Anutosh Chakraborty

Thermodynamic formalism of water uptakes on solid porous adsorbents for adsorption cooling applications

This Letter presents a thermodynamic formulation to calculate the amount of water vapor uptakes on various adsorbents such as zeolites, metal organic frameworks, and silica gel for the development of an advanced adsorption chiller. This formalism is developed from the rigor of the partition distribution function of each water vapor adsorptive site on adsorbents and the condensation approximation of adsorptive water molecules and is validated with experimental data. An interesting and useful finding has been established that the proposed model is thermodynamically connected with the pore structures of adsorbent materials, and the water vapor uptake highly depends on the isosteric heat of adsorption at zero surface coverage and the adsorptive sites of the adsorbent materials. Employing the proposed model, the thermodynamic trends of water vapor uptakes on various adsorbents can be estimated.

Theoretical insight of adsorption cooling

This letter proposes and presents a thermodynamic formulation to calculate the energetic performances of an adsorption cooler as a function of pore widths and volumes of solid adsorbents. The simulated results in terms of the coefficient of performance are validated with experimental data. It is found from the present analysis that the performance of an adsorption cooling device is influenced mainly by the physical characteristics of solid adsorbents, and the characteristics energy between the adsorbent-adsorbate systems. The present study confirms that there exists a special type of silica gel having optimal physical characteristics that allows us to obtain the best performance.

Performance investigation of advanced adsorption desalination cycle with condenser–evaporator heat recovery scheme

Abstract Energy or heat recovery schemes are keys for the performance improvement of any heat-activated cycles such as the absorption and adsorption cycles. We present two innovative heat recovery schemes between the condensing and evaporating units of an adsorption desalination (AD) cycle. By recovering the latent heat of condenser and dumping it into the evaporative process of the evaporator, it elevates the evaporating temperature and hence the adsorption pressure seen by the adsorbent. From isotherms, this has an effect of increasing the vapour uptake. In the proposed configurations, one approach is simply to have a run-about water circuit between the condenser and the evaporator and a pump is used to achieve the water circulation. This run-around circuit is a practical method for retrofitting purposes. The second method is targeted towards a new AD cycle where an encapsulated condenser–evaporator unit is employed. The heat transfer between the condensing and evaporative vapour is almost immediate and...

Advanced Adsorption Cooling cum Desalination Cycle: A Thermodynamic Framework

We have developed a thermodynamic framework to calculate adsorption cooling cum desalination cycle performances as a function of pore widths and pore volumes of highly porous adsorbents, which are formulated from the rigor of thermodynamic property surfaces of adsorbent-adsorbate system and the adsorption interaction potential between them. Employing the proposed formulations, the coefficient of performance (COP) and overall performance ratio (OPR) of adsorption cycle are computed for various pore widths of solid adsorbents. These results are compared with experimental data for verifying the proposed thermodynamic formulations. It is found from the present analysis that the COP and OPR of adsorption cooling cum desalination cycle is influenced by (i) the physical characteristics of adsorbents, (ii) characteristics energy and (iii) the surface-structural heterogeneity factor of adsorbent-water system. The present study confirms that there exists a special type of adsorbents having optimal physical characteristics that allows us to obtain the best performance.Copyright

Thermodynamic Property Surfaces for Adsorption of R507A, R134a, and n-Butane on Pitch-Based Carbonaceous Porous Materials

The thermodynamic property surfaces of R507A, R134a, and n-butane on pitch-based carbonaceous porous material (Maxsorb III) are developed from rigorous classical thermodynamics and experimentally measured adsorption isotherm data. These property fields enable us to compute the entropy, enthalpy, internal energy, and heat of adsorption as a function of pressure, temperature, and the amount of adsorbate. The entropy and enthalpy maps are necessary for the analysis of adsorption cooling cycle and gas storage. We have shown here that it is possible to plot an adsorption cooling cycle on the temperature-entropy (T–s) and enthalpy-uptake (h–x) maps.

Adsorption Desalination: A Novel Method

The search for potable water for quenching global thirst remains a pressing concern throughout many regions of the world. The demand for new and sustainable sources and the associated technologies for producing fresh water are intrinsically linked to the solving of potable water availability and hitherto, innovative and energy efficient desalination methods seems to be the practical solutions. Quenching global thirst by adsorption desalination is a practical and inexpensive method of desalinating the saline and brackish water to produce fresh water for agriculture irrigation, industrial, and building applications. This chapter provides a general overview of the adsorption fundamentals in terms of adsorption isotherms, kinetics, and heat of adsorption. It is then being more focused on the principles of thermally driven adsorption desalination methods. The recent developments of adsorption desalination plants and the effect of operating conditions on the system performance in terms of specific daily water production and performance ratio are presented. Design of a large commercial adsorption desalination plant is also discussed herein.

