Desiccant Cooling System Research Articles

Analysis and Optimization of a Biomass Heated Two-Stage Desiccant Cooling System Used for Greenhouse Cultivation in Hot and Humid Climates

Abstract This paper presents a multi-objective optimization of a biomass heating-based two-stage desiccant-supported greenhouse cooling system used for Orchids cultivation in hot and humid weather conditions. The simulation model has been developed considering thermodynamics, economic, and environmental aspects. The thermal coefficient of performance (COPth) of the system and greenhouse temperature have been predicted for the five most impactful months (March, May, August, September, and December) corresponding to the respective seasons of spring, summer, monsoon, autumn, and winter of a calendar year. The system maintains the peak average greenhouse temperature at a maximum of 26 °C during the prominent sunshine period (12 h) in May while ensuring a minimum of 18 °C during nighttime. In terms of system components, the residue boiler stands out as the significant contributor to exergy destruction (45%), followed by regeneration heater 1 (22%), desiccant wheel 1 (7%), and the heat recovery water heater (6%) during the critical operational month of August. Multi-objective optimization has also been conducted using the optimization toolbox provided in matlab-R2017a to determine the optimal performance and operating conditions of the two-stage desiccant cooling system. The optimal conditions display the corresponding total cost rate, considering capital and maintenance costs, operating costs, CO2 penalty costs, and exergetic efficiency.

Investigation of a Wheel Liquid Desiccant Cooling System Performance via ANSYS CFX

A liquid desiccant cooling system is an alternative air-conditioning system with significant energy-saving potential. This system is commonly used in the industrial sector, such as in dehumidifiers. The key component of the liquid desiccant cooling system is its dehumidification performance. Therefore, a study on a liquid desiccant dehumidifier has been conducted to predict its performance using computational fluid dynamics analysis. In these simulations, the effects of the temperature of the liquid desiccant and the velocity of air flow on the absorption process between the liquid desiccant and air were studied. The same applies to the velocity profile, which helps determine the airflow pattern within the dehumidifier. The model was constructed using ANSYS FLUENT and Autodesk Inventor. The model is the rotary desiccant wheel dehumidifier which was used to dehumidified the air.. ANSYS CFX was used for simulating the velocity profile to achieve the airflow pattern in the dehumidifier. The volume of fluid was selected as the multiphase method for the second simulation process. The temperature and mass fraction of water were monitored within the air during the counterflow simulation between the liquid desiccant and the air. The liquid desiccant chosen for this study was LiCl. The simulations were conducted at specific air velocities, and the behavior within the dehumidifier was observed. The analysis results revealed that the air entering the rotary desiccant wheel dehumidifier experienced a drop in velocity after passing through the desiccant wheel in the middle. Additionally, turbulence occurred after the air passed through the wheel and the dehumidifier’s wall. Based on these findings, the design of an optimal dehumidifier and the selection of an appropriate air velocity for cooling can be carried out.

Experimental Demonstration and Energy Consumption Analysis of Solar Thermal Desiccant Cooling System with Evaporative Condenser

Experimental Demonstration and Energy Consumption Analysis of Solar Thermal Desiccant Cooling System with Evaporative Condenser

Optimization of the Liquid Desiccant Cooling Systems in Hot and Humid Areas

Air-conditioning systems in hot and humid regions account for over 50% of total energy usage. Integrating an indirect evaporative cooling (IEC) and a liquid desiccant dehumidifier (LDD) as the liquid desiccant cooling system (LDCS) presents an energy-saving and emission-reducing solution to replace traditional mechanical vapor compression refrigeration (MVCR) systems. This integration overcomes the regional limitations of IEC in hot and humid areas. The newly developed LDCS uses exhaust air as the working air source and solar energy as the heat source for desiccant solution regeneration. This study aims to develop an empirical model for the outlet parameters of the LDCS, propose an optimization strategy for its operating parameters, and assess the potential and energy performance through parameter analysis and multifactor optimization. By conducting sensitivity analysis and optimizing six critical parameters based on a response surface model (RSM), the system outlet temperature, relative humidity, and coefficient of performance (COP) are improved as the optimization objectives. The regional capability is demonstrated in three selected hot and humid cities. The results indicate that the LDCS can significantly increase the COP by 57.3%. Additionally, it can meet the dehumidification demand when operating with 25% of the air extracted in the RIEC during months with high humidity and temperature. This study will facilitate the application of IEC and LDD technologies, guide the design and operation scheme of the system, and promote energy-saving and emission-reducing solutions in hot and humid regions.

