°C regeneration air temperature, a maximum dehumidification of 13.35 g/kg was achieved, whereas the lowest dehumidification of 5.5 g/kg was observed at 60% relative humidity and 60°C regeneration air temperature. These findings demonstrate the potential of the desiccant dehumidifier to maintain optimal temperature and humidity levels for prolonged shelf life and reduced post-harvest losses.

Deep dehumidification characteristics of a silica gel coated cross-flow heat exchanger with a circulating blowing loop

Solid desiccant dehumidification systems offer an effective and energy-efficient alternative for deeply dehumidifying air. Desiccant coated heat exchangers (DCHEs), a type of solid desiccant dehumidification system, have garnered attention due to their ability to eliminate adsorption heat and thereby enhance dehumidification capacity, unlike desiccant wheels that perform adiabatic dehumidification. This study introduces a silica gel coated cross-flow DCHE equipped with a circulating blowing loop for deep dehumidification applications. A two-dimensional numerical model is developed to simulate deep dehumidification behavior of the DCHE. Parametric analysis is performed to explore the dehumidification characteristics under various conditions, setting different volume fractions ω of blowing loop air. Results indicate that the DCHE can effectively reduce the moisture content of humid air to a deep dehumidification threshold of 6.2 g/kg. Additionally, dehumidification capacity can be increased by incorporating a circulating blowing loop. The influence of process air velocity, cooling air velocity, process air humidity ratio, regeneration air temperature and air channel length on the dehumidification performance are analyzed, focusing on metrics such as minimum outlet air humidity ratio Ya1,ad,out_min, effective deep dehumidification time teff, moisture removal capacity MRC and dehumidification coefficient of performance DCOP. It is determined that the regeneration air temperature should be raised to 80 °C to ensure deep dehumidification, and an air channel length of 0.2 m is optimal.

Study on the double-coil heat exchanger for dehumidification and heating in greenhouses: Modeling, analysis, and optimization

Heat exchangers are widely used in dehumidification and heating technologies owing to their excellent heat transfer performance, however, their dehumidification capability is limited for greenhouse applications. This study evaluates a double-coil heat exchanger (DC-HE) for dehumidification and heating in greenhouses. Humid air undergoes condensation dehumidification through the dehumidifying coil and is then reheated by the heating coil before being released. Using double coils allows for the separate circulation of cold and warm water in their respective paths, handling the latent and sensible heat of the air. In this study, predictive methods for air treatment in a heat exchanger are combined, and theoretical calculations are performed on the DC-HE and validated through experimental investigations. Furthermore, the impact of variables such as air temperature, relative humidity, water temperature and flow rate, and air flow rate on the moisture removal rate (MRR), latent heat ratio (LHR), and heating capacity (qheat) of the DC-HE is analyzed, the effects of these variables on the sensible and latent heat transfer rates are discussed. Finally, the optimal variables for maximizing MRR and LHR are determined using the response surface method and multi-objective genetic algorithm. When the inlet air temperature, relative humidity, cooling-side water temperature, heating-side water temperature, cooling-side water flow rate, heating-side water flow rate, and air flow rate are 11.8 ℃, 95 %, 3 ℃, 30 ℃, 2 m/s, 2 m/s, and 2 m/s, respectively, the DC-HE achieves an MRR of 1.58 g/s, an LHR of 62.2 % and a qheat of 9.99 kW. Compared with other finned tube heat exchangers, the DC-HE enhances the moisture removal capacity and significantly reduces the temperature requirement for the heat source, offering a promising dehumidification and heating technology for greenhouse applications.

Investigations of Silica/MOF composite coating and its dehumidification performance on a desiccant-coated heat exchanger

Desiccant materials have an important impact on the dehumidification performance of desiccant-coated heat exchanger (DCHE). In this paper, a desiccant-coated heat exchanger based on a composite desiccant material of metal organic frameworks (MOFs) and silica gel was proposed. The coating was experimentally prepared and tested for its hygroscopic performance under different binder types (PVP, PVA, and PVB), different binder mass concentrations, and different MOF mass concentrations in the composite adsorbent. Further simulations were performed to investigate the effects of key structural and operational parameters on the performance of DCHE. Experimentally, the optimal hygroscopic performance of the composite adsorbent was obtained at 15 wt% PVP and 20 wt% MOF, which was 51.71 % higher than that of silica coating, and the cost of the composite adsorbent drops 78.04 % by comparing to the pure MOF for laboratory fabrication, and based on the novel economic efficiency index proposed in this paper, the mass concentration of the MOF should not exceed 32.8 wt%. Simulation results showed that under the conditions as follows: 1.2 mm (fin spacing), 25 mm (fin height), 0.28 mm (coating thickness), 25 °C (cooling water temperature), and 0 % (initial moisture content), the corresponding moisture removal capacity (MRC) and of DCHE was 6.740 g/kg, which was 149.63 % higher than that of silica coating.

