Steam Humidification Research Articles

PERFORMANCE OF HEAT PUMP BASED ON COMPOSITE ADSORBENT ‘SILICA GEL – CRYSTALLINE HYDRATE’

Performance of an adsorptive heat pump has been studied. The factors affecting the efficiency of its work have been analyzed. Operating parameters and efficiency of adsorptive heat pumps and adsorptive heat storage devices have been compared. An algorithm of calculating the basic operating characteristics of an adsorption heat pump in heat supply systems has been proposed. It involves calculating the mass transfer coefficient, final absolute humidity of the air flow passed though adsorbent layer, the water uptake or adsorption and the useful heat of adsorption and heat of condensation, determination of heat inputs for the operation of the device such as heating the adsorbent, case of the device, hydraulic circuit, the water in the tank and adsorbed water, heat of desorption and heat of evaporation, estimation the coefficient of energy performance. The evaluation criteria of the efficiency of adsorptive heat pumps and heat storage devices have been compared. It is shown that the operating parameters of the adsorptive heat pump and the adsorptive thermal energy storage device based on composite adsorbents ‘silica gel – sodium sulfate’ and ‘silica gel – sodium acetate’ are the same, i.e. airflow rate 0.08 - 0.1 m3/s and initial absolute humidity of airflow 0.03 – 0.04 kg/m3, which are corresponded with maximal efficiency of the device. The temperature of the humid air flow directed to the adsorbent layer is suggested to be set at 20 – 40 °C. The measures to increase the efficiency of the adsorptive heat pump are proposed. It is shown that ultrasonic air humidification allows to increase the coefficient of energy performance by almost 2 times compared to steam humidification. The obtained results can be used for developing energy-efficient heating systems of residential premises.

EXERGY ANALYSIS OF AN OPEN-MODE ADSORPTIVE HEAT STORAGE UNIT BASED ON COMPOSITE ADSORBENT ‘SILICA GEL – CRYSTALLINE HYDRATE’

Exergy analysis of an open-mode adsorptive heat storage unit has been performed when a composite ‘silica gel – crystalline hydrate’ used as an adsorbent. The crucial factors affecting the exergy efficiency factor are stated to be temperature and initial humidity of airflow supplied to the inlet of adsorbent layer, temperature of external air and methods of air flow humidification. Procedure of calculation of the operating characteristics of an open-mode adsorptive heat storage device was further developed. The suggested procedure involves determination of adsorption, specific adsorption heat and final airflow temperature, useful heat, heat inputs for operating heat storage device and its efficiency factor, then exergy recovered, exergy supplied and exergy efficiency are calculated. Exergy efficiency depends on characteristics of flow of humid air fanned into the adsorbent layer such as temperature and initial absolute humidity which strongly affect the adsorption and final airflow temperatures. Increase of initial temperature of the humid air leads to decreasing of the exergy efficiency. Maximal values of exergy efficiency are determined at the absolute humidity and temperatures of initial airflow within the ranges of 0.03 – 0.04 kg/m3 and 20 – 30ºC, respectively. These characteristics are corresponded to the maximal airflow temperatures after passing through the adsorbent layer which meet to the Sanitary Regulations. Dependence of exergy efficiency vs. external air temperature and initial airflow temperature is shown. The exergy efficiencies of the open-mode adsorptive heat storage unit with steam and ultrasonic humidification were compared. Ultrasonic humidification is shown to allow increasing the exergy efficiency by 7 % against steam humidification. The obtained results can be used when energy-efficient heat and ventilation systems for residential premises developed.

