Desiccant Coated Heat Exchanger Research Articles

Experimental and numerical studies on moisture adsorption/desorption characteristics across the circular fin tube desiccant coated heat exchanger

To improve the energy transfer abilities, enhance the quality of air, and curtail the growth of microorganisms, the desiccant coated heat exchangers are a capable substitute compared to conventional heat exchangers due to their capability of decoupling the sensible and latent loads and utilizing low-grade thermal energy. The concept of desiccant coated heat exchangers (DCHE) can be employed in various heat exchange/transport systems like heat pumps, atmospheric water harvesters, adsorption chillers, and air conditioners. Thus, in this research work, a circular fin tube desiccant coated heat exchanger (DCCHE) has been proposed and designed and a dynamic numerical model is established for simulating the combined heat and mass transport occurring across the adsorption/desorption process of a DCCHE employing finite element approach. The moisture and temperature distribution and flow of fluid are considered in the transient numerical model covering several domains such as water flow, air flow, and the coated desiccant. The desiccant material utilized in the current analysis is silica gel. The validation study showed good agreement, and the maximum error between the experimental result and simulated model for the humidity ratio of air and temperature of outlet air were observed to be ± 8 % and ± 7 %, respectively. A parametric analysis is carried out to assess the effect of varying the different input parameters on DCCHE’s performance. The field emission scanning electron microscopy results concluded that a uniform coating is formed on the circular fin surface. The experimental examination on the sorption kinetics of the silica gel showed that the moisture uptake capability was 0.34 g/g. Moreover, the proposed circular fin tube desiccant coated heat exchanger has been compared with the conventional plate type fin tube DCHE to assess its performance in terms of thermal coefficient of performance and specific dehumidification energy.

Investigations of Silica/MOF composite coating and its dehumidification performance on a desiccant-coated heat exchanger

Desiccant materials have an important impact on the dehumidification performance of desiccant-coated heat exchanger (DCHE). In this paper, a desiccant-coated heat exchanger based on a composite desiccant material of metal organic frameworks (MOFs) and silica gel was proposed. The coating was experimentally prepared and tested for its hygroscopic performance under different binder types (PVP, PVA, and PVB), different binder mass concentrations, and different MOF mass concentrations in the composite adsorbent. Further simulations were performed to investigate the effects of key structural and operational parameters on the performance of DCHE. Experimentally, the optimal hygroscopic performance of the composite adsorbent was obtained at 15wt% PVP and 20wt% MOF, which was 51.71% higher than that of silica coating, and the cost of the composite adsorbent drops 78.04% by comparing to the pure MOF for laboratory fabrication, and based on the novel economic efficiency index proposed in this paper, the mass concentration of the MOF should not exceed 32.8wt%. Simulation results showed that under the conditions as follows: 1.2mm (fin spacing), 25mm (fin height), 0.28mm (coating thickness), 25 °C (cooling water temperature), and 0% (initial moisture content), the corresponding moisture removal capacity (MRC) and of DCHE was 6.740g/kg, which was 149.63% higher than that of silica coating.

Novel MOF-303/G coated wire-finned heat exchanger for dehumidification applications–Experimental investigation

Adsorption dehumidification outperforms other technologies regarding moisture removal rate, lower energy consumption, and environmental friendliness. The selection of desiccant material, the heat exchanger used, and the method of regeneration significantly impact the performance of desiccant dehumidifiers in terms of water vapour removal rate and energy consumption. Metal-organic framework materials are a new class of microporous materials with high water adsorption characteristics compared to conventional desiccants like silica gel. In this work, a novel MOF-coated electrically heated wire finned heat exchanger was developed, and its performance was experimentally investigated. Wire-finned tubes coated with MOF-303/G outperformed other wire-finned tubes coated with Aluminium fumarate, MIL-100(Fe), MIL-100(Fe)/G, MOF-801 and MOF-801/G, achieving water uptake of 22 %. Also, the addition of graphene nanoplatelets during the synthesis of MOF-303 resulted in a significant enhancement of its thermal diffusivity to reach 0.184–0.23 mm2/s at temperatures ranging between 25 °C and 115 °C. The Coefficient of Performance (COP) for the developed multi-tube MOF-303/G coated heat exchanger was experimentally tested and compared to other desiccant-coated heat exchangers. Results showed that COP values ranging from 0.6264 to 1.02 to 1.2 at the regeneration temperatures of 45 °C, 60 °C and 70 °C, respectively, were achieved, which are higher than those reported in the literature.

