Dehumidification System Research Articles

A Pilot-Scale Demonstration of Municipal Solid Waste Conversion to Energy and Resource Through Gasification and Dehumidification System

A Pilot-Scale Demonstration of Municipal Solid Waste Conversion to Energy and Resource Through Gasification and Dehumidification System

Edge Computing Based Storage Monitoring System Using IoT

Warehouses around the world have helped businesses meet their needs for long-term warehousing and preservation of goods. Storage systems are maintained under certain conditions according to the goods they store, using cooling and dehumidification systems. Products stored in cold storage facilities must be kept in a specific environment to store products such as vegetables, fruits, fish etc. To maintain storage systems, parameters such as temperature and humidity are critical for monitoring warehouse conditions. Over the years, it has been observed that small warehouses are not equipped with monitoring systems, making it more difficult for many warehouses to manage these systems. As the food industry grows, small warehouse owners must use a system that will meet their storage needs at a lower cost. In this paper, we have proposed a system that will monitor the warehouse with an alarm system and overcome the disadvantages of the industry's expensive systems. The proposed system is based on edge computing, which results in low latency, lower power consumption, and a more compact solution than existing systems that can be used by small warehouse owners in urban and rural areas. The system provides real-time feed of various parameters through a web-app that is deployed on the cloud and can be accessed from anywhere.

Simplified Calculation of Flow Resistance of Suspension Bridge Main Cable Dehumidification System

To calculate the flow resistance of a main cable dehumidification system, this study considers the air flow in the main cable as the flow in a porous medium, and adopts the Hagen–Poiseuille equation by using average hydraulic radius and capillary bundle models. A mathematical derivation is combined with an experimental study to obtain a semi-empirical flow resistance formula. Additionally, Fluent software is used to simulate the flow resistance across the main cable relative to the experimental values. Based on the actual measured results for a Yangtze River bridge, this study verifies the semi-empirical formula, and indicates that it can be applied in actual engineering.

Техническое решение для обеспечения оптимальной влажности воздуха в животноводческом помещении

The article describes the relevance of the development and use of air dehumidification systems in animal husbandry premises, the installation for maintaining the optimal relative humidity of the air is developed. Optimum microclimate in livestock buildings contributes to a more complete realization of the genetic potential of animals and birds, prevent disease, increase natural resistance and prolong the service life of buildings and installed equipment. Ensuring an optimal indoor microclimate is achieved by observing the scientifically based values of the environmental factors that form it (temperature, humidity, air velocity, etc.), which are generalized and given for each type of animal in the relevant standards of technological design of livestock enterprises.

Assessment of Solar Dehumidification Systems in a Hot Climate

Solar thermal-powered desiccant dehumidification systems are attracting attention for cooling load-dominated climates. However, their performance varies substantially from place to place depending on climatic conditions, which therefore warrants a tailored design and specification at each geographical location. The current article attempted to investigate the feasibility of extending an existing solar thermal system in a school building in Abu Dhabi to provide dehumidification for the existing air condition system through a desiccant system. The system performance was predicted through a Transient System (TRNSYS) Simulation model to determine the energy savings achieved by the solar-assisted dehumidification system. The current articles determined the effect of fluid flow rate, solar radiation concentration, and heat exchanger effectiveness at the dehumidification of the fresh air as well as energy saved by the proposed system. It was concluded that the system can remove 35% moisture from the air, simultaneously saving 10% of the building’s energy. The system cost and benefit analysis revealed a payback period of 7.5 years, considered slightly higher for an attractive investment in such systems.

