Liquid Desiccant System Research Articles

Energy-saving in a liquid desiccant dehumidification system with a semipermeable-membrane-assisted dual sump

With the recent development of the independent control of temperature and humidity, the demand for dehumidification has significantly increased, and liquid desiccant dehumidification systems have attracted considerable attention because of a high dehumidification efficiency. This study presents a new design for a liquid desiccant dehumidification system that applies a membrane-assisted dual sump for maintenance the solution concentration with a low solution cooling and heating loads. A detailed heat and mass transfer analysis was conducted to evaluate the feasibility of the membrane for the maintenance the solution concentration according to the mass transfer resistance of the membranes. Moreover, the variation in the solution temperature and concentration was predicted by performing detailed simulations. The simulation results indicated that the low-mass-transfer-resistance membrane requires a large amount of solution load and the high-mass-transfer-resistance membrane cannot be used to maintain the solution concentration. Thus, the mid-mass-transfer-resistance (i.e., 15,000 s/m) membrane is suitable for the liquid desiccant dehumidification system. Compared with the conventional liquid desiccant dehumidification system based on a solution exchange, the membrane-assisted liquid desiccant dehumidification system could save about 19% load for solution cooling and heating owing to the lower heat and mass transfer rate on the absorber and regenerator sump. • The liquid desiccant dehumidification system with a membrane was proposed. • Various types of membranes were considered to evaluate the applicability. • Heat and mass transfer analysis was conducted to estimate the system performance. • The proposed system can reduce the load by about 19% for solution cooling and heating.

A dual-scale analysis of mass transfer enhancement in liquid desiccant system for indoor VOCs removal by adding surfactant

Indoor volatile organic compounds (VOCs) pollution control is a major challenge facing the healthy development of people. Liquid dehumidification is expected to be a potential way for VOCs removal. However, the poor mass transfer ability for some hydrophobic VOCs in liquid desiccant (LD) system results in a lower removal performance. Therefore, a dual-scale perspective is proposed to enhance VOCs transfer in this study. It includes micro material property for VOCs transfer at solution interface, and macro system model for heat-moisture-VOCs transfer in LD system. The micro and macro sub-perspectives are combined via key information exchange. Moreover, surfactant is firstly introduced into LD system to enhance VOCs transfer from dual-scale perspective. The surfactant can effectively improve the solubility of hydrophobic VOCs in LD and enhance their mass transfer at solution interface. Through experiment and simulation, the influences of micro material properties and macro working parameters on VOCs transfer characteristic are investigated considering air dehumidification requirements. Using the proposed dual-scale perspective, a new LD is designed. Thus, the VOCs transfer ability at micro interface and macro system are improved by 19.24% and 16.67%, respectively. It is found that the enhanced VOCs transfer ability is co-determined by micro material properties and macro working parameters. In a way, the proposed approach can realize the dual-scale co-design from “micro interface - macro system”. Entirety analysis of the VOCs transfer characteristics in LD system is feasible with this methodology.

Assessment of dehumidification performance of non-corrosive desiccant in hybrid liquid desiccant-vapour compression system

ABSTRACT Air-conditioning (AC) systems, which operate on traditional vapor compression refrigeration (VCR) systems, consume a substantial proportion of the world’s electricity consumed by the building industry. In the scope of decreasing greenhouse gas emissions, energy consumption, heating, ventilation, and air conditioning industries have focused on finding alternatives to electrically operated VCR systems. A combination of a liquid desiccant dehumidification system (LDDS) with a VCR system has been recommended as a superior substitute in warm and moist climates. The focus of this research article is to design and fabricate a small-scale 5 kW hybrid LDDS system by integrating the distinct technologies mentioned above. Additionally, data collected on the vapor pressure of potassium formate (KCOOH) at various solution concentrations and temperatures is being collected to assist in encouraging research and determine the optimal concentration range. In this study, experimental analysis and comparison of dehumidification performance was conducted between two desiccants by analyzing the effects of input variables ( m a , T d , and ω s ) on the output response ( Δ ω , Q d e h , and C O P h ). The results showed that the solution with a 69.92% KCOOH concentration had nearly the same vapor pressure as a solution with a 35% LiCl concentration. Moreover, it was revealed that the lowest values of m a and T d and the highest value of ω s yield maximum values of the output responses. At the same combination of input variables, the KCOOH desiccant has a much higher hybrid system coefficient of performance than the LiCl desiccant.

