Performance Of Desiccant Wheel Research Articles

Simulation Study on Performance of Solar-Powered Desiccant Wheel and Ground Source Heat Pump Air Conditioning in Qingdao

In China, a large amount of the total energy consumption is made up of building energy, particularly in humid regions. The conventional vapor compression refrigeration systems cannot effectively control the indoor humid and thermal environment. Therefore, this article proposes a solar-powered desiccant wheel and ground-source heat pump (SDW-GSHP) air conditioning system. The energy consumption of the system is mainly from sustainable sources of solar and geothermal energy, showcasing excellent energy efficiency and environmental friendliness. The desiccant wheel (DW) processes latent heat loads, and the GSHP processes the sensible heat load. The regeneration air of the DW is heated by a solar collector. The operational performance of the system was simulated by using TRNSYS during the typical summer week (15 July to 22 July) in Qingdao. The simulation results indicated that indoor temperature was maintained within 25.8–26.2 °C and the relative humidity was maintained in the range of 57–61%. The COP of the SDW-GSHP air conditioning system was 42.1% higher than that of the DW air conditioning system with electric heating regeneration, and electricity saved 43.7%.

Development of rotary dehumidifier with silica-gel-based composite desiccant

The desiccant dehumidification system's key component, the desiccant wheel, can perform effectively using composite desiccant materials. Evaluation of the desiccant wheel's performance using composite desiccant material is the primary goal of this study. Authors have compared the performance of two desiccant wheels; one is packed with traditional Silica-gel, and the other is a composite of Silica-gel and calcium chloride in a ratio of 3:2 by weight. A rotary wheel is developed with rectangular channels parallel to the wheel's axis. The novelty of this research lies in the improved design of the desiccant wheel. Unlike other techniques involving pressure losses and ineffective space utilization, this design offers better space utilization and fewer pressure losses. In addition, wheel fabrication is less costly and easily reusable with other desiccants. Three performance indicators were evaluated through experimentation: dehumidification capability, moisture removal capacity, and dehumidification coefficient of performance. Results show that the Parallel channel desiccant wheel achieves 25% higher dehumidification capability and 55% greater moisture removal capacity. The specific humidity of the air is reduced by 35% using the composite desiccant wheel. Comparing the composite desiccant to traditional Silica-gel, its dehumidification coefficient of performance is 40% higher.

Optimized geometric designs of desiccant wheels with metal-organic frameworks considering dehumidification capacity and energy

With the increasing demand for handling dehumidification loads and energy savings in air-conditioning systems, solid-desiccant dehumidification systems have been implemented in passive and zero-energy buildings. Although novel metal-organic frameworks (MOFs) have been introduced to improve the performance of desiccant wheels, previous studies have mainly focused on silica gel-based desiccant rotors (DRs). This study aimed to optimize the geometric design of MOF DRs to achieve enhanced dehumidification and energy performance. A numerical model for estimating the performance characteristics of MOF DRs was developed using the adsorption isotherm curves measured in this study. The numerical model was validated by comparing the predictions with the experimental data. The dehumidification and energy performance of the MOF DRs were analyzed in terms of the coating amount, channel pitch, rotor thickness, and process-regeneration area ratio. Accordingly, the optimized geometric designs of the MOF DRs were determined to achieve the maximum dehumidification capacity and minimum energy consumption. Compared to the baseline MOF DR, the capacity-optimized MOF DR exhibited a 47.4 % higher moisture removal capacity, whereas the energy-optimized MOF DR exhibited a 48.6 % lower sensible energy ratio.

Experimental investigation of desiccant dehumidification with four different combinations of silica gel desiccant wheel on indoor air quality