Two-Dimensional Numerical Analysis of Membrane-Based Heat and Mass Cross-Flow Exchanger

ABSTRACT A two-dimensional numerical simulation model for a membrane-based heat and mass exchanger was developed. The system model equations were used to determine the coupled heat and moisture transfer from the humid air to the high concentrated liquid desiccant solution (LiCl, lithium chloride) by means of a parallel stack hydrophobic permeable membrane. The two streams of air and liquid desiccant solution were arranged in cross-flow directions. The fourth-order Runge–Kutta method was employed to solve these system model equations in a steady-state condition. This model enables one to predict the latent effectiveness of a membrane-based parallel cross-flow exchanger for dehumidification purpose in response to air to liquid mass flow ratio and the mass transfer unit number.

Adsorption Kinetics Emulation With Lattice Gas Cellular Automata

ABSTRACT Lattice gas cellular automata (LGCA), as a fluid dynamic simulation method, are conceptually simple and can be applied to deal with thermal interface effects to a wide array of boundary conditions. Based on LGCA, the lattice Boltzmann method has been successfully used to model a number of typical continuous fluid dynamic problems. In this research, however, we extend the general Frisch, Hasslacher, and Pomeau method from LGCA to the microscopic scale to emulate the surface adsorption process. Specifically, hexagonal grids topology and geometry are applied in two dimensions with 6-bit digits to represent different states of each grid node. The rule space is then determined as 66. A two-dimensional porous network is constructed for simulating a practical adsorbent material structure. The lattice gas collision and movement are implemented within periodic space boundary conditions. Local rules of lattice gas interaction with network surface are defined and examined. The adsorption probabilities on each adsorptive site, corresponding to adsorption potential with relationship to temperature, are taken into account. As a result, an intuitive visualization of physical surface adsorption kinetics is achieved.

Adsorption Characteristics of Modified MiL-101(Cr) for Gas (Mainly CH4) Storage Applications

As promising material for gas storage applications, MIL-101(Cr) can further be modified by doping with alkali metal (Li+, Na+, K+) ions. However, the doping concentration should be optimized below 10% to improve the methane adsorption. This article presents (i) the synthesis of MIL-101 (Cr) Metal Organic Frameworks, (ii) the characterization of the proposed doped adsorbent materials by X-ray Diffraction, Scanning Electron Microscopy, N2 Adsorption, Thermo-Gravimetric Analyzer, and (iii) the measurements of methane uptakes for the temperatures ranging from 125 K to 303 K and pressures up to 10 bar. It is found that the Na+ doped MIL-101(Cr) exhibits CH4 uptake capacity of (i) 295 cm3/cm3 at 10 bar and 160 K and (ii) 95 cm3/cm3 at 10 bar at 298 K. This information is important to design adsorbed natural gas (ANG) storage tank under ANG-LNG (liquefied natural gas) coupling conditions.Copyright

Impact of Alkali-Metal Impregnation on MIL-101 (Cr) Metal-Organic Frameworks for CH4 and CO2 Adsorption Studies

In this article, an assessment of the impact of alkali-metal-ion impregnation on metal-organic frameworks (MOF) is presented employing CH4 and CO2 adsorption isotherm data. At first, the parent MOF, MIL-101(Cr), is prepared by a fluorine-free hydrothermal reaction procedure and impregnated with Li, Na, and K alkali cations. These synthesised MOFs are characterized by N2 adsorption/desorption isotherm analysis, X-ray diffraction (XRD) measurement and scanning electron microscopy (SEM). The amount of CH4 and CO2 adsorption uptakes onto parent and alkali ions impregnated MIL-101(Cr) are conducted for wide ranges of pressures and temperatures. For understanding the effects of MOF synthesis process and alkali cations impregnation, CH4 /CO2 uptakes on perfect crystalline MIL-101(Cr) MOF are also calculated by Grand Canonical Monte Carlo (GCMC) simulation and the results are compared with experimental isotherm data of synthesised parent and alkali ions impregnated MIL-101(Cr) MOFs. It is found that the limiting uptakes and the isosteric heats are mainly influenced by the modified adsorbent structures due to alkali ions impregnation and the polarity of adsorbate molecules. Employing Dubinin-Astakhov (DA) equation, the energy distribution of synthesised parent and alkali doped MIL-101 (Cr) MOFs are also presented to identify the alkali cation effects and the surface heterogeneity.