Study on the performance of solar interfacial evaporation for high-efficiency liquid desiccant regeneration

Liquid desiccant air conditioning system (LDAS) was considered a promising air conditioning system due to the advantages of low-grade heat utilization, effective humidity control and environment-friendly. The performance of LDAS significantly depends on the heat and mass transfer components, namely dehumidifier and regenerator, while the regeneration process of traditional regenerator is energy-inefficient. Inspired by the high-efficiency solar interfacial evaporation which can produce drinking water from seawater, this method was introduced in this work for liquid desiccant regeneration to overcome the inefficiency of the regeneration process. Wood was prepared as the regenerator by alkali-assisted method and surface carbonization. The regeneration performance of solar interfacial regeneration was experimentally investigated and compared with that of packed-bed tower regeneration and membrane distillation regeneration. Results show solar interfacial regeneration is very competitive due to the high regeneration rate and efficiency, which can reach 0.57 kg m−2 h−1 and 42.5% for 40% LiCl solution under 1-sun irradiation. Moreover, the low temperature rises of concentrated solution, cheap construction costs and operating costs make LDAS more energy-saving. This work is expected to supply a novel method for liquid desiccant regeneration.

Experimental Investigation of Thermal Performance Parameters of Drying Air Unit with a Different Flowrate of Liquid Desiccant Solution

Liquid desiccant air-conditioning systems remove directly the latent load from moist air and remove indirectly sensible load of this air by using an indirect evaporative cooling process. The liquid desiccant must subsequently be regeneration once again with a low-grade heat source like solar energy. In this study, calcium chloride solution was used as a desiccant. For the desiccant solution regeneration process, a flat plate solar collector was employed. Different variables, such as the primary airflow rate and desiccant flow rate, were changed during the experiments. The impact of these variables on the performance parameters of the desiccant systems such as moisture removal rate, moisture efficiency, enthalpy efficiency, sensible heat ratio, and the mass transfer coefficient was studied. The obtained results revealed that as the flow rate of primary air increases, the moisture removal rate, sensible heat ratio, and the mass transfer coefficient increase. For example, from 0.006 m/s to 0.0125m/s when the mass airflow rate increased from 0.1 kg/s to 0.18 kg/s.

A short note on the application of the Cisternas-Lam vapor pressure model for liquid desiccant dehumidifier systems

Desiccants are an important part of dehumidifier systems, contributing to absorbing the humidity of the air. The vapor pressure is one of the most important properties in the dehumidification process. For this reason, the application of the Cisternas–Lam model can overcome difficulties such as the lack of experimental vapor pressure measurements. In this work, this model is applied to aqueous solution of several desiccants such as CH3COONa, CH3COOK, NaClO4, and KClO4, including ionic liquids such as [EMIM][OMs], [EMIM][OAc], [EMIM][OTf], [E3MPy][OMs], [EMIM]Cl, [BMIM]Br, [BMIM]Cl, [BMIM]I, [EMIM][ES], [EMIM][MS], [BMIM][DBP], [EMIM][DEP], [MMIM][DMP], [EMIM][DMP], [EEMI][DEP], [EMIM][Tf2N], [EMIM][DCA], [DMIM][BF4], and [MMIM][MS], estimating their K value in binary aqueous systems. In addition, the prediction capacity of the model is tested in interpolation and extrapolation examples and shows good results. Finally, this model is used to predict the vapor pressures of aqueous ternary systems that contain ionic liquids. The results showed that the Cisternas-Lam model is appropriate to correlate and predict vapor pressure in the systems studied.