Indoor air quality (IAQ) describes the air quality within buildings and other structures, particularly concerning how it affects the health and comfort of building inhabitants. Your likelihood of experiencing indoor health issues can be decreased by being aware of and controlling common indoor contaminants. In addition to maintaining indoor relative humidity at or below 65%, The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends temperatures between 21 and 26 °C in the summer and 20–24 °C in the winter. The EPA advises using humidity levels between 30 and 60% to stop mold from growing. Silica gel, lithium chloride, and molecular sieves 5A are excellent for dehumidification due to their strong moisture adsorption capability and potential for regeneration. Choosing the right desiccant depends on factors like adsorption capacity, pore size, and chemical compatibility, which are crucial for dehumidification applications and environments. This study compares the performance of silica gel desiccant wheels with three additional composite materials for air dehumidification, which is unusual in this work because very few studies of these combinations have been provided. For all desiccant wheels, the various operating parameters of the needed dehumidification process have been investigated and compared. For adsorption and regeneration rate, the performance of three different composite desiccant wheels was examined and compared experimentally. This experimental evaluation reveals that the composite desiccant wheel (silica gel-lithium chloride-molecular sieve 5A) has a higher adsorption and regeneration rate than others. When a composite desiccant wheel made from silica gel-lithium chloride, silica gel-molecular sieve 5A, and silica gel-lithium chloride-molecular sieve 5A was compared to the performance of a silica gel desiccant wheel, the percentage improvements in adsorption rate were 34.99%, 43.58%, and 85.5%, and the percentage increases in regeneration rate were 5.65%, 7.08%, and 14%.

Effect of operating parameters on the performance of rotary desiccant wheel energized by PV/T collectors

The main energy input of a desiccant air conditioning system is the low-quality thermal ener-gy required for regeneration, which can be obtained from waste heat, geothermal resources or solar energy. Regeneration thermal energy can be produced as well as energizing components such as fans, pumps, auxiliary air heaters, and control elements of the system by using pho-tovoltaic-thermal solar collectors (PV/T). In this study, parametric analyzes were performed to investigate the effect of regeneration temperature and air frontal velocity on the tempera-ture and dehumidification performance of a solid silica-gel desiccant wheel and on the wa-ter-cooled PV/T collectors used to provide the regeneration thermal energy. The regeneration temperature was varied between 50 and 70°C, and air frontal velocity between 1.3 and 4.1 m/s. The analyzes show that the dehumidification efficiency increases from 13.94% to 33.04% as regeneration temperature increased from 50°C to 70°C at 1.3 m/s air frontal velocity at which dehumidification efficiency is maximum. At 4.1 m/s air frontal velocity, the required regener-ation thermal energy is maximum and increases from 49.64 kW to 132.48 kW at the same re-generation temperature change. The low regeneration temperature resulted in desirable latent performance and undesirable sensible heat transfer performance in DEW. Finally, considering the whole system, it was concluded that the optimum regeneration air temperature for the performance parameters is 60°C.

Comparative performance evaluation of multi-objective optimized desiccant wheels coated with MIL-100 (Fe) and silica gel composite

Metal-organic frameworks have been introduced as promising alternative materials to improve the performance of conventional desiccant wheels (DWs) in desiccant cooling systems. However, simultaneously achieving high dehumidification and energy performance of DWs coated with advanced desiccant materials is challenging owing to the trade-off between these indices. In this study, based on multi-objective optimization, the dehumidification and energy performance improvement of a DW coated with MIL-100 (Fe) (MCDW) over a conventional DW coated with silica gel (SGDW) and silica composite (SCDW) were evaluated. Based on the data measured in this study, a metamodel was developed using an artificial neural network to predict the performance of the MCDW. Furthermore, Morris sensitivity analysis was conducted to determine the decision variables. The optimal solutions were determined using multi-objective optimization and a Euclidean distance-based approach. Finally, a comparative performance evaluation between the optimized MCDW and SCDW was conducted under baseline conditions. As a result, the optimized MCDW showed higher dehumidification and energy performance than the optimized SCDW and SGDW.

Multi-objective optimization of desiccant wheel via analytical model and genetic algorithm

The dehumidification performance and energy consumption of desiccant wheel are affected by many design parameters and operating variables. However, there are few researches concerning multi-objective optimization. Therefore, an optimal design framework combining analytical model, multi-objective optimization and decision-making is proposed. The model was based on the overall heat and mass balances, so the objective functions of the desiccant wheel were derived, and the constraints for the equilibrium of the adsorption and desorption were obtained. Then, the non-dominated sorting genetic algorithm II (NSGA-II) was employed to calculate the Pareto optimal front of the two-objective optimization, and the results were analyzed with psychrometric chart. This solution set includes not only the optimum one with the design method of psychrometric charts, but also includes other better solutions. From the Pareto solutions, the final optimal solution was obtained with the technique for order preference by similarity to ideal solution (TOPSIS) based on four criteria. With the final optimal parameters applied to existing example, the further improvements on the outlet process air humidity ratio and the dehumidification coefficient of performance were found.

