Adsorption Chiller Research Articles

Entropy generation minimization of an advanced two-bed adsorption refrigeration system

This article presents the thermodynamic assessment of an advanced adsorption chiller with an aim towards entropy generation minimization through the selection of appropriate operating strategies, temperatures, and design modifications. The present study carries out a second law analysis of a two-bed silica gel water pair-based adsorption cooling system, with a focus on the under-explored aspects of a heat recovery strategy and auxiliary consumption-reducing measures. A second law performance index, viz. specific irreversibility, is introduced for effectively incorporating the entropy generation, auxiliary electricity consumption, and cooling capacity, and it has been further verified to be an indicator of second law efficiency. The performance of the system has been numerically evaluated under the normal and passive heat recovery strategies, where it is found that the passive heat recovery strategy offers a lower entropy generation by 63%. The study further investigates the second law efficiency impact of adopting a capillary-assisted evaporator for auxiliary electricity consumption reduction. It is observed that the specific irreversibility could reduce by up to 22% over a conventional falling film design. The analysis and results presented in this study are anticipated to increase the effectiveness of adsorption chillers for heat recovery applications.

Multigeneration source based on novel triple-component chiller configuration co-supplied with renewable and fossil energy operated in Arabic Peninsula conditions

Innovative hybrid source for electricity, cooling and desalinated water production based on a mixed fossil fuel/solar energy supply, equipped with triple-component chiller configuration, has been presented in the paper. The system was erected and recently commissioned in King Abdulaziz City for Science and Technology (KACST) in Kingdom of Saudi Arabia to operate as a working laboratory supplying media to adjacent buildings of the Solar Village complex. In the Arabian Gulf region, increased demand, especially for cooling and desalinated water, as well as fluctuating availability of electricity from the grid in summer period is visible, what makes such a stand-alone installation operation justified especially in remote areas. Abundant availability of intermittent solar energy correlated with cooling demand led to development of novel triple-component chiller configuration consisting of absorption, adsorption and compressor chiller. Two Diesel internal combustion engines had been selected to supply electricity and heating when solar energy is not available. Paper presents results of installation commissioning, during which the performance of the system for three different operating scenarios was assessed. Maximum efficiency was achieved for maximum renewable energy production option reaching 324.91% with renewable share at a level of 89.99%. For the maximum cooling capacity production, the efficiency of the system was 124.89% with 18.6% share of renewable energy. The lowest efficiency, of 93.09%, system obtained for the night scenario.

Possibilities of Using Zeolites Synthesized from Fly Ash in Adsorption Chillers

Adsorption chillers produce cold energy, using heat instead of electricity, thus reducing electrical energy consumption. A major industrial waste, fly ash, can be converted to zeolite and used in adsorption chillers as an adsorbent. In this research, three different types of zeolites were synthesised from fly ash via a hydrothermal reaction in an alkaline solution (NaOH). The obtained samples (Na-A zeolites) were modified with K2CO3 to increase the water adsorption capacity of these samples. Phase and morphology analyses shows that desired zeolites formed properly but other crystalline phases also exist along with nonporous amorphous phases. The determined specific surface areas for Na-A zeolite (12 h) and Na-A zeolite (24 h) are 45 m2/g and 185 m2/g respectively, while the specific surface area for synthesized 13X zeolite is almost negligible. Water-isotherm for each of these samples was measured. Considering the application of adsorption chillers, average adsorption capacity was very low, 1.73% and 1.27%, respectively, for the two most probable operating conditions for synthesized 13X zeolite, whereas no water was available for the evaporation from Na-A zeolite (12 h) and Na-A zeolite (24 h). This analysis implies that among the synthesized materials only 13X zeolite has a potential as an adsorber in sorption chillers.