Energy Benefit of Liquid Desiccant-Assisted Humidification in Buildings during Winter Operation

The objective of this study was to modify an existing liquid desiccant and indirect/direct evaporative cooling-assisted 100% outdoor air system (LD-IDECOAS) for humidification operation in winter. The energy benefit of the liquid desiccant-assisted humidification approach during the operation of LD-IDECOAS over the conventional method with a steam humidifier was evaluated through a detailed energy simulation. The humidification and enthalpy effectiveness values of the liquid desiccant humidification measured from laboratory tests were 0.41 and 0.49, respectively, which were applied to the energy simulation for the modified system. Both systems with the proposed and conventional humidification approaches were simulated using an engineering equation solver combined with a TRNSYS 18 energy simulation program. The results demonstrated that the modified LD-IDECOAS consumes less energy for humidification compared to the existing system with a steam humidifier. The proposed system also exhibited considerable heating energy-saving potential. Consequently, modified LD-IDECOAS consumed 42% less primary energy during winter operation after being modified for liquid desiccant-assisted humidification.

Relaxation State of Wood and Production of Cellulose Composites for Energy Purposes: Wood Briquettes and Pellets

Changes in the relaxation state of polymeric components of wood at the main stages of production of cellulose composites for energy purposes—wood pellets and briquettes—are considered. The possibility of transition to energy-saving technology due to dispersion under conditions of directional brittle destruction of sawdust during its transformation into a powder material and the extrudability of the powder in subsequent steam humidification is shown. An anomaly of the apparent viscosity of the wood system in the extruder due to the combined effect of water vapor, gaseous pyrolysis products, temperature, and shear stresses is observed.

Design of a psychrometric coil testing facility for commercial size heat exchanger coils

Abstract This paper presents the design of a testing facility at Oklahoma State University that enables performance testing of commercial-sized air to refrigerant heat exchanger coils. The closed-loop facility contains the necessary equipment to condition the air supplied to the tested coil. This includes the glycol conditioning system for the air conditioning heat exchangers, fans, electric heaters, and a steam humidification system. The design is compliant with multiple ASHRAE standards; the airflow measurement apparatus is compliant with both, Standard 41.2 (1987 and 2018). The test section's cross section is 2.13 m wide by 2.44 m tall with a maximum airflow rate of 3.78 m3 s−1. The thermal model presented in this paper predicts a maximum capacity of 80.9 kW for air heating coils (e.g. refrigerant condensers) at an air inlet temperature of 19.4 °C. The specified air flowrate and facility's maximum flowrate limit the capacity of air cooling (e.g. refrigerant evaporators) to a range of achievable values. The facility will operate over an air temperature range of −17.8 °C to 60 °C. Future work includes completion of construction of the facility including physical assembly, assembly of psychrometers, and commissioning of the developed facility control software.

Design and implementation of a modulating test plant to assess the performance of innovative cross-flow heat recovery units for air conditioning system: preliminary results.

Nowadays global warming has increased consciousness of the dangers of energy wastefulness: in the last 50 years the temperature of the Earth’s surface rose by approximately 1 °C. The building sector is responsible for a very high percentage of world carbon emissions and with the increasing of the request for comfort, heating, ventilation and air conditioning, buildings energy consumption is rapidly growing. Consequently, it appears fundamental the role played by the improvement of buildings energy performance within global policies of emissions reduction. In this context an increasing attention is given to the energy waste reduction in tertiary sector: bars, offices, restaurants, meetings, shops, school buildings, gyms and in general in the buildings in which the minimization of the energy dissipation is requested. The present study is part of the NANOFANCOIL project (POR-FESR 2014-2020): one of the objectives was the design and implementation of a modulating test plant to assess the performance of innovative cross-flow heat recovery units for air conditioning system. This experimental setup was mainly composed by two climatic chambers that enabled to simulate the environmental conditions of interest. The temperature could vary from -20°C to 0°C and from 10°C to 30°C for the cold and the hot chamber, respectively (i.e. the outdoor and the indoor environment). Moreover, the climatic chamber that simulates the indoor environment could be controlled also in terms of humidity thanks to a steam humidifier that guaranteed 5 kg/h of vapour. Preliminary results about the heat transfer behaviour of a cross-flow heat recovery unit (air-to-air) for controlled mechanical ventilation systems that employs mini-channels in order to increase performance and reduce size and costs are presented here.

