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Summary This work presents a systematic techno‐economic assessment of 84 conventional and novel working fluid mixtures in two‐stage, double‐ and triple‐effect (Kangaroo) absorption refrigeration cycles. Rectifiers are modeled as staged distillation columns to capture appropriately the separation tasks. All mixtures are first evaluated based on process operating performance indicators including the coefficient of performance, the exergy efficiency, the cycle high pressure, the refrigerant and absorbent total flowrates, the total number of stripping stages and the distillate‐to‐feed ratios, subject to constraints ensuring feasible operation. The distillate‐to‐feed ratio, the number of stages in each rectifier and the individual flows of the refrigerant and the absorbent in different cycle circuits are considered as design parameters. The evaluation considers wide operating ranges, to identify the conditions that result in optimum values for the employed indicators. A multi‐criteria approach is used to generate few, highly performing candidates which are further evaluated using economic criteria. A mixture of acetaldehyde/dimethylformamide is selected as the best performing working fluid which exhibits at best 39% lower cost per ton of cooling and 7% higher coefficient of performance than NH3/H2O in the tripe‐effect cycle, with similar high performance observed in the double‐effect cycle too. The same mixture exhibits at best 38% lower coefficient of performance and 1% lower cost per ton of cooling than H2O/LiBr. [ABSTRACT FROM AUTHOR]

A systematic approach is proposed to investigate the influence of different thermodynamic models and multi-parametric variations propagated through single, double and triple effect absorption refrigeration (ABR) processes and to identify the models with the least sensitivity to variability. The approach highlights the parameters which mainly affect the ABR process performance in all indicators simultaneously. A sensitivity index quantifies the variation range of the ABR performance indicators with respect to parameter variability. Cost functions are developed which combine both performance indicators and state process variables. These are used to identify thermodynamic models which simultaneously a) enable close match of simulation results and reference data, b) maintain low process variability and c) give rise to process state and performance profiles of low non-linearity, despite changes in model parameters. We employ up to 12 thermodynamic models for NH 3 /H 2 O, comprising different eNRTL models and equations of state such as Redlich-Kwong, Peng-Robinson, Schwartzentruber-Renon and Cubic-Plus-Association. We consider uncertainty in up to 6 component and process parameters and up to 7 ABR performance indicators. The e NRTL-Helgenson model is selected in all ABR process cases. Peng-Robinson for hydrocarbon water systems is selected in single-effect ABR, whereas Redlich-Kwong is selected for the double and triple-effect cases. • Consideration of multiple thermodynamic models in absorption refrigeration. • Systematic identification of appropriate model using sensitivity analysis. • Application to single, double and triple effect systems. • Model selected based on proximity to reference data, parameter variability and non-linearity. [ABSTRACT FROM AUTHOR]

The presented work includes a detailed review of organic working fluid mixtures and corresponding Absorption Refrigeration (ABR) cycles available in published literature. Such processes are important as they enable exploitation of cleaner and renewable energy sources for cooling generation. Research efforts may be benefited by a systematically organized account of previous works in organic working fluids, which have received considerably less attention than conventional inorganic options. The reviewed developments are separated into working fluids used in single effect cycles and alternative configurations such as double effect, half effect and so forth. Details are reported regarding the operating conditions tested, the criteria used for working fluid selection and the ones selected as desirable options either experimentally or in simulation studies. Research on thermodynamics of organic working fluids suitable for ABR processes is also reported with respect to measured properties, experimental conditions and types of thermodynamic models. The characteristics of different process flowsheets are also analyzed, while commercial scale ABR applications are reported to motivate research in industrial/commercial scale systems. It is observed that there are few types of chemical groups repeated in working fluid investigations, with halogenated refrigerants and ether- and amide-based absorbents prevailing compared to other substances. Most experimental works pertain to single effect systems, with model-based approaches mainly used due to introduction of increasingly complex process modifications. The latter have been assessed with considerably fewer different fluid options compared to single effect systems. Thermodynamic investigations mainly combine experiments with parameter estimation for model development. Most works derive data and employ the NRTL activity coefficient model, often combined with cubic equations of state. • Comprehensive review of ABR processes with organic working fluids. • Mixture-ABR processes with operating conditions and performance indicators. • Thermodynamic property studies with experimental and modeling details. • Elaboration of ABR process configurations. • Commercial implementations of ABR systems. [ABSTRACT FROM AUTHOR]