Review on Polymer Materials for Solid Desiccant Cooling System

AbstractAs an alternative form of vapor compression air conditioning devices, solid desiccant cooling (SDC) techniques have increasingly been explored recently. The overall performances of SDC primarily rely on the capability of dehumidification and regeneration of desiccant. A desiccant with a great uptake capability and excellent regeneration potential is preferred in an SDC system. Although traditional desiccants like silica gels and zeolites are able to absorb moisture at moderate levels, hygroscopic polymers show a superior ability in moisture sorption and desorption. Significant research has been conducted to investigate the hygroscopic polymers in SDC for household and industrial applications. Here, first, an introduction to SDC systems is presented, and then hygroscopic polymers from natural and synthetic origins are discussed. Synthetic polymers discussed are metal–organic frameworks (MOFs), covalent organic frameworks (COFs), covalent triazine frameworks (CTFs), amorphous porous organic polymers (POPs), polyelectrolytes, and polymer‐based composites. Their dehumidification behaviors in SDC systems, primarily desiccant‐coated heat exchanger (DCHE) systems, are compared and summarized. Binders employed in SDC systems are also summarized, as a proper binder enhances the overall performance of the desiccant system. It can be anticipated that hygroscopic polymers and binder materials would witness extensive applications in the future.

Theoretical Evaluation of Solar Assisted Desiccant Cooling System for a Small Meeting-Hall

The performance of a solar assisted desiccant cooling system for a meeting-hall located in the College of Engineering/University of Baghdad was evaluated theoretically. The system was composed of four components; a solar air heater, a desiccant dehumidifier, a heat exchanger and an evaporative cooler. A computer simulation was developed by using MATLAB to assess the effect of various design and operating conditions on the performance of the system and its components. The actual weather data on recommended days were used to assess the load variation and the system performance during those days. The radiant time series method (RTS) was used to evaluate the hourly variation of the cooling load. Four operation modes were employed for performance evaluation. A 100 % ventilation mode and 3 recirculation modes, 30 % , 60 % and 100 % recirculation of room air. The concept of variable air volume was employed as a control strategy over the day, by changing the supply airflow rate to match the variation in the cooling load.The results showed that the reduction in moisture content at regeneration temperatures from 55 o C to 75 o C lead to adequate removal of the high latent load in the meeting-hall. Also, the 30 % recirculation of return air resulted in comfortable indoor conditions satisfying the ventilation requirements for most periods of system operation. In addition, the COP of the system was high compared with the conventional vapor compression system. It varied from 1 to 13, when considering solar energy used to regenerate thedesiccant material as free energy.

Investigation of thermal comfort conditions by heat pump Hybridized with phase change Material-based solar desiccant cooling system

In response to the challenge of providing energy-efficient thermal comfort in hot and high-humidity cities, this study investigates innovative cooling systems that can mitigate issues of overcooling and excessive energy consumption seen in conventional air conditioning systems. Also, conventional cooling systems contribute to global warming by emitting high levels of greenhouse gases. In this research, two systems Phase Change Material (PCM)-based Solar Desiccant Cooling System (PSDC) and Heat Pump Hybridized with a PCM-based Solar Desiccant Cooling System (HP-PSDC) were investigated for a typical residential house located in Doha (Qatar), Vancouver and Toronto (Canada), and Bangkok (Thailand). According to the findings, the PSDC system provides thermal comfort conditions in Vancouver and Toronto with COP of 1.05 and 1.44, respectively. While in Doha and Bangkok, the innovative system that is HP-PSDC system has better performance when the COP (Coefficient of Performance) of the former is 4.98 and the latter is 4.5. The novelty of this work lies in the approach to balancing thermal comfort conditions with energy consumption. Predicted Mean Vote (PMV) and Predicted Percentage of Dissatisfied (PPD) were determined to set design criteria for the selection of the proper system based on the weather conditions of each city by using Design of Experiment (DOE) analysis. According to DOE, the dry bulb temperature, the wet bulb temperature, and the absolute humidity of the ambient air are three key characteristics that must be considered when choosing the appropriate system to provide thermal comfort conditions. It was found that if the wet bulb temperature of the building location is more than 21.5 °C, utilizing the HP-PSDC system can guarantee thermal comfort condition. However, for wet bulb temperatures less than 18.5 °C, the PSDC system is recommended. This research presents implications for the design of sustainable cooling systems, offering energy efficiency improvements and climate-specific system selection guidelines.