Experimental performance of a three-fluid desiccant contactor using a novel ionic liquid

• Novel Ionic Liquid that is not corrosive to aluminum is used as liquid desiccant. • New three-fluid fin-tube desiccant contactor fabricated using aluminum. • Experimental performance of the fin-tube contactor using IL solution is investigated. • The fin–tube contactor showed superior performance than the packed bed contactor. • Lower solution flow rates and pumping power is expected using the fin–tube contactor. The experimental performance of a new three-fluid fin–tube contactor using a novel ionic liquid desiccant solution is investigated and compared with those of an adiabatic packed bed contactor with LiCl solution for liquid desiccant air conditioning system applications. Owing to the compatibility of the ionic liquid solution with aluminum, a fin–tube contactor is manufactured to exploit internal cooling from a third fluid. The results indicate the superior dehumidification performance of the fin–tube contactor, which yielded an outlet air humidity ratio of 10.5 g w ·kg da -1 at a solution mass flux of 3.06 kg·m −2 ·s −1 , as compared to a similar humidity ratio at a solution mass flux of 4.98 kg·m −2 ·s −1 achieved by the packed bed contactor. In terms of cooling performance, the outlet air temperature of the fin–tube contactor is 21.9 °C, which is lower than that of the packed bed contactor even at its highest solution mass flux. This indicates that the cooling performance of the fin–tube contactor has minimal dependence on the solution mass flux in achieving cooling effect, owing to the cooling medium flowing inside the tubes. Relatively lower solution pumping power than that of the packed bed contactor can be expected from the fin–tube contactor, in addition to the ability to achieve comfortable and hygienic indoor air at a cooling medium temperature of 17 °C or higher, the ionic liquid desiccant and three-fluid fin–tube contactor pair for liquid desiccant air conditioning system is elevated a step higher as an alternative to vapor compression air conditioning system.

Performance study of heat and mass transfer in a counterflow liquid to air membrane-based parallel-plate dehumidifier

Liquid to air membrane energy exchanger (LAMEE) is the most important component in a liquid desiccant air conditioning system. Three main configurations of LAMEE are presented in the literature: co-current, counterflow, and cross-counter flow. In this paper, we evaluated the performance of a counterflow LAMEE dehumidifier in terms of its cooling capacity (CC) and moisture removal rate (MRR). A numerical model was developed and validated with experimental results. The impact of solution properties and inlet air characteristics on the LAMEE’s performance were investigated. Simulation results show that CC and MRR are enhanced by decreasing the temperature and increasing the concentration of the liquid desiccant simultaneously. In order to obtain an optimal performance of the LAMEE, the solution mass flow rate should be equal to or slightly higher than the inlet air mass flow rate. On the other hand, we found that both CC and MRR increase with increasing inlet air temperature and relative humidity. Even though solution properties and inlet air characteristics affect the MRR and the CC, they have a negligible effect on the required air sensible cooling to meet the supply air condition (Qsen). The characteristics of outlet air provided by the LAMEE are in a stable state condition, which proves that the LAMEE has a wide range of adaptability in different operating conditions.

Performance investigation on electrodialysis regeneration of potassium formate desiccant solution for liquid desiccant air-conditioning systems

In this work, the ED regeneration experiments were conducted using KCOOH (potassium formate) liquid desiccant, which is attracting attention due to its non-corrosiveness and low toxicity. Varying solution concentration, solution temperature, and current density, effect of the operating conditions on overall transport number, overall hydration number, overall osmotic coefficient, and area-specific resistance (ASR) was analyzed. In particular, effect of the solution temperature on the ASR, which was frequently ignored in previous research, was evaluated. As the solution temperature increased from 21 °C to 30 °C, the ASR decreased 21% and 17% at different concentration conditions. Additionally, the overall transport number of the KCOOH was compared with experimental data of different liquid desiccants in other research. The result showed that at low solution vapor pressure condition, KCOOH recorded the largest overall transport number so that it has a potential to be an energy-efficient working fluid for ED regeneration system. Furthermore, the analysis results and the regression equations can be utilized in developing a system modelling of the liquid desiccant regeneration using ED with KCOOH desiccant in future research.

