Thermodynamic study on absorption refrigeration systems using ammonia/ionic liquid working pairs

This thesis was aimed to analyse the feasibility and the performance of ionic liquids as an absorbent for ammonia refrigerant in absorption refrigeration systems. Ionic liquids, novel and tailor-made absorbents, can be used with ammonia as working pairs for absorption refrigeration cycles and give some advantages such as elimination of the rectification process in ammonia/water systems. The performances of several ammonia/ionic liquid mixtures working pair available in the literature were then theoretically studied and analysed for absorption refrigeration applications using selected NRTL model. In addition, new selected ammonia/ionic liquid mixtures working pair for absorption refrigeration applications were also theoretically studied and analysed. The results show that the coefficient of performance (COP) of the absorption systems working with ammonia/ionic liquid working fluids were about similar when compared with ammonia/LiNO3 at same cooling capacity and operation conditions. Among all of selected ammonia/ionic liquid working fluids studied in this thesis, only [N1113][NTf2] presented higher COP that that of ammonia/LiNO3 at certain operation conditions. The COP of the systems with other ionic liquids as absorbents follows an order of [EtOHmim][BF4] > [N111(2OH)][NTf2] > [EtOHmim][NTf2] at all operation conditions. Finally it can be concluded that the ionic liquid has a great potential to be an alternative absorbent for ammonia refrigerant. The ammonia/ionic liquid working fluid can provide competitive performance in comparison with conventional absorbent for ammonia refrigerant. However, some drawbacks were still remains to be solved such as relatively low solubility of ammonia into ionic liquids which affects to the solution circulation mass flow ratio and relatively high viscosity of ionic liquid in comparison with other conventional absorbent which may affects to the performance of absorber and solution pump

Analysis and evaluation of 2,2,2- trifluoroethanol/ionic liquids as new

In this work, the performance of new proposed 2,2,2-trifluoroethanol/ionic liquid mixtures for absorption heat transformer applications is studied. The 1-ethyl-3-methylimidazolium tetrafluoroborate ([emim][BF4]) and 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4] have been selected as new absorbent for absorption heat transformer systems with 2,2,2- trifluoroethanol (TFE) as refrigerant. The selection of these ionic liquids is based on a computationalexperimental study to select suitable ionic liquids with optimized properties for TFE absorption applications. The performance of these two TFE/ionic liquid mixtures is analysed and evaluated. The solution concentration (i.e. refrigerant in ionic liquids) in absorber and generator are predicted based on experimental vapour-liquid equilibrium data. The experimental data of both vapor liquid equilibrium and excess enthalpy of the mixture are correlated using Non-Random Two Liquid (NRTL) method available in Aspen Plus software. The performance indicators, such as coefficient of performance and solution mass flow rate are studied and analyzed. The simulation results show that the new proposed working fluid of TFE/[bmim][BF4] and TFE-[emim][BF4] are suitable for absorption heat transformer applications. The COP of new proposed TFE-ionic liquid working pairs is slightly lower than conventional waterlithium bromide working fluid. However solution mass flow ratio of the new proposed working fluids gives better values as compared to conventional water-lithium bromide working pair. The TFE/[bmim][BF4] working pair gives better performances as compare to the TFE/[emim][BF4] working pair.This research project was financially supported by the FP7-People- 2010-IRSES Program (NARILAR -New Working Fluids based on Natural Refrigerants and Ionic Liquids for Absorption Refrigeration, Grant Number 269321) and the Spanish Ministry of Economy and Competitiveness (DPI2012-38841- C02-01. Hifni M. Ariyadi are grateful to the fellowship from Universitat Rovira i Virgili–Fundació Caixa Tarragona

Design of the Organic Rankine Cycle (ORC) System Using R600 and R600a as Working Fluid

Organic Rankine Cycle (ORC) is one of the alternative technologies for generating electricity from low to medium level heat sources. ORC operates at low temperatures and pressures using two types of organic working fluids. The organic working fluids as the refrigerants were chosen in the ORC system instead of water, which is suitable for high pressure and temperature applications. Since the performance and configuration of the ORC system rely on its working fluids, the selection of the working fluid for the ORC system becomes crucial. The system utilizes low-temperature heat sources as a supply of heat energy that flows through the evaporator and is then received by the working fluid to operate the cycle. In this study, two dry type working fluids, namely butane (R600) and isobutane (R600a), were used to thermally design an ORC to recover geothermal waste heat. The working fluids were designed using mathematical calculations based on thermodynamic laws. The results revealed that a slightly higher thermal efficiency value was achieved when using R600 as the working fluid, which was 12.8% compared to R600a

Emulator-type load-based tests for dynamic performance characterization of air conditioners

Current air-conditioning performance evaluation procedures are based on experimental tests conducted at a fixed compressor speed while deactivating the native control system to simplify data acquisition and ensure reproducibility of the results. Conversely, the actual operation of air conditioners responds to thermal loads with variable or cyclic modulations of the compressor speed and expansion valve opening according to the native control system. This study aimed to establish a new reproducible and representative methodology for evaluating the dynamic performance of air conditioners. The developed emulator-type dynamic performance testing facility features hybrid characteristics consisting of an emulator, which is used to simulate the dynamic response of indoor and outdoor environments, and the hardware of a testing facility for performance measurement. This study demonstrates the integrity of the constructed testing facility and the ability of the emulator-type testing methodology to determine the dynamic performance of an air conditioning unit using its native control system, in response to variations in the room-side environment

Economically viable electromechanical tensile testing equipment for stretchable sensor assessment

The growing interest in soft robotics increases the demand for stretchable sensors. The high performance of stretchable sensors depends much on the linearity, reliability and hysteresis of the stretchable conductive materials. In the applications of conductive materials such as in dielectric elastomer actuators, a stretchable conductive material should maintain the conductivity while sustaining large and multiple cycles of stretch and release tests. To understand the stretchable electrode quality, researchers should perform an electromechanical test. However, researchers require a high investment cost to use a professional type of electromechanical tensile test. In this research, we proposed an economically viable version of the Do-it-yourself (DIY) electromechanical tensile test (EMTT) to resolve the high investment cost problems. The DIY-EMTT is based on the Arduino-nano module. We integrate the load cell, displacement sensor, motor linear stage and DIY resistance meter. We can use the DIY mechanism to suppress the instrumental cost from thousands to hundreds of dollars. Furthermore, we provide a step-by-step guide to build the DIY-EMTT. We expect our DIY-EMTT to boost stretchable sensor development in soft robotics