This work presents a systematic approach toward the design of Organic Rankine Cycles (ORC) for the generation of power from multiple heat sources available at different temperature levels. The design problem is approached in a mixed-integer non-linear programming (MINLP) formulation where an inclusive and flexible ORC model is automatically evolved by a deterministic algorithm for global optimization. The basic building block of the model is the ORC cascade which consists of a heat extraction, a power generation, a condensation and a liquid pressurization section. The aim of the optimization is to determine the optimum number of ORC cascades, the structure of the heat exchanger network shared among different cascades, the operating conditions and the working fluid used in each cascade in order to identify an overall ORC structure that maximizes the power output. The approach is illustrated through a case study which indicates that a system of two waste heat sources is best exploited through two interconnected ORC utilizing different working fluids. [ABSTRACT FROM AUTHOR]

• Holistic evaluation of 13 vapor-compression absorption-refrigeration cycle combinations. • Performance evaluation based on economic (steady-state) and scheduling (dynamic) criteria. • Multi-criteria assessment approach for alternative configuration-working fluid selection. • For all cases, VCR cost is significantly lower compared to the nominal (dual VCR) case. • ABR-equipped configurations satisfy the cooling demand 16.47% more effectively than the dual VCR. A holistic approach is presented for the systematic assessment of the steady-state and dynamic performance of integrated absorption-compression refrigeration configurations that exploit thermal energy storage (TES). Thirteen configurations are evaluated including a dual vapor compression cycle (VCR), stand-alone single and double absorption refrigeration cycles (ABR) with two different working fluids (conventional NH 3 /H 2 O and novel acetaldehyde/DMF mixture), and their combinations thereof (VCR-ABR in parallel or cascaded configurations). The evaluation criteria combine steady-state performance metrics such as capital and energy cost, coefficient of performance (COP) and cooling water utilization, with dynamic operation indicators such as demand satisfaction, cooling and total energy utilities during transients between different operating levels. The dynamic operation optimization variables are the energy input per hour and the share of cooling output heading to each end-user. For all combined configurations, the resulting VCR cost is significantly lower compared to the nominal case of a dual VCR. The cascaded VCR-ABR configurations exhibit 241% higher VCR COP values than the nominal case. The latter also presents an average of 8.79% higher cooling water utilization than all the alternatives. The employment of TES enables the satisfaction of higher cooling demand than the cycle's nominal cooling capacity. ABR-equipped configurations satisfy the cooling demand 16.47% more effectively than the dual VCR. The latter is attributed to the ABR ability to operate in part load when at nominal efficiency, while presenting better dynamic cooling water use. The electricity requirements are reduced by 49% and 69% in the parallel and cascaded VCR-ABR configurations, compared to the nominal case. [ABSTRACT FROM AUTHOR]

• Novel and conventional working fluids for absorption refrigeration. • Techno-economic, environmental, health and safety performance assessment. • Improved performance compared to ammonia-water and water-lithium bromide. • Mixtures with acetaldehyde and methyl-formate reduce costs up to 40%. Absorption refrigeration is a promising technology for the replacement of vapour compression systems. Few, conventional mixtures of organic components have been evaluated to date as working fluids using mainly operating performance indicators. The aim of this work is to evaluate 75 working fluid mixtures, including 18 novel options as candidates for single-effect absorption refrigeration processes. Multiple performance indicators are considered such as coefficient of performance, exergy efficiency, high cycle pressure, distillate-to-feed ratio and number of stages in the rectifier, mass flowrates, process economics and safety, health and environmental properties of fluids. The evaluation is performed within a systematic, stage-wise approach, which employs multi-criteria analysis. It is observed that mixtures of acetaldehyde with dimethylformamide or methylpyrolidone exhibit up to 40% and 22% lower costs per ton of cooling compared to ammonia-water and water-lithium bromide. The same mixtures also outperform or match the coefficient of performance of ammonia-water. Propionaldehyde and methyl formate with the same absorbents are also competitive options in smaller scale processes, while they exhibit better health, safety and environmental properties than acetaldehyde. The new mixtures are of equivalent or better safety, health and environmental performance than other well-known refrigerants. [ABSTRACT FROM AUTHOR]

