Evaporative Air Research Articles

Developing an experiment-based strong machine learning model for performance prediction and full analysis of Maisotsenko dewpoint evaporative air cooler

Among all direct and indirect water-based evaporative air coolers, Maisotsenko indirect evaporative cooler (MIEC) is the only one which can supply sub wet-bulb air temperature while adding no moisture to the product air. For any given MIEC, four thermal/fluid parameters including dry channel flow rate, wet-to-dry-side air flow ratio, ambient air temperature and ambient relative humidity impact the performance of the MIEC. Sub-wet bulb supply temperature while having maximum cooling capacity happen only for a specific range of the mentioned thermal/fluid parameters. For any ambient condition and dry side air flow, a magic value of air-flow-ratio can maximize the cooling capacity of the cooler. Thousands of data is required to provide a simultaneous multi-aspect analysis of each parameter (while other parameters vary as well) to identify all possible curve behaviors and secrets of this technology. That is why, for the first time in this research, a strong machine learning (ML) model, is developed for MIEC cooler using 625 validated analytical/experimental-based training data (full factorial design). This model is employed to generate around 3600 unseen data to fully clarify the impact of each parameter (on supply temperature, total cooling capacity, useful cooling capacity and wet-bulb effectiveness) while other parameters are variable too. This strategy makes it possible to see all hidden extremum or peak point where the performance of the cooler is maximized or minimized. Interesting results are found in this research. For any ambient condition, there is an extremum point of the air flow ratio at which the total cooling capacity is maximized. The results indicate that as the dry side air flow increases, this extremum value decreases. For instance, under an ambient condition of 18 °C and 9 % relative humidity, the extremum point of the air flow ratio is 0.45 when the dry side air flow is 0.8 L/s and 0.25 when the dry side air flow is 4.8 L/s. In real-world commercial cooler, this can be simply happened by appropriate re-adjusting the dry and wet side fan speeds.

Thermodynamic performance assessment of a solar-driven desiccant evaporative air cooling system (SDEAC) for outdoor environments- a dynamic study

In this work, a novel dynamic model of a solar-driven desiccant evaporative air cooling system for outdoor environments is proposed, namely the SDEAC system. The effects of operating and designing parameters on the performance of the SDEAC system are analyzed. The results indicate that the sensible cooling capacity, the latent cooling capacity, and the COP decrease monotonically as the rotational speed of the desiccant wheel increases. When the ratio of dehumidification area to total area (r1) is 0.5, the performance of the SDEAC system is optimal under the condition of sufficient solar radiation. The ratio of the dehumidified air flowrate to the regenerated air flowrate has a small effect on the cooling capacity but has a large effect on the COP. The SDEAC system has a higher sensible cooling capacity and total cooling capacity compared to the EAC system. Moreover, although the COP of the SDEAC is lower than that of the EAC system, it is still maintained at a relatively high level. The SDEAC system with a supply air flowrate of 670 m3/h to cool the outdoor air saves about 1283∼1617 kWh of electricity and 788 kg–1139 kg of carbon emission reduction compared to a conventional vapor compression air conditioning system in different cities during the period of June to August.

Effectiveness of cooling interventions on heat-stressed dairy cows based on a mechanistic thermoregulatory model

Addressing heat stress in dairy farming is a substantial challenge, and there is an increasing need for efficient cooling systems, even in regions with moderate climates. Accurately predicting the efficacy of diverse cooling options under different climatic conditions is crucial for reducing heat stress in modern high-producing dairy cows, aligning with sustainability goals. This study assessed the effectiveness and feasibility of different cooling measures, including fans, sprinklers with fans, and evaporative air cooling, using a dynamic thermoregulatory model. This 3-node dynamic model was developed based on recent animal data simulating the processes of dairy cows' physiological regulation and heat dissipation under various environmental conditions. The cooling methods were based on two principles: enhancing heat loss from cows using fans with/without sprinklers; lowering the ambient temperature by evaporative air cooling. The predicted results were discussed and partly validated using the experimental data from the literature. The predictions indicated that fan cooling alone was effective in ambient temperatures below 26 °C, while higher temperatures required a combination of fans and sprinklers for effective heat stress alleviation. Consideration of individual cow characteristics and environmental factors, including fan speed and wetting area, is crucial for optimal cooling. In regions with high relative humidity, evaporative air cooling could be counterproductive to some extent. The model's predictions largely aligned with experimental data, demonstrating its capability to forecast cooling effects under various climatic conditions. Future model improvements included refining calculations for water holding capacity, wetted skin area, and dry time, depending on the influence of spraying time and rate.

