Vapour Absorption Machine

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Thermodynamic Properties of 1 Ethyl-3Methylimidazolium Ethylsulphate - Water Based Working Pair for an Absorption Refrigeration System Gorakshnath D. Takalkar* and Sunil S. Bhagwat


Abstract— Absorption refrigeration systems (ARS) are alternative systems to conventional compression cycles in which the energy necessary for the refrigeration is provided through heat instead of mechanical power. The present work deals with thermodynamic properties evaluation of Ionic liquid 1 Ethyl-3-methylimidazolium ethyl sulphate (EMISE) and water as an alternative working. The local composition based activity coefficient model i.e. Non-Random Two liquid (NRTL) is being used to predict the thermodynamic properties of IL based binary mixture. The estimated properties of present binary mixture include vapor pressure, specific enthalpy of mixture, specific entropy and excess free energy. The required state diagrams for this solution are calculated and represented. Also, NRTL were employed to produce a Dühring's plot (pressure-temperature-concentration) with water mole fraction of 0.45 to 1 and solution temperature from 5 0C to 100 0C. These properties are useful to study the feasibility of using EMISE-H2O in an absorption cycles and to show some favorable results for cooling and refrigeration. Keywords: — Absorption Refrigeration, Activity coefficient, EMISE-H2O, Ionic Liquid

I. INTRODUCTION he application of thermal energy for absorption cooling and heating cycles (Absorption refrigeration, Absorption Heat Transformer, Absorption Heat Pump) has been gaining rapid attention in today’s time. These systems do not cause ozone layer depletion and global warming problems unlike the mechanically operated vapor compression refrigeration system. These utilize available waste heat, renewable solar energy and geothermal energy as main source for operation. Use of low grade energy like heat instead of electricity reduces the operating cost significantly. Thus they are a viable and economic option for cooling and refrigeration application. Gorakshnath D. Takalkar, a Ph.D. student in Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai - 400019 INDIA. (*corresponding author, phone: +91-996-702-5033; e-mail: goraksh3@gmail.com, ce08gd.takalkar@pg.ictmumbai.edu.in). Dr. Sunil S. Bhagwat, Professor in Chemical Engineering Department, Institute of Chemical Technology, Matunga, Mumbai - 400019 INDIA. (phone: +91-22-3361-2001; Fax: +91-22-3361-1020; e-mail: ss.bhagwat@ictmumbai.edu.in).

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The most useful combinations of working fluid include lithium bromide-water (LiBr-H2O) where water is a refrigerant and ammonia-water (NH3-H2O) systems where water is absorbents. Inherent drawback of using LiBr-H2O and NH3H2O as refrigerants is the crystallization, corrosiveness of LiBr and the toxicity, flammability and rectification of NH3. Present work uses ionic liquid (IL) based alternative working pair to overcome the corrosion and crystallization problems occurred in the conventional working pairs. Ionic liquids (ILs) are defined as an organic salt that belong to a class of low temperature molten salts comprising of an organic cation and an inorganic anion. The negligible vapor pressure, stability in the air and water with melting point below 373.16 K , IL have been used as an organic green solvent in catalysis and separation process. The water can be regarded as a green refrigerant, which is nontoxic and with high enthalpy of evaporation and excellent thermal characteristics. Water has a good solubility in the ionic liquid. Hence, water was, is, and will be a good refrigerant in the domain of refrigeration. Due to these advantages ILs could be used as new absorbents in absorption system [1], [2], [3], [4]. Zuo et al. (2010) [5] measured properties like vapor pressure, heat capacity and density of EMISE water mixture at the various temperatures and IL concentrations. They have used Non-Random two liquid (NRTL) activity...
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