TIME-VARIANT MODEL OF HEAT-AND-MASS EXCHANGE FOR STEAM HUMIDIFIER

The dynamical model of heat-mass exchange for a steam humidifier with lumped parameters, which can be used for synthesis of control systems by inflowing-exhaust ventilation installations, or industrial complexes of artificial microclimate, is considered. A mathematical description that represents the dynamical properties of a steam humidifier concerning the main channels of control and perturbation is presented. Numerical simulation of transient processes for the VEZA KCKP-20 humidification chamber to the influence channels was carried out. The achieved dynamical model of a humidification chamber can be the basis for the synthesis of automatic control systems and simulation of transient states. A significant advantage of the obtained mathematical model in the state space is the possibility of synthesis and analysis of a multidimensional control system.

Упруго-релаксационные свойства древесины лиственницы и их роль при получении древесных и древесно-угольных брикетов

Processing of sawdust, which accounts for 10…12 % of the volume of processed raw wood materials in products with high added value, is one of the areas of woodbiorefining. This became a premise for sawdust processing into secondgeneration biofuel, as well as carbonized briquettes based on it. The relaxation properties of larch wood are studied and their role in the technological process carried out in creation of new generation biofuel with a given set of operational properties is analyzedtaking into account the specific features of relaxation transitions at the stages of obtaining wood and charcoal briquettes.The relationship between the directed change in the relaxation state of the wood polymer components (lignin, cellulose and hemicelluloses) and the operational parameters is considered. The experimental data findings confirm that cellulose and hemicelluloses are in a high-elastic state in the initial wood and sawdust.It is advisable to ensure that the wood polymer components are transferred below the brittle temperature, in other words, wood should be dried to the lowest possible residual moisture, in order to grind wood sawdust to a powdery state with minimum energy consumption. Subsequent steam humidification to a moisture content of 3…4 % gives the system extrusion ability due to the formation of hemicellulose gel layers on the surface. For citation: Pekarets A.A., Erokhina O.A., Novozhilov V.V., Mandre Yu.G., Akim E.L. Elastic and Relaxation Properties of Larch Wood and Their Role in Production of Wood and Charcoal Briquettes. Lesnoy Zhurnal [Russian Forestry Journal], 2020, no. 1, pp. 200–208. DOI: 10.37482/0536-1036-2020-1-200-208

Mathematical Model of Heat-and-Mass Transfer for Steam Humidifier

The dynamical model of heat-mass exchange for a steam humidifier with lumped parameters, which can be used for synthesis of control systems by inflowing-exhaust ventilation installations, or industrial complexes of artificial microclimate, is considered. A mathematical description that represents thedynamical properties of a steam humidifier concerning the main channels of regulation and perturbation is presented. The resulting dynamical model of a humidification chamber can be the basis for the synthesis of automatic control systems and simulation of transients. A significant ad-vantage of the obtainedmathematical model in the state space is the possibility of synthesis and analysis of a multidimensional control system.

Investigation of the Concepts to Increase the Dew Point Temperature for Thermal Energy Recovery from Flue Gas, Using Aspen®

Thermal energy of flue gases (FG) dissipating from industrial facilities into the environment, constitute around 20% of the total dissipated thermal energy. Being part of the FG, water vapour carries thermal energy out of the system in the form of the latent heat, which can be recovered by condensation, thus increasing the overall efficiency of an industrial process. The limiting factor in this case is the low dew point temperature (usually 40–60 °C) of the water vapour in the FG. The increase of the dew point temperature can be achieved by increasing the water content or pressure. Taking these measures as a basis, the presented work investigated the following concepts for increasing the dew point temperature: humidification of the flue gas using water, humidification using steam, compression of the FG and usage of the steam ejector. Modelling of these concepts was performed using the commercial software Aspen®. The humidification of the FG using water resulted in the negligible increase in the dew point (3 °C). Using steam humidification the temperatures of up to 92 °C were reached, while the use of steam ejector led to few degrees higher dew point temperatures. However, both concepts proved to be energy demanding, due to the energy requirements for the steam generation. The FG compression enabled the achievement of a 97 °C dew point temperature, being both energy-efficient and exhibiting the lowest energy cost.