Experimental assessment of the energy performance of a renewable air-cooling unit based on a dew-point indirect evaporative cooler and a desiccant wheel

Given the escalating energy consumption in cities worldwide, it is crucial to investigate the utilization of sustainable technologies and renewable energy sources. The number of empirical studies on the energy performance of hybrid air-cooling systems is limited. Therefore, the objective of this work is to experimentally study the energy performance of a novel renewable air-cooling unit. This prototype is mainly composed of a desiccant wheel and a dew-point indirect evaporative cooler to independently control the temperature, humidity, and carbon dioxide levels of indoor air. 64 experimental tests are carried out to fit an empirical model of this renewable air-cooling unit, focusing on outlet air conditions and the coefficient of performance. In addition, several performance indices are developed for desiccant wheel and dew-point indirect evaporative cooler: (i) moisture removal capacity; (ii) moisture removal capacity per unit of electrical power-consumption; (iii) dew-point efficiency and (iv) cooling capacity of dew-point indirect evaporative cooler per unit of electrical power-consumption. The highest values of dehumidification capacity, sensible cooling capacity and coefficient of performance for this renewable air-cooling unit are achieved for the most severe outdoor air conditions, namely 19.02 kg·h−1, 21.49 kW and 11.0, respectively. This work can serve as a reference for research on the feasibility of hybrid air-cooling systems in the scenarios of heat events and climate change world.

Comprehensive assessment of drying performance, physical characteristics, bioactive compounds, and antioxidant capacity of mallow (Malva verticillata) vegetables: A comparative study of a modified tray dryer and conventional drying methods

Drying vegetables in a suitable dryer is an imperative concern in the food-processing sector. To address this issue, a cabinet-type tray dryer has been developed by modifying its design, employing a comprehensive approach ensuring uniform air velocity and temperature in all the trays, and naming it a modified tray dryer (MTD). A comparative analysis of drying performance, physical characteristics, functional attributes, and antioxidant capacity of mallow (Malva verticillata) vegetables dried in MTD and existing three drying methods such as sun, shade, and traditional cabinet drying was accomplished. The performance evaluation study revealed that MTD demonstrated a faster moisture removal capacity and required less drying time compared to other drying methods. Statistical analysis revealed that drying methods had a significant (p < 0.05) impact on the physical properties, functional qualities, and bioactive functions of the dried mallow powder (MP). The higher chlorophyll content (27.41 ± 0.84 mg/100 gm of dry matter, DM), total phenol content (15.71 ± 0.95 mg GAE/g DM), and DPPH activity (8.82 ± 0.81 mg TEAC/g DM) were noticed in the mallow vegetable powder dried in MTD than shade, sun and traditional cabinet drying methods. A slightly lower value (statistically insignificant) of ascorbic acid content (9.64 ± 0.78 mg/100 gm DM) and total flavonoid (1.44 ± 0.05 mg QE/g DM) was achieved in contrast to other drying methods. The antioxidant capacity of the analyzed data was lowest for shade drying compared to other drying methods, while MTD exhibited the highest capacity. Therefore, this study might assist in selecting a suitable dryer for drying vegetables. The findings suggest that MTD can be an alternative drying technique as a quicker drying technique and for obtaining better-quality dried products in terms of antioxidant and functional properties than the traditional and existing process of vegetable drying.

Effect of polyvinylpyrrolidone and lithium chloride composite desiccant-coated heat exchangers on dehumidification studies

