Water Vapor Adsorption Research Articles

Equilibrium and Hysteresis Formation of Water Vapor Adsorption on Microporous Adsorbents: Effect of Adsorbent Properties and Temperature

Water vapor has been one of the vital problems in purification of volatile organic compounds. In this study, the adsorption-desorption equilibrium of water vapor were conducted at 298, 308, 318 and 328K on three adsorbents: hypercrosslinked polymeric adsorbents (HPA), activated carbon fiber (ACF) and granular activated carbon (GAC). The obtained isotherms were type V and the adsorption capacity at the same condition was as follows: GAC>ACF>HPA. Cluster Formation Induced Micro-pore Filling (CIMF) model was adopted to fit the adsorption isotherms and the fitting parameters showed that adsorption capacities of water vapor on micropores and functional groups had a negative logarithmic linear relationship with temperature. The existence of functional groups could weaken the negative influence of temperature on the water adsorption performance, while the influence of temperature had negligible relationship with microporous volume. The hysteresis loops at different temperatures on three adsorbents had similar shape, the size of which were also as follows: GAC>ACF>HPA. They mainly occurred in micropore adsorption, but their size had positive relationships with both functional groups and microporous volume. The hysteresis became smaller along with the increase of temperature, closely related with the stability of water clusters. In conclusion, temperature, functional groups and porous structure played crucial roles for water vapor adsorption and the formation of hysteresis.

Insights into optimized synthesis conditions of hollow microspheres of silica for water vapor adsorption

Hollow microspheres of silica were synthesized with different ethanol/water ratios (0.4, 1.0, 2.0 and 6.0) to assess the influence of this parameter on the morphology/porosity of the samples and thus on their water adsorption capacity. The samples were characterized by N2 at 77 K and CO2 at 273 K adsorption isotherms, scanning electron microscopy, transmission electron microscopy and water vapor isotherms at 298, 313 and 328 K. The textural properties of the samples were slightly different: as the ethanol/water ratio increases, the pore volume and specific surface area decrease and the structure of the samples evolves into a well-defined spherical arrangement. In addition, water adsorption capacity of the samples was similar to that of commercial adsorbents used for gas drying at high relative pressures, but significantly lower at low relative pressures. Moreover, varying of the ethanol/water ratio did not lead to a noticeable improvement in the water adsorption capacity at low relative pressures and hence these samples are not suitable for deep gas drying. On the other hand, as they require less energy to be regenerated, HMS are alternatives to be considered in less demanding situations, such as coarse drying and water harvesting from air.

Graphene wettability control: Texturing of the substrate and removal of airborne contaminants in the atmosphere of various gases

Experimental and theoretical studies on the wettability of graphene coating are carried out. Molecular dynamic modeling is used to structure water molecules on the surface of copper and graphene-copper, as well as to assess wettability. The instability of the properties of graphene coatings over time is one of the reasons that inhibit their widespread use as highly sensitive sensors. The adsorption of water vapor and airborne contaminations on the graphene surface leads to a change in the electrical properties of the coating. The influence of key parameters (copper recrystallization, copper oxidation due to graphene surface defects, wall textures and airborne contaminations) on the wettability of the graphene coating is investigated for the first time. It is shown that the predominant effect on the change in wettability is exerted by hydrocarbon impurities. Molecular dynamic modeling demonstrates that an insignificant local separation of copper, as well as an inhomogeneous graphene coating, increases the angle on the graphene coating from 25 to 30° to 60-65°. To remove the hydrocarbon layer, annealing is carried out in a wide temperature range, as well as in the atmosphere of argon and hydrogen. A comparison of various methods of removing impurities is carried out. After prolonged annealing, the contact angle of the drop decreases from 80 to 90° to 55°.

Experimental investigation into simultaneous adsorption of water vapor and methane onto shales