Investigating Solid and Liquid Desiccant Dehumidification Options for Room Air-Conditioning and Drying Applications

This study reports on the investigation of the performance of single and two-stage liquid and solid desiccant dehumidification systems and two-stage combined liquid and solid desiccant dehumidification systems with reference to humid climates. The research focus is on a dehumidification system capacity of 25 kW designed for room air conditioning application using the thermal models reported in the literature. RD-type silica gel and LiCl are used as solid and liquid desiccant materials, respectively. In this study, the application of proposed system for deep drying application is also explored. Condensation rate and moisture removal efficiency are chosen as performance parameters for room air conditioning application, whereas air outlet temperature is chosen as performance parameter for deep drying application. Further, for a given range of operating parameters, influences of air inlet humidity ratio, flow rate, and inlet temperature on performance parameters of the systems are investigated. In humid climatic conditions, it has been observed that a two-stage liquid desiccant dehumidification system is more effective for room air conditioning application, and two-stage solid desiccant dehumidification system is more suitable for deep drying application in the temperature range of 50 to 70 °C, while single-stage solid desiccant and two-stage combined liquid and solid desiccant dehumidification systems are more effective for low temperature, i.e., 30 to 50 °C deep drying application.

Performance analysis of a cascade lithium bromide absorption refrigeration/dehumidification process driven by low-grade waste heat for hot summer and cold winter climate area in China

Recovery of low-grade waste heat has great potential to reduce energy consumption around the world. In this paper, a novel cascade lithium bromide absorption refrigeration/dehumidification system is developed to recover low-grade waste heat with temperature range from 90 °C to 150 °C for dehumidification in hot summer and cold winter climate area of China. This system consists of two subsystems: lithium bromide absorption refrigeration system and lithium chloride liquid dehumidification system. The low-grade waste heat is applied by two subsystems in a cascade approach. The key parameters in terms of air temperature, air humidity, solution concentration, and solution temperature are investigated to obtain the optimization design of the proposed system. Performance of the proposed system is analyzed for different refrigeration temperatures. The results show that the max coefficient of performance for the proposed system is 0.6029. The moisture removal rate and the humidity efficiency are 20.20 g/kg and 0.9385. The novel coupling system develops a creative and efficient way to recover low-grade waste heat for dehumidification in hot summer and cold winter climate area of China.

Experimental investigation on structured packed bed liquid desiccant dehumidifier: An optimal mixture design of experiments strategy

Abstract Maintaining human thermal comfort and extensive power consumption of the conventional heating ventilating and air-conditioning systems drive the researchers to look for an alternative dehumidification system. Among the potential alternatives, the liquid desiccant dehumidification system has evolved as a long-term renewable and less power consuming system due to its effective controlling capability of humidity. In the present study, an experimental investigation is carried out to demonstrate the performance of lithium bromide (LiBr) and potassium formate (HCOOK) desiccant solution mixture in a spray type counterflow-packed bed adiabatic dehumidifier. Subsequently, ternary plots and 3D-contour trade-off paradigms are patterned to assess the performance parameters using an optimal mixture design methodology. Additionally, empirical correlations are developed to pattern the performance parameters (moisture removal rate (MRR), enthalpy effectiveness (ξh) and moisture effectiveness (ξm)) as a function of blend combinations. Further, the present study endeavours to explore the application of offline calibration methods based on a balanced optimum mixture design-centred desirability approach for optimizing the mixture proportion to obtain the optimal performance parameters (i.e., MRR, ξh and ξm). The wettability area is explained based on the static contact angle on a plane glass. The results showed that the contact angle was decreased from 47.3° to 44.1° for the optimum mixture of LiBr solution (37.2%-LiBr +17.8%-HCOOK), which further confirmed the higher MRR. Lastly, the tuning effect of the liquid to gas flow rate on the dehumidifier performance and economic viability of LiBr-HCOOK blends are studied.

