Mass Ratio Of Adsorbent Research Articles

Sorption enhanced DME synthesis by one-step CO2 hydrogenation

DME synthesis by direct CO2 hydrogenation was studied on physical mixture of commercial CuZnO/Al2O3 (CZA) and in-house synthesized PTA (phosphotungstic acid)/γ-Al2O3 catalysts. Effects of PTA loading (0–50 % by mass) and relative amounts of the catalysts on CO2 conversion and DME yield were investigated. The process was intensified through integration of in-situ steam separation by Zeolite 3A (Z3A) adsorbent mixed with the catalysts. Experiments were run at 498 K, 30 bar, H2:CO2=3:1 and GHSV=1750 h−1 (based on CZA catalyst). Optimum PTA loading and CZA:PTA/γ-Al2O3 mass ratio were 30 % and 1:2, respectively, that gave ∼21 % CO2 conversion and 6.3 % DME yield. These values remained below the respective thermodynamic limits (28.5 % and 21 %), which were exceeded upon adsorbent integration. Catalytic performance depended strongly on adsorbent quantity studied at the catalyst (CZA+PTA/γ-Al2O3):adsorbent mass ratio range of 1:0.33–4. Catalysts and the adsorbent remained stable during the pressure swing driven adsorption-regeneration cycles. Sorption assistance at catalyst:adsorbent ratio=1:4 increased catalyst productivity from 5.5×10−3 to 2×10−2 kgDME h−1 kgcat−1. The latter value was comparable to those of the sorption enhanced CO2+CO hydrogenation systems due to the PTA-based dehydration catalyst with strong acidic features and was promising when the strong thermodynamic limitations of CO2-DME conversion was considered.

Potential assessment of biomass-based single-stage adsorption systems for refrigeration, cooling, and heat-pumping applications

ABSTRACT This article presents the performance estimation of a single-stage vapor adsorption system employing various carbon-based adsorbents with ethanol refrigerant, coupled with a small-scale biomass-based heating unit for space cooling, refrigeration, and heat-pumping applications. A detailed parametric investigation highlights the effects of operating temperatures, and heat exchanger to adsorbent mass ratio on specific cooling energy (SCE), coefficient of performance (COP), uptake efficiency (ηu), and mass of adsorbent to combustion fuel (mad/mcf) to identify the suitable adsorbent and sorption bed designs for each application. The numerical findings reveal that the flat-finned tube (FFT) adsorber outperforms traditional-finned tube (TFT) and tube & shell-type (T&S) adsorbers, achieving 19% and 30% higher COP, respectively, with biomass carbon-ethanol pair. The H2-treated Maxsorb-III shows the greatest optimal cooling COP (0.73), followed by the biomass-carbon (0.72) for refrigeration and space cooling. For heat pumping applications, biomass carbon-ethanol achieves the highest heat pumping COP (1.84) at a desorption temperature of 90°C, surpassing H2-treated Maxsorb-III. Further, the biomass-derived activated carbon requires the lowest amount of adsorbent per unit mass of combustion fuel in the biomass heating unit. The present thermodynamic analysis is a precursor for optimization of the potential heat-exchanger geometries and operating parameters, with the high-performance carbon adsorbents.

Matrix solid-phase dispersion combined with micro-fractionation bioactivity evaluation screening polymethoxylated flavones from Citrus peels.

