Activated Carbon Methanol Research Articles

Experimental study of the optimal mixing ratio of metallic additives for improving the performance of the solar activated carbon-methanol adsorption refrigeration system

An activated carbon–methanol system can run on low heat (70–100°C). Methanol is dependable and works well with activated carbon because of several benefits, including an appropriate latent heat of evaporation, a low freezing point, and negligible copper corrosion and steel at temperatures below 100 °C. An experimental study of the thermal performance by increasing the adsorption bed thermal conductivity was conducted. Using0 10 % 20 and %30 % of metallic copper powder with activated carbon to improve the bed thermal conductivity. A sample is prepared with 20 % copper powder to find out the improvement of heat transfer characteristics to the cooling effect. The temperature gradient has been tested with two flow rates to examine the coolant performance and increase. Solar energy can be effectively utilized based on low-grade temperature consumption in such systems. This work aims to make an experimental investigation of the thermal performance of an activated carbon-methanol adsorption refrigeration system to study the effect of the enhanced thermal conductivity of the adsorbing bed. Using 0 %, 10 %, 20 %, 30 % of metallic copper powder with activated carbon to enhance the thermal conductivity of the bed, providing a significant improvement in the system efficiency, specific cooling power (SCP), and coefficient of performance of adsorption cooling. It is found that copper filing with a mass concentration of 20 % are appeared the optimal ratio metallic additive to enhance the thermal performance of the system. Moreover, the effect of the hot water flow rate is studied. Results indicated that the addition of 20 % metallic copper filings to the activated carbon lowered the evaporator temperature to reach -5 and -10 °C for heating water flow rates 3 and 2 LPM, respectively. Also, the addition of copper filing enhances the cycle COP of the system by 49 % and 46 % at hot water flow rates of 2and 3 LPM, respectively. The highest cycle COP of the current system reached was 0.92 for the condition 20 % additives at 3 LPM hot water flow rate. Owning the feature of great solar energy availability and the long daily sunny hours, solar-powered adsorption cooling systems have promising potential applications in Egypt. A mathematical model of the system performance is also studied.

Adsorption Solar Air Conditioning System for Singapore Climate

The design of an adsorption solar air conditioning system is investigated by using a model with an activated carbon–methanol working pair. This system is analysed with the solar insolation levels and ambient temperatures of Singapore. The proposed design mainly consists of two tubular reactor heat exchangers (TRHEXs) operating out of phase and driven by heat from an evacuated tube solar collector (ETSC). The pair of TRHEXs act as a thermal compressor and contain about 2.275 kg of activated carbon per reactor. The evacuated tube solar collector (ETSC) has better performance and is more cost effective than the flat plate solar collector (FPSC), even though it has a higher cost per unit. On the hottest day of the year, the proposed adsorption system has a maximum cooling power of 2.6 kW and a COP of 0.43 at a maximum driving temperature of 139 °C with a 9.8 m2 ETSC area. The system has a total estimated cost of EUR 10,550 corresponding to about SGD 14,800 with a 7-year payback time. At similar cooling capacities, the adsorption air conditioning system is expected to be more cost effective than the conventional system beyond an expected period of 7 years, with an expected lifetime of 15 to 20 years.

Optimization and experimental analysis of a solar powered adsorption refrigeration system using selective adsorbent/adsorbate pairs

Adsorption-based cooling system is a cost-effective method of heat conversion. It has the potential to dramatically enhance energy efficiency while also lowering pollutant levels. For this purpose, a solar-powered vapor adsorption refrigeration system (VAdRS) using activated carbon–methanol and zeolite–water as the working pair has been designed and experimentally evaluated. The aim of this experiment was to evaluate the coefficient of performance (COP) and specific cooling power (SCP) of a solar cooling unit by utilizing the optimum minimum and maximum mass concentration ratios. The novel solar-assisted adsorption refrigeration system optimization technique is used in this research to evaluate the optimal performance of the solar-powered VAdRS under various operating scenarios. The experiment was conducted at the optimum minimum and maximum mass concentration ratios of 0.1 and 0.2, respectively. The experimental results show that the activated carbon–methanol adsorption system produces a higher COP value than the zeolite–water adsorption system of 0.49–0.64 and 0.64–0.67 at constant evaporator and condenser temperature, respectively. It also showed that the higher SCP value was revealed in the zeolite–water-based adsorption cooling system as 207.5–217.4 kJ/kg. It was revealed that AC–methanol could be used to operate better in low-generating-temperature conditions. On the other hand, the zeolite–water adsorption system can be used at higher generating temperatures.