Novel MOF-303/G Coated Wire-Finned Heat Exchanger for Dehumidification Applications – Experimental Investigation

Adsorption dehumidification outperforms other technologies regarding moisture removal rate, lower energy consumption, and environmental friendliness. The selection of desiccant material, the heat exchanger used, and the method of regeneration significantly impact the performance of desiccant dehumidifiers in terms of water vapour removal rate and energy consumption. Metal-organic framework materials are a new class of microporous materials with high water adsorption characteristics compared to conventional desiccants like silica gel. In this work, a novel MOF-coated electrically heated wire finned heat exchanger was developed, and its performance was experimentally investigated. Wire-finned tubes coated with MOF-303/G outperformed other wire-finned tubes coated with Aluminium fumarate, MIL-100(Fe), MIL-100(Fe)/G, MOF-801 and MOF-801/G, achieving water uptake of 22%. Also, the addition of graphene nanoplatelets during the synthesis of MOF-303 resulted in a significant enhancement of its thermal diffusivity to reach 0.184 to 0.23 mm2/s at temperatures ranging between 25°C and 115°C. The Coefficient of Performance (COP) for the developed multi-tube MOF-303/G coated heat exchanger was experimentally tested and compared to other desiccant-coated heat exchangers. Results showed that COP values ranging from 0.6264 to 1.02 to 1.2 at the regeneration temperatures of 45°C, 60 °C and 70 °C, respectively, were achieved, which are higher than those reported in the literature.

Experimental analysis and investigation of desiccant coated heat exchanger applications involving condensation and sorption mechanisms

This study focuses on the application of desiccant coated heat exchangers (DCHEs) in conditions where condensation occurs below the dew point temperature. Previous experimental studies on DCHEs and DCHPs have predominantly examined the sorption mechanism above the dew point, leaving a gap regarding material selection and system design in the presence of condensation. To address this, a guide is introduced that combines the understanding of condensation and sorption processes for desiccant applications. The guide is applied to evaluate the suitability of a superabsorbent-LiCl (SAP-LiCl) composite desiccant for desiccant coated heat pump (DCHP) applications. The stability of the desiccant in the presence of condensed water droplets is validated. Additionally, an experimental investigation explores the relationship between sorption and condensation mechanisms, identifying the transitional coolant temperature at which dehumidification shifts from condensation-dominant to sorption-dominant. By incrementally adjusting the coolant temperature in 5 °C steps, the transitional temperature of the SAP-LiCl based DCHE is determined to be approximately 15 °C under the target operation scenario, rendering its suitability for additional below-dew-point applications. The study reveals optimal operational parameters for DCHE, demonstrating a potential energy saving of 20 %. Based on these findings, a DCHP prototype is constructed to assess the feasibility of DCHE in real-world applications. The transient behaviors of this prototype are analyzed during each operating cycle, yielding a coefficient of performance of 4.97 and a cooling capacity of 1.5 kW under baseline operating conditions.

Experimental study on wavy fin desiccant coated heat exchanger for hybrid air conditioning systems

The desiccant-coated heat exchanger (DCHE) is an energy-efficient alternative dehumidification equipment for humidity control in air conditioning. It exhibits a higher dehumidification performance than other solid desiccant systems and can simultaneously handle both latent and sensible loads. Taking the clue of research outcomes from the alternative heat exchangers to enhance the performance, a wavy fin DCHE is designed, fabricated and tested. Objectives of the study are to (i) analyse the dynamic performance of DCHE, (ii) compare the heat and mass transfer characteristics of plain and wavy fin-type DCHEs, and (iii) examine the influence of different operating parameters on the performance. The experimental investigation shows that the dehumidification capacity and thermal coefficient of performance of the proposed wavy fin DCHE are 0.34 g/s and 1.041, respectively, which are 75% and 60% higher than the conventional plain fin type. In addition, the developed DCHE has an average cooling capacity of 0.85 kW, which is 42% higher. Besides, the total quantity of moisture adsorbed also increased by 35%. Furthermore, the sensitivity analysis of the parametric study identified air velocity, cold water temperature, and inlet humidity ratio as the most influential operating parameters on the performance of wavy fin DCHE.