Polymethoxyflavones were a unique class of natural and safe flavonoids containing two or more methoxy groups, which were also the most abundant edible part in Citrus peel. The optimum condition in the process of selective extraction of polymethoxylated flavones from Citrus peel by matrix solid-phase dispersion (MSPD) was as follows: SBA-15 as adsorbent, ethyl acetate as eluent, the mass ratio of adsorbent to sample 1:1, and the mixture of sample and adsorbent was ground for 3min. Twelve antioxidants were successfully screened by micro-fractionation bioactivity evaluation assay, in which four of them were flavonoid glycosides, seven of them were polymethoxylated flavones, and one was phenylpropanoid. 1-sinapoly-β-D-glucopyranoside (1) was reported for the first time in Citrus peel. And antioxidant capacity of 1-sinapoly-β-D-glucopyranoside, 5, 7, 8, 3', 4', 5'-hexamethoxyflavone (6), hexamethoxyflavone (11), and 5, 6, 7, 4'-tetramethoxyflavone (7) were reported for the first time. Nobiletin (compound 8), 3, 5, 6, 7, 8, 3', 4'-heptamethoxyflavone (9) and tangeretin (10) were isolated and purified by countercurrent chromatography combined with preparative liquid chromatography. Antioxidant activity evaluation indicated that the three isolated polymethoxylated flavones owned similar antioxidant activity. This study indicated that MSPD combined with micro-fractionation bioactive evaluation was efficient in screening bioactive compounds for rapid extraction and effective pinpointing bioactive substances in natural products.

Kinetics, Equilibrium and Thermodynamic Studies on Removal of Oleic Acid from Sunflower Oil onto Amberlyst A21

Amberlyst A21 was used for the oleic acid adsorption from sunflower oil (SFO). The impacts of parameters such as contact time, temperature, and mass ratio of adsorbent on oleic acid adsorption were studied. The characterization of Amberlyst A21 before and after adsorption was performed by using Fourier transform infrared spectrometer (FTIR) and scanning electron microscope (SEM). The adsorption reached equilibrium 480 minutes later. The increase in temperature and the amount of adsorbent caused an increase in the amount of adsorbed oleic acid. The adsorption kinetics, isotherms, and thermodynamics were studied. The pseudo-first order kinetics well described the adsorption for all studied temperatures. The Langmuir, Freundlich, and Dubinin−Radushkevich isotherms and thermodynamic analysis were investigated at equilibrium. The suitability of the Langmuir and Freundlich isotherms indicated that the adsorption takes place under monolayer and heterogeneous surfaces. Thermodynamical results showed that adsorption occurs spontaneously and endothermic.

The Effectiveness of Blood Clam Shell (Anadara granosa) as an Adsorbent to Improve Peat Water Quality

Research has been carried out to determine the effectiveness of blood clam (Anadara granosa) shell adsorbents in improving the quality of peat water. Blood clam shells were mashed with variations in particle size of 8 mesh, 50 mesh and 150 mesh, then an adsorption process was carried out with a mass ratio of adsorbent and peat water of 1:10. The physical and chemical parameters tested in this study included turbidity, color, Total Dissolved Solid (TDS), and pH. Based on the test results with a contact time of 12 hours, peat water levels increased for all parameters along with increasing particle size. Meanwhile, within 7 days of contact time, the results of the peat water test experienced a decrease in levels for all parameters along with increasing particle size and was a good optimum contact time in the adsorption process. The results obtained show that for the parameters of turbidity, Total Dissolvesd Solid (TDS), and pH have met the standard set by the Minister of Health of the Republic of Indonesia No. 32 of 2017, only the color parameter does not meet the standard in improving the quality of peat water.

Fly ash and TiO2 modified fly ash as adsorbing materials for removal of Cd(II) and Pb(II) from aqueous solutions

The FA and MFA had been sued to adsorb heavy metals on their surface in this work. For this purpose, fly ash alone is efficient for adsorption, but its efficiency increases when modified with TiO2. TiO2 enhanced the adsorption site of the FA. The study of the surface morphology of FA and MFA by SEM and XRD provides information about their morphology and crystallinity, which is enhanced by modification with TiO2. The crystallinity calculated by Debye-Scherrer's equation was 49.36% for FA, which increased to 79.70%, modifying it with TiO2. The BET analysis reveals that the adsorbent surface area increases after treatment from SBET = 10.79 m2 g−1 (FA) to SBET = 30.59 m2 g−1 (MFA). The adsorption parameters to define the adsorption, such as contact time, temperature, adsorbate concentration, and the adsorbent mass ratio, have been optimized. The TEM analysis revealed that the mean diameter of FA and MFA was 19.45 and 57.71 nm, respectively. The percentage removal of Cd(II) onto FA and MFA was found to be 78.10% and 94.30% and of Pb(II) onto FA and MFA was found to be 75% and 93.10%, respectively at 308 K. The adsorption capacity, qm of Cd(II) onto FA and MFA was found to be 59.20 and 68.80 mg/g, and of Pb(II) onto FA and MFA was found to be 75.30 and 62.70 mg/g, respectively at 308 K. The experimental data had been applied to various adsorption and kinetic models for both FA and MFA, and the order of the best-fitted model was Temkin > Langmuir > Freundlich > Dubinin-Radushkevich isotherm for the adsorption model and pseudo-second-order >pseudo-first-order > intraparticle diffusion for kinetic models.