Mitigating dengue incidence through advanced Aedes larval surveillance and control: A successful experience from Pakistan.

Dengue fever is a viral disease caused by one of four dengue stereotypes (Flavivirus: Flaviviridae) that are primarily transmitted by Aedes albopictus (Skuse) and Aedes aegypti (L.). To safeguard public health, it is crucial to conduct surveys that examine the factors favouring the presence of these species. Our study surveyed 42 councils across four towns within the Bhakkar district of Punjab Province, by inspecting man-made or natural habitats containing standing water. First, door-to-door surveillance teams from the district health department were assigned to each council to surveillance Aedes species and dengue cases. Second, data collection through surveillance efforts, and validation procedures were implemented, and the verified data was uploaded onto the Dengue Tracking System by Third Party Validation teams. Third, data were analysed to identify factors influencing dengue fever cases. The findings demonstrated the following: (1) Predominantly, instances were discerned among individuals who had a documented history of having travelled beyond the confines of the province. (2) Containers associated with evaporative air coolers and tyre shops were responsible for approximately 30% of the Aedes developmental sites. (4) Variability in temperature was responsible for approximately 45% of the observed differences in the quantity of recorded Aedes mosquito developmental sites. (5) Implementation of dengue prevention initiatives precipitated a 50% reduction in Aedes-positive containers, alongside a notable 70% decline in reported cases of dengue fever during the period spanning 2019 to 2020, while the majority of reported cases were of external origin. Aedes control measures substantially curtailed mosquito populations and lowered vector-virus interactions. Notably, local dengue transmission was eliminated through advanced and effective Aedes control efforts, emphasising the need for persistent surveillance and eradication of larval habitats in affected regions.

Investigation of Solar-Powered Evaporative Air Cooling System for Industrial Application

Investigation of Solar-Powered Evaporative Air Cooling System for Industrial Application

EVAPORATIVE AIR COOLER THERMAL PERFORMANCE FOR RESIDENTIAL USE

This paper investigates an Evaporative Air Cooler (EAC) thermal performance and energy efficiency, when reducing the air temperature. EAC equipment typically consists of fan, small hydraulic pump and cooling pads. That device is able to provide ventilation only or air cooling trough water evaporative process that increases the air humidity (absolute and relative) and, as consequence, air temperature decreases (dry and wet bulb). The methodology adapts some aspects from ABNT - Brazilian Technical Standards Normative, for air conditioning devices. During tests, the fan rotor operates in 3 (three) angular speeds (RPM) in different ambient conditions for inlet air. Appropriate instrumentation and measurements registration allow to register the behavior of thermal parameters as: dry and wet bulb temperatures (Tdb and Twb, °C), air relative humidity (RH, %), enthalpy (kJ.kg-1), and water mass flow (kg.s-1). Thus, main results are for overall efficiency (η, %) considering the energy conversion from electricity to air flow hydraulic power, and cooling effectiveness (ε, %) is based on heat exchange between water evaporation and airflow rate. As main conclusions, we point out that: a) ↓Tdb for ↓mAir, reaching ΔT~5.0°C and corresponding ΔΦ~20%, when comparing outlet and inlet airflow parameters; b) EAC efectiveness reaches maximum values for lower rotor angular speeds (εEAC ~90%@1300 RPM), in comparison to higher ones; c) For a constant rotor angular speed, EAC performance (CP, εEAC and others) is strongly dependent on air ambient conditions; mAir increases from ~13.8 kg.s-1 up to ~16.5 kg.s-1 when rotor angular speeds goes from 1300 RPM to 1500 RPM.

Numerical Study of an Evaporative Exchanger Based on Fired Clay

Evaporative air coolers are one of the alternatives to conventional air conditioners for cooling the air in the building. These systems consume less energy and contribute to the reduction of greenhouse gases. This work is a numerical study of an evaporative exchanger based on fired clay plates using COMSOL Multiphysics software. It was interested in hygrothermal transfers for air cooling. This study allowed to highlight the impact of the gap between the fired clay plates, the speed of the area as well as the air temperature at the inlet of the exchanger on the evolution of temperature and relative humidity of the air along the fired porous clay plates. The thermal efficiency of the exchanger was subsequently evaluated. This study allowed to note that there is a drop of 14 K along the porous plates of fired clay. Speed has an influence on outlet temperatures and relative humidity. For a speed of 0.2m/s, the temperature variation is 16 K and for speeds ranging from 2 m/s to 4m/s, the temperature variations are approximately 17 K. For gaps in porous plates of fired clay less than 2cm, the thermal efficiency varies 92% to 98%.

