Activated Carbon Methanol Pair Research Articles

Investigation The performance of a Linear Fresnel Solar Concentrator Integrated with an Adsorption Refrigeration Cycle

A large amount of the energy produced is used for heating and cooling application. Many studies at the present time are looking for ways to reduce this consumption or use a renewable energy source to reduce dependence on fossil fuel energy. In this research, the used of solar energy to power a hybrid adsorption ice-maker, a linear Fresnel solar concentrator type, with a total area of 5 m2, is used for this purpose The concentrator was designed, built and conducting an experimental study in Baghdad (latitude 33.33 and longitude 44.14) for the solar system that which is consisting of the concentrator with a double absorber type evacuated tube has been used, tank, pump and accessories to investigate the performance of the system and the effect of the water flow on the unit performance. The performance of the adsorption system is studied theoretically. The adsorption system works with the activated carbonmethanol pair the mass of activated carbon is 0.5 and while the mass of methanol is 1.6 kg. The experimental work was achieved at July 2019 and the results showed that the maximum temperature of the water inside the tank obtained was 95 °C when the rate of water flow through the collector loop was 0.5 kg/min and that the maximum thermal efficiency was about 40% at the same flow amount. The theoretical results showed that the best coefficient of performance for the adsorption refrigeration system was 0.43 at the generator temperature of 95 °C and the condensing temperature of 30 °C.

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.

Methanol adsorption behaviors of compression-molded activated carbon fiber with PTFE

In order to improve the cold production performance of adsorption chillers using an activated carbon-methanol pair, we studied a high-density molded adsorbent consisting of activated carbon fiber and polytetrafluoroethylene (PTFE). The high-density activated carbon fibers (HDACF) with an apparent density of 135–357 kg m−3 were successfully prepared by the addition of a low dose of PTFE through kneading and mechanical compression processes. Experimental results showed that the methanol adsorption equilibria on the HDACFs could be expressed by the Dubinin–Astakhov equation. The HDACF with a larger apparent density adsorbed and desorbed methanol more rapidly. It was possible to estimate the temporal changes in the amount of methanol adsorption, and the surface temperature of the HDACF for both adsorption and desorption processes using calculation model established in this study. The calculated results showed that the adsorption rate of methanol vapor achieved a maximum apparent density 380 kg m−3 for the HDACF.

Performance of finned adsorber-desorber refrigeration system using activated carbon-methanol pair

Performance of finned adsorber-desorber refrigeration system using activated carbon-methanol pair

SOLAR-POWERED ADSORPTION REFRIGERATION CYCLE OPTIMIZATION

Solar energy is an attractive energy source among various renewable energy resources in Malaysia as relatively high solar radiation is available throughout the year. This solar energy can be utilized for air-conditioning by using solar-powered adsorption refrigeration cycle. Intermittent nature of the solar radiation leads to a challenge for continuous air-conditioning operation. In the present study, a combination of solar-powered adsorption refrigeration system and thermal storage is studied. Activated carbon-ammonia and activated carbon-methanol are the working pairs of the adsorption reaction. Analytical calculation results show that activated carbon-methanol pair indicates higher coefficient of performance (COP) than activated carbon-ammonia pair, while adsorption chiller system with hot water thermal storage has higher COP than the system with ice thermal storage. For the activated carbon-methanol case with hot water thermal storage, the COP is 0.79. Since this COP analysis is based on the ideal case with uniform temperature distribution within the reactor beds, which achieves equilibrium states at the end of the reactions. In more realistic situation, the reaction process will be terminated before reaching to the equilibrium states because of the non-uniform temperature distribution and the time required for the reaction. Transient simulation in which heat transfer and reaction equation are combined will be performed to model actual reactors.

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).

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.

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.

Exergy Assessment of Single Stage Solar Adsorption Refrigeration System Using ANN

A new approach based on artificial intelligence is proposed here for the exergy assessment of solar adsorption refrigeration system working with activated carbon-methanol pair. Artificial neural network model is used for the prediction of exergy destruction and exergy efficiency of each component of the system. Pressure, temperature and solar insolation are used as input variables for developing the artificial neural network model. The back propagation algorithm with three different variants such as CGP, SCG and LM are used in the network A and network B. The most suitable algorithm and the number of neurons in hidden layer are found as LM with 9 for network A and SCG with 17 for the Network B. The artificial neural network predicted results are compared with the calculated values of exergy destruction and exergy efficiency. The values of the exergy destruction and exergy efficiency of components (condenser, expansion device, evaporator, adsorbent bed, solar concentrator and overall system) are found to be close to 1. The RMS and COV values are found to be very low in all cases. The comparison of the results suggests that the artificial neural network provided results are within the acceptable range.