Energy analysis of a novel solar tri-generation system using different ORC working fluids

A novel solar tri-generation system combined with an Organic Rankin Cycle (ORC), humidification dehumidification water desalination system (HDH), and a desiccant cooling system (DCS) for electrical power generation, water desalination, and air-conditioning is investigated numerically. Such a system is intended for tiny and medium-sized structures in Gulf nations that are abundant in solar energy but deficient in fossil fuels and water supplies. Detailed parametric studies of the operating and design parameters on the system's productivities and performance are carried out using different kinds of organic fluids (n-Octane, R245fa, R113, R123, Cyclohexane, and Toluene). It is noticed that the proposed system can provide the highest electrical power, fresh water, and space cooling capacity of 152.5 kW, 77.29 kg/s kg/h, and 27.11 kW, respectively, using Cyclohexane. Moreover, the maximum energy utilization factor obtained is 0.3018 using R123 and the improvement percentage of using R123 instead of n-Octane is 20%. Finally, general numerical correlations of a system's productivities and its performance are developed and presented within reasonable errors for different organic fluids.

Assessment of a desiccant cooling system in a traditional and innovative nanofluid HVAC system

The topic of energy saving is a constant in everyday life, and it is widespread all over the world. Space heating using solar panels is the most used renewable source of energy, but the application of solar energy for cooling the fluids used for refrigeration is growing very fast. Among the techniques used for refrigeration, this work focused on Desiccant Cooling. In particular, with the use of dynamic simulation software, it was possible to study the heat supplied and the energy consumption of a Heating Ventilation Air Conditioning (HVAC) system of a university building and to compare consumption with those of a Desiccant Cooling system applied to the same building. Four different cases were simulated: two related to the HVAC system, one of which operates with water and glycol and the other one with nanofluid, and the other ones to the Desiccant Cooling system with both types of fluids mentioned above. Keeping the same energy demand of the building in all the simulations, it was found that in summer the Desiccant Cooling system had higher performance than the traditional HVAC system and that the use of the nanofluid in both types of conditioning systems further increased the performance of 21%. Simulations were carried out using TRNSYS software.

Performance Evaluation of a Solar Heat-Driven Poly-Generation System for Residential Buildings Using Various Arrangements of Heat Recovery Units

Poly-generation systems are a feasible alternative to conventional energy production techniques in buildings. A poly-generation system allows for the concurrent production of electricity, heat, cold, and fresh water, with considerable advantages regarding technology, finances, energy recovery, and the environment. In the present study, the organic Rankine cycle (ORC), the humidification–dehumidification desalination system (HDH), and the desiccant cooling system (DCS) are merged with three unique solar-driven poly-generation systems (BS, IS-I, and IS-II) and numerically examined. The proposed options provide energy, space cooling, domestic heating, and potable water to buildings of small/medium scale. Using n-octane ORC working fluid, the impact of operational circumstances on system productivity and execution characteristics was considered. The findings show that (i) the suggested poly-generation systems can provide electrical power, conditioned space cooling, local heating, and fresh water, whereas keeping the conditioned area pleasant, (ii) the IS-I system achieves the best system performance among all compared arrangements (BS and IS-II); (iii) the attained extreme values of W˙net, m˙fresh, Q˙cooling, Q˙heating, and TGOR are 102.0 kW (all systems), 214.70 kg/h (IS-II), 29.940 kW (IS-II), 225.6 kW (IS-I), and 0.6303 (IS-I), respectively.

