Performance Investigation and Optimization of Composite Materials in Household Dehumidifiers

Abstract

The efficiency of household dehumidifiers is affected by air temperature and the temperature used for regeneration. A regeneration temperature that is too high can lead to increased energy use, heat build-up in the desiccant wheel, and lower dehumidification efficiency. In this study, we developed a LiCl@Al-Fum composite material and evaluated it through physical characterization and module testing. The results show that the LiCl@Al-Fum composite with a 20% mass fraction is particularly effective as a desiccant material. Additionally, a 15% volume concentration of neutral silica sol was identified as the optimal binder concentration. A comparative analysis of the effects of glass-fiber desiccant wheels (GF DWs), aluminum desiccant wheels (Al DWs), and commercial desiccant wheels (CM DWs) on household dehumidifier performance revealed that the Al DWs outperformed the CM DWs, showing a 13% improvement in the dehumidification rate and a 12.56% increase in the DCPP. An increase in the dehumidifier structure led to increases in the dehumidification rate by 11.8%, 11.9%, and 10% and in the DCPP by 11.6%, 12.1%, and 10%, respectively. Moreover, the modifications resulted in a 3.85 °C, 3.34 °C, and 3.8 °C decrease in the temperature.

1. Introduction

Prolonged exposure to high humidity can hinder the body’s ability to dissipate heat and promote the growth of harmful bacteria, thereby affecting one’s health [1]. On the other hand, low humidity can also increase the risk of respiratory and headache-related illnesses.

Air dehumidification can be achieved through two primary methods: condensing dehumidification and desiccant dehumidification. Condensing dehumidification methods include compressing dehumidification [2], thermoelectric dehumidification [3,4], and heat pump dehumidification [5,6], among others. Desiccant dehumidification methods include liquid desiccant dehumidification [7,8] and solid desiccant dehumidification [9,10]. Condensing dehumidification can only handle air with a dew point temperature above 0 °C due to freezing phenomena [11]. Liquid desiccant dehumidification is generally corrosive and consumes substantial energy for regeneration. Rotary dehumidification systems (RDSs) based on solid desiccants have gained increasing attention and recognition due to their simplistic structure, low energy consumption, and potent dehumidification capability, as stated in various studies [12,13,14].

Research on the RDS primarily revolves around two aspects: advanced desiccant material and system structure optimization [15]. The performance of the desiccant material directly determines the effectiveness of the dehumidification system. An ideal desiccant material possesses three key characteristics: good cycling stability and thermal stability, outstanding water vapor adsorption performance, and a low regeneration temperature. Its excellent water vapor adsorption performance is a crucial indicator of its potential applications.

Currently, household dehumidifiers typically use traditional desiccants such as silica gel [16], zeolite [17] and calcium chloride. Ge et al. [18] investigated the dehumidification performance of a silica gel desiccant and found that it can only meet the dehumidification requirements when the regeneration temperature is above 100 °C at 37 °C and 65% RH. Fong et al. [19] studied the effect of adsorbent characteristics on the performance of rotary dehumidifiers through computer simulations. Their results indicate that rotary dehumidifier performance depends not only on factors such as the moisture uptake rate and adsorbent density but also on the regeneration temperature, airflow velocity, and rotational speed of the rotary wheel.

Traditional desiccants such as silica gel and zeolite have low moisture absorption rates at low regeneration temperatures and low relative humidity. As a result, rotary dehumidification systems tend to have inferior performance compared to cooling systems. To overcome this challenge, there is a need for moisture-absorbing materials with superior performance. Metal-organic frameworks (MOFs) have gained popularity due to their high dehumidification performance and low regeneration temperature [20]. Park et al. [21] investigated a rotary dehumidification system using MOF materials as desiccants and observed a 139% improvement in the dehumidification capacity compared to that of traditional desiccants. Elsayed et al. [22] compared the isotherms, adsorption kinetics, and adsorption cycle stability of two MOF materials, CPO-27(Ni) and Al-Fum. The findings indicate that Al-Fum performs better at high evaporation temperatures (20 °C) and low regeneration temperatures (70 °C).