Thermal design of parabolic solar concentrator adsorption refrigeration system

This study presents a thermal design of solar-powered adsorption refrigeration with the type of activated carbon-methanol pair. The designed module consists of an evacuated glass tube equipped with a parabolic solar concentrator as generator, sorption bed, evaporator, and condenser units. A thermodynamic design procedure and a mathematical model of a steady state system with activated carbon refrigerator have been developed. The adsorber is heated by solar energy collected by a parabolic solar concentrator. The temperature of the working pair in the adsorber, the amount of methanol leaving and reabsorb bed, and the refrigerated box was estimated. An optimize design of the system to achieve higher cycle COP was presented. Maximum cycle COP = 0.576 and COPnet = 0.375 with Tmax reached 157.8°C, TB = 57.5°C, Mac = 0.907 kg, and the concentration of methanoldesorped equal to 0.206 kg/kgac.

Comparison among three adsorption pairs for using as the working substances in a multi-bed adsorption heat pump

A comparison among three adsorption pairs (activated carbon–methanol, silica gel–water and 13X molecular sieves–water) for using as the working substances in a four-bed adsorption heat pump is presented. A solid-side resistance model considering a finite mass flowrate of heating/cooling fluid was adopted. The result shows that, for small mass flowrates of the heating/cooling fluid, assuming a constant temperature for the heating/cooling fluid might give rise to an over-predication of the system performance. For the adsorption heat pump, there exists an optimum mode operating time ( τ) which corresponds to a maximum specific cooling power. For operations at the maximum specific cooling power ( τ = 3–6 min) and with regeneration temperatures in the range 80–120 °C, among the three adsorption pairs, the activated carbon–methanol pair leads to the highest specific cooling power, COP value and second-law efficiency. For the silica gel–water pair, the temperature rise resulting from adsorption heat significantly downgrades the system performance. This causes its corresponding specific cooling power, COP value and second-law efficiency to be lower than those for the activated carbon–methanol pair. The 13X molecular sieves–water pair possesses the smallest cyclic variation of adsorbate content, thus it yields the lowest specific cooling power, COP value and second-law efficiency.

Experimental thermodynamic cycles and performance analysis of a solar-powered adsorptive icemaker in hot humid climate

This paper analyzes and presents the thermodynamic cycles and the experimental performance parameters of a solar adsorptive icemaker that uses activated-carbon methanol pair. The solar energy technology employed is far less sophisticated than that of collectors using selective surface or evacuated tubes. The collector-adsorber is multi-tubular with an opaque black radiation-absorbing surface, and thermal insulated by means of transparent covers, the so-called transparent insulation material (TIM). The solar radiation hits on both faces of the tubes by means of semi-cylindrical reflectors. It is shown the results of tests carried out in a region of Brazil close to the Equator, on days characterized by the predominant cloud cover degree. Three cycles have been analyzed: one with clear sky, another with partially cloudy sky, and a third under entirely cloudy sky. The maximum regenerating temperatures were 100.1, 87.3 and 92.7 °C, with an ice production of 6.05, 2.10 and 0 kg by square meter of projected area, for cycles of clear sky, partially cloudy and overcast nights, respectively.

Dimensioning, thermal analysis and experimental heat loss coefficients of an adsorptive solar icemaker

The dimensioning, a thermal parameters analysis and the experimental heat loss coefficients of an adsorptive solar refrigerator prototype used for ice production are presented. The solar icemaker operates in an intermittent cycle, i.e. without recovering heat. It uses the activated carbon–methanol pair whose basic components are an adsorber coupled to a static solar collector, a condenser and an evaporator. Some innovations were considered, especially those brought about by French researchers, in which the adsorber was always box-shaped with extended surfaces, and air condensers were used. For the present system, the adsorber is bi-facially irradiated and covered with transparent insulation material (TIM), the geometric configuration of the main components is multi-tubular, and a water condenser is used. TIM polycarbonate covers are used on the top and bottom of the adsorber. The components of the prototype were dimensioned after the results from numerical simulations using meteorological data valid for the hottest six months in João Pessoa (7°8′S, 34°50′WG), whose climate is typically hot and humid. The machine was designed to produce up to 10 kg of ice/day per square meter of solar collection surface. Analyses of the thermal parameters influence on the ice production as well as parameters for dimensioning each component of the machine are presented. The overall heat loss coefficient by the top and the bottom of the adsorber–solar collector component are experimentally evaluated. The tests were performed using an incandescent lamp panel disposed on a 1 m2 surface, totalizing a thermal power of 3600 W. The results show a good efficiency of the TIM covers, achieving overall heat loss coefficient values between 0.54 and 1.90 W m−2 K−1.

Heat and mass transfer in the adsorbent of a solar adsorption cooling system with glass tube insulation

A solar adsorber with glass tube insulation used in a solar adsorption cooling system is proposed and investigated. The adsorber is a metal tube packed with activated carbon methanol pair surrounded by a vacuum tube glazing. A mathematical model, which accounts for the heat and mass transfer of sorption (adsorption and desorption) processes as well as the effects of non-equilibrium and non-uniform temperature and pressure distribution, is developed and experimentally validated. Based on the model simulation, the influence of different physical variables on the performance of the adsorber and their variations are simulated and discussed. It has been found that the thermal efficiency of the solar adsorber is about 30% and the solar adsorber configuration used in this study is one of the good configurations that can be used for adsorption refrigeration. The mathematical model is capable of predicting the performance of the solar adsorber.