A Novel Hybrid Polygeneration System Based on Biomass, Wind and Solar Energy for Micro-Scale Isolated Communities

The availability of freshwater and energy is a serious issue in remote and islanded areas, especially at a small scale, where there may not be the possibility to access the grid and/or water distribution systems. In this context, polygeneration systems operating on the basis of local, renewable energy sources can be an answer to the users’ demand for electricity, heating, cooling, and domestic hot water. The scope of the proposed paper was to investigate, numerically, the energy and economic feasibility of a novel hybrid polygeneration system powered by biomass, solar, and wind energy for a micro-district of households. The proposed system consists of a biomass-fueled steam cycle, wind turbine, photovoltaic field coupled with thermal and electrical energy storage, adsorption chiller, and a reverse osmosis water desalination unit. The system is also assisted by an LPG generator set running as backup. The system provides space heating and cooling, electrical energy, and fresh and domestic hot water to 10 households located on Pantelleria Island, Italy. The proposed system is modelled and simulated through TRNSYS software with realistic user demand. The energy and economic performance of the proposed system are assessed with respect to a reference system in different scenarios, taking into account islanded operation, connection to the grid, and biomass tariffs. The results show that the proposed system achieves an excellent primary energy saving performance in all the investigated scenarios, with savings of more than 94% for all the investigated scenarios. Excluding any kind of funding, in case of new investment for the system, the simple payback oscillates between 7 and 12 years, showing that the developed alternative is fairly valid with respect to traditional solutions.

Possibilities of Integrating Adsorption Chiller with Solar Collectors for Polish Climate Zone

Solar-powered adsorption chillers are a particularly interesting alternative to energy-intensive conventional refrigeration systems. Integration of the adsorption chiller with solar collectors is a very promising concept since the increase in solar radiation coincides with the increased demand for cooling. Such a solution is very economical and environmentally friendly. It also fits in with current trends related to energy policy and sustainable development. The article presents the results of tests conducted for a two-bed adsorption chiller integrated with solar collectors. The tests were performed on selected days of the summer period (July and August) at the KEZO Research Centre PAS in Jablonna (Poland). Based on the results obtained, the performance parameters of the adsorption chiller were determined, and the problems associated with the integration of all components of the system were identified and discussed. The values of the determined Coefficient of Performance (COP) and cooling capacity for the tested adsorption chiller are, depending on the day on which the tests were conducted, from 0.531 to 0.692 and from 5.16 kW to 8.71 kW, respectively. Analysis of the test results made it possible to formulate conclusions related to the design of integrated systems of adsorption chillers with solar collectors.

An Industrial Approach for the Optimization of a New Performing Coated Adsorber for Adsorption Heat Pumps

In the present work, the optimization of a new coating formulation was investigated, taking attention to an industrially focused research approach used for the engineering design of the adsorber. The adsorbent was a composite zeolite or silica-gel based coating applied by using new flexible polymer matrices. The FC-80 formulation represents a good compromise between mechanical stability and absorption capacity. Using the developed coating process, a new compact HEX design was developed to reach the AHP target performance with easy and fast manufacturing. The specific cooling power of the coated heat exchanger was estimated to be about 500 W/kg of adsorbent. The new coated HEX was integrated in a new adsorption chiller and has been tested by a laboratory test-rig under realistic operating conditions. Results of preliminary testing demonstrated that the prototype provides a cooling capacity of around 10 kW with a COP of 0.54.

Modeling and Simulation of a Two-Stage Air Cooled Adsorption Chiller with Heat Recovery Part I: Physical and Mathematical Performance Model

In the proposed work, the MATLAB program was used to model and simulate the performance of the investigated two-stage adsorption chiller with and without heat recovery using an activated carbon/methanol pair. The simulated model results were then validated by the experimental results conducted by Millennium Industries. The model was based on 10th order differential equations; six of them were used to predict bed, evaporator and condenser temperatures while the other four equations were used to calculate the adsorption isotherm and adsorption kinetics. The detailed validation is stated in the next paragraphs; for example, it clearly notes that the simulation model results for the two-stage air cooled chiller are well compared with the experimental data in terms of cooling capacity (6.7 kW for the model compared with 6.14 kW from the experimental results at the same conditions). The Coefficient of Performance (COP) predicted by this simulation was 0.4, which is very close to that given by the Carnot cycle working at the same operating conditions. The model optimized the switching time, adsorption/desorption time and heat recovery time to maximize both cooling capacity and COP. The model optimized the adsorption/desorption cycle time (300 to 400 s), switching cycle time (50 s) and heat recovery cycle time (30 s). The temporal history of bed, evaporator and condenser temperatures is provided by this model for both heat recovery and without heat recovery chiller operation modes. The importance of this study is that it will be used as a basis for future series production.