Performance enhancement of desiccant wheels by adsorption/desorption in stages with type-S isotherm desiccants

Desiccant wheels coated with desiccants possessing a single kind of adsorption isotherm face the drawback that the moisture transfer driving force decreases along the direction of air flow in the channel, which hinders the efficiency of regeneration and dehumidification processes. In this study, a new concept of adsorption/desorption in stages with type-S isotherm desiccants was proposed to improve the performance of a counter flow type desiccant wheel by increasing the moisture transfer driving force during both dehumidification and regeneration processes. The numerical results show that compared with conventional wheel made up of silica gel, the two desiccant wheels with various hypothetical type-S isotherm desiccants designed in this study output air with more stable humidity during dehumidification, and have superior performance when both cycling time (tcyc) is high and regeneration temperature (Tr,i) exceeds the critical value.

Performance evaluation of various fiber paper matrix desiccant wheels coated with nano-adsorbent for energy efficient dehumidification

This paper investigates the dehumidification performance of desiccant wheel (DW) with different fiber paper (FP) substrates such as wood pulp, glass fiber, ceramic fiber, Nomex fiber, and brown wood pulp FP, coated with nano SiO2 as adsorbent for energy efficient air dehumidification. The FP substrates are coated with SiO2 nano-adsorbent by impregnation-dip coating method to the thickness of 5 mils. The adsorption capacity for all the FP substrates was evaluated at temperature of 28 °C and 70% relative humidity. It was found that the adsorption capacity increases with increasing the desiccant coatings. The adsorption capacity of GFP was high with a value of 57.6 g·m-2 and thermal conductivity was improved from 0.038 W·m-1·K-1 to 0.094 W·m-1·K-1 with desorption temperature of 45 °C after coating with SiO2 nano-adsorbent. Among varying regeneration temperature from 50‒90 °C, the desiccant wheel GFP-SiO2-DW has high dehumidification capacity and dehumidification coefficient of performance (DCOP) of 2.1 g·kg-1 and 2.2 respectively at 50 °C. The results confirm that less energy is necessary for the regeneration heater which can be supplied from a low-grade energy source thus reducing the energy consumption for regeneration of the desiccant wheel.

Effectiveness approach for predicting desiccant wheel performance: correlation utilizing experimental results

In order to utilize green energy and reduce the environmental effect of traditional systems, the majority of HVAC experts are now focusing on the development of sustainable and green energy-supported air conditioning technologies. The air conditioning technologies integrated with a desiccant wheel can save energy and reduce the environmental influence. The desiccant wheel is essential for every rotary desiccant integrated air conditioning system. A practical cooling system with a desiccant wheel requires much effort to analyze. But the performance of a desiccant wheel can be predicted effectively using suitable performance parameters, which is the focus of this study. The desiccant wheel's performance has been evaluated using a new set of independent efficacy metrics. Several types of research have been conducted to determine the effects of operational factors on the performance parameters. Correlations have been developed based on experimental data for forecasting desiccant wheel performance. There is a high degree of agreement between experimental and anticipated results when using the correlations suggested.

Experimental Investigation on Heat Transfer Performance of Rotatory Desiccant Dehumidifier

Dry air plays an essential role in achieving human comfort and in other applications like product drying, food storage, etc. one of the best methods to produce dry air is by employing a desiccant dehumidifier. A rotatory desiccant wheel with silica gel is used in the present work. Current work involves the optimization of the desiccant wheel performance in terms of airflow rates along with ambient temperatures. Optimization of desiccant wheel is suggested by maximum value of various performance parameters involved in this study. Required conditions have been set up by the pre-treatment section installed before the desiccant wheel. At the regeneration section two electric heater (250 watt each) is fitted through which the desiccant material is regenerated. This work is conducted for humid and hot conditions and found that the optimum functioning of desiccant wheel dehumidifier is found at 31°C ambient temperature and at the inlet 3.5 m/s velocity of air.

