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• Adsorption of R-32 and R-125 in an activated carbon fixed-bed is studied. • Breakthrough curves are performed to determine mass and heat transfer parameters. • A 4-step VSA process is evaluated for the separation of R-32 from R-125. • R-32 is obtained with 97.0 mol-% purity and 30.9% recovery. The recovery of high purity fluorinated gases from refrigerant blends is vital to promote a circular economy in the field of refrigeration and air conditioning. In this work, we evaluate the performance of a four-step Vacuum Swing Adsorption (VSA) process using activated carbon for the recovery of R-32 (difluoromethane) from a R-410A refrigerant blend: a binary mixture of R-125 (pentafluoroethane) and R-32 (y R − 32 = 0.7; y R − 125 = 0.3). Breakthrough curves were performed using dilute and bulk feed concentrations to determine mass and heat transfer parameters, which were then employed in simulations of fixed-bed adsorber dynamics. The mathematical model employed successfully predicts the experimental results of a four-step VSA cycle (feed, blowdown, purge, pressurization). The VSA performance was evaluated using process simulation. For a cycle time of 800 s (each step taking 200 s) and feed and regeneration pressures of 1.01 and 0.01 bar, respectively, R-32 is obtained with 97.0 mol-% purity and 30.9% recovery, with process productivity of 4.06 mol h −1 per kilogram of adsorbent, and energy consumption of 123.2 kJ/mol. Our results demonstrate the feasibility of using VSA processes for the recovery of R-32 from the near-azeotropic R-410A refrigerant blend. [Display omitted] [ABSTRACT FROM AUTHOR]

• Thermodynamic analysis of a two bed solar adsorption refrigeration system is presented. • Activated carbon-ethanol is the best adsorbent-adsorbate pair for the continuous operating adsorption cooling cycle. • The maximum C O P S Y of the system is 0.68 for the desorption temperature of 95 °C. • Dependency of performance parameters with desorption temperature is studied. • Isothermal adsorption is thermodynamically efficient as compared to isobaric adsorption. In this study, a thermodynamic model for analysing the performance of a two-bed solar adsorption cooling system (SAC) has been presented. It projects isothermal adsorption instead of isobaric to reduce the heat of adsorption and hence improve the performance of SAC system. An adsorption chiller of 500 W capacity operating at an evaporator temperature of 5 °C and a condenser temperature of 45 °C is selected for the present research. The proposed adsorption chiller uses activated carbon/ethanol as the working pair. The refrigeration cycle operates between an evaporator pressure of 2.01 kPa and a condenser pressure of 23.1 kPa. The input heat distribution in the bed component, followed by, assessing the effect of maximum desorption temperature on the performance of the system is also carried out. The maximum coefficient of performance of 0.68 is observed for a desorption temperature of 95 °C.The thermal performance of the system is also studied for adsorbate fraction, adsorbent bed pressure and effect of desorption temperature on various parameters. It has been found that the isothermal adsorption process increases the thermal performance of the SAC and it is estimated that coefficient of performance of the system with isothermal adsorption is 13.23% times more when compared with conventional isobaric adsorption. The study aims at providing a formidable solution to the low performance of adsorption cooling systems. [ABSTRACT FROM AUTHOR]

• A new adsorption pair maxsorb III/HFC404A has been presented. • Adsorption isotherms have been studied experimentally and theoretically. • Adsorption kinetics has been studied experimentally and theoretically. • A mathematical model for an adsorption cooling system has been conducted. This work comes as a part of a series of researches carried out by our team to study and present new materials with distinctive properties suitable for adsorption applications. As we previously studied employment of many Freons within the adsorption cooling systems, this paper expresses a study using HFC404A with activated carbon (Maxorb III). Adsorption of Maxsorb III/HFC404A pair has been estimated experimentally at different temperatures ranging from 25 to 75 °C. Dubinin-Astakhov (D-A) and Tóth equations have been fitted with the experimental data to evaluate the adsorption isotherm, while the adsorption kinetic is evaluated by linear driving force model (LDF) and Fickian diffusion (FD) equations. The maximum adsorption capacity is 2.2 kg R404A /kg activated carbon. The numerical values of the activation energy (E a) and the pre-exponential coefficient (D so) are evaluated to be 3429.27 kJ/kg and 5.35×10–13, respectively. Transient simulation modeling has been carried out to predict performance of adsorption cooling system under different operating temperatures of Maxsorb III/HFC404A. Optimum recorded coefficient for performance and specific cooling power is 0.23 and 275 W/kg, respectively. [ABSTRACT FROM AUTHOR]