Effect of Evaporator Position on Heat Pump Assisted Solid Desiccant Cooling Systems

The packaged terminal air conditioning with reheat (PTACR) system, as a commonly used dehumidification system, faces the problem of extra energy consumption in the deep-cooling and reheating processes. Therefore, different heat pump assisted hybrid solid desiccant cooling (HPDC) systems were proposed and their characteristics were investigated via EnergyPlus simulations. The system energy efficiency presents an upward trend with the increase in outdoor temperature and humidity. A high-humidity climate leads to the improvement of system performance. The dehumidification performance of the desiccant wheel in the HPDC system declines when outdoor humidity increases. Compared with the PTACR system, the energy consumption of the HPDC system in which the evaporator was placed upstream of the desiccant wheel is reduced by 36%, 66%, and 64%, respectively, under different high-humidity climates. The system maintained the indoor environment within the comfort zone, and eliminated the need for a heat source for desiccant regeneration. In conclusion, the HPDC system is an available alternative that considers both energy consumption and system performance. Placing the evaporator upstream of the desiccant wheel is more advantageous in high-temperature and high-humidity climates.

Energy saving potential of a vacuum-based membrane dehumidifier in a dedicated outdoor air system

As a novel energy-conservative ventilation system for buildings, a dedicated outdoor air system (DOAS) assisted by a vacuum-based membrane dehumidifier is proposed, and its energy performance is investigated via detailed energy simulations. The vacuum-based membrane dehumidifier dries the air by an isothermal process, which is difficult to realize in conventional dehumidification systems. The proposed system consists of an enthalpy exchanger, a vacuum-based membrane dehumidifier, and a cooling coil. Its dehumidification performance and operation energy are compared with those of the following conventional DOASs: a DOAS that employs a cooling coil (Reference A) and a DOAS that employs an active desiccant wheel (Reference B). To evaluate the energy performance of the proposed system, the energy consumptions of all the DOASs were estimated by simulation programs (i.e., TRNSYS and EES) with mathematical models. The simulation results indicate that the average coefficient of performance of the DOAS we devised (i.e., 1.34) is lower than that of Reference A (i.e., 2.70) and higher than that of Reference B (i.e., 0.80). However, owing to the isothermal dehumidification process, the latent cooling ratio in the case of the proposed system (i.e., 1.0) is significantly higher than those in the cases of Reference A (i.e., 0.43) and Reference B (i.e., 0.11). Consequently, the annual energy consumption of the proposed system is 17.4% and 56.2% lower than those of Reference A and Reference B, respectively.

Investigation of a compact hybrid liquid-desiccant air-conditioning system for return air dehumidification

In some automatic workshops, pharmaceutical warehouses, etc., there are control requirements for indoor air temperature and humidity, yet almost no occupants or no fresh air demand in the rooms. In this study, a hybrid liquid-desiccant air-conditioning (LDAC) system is proposed for the unoccupied rooms without fresh air demand. In the proposed system, the liquid dehumidifier and regenerator are cascaded, and the regeneration process is creatively moved to indoors. Two systems are selected as the reference systems, i.e., conventional vapor-compression system (reference system I) and conventional LDAC system using outdoor air for regeneration (reference system II). The simulation results reveal that, under the typical summer condition in Guangzhou of China, the coefficients of performance (COPsys) of the proposed system, reference system I, and reference system II are 2.6, 1.8, and 2.3, respectively, when the air is dehumidified from 13.0 to 7.7 g/kg. Compared to the reference system I, the reheating process can be avoided, and higher-temperature chilled water at 16 °C can be used in the proposed system. Compared to the reference system II, using indoor air for regeneration helps to reduce the regeneration temperature. Thus, the proposed system demonstrates energy and space advantages than the reference systems.

A novel metal-organic frameworks based humidity pump for indoor moisture control

Latent heat load accounts for a significant proportion of energy consumption by air-conditioning, particularly for buildings in humid climates. Traditional vapor-compression refrigeration dehumidification faces problems like refrigerant leakage, overcooling, and complicated mechanical systems. Here, we report a novel humidity pump that uses metal-organic frameworks (MOFs) as desiccant layers to transport moisture from a low-humidity space to a high-humidity one efficiently. The working principle and operation modes of the humidity pump are introduced herein for which the dehumidification performance is investigated at 22.8 °C with 60% RH. The dehumidification rate and moisture removal efficiency of the MIL-100(Fe) based humidity pump reached 26.24 g h−1 and 0.87 g Wh−1, respectively, and these are 2.15 and 2.12 times higher than that of the humidity pump with silica gel coating. The maximum dehumidification coefficient of performance (DCOP) of the humidity pump could reach up to ~0.46, higher than the conventional desiccant dehumidification systems. In addition, many factors, such as the cycle time, thermoelectric power, air velocity, etc., which may affect the dynamic characteristics and dehumidification performance, were analyzed. Lastly, the localized humidity management ability of the designed humidity pump using MIL-100(Fe) was validated by a small chamber test. The results indicate that the MOF humidity pump could achieve energy-efficient localized moisture control.