A novel drift eliminator enhanced by Voronoi-based porous foam applied to liquid desiccant system: Separation performance and preliminary design

A novel drift eliminator enhanced by Voronoi-based porous foam (VPF-enhanced drift eliminator) is proposed for the control of salt-spray aerosol in liquid desiccant systems. The gas-liquid flow characteristics though VPF-enhanced drift eliminator under different conditions are examined numerically and verified by the experimental results in the literature. Additionally, a new prediction model of separation efficiency is obtained based on response surface methodology. The results show that 3-D modeling of porous foam based on Voronoi technology can well characterize the structure properties of actual porous foam in terms of meso-scale (i.e. pore shape, strut orientation and cell topology) and macro-scale (i.e. strut diameter and porosity), which provides support for more accurate analysis of separation performance from the microscopic aspect of droplet. Separation performance exhibits a strong dependence on the structure properties of porous foam and operating conditions. Moreover, the interaction of thickness and porosity has a significant impact on separation efficiency. For porous foams with relatively low resistance (i.e. smaller thickness and higher porosity), separation efficiency can be simply quantified by the specific surface area of the porous foam. For relatively high resistance, it is jointly determined by the specific surface area and resistance. It is concluded that prediction model combined with multi-objective optimization can provide guidance for the structural design and selection of VPF-enhanced drift eliminator. Meanwhile, Voronoi-based porous foam can be conveniently processed by the additive manufacturing techniques, which provides engineering significance for the development of VPF-enhanced drift eliminator under specific needs.

Comparative Analysis on Dehumidification Performance of KCOOH–LiCl Hybrid Liquid Desiccant Air-Conditioning System: An Energy-Saving Approach

Conventional air conditioners (AC) operate on vapor compression refrigeration (VCR) technology, which is a heavy consumer of electricity, and the used refrigerants harm the environment. In humid and hot areas, a liquid desiccant AC system integrated with a VCR system has been proposed as a better alternative to traditional standalone VCR system, as it is an energy-efficient system that can remove latent air load, air pollutants from the processed air, and it is energy-saving. In this study, a hybrid liquid desiccant air conditioning (LDAC) system with a capacity of 5.5 kW was designed and developed by integrating these two different technologies, and the vapor pressure of potassium formate (KCOOH) solution at different solution temperatures and concentrations were monitored experimentally to determine the optimal concentration range. Moreover, a comparative study was conducted to analyze the dehumidification performance of lithium chloride (LiCl) and KCOOH solutions. Experiments are designed by using Minitab 19 software, which employs the design of an experimental technique through full factorial design by considering four variables, namely, type of desiccant, inlet air flow rate, inlet desiccant temperature, and inlet air humidity. To study and compare dehumidification characteristics of both solutions, three responses were considered, i.e., the coefficient of performance of a hybrid system, the heat load of dehumidifier, and specific humidity change. Experimental results revealed that 70% of KCOOH solution exhibited comparable vapor pressure to that of 36% LiCl solution. Additionally, the dehumidification ability of the KCOOH solution was better than that of the LiCl solutions.