Performance Analysis of an Adsorption Refrigeration System Working on Activated Carbon/Methanol Pair Using Finned Tube Type Adsorber Bed

Adsorption refrigeration, being a unique and eco-friendly technology, has gained popularity over conventional refrigeration systems. The present study is aimed at developing an annular finned tube adsorber model which serves as a thermal compressor in adsorption refrigeration systems. The mathematical model is addressed numerically using finite difference discretization method and explicit scheme was used for the solution. The generalized model has been simulated for activated carbon–methanol working pair. The system has an optimum cycle time of 1800s. It was found to have a highest refrigeration capacity of 260.66 kJ/kg at a regeneration temperature of 393 K and evaporator temperature of 283 K. The highest COP (Coefficient of Performance) achieved by the system is 0.3706 at a regeneration temperature of 353 K and evaporator temperature of 283 K. A highest SCP (Specific Cooling Power) of 144.8 W/kg was obtained at an evaporator temperature of 283 K and regeneration temperature of 393 K.

Role of chemical equilibrium on the performance of an activated carbon–methanol adsorption refrigeration tube

The main compartment that determines the functionality of the adsorption refrigerator is the adsorption refrigerator tube (ART). Many scientists have suggested certain ART configuration that would help improve its adsorption performance. The focus of the research is to determine causes of the ART malfunction via material failure. The linear driving force (LDF)-based models and the chemical kinetic reaction were taken into account to determine the chemical equilibrium of the material. It was observed that the successes of the adsorption refrigerator depend on the source material of the activated carbon and the level of impurity in the activated carbon.

Experimental and Theoretical Study of the Energy Flow of a Two Stages Four Generators Adsorption Chiller

This work is concerned with a two stages four beds adsorption chiller utilizing activated carbon-methanol adsorption pair that operates on six separated processes. The four beds that act as thermal compressors are powered by a low grade thermal energy in the form of hot water at a temperature range of 65 to 83 °C. As well as, the water pumps and control cycle consume insignificant electrical power. This adsorption chiller consists of three water cycles. The first water cycle is the driven hot water cycle. The second cycle is the cold water cycle to cool the carbon, which adsorbs the methanol. Finally, the chilled water cycle that is used to overcome the building load. The theoretical results showed that average cycle cooling power is 2.15kW, while the experimental measurement revealed that the cooling capacity of the cycle is about 1.98 kW with a relative error of % 0.02. The generator and condensing temperatures are 83 and 30 °C, respectively. The coefficient of performance (COP) of that chiller was in the range of 0.37 to 0.49. The best operating point and the best working conditions were also investigated. The present chiller is superior more than the single stage, two beds adsorption chiller that works on the activated carbon methanol pair that needs a high ambient temperature.

Numerical Modeling and Thermal Analysis of an Adsorption Refrigeration System

The aim of this paper is to develop a complete, precise and simple numerical model based on the thermophysical properties of an adsorptive cooling system (using activated carbon–methanol pair), analyze and discuss the heat and mass transfer processes and identify the parameters which influence the system performance. In the design of adsorption refrigeration system, the characteristics of both adsorbate–adsorbent pairs and system operating conditions are very important. So in this model, different thermophysical properties of working pair such as, specific heat, density, isosteric heat of adsorption and desorption, and different temperatures of the system are considered. A simulation code, written in FORTRAN, is carried out. The performance of the system is assessed in terms of refrigeration effect and coefficient of performance (COP).

Performance investigation of a solar hot water driven adsorption ice-making system

A solar hot water driven solid adsorption ice-making system with heat storage was designed and constructed. The finned-tube absorbent bed in the water tank, which also acted as heat storage unit, was heated by the hot water from the solar vacuum tube collector in desorption process. The water in the tank was also auxiliary heated by electric heater to keep at the set desorption temperature. Activated carbon–methanol was utilized as the working pairs in the system. Effects of heat source temperature on system performance were experimentally investigated under four conditions: maintaining the water temperature in the tank at 94°C (boiling point), 85°C, 75°C, respectively, and heating the water to reach 94°C then naturally cooling the hot water without maintaining heating in desorption process. The experimental results showed that the temperatures around the finned-tube of the adsorbent bed was homogeneous, which was beneficial for desorption of the adsorbate. The maximum daily ice-making capacity of 8.4kg and the lowest temperature of −8.6°C were achieved when the hot water temperature was maintained at 94°C. The maximum refrigeration cycle coefficient of performance (COP) of 0.139 was obtained under the condition of heating the water to reach 94°C then cooling naturally the hot water without maintaining heating. The system heat utilization efficiency decreased with the increase of heat source temperature due to the greater heat loss in desorption process.