Experimental investigation of using the evaporative air cooling technique to enhance the performance of the photovoltaic module

Abstract In this experimental study, two techniques of photovoltaic thermal (PVT) collector with active cooling were used to enhance the performance of the photovoltaic (PV) module. The first technique was prepared by integrating the PV module with a forced air duct (PVTFC). At the same time, the second technique was the PV module integrated with a forced air duct including a direct evaporative cooling unit (PVTDEC). In these two techniques, the air was forced by an electrical centrifugal fan with variable speeds (1.5, 2.5 and 3.5 m/s) placed at the end of the duct. The output electrical characteristics of the PVTFC and PVTDEC modules were compared with the reference PV module. The obtained results showed a significant decrease in the temperature of the PV module, where the reduction in the temperature of the PV module was achieved between 5°C and 16°C and 21°C and 25°C in PVTFC and PVTDEC techniques, respectively. Accordingly, the voltage was dropped to 15.1 and 15.8 V in PVTFC and PVTDEC, respectively, as compared with the sharp decline of voltage for the reference PV module, which recorded 14.2 V at a maximum PV module temperature of 69°C. In addition, the maximum enhancement percentage of PV efficiency was achieved at a maximum airflow rate of 0.22 kg/s, where it was recorded between 3.5% and 6.2% in the case of PVTFC and 7% and 9.3% in the case of PVTDEC.

Efficient harvesting of renewable evaporative energy from atmospheric air through hierarchical nano/microscale shaping of air-water interface

Renewable evaporative energy from atmospheric air is a recently emerged research field that demonstrates the great potential for significant energy savings in the air conditioning of buildings, data/big-data/integrated-big-data centers, agricultural storage facilities, and greenhouses. Here, we develop a method for an essential increase in the harvesting efficiency of renewable air evaporative energy by enhancing the water evaporation rate through the shaping of the air-water interface (AWI) by the menisci formed in superhydrophilic hierarchical surface nano/microstructures. Using this method, we achieve a 10-fold rise in the evaporation rate for the microscale AWI shaping. For the first time, we discover the superevaporation effect that provides an unprecedented 130-fold rise in the evaporation rate at the hierarchical nano/microscale AWI shaping. Furthermore, based on these findings, for the first time, we elaborate a novel material with an engineered AWI for a significant increase in the harvesting of renewable air evaporative energy in the dew point (Maisotsenko cycle) indirect evaporative air conditioning systems whose operation is fundamentally based on utilizing renewable air evaporative energy. The dew point cooling device fabricated using this novel material shows significantly superior cooling performance, validating the substantially enhanced harvesting of the air's evaporative energy. Our findings can essentially advance the emerging field of renewable air evaporative energy and, besides the air conditioning technology, can provide significant efficiency enhancements in water purification/desalination, thermal management, gas turbine power generation, and waste heat recovery technologies.

Numerical simulation of integrating an air conditioner with an evaporative air cooler

During the summer, air conditioning is increasingly used in commercial and residential structures to provide thermal comfort. The elevated condenser pressure caused by high ambient temperatures has led to a significant increase in electricity consumption in dry, hot climates. Therefore, this article presents the results of a numerical simulation investigation into the feasibility of enhancing the performance of a conventional air conditioning unit by applying a direct evaporative cooling system. The objective is to increase the cooling capacity while decreasing power consumption. The program used a small window-type air conditioner configured to simulate various weather conditions. The numerical findings indicate that incorporating evaporative cooling aids improved the system's ability to overcome numerous obstacles, resulting in a 10–20% increase in refrigeration capacity. Additionally, power consumption was reduced by approximately 3%, and the discharge temperature fell by 6–10°C. The predicted mean vote standard (PMV) for thermal conditions for human occupants yielded favorable outcomes (normal-type). Despite the challenging climate conditions prevailing during the five sweltering summer months, water production demonstrated good results, particularly in September.