Energy, exergy, economic and environmental (4E) assessment of hybrid solar system powering adsorption-parallel/series ORC multigeneration system

Energy, exergy, economic and environmental assessment is performed for an integrated hybrid solar system powering a multigeneration system. The proposed multigeneration system is integrated parallel/series configurations of organic Rankine cycle (ORC) unit and adsorption chiller under weather conditions of Alexandria-Egypt. The solar subsystem comprises photovoltaic/thermal collectors (PVT) connected in parallel arrangement with evacuated tube solar collectors (ET). The system output aims to provide annual electricity requirements via PVT collectors and the ORC unit and supply cooling requirements during summer via an adsorption chiller for a small building. The hot water output of the solar system is used to drive the ORC unit and adsorption chiller in four configurations; (Conf-1) hot water drives the adsorption chiller, then its output hot water runs the ORC unit (series), (Conf-2) it drives the ORC first, then the adsorption chiller (series), (Conf-3) hot water is divided between adsorption and ORC (parallel), and (Conf-4) hot water drives only adsorption without using ORC unit. Moreover, the impact of the area ratio of the PVT to ET collector and the ORC working fluid and its flow rate on the system performance is investigated. A complete mathematical model is developed for the system components and solved using MATLAB software. The results show that Conf-4 has the best cooling production performance with an average value of 9.6 kW during the summer months and energy efficiency with an average value of 0.3 during August. Conf-1 is the best performing configuration in cooling production of about 5.6 kW average cooling capacity compared to Conf-2 and Conf-3. In contrast, Conf-2 has the best ORC unit performance with a maximum output of 1.2 kW on a typical day in July. Increasing the PVT collector area in the solar configuration negatively affects cooling production but increases electricity production, which augments the system’s overall exergy and energy efficiencies. R600 is the best ORC working fluid compared to R290 and R134a in terms of average ORC power production of about 0.72 kW compared to 0.63 kW for R290 and 0.39 kW for R134a. Conf-1 is found to have the best energy savings of about 50.8 MWh/year and thus the best emissions of approximately 10.06 equivalent tonCO2 per year. The system Payback period is about 9.8, 9.95, 9.9, and 8.45 years for Conf-1 to Conf-4, respectively, proving the system’s economic feasibility.

Thermochemical energy applications of green transition metal doped MIL–100(Fe)

Recently metal organic frameworks (MOFs), already known as adsorbent materials, have gained increasing research interest in thermal energy storage and conversion. MOF-water working pairs have been envisaged to provide the next revolutionary advancement in the existing sorption-based thermal energy storage and conversion systems. Herein, a promising MOF for high water sorption, MIL–100(Fe), and its transition metal-doped (Ni2+ and Co2+) derivatives are produced following a green synthesis procedure. The synthesized materials were tested in water sorption measurements using a thermogravimetric technique. The experimentally obtained adsorption data were correlated with the Sun-Chakraborty adsorption isotherm model. As an example of thermal energy conversion, an adsorption chiller is considered, and hence cooling cycles were drawn using the sorption data. The cooling cycles revealed that the nickel-doped MIL–100(Fe) demonstrates the highest value of the specific cooling effect (450.79 kJ kg−1) among the studied MOFs. Inverse gas chromatography technique was employed to investigate the surface free energy of the parent and doped MIL–100(Fe) MOFs. It was found that nickel-doped MIL–100(Fe) had the highest total surface free energy of 105.41 mJ m−2. Surfaces’ Lewis acid-base activities and the work of cohesion and adhesion (towards water molecules) were investigated. The surfaces’ properties were correlated with the water adsorption isotherms, which can provide crucial information for developing optimal adsorbents targeting water as the adsorbate for an efficient and effective thermal energy storage and conversion system.