RETRACTED: Simulation of tubular adsorber for adsorption refrigeration system powered by solar energy in sub-Sahara region of Algeria

Abstract This paper presents a simulation and optimization of a tubular solar collector/adsorber destined for an adsorption refrigeration system developed in El Oued region, which is situated in the sub-Sahara regions of Algeria. The system uses activated carbon–methanol as a working pair, under real climatic data of the region. A theoretical model coupled between heat and mass transfer in adsorbent bed and energy balance in the solar collector/adsorber was presented in Dubinin–Astakhov equation was used to describe the adsorption phenomena. Effect of some important parameters, such as activated carbon types, adsorber tube size, tube wall material and collector glazing cover, on the system performances were investigated. The temperature, pressure and adsorbed mass profiles inside the adsorber have been shown and energy balance for the whole system was determined with relative error 0.014%. The optimized solar collector/adsorber was corresponded to a tube diameter of D = 0.118 m and a number of 8 tubes for filling 1 m 2 double glazed cover collector by about 38.59 kg of activated carbon based on stone coal. This design has a solar coefficient of performance about 0.21 and a collector efficiency η = 44.23% for a tilt angle 20.5° during August at this region. Use of this system, in this region, may be preserve electrical energy of about 28,303 MW h or 2434.058 toe of fossil fuel corresponding to 18396.950 tonne of carbon dioxide emission prevented from being released into the atmosphere.

Characterizations of Activated Carbon–Methanol Adsorption Pair Including the Heat of Adsorptions

This paper presents adsorption isotherms and isosteric heats of adsorption for methanol vapor adsorption for two commercially available activated carbon samples—207EA granules and WS-480 pellets (Calgon Carbon, U.S.A.)—which were also fully characterized using nitrogen sorption at 77 K. The heat of adsorption of methanol as a function of loading was determined using the Clausius–Clapeyron approach with isotherms obtained at 5 °C, 15 °C, and 25 °C. The isosteric heats of adsorption increased sharply at the small coverage due to increasing effect of condensation heat with coverage. The heat reached a maximum and then varies little with loading, with the average values at around 46.6 kJ/mol for 207EA and 45.1 kJ/mol for WS-480. The higher heats of adsorption for the former activated carbon reflect its more microporous nature (around 78 % compare to 62 % for WS-480 activated carbon). The heat of adsorption data is also comparable to that obtained elsewhere for other activated carbons.

Thermal behavior and performance assessment of a solar adsorption cooling system with finned adsorber

This paper presents a modeling and optimization investigation of a solar driven adsorption cooling system working with activated carbon–methanol pair. It deals with the effect of internal fins on the thermal behavior of the adsorber and on the system performance. A two-dimensional model describing the coupled heat and mass transfer in the adsorbent bed and energy balance in the main components of the solar collector is presented. Furthermore, a simulation code based on alternating direction implicit method is developed. This model has been validated by experimentation data.The analysis of the thermal behavior of adsorbent indicates that heat and mass transfer within the adsorbent is enhanced by increasing the number of fins. The simulation results show that, under the climatic, operating and design conditions of the system, the solar coefficient of performance is roughly invariant with changes in number of fins. The results indicate also that the thermal coefficient of performance is improved by increasing the number of fins. However, it is found that there is an optimal range of number of fins varying from 15 to 20 that allows obtaining an optimal performance; the corresponding range of fin spacing is found to be between 4 and 5.2 cm.