Solar regenerated carbon-based composite desiccant coated heat exchangers for air dehumidification

Desiccant dehumidification can realize decoupling of latent and sensible heat loads in dehumidified air conditioning, thereby reducing energy consumption. This paper proposes a solar regenerated carbon-based composite desiccant coated heat exchangers (DCHE) for air dehumidification. Carbon-based composite desiccant is electrostatically sprayed onto the surface of the heat exchanger to form a dehumidification coating. An experimental system for evaluating the dehumidification and regeneration performance of DCHE is established. The Taguchi method is employed to evaluate the impact of operating parameters such as air velocity, water flow rate, and regeneration temperature on the dehumidification and regeneration efficiency of DCHE. The result shows that air velocity is the primary factor impacting the dehumidification performance of DCHE, with regeneration temperature and cooling water flow rate following in importance. With the faster air velocity and the lower cooling water flow rate, DCHE shows the better dehumidification performance. Moreover, excessively both high and low regeneration temperatures can result in a degradation in the dehumidification performance of DCHE. Under optimal operating conditions, the dehumidification rate (EDE) and thermal coefficient of performance (COPth) of DCHE can reach 7.5 kg/h and 2.3, respectively. The moisture content of the air reduces from 19.6 g/kg to 8.0 g/kg.

Effect of polyvinylpyrrolidone and lithium chloride composite desiccant-coated heat exchangers on dehumidification studies

Cooling systems are necessities that remain energy intensive, particularly in tropical regions with elevated humidities and temperatures. Conventional vapor-compression air-conditioners are often inefficient because the sensible and latent heat loads are intrinsically coupled. To realize more energy-efficient cooling, solid desiccant-coated devices can be introduced to mitigate the latent heat load. Among such devices, desiccant-coated heat exchangers (DCHEs) are attractive for enabling nearly isothermal dehumidification. Hence, desiccants with high sorption capacity and rapid kinetics are essential. Solid polymeric desiccants are well-positioned to meet these requirements but comprehensive studies on the dehumidification performance of solid polymeric desiccant-coated heat exchangers are currently lacking. In this study, we investigated the potential of polyvinylpyrrolidone (PVP) and lithium chloride (LiCl) composites as desiccant materials at both material and system levels in terms of gravimetric water uptake. Specifically, LiCl is a hygroscopic salt bound by the moisture-sorbing PVP matrix. This work also demonstrates how the Elovich model accurately predicted the PVP-LiCl composite’s sorption kinetics. The results show that the optimum PVP-LiCl composite ratio is 66.7 wt%, with an equilibrium sorption capacity of 280 % at 75 % RH and 25 °C, compared to 29 % for silica gel under the same condition. With much superior sorption kinetics and capacity, the PVP-LiCl-coated prototype heat exchanger demonstrated a moisture removal capacity eight times higher than a silica gel-coated one under dynamic flow towards energy savings in air-conditioning systems.

Performance study of a heat pump fresh air unit based on desiccant coated heat exchangers under different operation strategies

Fresh air system is getting more and more important nowadays. The heat pump fresh air system based on the desiccant coated heat exchanger (DCHE) that can handle the latent and sensible load of fresh air efficiently has a large energy saving potential. To improve the performance of the heat pump fresh air system based on DCHE, in this paper, a control system based on PLC is established and the operation strategies of the system are investigated. An operation strategy including automatic control of the opening of the electronic expansion valve based on the suction superheat of the compressor, control of the switchover period based on the relative humidity of supply air, and control of compressor frequency based on evaporation and condensation temperature is established. By using the optimal operation strategies, the dehumidification rate and COP of the system can reach 4.42 kg/h and 6.2 in summer, compared with the unoptimized strategy it increased 8% and 25%, respectively. The two performance indices can reach to 3.04 kg/h and 6.98, with an increase of 89% and 78%.