Cooling systems are necessities that remain energy intensive, particularly in tropical regions with elevated humidities and temperatures. Conventional vapor-compression air-conditioners are often inefficient because the sensible and latent heat loads are intrinsically coupled. To realize more energy-efficient cooling, solid desiccant-coated devices can be introduced to mitigate the latent heat load. Among such devices, desiccant-coated heat exchangers (DCHEs) are attractive for enabling nearly isothermal dehumidification. Hence, desiccants with high sorption capacity and rapid kinetics are essential. Solid polymeric desiccants are well-positioned to meet these requirements but comprehensive studies on the dehumidification performance of solid polymeric desiccant-coated heat exchangers are currently lacking. In this study, we investigated the potential of polyvinylpyrrolidone (PVP) and lithium chloride (LiCl) composites as desiccant materials at both material and system levels in terms of gravimetric water uptake. Specifically, LiCl is a hygroscopic salt bound by the moisture-sorbing PVP matrix. This work also demonstrates how the Elovich model accurately predicted the PVP-LiCl composite’s sorption kinetics. The results show that the optimum PVP-LiCl composite ratio is 66.7 wt%, with an equilibrium sorption capacity of 280 % at 75 % RH and 25 °C, compared to 29 % for silica gel under the same condition. With much superior sorption kinetics and capacity, the PVP-LiCl-coated prototype heat exchanger demonstrated a moisture removal capacity eight times higher than a silica gel-coated one under dynamic flow towards energy savings in air-conditioning systems.

Theoretical study on the dehumidification behaviors of dual-desiccants coated cross-flow heat exchanger with staged adsorption-desorption process

The conventional desiccant coated heat exchangers (DCHEs) suffer from the inefficient utilization of regenerative energy and the inadequate dehumidification capacity of a single desiccant. In this study, a concept of dual-desiccants cross-flow DCHE with staged adsorption-desorption process was proposed to strengthen dehumidification capacity and energy efficiency simultaneously. In order to guide the construction of proposed DCHE, the steady-state dehumidification capacity of single-desiccant (specifically, silica gel, FAM Z01, FAM Z05 and EMM-8) cross-flow DCHE was investigated by thermodynamic analysis. The dual-desiccants cross-flow DCHE was thus constructed, and its numerical model was established to investigate the dehumidification characteristics. Theoretical analysis revealed that single-desiccant cross-flow DCHEs exhibit different optimal relative humidity ranges for dehumidification. The minimum regeneration temperature driving dehumidification cycle increases as the lower supply air humidity is required. Numerical results demonstrated that the staged adsorption process ensures a large dehumidification capacity across a wide humidity range, including low humidity conditions. Meanwhile, the staged desorption process facilitates the cascade utilization of energy and the direct recovery of regenerative waste heat. For dual-desiccants cross-flow DCHE utilizing silica gel and EMM-8, the moisture removal capacity and dehumidification coefficient of performance can reach 0.012 kg/kg and 0.41, respectively.

Development of rotary dehumidifier with silica-gel-based composite desiccant

The desiccant dehumidification system's key component, the desiccant wheel, can perform effectively using composite desiccant materials. Evaluation of the desiccant wheel's performance using composite desiccant material is the primary goal of this study. Authors have compared the performance of two desiccant wheels; one is packed with traditional Silica-gel, and the other is a composite of Silica-gel and calcium chloride in a ratio of 3:2 by weight. A rotary wheel is developed with rectangular channels parallel to the wheel's axis. The novelty of this research lies in the improved design of the desiccant wheel. Unlike other techniques involving pressure losses and ineffective space utilization, this design offers better space utilization and fewer pressure losses. In addition, wheel fabrication is less costly and easily reusable with other desiccants. Three performance indicators were evaluated through experimentation: dehumidification capability, moisture removal capacity, and dehumidification coefficient of performance. Results show that the Parallel channel desiccant wheel achieves 25% higher dehumidification capability and 55% greater moisture removal capacity. The specific humidity of the air is reduced by 35% using the composite desiccant wheel. Comparing the composite desiccant to traditional Silica-gel, its dehumidification coefficient of performance is 40% higher.

Investigation on recirculated regenerative solid desiccant-assisted dehumidification system: Impact of system configurations and desiccant materials

Desiccant wheels (DWs) have emerged as highly promising alternatives for achieving efficient dehumidification, low-carbon and energy-saving initiatives. The present work aimed to determine the optimal system configuration for dehumidifying enclosed spaces using a DW-based system with the recirculated regeneration of process air based on modelling investigation, which has been validated with experiments. Three distinct configurations of this DW-based system were compared. The impact of operational parameters and desiccant materials on the system dehumidification capacity (Dtot) and energy efficiency was thoroughly analyzed. The results indicate that the posterior diversion of regeneration air was most preferable for improved dehumidification performance, enhancing the Dtot and the improvement of moisture removal capacity (ΔMRC) by 3.7 % and 42.8 %, respectively. Moreover, posterior diversion emerged as a compelling option for energy conservation as it reduced the energy consumption by 13.3 %. Furthermore, six different desiccant materials were compared, and it was found that the synthesized metal silicate material was most suitable for the proposed systems, improving the optimal ΔMRC by 32.2 %. Furthermore, a strong correlation was identified between the maximum adsorption capacity and the proposed system performance. Overall, these findings aid in developing a promising method for enclosed space dehumidification and cooling.