Mechanism study on magnitude of mass transfer coefficients in liquid desiccant dehumidification and regeneration

• Mass transfer coefficients of regeneration are much lower than dehumidification. • Lower mass transfer coefficients of regeneration are decided by transfer direction. • Water release has a huge free energy barrier but water absorption has not. • Correlations considering parameters of aqueous solution show higher accuracy. Liquid desiccant systems have attracted extensive attention due to huge energy-saving and environmental potential. Mass transfer coefficients are key parameters for system design and performance evaluation. Contrast experiments between liquid desiccant dehumidification and regeneration were conducted here to investigate the magnitude of mass transfer coefficients by using LiBr aqueous solutions. Mass transfer coefficients of dehumidification were found to be much higher than regeneration even under the condition that the mass transfer driving force and inlet parameters except solution temperatures were kept the same. To obtain microscopic explanation, free energy curves of water transport were simulated by molecular dynamics based on umbrella sampling. Results show that large energy obstacle should be overcome for water moving into air, which is unnecessary for water transported into aqueous solution. Lower mass transfer coefficients of regeneration should be attributed to the mass transfer direction rather than higher solution temperatures of regeneration than dehumidification. Dimensionless correlations of mass transfer coefficients using water diffusivity in LiBr aqueous solution and correlations using surface tensions show better prediction performance than dimensionless correlations using water diffusivity in air. This study discloses changing mechanism of mass transfer coefficients and helps develop correlations with high accuracy.

A current efficiency model coupled with desiccant molecular weight for electrodialysis regeneration in liquid desiccant air-conditioning systems

Liquid desiccant air-conditioning system is an energy-efficient choice for heat and moisture independent treatment in buildings, especially for the large dehumidification load. Electrodialysis regeneration is a novel and reliable regeneration method for liquid desiccants, which is suitable for hot and humid climates. In this paper, the performance of the electrodialysis regenerator for regenerating lithium chloride and lithium bromide solutions was studied experimentally, and the current efficiency of the electrodialysis regenerator for regenerating these two solutions was compared. Through analysis, the solute molecular weight was coupled into the current efficiency model, and a new current efficiency model of electrodialysis regenerator for regenerating these two solutions was established, which considers the solute molecular weight of liquid desiccant and can be extended to more liquid desiccants in the future. Furthermore, the performance of the liquid desiccant air-conditioning system using electrodialysis regeneration with these two solutions is compared based on this model. The results show that when lithium chloride solution is applied as liquid desiccant, the system performance coefficient (COP, ratio of cooling capacity to energy consumption) is between 1.16 and 4.49, while the performance coefficient of the system is between 2 and 8.3 when the system uses lithium bromide solution.

Operating characteristics and performance evaluation of carbon dioxide heat pump driven liquid desiccant dehumidification systems: A comparative study

Carbon dioxide heat pump driven liquid desiccant dehumidification takes perfect advantage of the eco-friendly and excellent heating performance of the carbon dioxide heat pump, making regeneration performance significantly improved, being a possible green and efficient air conditioning method. However, the system's operating characteristics and performance are not yet fully clear, hindering practical applications. Given this, a comparative study is conducted in terms of both refrigerants and system configurations. The mathematical models are developed and validated. The results suggested that the power consumption and dehumidification performance of the carbon dioxide heat pump driven liquid desiccant dehumidification systems are reduced and improved by a maximum of 51.67% and 106.89%, respectively, compared with condensing dehumidification. The carbon dioxide heat pump driven liquid desiccant dehumidification systems provide better performance at high dehumidification needs than R134a while offering comparable or even better seasonal performance. The total power consumption and seasonal dehumidification performance are reduced and enhanced by a maximum of 18.84% and 23.21%, respectively. However, owing to the special characteristics and performance of the carbon dioxide heat pump, it is not applicable to the liquid desiccant dehumidification system with solution self-circulation while being less sensitive to the solution-solution heat exchanger. Hence, more efficient systems should be tailored in the future. This study lays the foundation for the optimization and practical applications of the carbon dioxide heat pump driven liquid desiccant dehumidification systems.