Theoretical study on the dehumidification behaviors of dual-desiccants coated cross-flow heat exchanger with staged adsorption-desorption process

The conventional desiccant coated heat exchangers (DCHEs) suffer from the inefficient utilization of regenerative energy and the inadequate dehumidification capacity of a single desiccant. In this study, a concept of dual-desiccants cross-flow DCHE with staged adsorption-desorption process was proposed to strengthen dehumidification capacity and energy efficiency simultaneously. In order to guide the construction of proposed DCHE, the steady-state dehumidification capacity of single-desiccant (specifically, silica gel, FAM Z01, FAM Z05 and EMM-8) cross-flow DCHE was investigated by thermodynamic analysis. The dual-desiccants cross-flow DCHE was thus constructed, and its numerical model was established to investigate the dehumidification characteristics. Theoretical analysis revealed that single-desiccant cross-flow DCHEs exhibit different optimal relative humidity ranges for dehumidification. The minimum regeneration temperature driving dehumidification cycle increases as the lower supply air humidity is required. Numerical results demonstrated that the staged adsorption process ensures a large dehumidification capacity across a wide humidity range, including low humidity conditions. Meanwhile, the staged desorption process facilitates the cascade utilization of energy and the direct recovery of regenerative waste heat. For dual-desiccants cross-flow DCHE utilizing silica gel and EMM-8, the moisture removal capacity and dehumidification coefficient of performance can reach 0.012 kg/kg and 0.41, respectively.

Experimental investigation of a thermo-responsive composite coated heat exchanger for ultra-low grade heat utilization

There is a growing interest in desiccant coated heat exchanger (DCHE)-based systems due to characteristics of isothermal dehumidification and compact structure. To enhance the dehumidification efficiency and reduce the regeneration temperature of DCHE-based systems, a thermo-responsive composite desiccant coated heat exchanger (PSLCHE) was developed. This study focuses on investigating the influence of operating parameters (such as air temperature, relative humidity, regeneration temperature and adsorption/desorption time ratio) on the dynamic performance, average dehumidification capacity (Davg) and thermal coefficient of performance (COPth) of the system. Under the air condition of 30 °C & 60% RH, the PSLCHE demonstrates remarkable performance with the Davg of 7.3 g·kg−1 and COPth of 0.93 at 40 °C. This study provides a route to the design of highly efficient air conditioning systems using thermo-responsive composite for ultra-low grade thermal energy at 40 °C.

Performance evaluation of wavy fin desiccant coated heat exchanger for hot and humid climatic conditions

The desiccant coated heat exchanger (DCHE) is a novel type of solid desiccant equipment that can simultaneously handle both latent and sensible loads. The systems based on DCHE are considered as an energy efficient alternative to dehumidification in conventional air conditioning. Hence, the present study proposes a novel wavy fin based DCHE which can perform better than plain fin configuration. The main objectives of this paper are (i) to numerically evaluate the heat and mass transfer characteristics of wavy fin DCHE and compare them with the plain fin type, (ii) to propose a novel method of estimating the effective cycle time for DCHE operation, and (iii) to identify the critical geometric and operating parameters influencing the performance of DCHE. The investigation reveals that the dehumidification capacity of the proposed wavy fin DCHE is 61% higher than that of the plain fin DCHE. Further, the dehumidification increases by 53% when the DCHE is operated on the proposed effective cycle time. In this work (i) a high performance DCHE based on wavy fin configuration is proposed, (ii) a methodology for determining and operating the DCHE on an effective cycle time is presented and (iii) an overview to choose a suitable geometric design for wavy fin DCHE in air conditioning applications is provided.

Performance evaluation of MIL-101(Cr) based desiccant-coated heat exchangers for efficient dehumidification

Metal-organic frameworks (MOFs) with ultrahigh water uptake and moderate regeneration temperature are ideal sorbents for desiccant-coated heat exchangers (DCHEs). Herein, MIL-101(Cr) is synthesized through the hydrothermal method and the product shows an exceptional adsorption capacity of 1.17 g/g at 90 % RH and steep water uptake at middle RH (P/P0 = 0.35–0.45). Then MIL-101(Cr) coated heat exchangers (MCHE) are fabricated by the spraying method and a testing platform is established to investigate the dehumidification performance. Parameter analysis revealed that a medium switchover period (9–12 min), low-temperature heat sources (48–60 °C), and lower cooling water temperature facilitate the overall performance. Experiments under two different heat exchanger layouts are conducted, showing MCHEs in the parallel mode present better heat/mass transfer performance and MCHEs in the series mode tend to acquire higher heat recovery efficiency (η). Hot and humid climates are favorable in both modes while low-RH climates require lower inner cooling fluid temperature. Under five typical inlet air conditions, the dehumidification capacity of the parallel mode and the series mode ranges from 0.26 to 0.43 kg/h and 0.24–0.40 kg/h, and the η ranges from 0.30 to 0.47, 0.32–0.53, respectively.