Porous materials rely solely on their physical adsorption capacity, which has limitations [23]. On the other hand, hygroscopic salts and similar substances utilize chemical adsorption, providing higher adsorption capacities. However, they are vulnerable to dissolution and corrosion issues after hydrate formation. To address these limitations, incorporating hygroscopic salts into the main adsorbent to form composite materials is an effective strategy. Elsayed et al. [24] synthesized a composite material of MIL-101(Cr)/CaCl₂ and conducted a series of experimental studies. The results revealed that the hygroscopic performance of the composite material was 11 times greater than that of the pure MIL-101(Cr) material.

Research is currently focused on the design of desiccant wheel structures and system parameters in the field of RDSs. Su et al. [25] proposed an improved dehumidification system that integrates precooling and a recirculated regenerative rotary dehumidification system. This resulted in a 29.7% improvement in the dehumidification capacity compared to that of conventional chilled water-cooling systems. Guan et al. [26] designed a desiccant wheel and liquid desiccant cascade dehumidification system that achieves a supply air dew point temperature of −10 °C. Liu et al. [27] developed a combined desiccant wheel and heat pump drying system, which increased the dehumidification capacity of the system by 166% by utilizing a heat pump evaporator to lower the inlet temperature of the processing zone. Narayanan et al. [28] developed a numerical model for a counterflow desiccant wheel and analyzed the impact of different channel shapes on system performance. The results showed that desiccant wheels with sinusoidal, rectangular, and triangular channels outperformed those with circular, hexagonal, and square channels in terms of dehumidification effectiveness.

The temperature of the treated air is increased by the heat generated by the air passing through the desiccant wheel, which reduces the dehumidification efficiency. While a high regeneration temperature is beneficial for desiccant desorption in the regeneration zone, it can result in heat accumulation in the desiccant wheel, further increasing the temperature of the treated air at the inlet and reducing the dehumidification efficiency. Additionally, a high regeneration temperature leads to increased energy consumption, which reduces the economic viability of household dehumidifiers. Therefore, the main objective of this study is to develop a desiccant suitable for household dehumidifiers, optimize the structure of household dehumidifiers, thereby improving dehumidification efficiency and reducing dehumidification energy consumption.

2. Materials and Methods

2.1. Materials

Aluminum sulfate (Al₂(SO₄)₃·18H₂O) was purchased from Titan Scientific in Shanghai (China). Fumaric acid (C₄H₄O₄) was acquired from InnoChem Science and Technology in Beijing (China). Sodium hydroxide (NaOH) was obtained from Yili Fine Chemicals in Beijing (China). Lithium chloride (LiCl) was supplied by Zesheng Technology in Beijing (China). Acidic silica sol and neutral silica sol were obtained from Fuer Chemical Technology in Guangzhou (China). All chemicals were used as received without further purification.

2.2. Preparation of the Composite Material

Pure MOF aluminum fumarate was prepared according to reference [29]. LiCl@Al-Fum was prepared through the ion-liquid infiltration method. Figure 1 shows the schematic diagram of LiCl@Al-Fum. The concentration of lithium chloride in the composite material was controlled by adjusting the amount of lithium chloride added, while the amount of Al-Fum remained constant. Composite materials with various ratios were prepared using the aforementioned steps: 10-LiCl@Al-Fum, 15-LiCl@Al-Fum, 20-LiCl@Al-Fum, and 25-LiCl@Al-Fum, Figure 2 shows composite materials with different ratios.

2.3. Study of Composite Material Characteristics

Determining the optimal ratio of the composite material is essential. Figure 3 illustrates the adsorption capacity of the pure Al-Fum material and its composite materials at 60% and 80% relative humidity at 25 °C. The greater the proportion of LiCl in the composite material is, the greater the adsorption performance. The composite material undergoes both physical and chemical adsorption simultaneously. After 30 min, the 25-LiCl@Al-Fum composite material exhibited hydrolysis, whereas the 20-LiCl@Al-Fum composite material did not display hydrolysis even after 60 min. Consequently, the 20-LiCl@Al-Fum composite material was selected as the appropriate material for the desiccant wheel.

To study the characteristics of composite drying materials, a series of experiments were conducted [30].

(1) SEM test

FE-STEM SU9000 scanning electron microscope characterized the surface morphology of composite materials.

(2) FTIR test

The molecular structure of composite materials was analyzed using a Thermo Scientific Nicolet iS20 Fourier transform infrared spectrometer with a spectral collection range of 400 cm⁻¹–4000 cm⁻¹.