Integration of desiccant wheels and high-temperature heat pumps with milk spray dryers

Heat pump technologies are promising to decarbonise industrial drying processes by improving energy efficiency and shifting the energy source from fossil fuels to renewable-sourced electricity. While desiccant materials have proved effective in improving drying efficiency for dryers at temperatures < 120 °C, this paper focuses on the performance of desiccant wheel assisted high temperature heat pump (HTHP) technology to heat the dryer inlet air up to 150 °C using heat recovered from the dryer exhaust. Thermodynamic models of heat pump cycles were established to evaluate the performance of all the HTHP components. A one-dimensional finite difference model was used to simulate the dehumidification of exhaust air through the evaporator of the HTHP. The performance of the desiccant wheel was numerically simulated considering only the gas-side heat and mass transfer resistance. When compared with configurations of a simple HTHP, the desiccant wheel assisted HTHP requires a much smaller evaporator size (50–60 % less than the simple HTHP), similar to the HTHP with a heat recuperator. Its improvement in overall system coefficient of performance (COP), exergy efficiency and the drying capacity when applied to a spray dryer is marginal when compared to the model accuracy. However, comparisons between two cases with different ambient conditions (15 °C and 60 % RH vs 25 °C and 80 % RH) show that such improvement by the desiccant wheel assisted HTHP develops with increasing humidity in the incoming drying air.

Effect of operating parameters on the performance of rotary desiccant wheel energized by PV/T collectors

The main energy input of a desiccant air conditioning system is the low-quality thermal ener-gy required for regeneration, which can be obtained from waste heat, geothermal resources or solar energy. Regeneration thermal energy can be produced as well as energizing components such as fans, pumps, auxiliary air heaters, and control elements of the system by using pho-tovoltaic-thermal solar collectors (PV/T). In this study, parametric analyzes were performed to investigate the effect of regeneration temperature and air frontal velocity on the tempera-ture and dehumidification performance of a solid silica-gel desiccant wheel and on the wa-ter-cooled PV/T collectors used to provide the regeneration thermal energy. The regeneration temperature was varied between 50 and 70°C, and air frontal velocity between 1.3 and 4.1 m/s. The analyzes show that the dehumidification efficiency increases from 13.94% to 33.04% as regeneration temperature increased from 50°C to 70°C at 1.3 m/s air frontal velocity at which dehumidification efficiency is maximum. At 4.1 m/s air frontal velocity, the required regener-ation thermal energy is maximum and increases from 49.64 kW to 132.48 kW at the same re-generation temperature change. The low regeneration temperature resulted in desirable latent performance and undesirable sensible heat transfer performance in DEW. Finally, considering the whole system, it was concluded that the optimum regeneration air temperature for the performance parameters is 60°C.

Heat pump combined with single-stage or two-stage desiccant wheel system? A comparative study on different humidity requirement buildings

Heat pump desiccant wheel hybrid systems can control indoor temperature and humidity for industrial and civil buildings. To clarify the boundary of heat pump combined single-stage desiccant wheel system and two-stage desiccant wheel system for judging the optimal system under different conditions, the performance of the two systems is analyzed with experiment and simulation method. Firstly, the fresh air process is compared for different humidity set points under typical operation conditions. Secondly, the energy moisture ratio (EMR) of desiccant wheels is analyzed. At last, based on system energy consumption and economy, the humidity boundary of the single-stage and the two-stage dehumidification system is proposed, under different conditions. It is found that the energy performance of desiccant wheel increases with the reducing of humidity set point for both systems, and higher EMR can be obtained by the desiccant wheel of the single-stage dehumidification system for all operation modes. The two-stage dehumidification system is more energy efficient when humidity for the controlled space is lower than 49%, 55% and 40% for high temperature mode, typical summer mode and typical dehumidification mode, separately. With the proposed operation boundary, the optimal system can be quickly judged according to the humidity control requirement and outdoor environment.