Performance evaluation of a high-efficient hybrid adsorption refrigeration system for ultralow-grade heat utilization

50–80 °C heat sources are abundant in renewable energy areas and industrial processes. However, they are difficult to be effectively used due to their ultralow grade. In order to solve this problem, this paper presents a high-efficient hybrid adsorption refrigeration system combing with desiccant coated heat exchangers. In this study, the performance of the hybrid system is experimentally investigated and parametric effects are fully discussed. Results indicate that the hybrid system operates efficiently across a wide heat source range of 50–80 °C. A high-temperature hot water facilitates the cooling production of the hybrid system, while a low-temperature hot water is more beneficial to the COP promotion. Also, a lower cooling water temperature, higher air temperature, higher relative humidity and longer switch time can enhance system performance. The optimal cooling capacity is quantified as 4579 W when powered by 80 °C hot water and the COP reaches its maximum of 0.673 under a heat source temperature of 50 °C. Comparison results show that compared with present systems, the hybrid system has greater adaptability as well as higher efficiency in utilizing 50–80 °C ultralow-grade heat sources, and can satisfy the simultaneous demand for cooling and dehumidification, which offers a promising way to high-efficient energy utilization and sustainable development.

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.

Experimental study on the performance of a novel superabsorbent polymer and activated carbon composite coated heat exchangers

Desiccant coated heat exchangers have attracted great attention for their ability to handle both sensible and latent heat loads. However, widely used salt-embedded composite silica gels risk salt solution leakage. To alleviate this problem, a novel superabsorbent polymer (sodium polyacrylate) and activated carbon composite coated heat exchanger (C-DCHE) was developed and tested. Effects of air-side and water-side parameters on the performance of C-DCHE in terms of average dehumidification capacity (Davg) and thermal coefficient of performance (COPth) were investigated and compared to an activated carbon coated heat exchanger (A-DCHE). With the outdoor air of 38 °C&60% RH, Davg and COPth of C-DCHE can be up to 6.1 g kg−1 and 3.6, an improvement of 43% and 26% over A-DCHE, respectively. Besides, the performance of C-DCHE was compared with conventional and salt-embedded silica gels coated heat exchangers in recent publications. C-DCHE showed superior air supply comfort owing to a lower average outlet air humidity ratio and larger COPth under most conditions. Especially, at low regeneration temperatures of 40∼50 °C, its COPth can be 50%–220% higher. This paper provides a promising direction for salt-free composites in DCHE-based systems.

Performance assessment of heat exchanger coated with encapsulated ultra-high salt content desiccant

Desiccant coated heat exchanger (DCHE) provides an effective way to decouple the sensible and latent heat loads and improves the energy efficiency by raising the evaporation temperature of air conditioning system. In this paper, a new encapsulation of porous membrane is adopted to fabricate the ultra-high salt content composite desiccant, AFLi30@P, whose salt content can reach over 85w %. Its adsorption capacity can be as high as 3.8 g g−1 at 27 °C and 70 % humidity. And then, DCHE based on AFLi30@P is developed. Experiments on both desiccant and DCHE levels are conducted to investigate the effects of temperature and humidity conditions on the dehumidification performance. The results reveal that, different from air temperature and dehumidification temperature, air humidity and regeneration temperature has positive effects on the DCHE dehumidification performance. Comparison between vertical and horizontal placements presents that horizontal placement of AFLi30@P on DCHE can avoid the effect of gravity to realize more uniform adsorption and heat transfer capacity. Dehumidification capacity of AFLi30@P DCHE can reach 1.08 g g−1 under the conditions of 27 °C air temperature, 70 % air humidity, 30 °C dehumidification temperature and 60 °C regeneration temperature.