(3) XRD test

The Smartlab 3 powder diffractometer was used to analyze the composition of materials. The testing conditions were as follows: we used Cu-K α under the condition of a current of 20 ma and a tube pressure of 36 kV. The material was scanned with a diffraction angle of 2θ, the scanning range was 3–30°, and the scanning speed was 10°/min.

(4) Thermal gravimetric test

Thermogravimetric Analyzers model STA-8000 was used to study the thermal stability of materials. The testing conditions were as follows: under nitrogen gas flow, the testing temperature range was 30 °C–600 °C, and the heating rate was 10 °C/min.

(5) Aperture test

The fully automatic gas analyzer with the model Autosorb iQ was used to analyze the pore structure of materials. Place the sample in an environmental condition of 120 °C for desorption for 10 h, and then in an environment with liquid nitrogen temperature (−196 °C) to obtain the adsorption desorption curve of the sample by adsorbing N².

(6) Water vapor adsorption test

The multi station weight method gas vapor adsorption instrument with model BSD-DVS is used to measure the adsorption isotherms and kinetics of materials. The adsorption temperature is 25 °C, the relative pressure is set to 0.1–0.9, and a partial pressure point is set every 0.1 for the relative pressure.

The XRD pattern of the prepared Al-Fum is consistent with reference [31], with the characteristic diffraction peak appears at 2θ = 10.63°, 21.24°. Figure 4a demonstrates the successful synthesis of Al-Fum. Compared to pure Al-Fum, the diffraction peak position of the composite material unchanged, indicating that the composite process did not alter the structure of Al-Fum. Compared with pure Al-Fum, the diffraction peak intensity of composite adsorbent materials is reduced, indicating that the composite process will affect the coordination between metal ions and organic ligands in MOFs, leading to a decrease in their crystallinity. The SEM image in Figure 4b shows that the composite material exhibits continuous growth of spherical particle aggregates due to uneven crystal growth. Figure 4c shows that Al-Fum and 20-LiCl@ Al-Fum the characteristic vibration peaks in the spectrum are the same, with the absorption peaks at 1614 cm⁻¹ and 1422 cm⁻¹ attributed to the stretching vibration of carboxyl groups (-COO), respectively. The peak at 3428 cm⁻¹ was assignable to the O–H stretching frequency of adsorbed H₂O.

Figure 5 depicts the thermogravimetric analysis of Al-Fum and the composite material. Prior to thermogravimetric testing, the materials were pre-dried, and it was observed that pure Al-Fum had an exceptionally low water content. At 400 °C, the weight of Al-Fum rapidly decreased, indicating the decomposition of the Al-Fum MOF material framework. Due to its favorable hygroscopic nature, the composite material absorbed some water from the air before the test. As a result, the composite adsorbent material effectively removed the bound water of the hygroscopic salt within the temperature range of 30–100 °C. The framework of the composite material decomposed at approximately 330 °C. The thermogravimetric curve indicates that the composite material has good thermal stability and will not decompose when used in household dehumidifiers.

Figure 6 shows the N₂ adsorption and desorption curves of Al-Fum and the composite material. Both curves demonstrated a Type I isotherm. At a small relative pressure (P/P0 < 0.1), N₂ was swiftly adsorbed, and the adsorption capacity increased rapidly. As the relative pressure increased (P/P₀ > 0.1), the adsorption capacity gradually increased, eventually reaching saturation. The N₂ saturated adsorption capacity of pure Al-Fum was 375.46 cm³/g, which was significantly greater than that of the composite material at 143.20 cm³/g. The pore structure parameters, calculated using the BET equation and the Langmuir equation, are presented in

Table 1. Pore structure parameters of Al-Fum and the composite material.

	SBET	Smicro	Smicro	Vtotal	Dave
	(m2/g)	(m2/g)	/SBET	(cm3/g)	(nm)
Al-Fum	1029	993.6	96.56%	0.58	2.257
composite	311.9	281.6	90.29%	0.22	2.848

. The internal structure of pure Al-Fum predominantly comprised micropores. In contrast, the proportion of micropores in the composite adsorbent material was lower than that in pure Al-Fum. The total specific surface area and total pore volume of the pores in the composite material also decreased, indicating partial blockage of the pores during the composite process.

