Absorption Refrigeration Research Articles

Exergy and exergoeconomic comparative analysis of three NH3–NaSCN absorption refrigeration cycles driven by solar collector

Exergy and exergoeconomic comparative analysis of three NH3–NaSCN absorption refrigeration cycles driven by solar collector

Exergoeconomic evaluation and multi-objective optimization of a novel geothermal-driven zero-emission system for cooling, electricity, and hydrogen production: capable of working with low-temperature resources

Geothermal energy is an abundant natural resource in many regions around the world. However, in some areas, the temperature of the geothermal energy resource is too low to be efficiently harvested. Organic Rankine cycles (ORCs) are known for recovering heat from low-temperature resources and generating electricity. Furthermore, half-effect absorption chillers (HEACs) are designed to produce cooling with low-temperature resources. This study proposes a novel configuration that utilizes an ORC for electricity generation, a HEAC for cooling production, and a PEM electrolysis system to produce hydrogen. The power section consists of two turbines, one driven by the vapor produced from the geothermal flow expansion, which powers the PEM section, while the other turbine in the ORC is used to drive pumps and electricity production. First, the system is thermoeconomically analyzed for an initial set of inputs. Then, various parameters are analyzed to determine their influences on system performance. The analyses reveal that the system can work with geothermal source temperatures as low as 80 °C, but the exergy and energy (thermal) efficiencies decrease to around 17% under the base settings. Furthermore, the system is capable of working with resource temperatures up to 170 °C. Ten parameters are found to affect the system’s efficiency and effectiveness. To optimize the system, the Non-dominated Sorting Genetic Algorithm II (NSGA-II) is implemented to find the optimum conditions. The objective functions are exergy efficiency and unit polygeneration cost (UPGC), which can conflict. The optimization shows that the exergy efficiency of the system can reach 48% in the optimal conditions (for a heat source temperature of 112 °C and a mass flow rate of geothermal fluid of 44 kg/s), with a hydrogen production rate of 1.1 kg/h.

Techno-economic analysis of blue ammonia synthesis using cryogenic CO2 capture Process-A Danish case investigation

Ammonia is a vital chemical with numerous applications. Currently, the primary methods for generating the necessary reactants for ammonia production involve steam methane reforming (SMR) and cryogenic air separation unit (CASU), while the Haber-Bosch process converts these reactants into ammonia. However, the SMR process releases substantial amounts of CO2, making it imperative to employ an efficient and cost-effective CO2 capture technology to mitigate emissions. This investigation focuses on evaluating the cryogenic CO2 capture (CCC) process for blue ammonia production and provides a thorough economic analysis, estimating both the initial investment costs and operational expenses involved in producing blue ammonia. The results indicated that the CCC process can capture 90% of the CO2 content in the flue gas emitted by the SMR, incurring an energy penalty of 0.724 MJe/kgCO2 while capturing CO2 in the liquid phase with purities exceeding 99.9%. In this case, the estimated CO2 capture costs would be 18.05, 45.1, and 16.65 USD/ton in 2021, 2022, and 2023, respectively. This represents a 40% reduction compared to the CO2 capture costs associated with conventional amine-based technology. The results of this study indicate that the annual electricity costs for ammonia production increase by 38.5% and 64.2% when employing the CCC and amine-based processes, respectively. This investigation employed an isothermal reactor for ammonia synthesis, using the heat from the exothermic reaction in a water ammonia absorption refrigeration cycle (ARC) to condense and purify ammonia. The results show that the ARC system can effectively condense ammonia at −6 °C, producing a liquid ammonia stream with 99.3% purity. This leads to a 95% reduction in power consumption compared to a vapor compression refrigeration cycle (VCRC). Consequently, this method has the potential to decrease the annual operational costs for ammonia production by 2.92%, 2.69%, and 3.13% in 2021, 2022, and 2023, respectively. This study indicated that the hydrogen production unit incurs the highest initial investment costs, as well as operating costs, in the blue ammonia production process, followed by CASU and the Haber-Bosch process.