Experimental Investigation on Dehumidification Using a Solid Composite Bio Desiccant Internally Cooled Using Nanofluids for Building Cooling

Indoor comfort has become a major factor with advancements in science and technology. This also leads to an increase in greenhouse gases as well as energy consumption. Desiccant-coated heat exchangers are one of the common solutions to these risks and to lower energy usage. In the present work, the capability of a solid composite desiccant blend prepared from coconut shell-based activated carbon and bio char was studied. Aluminum plates have been coated with the prepared solid desiccants. Desiccant-coated heat exchangers were cooled by the cerium oxide nanofluid passing through the pipes connected along the length of the heat exchanger. Air was blown through the plates where dehumidification occurs due to the vapor pressure difference between the air and the desiccant-coated plate. The experiments were conducted by varying the air velocity, water flow rate, and nanoparticle concentration. The nanoparticle volume fraction varied from 0.05% to 0.3%. Different performance parameters such as the moisture removal rate, dehumidification efficiency, cooling capacity, and coefficient of performance (COP) were calculated. Results showed that the performance parameters were enhanced with an increase in the water flow rate as well as the air flow rate. Furthermore, it was seen that with the addition and increase in nanoparticle concentration, the moisture removal rate and dehumidification efficiency were enhanced. In comparison to no addition of nanoparticles, a 0.3% addition of nanoparticles demonstrated a maximum increase in MRR of 53% and dehumidification efficiency of 57%. A maximum reduction of 6.1% in the dehumidification area was achieved by using 0.3% nanoparticles with water. It is recommended to use nanofluids for dehumidification using solid desiccants, which can enhance the performance without having negative influence on the environment.

Energy and exergy analyses of a hybrid adsorption refrigeration system for simultaneous production of cold water and dry air

Current adsorption refrigeration systems are limited by dehumidification methods and produce either cold water or cold dry air. The single cooling product greatly hinders their application into situations where multiple cooling outputs are needed. In order to address this issue, this paper introduces a hybrid adsorption refrigeration system using efficient desiccant coated heat exchangers to provide both cold water and dry air via the deep utilization of input heat sources. In this study, the performance of the hybrid system is experimentally investigated from a combined perspective of energy and exergy. Results show that the hybrid system can simultaneously output cold water and dry air with a heat source of 50–80 °C. A low-temperature cooling water is beneficial to system performance, while an optimum input hot water temperature exists. At a coolant-side temperature of 25 °C, the COP reaches its maximum of 0.238 under a heat source temperature of 60 °C, and the highest exergetic efficiency is quantified as 13.9% when powered by 50 °C hot water. Increasing inlet air temperature or relative humidity facilitates the COP improvement but has a negligible effect on the exergetic efficiency. In comparison with a traditional adsorption air conditioning system, the hybrid system has a wider range of input hot water temperatures and is more advantageous in terms of cooling exergy and exergetic efficiency. This hybrid system firstly enables adsorption refrigeration to export dual cooling products of cold water and dry air, which is expected to extend adsorption refrigeration into fully automatic industrial fields.

Highly efficient desiccant-coated heat exchanger-based heat pump to decarbonize rail transportation

In the rail sector, air conditioning accounts for 30% of the total operational energy consumption, thus, it is crucial to enhance the efficiency of air conditioning units (ACUs) to reduce overall energy consumption. Traditional ACUs for train vehicles usually have a low coefficient of performance (COP), often less than 2, because of condensation-based dehumidification and a consequent reheating process and also the restricted spaces to install ACUs on the rooftop of the cabinet. Herein, we present a novel ACU with an integrated structural design that uses desiccant-coated heat exchangers (DCHEs) coupled with heat pumps, providing comfortable air conditioning on the metro or high-speed trains. This approach provides a direct method for reducing the air temperature and humidity simultaneously, thus realizing the decoupling of temperature and humidity treatments on a single heat exchanger. Using this design, experimental results show that the proposed system can improve the COP by ∼40% under standard conditions compared with existing ACUs (2.5 vs. 1.8). In addition, the proposed system achieves the highest COP of 2.8 under Shenzhen ground conditions (high humidity and temperature conditions) and exhibits high adaptability to various climate zones. The application of the DCHE-based system in the rail sector can significantly contribute to the decarbonization of the sector and make rail transportation sustainable and ready for a green transformation.