Study on Desiccant Dehumidification System Using Experiments and Steady-State Model

Study on Desiccant Dehumidification System Using Experiments and Steady-State Model

Investigating Applicability of Heat-Driven Desiccant Dehumidification System for Shelf Life Improvement of Fruits and Vegetables

Investigating Applicability of Heat-Driven Desiccant Dehumidification System for Shelf Life Improvement of Fruits and Vegetables

Lab-Scale Study of Desiccant Dehumidification System for Poultry Shed Air-Conditioning in Pakistan

Lab-Scale Study of Desiccant Dehumidification System for Poultry Shed Air-Conditioning in Pakistan

Performance investigation of a liquid desiccant regenerator with CFD technology

The regenerator is a critical component for a liquid desiccant dehumidification system. Compared with the dehumidifier, the studies of the regenerator are much fewer. Besides, most of the present models only focused on the outlet parameters while usually ignored what happened in its interior, and therefore the underlying heat and mass transfer mechanism was remained to be explored. In the paper, a numerical model was established based on Computational Fluid Dynamics (CFD) technology. It revealed that the simulation results agreed well with the experimental ones within an average deviation of 10.2%. The response time for regeneration time was significantly affected by the velocity of air and solution. A greater velocity led to a shorter response time due to an enhanced mixture in vertical direction. The regeneration performance could be improved at higher solution flow rate as a result of greater interface area ratio and faster solution surface renewal. The influence of inlet air temperature on the regeneration process was relatively smaller compared to other factors. And it was found that increasing the solution temperature could be more beneficial to regeneration performance than reducing the mass fraction of water vapor at air inlet.

Energy impact of vacuum-based membrane dehumidification in building air-conditioning applications

The energy and operating performances of a vacuum membrane dehumidification system were theoretically investigated for building air conditioning applications. The dehumidification effectiveness and coefficient of performance (COP) were adopted as performance indices. A one-dimensional mass-transfer model was derived to analyze the effect of each operating parameter on dehumidification performance. The data predicted by the model agreed well with measured results, with an error bound of 20%. Parametric analysis results indicated that the vacuum side pressure had the most significant impact on the energy and dehumidification performances. It was also observed that the membrane module length plays an important role in the module design. Based on the analysis results, a configuration and operating strategy of a vacuum membrane dehumidifier-assisted variable air volume air conditioning system were suggested. Subsequently, the proposed system was evaluated by comparing its energy and operating performances with those of the conventional variable air volume air system via energy simulations. The results indicated that the total primary energy consumption from the proposed system was 8.2% lower than that of the conventional system. However, the fan energy consumption in the proposed system was 2.5 times higher than that of the conventional system owing to the high pressure drop of membrane module. In addition, the proposed system consumed 7.7% more primary energy for dehumidification and sensible cooling process because of its lower COP. To achieve comparable energy performance, further research on the optimized design of a membrane module and optimized operation of a vacuum pump in the proposed system are necessary.