Effectiveness and constraints of using PV/Thermal collectors for heat-driven chillers

• Dynamic simulation of a pilot adsorption chiller driven by flat photovoltaic thermal collectors (PVT-ADS) • Comparison among the proposed (PVT-ADS) system and a vapour compressor chiller driven by conventional PV (PV-VCC) collectors are presented. • The PVT-ADS system produces less cooling energy than the PV-VCC (35% and 3.5%), on the contrary the net electricity is greater (6% and 13.5%) respectively during a typical summer and peak day. • PVT-ADS systems could be one of the promising systems for generating cooling, thermal and electrical energy. In the last year, a continuous deeply increase in energy demands for cooling purposes is observed. Such energy needs are mainly satisfied through conventional vapour compressor chiller (VCC), which foresee the use of electricity usually generated through conventional energy sources. As an alternative, solar cooling plants offer a reliable and environmentally friendly for producing, in a sustainable way, cooling energy. This paper presents the analysis of the performances of an adsorption chiller (ADS) driven by solar energy operating in the Mediterranean area. In particular, this research aims to highlight the effectiveness and constraints of using photovoltaic/thermal (PVT) panels as the energy source of a heat-driven adsorption chiller (PVT-ADS). Since the PVT allow producing both thermal and electrical energy it is of fundamental importance to investigate the effects of the operative temperatures on the efficiency of the whole PVT-ADS system. The analysis was conducted developing a dynamic simulation model for a solar cooling plant, for which the adsorption chiller’s performances are derived by the 9.75 kW ADS, developed at the Gebze Technical University, Turkey. Cooling and power production has been explored as a function of the regeneration temperature of the ADS chiller. This analysis allowed us to point out the best design for the investigated PVT-ADS system. As a result, a regeneration temperature of 70 °C for a volume of the solar tank of 60 l/m 2 of PVT panel was defined. The investigated PVT-ADS, composed of 49.0 m 2 of glazed PVT panels achieves 51.9 and 40.3 kWh of cooling energy and electrical production respectively, during a typical summer day. Moreover, the comparison between the proposed PVT-ADS with a vapour compressor chiller driven by conventional PV modules (PV-VCC) is proposed. Such comparison shows that the PV-VCC produce about 2.9 kWh of cooling energy, per kW of nominal cooling power installed, more than the PVT-ADS system. Instead, the PVT-ADS guarantees the highest net electrical yield. The results of this study demonstrate the effectiveness of using PVT system as a potential source for solar cooling plants in the Mediterranean area.

Modeling and Simulation of a Two-Stage Air-Cooled Adsorption Chiller with Heat Recovery Part II: Parametric Study

This study is the second part of the theoretical study of “Modeling and Simulation of a Two-Stage Air-Cooled Adsorption Chiller with Heat Recovery”, which is based on developing a theoretical model for a two-stage adsorption chiller with an activated carbon/methanol pair. The following models were conducted numerically using MATLAB. The model was based on 10th order differential equations; six of them were used to predict bed, evaporator and condenser temperatures, while the other four equations were used to calculate adsorption isotherm and adsorption kinetics. In this second part, bed heat exchangers and evaporator and condenser heat exchangers are studied by varying the parametric design of a chiller. This includes but is not limited to activated carbon mass inside a single bed, overall heat transfer coefficient for the bed and evaporator and the mass flow rates of all components comprising the chiller. The optimum values increased the COP from 0.35 to 0.4, while the cooling capacity was slightly changed. The COP is 95% of a Carnot cycle working at hot water temperatures as low as 60 °C, and 90% at hot water temperatures as high as 90 °C. It was found that the simulation model results for the two-stage air-cooled chiller agreed well with the experimental data in terms of cooling capacity (6.7 kW for the model against 6.14 kW for the experimental result at 30 °C cooling water temperature). The model optimized the adsorption/desorption time, switching time and heat recovery time to maximize both cooling capacity and COP. Moreover, the model is used to study the effect of activated carbon mass, size of beds and mass flow rates of cooling, heating, chiller and condenser on both cooling capacity and COP.