Experimental and analytical study of the energy and exergy performance for different evaporative pads in hot and dry climate

In this work, effects of using different evaporative cooling pads (ECPs) on the energetic and exergetic efficiency of a direct evaporative air cooler (DEAC) have been theoretically and experimentally investigated. Three types of ECPs were used, i.e., honeycomb cellulose cooler pad (HCCP), shading-cloth cooler pad (SCCP), and aspen wood wool cooler pad (AWWCP). For SCCP and AWWCP, a 3-cm pad thickness was used, while for the HCCP, three different values of pad thickness were used, i.e., 3, 5, and 7 cm. Tests were carried out using air velocities of 8, 14, and 19 m/s, measured at the DEAC outlet. Engineering equation solver (EES) used for performing the required calculations of the various parameters affecting the thermal performance of the DEAC, i.e., dry bulb temperature at exit (Tdbo), relative humidity at exit (RHo), mass of water evaporated, saturation efficiency, energetic efficiency (ηen), exergetic efficiency (ηex), and the overall exergetic efficiency (ηexoverall). Results showed the great effectiveness of HCCP compared to the other studied types. HCCP showed the highest energetic efficiency reached 103 % for 3 cm thickness of the ECP, and the highest exergetic efficiency of about 19 %. All with the highest temperature difference, achieving 10.3 °C.

Optimizing the performance of cotton Bundle-based solar evaporative cooling system using a CFD Model: Model Development, Validation, and optimization

A Solar Evaporative cooling system is an energy-efficient, environmentally friendly, and low-cost air conditioning system. It is an economical air conditioning system for any type of cooling application, such as cold storage of horticulture products and ventilation systems. In this work, a computational fluid dynamics CFD-based model was used to study the parametric effect and to optimize the evaporative air cooler. The system used cotton bundles for the absorption and evaporation of water. Heat and mass transfer processes were coupled using user-defined functions. The accuracy of the model was validated by the experimental results. The predicted results well agreed with experimental results; with average errors of 13.39% (pressure drop), 2.347% (supply air temperature), and 2.22% (supply air relative humidity). The effects of airspeed, porosity, and thickness of the bundle on the cooling performance of evaporative cooling were studied. The incoming air had a dry-bulb temperature of 33 °C and a relative humidity of 28.4%. The study assessed the velocity, temperature, and relative humidity distribution in a cooling chamber. The optimum cooling system reduced the air temperature by up to 12℃ and increased relative humidity to 94% at 1.69 m/s inlet air velocity, 20 cm bundle thickness, and 30.23% porosity.

An insight into environmental footprints of emerging air-conditioning systems towards sustainable cities

In this study, the environmental impacts of six conventional and modern air conditioning systems, including vapor-compression air conditioning (VAC), hybrid membrane-based air conditioning (HMBAC), desiccant enhanced evaporative air conditioning (DEVap), solar HMBAC, solar DEVap, and inverter VAC, are analyzed using a cradle-to-gate life cycle assessment (LCA) approach. The assessment is based on climate change, ozone depletion, terrestrial acidification, freshwater eutrophication, human toxicity, photochemical oxidant formation, ecotoxicity, water depletion, and fossil fuel depletion impacts. The LCA findings reveal that membrane-based systems (HMBAC and DEVap) are highly environmentally-friendly in comparison to the regular VAC systems (household split coolers), showing the capability of membranes in developing efficient air conditioning systems. In addition, solar-assisted systems reduce seven out of eleven environmental impacts, while they cause severe eutrophication, marine and freshwater ecotoxicity, and human toxicity consequences. Furthermore, it is unveiled that the inverter can reduce up to 38% of the environmental impacts of VAC systems which are the most common air conditioning system in buildings. Therefore, the manipulation of the inverter system in VACs can be considered as one of the short-term solutions in reducing the environmental footprints of air conditioning. Finally, the sensitivity analysis is applied to show the reliability of the outcomes.

Pad type impact on the economical direct- evaporative air cooler efficiency

ABSTRACT Theoretical and experimental investigations were performed to study the impact of four pads in series on the thermal performance of an economical evaporative air cooler that works at a low voltage (12 Volts). Straw and cardboard pads were studied. The studied parameters were dry bulb temperature, the dry bulb temperature difference between inlet and outlet air, cooling efficiency, and the total heat transfer rate. Three draft fan speeds were considered, i.e. 2.8, 3.5, and 4.7 m/s. The results showed that adding multiple pads in series had an insignificant impact on the evaporative cooler thermal performance compared to one pad. The straw pads’ cooling efficiency at 2.8 m/s was lower than that of the cardboard, i.e. 91.4% and 93.1%, respectively. Also, it was found that the velocity of the air passing through the cooler significantly impacted the cooling efficiency. The theoretical results for the lowest speed of 2.8 m/s showed an increase in the cooling efficiency of the cardboard pad by 46.6% compared to the speed of 4.7 m/s due to a long time for heat transfer. Therefore, the best air velocity entering the cooled space was 2.8 m/s.