Optimized geometric designs of desiccant wheels with metal-organic frameworks considering dehumidification capacity and energy

With the increasing demand for handling dehumidification loads and energy savings in air-conditioning systems, solid-desiccant dehumidification systems have been implemented in passive and zero-energy buildings. Although novel metal-organic frameworks (MOFs) have been introduced to improve the performance of desiccant wheels, previous studies have mainly focused on silica gel-based desiccant rotors (DRs). This study aimed to optimize the geometric design of MOF DRs to achieve enhanced dehumidification and energy performance. A numerical model for estimating the performance characteristics of MOF DRs was developed using the adsorption isotherm curves measured in this study. The numerical model was validated by comparing the predictions with the experimental data. The dehumidification and energy performance of the MOF DRs were analyzed in terms of the coating amount, channel pitch, rotor thickness, and process-regeneration area ratio. Accordingly, the optimized geometric designs of the MOF DRs were determined to achieve the maximum dehumidification capacity and minimum energy consumption. Compared to the baseline MOF DR, the capacity-optimized MOF DR exhibited a 47.4 % higher moisture removal capacity, whereas the energy-optimized MOF DR exhibited a 48.6 % lower sensible energy ratio.

Performance evaluation of a rotary dehumidifier with molecular sieve desiccant using coupled regeneration mode: Experimental investigation

The increasing demand for energy-efficient and environmentally friendly air conditioning systems has led to the development of innovative technologies such as desiccant cooling systems. This study presents a comprehensive experimental analysis of the dehumidification and thermal performance of a rotary dehumidifier with molecular sieve desiccant designed to effectively remove moisture from the air by utilizing coupled regeneration mode (complete waste heat liberated out of condenser and electric rod heat). Various experiments were conducted to investigate different performance parameters including moisture removed from air by adsorption, moisture added to air by regeneration, dehumidification effectiveness, regeneration effectiveness, moisture removal capacity (MRC), regeneration rate (RR) at different process air inlet temperatures ranging (28–34 °C) and at different regeneration air inlet temperatures ranging (55–62 °C). These experiments were conducted at same air velocity for both adsorption and regeneration segments of rotary solid desiccant wheel using molecular sieve. The results showed that the performance of the desiccant wheel was affected by inlet temperature and humidity ratio for adsorption and regeneration segments. The findings emphasize the system's ability to provide efficient dehumidification and cooling while simultaneously promoting sustainable energy practices. Moreover, the waste heat recovery system significantly contributes to the overall efficiency improvement of the rotary dehumidifier with molecular sieve desiccant, making it an environmentally friendly alternative to conventional air conditioning technologies.

Membrane-based packed-sheet liquid desiccant dehumidification system

Humidity control plays a vital role in both buildings and greenhouses. The thermally-driven liquid desiccant dehumidification systems are getting an increasing traction because of their high moisture removal capacity and the possibility of their integration with waste-heat or renewable energy sources. In this work, a novel design concept for liquid desiccant dehumidification systems is proposed to overcome the practical challenges of the conventional systems, such as solution carryover, crystallization, and corrosion. The presented system utilizes a compact “packed-sheet” sorption bed that houses spherical membrane-based micro-absorbers with LiBr as a liquid desiccant. A bench-scale system is designed and tested under the typical dehumidification working conditions. The experimental results showed that the proposed design has up to two-fold higher moisture removal rate per volume (MRR = 75 g/s-m3) than a conventional LiBr liquid desiccant dehumidification system (MRR = 35 g/s-m3). In addition, a one-dimensional coupled heat and mass transfer mathematical model is developed to simulate the transient behavior of the proposed system. An optimization study, using the validated model, suggested that the performance of proposed design can be maximized to realize moisture removal rates of up to 135 g/s-m3 (270% higher than the conventional liquid desiccant systems) with a coefficient of performance of 0.25.