A comparative study to critically assess the designing criteria for selecting an optimal adsorption heat exchanger in cooling applications

• Adsorption heat exchanger (AdHEx) type, fin dimension and body material are studied. • Different design criteria for comparing AdHExs are employed. • Rectangular finned-flat tube and annular finned-tube AdHExs are compared. • The AdHEx superiority in terms of chiller performance and compactness is examined. • A powerful numerical tool for designing the most efficient AdHExs is provided. In an adsorption cooling system (ACS), it is essential to design the most efficient AdHEx in terms of compactness, heaviness, and ACS performance parameters. For this purpose, the coupled effects of structural type, body material, and fin geometrical specifications of its adsorber heat exchanger (AdHEx) need to be investigated. Therefore, a three-dimensional distributed-parameter model is developed and validated to conduct a comprehensive parametric study on finned flat-tube and annular finned-tube AdHExs. In this regard, two different design criteria of AdHEx heat transfer area to adsorbent mass ratio (S/m ads ) and inter-particle mass transfer resistance are adopted as common bases of the comparisons. The results indicate that for any given bed geometrical configurations, there exists a certain threshold value for the thermal conductivity of AdHEx body material. For values greater than it, the specific cooling power (SCP) and volumetric cooling power (VCP) are approximately invariant. In contrast, the coefficient of performance (COP) is mainly influenced by the volumetric heat capacity (VHC) of the AdHEx body material such that it steadily decreases by increasing VHC. Independent of body material, utilizing the smallest fin dimensions for an AdHEx leads to the highest SCPs at the cost of lowering COP, dramatically. However, maximizing VCP is more complicated because the variations of VCP with fin height show entirely distinct behaviors for different body materials and AdHEx type. It is found that estimating the superiority of an AdHEx over another is beyond the ability of common rules of thumb because of complicated transport phenomena within the adsorber beds. In light of this, the approach and results of this study properly bridge the gap between the scientific and practical aspects of designing an AdHEx based on application constraints.

Numerical analysis of heat pipe-assisted finned adsorber with FAM-Z02/water pair for vehicle air conditioning

• Heat pipe-assisted finned adsorber for vehicle air conditioning. • Heat and mass transport between the heat pipe, fins and adsorbent particles. • Parametric study on SCP, COP and AAMR of FAM-Z02/water adsorber bed. • Optimal bed configuration considering number of fins and minimized weight. Adsorption cooling system (ACS) driven by engine waste heat is an attractive alternative to vehicle air conditioning (A/C) system. To find a compact and efficient solution for onboard application, a heat pipe-assisted finned adsorber unit tube (AUT) packed with FAM-Z02 adsorbent was studied numerically. Based on the integrated physical prototype, a three-dimensional numerical model was developed to investigate adsorption/desorption characteristics combined with experimentally validated heat pipe model and adsorption isotherm model. Moreover, specific cooling power (SCP), coefficient of performance (COP) and adsorber bed to adsorbent mass ratio (AAMR) were quantified to evaluate cooling capacity and system performance. It is found that, compared with adsorber without heat pipe, a 15.3% increment of SCP and 19.1% increment of COP can be achieved in the FAM-Z02/water based adsorber due to the contribution of heat pipe, and the AUT has an optimal SCP of 64.19 W/kg at the cycle time of 8510 s. The smaller adsorbent particle size leads to more refrigerant adsorbing/desorbing under the same cycle time, and FAM-Z02 with 0.1 mm diameter provides optimal SCP of 66.7 W/kg for ACS due to smaller particles possess less intra-particle mass transfer resistance. When the cool source temperature and heat source temperature are 300 K and 365 K respectively, higher SCP can be achieved due to the larger cyclic water uptake. Heat pipe-assisted finned adsorber offers a viable solution for coolant’s application in onboard ACS, and a 6-fin adsorber packed with 0.1 mm-diameter FAM-Z02 is considered optimal under lower adsorption temperature and higher desorption temperature.