Energy consumption in humidification process

The purpose of the air-conditioning system is to provide people in an air-conditioned room or facility with thermal-humidity comfort. For this purpose, the external air before entering into the room is processed for its treatment. These processes include, among others, humidification of the air. Too high a humidity level also does not benefit the building and its people. Humidification of the air can be realized as directly, then the steam or water mist injection takes place in the room, and indirectly, when the supply air to the room is humidified in the ventilation system. The energy consumption in the humidification process depends primarily on stream of humid air, methods of humidifying the air (water or steam), the type of energy carrier used to produce steam or secondary heating of humid air, range of relative humidity maintained, external humidity parameters. In the case where both the steam and the secondary heating use the same energy sources, the costs in both cases will be comparable. In this paper the calculation of energy demand in hourly and annual period as well as for water and steam humidifier unit have been calculated and presented in many tables and figures. The semidetached house were taken under consideration to analyzed the energy consumption for humidification process. The amount of energy needed to humid the air during the annual season varies from 127 to 545 kWh/ar, depending on the humidifier used and the pump power, while for steam humidification the amount of energy for humidification is less than 9421 kWh/a. As a result, water humidification should be considered more economical. The basic difference between water and steam humidification, as evidenced by the hx graphs is decrease in the air temperature during water humidification and need to reheat it. Taking into account the energy requirements in both cases is similar. The humidifying costs of the steam humidifiers are much higher than those of water humidification.

Preliminary experimental and numerical analysis of a silica gel packed bed humidification system

In this research, an innovative air humidification system based on two packed beds made of silica gel spherical particles is developed. Each bed is alternatively crossed by two airflows (regeneration and process). The first air stream, at outdoor conditions, after being heated and humidified through the sorption material, is supplied to the building. The second one, also at outdoor conditions, provides water vapour to the desiccant packed bed. The system design and optimization is carried out through a numerical and experimental approach. The developed phenomenological model is based on the Pseudo Gas-side Controlled (PGC) method, considering only the gas side resistance and, therefore, assuming uniform water content and temperature distribution within the desiccant particles. A test rig to evaluate performance of the packed bed humidification system has been realized and experimental results have been used to validate the model. Obtained performance highlights that the proposed system can provide adequate humidification and that it can be a valid alternative to conventional adiabatic and steam humidifiers.

Impacts of humidification process on indoor thermal comfort and air quality using portable ultrasonic humidifier

Human exposed to low level of indoor humidity will have dryness (for skin, pharyngeal, eye etc.) or respiratory symptoms, which are closely related with indoor thermal comfort and air quality. To increase indoor humidity, portable humidification facilities (e.g., ultrasonic humidifiers) are widely applied in residential buildings due to their economy and convenience. Most of the available indoor humidity-related studies were associated with health issues induced by humidity and airborne pollutants generated by humidifier. However, the studies are rarely focusing on the effects of unsteady humidification (water vapor and droplet-induced from portable humidifier) on indoor thermal environment (i.e., air temperature, humidity, thermal comfort) and indoor air quality (e.g., TVOC, particles). Thus, this work aimed to investigate the impacts of humidification process on indoor environment by experiments in an isothermal chamber. The results show that portable ultrasonic humidifier increased humidity and decreased temperature simultaneously. The unsteady air temperature curve had “ladder-like” pattern. If RH increased from 34% to 60%, air temperature and PMV (Predicted Mean Vote) were decreased by 1.5 °C and 0.2 respectively. The obvious spatial stratification phenomenon was observed for both temperature and humidity field. We also found the obvious decrease of PM and TVOC concentrations during the entire humidifying process. Compared to traditional steam humidification system, indoor portable ultrasonic humidifier could save 70% of energy consumption and 18% of exergy loss. These qualitative characteristics of indoor humidification process would facilitate for indoor humidity control in the perspectives of human health and thermal comfort.