Heat and mass transfer analysis of natural convection in a liquid desiccant closed-loop system: The effect of heat source and heat sink temperature

Considering the importance of providing healthy and suitable indoor air condition efficiently, liquid desiccant air condition systems are the focus of study in recent years. The concept of natural convection heat and mass transfer loop is introduced. The system is a closed-loop consisting of two three-fluid hollow fiber membrane heat and mass transfer exchangers played as absorber and regenerator. The system was run under standard conditions with an inlet air flow rate of 6 m3/h. The sensitivity analysis was made to reveal the effect of heat source and heat sink temperature on the system performance. The heat sink and heat source temperature lie between 15–25 °C and 50–70 °C respectively and the outlet air temperature and humidity ratio, moisture removal rate, cooling capacity and coefficient of performance are the evaluating indexes. The results show that despite the convectional desiccant loops the high solution flow rate is not desirable and instead the concentration gradient in the loop is the most important factor. For each heat source temperature, there is an interval of heat sink temperature for which the solution flow rate is the maximum and the concentration gradient is the minimum. Under operating conditions of the present study, the maximum obtained COP is 0.71 which is for temperature pair of (55 °C, 20 °C).

Experimental study on a novel air conditioning system for deep cascade utilization of waste heat

• A novel air conditioning system cascade driven by 80 °C hot water is established. • Both the conventional LiBr solution and cheaper KCOOH solution can be used in this novel system. • The increase of dilute solution flow rate will decrease the COP of system for both solutions. The existing combined absorption refrigeration and liquid desiccant dehumidification systems have the disadvantages of small temperature difference in waste heat utilization and high cost of working pair. For effective and deep utilization of low-grade heat below 80 °C, a novel air conditioning system cascade driven by waste heat is established. In this system, the low-grade heat is used to drive an absorption chiller to produce chilled water for air cooling and then drive a liquid desiccant system for air dehumidification. The cheaper and non-corrosive KCOOH solution is selected as the comparative working pair of LiBr solution to conduct the experimental study in the system. Operation parameters such as inlet temperature, flow rates of both hot water and cooling water that directly affect the application of the system are studied. The results show that the system can be driven by 80 °C hot water, which is much lower than that of the conventional single absorption refrigeration system. Besides, both working pairs can be used for the system. As the inlet parameters of supply air are fixed, the cooling capacity of KCOOH solution is 10% lower than that of LiBr solution. The KCOOH solution has comparable COP compared to LiBr solution only when the dilute solution flow rate is low. The conclusion is summarized that considering the much lower cost, the KCOOH solution is a promising working pair for this novel air conditioning system, nevertheless, the structure of this system needs to be redesigned to match this working pair.

Performance Analysis of a Passive Mixing Strategy assisted Heat-Pump-driven Liquid-Desiccant Air-Conditioning System

In liquid desiccant systems, an operating strategy of mixing small fractions of weak and strong solutions integrated with a closed-loop operating strategy has drawn attention for its ability to improve the system energy performance. This study proposed a passive mixing strategy integrated with the closed-loop strategy for a heat-pump-driven liquid-desiccant (HPLD) air-conditioning system and experimentally analysed its operating performances. Based on the density difference between the weak solution in the absorber sump after dehumidification process and the strong solution in the regenerator sump after regeneration process, the proposed passive mixing strategy can practically mix them without moving parts. The results showed that the passive mixing strategy was found to be feasible to properly maintain the solution temperatures and concentrations of both absorber and regenerator within the target range in the operation of the system. Therefore, the converged dehumidification rate was shown to be 4.3 g/kg and the converged cooling capacity was shown to be 5.4 kW, which satisfied the target performance. Consequently, the closed-loop and the proposed passive mixing strategy can be concluded to be applicable to the HPLD air-conditioning system.