Methane is the main component of natural gas and a greenhouse gas. It usually coexists with water in geological formations. Methane adsorption onto shale has been studied extensively, but there is no report on the Simultaneous Adsorption of Water vapor and Methane (SAWM). This paper reports a new experimental method for studying SAWM onto shale. During the experiment, liquid water, water vapor and methane coexist in an adsorption cell. Water vapor is produced via evaporation of liquid water, and the processes of liquid water evaporation and water vapor and methane adsorption onto shale occur simultaneously. The rate of liquid water conversion into vapor and the free water vapor content in the gas mixture depend on Relative humidity (Rh). Changes in Rh are monitored with a humidity-sensor. In SAWM, the amount of water vapor adsorbed greatly exceeds that of methane. The adsorption of water vapor took longer to reach equilibrium than that of methane. The amount of water vapor adsorbed at equilibrium decreased with total pressure, while the opposite situation occurred with methane adsorption. Compared to Pure Methane adsorption onto Dry Shale (PMDS), the amount of methane adsorbed was lower by 10–59% in SAWM. The equilibrium time for methane adsorption was higher, and t50 and t80 (t50 and t80 represented the times required for adsorption of 50% and 80% of the equilibrium adsorption amount, respectively) increased 12.0–108.0 and 9.0–115.2 times, respectively. In the two experiments, the declines in the level of methane adsorption were equal when a critical threshold Equilibration Degree (Ed) was reached. Before reaching Ed, the rate of methane adsorption in SAWM was higher than that in PMDS. After reaching Ed, the phenomenon was reversed.

Factors Influencing the Kinetics of Water Vapour Adsorption on Activated Carbons

The performance of porous carbon materials as sorbents is often compromised by the presence of humidity. Studying the kinetics of water vapour adsorption on activated carbons will undeniably help to overcome this issue. This has been approached in this work by evaluating the influence of several operational factors on the dynamic adsorption of water vapour in these materials. Specifically, different carbon types, particle sizes, air flows and ambient conditions (temperature and relative humidity (RH)) were systematically investigated. The impact of each isolated parameter on both the maximum water uptake and the uptake rate was analyzed by fitting the experimental data to the Linear Driving Force (LDF) kinetic model. The results show that except for the particle size, the studied variables play a role in the water sorption kinetics, although to a different extent. It was also confirmed that the LDF model can adequately describe the kinetics of water vapour adsorption independently of the experimental conditions. Finally, the complete water vapour adsorption process can be described by this model, obtaining a different value of the kinetic constant for the sequential stages, involving different adsorption mechanisms.

Chemically Stable Carbazole-Based Imine Covalent Organic Frameworks with Acidochromic Response for Humidity Control Applications.

Isoreticular chemically stable two-dimensional imine covalent organic frameworks (COFs), further denoted as DUT-175 and DUT-176, are obtained in a reaction of 4,4′-bis(9H-carbazol-9-yl)biphenyl tetraaldehyde with phenyldiamine and benzidine. The crystal structures, solved and refined from the powder X-ray diffraction data and confirmed by high-resolution transmission electron microscopy, indicate AA-stacked layer structures. Both structures feature distorted hexagonal channel pores, assuring remarkable porosity (SBET = 1071 m2 g–1 for DUT-175 and SBET = 1062 m2 g–1 for DUT-176), as confirmed by adsorption of gases and vapors. The complex conjugated π system of the COFs involves electron-rich carbazole building units, which in combination with the imine groups allow reversible pH-dependent protonation of the frameworks, accompanied by charge transfer and shift of the absorption bands in the UV–vis spectrum. The sigmoidal shape of the water vapor adsorption and desorption isotherms with a steep adsorption step at p/p0 = 0.4–0.6 in combination with excellent stability over dozens of adsorption and desorption cycles ranks these COFs among the best materials for indoor humidity control applications.

Study of hygroscopic behaviour of spruce during adsorption and desorption

Sorption of water vapour in hygroscopic porous materials is associated with latent heat release and absorption. This phenomenon should be taken into account to achieve a better understanding of the coupled transfer of vapour and heat in hygroscopic porous materials. In this paper, water vapour adsorption and desorption in the longitudinal direction of spruce samples are studied. Neutron radiography is used to measure changes in moisture content and wireless thermocouples are used to measure temperature changes. During the adsorption and desorption experiments, large changes in moisture content and temperature are observed. A hygrothermal model is developed to simulate vapour and heat transfer during adsorption and desorption experiments. Generally, the numerical model predicts well the measured moisture and temperature changes. The large moisture change is due to the low vapour resistance factor in the longitudinal direction of the spruce samples. The latent heat associated with vapour adsorption is the cause of the large temperature changes. It was found that vapour permeability affects both vapour and heat transfer, while thermal conductivity only affects heat transfer.