The synthesis procedure of multidimensional regulator for precision air conditioner with steam humidifier

The automatic control system (ACS) of air conditioning is considered in the framework of the unified computer-integrated complex with technological links of the air conditioner equipment. Taking into account the availability of dynamic models of HVAC equipment in the state space (developed by the authors in the previous works) precision air conditioner complex mathematical model with steam humidifier for the stabilization of microclimate parameters in the premises is obtained considering the technological relations between the climatic equipments.The dynamic model differs from the existing one by technological linkages due to sequential treatment of the supply air for the HVAC equipment and the use of moisture content parameter (instead of relative humidity) for mass transfer modeling in the process of air preparation. The procedure of optimal multivariate linear-quadratic digital controller (LQDC) in the state space, which takes into account the logical switching in HVAC equipment operation for the modified control algorithm by the “optimum mode” method, is offered. Simulation of transient processes for the ACS of precision air conditioning has confirmed the effectiveness of the proposed procedure of multidimensional control synthesis. Additional condition is the usability of the obtained model in the MatLAB environment.The ACS use with LQDC improves the integral quality indicators by 1.2 – 2.3 times in comparison with the ACS which uses one-dimensional digital controllers, and also decreases the colunt and duration of the transient processes. This approach allows us to rethink the synthesis of ACS air conditioning on the basis of differentiation of the mutual influence of governing parameters and it enables the transferring of the air conditioning control system to the qualitatively new level and provides the effective use of energy for artificial microclimate systems.

Energy-Saving Benefits of Adiabatic Humidification in the Air Conditioning Systems of Semiconductor Cleanrooms

This paper aimed to evaluate the applicability of adiabatic humidification in the heating, ventilation, and air conditioning (HVAC) systems of semiconductor cleanrooms. Accurate temperature and humidity control are essential in semiconductor cleanrooms and high energy consumption steam humidification is commonly used. Therefore, we propose an adiabatic humidification system employing a pressurized water atomizer to reduce the energy consumption. The annual energy consumption of three different HVAC systems were analyzed to evaluate the applicability of adiabatic humidification. The studied cases were as follows: (1) CASE 1: a make-up air unit (MAU) with a steam humidifier, a dry cooling coil (DCC), and a fan filter unit (FFU); (2) CASE 2: a MAU with the pressurized water atomizer, a DCC, and a FFU; and (3) CASE 3: a MAU, a DCC, and a FFU, and the pressurized water atomizer installed in the return duct. The energy saving potential of adiabatic humidification over steam humidification has been proved, with savings of 8% and 23% in CASE 2 and CASE 3 compared to CASE 1, respectively. Furthermore, the pressurized water atomizer installed in the return duct exhibits greater energy saving effect than when installed in the MAU.

Parametric identification of the process of preparing ceramic mixture as an object of control

Manufacture of ceramic materials and products largely depends on the preparation of clay raw materials. The main process here is the process of mixing, which in industrial production is mostly done in cross-compound clay mixers of continuous operation with steam humidification. The authors identified features of dynamics of this technological stage, which in itself is a non-linear control object with distributed parameters. When solving practical tasks for automation of a certain class of ceramic materials production it is important to make parametric identification of moving clay. In this paper the task is solved with the use of computational models, approximated to a particular section of a clay mixer along its length. The research introduces a methodology of computational experiments as applied to the designed computational model. Parametric identification of dynamic links was carried out according to transient characteristics. The experiments showed that the control object in question is to a great extent a non-stationary one. The obtained results are problematically oriented on synthesizing a multidimensional automatic control system for preparation of ceramic mixture with specified values of humidity and temperature exposed to the technological process of major disturbances.