Combination of a solar collector and thermoelectric cooling modules in a humidification–dehumidification desalination system-experimental investigation with energy, exergy, exergoeconomic and environmental analysis

In this study, a novel humidification–dehumidification desalination (HDD) system, consisting of a hybrid solar collector with two working fluids, air and ethylene glycol, is designed and tested under climatic condition of Tehran, Iran. In this design, air passes above the absorber plate, while ethylene glycol flows through the copper tubes located on the absorber plate. The dehumidification system is also equipped with thermoelectric cooling modules. The effects of different parameters including collector outlet air velocity, volumetric flow rates of ethylene glycol and saline water and the effect of thermoelectric cooling on the performance and exergy of the system have been investigated. The experimental results showed that the water production improves by 8% with increasing the collector outlet air velocity from 2.2 to 3 m/s, while it reduces by 17% when increasing the collector outlet air velocity in the range of 3 to 4.2 m/s. In addition, the daily productivity increases about 44% by increasing the volumetric flow rate of ethylene glycol in the collector in the range of 0.83 L/min to 2.24 L/min. Moreover, the daily productivity of the system improves about 55% by increasing the volumetric flow rate of saline water from 0.66 L/min to 3 L/min. Furthermore, the productivity improves about 4% as the distance between the glass cover and the absorber plate decreases from 27.25 mm to 14.75 mm. The results also show that the productivity increases about 13% by using the thermoelectric cooling system. Finally, the maximum hourly exergy efficiency and maximum daily exergy efficiency were measured as 12.75% and 8.78%, respectively. Economic analysis shows that the estimated cost of water production is 0.097 $/lit/m2 which is comparable with the other devices reported in the literature. Finally, the exergoeconomic and environmental analysis are analyzed and discussed to show CO2 mitigation and economic potential of the system.

Experimental based multi-objective optimisation for structured packed bed liquid desiccant dehumidification systems

In last few decades, a substantial advancement has been observed in dehumidifier modules for their energy-conservative and environment-friendly nature; however, still uncertainty in decision-making is of concern in selection of optimum input parameters to attain an effective performance. In this perspective, an experimental study is performed in an adiabatic packed bed, counter-flow liquid desiccant dehumidifier fuelled with the blend of lithium bromide and calcium chloride solution at various operating conditions with different control settings. It is observed that air mass flux rate (Fa), solution concentration (ζ) and air specific humidity (ωa) have significant impact on condensation rate (CR), whereas, air mass flux rate (Fa) and solution temperature (Ts) are the most effective parameters for moisture effectiveness and latent heat factor, respectively. The experimentally obtained results for multiple response performance characteristics are represented based on inlet process parameters using gene expression programming (GEP). The proficiency of developed GEP meta-models is provided by statistical parameters, Taylor diagram and Theil uncertainty. Subsequently, GEP meta-model based fuzzy logic is developed for optimising dehumidifier inlet process parameters in terms of multi-responsive performance characteristics using Genetic Algorithm. The optimisation results showed that dehumidifier performance characteristics have a tendency to become optimal at Fa = 0.766 kg/m2-s, Ta = 30.745 °C, ωa = 0.023 kgwv/kgda, Fs = 1.812 kg/m2-s, Ts = 24.01 °C, and ζ = 48.1%. Finally, experiments were conducted at optimum conditions and observed proximity between the predicted and experimental outcomes, which further validates the current optimisation approach.

Design requirements for condensation-free operation of high-temperature cooling systems in mediterranean climate

Radiant cooling systems are a subject of increasing scientific interest due to their efficiency and ability to use high-temperature cooling sources. In hot and humid conditions, they have generally been studied in combination with dehumidification systems. For retrofit projects, a control system that would eliminate the need for dehumidification would be beneficial. In the present study, a passive geothermal-based radiant high-temperature cooling system is studied in a Mediterranean climate. The system is operated with supply water temperature control using dew point temperature as a controlling variable. The system's performance is compared with that of an all-air cooling system. The systems are evaluated using IDA-ICE building energy simulations, validated with on-site measurement data. The results show that the radiant cooling system produces the same level of thermal comfort with 40% lower energy use and 85% lower exergy consumption than the all-air system. The risk of condensation limits the cooling capacity of the radiant cooling system. Consequently, insufficient cooling capacity causes thermal discomfort for the occupants due to the operative temperature exceeding 26 °C.