Numerical modeling of a confined falling liquid film sheared by a gas flow in a plate heat exchanger of an NH3/H20 absorption chiller

In recent years, the demand for cooling has seen a substantial increase, primarily due to rising summertime temperatures. Conventional mechanical compression air conditioners have played a predominant role in fulfilling this demand, albeit at the cost of significant electricity consumption. In response, absorption chillers have emerged as an eco-friendly alternative, powered by sustainable heat sources like solar energy or industrial waste heat. The present work is conducted within the framework of developing compact absorption chillers incorporating plate heat exchangers. It builds upon prior research by improving an existing numerical model for falling film plate heat exchangers within an NH3/H2O absorption chiller. This former numerical model evaluates the coupled heat and mass transfer between the liquid film and the vapor flow while excluding hydrodynamic interactions at the liquid-vapor interface. The current investigation aims to address compactness and cost-efficiency limitations in absorption chillers. The consequences of operation within confined spaces were numerically evaluated. An innovative analytical model was developed to quantify the influence of the interactions at the liquid-vapor interface. Shear stress and interfacial perturbations were considered compared to the classical Nusselt model, enabling the evaluation of the changes in the average film thickness and the flooding phenomenon. This analytical model was then added to the previously developed heat and mass transfer model. The numerical model was applied to both the desorber and absorber units. The results show that increased confinement has minimal effects on the transfer coefficients. Additionally, an approach is suggested for estimating flooding in confined spaces and the results are compared with various correlations available in the literature.

A multivariable control strategy based on fuzzy logic interference rule for a solar-driven, direct air-cooled H[formula omitted]O-LiBr absorption chiller

The operation of a solar-driven H2O-LiBr Absorption Chiller (AbC) is subjected to various limitations regarding its ability to satisfy efficiently the required cooling demand while avoiding certain internal conditions, such as H2O-LiBr solution crystallization and water freezing. These circumstances would lead to problematic situations and jeopardize the continuous operation of the system. Thus, the development of accurate control strategies is an issue of interest. A new operational control strategy approach is introduced and tested through simulation studies, by employing a transient model of the entire solar cooling application. A prototype under development is used for the parametrization of the direct air-cooled AbC model used in the simulations. The developed control strategy aims to minimize the electrical consumption of the auxiliary components of the AbC (i.e., fan, pumps) during the partial load operation period, by using a fuzzy logic interference rule for determining the cooling capacity demand and then applying an optimization algorithm for determining the velocity of the auxiliary components. Within the proposed control strategy, a fast-calculation model is embedded, which predicts the chiller’s capacity under variable external conditions and partial load operation. The electrical COP is increased up to 2.2 times with respect to a baseline case, based on a basic two-step control strategy, while allowing the chiller to operate smoother, minimizing the crystallization and freezing risk.

Performance characteristics of a hybrid absorption chiller driven by exhaust gas and cooling water from a gas engine

Performance characteristics of a hybrid absorption chiller driven by exhaust gas and cooling water from a gas engine

The Prospect of Using Membrane Devices for Cold Production as an Alternative to the Absorption Refrigerating Installation

The Prospect of Using Membrane Devices for Cold Production as an Alternative to the Absorption Refrigerating Installation

Experimental research of a novel binary solution for diffusion absorption cooling systems

AbstractThe diffusion absorption refrigeration (DAR) systems are driven by heat and utilize a binary solution along with an inert gas as the working fluid. In commercial applications, the choice of binary solutions operating with an auxiliary gas is typically limited to ammonia‐water or water‐lithium bromide combinations. The focus of this study is to explore the viability of using tetrafluoropropene (R‐1234yf, an HFO refrigerant) as the refrigerant, dimethylacetamide (DMAC) as the absorbent, and helium as the auxiliary gas. As the thermodynamic properties of this specific binary solution are yet to be studied, experimental investigations are conducted to obtain these properties. The results allow the establishment of the pressure‐temperature and concentration relationships and determine the mixture‘s enthalpy for various temperatures. Subsequently, both numerical and experimental analyses of the diffusion absorption system are performed. The experimental findings show that, under certain concentrations of the components and with appropriate heat input, temperatures in the evaporator reached below 0 °C. However, the system exhibits low coefficient of performance values, high generation temperatures, and overall inefficiency, suggesting that this particular binary solution may not be well‐suited for diffusion absorption cooling systems.