Energy Performance Assessment of a Novel Solar Poly-Generation System Using Various ORC Working Fluids in Residential Buildings

Poly-generation systems are an exciting new technology that provide an alternative to separating existing energy production methods in buildings. A poly-generation system enables the efficient simultaneous production of heating, cooling, fresh water, and electricity, resulting in many technological, economic, energy recovery, and environmental advantages. This study numerically investigates three proposed novel solar-driven poly-generation systems (BS, IS-I, and IS-II) integrated with organic Rankine cycle (ORC), humidification-dehumidification desalination system (HDH), and desiccant cooling system (DCS) with different heat recovery system arrangements. The suggested systems supply residential structures with energy, space conditioning, domestic heating, and fresh water. The effects of system operating circumstances on productivity and performance characteristics and several organic working fluid types (n-octane, R245fa, R113, isopentane, and toluene) on optimum system performance have been investigated. The results show that (i) the average enhancement percentage of TGOR using integrated poly-generation systems over the separated ones is 68.5%, 68.5%, and 95.5% for BS, IS-I, and IS-II systems, respectively; (ii) when comparing the three systems, the IS-I system outperforms the other systems (BS & IS-II); and (iii) the maximum values of W•net, m•fresh, Q•cooling, and Q•heating, obtained for different proposed systems using n-octane are 102 kW (all systems), 214.7 kg/h (IS-II), 29.94 kW (IS-II), and 225.6 kW (IS-I); (iv) R113 has the highest TGOR of 0.6924 (IS-I) compared to other organic fluids. (v) The improvements in Wnet•, mfresh•, Qcooling• and Qheating• with using toluene instead of R113 at tf1 = 40 °C are 177.5%, 105.8%, 389.25%, and 79%, respectively.

Towards an Efficient Multi-Generation System Providing Power, Cooling, Heating, and Freshwater for Residential Buildings Operated with Solar-Driven ORC

In buildings, multi-generation systems are a promising technology that can replace discrete traditional energy production methods. A multi-generation system makes it possible to efficiently produce electricity, cooling, heating, and freshwater simultaneously. This study involved the numerical analysis of a modified proposed novel solar-driven multi-generation system (MGS-II) integrated with the Organic Rankine Cycle (ORC), Humidification–Dehumidification Desalination System (HDH), and Desiccant Cooling System (DCS) by using heat recovery and thermal energy storage (TES) units. In addition, a comparison study with the basic multi-generation system (MGS-I) is performed. The proposed system is designed to supply electricity, air conditioning, domestic heating, and fresh water to small/medium-sized buildings. How operating conditions affect system productivity and performance metrics have been investigated. The results show that the proposed multi-generation system (MGS-II) can produce electrical power, space cooling, domestic heating and fresh water while maintaining comfortable conditions inside the conditioned space. Moreover, the MGS-II outperforms the MGS-I system, and the maximum MGS-II system productivity; electricity production (\({W_{net}^{\bullet}}\)), freshwater (\({m_{fresh}^{\bullet} }\)), space cooling (\({Q_{cooling}^{\bullet} }\)), and domestic heating (\({Q_{heating}^{\bullet} }\)) are 102.3 kW, 141.5 kg/h, 20.77 kW, and 225 kW, respectively. In addition, the highest total gained output ratio (TGOR), specific total gained energy (STG), and specific total gained energy equivalent price (STGP) of the MGS-II system are 0.6303, 3.824 kWh/m2, and 0.149 USD/m2, respectively. The accepted ranges of comfortable space-supplied air conditions (temperature and humidity) are 15.5–18.2 °C and 9.2–12.00 gv/kga for both systems, MGS-I and MGS-II. Finally, the current system (MGS-II) has the maximum of the system’s performance indicators and productivity (TGOR and \({{\overset{.}{m}}_{fresh} }\)) compared with the other reported systems.