D-optimal experimental designs for precise parameter estimation of adsorption equilibrium models: initial concentration and solvent volume to adsorbent mass ratio as independent variables

D-optimal experimental designs for precise parameter estimation of adsorption equilibrium models: initial concentration and solvent volume to adsorbent mass ratio as independent variables

Pemanfaatan cangkang telur dan sekam padi sebagai bioadsorben metilen biru pada limbah tekstil

The textile industry in Indonesia has increased since the 1980s. From the non-oil and gas sector, the textile industry is the government's largest source of income. In addition to its impressive growth, about 10-15% of the used textile dyestuff is wasted at the dyeing process can exceed the maximum Chemical Oxygen Demand level of 150 mg/L. Synthetic dyes contain carcinogenic ingredients that can harm the environment and aquatic biota. The alternative for handling the dye waste is the adsorption method using bio adsorbent from a mixture of chicken eggshells and rice husk ash. Both have the potential to be used as adsorbents because they have an active site, abundant amounts, and are economical. This study was to determine the effect of the process variables of the adsorbent mass ratio, contact time, and pH on the adsorption capacity of methylene blue using a mixture of eggshells and rice husk ash with the UV-Vis Spectrophotometer analysis method. The results showed that the optimal conditions for the adsorption of 20 ppm methylene blue were 0.2:0.8 gram of adsorbent ratio, 80 minutes, and pH of 3. The adsorption capacity obtained was 98.817%, reduced the methylene blue concentration to 0.237 ppm.

Studi Model Isoterm Adsorpsi Kristal Violet oleh Biosorben Kulit Ubi Kayu (Manihot esculenta)

Crystal violet is a dye that has many uses, but its waste can be harmful to humans and the environment. Adsorption is the most useful method for removing crystal violet waste compared to other separation methods because of its efficiency and viability. Cassava peel is a material that has potential to be an adsorbent. Cassava peel is suitable as an adsorbent because of its high cellulose, hemicellulose, and lignin content. In carrying out adsorption, getting the most appropriate isotherm model is important for predicting the adsorption parameters and the adsorbent system. This study aims to obtain an adsorption isotherm model that is the most suitable for the adsorption of crystal violet by cassava peel biosorbent with high accuracy and to obtain a combined model of the adsorption isotherm model that is the most suitable with the mass balance equation to predict removal efficiency. This research was conducted using secondary data using MATLAB as a supporting tool to perform a non-linear regression and Newton-Raphson iteration. In this research, we conclude that Sips model is the most suitable model with qms = 374,3 mg/g and 0,5933 site heterogeneity. For predict adsorbent mass ratio: adsorbate volume minimum ratio but removal efficiency stay at ≥ 90%, we obtain a correlation factor: m/V = -1.10-11Co4 + 2.10-8Co3 – 2.10-5Co2 + 0.015Co + 1.2686.