• Four different configurations of adsorption cooling cycles are studied for improved performance for subcritical and transcritical cycles. • Detailed thermodynamic analysis is carried out for 5 different adsorbent materials for all the configurations. • Effect of various parameters are studied on system performance. • Out of all the adsorbents used, Maxsorb III showed better system performance. • Various co-relations have been developed for various intermediate temperatures and COP. In the present investigation, thermodynamic analysis of four different adsorption cooling cycles; basic, internal heat recovery, mass recovery, and heat & mass recovery cycles are carried out employing CO 2 as the refrigerant. The said investigation is done for five different adsorbent materials i.e. a highly microporous activated carbon (Maxsorb III), Maxsorb III based composite, Activated carbon fibre (ACF) A-20, BPL activated carbon (AC), and Norit AC. The study stretches the analysis from subcritical to supercritical zone for evaporator temperature ranging from −5 °C to 15 °C. For subcritical cycle, generator and condenser temperatures are varied between 65 °C to 91 °C and 20 °C to 30 °C, and for transcritical cycle, generator and gas cooler exit temperatures are varied from 90 °C to 120 °C and 35 °C to 40 °C, respectively. The maximum COP and specific cooling effect (SCE) achieved by incorporating both heat and mass recovery to the basic cycle are 0.305 and 105 kJ/kg, respectively. The improvement in COP and 2nd law efficiency of the same cycle w.r.t. other cycles are in the range of 7% to 84% and 38% to 77%, respectively for subcritical cycles. Similarly, for transcritical cycles, improvements in COPs of HMRC are in range of 17% to 75%. Analysis showed better system performance for Maxsorb III and it's composite as compared to other adsorbents. Various regression equations are developed to predict the different intermediate temperatures and COP for the mentioned modified subcritical and transcritical cycles. [ABSTRACT FROM AUTHOR]

• AC-GNPs based composites are prepared and measured for thermophysical properties. • CO 2 adsorption isotherms of synthesized composites are investigated. • Modified D-A and Tóth models are used to correlate the experimental CO 2 uptake data. • Thermodynamic analysis of composite/CO 2 based adsorption cooling cycle is performed. • The theoretical maximum SCE and COP are estimated and compared. Adsorption cooling system using composite adsorbent and high energy density adsorbate (CO 2) provides a significant advantage to reduce the system geometry. This study presents the adsorption characteristics of CO 2 onto synthesized composites employing graphene nanoplatelets (GNPs) and activated carbon (AC). The influence of GNPs in the composite is investigated in terms of porous properties, thermal conductivity, and CO 2 adsorption capacity. The composite 3 (50 wt% AC and 40 wt% H-25) achieves the highest thermal conductivity enhancement which is 23.5 times higher than parent AC powder. The CO 2 adsorption uptakes onto different composites are measured gravimetrically at adsorption temperatures 20–70 °C. The measured data are fitted with modified D-A and Tóth models. The specific cooling effect (SCE) and coefficient of performance (COP) are estimated for various driving heat source temperatures and two evaporation temperatures of 5 and 10 °C with a fixed adsorption/condenser temperature of 30 °C. AC-GNPs based composites are found suitable for developing compact adsorption cooling systems. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Highlights • Quantifies CO 2 adsorption capacity of nitrogen doped graphene oxide. • Adsoprtion characteristics estimated using volumetric method with 5% uncertainty. • Higher SSA of nitrogen doped rGO enhances Specific Adsorbance. Abstract The research reported here presents the results of an experimental investigation of the adsorption performance of combinations of activated carbon and different forms of graphene oxide, and activated carbon and reduced grapheme oxide containing nitrogen, in mixtures. The materials can be used as adsorbent materials for CO 2 , with application potential in CO 2 capture and storage systems. The specific adsorbance was found to increase with the addition of graphene oxides to activated carbon. It was also found that it increases in the sequence: expanded graphene oxide, exfoliated graphene oxide, reduced graphene oxide and reduced graphene oxide containing nitrogen. Adsorption isotherms and isobars were developed and the results compared with pure activated carbon, for samples with weight percentages of expanded graphene oxide, exfoliated graphene oxide, reduced graphene oxide and reduced graphene oxide containing nitrogen, up to 25%, 32.5%, 42% and 50%, respectively. [ABSTRACT FROM AUTHOR]

Abstract: An adsorption cooling system has been designed and built employing granular activated carbon (GAC)–R134a as adsorbent–refrigerant pair. The performance of the system has been determined using a cycle simulation computer program written in Fortran. The performance of the system has been determined varying driving heat source inlet temperatures and delivered evaporator temperatures. The maximum driving heat source temperature is kept below 100 °C to utilize solar thermal energy or waste heat sources. The results showed good agreement between the theoretical and experimental data. The maximum theoretical coefficient of performance (COP) is obtained as 0.35. The experimental specific cooling energy (SCE) is reached up to 70 kJ kg−1 whereas the maximum theoretical SCE of the system is 83 kJ kg−1. The pressurized-bed adsorption cooling system can effectively utilize low grade waste heat of temperature below 100 °C. [Copyright &y& Elsevier]