Thermodynamic and Performance Assessment of an Innovative Solar-Assisted Tri-Generation System for Water Desalination, Air-Conditioning, and Power Generation

Abstract-An innovative tri-generation system powered by solar energy for water desalination, air-conditioning, and electrical power production is proposed and investigated numerically in this paper. The system is designed for small and medium-sized buildings in countries that are rich in solar energy but poor in fossil fuels and water resources. The devised system includes a solar system (evacuated tube collectors and thermal energy storage unit), an Organic Rankine Cycle (ORC), a Humidification and Dehumidification (HDH) water desalination system, and a Desiccant Cooling System (DCS). A detailed parametric study of the developed system is carried out for a wide range of operating conditions and design parameters on the system’s productivity and performance parameters. It is found that: (i) The proposed tri-generation system can deliver high electrical power, fresh water, space cooling capacity, and Energy Utilization Factor (EUF) of 104.5kW, 72.37kg/h, 25.48kW, and 0.2643 respectively. In comparison to the basic system, the EUFimp and ASC,sav parameters were enhanced having maximum values of 69.9% and 41.14% respectively. General numerical correlations derived from the numerical data can predict the system productivity and performance parameters within reasonable error.

Solar Desiccant Cooling System for a Commercial Building in Kuwait’s Climatic Condition

The use of air conditioning in buildings to provide a comfortable environment accounts for up to 75% of the electricity consumed in Kuwait for the hot season from April through to the end of October. The widespread adoption of air conditioning systems in buildings has resulted in an increased demand for electricity. This has led to an increased peak load demand that has resulted in a larger carbon footprint and placed the electricity grid under significant strain. Heat-driven air conditioning systems that use solar energy are now emerging as alternatives to electricity-driven conventional refrigerated air conditioners. These systems are more energy-efficient, with lower carbon emissions while also ensuring better indoor air quality and comfort when optimally designed. Among the heat-driven air conditioning systems, the desiccant cooling system is among the systems with the most potential. This paper presents a numerical investigation of the design optimization of solar desiccant cooling systems for Kuwait’s climate. The numerical model of the system is developed using validated components. The various design configurations analysed include a solar heating system and regeneration air for the desiccant wheel. It is found that an evacuated tube solar collector in conjunction with return air from the building to regenerate the desiccant wheel provides the best results.

Solar Desiccant Cooling System as an Alternative Solution for Net-Zero Energy Buildings (NZEBs) in the Tropical Regions

The development of energy-efficient cooling systems is a major challenge for Net-Zero Energy Buildings (NZEBs) in tropical climates. This study proposes a solar-assisted two-stage hybrid desiccant cooling system as an energy-efficient air conditioning (AC) system for use in tropical NZEBs. TRNSYS software was used to simulate the proposed model for application in a classroom with a high latent load (51%). The simulation results were analysed in terms of air properties, energy allocation, and potential energy savings. It was discovered that using two-stage dehumidification instead of one-stage dehumidification reduced regeneration temperature from 72 °C to 63 °C, which leads to considerable reduction in backup heater energy consumption. This study shows that by means of the proposed model instead of a fan coil unit, thermal comfort and energy savings of 37% can be achieved.

A Novel Polygeneration System Based on a Solar-Assisted Desiccant Cooling System for Residential Buildings: An Energy and Environmental Analysis

This work aims to design and dynamically simulate a polygeneration system that integrates a solar-assisted desiccant cooling system for residential applications as an alternative to vapor compression systems. The overall plant layout supplies electricity, space heating and cooling, domestic hot water, and freshwater for a single-family townhouse located in the city of Almería in Spain. The leading technologies used in the system are photovoltaic/thermal collectors, reverse osmosis, and desiccant air conditioning. The system model was developed and accurately simulated in the TRNSYS environment for a 1-year simulation with a 5-min time step. Design optimization was carried out to investigate the system’s best configuration. The optimal structure showed a satisfactory total annual energy efficiency in solar collectors of about 0.35 and about 0.47 for desiccant air conditioning. Coverage of electricity, space heating and cooling, domestic hot water, and freshwater was 104.1%, 87.01%, 97.98%, 96.05 %, and 100 %, respectively. Furthermore, significant ratios for primary energy saving, 98.62%, and CO2 saving, 97.17%, were achieved. The users’ thermal comfort level was satisfactory over the entire year. Finally, a comparison with an alternative coastal site was performed to extend the polygeneration system’s applicability.