TiO2 grafted activated carbon elaboration by milling: Composition effect on sorption and photocatalytic properties

Activated-Carbon/Titania composites (AC/TiO2) is a relevant option to gather the dual adsorption/photodegradation property within a single material. This work aimed to investigate the composition influence on the adsorption and photodegradation properties of AC/TiO2 composites against caffeine. TiO2 grafted AC powders covering the whole composition scale were synthesized by a one-step mechanical milling process. This original simple elaboration route led to the obtention of powders which particles size and composition were homogeneous and well controlled. When the adsorbent mass ratio varied in the range 0.01−0.75, the adsorption properties, i.e. apparent kinetic and maximum adsorption capacity of the composites increased respectively by 1 and 2-log. At the opposite, the photo-oxidation rate decreased significantly when the adsorbent ratio increased. The simple elaboration route explored produces flexible AC/TiO2 composites with adjustable properties that can easily be managed to meet the requirements of different target applications.

Effective adsorption of zinc on magnetic nanocomposite of Fe3O4/zeolite/cellulose nanofibers: kinetic, equilibrium, and thermodynamic study.

In this paper, the adsorption behavior of zinc onto magnetic zeolite/cellulose nanofibers (MZNF) was studied. The prepared adsorbent was characterized by SEM, FTIR, and VSM analyses. The mass ratio of adsorbent in composite, pH, contact time, adsorbent dosage, initial Zn+2 concentration, temperature, and agitation speed were investigated in batch experiments. The results showed that zeolite played an important role in the prepared nanocomposite due to its great surface area. pH7 exhibited the highest Zn+2 removal efficiency. Rapid adsorption at the first 30min of the reaction is one of the advantages of the prepared adsorbents. Moreover, increase at temperature led to higher efficiency and maximum efficiency was attained at 30°C. Under optimum conditions, MZNF showed removal efficiency of 96% and maximum adsorption capacity of 9.45mg/g. The presence of the competing ions did not reduce the efficiency of the process and adsorption efficiency was higher than 93%. The calculated RSD of 1.42% exhibits the suitability of the process. Equilibrium data were examined by various isotherms and kinetics equations. It was concluded that Pseudo second-order model and Langmuir models described the adsorption process well. Based on these results, MZNF obtained in this work can be served as a promising candidate for Zn+2 removal in wastewater.

Uranium Removal from Wastewater Using Mg(OH)2-Impregnated Activated Carbon

Uranium wastewater treatment has been performed by adsorption method using Mg(OH)2-impregnated activated carbon. Research purposes are to determine (i) uptake capacity of the adsorption isotherm of uranium in Mg(OH)2-impregnated activated carbon, (ii) mathematical correlation of uranium (VI) adsorption rate, and (iii) effect of the impregnation ratio of adsorbent to uranium removal efficiency. Adsorbent was synthesized through several stages, i.e., pyrolysis of coconut shell (400 °C), chemical activation using NaOH, and impregnation process using varied solutions of MgCl2 (600 °C). The materials were characterized comprehensively using FTIR, BET, XRF, and XRD. The parameters studied in this research were adsorption temperature (T), average particle diameter of adsorbent (d), mass ratio of adsorbent to wastewater solution (r), and impregnation ratio of Mg(OH)2/activated carbon. The results shown that equilibrium data are well fitted with the Langmuir isotherm model with the maximum adsorption capacity about 85 mg/g at 303 K and dimensionless constant separation factor (RL) value about 0.7. The adsorption rate was increased by increasing the adsorption temperature, mass ratio of adsorbent to wastewater solution, and the decrease of particle diameter of adsorbent with mathematical equation of the uranium (VI) adsorption rate as: $$ \ln \frac{C}{C_0}=-\left[85032.11\exp \left(-\frac{41981.03}{RT}\right){d}^{-0.2176}{r}^{0.1925}\right]{t}^2 $$ In addition, the results also shown that increasing the impregnation ratio from 0.3 to 1.0 can increase the uranium removal efficiency up to 67.3%.