Hydrophobic-to-hydrophilic affinity change of sub-monolayer water molecules at water–graphene interfaces

Investigating the interfacial properties between water and graphene is important, as the water–carbon interface influences various applications. Graphene is the fundamental unit of various carbon allotropes and composed of a single atomic species, although slight oxygen groups are normally attached on it. Therefore, adsorption properties on graphene is inevitable to advance fundamental understating on surface sciences. However, the detection of water adsorption on graphene is considerably hard, because amount of water is tiny and mass production of graphene to a detectable level using a standard adsorption apparatus is extremely difficult. We succeeded to detect water vapor adsorption on several layer graphene using lab-made adsorption apparatus with a quartz crystal microbalance technique. This study derives the properties of water on single-, triple-, and six-layer graphene from the contact angles of water droplets and the water vapor adsorption isotherms. The surface hydrophobicity evaluated from the contact angles and water vapor adsorption isotherms decreased in the following order: single-layer graphene > triple-layer graphene > six-layer graphene. At a relative pressure of 0.4 and water surface densities of 0.5–1.5 mg m −2 (corresponding to 2–5 water layers), the water stability was 1.0 kJ mol −1 smaller on single-layer graphene than on triple- and six-layer graphene. The weak interaction between water molecules and single-layer graphene induced slight water adsorption on graphene. As the water amount increased, the water–graphene interaction energy increased with steps of 0.17–0.18 mg m −2 (corresponding to nearly 50% of a water monolayer), and the water structure correspondingly transformed from cluster to layer. The structure transformation of adsorbed water induced the affinity change from hydrophobic to hydrophilic on graphene interfaces. The mechanism of water–graphene interfaces can be exploited in applications of graphene-based carbon nanomaterials. • Water contact angles of graphene were 57–80°, indicating hydrophobic interfaces. • Water vapor on single-layer graphene was rarely adsorbed below P/P 0 = 0.4. • Water-adsorbed structure was changed from cluster to layer form at 0.5 water layer. • Cluster-to-layer transformation triggers affinity change of water on graphene.

Novel insights into diethylamine catalytic combustion over CuO catalysts supported by SSZ-13: Undesirable product NOx as a crucial intermediate for N2 generation

Catalytic combustion of nitrogen-containing volatile organic compounds (NVOCs) could effectively control N2 generation rather than NOx, but its mechanism is still not well answered. Herein, a series of CuO supported by SSZ-13 catalysts (denoted as Cu/S) were prepared for the catalytic combustion of diethylamine (DEA), a typical NVOCs. The effects of CuO loading and calcined temperature of catalysts on the catalytic performance were investigated. Among the Cu/S catalysts, the 10CuO/S-450 catalyst exhibits the highest oxidation activity (lowest T99 of 240 °C), and widest temperature window (△T = 120 °C) for high N2 selectivity (>99%). This result is ascribed to its highest ratio of easily reduced CuO active species. Importantly, there are two important steps for DEA combustion (I: catalytic oxidation to NOx; II: selective catalytic reduction of NOx with DEA to N2). Selective catalytic reduction of NOx with DEA is the very crucial pathway for N2 generation. The easily reduced CuO species play crucial roles on both catalytic oxidation and selective catalytic reduction. In addition, water vapor (5 vol.%) slightly improved oxidation activity of DEA, and increased N2 selectivity at high temperature (>350 °C), but the catalytic oxidation activity of intermediate CO was decreased caused by the competitive adsorption of water vapor.

Experimental study on desiccant evaporative combined chilled air/chilled water air conditioning systems

• A desiccant evaporative combined chilled air/chilled water systems was proposed. • The dynamic characteristics was presented by experimental investigation. • The temperature of the chiller air and the chiller water is below 20℃ and 18℃. • Regeneration temperature and air–water ratio have great impacts on performance. • 70 °C regeneration temperature was recommended in high humidity regions. Evaporative cooling technology is limited by the environmental wet-bulb temperature and is not suitable for humid climates. Desiccant wheels adsorb water vapour, thereby converting high-humidity air into low-humidity air, and they can be regenerated by solar energy or waste heat. In this study, a desiccant evaporative combined chilled air/chilled water air-conditioning system is proposed. The proposed system integrates a desiccant wheel air conditioning system and a direct-evaporative cooler, which can be used for temperature and humidity independent control systems in humid climates. An experimental setup was built and used to test the system performance and important system parameter effects under moderate temperature and humidity (32 °C, 60% RH), moderate temperature and high humidity (32 °C, 80% RH), and high temperature and humidity (36 °C, 80% RH). The results indicated that for the system at a regeneration temperature of 70 °C, the chilled air temperature was lower than 20 °C, the chilled air humidity ratio was lower than 13 g/kg, and the chilled water temperature was lower than 18 °C, which meets the temperature and humidity independent control requirements.