A review on thermal performance enhancement of green cooling system using different adsorbent/refrigerant pairs

Due to the ever-increasing cooling demand, alternative refrigeration is being explored for the last few decades that are less energy-intensive and can utilize ozoenvironmental friendly working fluid. Vapor adsorption refrigeration is one of the most promising alternatives among all heat-driven refrigeration systems. One of the most important requirements in an adsorption-based cooling system is to enhance the adsorption uptake capacity of the adsorbent materials for their impactful, effective, and economical operation. However, there are several working pairs explored during the recent decades but none of them could be suitable as an ideal one, for all the operating conditions. In this article, the various characteristics of different adsorbents including the highly porous activated carbons derived from waste biomass, the composites, and compounds developed, are thoroughly reviewed. Further, the synthesization, the optimal assortment, regeneration, coatings on adsorber, and commercial application of novel adsorbents including the advanced adsorption reactors and the current scenario of industrial adsorption chillers are discussed in detail. Finally, the impact of operating parameters, such as adsorbent-adsorbate mass ratio, desorption pressure, operating temperatures, and adsorption/desorption cycle time on the specific cooling power, coefficient of performance, and the chiller efficiency are summarized.

Efficient modeling of adsorption chillers: Avoiding discretization by operator splitting

Reliable and computationally efficient models are crucial to improve the performance of adsorption chillers. However, modeling of adsorption chillers is challenging due to the intrinsic process dynamics. Currently, adsorption chillers are most often represented by 1-d, lumped-parameter models that use lumped models for all components but resolve the heat exchangers in one spatial dimension. Still, accurate simulations require fine discretization leading to poor computational efficiency. To increase computational efficiency, here, an alternative modeling approach is proposed that avoids discretization by applying operator splitting.The benefits of the proposed modeling approach are demonstrated in two real-world case studies. First, the resulting adsorption chiller model is calibrated and validated with experimental data of a lab-scale one-bed adsorption chiller: The proposed model retains the accuracy of a state-of-the-art model while increasing computational efficiency by up to 70%. Second, the proposed model is applied to a commercial two-bed adsorption chiller with excellent accuracy. Finally, the validity of model is tested by varying the ratio between the overall heat transfer coefficient and the heat capacity rate of the fluid in the heat exchangers. The proposed model is shown to be well suited for the conditions present in most adsorption chillers.

Towards Energy-Positive Buildings through a Quality-Matched Energy Flow Strategy

Current strategies for net-zero buildings favor envelopes with minimized aperture ratios and limiting of solar gains through reduced glazing transmittance and emissivity. This load-reduction approach precludes strategies that maximize on-site collection of solar energy, which could increase opportunities for net-zero electricity projects. To better leverage solar resources, a whole-building strategy is proposed, referred to as “Quality-Matched Energy Flows” (or Q-MEF): capturing, transforming, buffering, and transferring irradiance on a building’s envelope—and energy derived from it—into distributed end-uses. A mid-scale commercial building was modeled in three climates with a novel Building-Integrated, Transparent, Concentrating Photovoltaic and Thermal fenestration technology (BITCoPT), thermal storage and circulation at three temperature ranges, adsorption chillers, and auxiliary heat pumps. BITCoPT generated electricity and collected thermal energy at high efficiencies while transmitting diffuse light and mitigating excess gains and illuminance. The balance of systems satisfied cooling and heating demands. Relative to baselines with similar glazing ratios, net electricity use decreased 71% in a continental climate and 100% or more in hot-arid and subtropical-moderate climates. Total EUI decreased 35%, 83%, and 52%, and peak purchased electrical demands decreased up to 6%, 32%, and 20%, respectively (with no provisions for on-site electrical storage). Decreases in utility services costs were also noted. These results suggest that with further development of electrification the Q-MEF strategy could contribute to energy-positive behavior for projects with similar typology and climate profiles.