Energy and Thermal Comfort Analysis of Optimised Hollow Fibre Liquid Desiccant Cooling and Dehumidification Systems in Mediterranean Regions: Modelling, Validation and Case Study

Energy and Thermal Comfort Analysis of Optimised Hollow Fibre Liquid Desiccant Cooling and Dehumidification Systems in Mediterranean Regions: Modelling, Validation and Case Study

A Mathematical Model for Predicting the Performance of the Solar Energy assisted Hybrid Air Conditioning System (SEAHACS) with One-Rotor Six-Stage Rotary Desiccant Cooling System. (Dept. M)

A mathematical model for predicting the performance of solar energy assisted hybrid air conditioning system (SEAHACS) is presented. The honeycombed silica gel desiccant wheel was used in this study, one-rotor six-stage rotary desiccant cooling system, in which two-stage dehumidification process, two –stage pre-cooling process and two-stage regeneration process are realized by only one wheel. Three air streams are involved in the present system. The mathematical model has been validated with the experimental data. As the key operating and design parameters, the range of regeneration air inlet temperature from 65-140 oC, area ratio of process air to generation air change from 1-3.57, regeneration air inlet velocity from 1.5-5.5 m/s have been examined for a range of rotation speed from 6-20 rev/h. the optimization of this parameters is conducted based on the moisture removal capacity D, relative moisture removal capacity, dehumidification coefficient of performance and thermal coefficient of performance. At last, the influences of these main parameters on optimal rotation speed are discussed

Dynamic Simulation of Desiccant Cooling System with Simultaneously Using Solar and Ground Renewable Energies in Hot-Humid Regions

This paper presents the dynamic operation of a desiccant cooling system combined with solar and ground source energies. Solar energy is used for providing the required energy for regenerating the desiccant wheel, and the ground source heat exchanger is exploited as an air pre-cooling component. The potential of the system in providing thermal comfort is assessed in hot-humid regions. Results reveal that this system is capable of providing thermal comfort in these regions with low-grade regeneration temperatures (lower than 75 ℃). As a new perspective, the maximum value of the desiccant wheel regeneration temperature is controlled. The effect of the desiccant wheel performance and its maximum regeneration temperature is evaluated on the behavior of the system. With results, high performance desiccant wheel increases the provided thermal comfort up to 40% and the contribution of solar energy up to 14% compared with its low performance. Reducing the maximum regeneration temperature to 50 ℃, decreases the achieved thermal comfort to lower than 30%. Ground source heat exchanger enhances the thermal comfort and a specified level of that can be provided with lower regeneration temperatures. The economical assessment shows that in entirely provided thermal comfort conditions by the system, the payback period is calculated to be 8.2 years.

Experimental and Statistical Analysis of Relative Humidity and Temperature of Moist Air in a Flat Plate Multi-Layer Desiccant Cooling System

ABSTRACT Sensible load and latent load are the two main factors for effective space air conditioning. In recent times, for comfort space air conditioning, several efforts have been made to drop the Relative Humidity (RH) and Temperature of the ambient moist air to meet the comfort conditions. In the present work, dehumidification of ambient processed air has been performed using a novel flat plate multi-layer liquid desiccant cooling system to achieve a comfortable environment for human beings. The experimental investigation has been performed to analyze the effects of operating parameters including processed air velocity, desiccant solution flow rates, and its concentration, relative humidity (RH) and temperature (T) of the ambient processed air. Response surface methodology has been implemented to execute the statistical modeling of the RH and T of the processed air during the dehumidification process. Analysis of variance (ANOVA) has been implemented at a confidence interval of 95% of process parameters (processed air velocity, desiccant solution flow rates, and solution concentration) on the responses (RH and T) of the processed air. Finally, few experiments were also performed to validate the developed model. It has been perceived that the value of output parameters decrease with decrease in processed air velocity and increase in solution concentration while these parameters increase with increase in solution flow rates. The results revealed that the relative humidity and temperature of the processed air reduced up to 12.8% (8.73 g/kg as humidity ratio) and 4.1◦C, respectively, in comparison to the inlet air conditions.