Abstract: Computational modelling of multiple-bed and thermal wave adsorption cycles is carried out in order to determine which method of heat recovery gives the superior trade off between coefficient of performance (COP) and power density (the power output per unit mass or volume of machine). The modelling is performed for the activated carbon-ammonia pair with a high power density plate heat exchanger type generator. It is discovered that multiple-bed cycles give a superior trade-off between COP and power density and are therefore recommended over thermal wave cycles. The principal application is considered to be a gas fired heat pump and it is found that the technology compares favourably with competing systems. [Copyright &y& Elsevier]

Abstract: The objective of this article is to improve the performance of thermally powered adsorption/cooling systems by selecting a new adsorbent/refrigerant pair. Adsorption equilibrium data of R134a onto granular activated carbon (AC) and Unitika activated carbon fiber (ACF) of type (A-20) have been measured experimentally using Rubotherm ISOSORP 2000 within evaporation temperatures range between −20 and 40 °C and adsorption temperatures range from 30 to 80 °C. Experimental data have been correlated using various popular isotherm models. The isosteric heat of adsorption of the assorted adsorbent/refrigerant pairs has also been extracted from the present experimental data. [Copyright &y& Elsevier]

Abstract: In this first part a comprehensive thermophysical characterisation of six activated carbons – based on coconut, peat and stone coal with focus on thermally driven chillers is reported. Pore and surface analysis are performed using N2 and CO2 adsorption. Furthermore the density and heat capacity of the samples is determined. Methanol adsorption measurements for evaporation between −5 °C and 35 °C and driving temperatures up to 130 °C are realized using a thermobalance and evaluated using the Dubinin–Astakhov (DA) approach. Based on the given DA equations, the possible loading lifts for typical applications like 95°-35°-7 °C are calculated. The samples show very attractive maximum loading lifts up to 0.385 g g−1. Furthermore the mass and volume specific cooling enthalpy of 244 kJ kg−1 and 126 kJ dm−3 under realistic conditions demonstrates the good performance of this working pair. [Copyright &y& Elsevier]

Abstract: Experimental runs were done to estimate the adsorption characteristics of granular activated carbon (GAC)/R134a pair. A laboratory scale test rig was designed and built to run the experiments. The adsorption capacity of the GAC was studied at different temperatures 25°C, 35°C, 45°C and 65°C. Pressure and time were recorded during the experiments. The maximum adsorption capacity was found to be 1.68kgR134a kgcarbon −1 at 25°C after 1000s. The activation energy and the exponential constant were estimated to be 9575Jmol−1 and 1.83 respectively. [Copyright &y& Elsevier]

Abstract: This paper presents the isothermal characteristics of methanol onto two specimens of activated carbons namely Maxsorb III and Tsurumi activated charcoal. Dubinin Raduskevich (D-R) equation is used to correlate the adsorption isotherms and to form the pressure–temperature–concentration diagram for both of the assorted pairs. Experimental results show that the maximum adsorption capacity of Maxsorb III/methanol pair is 1.76 times that of activated charcoal/methanol pair. Employing a time-independent mathematical model, the performance of adsorption cooling cycle using Maxsorb III/methanol and activated charcoal/methanol pairs has been studied and compared with that of three other types of carbon based adsorbent/methanol pairs. Theoretical calculations show the superiority of Maxsorb III/methanol pair for both of air-conditioning and ice-making applications. [Copyright &y& Elsevier]

Abstract: This paper presents adsorption isotherms of R-134a (HFC-134a) on highly porous pitch based activated carbon (Maxsorb III) in the temperature range of 5–70°C and pressures up to 12bar, using desorption method. The experimental data have been fitted with the Dubinin–Astakhov (D–A) isotherm equation. The adsorption isotherms of R-134a on Maxsorb III obtained from the present study are compared with the adsorption isotherm results of R-134a on similar type of adsorbents obtained by other researchers and they are found to be fairly consistent. The isosteric heat of adsorption of the assorted adsorbent–refrigerant pair has also been extracted from the present experimental data. [Copyright &y& Elsevier]

Adsorption of methylene blue from solution on unoxidized and an oxidized Algerian activated carbon with HNO3 has been studied. The change in physical and surface chemical properties, resulting from this treatment, was characterized using N2 and C6H12 adsorption, Boehm titration and temperature programmed desorption (TPD). The textural parameters obtained from N2 and C6H12 adsorption showed a considerable decrease in surface area and pore volume of the oxidized carbon with enhanced pore widening. The extent of porosity modification was found to depend on the HNO3 concentration. The Boehm titration and the CO, CO2 desorption showed that the treatment with HNO3 increased the number of oxygenated groups on the surface of the carbons. The adsorption capacity of methylene blue mainly depends on the porosity of samples and pH of the solution, i.e., the total number of acid sites. [ABSTRACT FROM AUTHOR]