Large-Area Fabrication of Structurally Colored and Humidity Sensitive Composite Nanofilm via Ultrasonic Spray-Coating.

Intelligent structural colors have received extensive attention in recent years due to their diverse applications. However, the large-area, uniform, and cost-effective fabrication of ultra-thin structural color films is still challenging. Here, for the first time, we design and employ an ultrasonic spray-coating technique with non-toxic, green nano-silica and polyvinylpyrrolidone as raw materials, to prepare structural color films on silicon wafers. Due to the addition of polyvinylpyrrolidone, the coffee-ring effect during droplet drying is suppressed and uniform composite films are formed. We further perform a detailed study of the influence of various processing parameters including silica/polyvinylpyrrolidone concentration, substrate temperature, nozzle-to-substrate distance, and number of spray-passes on film roughness and thickness. By increasing the number of spray-passes from 10 to 30, the film thickness from 120 to 340 nm is modulated, resulting in different colors, and large-area and uniform colors on commercial round silicon wafers with 15 cm diameter are achieved. The silica/polyvinylpyrrolidone composite films show strong hydrophilicity and are sensitive to humidity changes, leading to quickly tunable and reversible structural colors. Quartz crystal microbalance with dissipation demonstrates water vapor adsorption and condensation on the nanofilm when increasing environmental humidity. Thereby, ultrasonic spray-coating as a novel film fabrication technique provides a feasible scheme for large-area preparation of intelligent structural colors.

High-temperature selective catalytic reduction of NO with NH3: Optimization of ZrO2 and WO3 complex oxides

The catalyst for selective catalytic reduction of NOx at high temperatures is significantly demanded by current gas-fired exhaust purification. In this work, the complex oxides composed of two different structures of ZrO2-WO3 and WO3/ZrO2 with zirconium as the main component were prepared for NH3-SCR of NO at high temperatures by blending method and equal volume impregnation method, respectively. Combined with XRD, NH3-TPD, FE-SEM, BET and in situ DRIFTS characterization, the effects of component optimization of two kinds of ZrO2 and WO3 complex oxides on the performance for NH3-SCR of NO were mainly studied. The optimal compatibility of ZrO2 and WO3 complex oxides was determined, and the corresponding N2 selectivity and anti-interference ability of water vapor and SO2 were further investigated. Results showed that the performance of ZrO2-WO3 prepared by blending method for NH3-SCR of NO was significantly better than that of WO3/ZrO2 prepared by impregnation method. The ZrO2-WO3 containing 20% WO3 has the best performance in NH3-SCR of NO with NO conversion higher than 90% and N2 selectivity higher than 90% at 450–650 °C, and the performance was not affected by SO2, slightly affected by competitive adsorption of water vapor at 450 °C and not disturbed by water vapor above 500 °C. Further investigation showed that the NH3-SCR of NO over the ZrO2-WO3 reaction followed both L-H and E-R mechanisms. Characterization analysis revealed that ZrO2-WO3 has finer microscopic particles, larger specific surface area, higher acid amount and stronger acid strength than WO3/ZrO2.

Hybrid super-porous hydrogel composites with high water vapor adsorption capacity – Adsorption isotherm and kinetics studies

Water vapors adsorption capacity of deliquescent salts is very high, but they dissolve in the adsorbed water by forming crystalline hydrates which restricts their use in different water vapor adsorption applications. This limitation can be overcome by incorporating deliquescent salts within a polymer matrix which will keep the salt solution in place. Furthermore, if the polymer matrix used is also capable of adsorbing water vapor, it will further improve the overall performance of desiccant systems. Therefore, in this work, we are proposing the synthesis and use of a highly effective new solid polymer desiccant material, i.e. superporous hydrogel (SPHs) of sodium acrylate and acrylic acid P(SA+AA), and subsequently its composite with deliquescent salt, i.e. calcium chloride (CaCl2), for the adsorption of water vapors from humid air without the dissolution of deliquescent salt in the adsorbed water. Synthesized SPH composite was characterized using different techniques like scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). Parental P(SA+AA)-SPHs matrix alone exhibited the adsorption capacity of 1.02 gw/gads which increased to 3.35 gw/gads after incorporating CaCl2 salt in the polymer matrix. For both materials, experimental isotherm data agreed with Guggenheim, Anderson and Boer (GAB) isotherm model and exhibited type-III adsorption isotherm. The adsorption kinetics followed linear driving force model. Furthermore, adsorbents were used successively for ten cycles of adsorption and regeneration. Therefore, the proposed polymer desiccant material overcomes the problem of dissolution of deliquescent salts and purposes a new class of highly effective solid desiccant material.