Figure 7 shows the water vapor adsorption isotherms of Al-Fum and the composite material. The water vapor adsorption capacity of the composite material is greater than that of the pure Al-Fum material at all relative pressures. Moreover, at higher relative pressures (P/P0 > 0.6), the adsorption amount of the composite material is significantly greater than that of the pure Al-Fum material. Considering that the desiccant wheel operates under high humidity conditions, the composite material serves as the ideal adsorbent material for the desiccant wheel.

3. Module Dehumidification Performance Analysis

This study was conducted to evaluate the dehumidification performance of a composite material using glass fiber (GF) and Al modules. Silica sol was chosen as the adhesive for loading, and the effect of pH on the loading of the adsorbent agent was investigated by comparing acidic silica sol and neutral silica sol.

3.1. Performance of the Glass Fiber Module

3.1.1. Effect of Silica Sol Concentration on the Dehumidification Performance

Table 2. Load weight of glass fiber modules at different neutral silica sols concentrations.

	10-CM/GF (g)	15-CM/GF (g)	20-CM/GF (g)
Before load	10.45	10.37	10.14
After load	16.2	17.98	18.16
Capacity	5.75	7.61	8.02

shows that the loadings of 20-CM/GF and 15-CM/GF are similar and are 32.3% greater than that of 10-CM/GF. Figure 8 illustrates the dehumidification capacity of the composite material at different concentrations of neutral silica sol at 25 ℃ and 80% RH. After 1 h of adsorption, the dehumidification capacities of 10-CM/GF and 15-CM/GF reached 0.996 g/g and 1.068 g/g, respectively, both of which are greater than 0.925 g/g. A high concentration of silica sol can obstruct the pores of the MOF material, thereby impacting the dehumidification performance. Hence, the optimal volume concentration of silica sol was determined to be 15%.

3.1.2. Effect of the pH of the Silica Sol on the Dehumidification Performance

Figure 9 shows the dehumidification capacity of glass-fiber modules under different pH values of silica sol at 25 °C and 80% RH. After 1 h of adsorption, the dehumidification capacity of CM/GF was 23.4% greater than that of CM-ac/GF. Furthermore, acidic silica sol can increase the acidity and negatively impact the indoor air quality. In conclusion, neutral silica sol was identified as the optimal choice for adhesives in glass-fiber modules.

3.2. Performance of the Aluminum Module

Table 3. Load weights of aluminum modules at different neutral silica sol concentrations.

	10-CM/Al (g)	15-CM/Al (g)	20-CM/Al (g)	25-CM/Al (g)
Before load	11.64	12.09	12.25	11.85
After load	17.17	18.8	19.53	19.69
capacity	5.53	6.71	7.28	7.84

indicates that as the concentration of silica sol increases, the module loading also increases. Figure 10 shows the dehumidification capacity of aluminum modules with different concentrations of neutral silica sol at dry bulb temperature (DB) = 25 °C and RH = 80%. The dehumidification capacities of 10-CM/Al and 15-CM/Al were similar and 23.6% greater than that of 20-CM/Al. Consequently, 15% neutral silica sol was chosen for subsequent experiments.

3.3. Influence of Regeneration Temperature on Module Performance

Figure 11 shows the regeneration rates of the composite materials at various regeneration temperatures. At a regeneration temperature of 70 °C, 73.2% of the Al module regenerated after 30 min. The Al module can achieve complete regeneration within 20 min at a temperature of 90 °C. Notably, the Al module demonstrated significantly greater regenerative performance than the GF module. Furthermore, the desorption process requires substantial heat consumption. The superior thermal conductivity of aluminum translated to reduced heat loss during the desorption process, effectively minimizing energy consumption for dehumidification. Consequently, aluminum is more suitable as the base material for desiccant wheels.

4. Performance Study of Composite Materials in Household Dehumidifiers

4.1. Structure Description

Figure 12 presents the structure of a household dehumidifier. The treated air was first filtered and subsequently directed into the desiccant wheel’s dehumidification zone via a process fan. Moisture was adsorbed by the desiccant, whereas the dried air is reintroduced into the room. Regeneration air was routed to the heater through a regeneration fan for heating purposes. The heated air then eliminated moisture from the desiccant wheel, which subsequently underwent heat exchange with the treated air in a heat exchanger. Ultimately, the air condensed, and the liquid water resulting from condensation flowed into a water tank via a water outlet. The air then underwent circulation by being sent back into the heater via the regeneration fan.