Post-combustion CO 2 capture plants include high costs that are associated with intense energy consumption. Heat pumps can recover heat from the flue gas and other sources in the CO 2 emitting plant and upgrade it to reduce the use of fossil-based steam. The few studies regarding heat pumps in CO 2 capture systems include arbitrary selection among limited working fluids, without optimizing the underlying cycle. This work implements a multi-criteria investigation of the performance of 20 working fluids for vapor compression heat pumps (VCHP) and 21 refrigerant/absorber pairs for absorption heat transformers (AHT), considering the operating optimization of each cycle for each fluid. A cascade cycle combining the two configurations (AHT-VCHP) is proposed, using the optimum fluids cyclopentane and water/potassium nitrate identified for the VCHP and the AHT. The annual operating costs are higher than the annualized capital expenditures. The proposed fluids outperform the conventional options. The VCHP with cyclopentane covers 58 % (2.68 GJ/t CO 2) of the reboiler duty with recovered heat and exhibits the lowest cost of $33.8/tCO 2. This is $18.7/tCO 2 lower than the cost of the conventional direct contact cooling unit that is used in capture plants. The VCHP remains competitive for up to 57 % increase in the electricity price. [Display omitted] • Evaluation of 41 known and novel working fluids through heat pump optimization. • Multi-criteria selection and technoeconomic analysis. • Vapor compression heat pump with cyclopentane covers 58 % of reboiler duty with recovered heat. • Its cost is $18.7/tCO 2 lower than that of a conventional flue gas cooling unit. • Vapor compression heat pump is competitive for up to 57 % higher electricity price. [ABSTRACT FROM AUTHOR]

District cooling plants are predominantly based on vapor compression refrigeration cycles with detrimental environmental impacts due to fossil-based electricity. Vapor absorption refrigeration cycles promise operating improvements and emission reductions in vapor compression-absorption refrigeration system configurations. However, the use of conventional vapor absorption refrigeration working fluids and the limited studies of systems with capacities that are relevant to district cooling plants, prohibit their scaling-up. This work compares the thermodynamic, environmental, and economic performance of seven configurations of the vapor compression refrigeration cycle with a double-effect vapor absorption refrigeration cycle that employs either the conventional ammonia/water or the novel acetaldehyde-N, N -dimethylformamide working fluid. These three cycles are compared with the cascade and parallel vapor compression-absorption refrigeration system configurations, with ammonia/water or acetaldehyde-N, N -dimethylformamide in the vapor absorption refrigeration. The coefficient of performance of the vapor compression refrigeration unit in the cascade configurations is 252% higher than the stand-alone vapor compression refrigeration configuration. The stand-alone vapor absorption refrigeration coefficient of performance with the novel fluid acetaldehyde-N, N -dimethylformamide is 9.1% higher than that of the vapor absorption refrigeration with ammonia/water. The cost per ton of cooling and the total equivalent warming potential of the cascade vapor compression-absorption refrigeration system with acetaldehyde-N, N -dimethylformamide are 65% and 67.8% lower than those of the stand-alone vapor compression refrigeration. The electrical energy utilization factor is 30.5% lower for the acetaldehyde-N, N -dimethylformamide fluid compared to ammonia/water, in the cascade configuration. • VCR-VAR cycles are promising for district cooling plants. • Comparative assessment of Cascade and Parallel VCR-double effect VAR systems. • Utilization of real district cooling plant and novel working fluid in VAR. • Coefficient of performance of the VCR in the VCR-VAR is increased by 252%. • Costs and emissions in VCR-VAR are reduced by up to 67.8%. [ABSTRACT FROM AUTHOR]