Techno-economic and emission analysis of solar assisted desiccant dehumidification: An experimental and numerical study

In humid climates, it is challenging to maintain moisture content in the air for human thermal comfort and industrial applications. Commercial dehumidifiers rely on conventional electric heaters to regenerate desiccant material, which accounts for significant energy consumption by such dehumidifiers. As a green solution to this problem, the present study integrates a flat plate solar air collector (FPSAC) with a desiccant dehumidifier to effectively use solar thermal energy and reduce electrical consumption. Performance evaluation of glazed and unglazed FPSAC-assisted desiccant dehumidifier has been conducted at process air flow rates of 33, 51 and 62 m3/h with a constant regeneration flow rate of 42 m3/h. Both glazed and unglazed FPSAC assisted desiccant dehumidification systems had the highest dehumidification effectiveness and percentage increase in temperature at the flow rate of 33 m3/h, while the highest moisture removal capacity was at 51 m3/h. Maximum dehumidification effectiveness, percentage temperature increase, and moisture removal capacity for the glazed case were 0.4, 66.67%, and 6.14 kg/h, respectively. Experimental results showed that the glazed FPSAC-integrated desiccant dehumidification system outperforms unglazed FPSAC in all performance evaluation parameters. Using Transient System Simulation software (TRNSYS), the proposed glazed and unglazed assisted desiccant dehumidification system was modeled and validated with experimental results. Furthermore, a techno-economic analysis of the solar hybrid desiccant dehumidification system has been carried out. The FPSAC used in this study showcased a 33.57% yearly solar fraction with a solar hybrid system having a payback period of 4.23 years. In addition, the hybrid system can reduce greenhouse gas emissions yearly by 0.352 tons of CO2 equivalents.

Desiccant coated fin tube energy exchanger design optimization implementing KNN-ML tool and adsorption/desorption kinetics analysis using finite difference based transient model

In air conditioning applications, to increase energy exchange capabilities and enhance indoor air quality, the desiccant coated fin tube energy exchanger (DCFTE) appears to be a capable substitute compared to traditional energy exchangers like an adsorber bed and rotary wheel. Hence, for enhancing the air conditioning system's performance, accurate prediction of the adsorption kinetics of DCFTE is crucial. Thus, a K-Nearest Neighbor-Machine Learning (KNN-ML) tool is employed for predicting the exit and design parameters of DCFTE. The impact of the operating parameters on the performance of DCFTE has been assessed by utilizing the KNN-ML tool. To analyze the performance of DCFTE, energy exchange and dehumidification capacity are selected as the performance indices. The optimum operating conditions for a specific operational range are also found using the KNN-ML tool. Moreover, a finite difference approach-based transient model is developed to assess the inlet parameters' effect on the performance characteristics and adsorption/desorption kinetics of DCFTE. The coefficient of performance and moisture removal capacity are selected as the performance indices. Furthermore, the effect of time on the outlet air specific humidity, outlet water temperature, air temperature, and desiccant concentration during the dehumidification and regeneration process is analyzed. The effect of the water vapor partial pressure ratio on adsorption capacity is examined. Moreover, Lewis and Stanton number's influence on the DCFTE performance is analyzed by employing the transient model. Silica gel is utilized as a desiccant.

Experimental Investigation on the Performance of a Dehumidifier Constructed from a Water-to-Air Heat Exchanger Coated with Composite Desiccant of Mesoporous Silica Gel and LiCl

Thermal environment in buildings in hot climate is conditioned for comfort by air-conditioning that is energy intensive. Presently, most air-conditioning systems in Thailand and other countries in Southeast Asia use electricity-driven vapor compression systems to cool down the air to the set-point temperature. However, latent load due to condensation of air humidity forms a large part of the air-conditioning load. This paper presents the results of experiments on a dehumidifier constructed from a water-to-air heat exchanger coated with a composite desiccant of large-pore mesoporous silica gel and LiCl, regenerated by low-temperature hot water. Moisture removal capacity (MRC), dehumidification capacity (DC), thermal coefficient of performance (COPth), and an equivalent air conditioning load of dehumidification (EALD) are comparative quantitative parameters derived from experimental results and are studied in this research. The composite desiccant requires low-temperature water for regeneration and offers a higher rate of vapor adsorption and desorption that leads to a shorter required desiccant dehumidification cycle time. The results demonstrate that the dehumidifier is able to effectively reduce moisture in ventilation air and substantially reduces the cooling load of air-conditioning.