Experimental Analysis on Adsorption Characteristics of Methanol and R134A by Activated Carbon in Adsorption Refrigeration System

This paper presents adsorption and desorption characteristics of two different working pairs—activated carbon–methanol and activated carbon–R134a—determined experimentally. Dubinin–Radushkevich (D–R) equation is used to correlate the adsorption isotherms and to form the pressure, temperature, and concentration diagrams for both the assorted working pairs. The results show that the maximum adsorption capacity of activated carbon–R134a working pair is 1.21 times that of activated carbon–methanol. Temperature and pressure distribution throughout the adsorbent bed and their variation with adsorption time are also predicted. Use of artificial neural network (ANN) is proposed to determine the uptake from measured pressure and temperature. The back propagation algorithm with three different variants, namely, scaled conjugate gradient (SCG), Pola–Ribiere conjugate gradient (CGP), and Levenberg–Marquardt (LM) and logistic sigmoid transfer function are used, so that the best approach could be found out. After training, it is found that LM algorithm with 11 neurons is the most suitable for modeling adsorption refrigeration system. The adsorption and desorption uptake obtained experimentally are compared with the uptake predicted by D–R equation and ANN modeling.

Thermodynamic analysis and theoretical study of a continuous operation solar-powered adsorption refrigeration system

Due to the intermittent nature of the solar radiation, the day-long continuous production of cold is a challenge for solar-driven adsorption cooling systems. In the present study, a developed solar-powered adsorption cooling system is introduced. The proposed system is able to produce cold continuously along the 24-h of the day. The theoretical thermodynamic operating cycle of the system is based on adsorption at constant temperature. Both the cooling system operating procedure as well as the theoretical thermodynamic cycle are described and explained. Moreover, a steady state differential thermodynamic analysis is performed for all components and processes of the introduced system. The analysis is based on the energy conservation principle and the equilibrium dynamics of the adsorption and desorption processes. The Dubinin–Astakhov adsorption equilibrium equation is used in this analysis. Furthermore, the thermodynamic properties of the refrigerant are calculated from its equation of state. The case studied represents a water chiller which uses activated carbon–methanol as the working pair. The chiller is found to produce a daily mass of 2.63 kg cold water at 0 °C from water at 25 °C per kg of adsorbent. Moreover, the proposed system attains a cooling coefficient of performance of 0.66.

Performance Analysis of a Modular Adsorption Cooling System with Sonic Vibration in the Adsorber

This article presents a performance evaluation of an adsorption cooling system using activated carbon–methanol as the working pair. The desorption process was enhanced by a sonic-wave generator attached to the center of the side of the adsorber. The results show that the sonic-wave activation reduced the cycle time of the heating–condensation process and improved the system performance in terms of coefficient of performance, specific cooling power, and volumetric capacity power, of which the highest achieved for this system were 0.619, 229.15 W/kg, and 17.61 cm3/W, respectively.

Structure optimization and performance experiments of a solar-powered finned-tube adsorption refrigeration system

A large-diameter aluminum-alloy finned-tube absorbent bed collector was designed and optimized by enhancing the heat and mass transfer in the collector. The collection efficiency of the adsorbent bed collector was between 31.64% and 42.7%, and the temperature distribution in the absorbent bed was relatively uniform, beneficial to adsorption/desorption of the adsorbate in the absorbent bed. A solar-powered solid adsorption refrigeration system with the finned-tube absorbent bed collector was built. Some experiments corresponding to the adsorption/desorption process with and without a valve control were conducted in four typical weather conditions: sunny with clear sky, sunny with partly cloudy sky, cloudy sky and overcast sky. Activated carbon–methanol was utilized as the working pair for adsorption refrigeration in the experiments. The experiments achieved the maximum COP of 0.122 and the maximum daily ice-making of 6.5kg. Under the weather conditions of sunny with clear sky, sunny with partly cloudy sky, and cloudy sky, ice-making phenomenon were observed. Even in the overcast-sky weather condition, the cooling efficiency of the system still reached 0.039 when the total solar radiation was 11.51MJ. The cooling efficiency of the solar-powered adsorption refrigeration system with a valve control in the adsorption/desorption process was significantly higher than that without a valve control.