D-optimal experimental designs for precise parameter estimation of adsorption equilibrium models

D-optimal experimental designs were obtained for Langmuir, Freundlich, Jovanovich, Sips, Redlich-Peterson and BET isotherms using two different approaches. In the first one, it is assumed that liquid solution equilibrium concentration is the independent system variable and solid equilibrium concentration is the dependent variable, which is the usual procedure for parameter estimation of adsorption isotherm models. In the second approach, initial liquid solution concentration, liquid solution volume and adsorbent mass are the independent variables and liquid solution equilibrium concentration is the dependent variable, which is closer to what actually occurs in adsorption experiments. In both cases, one of the designed conditions is an experiment using the maximum concentration value in the experimental range, while other conditions are functions of one or more isotherm parameter. When using equilibrium concentration as the independent variable, the linear parameter of the equilibrium model did not affect the experimental design. In this case, analytical solutions for 2-parameter equilibrium isotherm were obtained, while only numerical solutions were obtained for 3-parameter equilibrium models. When considering the initial concentration as the independent variable, with a constant liquid solution volume to adsorbent mass ratio, it was possible to observe that the experimental conditions of the optimum design depend on all model parameters, for all isotherms evaluated. Additionally, as liquid solution volume to adsorbent mass ratio increases, the experimental design obtained using the initial concentration as the independent variable approaches the one obtained when equilibrium concentration is assumed to be independent variable; therefore, this approach is just a particular case of the first one.

Combination of rice husk and coconut shell activated adsorbent to adsorb Pb(II) ionic metal and it’s analysis using solid-phase spectrophotometry (sps)

The purpose of this research was to know the effect and determine the mass comparation which most effective combination between rice husk and coconut shell activated adsorbent to adsorb Pb (II) ion using SPS method. This research used experimental method. Technique to collecting this datas of this research is carried out by several stages, which are: (1) carbonization of rice husk and coconut shell adsorbent using muffle furnace at a temperature of 350°C for an hour; (2) activation of the rice husk and coconut shell adsorbent using NaOH 1N and ZnCl2 15% activator; (3) contacting the adsorbent of rice husk and coconut shell activated adsorbent with liquid waste simulation of Pb(II) using variation comparison of rice husk and coconut shell, 1:0; 0:1; 1:1; 2:1; 1:2; (4) analysis of Pb(II) using Solid-Phase Spectrophotometry (SPS); (5) characterization of combination rice husk and coconut shell activated adsorbent using FTIR. The result of this research show that the combined effect of combination rice husk and coconut shell activated adsorbent can increase the ability of the adsorbent to absorb Pb(II) ion then the optimum adsorbent mass ratio required for absorbing 20 mL of Pb(II) ion with a concentration of 49.99 µg/L is a ratio of 2:1 with the absorption level of 97,06%Solid-Phase Spectrophotometry (SPS) is an effective method in the level of µg/L, be marked with the Limit of Detection (LOD) of 0.03 µg/L.

The synthesis of corncobs (zea mays) active charcoal and water hyacinth (eichornia crassipes) adsorbent to adsorb Pb(II) with it’s analysis using solid-phase spectrophotometry (sps)

This research aim to examine the effect of the combination between corncobs and water hyacinth to adsorb lead (II), the most effective combination have determined by compared the ratio of corncobs adsorbent and water hyacinth to the increasing adsorption of the Pb(II), prove the effectiveness of the solid-phase spectrophotometry (sps) to determine the levels of Pb(II) as the result of the corncobs active charcoal adsorption and water hyacinth in the level of µg/L. The research method used is experimental method. The data collecting technique is carried out by several stages, which are carbonization using muffle furnace at a temperature of 350°C for 1.5 hours, activation of the corncobs charcoal and water hyacinth using HCl 1M and HCl 5M activator, contacting the adsorbent of corncobs active charcoal and water hyacinth with liquid waste simulation of Pb(II) using variation of corncobns and water hyacinth, 1:0; 0:1; 1:1; 2:1; 1:2, analysis of Pb(II) using an sps, characterization of corncobs active charcoal adsorbent and water hyacinth using FTIR. Research results show that the combined effect of activated charcoal corncobs and water hyacinth can increase the ability of the adsorbent to absorb Pb(II), the optimum adsorbent mass ratio of 1:1 with the absorption level of 90.33%, SPS is an effective method to analyze the decreasing level of Pb(II) as the adsorbtion result of the corncobs active charcoal and water hyacinth in the level of µg/L, with the limit of detection (LOD) of 0.06 µg/L.