Multi-stack coupled energy management strategy of a PEMFC based-CCHP system applied to data centers

Aiming at the power fluctuation and mismatch of the combined cooling, heating, and power (CCHP) system based on proton exchange membrane fuel cells (PEMFCs) and adsorption chiller, this study proposes a multi-stack coupled power supply strategy. The PEMFC stacks are divided into types Ⅰ, Ⅱ, and Ⅲ to meet the electric load and cooling load of the data center, and the heat requirements of the system. Meanwhile, economic analysis is conducted on the single-stack energy supply strategy and the multi-stack coupled energy supply strategy. The results show that with the multi-stack coupling power supply strategy, the cooling power and electric power almost completely match the load of the data center, without power fluctuations and overshoot. By smoothing the PID control results of the current of the stacks-Ⅲ, the heating power fluctuation is significantly reduced, and the maximum overshoot does not exceed 0.5 kW. Therefore, the strategy is conducive to the stable operation of the PEMFC stack and improves the lifetime of the system. Considering investment costs, maintenance costs, hydrogen costs, and electricity benefits, the multi-stack coupled energy supply strategy can save about 6.1 × 105 $ per year. In summary, the multi-stack coupled energy supply strategy has advantages in system lifetime, operational stability, and economy.

Flexible load regulation method for a residential energy supply system based on proton exchange membrane fuel cell

To increase the use of renewable energy sources and reduce the consumption of energy and environmental pollution, a flexible load regulation method is proposed for a hybrid residential combined cooling, heating, and power system based on fuel cells and adsorption chillers. The combined cooling, heating, and power system consisted of a proton exchange membrane fuel cell stack, an adsorption refrigerator, a thermal storage tank, a wall-hanging boiler, and related accessories. A system model was established for a typical Shanghai household and a 4E (energy, exergy, environment and economy) analysis evaluation method was used to evaluate the performance of the system during winter and summer. The energy savings and CO2 emission reduction rates of the system with and without regulation were compared. The results indicated that energy and exergy efficiencies can be improved by using flexible load regulation. The energy efficiencies of the combined cooling, heating, and power system with regulation in winter and summer were 89.21% and 73.26%, respectively, and the exergy efficiencies were 58.04% and 55.47%, respectively. When compared with the traditional system, the CO2 emission reductions in the combined cooling, heating, and power system with flexible load regulation in winter and summer reached as high as 67.26% and 67.43%, respectively. Therefore, the environmental benefits of the proposed system can be significant. If the hydrogen price can drop below 1.557 $/kg and the costs of the proton exchange membrane fuel cell and adsorption chiller can be reduced, the application of the combined cooling, heating, and power system will become economically viable.

Evaluation and Design of Large-Scale Solar Adsorption Cooling Systems Based on Energetic, Economic and Environmental Performance

In hot and dry regions such as the Gulf Cooperation Council (GCC) countries, the cooling demand is often responsible for more than 70% of electricity consumption, which places a massive strain on the electricity grid and leads to significant emissions. Solar thermal driven Silica-Gel/Water adsorption chillers, used for space cooling, could provide low carbon emission cooling and reduce the reliance on grid electricity. However, a meticulous design is required to make this both economically and environmentally beneficial. This paper aims to evaluate the solar thermal adsorption chiller performance based on large-scale cooling demand through a TRNSYS simulation for 1 year of operation. The proposed system consists of two main parts: first, the solar loop with evacuated tube solar collectors; and second, the adsorption cooling system with a silica-gel/water adsorption chiller. A neighbourhood of 80 typical 197 m2 villas in Riyadh, the capital city of the Kingdom of Saudi Arabia (KSA), was taken as a case study. The solar adsorption cycle’s performance has been compared to the conventional vapour compression cycle in terms of energy, economic and environmental performance. In addition, a parametric study has been performed for the main design parameters. Results reveal that the system can reach a solar fraction of 96% with solar collector area of 5500 m2 and a storage tank volume between 350 and 400 m3. Furthermore, the annual energy cost can be reduced by 74% for the solar adsorption system compared to the conventional vapour compression cycle. Meanwhile, the CO2 saving percentage for the solar adsorption cycle was approximately 75% compared to the conventional vapour compression cycle. Carefully designed solar thermal cooling systems can reduce greenhouse gas emissions while covering a large scale of cooling demands. This can reduce the strain on the electricity grid as well as greenhouse gas emissions.