4.2. Performance of Household Dehumidifiers

Many factors influence the performance of household dehumidifiers, such as the treated air temperature and humidity and regeneration temperature. In this study, a single-variable method was utilized to compare and analyze the dehumidification performances of glass-fiber desiccant wheels (GF DWs), aluminum desiccant wheels (Al DWs) and commercial desiccant wheels (CM DWs). The treated air temperature, humidity status, and regeneration temperature were used as independent variables in the experiment, while the dehumidification performance evaluation index served as the dependent variable.

4.2.1. Experimental Conditions

The indoor environment has a considerable impact on the dehumidification performance of household dehumidifiers. In comparison to the dry climate in northern China, the southern region experiences higher humidity levels, rendering it more conducive for the promotion of household dehumidifiers. For this study, the experimental conditions outlined in

Table 4. Experimental conditions.

T	RH	d (g/kg)	T	RH	d (g/kg)
20 °C	60%	8.73	30 °C	60%	16.04
	70%	10.21		70%	18.8
	80%	11.70		80%	21.57
	90%	13.19		90%	24.38
25 °C	60%	11.90	35 °C	60%	21.44
	70%	13.92		70%	25.16
	80%	15.96		80%	28.92
	90%	18.01		90%	32.73

were selected based on the average temperature and humidity conditions observed in Guangzhou over recent years. The regeneration temperatures chosen were 120 °C, 130 °C, 140 °C, and 150 °C. The aforementioned experimental conditions were replicated within an environmental chamber situated in Beijing, China.

4.2.2. Evaluation Indicators

In this study, we defined the condensate amount during operation as D1, the input power as W, the inlet air temperature of the dehumidifier as Tin, the outlet air temperature as Tout and the operation time as t.

The dehumidification rate (Dr) was calculated as the ratio of the condensate amount to the operation time:

$$\mathrm{Dr}=\frac{{\mathrm{D}}_1}{\mathrm{t}}$$

(1)

The dehumidification capacity per power (DCPP) was calculated as the ratio of the dehumidification rate to the input power under nominal operating conditions:

$$\mathrm{DCPP}=\frac{{\mathrm{D}}_1}{\mathrm{tW}}$$

(2)

The temperature increase at the inlet and outlet (ΔT) was calculated as the difference between the outlet temperature of the treated air and the inlet temperature.

$${\mathsf{\Delta }\mathrm{T}=\mathrm{T}}_{\mathrm{out}}{ - \mathrm{T}}_{\mathrm{in}}$$

(3)

4.2.3. Uncertainty Analysis

To ensure the practical significance of our analysis, it is essential to establish the accuracy of the data. We will consider both type A and type B uncertainties simultaneously. Type-A uncertainty pertains to the variability observed in repeated measurements and can be determined using statistical methods. Specifically, type-A uncertainty for a function f of a set of measured independent variables xi can be obtained using Equation (4). On the other hand, type B uncertainty arises from the inherent uncertainty of the measuring device itself and can be estimated utilizing Equation (5). The corresponding synthetic relative standard uncertainty can be calculated using Equation (6).

$${\mathrm{u}}_{\mathrm{A}}\left(\mathrm{f}\right)=\sqrt{\frac{{\displaystyle \sum _{\mathrm{i}=1}^{\mathrm{n}}}{(\mathrm{f}}_{\mathrm{i}}-\overline{\mathrm{f}}{)}^2}{\mathrm{n}(\mathrm{n} - 1)}}$$

(4)

$${\mathrm{u}}_{\mathrm{B}}(\mathrm{f})=\sqrt{{(\frac{\partial \mathrm{y}}{\partial {\mathrm{x}}_1})}^2{(\frac{\Delta {\mathrm{x}}_1}{\mathrm{f}})}^2+{(\frac{\partial \mathrm{y}}{\partial {\mathrm{x}}_2})}^2{(\frac{\Delta {\mathrm{x}}_2}{\mathrm{f}})}^2+\dots +{(\frac{\partial \mathrm{y}}{\partial {\mathrm{x}}_{\mathrm{n}}})}^2{(\frac{\Delta {\mathrm{x}}_{\mathrm{n}}}{\mathrm{f}})}^2}$$

(5)

$${\mathrm{u}}_{\mathrm{C}}\left(\mathrm{f}\right)=\sqrt{{\mathrm{u}}_{\mathrm{A}}^2+{\mathrm{u}}_{\mathrm{B}}^2}$$

(6)

Table 5. Uncertainty analysis.