Performance analysis of aqueous LiCl and CaCl2 based falling film dehumidifier with surface modification

• Analysis is carried out on a falling film based liquid desiccant dehumidifier. • The surface is modified with sinusoidal profile to increase the dehumidification. • The sinusoidal wavy profile increases the desiccant surface area by 7%. • Aqueous LiCl solution enhances the dehumidification by 29.15% compared to CaCl 2 . • With aqueous LiCl, the modified surface increases the dehumidification by 33.18%. In summer air-conditioning, conventional vapor compression systems cool the process air to its dew point temperature for dehumidification and further heat it to required supply temperature. This involves extra cooling and subsequent heating. Liquid desiccant systems avert this issue by separately handling latent and sensible loads, while running primarily on low grade thermal energy. Falling film type liquid desiccant dehumidifiers are advantageous over other types, mainly, as they reduce desiccant carryover into supply air stream. The current work aims towards the analysis and the performance improvement of a falling film type dehumidifier with the help of wavy profile of the working surface. Detailed comparison of the two commonly used desiccants, i.e., LiCl and CaCl 2 are carried out to analyse the performance of the dehumidifier. The present work also includes the characterisation of the wave profile and the analysis in terms of various important parameters, such as, the dehumidification effectiveness, the moisture removal rate and the change in specific humidity, missing in earlier studies. In order to study the performance, a simplified 2–D transient finite volume model is taken into consideration to simulate a multiphase, multi-component conjugate heat and mass transfer system using ANSYS Fluent 19.2. The volume of fluid method is used to trace out the liquid–gas interface. With back-end modification of the solver, the thermophysical properties of the liquid film are evaluated using empirical relationships, as a function of temperature and concentration. The penetration model of mass transfer provides the local mass transfer coefficients. The moisture removing the potential of the aqueous solutions of LiCl and CaCl 2 are evaluated at quasi steady-state conditions. The numerical solver is validated with the already published experimental results with a maximum deviation of 10.31%. A sinusoidal wavy profile of the wall introduced in the system enhances the turbulence intensity by 3.8% and the dehumidification performance by 33.18% and 18% for LiCl and CaCl 2 , respectively. It is due to the enhanced liquid–gas interface area. The mean film thickness is found to improve by 15.25% and 13.38% for LiCl and CaCl 2 , respectively. The effect of process parameters on the performance of the dehumidifier is also studied. It has been observed that the dehumidification effectiveness decreases from 86.14% to 31.1% with increase in inlet air velocity from 0.2 m/s to 2.0 m/s. It has also been found that a lower concentration of the desiccant solution and lower velocity of air yield higher dehumidification effectiveness. However, the moisture removal rate of the system will be compromised. Compared to the previously studied cases, the current configuration of the sinusoidal profile with amplitude to wavelength ratio of 1:15, yields superior dehumidification performance.

The Experimental Study of Dehumidification and Regeneration Processes in a Fin and Tube Liquid Desiccant System

The Experimental Study of Dehumidification and Regeneration Processes in a Fin and Tube Liquid Desiccant System

Performance assessment of a liquid desiccant system for formaldehyde removal based on a novel criterion

In the era of requirements in indoor air quality, liquid desiccant (LD) dehumidification is regarded as an energy-saving method removing indoor air contaminants during the dehumidification process, which has made considerable progress in recent years. Many previous studies have confirmed that the heat and mass transfer characteristics associated with absorption characteristics and thermophysical properties in LDs play a vital role in contaminants removal performance. The main purpose of this research is to numerically assess the indoor formaldehyde removal performance of a LD dehumidification system with different LDs. In order to make a fair assessment, a novel criterion based on the same temperature and the same vapor pressure which is the same desiccant condition is proposed. A numerical model integrated with heat, moisture, and formaldehyde transfer is used to predict the system performance. This model can rationally simulate the formaldehyde removal performance of the LD dehumidification system by inputting various operating parameters, including indoor air status parameters and outdoor air status parameters. The simulation results show that the number of mass transfer units of formaldehyde (NTUmf) plays a key role in the formaldehyde removal performance. The formaldehyde removal performances decrease with the increase of temperature and humidity ratio of return air, while they increase with the increase of temperature and humidity ratio of fresh air. With the aforementioned results, the study is expected to be beneficial to further improve the removal ability and potential of LD systems for indoor formaldehyde.