Performance of Gas Turbine Power Plant with Evaporative Air Pre-Cooler System Using Energy and Exergy Concept

One of the main challenges in building a Solar Power Generation System at home or a Home Solar Power Plant (Home SPP) is choosing component specifications according to price. The main components of Home SPP are photovoltaic (PV) panels, inverters, and wiring systems. Given the strict price constraints, the selection of parts available on the commercial market is generally of low quality. However, low-quality components can still provide a significant advantage by optimizing the plant design. This research proves that the proper configuration can reduce electricity bills by 52.2%. This configuration does by choosing a Grid Tie Inverter (GTI) with a high working voltage and a 12 Volt PV configured in a parallel series circuit to work at 24 Volts. In addition, the 12 Volt PV panels configured in series to 24 Volts are proven to increase the conversion efficiency

Design and Development of Solar Powered 360degree Automatic Air Cooler

Abstract: Evaporative coolers lower the temperature of air using the principle of evaporative cooling, unlike typical air conditioning systems which use vapor-compression refrigeration or absorption refrigerator. Evaporative cooling is the conversion of liquid water into vapor using the thermal energy in the air, resulting in a lower air temperature. The energy needed to evaporate the water is taken from the air in the form of sensible heat, which affects the temperature of the air, and converted into latent heat, the energy present in the water vapor component of the air, whilst the air remains at a constant enthalpy value. Vapor-compression refrigeration uses evaporative cooling, but the evaporated vapor is within a sealed system, and is then compressed ready to evaporate again, using energy to do so. Simple evaporative coolers water is evaporated into the environment, and not recovered. In an interior space cooling unit, the evaporated water is introduced into the space along with the now-cooled air; in an evaporative tower the evaporated water is carried off in the airflow exhaust. To Develop the Energy efficient, environment friendly direct evaporative air conditioning system having low operating cost suitable for hot and dry regions To Manufacture advanced 360-degree Rotating air cooler which rotates and provide air cooling in all directions. It can be used for domestic as well as Industrial applications. The temperature of dry air can be dropped significantly through the phase transition of liquid water to water vapor (evaporation). This can cool air using much less energy than refrigeration. In extremely dry climates, evaporative cooling of air has the added benefit of conditioning the air with more moisture for the comfort of building occupants

THE INFLUENCE OF DIFFERENT FACTORS ON THE MAISOTSENKO CYCLE EFFECTIVENESS

An important problem in the heat industry is the significant cost of energy resources for air conditioning. Therefore, energy-efficient refrigeration systems based on renewable energy sources and evaporative air cooling, as well as air-conditioning systems according to the Maisotsenko cycle using psychrometric energy of the environment are of great importance. This paper presents the results of experimental and numerical research of the influence of various factors on the efficiency of indirect evaporative heat and mass transfer apparatus on the M-cycle on the basis of a new unit cell.
 An experimental stand of a heat and mass transfer apparatus with vertically arranged plate channels was developed for experimental research. Experimental studies of heat and mass transfer in the new unit cell were conducted in a wide range of Reynolds numbers 200…1200, temperature 16… 30 °С, relative humidity 30… 50 %. The calculated study was performed using a modified ε-NTU method. Studies have shown that the thermodynamic efficiency of a wet bulb thermometer at a Reynolds number below 500 exceeded one. According to the results of computational studies, the influence of cell length and surface intensification of dry channels on thermodynamic efficiency was determined. Shown the effect of changes in thermodynamic efficiency in the range of 86…94 % increase in efficiency by 1 % leads to an increase in cell length by 7 %. The value of the enhancement factor increases with increasing air flow regime, so when the heat and mass transfer surface area increases by 50 % and the Reynolds number 200, the thermodynamic efficiency increases by 14 %, and with the Reynolds number 800 – by 28 %. The dependence of the thermodynamic efficiency of the cells at the dew point on the relative humidity of the inlet air have a maximum, which with increasing Reynolds number shifts toward larger values of relative humidity.
 Unlike traditional air conditioning devices, the M-cycle heat and mass exchanger does not use a steam compression cycle, so energy costs are spent only on the operation of the fan to pump air, which is a more environmentally friendly and energy efficient way of air conditioning.