Parameters	Total Error	Total Uncertainty
Dr	±0.393 g/h	±0.184%
DCPP	±4.489 g/(kW·h)	±0.812%
ΔT	±0.474 °C	±3.480%

provides an overview of the uncertainties associated with each evaluation indicator during the measurement process. Based on our analysis of the uncertainty results, we can conclude that the test results fall within an acceptable error range, thereby accurately reflecting the performance of the dehumidifier.

4.3. Analysis of the Dehumidification Performance

4.3.1. Effect of Treated Air Temperature and Humidity

During the experiment, the regeneration temperature was maintained at 150 °C and the treated air under different temperature and humidity conditions was simulated by an environmental chamber.

Figure 13 displays the Dr, DCPP, and ΔT of the three DWs under varying temperature and humidity conditions. The analysis reveals that Dr increases with increasing RH. It initially increases and then decreases with temperature, peaking at 25 °C. At high humidity levels, the Dr values of the GF DW and CM DW are comparable, whereas that of the Al DW is 13% greater than that of the others. As humidity increases, the water vapor pressure differential also increases, promoting better adsorption. With increasing temperature, the temperature difference between the regeneration air inside the condenser and the treated air decreases, resulting in a reduced condensation rate and decreased dehumidification capability of the household dehumidifier. When the treated air temperature is low (Tin < 25 °C), the limiting factor for dehumidification is the adsorption rate of the desiccant. When the temperature increases (Tin > 25 °C), the regeneration air condensation rate becomes the main limiting factor for dehumidification. Consequently, Dr exhibits a decreasing trend. At the same regeneration temperature, the power consumption of the device remains consistent, and the DCPP follows a similar trend to that of the dehumidification capability. Specifically, the DCPP of the Al DW was 11.3% greater than that of the GF DW and 12.56% greater than that of the CM DW.

The temperature rise at the inlet and outlet is influenced by the heat exchange of the condenser, the adsorption heat of the desiccant, and the heat storage of the DW. At the same treated air temperature, the temperature increase in the three DWs increases with increasing relative humidity, and the temperature increase in the Al DWs is consistently lower than that of the GF DWs and CM DWs under all operating conditions due to the lower heat storage capacity of the former.

4.3.2. Effect of Regeneration Temperature

The regeneration temperature directly affects the desorption effect of the desiccant material on the regeneration side. For this study, the selected regeneration temperatures were 120 °C, 130 °C, 140 °C, and 150 °C.

Figure 14a illustrates the dehumidification rate at different regeneration temperatures. The Dr of the GF DW and CM DW increased as the regeneration temperature increased. The curve tends to plateau at 140 °C. At the same regeneration temperature, the Al DW exhibited the highest dehumidification capacity, with 9.24% and 10.45% increases at 150 °C. These results imply that using aluminum desiccant wheels effectively reduces the regeneration temperature and energy consumption of the dehumidifier under the same dehumidification load.

Figure 14b illustrates that the DCPPs of the GF DWs and CM DWs initially increase and then decrease as the regeneration temperature increases. It reaches its peak at 130 °C, with values of 0.537 kg/(kW·h) and 0.54 kg/(kW·h), respectively. On the other hand, the DCPP of the Al DWs continuously decreased. At 120 °C, the DCPP of the Al DWs was 13% greater than that of the CM DWs. Lowering the regeneration temperature (T < 130 °C) significantly improved the desorption effect, thus enhancing the dehumidification capacity of household dehumidifiers. However, increasing the regeneration temperature (T > 130 °C) leads to an increase in the power consumption of household dehumidifiers. Nevertheless, the dehumidification capacity tends to stabilize, and the impact of the regeneration temperature on the input power outweighs its influence on the dehumidification capacity.

The change in regeneration temperature affects the adsorption heat of the regeneration air and the heat storage of the desiccant wheel. Figure 14c demonstrates that the temperature increase in the three types of desiccant wheels decreases as the regeneration temperature decreases. This is attributed to the decrease in the dehumidification capacity and adsorption heat when the regeneration temperature decreases. Notably, the Al DWs exhibited the lowest heat storage, resulting in a temperature increase that was 0.9 °C lower than that of the CM DWs.