Experimental evaluation of a 3D printed air dehumidification system developed with green desiccant materials

Energy-efficient dehumidification systems are necessary to reduce energy consumption and CO2 emissions into the atmosphere. Desiccant systems could be an alternative to conventional air dehumidification systems based on direct-expansion units. In the present work, the main objective was to develop and experimentally evaluate a 3D printed desiccant system manufactured using green desiccant materials. Hence, the adsorbent capacity of three 3D printed desiccant materials were studied: polylactic acid (PLA), pine wood with PLA (PW-PLA) and olive pit with PLA (OP-PLA). The results showed that PW-PLA was the material with the highest adsorption capacity of those analysed, up to 12.7 % higher than OP-PLA. A fixed bed desiccant system was fabricated using PW-PLA filament and its latent energy performance was investigated under different inlet air conditions and low regeneration temperature, 50 °C. The evaluation of the energy performance of the 3D printed desiccant system revealed adequate moisture removal capacity values, up to 30 g/sm3, with low pressure drop, less than 552 Pa. These results show the promising potential of 3D printing and green desiccant materials for manufacturing ecological air dehumidification systems.

Performance investigation and exergy analysis of a novel recirculated regenerative solid desiccant dehumidification system

Vapor compression dehumidification (VCD) is limited by the wet-bulb temperature, which results in high-energy consumption, especially in enclosed hot and humid spaces. An improved recirculated regenerative solid desiccant-vapor compression (RRSD-VC) hybrid dehumidification system was proposed to achieve highly efficient dehumidification in enclosed cabins, such as those in marines, spacecraft, and underground shelters. An experimental study of the RRSD-VC system was carried out to analyze the dehumidification characteristics and exergy performance. The results indicate that the regenerative airflow ratio (γ) was the most crucial performance indicator of the proposed system. The system moisture removal capacity (Dtot) increased with decreasing precooling temperature and increasing regeneration air temperature, and the highest Dtot was obtained when the optimal γ was reached. The exergy efficiency of the RRSD-VC system (ηex) was inversely proportional to γ. Therefore, a balance of high dehumidification capacity and low energy consumption could be maintained in the system design. Moreover, ηex could be improved by 55.7% when the electric heating was replaced by heating with waste heat recovered from the engine exhaust gas for air regeneration. The results of further parametric analysis showed that the RRSD-VC system was more adaptable than the VCD system to hot and humid conditions.

Performance characteristics of desiccant rotor using metal organic framework material

A desiccant rotor is often adopted for dehumidification applications, owing to the increased importance of humidity control and energy saving in air conditioning and ventilation systems for buildings. In previous studies, silica gel, zeolite, and silica composites have been widely used in the desiccant rotor. However, it is difficult to further improve the dehumidification performance of a conventional desiccant rotor, owing to the inherent limitations of the desiccant material. In this study, a desiccant rotor using a metal organic framework (MOF) material was proposed and manufactured to improve the dehumidification performance under various operating conditions. The dehumidification and regeneration performance of the MOF desiccant rotor were measured and analyzed by varying the temperature, humidity, volumetric flow rate of the process air, and temperature of the regeneration air. Furthermore, the performance of the MOF desiccant rotor was compared to that of a conventional silica composite desiccant rotor. The MOF desiccant rotor showed 53% lower sensible energy ratio and 139% higher specific moisture removal capacity than the conventional desiccant rotor. In addition, empirical correlations were developed for performance predictions for the MOF desiccant rotor.

Performance and design analyses of various configurations of dew point evaporative cooling-based desiccant air-conditioning (DAC) systems for hot and humid conditions

Thermally driven desiccant- and evaporative cooling-based technologies are promising greener and cheaper alternatives to compressor-based systems due to the separate handling of latent and sensible loads. Desiccant air-conditioning (DAC) systems comprise a desiccant dehumidifier, a sensible cooling unit, a heat source for regeneration, and a heat recovery unit. These components of a DAC system can be arranged in various ways to give different configurations with varying advantages and disadvantages. In this study, five configurations of thermally driven desiccant dehumidifier- and dew point evaporative cooling (DPEC)-based DAC systems were investigated. Seven evaluation criteria namely regeneration temperature, desiccant moisture removal capacity, COPt, DPEC L/H, heat exchanger UA, system size, and fan power requirement were employed. Results show that the standard cycle in ventilation mode offers the highest COPt despite having the highest regeneration temperature. Recirculation of the return room air can operate at a significantly lower regeneration temperature at the expense of larger equipment size and much lower COPt. DAC with an internally cooled dehumidification can operate at low regeneration temperature at the expense of higher fan power and slightly lower COPt. Dividing the dehumidification process into two stages can offer operation at moderately lower regeneration temperature without severely affecting the other criteria. This study can serve as a guide for the selection of an appropriate DAC configuration for space cooling depending on the objective criteria and the resources available.