Performance of a new solid adsorption ice maker with solar energy regeneration

A predictive model for an adsorption solar cooling system using the activated carbon–methanol pair and its numerical simulation are presented. This model accounts for instantaneous heat and mass transfers in each one of the machine components along a characteristic average day for each month. The solar powered ice maker consists of the following basic components: a reactor containing an adsorptive bed coupled to a static solar collector covered by Transparent Insulation Material (TIM), a condenser and an evaporator. A uniform pressure model for the reactor is considered. The bed’s radial temperature distribution is determined by means of a one-dimensional numerical method based on a finite difference technique. The machine’s performance is evaluated according to meteorological data valid for the hottest six months in João Pessoa (7°8′S, 34°50′WG), whose climate is typically hot and humid. The results are compared with those obtained from an identical system with a single cover solar collector. These last data are then compared to the results obtained in a particular month from the experimental study of a prototype with equivalent components, tested in Tunisia. The TIM cover’s system proved to be about 40% more efficient than the single cover solar system. The average net solar COP was 0.13 for the TIM cover system during the six month considered period. This corresponds to 7–10 kg/day of ice production per square meter of solar collection surface, respectively, for March and December, with solar irradiations ranging from 20 to 23 MJ/m 2, during the October–March period.

Dynamic simulation and experiments of a heat regenerative adsorption heat pump

The dynamic behavior of a heat regenerative adsorption heat pump employing an activated carbon–methanol pair has been studied. The mathematical models to simulate the system are presented. Curves of the system’s Specific Cooling Power and Coefficient of Performance versus evaporating temperature for the system’s variables are obtained by numerical calculation. To assess the validity of the model, experimental data with different operational parameters is furnished. The experimental results are in close agreement with the calculated data of the dynamic simulation. Therefore, by means of dynamic simulation, the performance of the system can be predicted, and the optimum operational parameters can be selected.

A Continuous Heat Regenerative Adsorption Refrigerator Using Spiral Plate Heat Exchanger as Adsorbers: Improvements

Spiral plate heat exchangers as adsorbers have been proposed, and a prototype heat regenerative adsorption refrigerator using activated carbon-methanol pair has been developed and tested. Various improvements have been made, at last we get a specific cooling power for 2.6 kg-ice/day-kg adsorbent at the condition of generation temperature lower than 100°C. Discussions on the arrangements of thermal cycles and influences of design are shown.

Performances of adsorption systems for ambient heating and air conditioning: Performances de systèmes à adsorption pour le chauffage et le conditionnement d'air d'ambiance

Two adsorption systems are considered: zeolite–water and activated carbon–methanol, both consisting of two `uniform temperature' adsorbent beds operating with internal heat recovery by a heat carrier circuit. Regarding the zeolite–water system, the performance obtained with a new adsorbent bed, with good heat transfer properties, is compared with a traditional tube and fin exchanger embedded with zeolite pellets. The performances were calculated by using a dynamic model developed and validated previously. Results show that the system based on the new adsorber has a higher specific power and the same Coefficient of Performance. Results of simulation for adsorbers consisting of finned tube heat exchangers and utilising the activated carbon–methanol pair are also presented.

Simulation of a new adsorptive solar ice maker using activated carbon-methanol pair

SYNOPSIS An analytical model of a new-conception of solid sorption solar cooling system and its numerical simulation are presented. This model combines instantaneous heat and mass transfers in each component of the machine, during a whole characteristic average day of each month. The innovation of the machine consists in the use of a polycarbonate honeycomb Transparent Insulation Material [TIM] cover for the solar collector and multitubular configurations for the reactor and the evaporator. The performance of the machine is evaluated utilising meteorological data for one region of Brazil close to the equator, for the hottest six months. The results are compared with those obtained by modeling the system with a single cover solar collector and those from an experimental study of a prototype with usual components realised in Tunisia. The average net solar Coefficient of Performance [COP] for the six months was 0.13 for the TIM cover system, corresponding to an ice production going from up to 7 to 10 kg per day per square metre of collector surface, respectively for March and December, with solar irradiations of 20 to 23 MJ/m2.

Experiment on a continuous heat regenerative adsorption refrigerator using spiral plate heat exchanger as adsorbers

Spiral plate heat exchangers were proposed to be used as adsorbers, and a prototype heat regenerative adsorption refrigerator using the activated carbon-methanol pair was developed and tested. The adsorption system using 12 kg activated carbon has a cycle time of 40 min., meanwhile 14 kg ice per day was made.