Probing the Water Vapor Adsorption Properties of MIL‐101 Doped with Manganese

AbstractThe chemical heat pump system is a heat management system based on the steam cycle. Combining the heat pump material and porous material into a frame can improve the heat storage capacity of the system. Metal‐OrganicFrameworks (MOF) is a kind of porous material with high porosity and specific surface area. We selected MIL‐101 (Cr) and studied whether doping can improve its water vapor adsorption capacity. In the hydrothermal synthesis process, we added manganese nitrate and chromium nitrate with different molar ratios to prepare four kinds of doped samples with diverse manganese contents, which were characterized by SEM, nitrogen adsorption test, XRD, FTIR, Raman test, TG, and water vapor adsorption test. Compared with the undoped sample, the particle diameter of the doped sample was doubled, and the water vapor adsorption increased by 30 %. Our experiments show that doping manganese ions is an effective way to adjust particle size and increase adsorption capacity.

Multiple Strategies to Fabricate a Highly Stable 2D CuIICuI–Organic Framework with High Proton Conductivity

Using multifunctional organic ligands with multiple acidic groups (carboxylate and sulfonate groups) to synthesize metal-organic frameworks (MOFs) bearing effective H-bond networks is a promising strategy to obtain highly proton conductive materials. In this work, a highly stable two-dimensional MOF, [CuII5CuI2(μ3-OH)4(H2O)6(L)2(H2L)2]·3H2O (denoted as YCu161; H3L = 6-sulfonaphthalene-1,4-dicarboxylic acid) containing mixed-valence [CuII5CuI2(μ3-OH)4]8+ subunits, was successfully prepared. It exhibited excellent stability and temperature- and humidity-dependent proton conduction properties. Its optimal proton conductivity reached 1.84 × 10-3 S cm-1 at 90 °C and 98% relative humidity. On the basis of a crystal structure analysis, water vapor adsorption test results, and activation energy calculations, we deduced the proton conduction pathway and mechanism. Apparently, uncoordinated sulfonic and carboxyl groups and a network of abundant H-bonds inside the framework were responsible for the efficient proton transfer. Therefore, the strategy of selecting suitable bifunctional ligands to construct two-dimensional Cu-cluster-based MOFs with excellent proton conductivity is feasible.

Effect of condensation on surface contact angle

Understanding the effect of condensation on surface contact angle is important in many applications, e.g., waste-heat recovery systems. This work aims to fill the two knowledge gaps in the literature related to the effect of condensation on the contact angle: (1) how the drop contact angle varies over time during condensation process; and (2) whether the evaporation of the condensed drops can be the reason for the observed contact angle under condensation environment. In this study, three surfaces, polystyrene, Teflon AF, and superhydrophobic surfaces, were used in experiments. The experimental results show that the contact angle between water and all three surfaces decreases with the time when the surface was exposed to the condensation environment. Such change of contact angle over time is caused by the evaporation of the condensed drop, which prompts the formation of a film formed around the condensed drop. The film formed due to the adsorption of water vapor onto the surface, causes a decrease in the contact angle observed over time. A theoretical model which considers the evaporation effect was developed to help to understand the experimental observation. Finally, to demonstrate the importance of the change in contact angle in condensation environment over time, we show its effect on shedding of drops in the context of drop-wise condensation.

Microwave detection with various sensitive materials for humidity sensing

Most of the humidity or gas sensing researches focus on the optimization of sensitive materials, while the studies of microwave detection focus on its sensitive-field control. It is necessary to implement the cooperative study on microwave detection with different types of sensitive materials for a better understanding of the operation mechanism as well as providing a way for performance enhancement. This study presents the double split-ring resonator as the sensitive electrode, where various sensitive materials, including polymer by pure Polyimide (PI), ceramic composite by PI-TiO2, metal composite by PI-Ag composite, are respectively tested as the sensing materials. The S-parameter is tested as the humidity indicators after coating on the sensitive regions with a strong electric-magnetic field. Owing to the improved dielectric properties by doping strong-polarity TiO2 nanoparticles into PI, the higher sensitivity with the maximum of 880.0 kHz/%RH and 0.322 dB/%RH is realized. The introduction of Ag nanoparticles facilitates the water vapor adsorption and desorption showing the sensitivity of 330.0 kHz/%RH and 0.149 dB/%RH, due to the high active-site density and surface roughness. By analyzing variations in resonant frequency and return loss, the microwave sensing mechanism of different sensitive materials is fully discussed from the perspective of polarization, dielectric property, and sensitive area.