Energy and exergetic analysis of applying solar cascade utilization to an artificial photosynthesis energy supply system

Although artificial photosynthesis can produce hydrocarbon fuels and reduce carbon emissions, current implementations cannot optimally utilize the solar spectrum and thus are inefficient. This research proposes a new hybrid energy system, which begins by applying the photovoltaic/thermal panel to simultaneously generate higher-grade electricity and lower-grade heat. Then, the electricity is supplied to the carbon dioxide reduction reactor, and the heat is supplied to carbon capture by adsorption and optionally the absorption chiller. By coupling the carbon capture and reduction reaction via the photovoltaic/thermal panel, efficient cascade utilization to generate solar fuels from a single solar energy source is achieved. The energy and exergy models that couple the individual devices are developed and the effects of photovoltaic conversion efficiency and the distribution of heat between the carbon capture by adsorption and absorption chiller are examined. Results show that the optimal power/heat ratio by the photovoltaic/thermal system to gain a proper mass balance characteristic is above 1.5 to yield 3.5 kg/m2 of methanol at 10 solar concentrations. Furthermore, carbon capture from the animal farm can contribute an additional 5% exergy efficiency over atmospheric air. Overall, maximizing the photovoltaic electrical efficiency is key to maximizing the system’s energy and exergy efficiencies.

Experimental study of 3D – structured adsorbent composites with improved heat and mass transfer for adsorption heat pumps

• Experimental material design of adsorbent composites for adsorption heat pumps. • 3D-structured adsorbent composites with enhanced heat and mass transfer. • Transient experiments in laboratory scale adsorption chiller. • Performance improvement of adsorption chiller by more than 80%. The optimal balance of heat transfer, mass transfer, and adsorption capacity is critical to enhancing the performance of adsorption heat pumps. Here, 3D-structuring of adsorbent composites is used aiming to reduce heat and mass transfer resistance to improve the performance of adsorption heat pumps. The composites are produced in a laboratory hot press by consolidating an activated carbon and binder-based suspension. By introducing percolating, thermally conductive aluminum ribs, as well as mass transfer channels into the composites, heat and mass transfer kinetic could be intensified without losing volumetric adsorption capacity to a high extend. Adsorbent composites with different structuring were dynamically investigated in a gram-scale laboratory adsorption chiller by measuring mass fluxes exchanged within an adsorption cooling cycle. For the application in an adsorption chiller, performance increases by 5% after introducing of mass transfer channels, by 42% on addition of 3D-printed aluminum ribs, and by 85% by applying both, mass transfer channels as well as 3D-printed ribs in the composites compared to non-structured composites.

A novel type of PEMFC-based CCHP system with independent control of refrigeration and dehumidification

• A PEMFC-based CCHP system with dehumidification is proposed. • The effects of operating parameters on the system performance are studied. • Refrigeration and dehumidification are controlled through the hot water proportion. • The system meets the needs of electricity, heating, cooling and dehumidification. The traditional combined cooling, heating and power (CCHP) system can only provide cooling power, heating power and electricity. However, when the CCHP system is used in places with high humidity requirements such as data centers, it cannot meet the humidity control requirements. Based on this, this study proposes a CCHP system with independent control of refrigeration and dehumidification based on a PEMFC. The system model is developed by MATLAB/Simulink, and its performance and efficiency are comparatively analyzed. The results show that the current density and hot water distribution ratio are critical to the performance of the system. Meanwhile, the mass flow rate of the cooling water and chilled water of the adsorption chiller and the parameters of the process air also have an impact on the performance of the system. When the mass flow rates of cooling water and chilled water increase from 0.2 kg·s −1 to 0.8 kg·s −1 , the cooling power of the system increases from 5.3 kW and 5.12 kW to 6.52 kW and 6.64 kW, respectively. Moreover, the addition of the dehumidification system reduces the cooling power by 1.28 kW but removes the latent heat of the process air by about 1.84 kW.