5. Optimization of the Household Dehumidifier

5.1. Optimization

In residential dehumidifiers, air is initially passed through a condenser to elevate its temperature before being directed to the desiccant wheel. However, this configuration presents two issues: (1) The proximity of the desiccant wheel to the condenser results in high regeneration air temperatures, which impacts the condensation rate and diminishes the dehumidification effect. (2) Figure 15 displays the temperature increase (ΔT1) of the processed air after passing through the condenser. Heating the air through the condenser is not conducive to desiccant adsorption, further affecting the dehumidification process.

Figure 16 presents an enhancement to residential dehumidifiers. The processed air bypasses the condenser and enters the desiccant wheel directly, reducing the incoming air temperature during dehumidification and enhancing the dehumidification effect. Additionally, the condenser is relocated away from the desiccant wheel, and the regeneration air is guided into the condenser through air ducts.

5.2. Dehumidification Performance

5.2.1. Performance under Different Air Temperatures and Humidities

Figure 17a depicts the dehumidification rates of three types of dehumidification wheels—GF DW, Al DW, and CM DW—under two different operating conditions. The dehumidification rates are 0.2125 kg/h, 0.2345 kg/h, and 0.2115 kg/h for the GF DW, Al DW, and CM DW, respectively, under one condition and 0.2075 kg/h, 0.24 kg/h, and 0.206 kg/h for the GF DW, Al DW, and CM DW, respectively, under the other condition. Compared to those of the original system, the dehumidification rates improved by, on average, 10.82%, 11.5%, and 9.29% for the GF DW, Al DW, and CM DW, respectively. Figure 17b demonstrates that after changing the air intake method, all three types of dehumidification wheels show average increases of 10.67%, 11.65%, and 9.28% in the DCPP. By improving the air intake method, the processed air can directly enter the dehumidification wheel. This results in a decrease in temperature, an increase in the dehumidification rate, and no change in regeneration temperature before and after the improvement, leading to a decrease in DCPP. Figure 17c shows that, compared to that of the original system, the average temperature increase in the three dehumidification wheels decreased by 4.52 °C, 3.78 °C, and 4.41 °C, respectively.

5.2.2. Performance under Different Regeneration Temperatures

Figure 18a displays the dehumidification rates of the GF DW, Al DW, and CM DW at various regeneration temperatures. At 150 °C, the dehumidification rates increased by 11.8%, 11.9%, and 10%, respectively, compared to those of the original system. Figure 18b shows that the maximum DCPPs of the GF DW and CM DW were 0.593 kg/(kW·h) and 0.59 kg/(kW·h), respectively, at 130 °C. At 150 °C, the DCPP increased by 11.6%, 12.1%, and 10% for the GF DW, Al DW, and CM DW, respectively, compared to that of the original system. Figure 18c illustrates the temperature increases at different regeneration temperatures. Compared to those of the original system, the improvements in the inlet and outlet temperatures for the three wheels are 3.85 °C, 3.34 °C, and 3.8 °C greater on average, respectively.

The performance of the improved dehumidifier increased by more than 10%. For example, the original CM DW system has a dehumidification rate of 0.19 kg/h at 150 °C. In contrast, the Al DW achieved a dehumidification rate of 0.198 kg/h at 130 °C. This indicates that the Al DW only requires a temperature of 130 °C to achieve the same dehumidification rate as the original system’s Al DW at 150 °C, thereby reducing energy consumption and achieving energy savings.

6. Conclusions

In this paper, fumarate aluminum hybrid desiccant material was prepared and its performance in household dehumidifiers was studied. The summary of the research results is as follows:

(1) At a temperature of 25 °C and a relative humidity of 80%, 25-LiCl@Al-Fum has the highest adsorption capacity. However, 25-LiCl@Al-Fum1 Completely liquefy after one hour. The optimal ratio of mixed desiccant materials is 20-LiCl@Al-Fum.

(2) Module experiments demonstrated that a 15% volume concentration of neutral silica sol is the optimal choice for the binder. Compared to glass-fiber modules, aluminum modules exhibit greater regeneration efficiency and are more suitable as the base material for desiccant wheels.

(3) The air temperature, humidity, and regeneration temperature significantly impact the dehumidification performance. However, under various operating conditions, the Al DWs consistently exhibited the highest dehumidification performance.

(4) The structure of household dehumidifiers was optimized. The dehumidification rate and DCPP of the optimized household dehumidifier have increased, while the temperature rise has decreased.