Suitability of bio-desiccants for energy wheels in HVAC applications

This paper investigates the suitability of bio-desiccants for moisture recovery in energy wheels. Bio-desiccants are environment-friendly materials that have high water vapor adsorption capacities. The main contribution of this paper is that it reports the latent effectiveness of flax-fiber (bio-desiccant) coated energy wheels for a wide range of operating conditions and compares the effectiveness of the flax-fiber wheels with wheels that are coated with commercially available desiccants and other biomaterials. The moisture transfer performance of a flax-fiber coated exchanger is determined using a small-scale test facility and two different experimental methods: single step change tests and cyclic tests. The test results are used to verify the applicability of an effectiveness correlation from the literature. Using the energy wheel correlation and the sorption isotherms, the latent effectiveness of commercially available energy wheels coated with molecular sieve, ion exchange resin and silica gel desiccants are obtained and compared with that of bio-desiccants (flax fiber and starch particles). The highest latent effectiveness is obtained for silica gel followed by starch particles, ion exchange resin, flax-fiber and molecular sieve. The results from this study will be useful in research and development of bio-materials for energy recovery systems for building applications.

Room-temperature synthesis of hydrophobic/oleophilic ZIF-90-CF3/melamine foam composite for the efficient removal of organic compounds from wastewater

To overcome the shortage of conventional synthetic methods, such as long reaction time at high temperature and pressure (HTP) or poor performance at room temperature and pressure (RTP), a facile and economical strategy was employed to prepare high-performance ZIF-90 for the first time at RTP only by adding triethylamine (TEA). Herein, we successfully prepared ZIF-90 nanocrystals by a two-step stirring method within several minutes (5–30 min) and their structure parameters (e.g., BET surface areas, 916–1235 m2·g−1) were also tuned simultaneously, which were much better than reported samples prepared at RTP. Afterwards, by changing functional ligands, hydrophobic ZIF-90-CF3 with low surface energy was also designed. With the ligand side of aldehyde (–CHO) and trifluoromethyl (-CF3) groups on ZIF-90 and ZIF-90-CF3, the water vapor uptakes and adsorption heats decreased from 7.9 to 0.79 mmol·g−1 and 20.6 to 2.6 kJ·mmol−1, respectively. Additionally, a shaped ZIF-90-CF3/melamine foam (MF) composite with both hydrophobic and oleophilic properties exhibited extraordinary organic compounds (OCs)-water separation ability, including a high adsorption capacity (40.1–108.7 g‧g−1) towards various OCs. Furthermore, owing to its excellent compressibility and mechanical stability, the ZIF-90-CF3/MF composite can be regenerated by slightly squeezing the adsorbed OCs, indicating the potential for possible commercialisation of the derived MOF/MF composites for the efficient purification of wastewater.

Energy efficiency analysis of air dehumidification methods that determine safe microclimatic
 working conditions

Introduction. The article deals with the issues related to provision of air humidity parameters required for non-hazardous operation of various technical facilities. 
 Problem Statement. The paper considers analytical methods for energy efficiency assessment of adsorption and condensation methods of air dehumidification, which provide safe microclimatic working conditions, and the influence of the operating modes of dehumidifying plants on the parameters of the microclimate. 
 Theoretical Part. As indicators of the energy efficiency of each of the methods, it is proposed to use the energy costs that are minimally necessary for the implementation of ideal physical dehumidification processes and per unit mass of water units emitted from air. This ensures safe and comfortable microclimatic working conditions with minimal energy costs. The ratio of the specific energy costs of the condensation and adsorption methods shows their comparative efficiency. An electronic Id-diagram was used to determine the air parameters in the implemented dehumidification processes (cooling, condensation and adsorption of water vapor).
 Conclusion. Analytical dependences are obtained for the analyzed energy efficiency indicators that provide safe and comfortable microclimatic working conditions with minimal energy costs. Numerical estimates were carried out according to the most probable modes of dehumidification processes and air parameters. The parametric restrictions on the implementation of the adsorption dehumidification method are justified, in which it becomes energetically more profitable. The conditions under which it is possible to implement a combined dehumidification method to ensure safe microclimatic working conditions are determined.