Solar Power Cooler With Tracking System

-The present air cooling methods is are evaporative coolers, air conditioning, fans and dehumidifiers. But running these products is need a source called electricity. The producing of electricity is ultimately responsible for hot and humid conditions also i.e. global warming. In hot and humid conditions and the need to feel relaxed and comfortable has become one of few needs and for this purpose utilization of systems like air-cooling and refrigeration has increased in quickly. These systems are most of the time not suitable for villages due to longer power cut durations and high cost of products. Solar power systems being considered as one of the path towards most sustainable energy systems, considering solar-cooling systems in rural areas would comprise of many attractive functions . This technology can efficiently serve large latent loads and greatly improve indoor air quality by allowing more ventilation while tightly controlling humidity. Despite improving performance and mandatory energy efficiency requirements, peak electricity demand is growing and there is currently no prevalent solar air cooling technology suitable to residential application especially for villages, schools and offices. This project model reviews solar powered air cooler for residential and industrial applications. Key Words: Solar Panel, Arduino Uno, Fresh Cool Air

Evaluation of Human Thermal Comfort and Microbial Analysis in an Evaporative Cooling Room

In Thailand, evaporative air coolers (EAC) are common in outdoor and semi-outdoor areas. Exploring the possibility of using an EAC in an indoor area, this research aims to determine its benefits in a natural, ventilated room during summer and winter. In terms of human thermal comfort, these benefits are evaluated through the CBE Thermal Comfort Tool with environmental parameters collected from the testing room. Bacterial growth due to increased humidity is analyzed based on bacterial counts in the opened Petri dishes. The results from the testing room with EAC show that air temperature reduces by 1.4 - 4.4 °C during winter and 3.3 - 3.5 °C during summer with a relative humidity increase of 2.3 - 13.1%. Thermal comfort was found to depend on indoor air temperature and air velocity. During winter, it was slightly improved by the use of an EAC, with an elevated percentage of people dissatisfied (PPD) due to low air temperature and high air velocity. The evaporative, cooled air also enhances thermal comfort in summer with less PPD. Increasing air velocity to provide thermal comfort is more suitable in summer than in winter. More bacteriological colonies formed in the room with an EAC than in the room with natural air by 33-55 units. The air quality in the EAC room according to IMA standards was Fair-Good, dropped from Good-Very Good in the natural-air room. This study confirms that the EAC improved thermal comfort in the natural ventilation room during both summer and winter. However, the room air was impure with the increase in microbial activity due to high air temperature and humidity.

Modeling and performance analysis of a hybrid-connected two-stage liquid dehumidification fresh air system based on CaCl2/LiCl double solution

In this paper, a novel hybrid-connected two-stage liquid dehumidification fresh air (HTLDFA) system by combining CaCl2 with LiCl aqueous solutions is proposed, in which the ambient air is adopted directly as the regeneration air of CaCl2 solution and the air pre-dehumidified by part of the strong CaCl2 is used for regenerating the LiCl solution. In this way, regeneration air of lower humidity for LiCl solution can improve the regeneration efficiency of the LiCl solution and reduce its regeneration temperature. The NTU optimization of main units and the action mechanisms of other fluid parameters on the dehumidification performance of that system are examined. Numerical simulation results show the proposed system is more efficient in utilizing the low-temperature heat sources and the energy and exergy efficiencies can reach about 0.57 and 0.47, respectively. For processing humid fresh air of 0.56 kg/s by using this system, the NTUs of main components are in the optimal range of 2–4 and the flow-rates of two-stage regeneration air are not less than 1.6 kg/s and 0.8 kg/s as well as their driven hot water flow-rates should be more than 1.9 kg/s and 0.8 kg/s. In the HTLDFA system, the water flow-rate of the second-grade cooling tower by using the indoor exhaust air as evaporative air only needs about half that of the first-grade cooling tower of using surrounding air as evaporative air. As for the hybrid-connected mode of CaCl2 and LiCl solutions, the flow-rate of CaCl2 solution entering the first-grade dehumidification shares 60 percent of its total flow-rate to achieve the optimal system performance. Performance comparison with the previous two-stage liquid dehumidification system shows that the proposed system has greater efficiency in using low-grade heat sources and achieves higher EER and exergy efficiency.