Study on the thermodynamic performance of solar absorption refrigeration combined with a ‘seasonal cold storage’ system

Inter-seasonal thermal storage technologies are focused on storing and transitioning abundant solar energy from summer to winter for heating, often ignoring the fact that abundant cold energy in winter can also be transferred to summer for cooling. In this paper, a novel solar absorption refrigeration combined with a ‘seasonal cold storage’ system is proposed to store abundant ambient cold energy in the form of chemical potential in winter and is utilized to discharge energy for refrigeration in summer. Moreover, based on the thermophysical properties of LiBr/H2O, LiBr-[BMIM]Br/C2H5OH and LiBr-[BMIM]Cl/CH3OH, the thermodynamic performances under various operating conditions were calculated via MATLAB. The results show that the system using LiBr-[BMIM]Cl/CH3OH obtained a larger energy storage density of 339.22 kJ·kg−1 below the ice point without freezing compared to traditional ice storage. The systems using LiBr-[BMIM]Br/C2H5OH and LiBr-[BMIM]Cl/CH3OH achieved higher coefficients of performance of 0.94 and 0.90, respectively. Moreover, the generation temperature of the system using both the ternary working pairs was below that of LiBr/H2O by more than 5 K, which was beneficial for enhancing the utilization of solar energy and saving the collector area. Overall, this new system using LiBr-[BMIM]Cl/CH3OH exhibited the shortest payback period of 2.73 a, with considerable economic benefits.

CONCENTRATION OF NANO FLUID/BASE FLUID SUSPENSION ENHANCE SURFACE CHARGE WITH PH STABILITY FOR LOW TO MEDIUM TEMPERATURE PHASE CHANGE MATERIALS

Zeta potential and poly-dispersivity are used to characterize the samples that is obtained using absorption refrigeration system for low to medium temperature phase transition materials. Salicyclic acid, Benzanilide, Hydroquinone, Potassium thiocyanates, D-mannitol, Alunimium oxide, Iron oxide, and ZnO active concentration with base fluid, aspects including the influence of the PCMs property based on their phase transition mutual interaction are explored. In order to comprehend their behavior and improve their performance, functional materials synthesis and characterization depend heavily on the isoelectric point. Understanding the material surface charge role of the medium's pH stability to the many liquid-phase procedures involved in the synthesis of materials, since it conduct the processes like agglomeration, coagulation, peptization to form solid particles materials. Zeta potential measure, which commonly use concentration of volume fraction methods, electrophoretic migration techniques, are hence a valuable source of data.

Design of Excellent Mechanical Performances and Magnetic Refrigeration via In Situ Forming Dual-Phase Alloys.

Magnetic refrigeration technology can achieve higher energy efficiency based on the magnetocaloric effect (MCE). However, the practical application of MCE materials is hindered by their poor mechanical properties, making them challenging to process into devices. Conventional strengthening strategies usually lead to a trade-off with refrigeration capacity reduction. Here, a novel design is presented to overcome this dilemma by forming dual-phase alloys through in situ precipitation of a tough magnetic refrigeration phase within an intermetallic compound with excellent MCE. In the alloy 87.5Gd-12.5Co, incorporating the interconnected tough phase Gd contributes to enhanced strength (≈505MPa) with good ductility (≈9.2%). The strengthening phase Gd simultaneously exhibits excellent MCE, enabling the alloy to achieve a peak refrigeration capacity of 720 J kg-1. Moreover, the alloy shows low thermal expansion induced by the synergistic effect of the two phases. It is beneficial for maintaining structural stability during heat exchange in magnetic refrigeration. The coupling interaction between the two magnetic phases can broaden the refrigeration temperature range and reduce hysteresis. This study guides the development of new high-performance materials with an excellent combination of mechanical and magnetic refrigeration properties as needed for gas liquefaction and refrigerators.