G-39 医療施設向け加湿システムに関する研究 : (第1報) 加湿空気質に対する蒸気式加湿と気化式加湿の比較試験

G-39 医療施設向け加湿システムに関する研究 : (第1報) 加湿空気質に対する蒸気式加湿と気化式加湿の比較試験

Enhancement of fine particle filtration with efficient humidification

Filtration is one of the most effective methods to remove suspended fine particles from air. In filtration processes, pressure drop of compact dust cake causes problems in efficiency and economy, which has received increasing attention and still remains challenging. In this study, we developed a novel technique to intensify the filtration of fine particles with efficient humidification. Two strategies for humidification, including ultrasonic atomization and steam humidification (controlling of ambient humidity), were employed and proved to be both effective. The regeneration frequency of the filter could be reduced by 55% with ultrasonic atomization, while steam humidification could lead to a 78% reduction in regeneration frequency. The effect of operating conditions on pressure drop and the mass loading during filtration were investigated. The dust cake showed a loose and porous structure with an optimized droplet-to-particle ratio. With the ratio of 1.53 and 0.0282, the maximum mass loading was 552g·m−2 upon the ultrasonic atomization and 720g·m−2 upon the steam humidification. The results show that humidification could slow down the increase of pressure drop during filtration and improve the efficiency of process.

Desiccant wheels for air humidification: An experimental and numerical analysis

In this work the use of a desiccant wheel for air humidification is investigated through a numerical and experimental approach. In the proposed humidification system, water vapour is adsorbed from outdoor environment and it is released directly to the air stream supplied to the building. Such a system can be an interesting alternative to steam humidifiers in hospitals or, more generally, in applications where air contamination is a critical issue and therefore adiabatic humidifiers are not allowed. Performance of the proposed system is deeply investigated and optimal values of desiccant wheel configuration parameters are discussed. It is shown that in the investigated conditions, which are representative of Southern Europe winter climate, the system can properly match the latent load of the building. Finally, power consumption referred to the primary source of the proposed humidification system is compared to the one of steam humidifiers. The present analysis is carried out through experimental tests of a desiccant wheel in winter humidification conditions and through a phenomenological model of the device, based on heat and mass transfer equations.

SYNTHESIS OF OPTIMAL LINEAR-QUADRATIC DIGITAL CONTROLLER FOR INDUSTRIAL CONDITIONING WITH STEAM HUMIDIFIER

For industrial complexes artificial microclimate (ICAM) proposed a methodology to develop a comprehensive mathematical model of industrial air conditioning in the space of a condition that involves the analysis of the structure of an automatic control system (ACS) and the development of appropriate control algorithms. On the basis of the developed methodology received a comprehensive model for technological schemes of industrial air conditioners as a single multidimensional control object. For the proposed methods use dynamic models of climatic equipment in the space of States . For the General model ICAM presents matrices that define a comprehensive model of industrial air conditioner with a steam humidifier. The algorithm of synthesis of multidimensional linear-quadratic digital controller (LQDC) for ICAM developed. The problem of synthesis of optimal LQDC considered and synthesized matrix feedback LQDC, which the state parameters of the control object determines the trajectory of the vector of optimal exposure that minimizes the quadratic criterion. From the classical procedure of synthesis LQDC the proposed algorithm is characterized by the presence of the logical selection of accessories for optimal control. This approach allows us to rethink the synthesis of ACS, as air conditioning is based on the separation of the mutual impact of the regulatory options. This allows you to transfer the control system is conditioned to a qualitatively new level and ensures the efficient use of energy for artificial microclimate systems. The obtained formulas are recommended experts on design automation of control systems and optimization of existing ones.