Effects of adsorbent mass and number of adsorber beds on the performance of a waste heat-driven adsorption cooling system for vehicle air conditioning applications

Waste heat-driven adsorption cooling systems (ACS) are potential replacements for vapor compression refrigeration cycles in vehicle air conditioning applications. However, the bulkiness and heavy weight of ACS are major challenges facing commercialization of these environmentally friendly systems. This study examines the effects of adsorbent mass and the number of adsorber beds on the performance of a FAM-Z02/water ACS under different operating conditions. The experimental results show that reducing the mass of FAM-Z02 from 1.9 to 0.5 kg in a one-adsorber bed ACS increases the SCP by 82% from 65.8 to 119.4 W/kg at cycle time of 20 min. However, the COP reduces by 37% because of the increase in the adsorber bed to adsorbent mass ratio. The results also show that the thermal mass of the evaporator limits the performance of the ACS, especially under short cycle times (8–20 min). A second adsorber bed is added to the one-adsorbed bed ACS test bed to generate continuous cooling in the evaporator. Comparing the performance of one- and two-adsorber bed ACS packed with 0.5 kg of FAM-Z02 particles and cycle time of 20 min shows that the SCP and COP of the two-adsorber bed ACS increase by 28% and 47%, respectively.

Impact of fin spacing on temperature distribution in adsorption cooling system for vehicle A/C applications

Effects of fin spacing on the temperature distribution in a finned tube adsorber bed are studied to decrease the temperature gradient inside the adsorber bed and minimize the adsorber bed to adsorbent mass ratio (AAMR) for vehicle air conditioning applications. Finned tube adsorber beds have shown higher specific cooling power and coefficient of performance, and low AAMR among the existing adsorber beds. A single-adsorber bed ACS with interchangeable heat exchangers is built and equipped with hermetic type T thermocouples. Two copper heat exchangers with 6.35 mm (1/4″) and 9.5 mm (3/8″) fin spacing are custom-built and packed with 2–4 mm silica gel beads. The experimental results show that by decreasing the fin spacing from 9.5 mm to 6.35 mm, the temperature difference between the fin and adsorbent reduces by 4.6 °C under the cycle time of 600 s and an adsorption to desorption time ratio (ADTR) of one. A greater reduction in the temperature gradient inside the adsorber bed with smaller fin spacing is observed for short cycle time operation, e.g. 600 s, compared to long cycle time operation, e.g. 1400 s. Finally, simultaneous comparison of the temperature gradient between the fins and AAMR against fin spacing indicates that the optimum fin spacing for a finned tube heat exchanger packed with 2–4 mm silica gel beads is about 6 mm.

Assessment of adsorber bed designs in waste-heat driven adsorption cooling systems for vehicle air conditioning and refrigeration

Abstract Adsorber bed design strongly affects the performance of waste-heat driven adsorption cooling systems (ACS) for vehicle air conditioning and refrigeration (A/C–R) applications. Adsorber beds should be specifically sized for vehicle A/C–R considering the limitations of mobile applications. However, there is no conclusive evidence on what type of adsober bed is proper for vehicle applications. To evaluate the performance of ACS, specific cooling power (SCP), adsorber bed to adsorbent mass ratio, and coefficient of performance (COP) are introduced and their order of importance are assessed. To investigate the available studies in the open literature, desired SCP of 350 W/kg dry adsorbent and adsorber bed to adsorbent mass ratio of less than one are calculated for a 1-ton-of-refrigeration, 2-adsorber bed, silica gel–water ACS. According to these criteria, previous studies are summarized into nine groups with respect to their adsober beds and consequently, finned tube adsorber bed design is selected among the existing designs. Finally, optimization of fin spacing and fin height, and enhancing thermal conductivity of adsorbent material by adding metal wool inside the finned tube adsorber bed are proposed as the practical solutions to increase heat and mass transfer rates within the adsorber bed.