Abstract: This article aims to evaluate the performances of an adsorption system driven thanks to the heat rejected by the post-combustion exhaust gases of a reformer/fuel cell system for residential air-conditioning application. Three adsorption pairs were compared: activated carbon/methanol, silica gel/water and zeolite/water. Taking into account both cooling power and sensitivity to performances of the heat rejection and recovery exchangers, it appears that zeolite 13X/water is the adsorption pair giving the best performance for this application. Nevertheless, a more detailed model would be of interest to better quantify the heat transfer impact on performance. [Copyright &y& Elsevier]

Abstract: Adsorption equilibrium uptake of ethanol onto a highly porous activated carbon based adsorbent, namely Maxsorb III, has been experimentally investigated using a thermo-gravimetric analyzer (TGA) unit over adsorption temperatures ranging from 20 to 60°C. The Dubinin–Astakhov (D–A) equation has been used to correlate the experimental data. Isosteric heat of adsorption is also estimated by using the Clausius–Clapeyron equation. Employing a thermodynamically equilibrium model, the performance of the ideal adsorption cooling cycle has also been studied and compared to that of activated carbon fiber (ACF)–ethanol pair. Experimental results show that Maxsorb III can adsorb up to 1.2kg of ethanol per kilogram of adsorbent. Theoretical calculations show that, the Maxsorb III–ethanol adsorption cycle can achieve a specific cooling effect of about 420kJkg−1 at an evaporator temperature of 7°C along with a heat source of temperature 80°C and thus the pair is recommended for solar cooling applications. [Copyright &y& Elsevier]

Abstract: This paper presents the results of an investigation on the efficacy of hybrid compression process for refrigerant HFC 134a in cooling applications. The conventional mechanical compression is supplemented by thermal compression using a string of adsorption compressors. Activated carbon is the adsorbent for the thermal compression segment. The alternatives of bottoming either mechanical or thermal compression stages are investigated. It is shown that almost 40% energy saving is realizable by carrying out a part of the compression in a thermal compressor compared to the case when the entire compression is carried out in a single-stage mechanical compressor. The hybrid compression is feasible even when low grade heat is available. Some performance indictors are defined and evaluated for various configurations. [Copyright &y& Elsevier]

This study aimed to compare the effectiveness of activated carbons, in the purification of aqueous effluents contain phenols. The activated carbons tested were prepared from Jujube shells according to different modes of activation. Their porous texture was characterized by gas adsorption and the mercury porosimetry. The influence of various parameters on the adsorption capacity was studied; the time of contact, pH, initial concentration of the phenolic aqueous solution and the temperature. The simulated adsorption isotherms were described by the Langmuir model. The ultimate capacity of adsorption reaches 476 mg/g for phenol and 344,8 mg/g for the 2-4 dichlorophenol. The kinetic adsorption was analyzed by the Lagergreen model. The capacity of adsorption depends on the porosity of the activated carbon, a pH of the solubility of the phenolic compounds. The thermodynamic parameters show that the process of adsorption is physical, exothermic and spontaneous. [ABSTRACT FROM AUTHOR]

Abstract: The performance of a solid sorption icemaker is investigated. CaCl2/activated carbon was used as compound adsorbent and ammonia was employed as adsorbate. The influence of operating conditions (cooling water temperature, mass recovery and heat pipe heat recovery, etc.) on the mass of ice, SCP (specific cooling power) and COP (coefficient of performance) was experimentally assessed. At the desorption temperature of 126°C, cooling water temperature of 22°C, ice produced temperature of −7.5°C, 40s of mass recovery and 2min of heat pipe heat recovery, the mass of ice, SCP and COP values are 17.6kg/h, 369.1W/kg and 0.2, respectively. [Copyright &y& Elsevier]

Abstract: The purpose of this paper is to identify the minimum desorption temperatures required to operate thermally driven adsorption beds of a solid sorption refrigeration system. The method is based on the evaluation of uptake efficiency of the adsorption bed and estimating there from conditions under which the compressor ceases to provide any throughput. The difference in the densities of the refrigerant between the inlet and outlet, the adsorption characteristics of the adsorbate–refrigerant pair and the void volume in the thermal compressor are the contributors to the manifestation of the desorption state. Among them, the void volume is a controllable parameter whose role is analogous to the clearance volume in a positive displacement compressor. The methodology has been tested out with three systems, namely, silica gel+water, activated carbon fiber+ethanol and activated carbon+HFC 134a systems. It is shown that waste heat at as low as 60°C can operate these systems which make them good energy conservation devices through recovery of low grade process waste heat. [Copyright &y& Elsevier]