Parametric study and simulation of a heat-driven adsorber for air conditioning system employing activated carbon–methanol working pair

ObjectivesThis paper aims to present a parametric study to compare with the experimental results obtained previously for a typical activated carbon–methanol, adsorption air-conditioning system powered by exhaust heat. The main objective is to study the effect of wall thickness on the desorption temperature and the cooling performance. MethodsThe current study is a simulation/parametric investigation employing computational fluid dynamics (CFD) simulation technique. ResultsIt is found that the CFD result is close to the experimental works. In this CFD investigation, an input exhaust gas of 200°C would have bed temperature around 120°C while employing 20mm thick of wall made by stainless steel. The adsorber took around 10min to heat up and decrease to room temperature around the same period. This set of data produce a cooling power of 0.65kW and COP around 0.25 with cycle time of 1200s. ConclusionIt is concluded that higher input temperature would have relatively longer cycle time but it is able to produce higher cooling power in return. While in design, it proves that an optimal wall thickness should be 15–20mm of stainless steel that offer lower heat transfer rate to maintain the system under functional Tdes at all time. Practice implicationsThis paper proves that adsorption air-conditioning system is technically applicable; however wall thickness of the adsorber should be considered seriously as one of the important parameters for suitable heat transfer and improved adsorption–desorption rate of the system.

Solar still with vapor adsorption basin: Performance analysis

In this work, a vapor adsorption type solar still was designed, fabricated and tested at Thiagarajar College of Engineering, Madurai, India. A vapor adsorbent pipe network comprising activated carbon–methanol pair was integrated with the basin. Losses from the bottom of the still are considerably reduced due to sensible heat absorption by the activated carbon and latent heat of vaporization by methanol. Also water circulated through the inner tube of the adsorbent bed is used as a feed to basin, thus enhancing the evaporation rate during day time. The increase in temperature of the basin due to adsorbent bed and condensation of methanol vapor, augments the evaporation rate during the night time also. Sponges, gravels, sand and black rubbers were used in the vapor adsorption type solar still for improving the yield. Experimental results were compared with ordinary conventional basin type still. The governing energy balance equations for both conventional and vapor adsorption type solar still were solved analytically and compared with experimental results. Theoretical analysis gave very good agreement with experimental results.

Dynamic modelling of an activated carbon–methanol adsorption refrigeration tube with considerations of interfacial convection and transient pressure process

In the present study, a dynamic model of the adsorption refrigeration cycle was established with the consideration of interfacial convective heat transfer within adsorbent particles. In the model, a concept and mathematical definition of a transient pressure process at the beginning of the traditionally considered isobaric adsorption process are introduced. The model was solved numerically and experimentally verified in terms of the adsorbent/adsorbate temperature development, system pressure variation, and dynamic adsorption/desorption amount. A temperature jump at the beginning of the adsorption process was experimentally identified and was successfully predicted in the numerical simulation with the introduction of a transient pressure process. Numerical results simulated with the newly introduced transient pressure process and the traditional constant pressure process were compared. The comparison shows that the introduced transient pressure process can significantly improve the accuracy of the presented model. In addition, a notable adsorbate migration phenomenon was discussed according to the abnormal temperature development in the processes of isosteric heating and cooling. The present model can be used for a valve-controlled and long cycle-time based ART and other systems with similar operating procedures.

Solar adsorption refrigeration system using different mass of adsorbents

In this investigation, a prototype model of the solar adsorption refrigeration system was constructed and its performance was evaluated with different mass ratios of adsorbents in the laboratory for possible field application. The main components of the solar-driven cooling system were vacuum tube collector, adsorption bed, condenser, evaporator, chilling chamber, and temperature data logger. The experimental study was conducted to analyze the performance of solar cooling unit using different mass ratios of activated carbon–methanol from 0.250 to 2.50. A minimum cooling temperature of 12.2 °C was obtained with the manually prepared activated carbon–methanol with mass ratio of 1.00. The cooling coefficient of performance and specific cooling potential was also evaluated from performance calculations.

A non-uniform pressure and transient boundary condition based dynamic modeling of the adsorption process of an adsorption refrigeration tube

The adsorption refrigeration tube (ART) has drawn increasing attention because of its advantages of no moving parts, compact structure and use of low grade heat as the heat source. A new design of ART was developed, in which activated carbon–methanol was selected as the working pair for either refrigeration or air-conditioning purposes. Based on the typical configuration of the generator of the ART, a dynamic mathematical model was developed under the non-uniform pressure assumption and the introduction of a transient boundary condition of diffusion equation. Moreover, experiments were conducted for validating the model. The experimental data and numerical results were compared in terms of temperature development inside the carbon bed, with the transient and two popular simplified boundary conditions of vapor density respectively. The comparison shows that the transient boundary condition improves accuracy of the model and more importantly it is capable of reflecting the dynamic shift of dominant driving forces of the adsorption process inside the generator, i.e. shifting to temperature driving gradually from diffusion driving.