Performance assessment of a desiccant air-conditioning system combined with dew-point indirect evaporative cooler and PV/T

In this study, a new solid desiccant air-conditioning system configuration integrated with direct and dew-point indirect evaporative coolers and water-cooled photovoltaic-thermal solar collectors (PV/T) is proposed and simulated for a building located in Adana, a humid and hot city on Mediterranean coast of Turkey. New multiple linear regression equations are developed for the performance of desiccant wheel and dew-point indirect evaporative cooler, which are the two crucial components of the air-conditioning system and used in hourly simulations. Building set temperature, exhaust air mixing ratio, suitable warm air source for preheating regeneration air and optimum connection strategy of PV/T collectors to each other are examined in detail. Hourly and daily thermal coefficient of performance (COPth), solar fraction, primary energy consumption and specific primary energy consumption are calculated to evaluate the energetic performance of the system. COPth of the system ranges from 0.28 to 0.40 during the day, with a daily COPth of 0.34. 69% of the thermal energy required to regenerate desiccant wheel can be generated by the PV/T water collectors.

Experimental Investigation on the performance of Silica Gel Desiccant Wheel. (Dept.M)

Experimental Investigation on the performance of Silica Gel Desiccant Wheel. (Dept.M)

Experimental evaluation of the dehumidification performance of a metal organic framework desiccant wheel

As the bearer of wet load, the desiccant wheel determines the performance of the rotary wheel dehumidification system. In this study, a novel metal organic framework composite adsorbent desiccant wheel (MOF DW) was prepared by impregnating–spraying method. The complete rotary wheel dehumidification system was built to compare the dehumidification performance of MOF DW and commercially silica gel desiccant wheel (SG DW). The experimental results showed that increasing the rotation speed appropriately improves the utilization ratio of regenerative energy and dehumidification capacity of MOF DW at high ambient humidity ratio. The temperature rise at the inlet and outlet of MOF DW is lower than that of SG DW at low ambient humidity ratios, and the opposite is true at high ambient humidity ratios. In addition, the dehumidification capacity and coefficient of performance of the MOF DW increase by 40%–48% and 13%–19%, respectively, compared with those of the SG DW at the regeneration temperature of 50°C.

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.

A Mathematical Model of Desiccant Wheel in Desiccant Cooling

The desiccant wheel performance of desiccant cooling system components is very important whose function is to regulate air humidity levels as well as to the capability, size and cost of the entire system. Mathematical models for predicting the performance of desiccant wheels in the development of mathematical models is one of the effective methods for analyzing the performance of wheel this moisture-reducing. This mathematical model can also be used in guiding system operation, delivering experimental results and automation in designing this cooling system. The purpose of this paper is to provide an overview of efforts to mathematically model the process of heat transfer and mass transfer that occurs in the moisture-reducing wheel. The desiccant wheel model built here is a gas and solid system including basic principles, heat and mass transfer mechanism and model building. The model is based on ideal assumptions, equations, additional conditions and the method of solution and also the main results. The gas-solid model is a more precise and more complex model than the other models. From these results the evolutionary process of the mathematical model is obtained and the aspects of calculation of pressure loss, air leakage, and optimal rotation speed of the drying wheel / dehumification.

Theoretical Performance of Silica Gel Desiccant Wheel

Abstract— Silica gel is a substance commonly used in desiccant wheel, which in turn is used in many applications to reduce moisture from the supplied air to a specific space. In this research, the effect of different operational conditions on the performance of silica gel wheel were studied. The desiccant wheel, which has been used, has a diameter of 55 cm and thickness of 20 cm. It contains 34 kg of silica gel and rotate at a speed of 30 rph. The theoretical performance coefficients of the desiccant wheel which have been studied include ,moisture removal capacity(MRC),dehumidification performance(DCOP),latent coefficient of performance (COPlat), and desiccant wheel effectiveness(ϵ_d). The theoretical investigation of these coefficients was done by using Novel Aire Technology software program (Simulation program of desiccant wheel) (2012). While the operational conditions like process air (humid air)inlet temperature between(30 to 43.4)0C, process air inlet humidity ratio between (0.011 to 0.019)kg/kgdry air ,regeneration air inlet temperature between (56.5 to 70)0C,and process air mass flow rate between(0.0814 to 0.199)kg/s. The results shows that the effectiveness and the moisture removal capacity have the same behavior increase with the increasing in mass flow rate from(0.0814 to 0.199) kg/s, humidity ratio from(11 to19)g/kgdry air, and regeneration air temperature from(56 t0 70)oC. But they reduces with increasing of inlet process air temperature from(30 to43.4)oC..