Design of solar thermal absorption air conditioning system using CO2 with synthetic building load

Traditional air conditioning and refrigeration solutions rely on compressor-driven systems, leading to increased electricity consumption and intensified greenhouse gas (GHG) emissions. These systems primarily utilize synthetic refrigerants such as CFCs, HCFCs, and HFCs. Despite their advantages, these refrigerants are either banned or subject to restricted permissions under the Montreal Protocol (1987) and the Kyoto Protocol (1997) due to environmental concerns. According to the Paris Accord, ratified by 196 parties as of 2017, there is a global shift towards low global warming refrigerants and eco-friendly alternatives. COP27 reaffirmed global commitments to limit temperature rise to 1.5 °C, emphasizing urgent action and stronger climate plans to combat global warming. CO2 envisaged by ASHRAE is resurrected as a promising natural refrigerant with the advent of high-pressure technologies the design employs a solar evacuated glass tube collector (EGTC) with U-shaped copper tubes and flat plate collector (FPC) to harness solar thermal energy. An immersed heat exchanger's (HX) based thermal storage tank is incorporated to address the intermittency of solar energy. The CO2 refrigerant offers advantages over other natural refrigerants due to its low critical point.This research conducts a TRNSYS® simulation of a 35.2 kW absorption cooling system with synthetic building load driven by energy captured through FPC and EGTC using R-744, additionally supported by a supplementary boiler for traditional office timing. The system design comprises two solar collectors, the EGTC and FPC, integrated with two different cooling loop configurations (C1 and C2). In C1, the hot water that exits the generator of the absorption chiller is forwarded toward the immersed HX-based hot storage tank, which is connected to the solar and absorption cooling loop. In C2, the working fluid leaving the absorption chiller is diverted directly toward the auxiliary boiler/furnace, if the temperature in the storage tank falls below the necessary level (108.89 °C) and if the tank temperature is greater than this set point temperature, then the flow passes through the storage tank. Both system designs have been developed using TRNSYS, with dynamic simulations conducted throughout the summer.The solar fraction and collector efficiency are considered as key performance indicators to evaluate and compare the system's effectiveness. Then the optimization of system parameters is performed for all four cases (EGTC C1 & C2 and FPC C1 & C2) based on these key performance indicators, all configurations integrated with a fixed synthetic building cooling load. The optimum parameters are found for all four cases, and the optimum parameters for EGTC C1 & C2 are 100 m2, 4 m3, and 11° for collector area, storage tank volume, and collector slope respectively. Similarly, for FPC based configurations, these parameters are 200 m2, 32 m3 for C2 and 4 m3 for C1, and 20° respectively. The results revealed better C2 performance than C1, with EGTC outperforming FPC. The final results were computed for the EGTC based designs due to their high solar fractions, with EGTC C2 emerging as the optimal configuration, achieving a seasonal solar fraction of 0.649.

Thermodynamic investigation of an innovative solar-driven trigeneration plant based on an integrated ORC-single effect-double lift absorption chiller

Maximizing the synergy between renewable resources and efficient multi-generation systems is crucial for transitioning the energy sector towards carbon-free production. The objective of this research paper is to investigate and optimize the performance of an integrated solar trigeneration plant. Electrical load and domestic heating supply are provided through an organic Rankine cycle and heat exchanger respectively. Cooling needs are provided using a single-effect double-lift absorption chiller (SE-DL ACH), a novel combination seldom encountered within multigeneration systems. Various collectors are evaluated, and an initial screening of organic fluids is done. A comprehensive analysis framework is developed, considering energy, exergy, and the sequence of energy usage, which is clarified into sequential (SSI) and parallel (PSI) integration.The final result indicates that n-decane is the most appropriate fluid, yielding thermal and electrical efficiencies of 11.93 % and 5 kW, respectively. Among the collectors evaluated, EFPC emerges as the most promising. SSI delivers electrical, cooling, and heating output of 5 kW, 105.7 kW, and 29.25 kW, with energy and exergy efficiencies of 45.6 % and 41.3 %. PSI demonstrates an improvement of 11.92 % and 43.08 % in cooling and heating generation. It exhibits an energy and exergy efficiency of 43.03 % and 37.26 %. Integrating the SE-DL parallel to the heat source has improved the potential of heat recovery by 22.22 %.

Determination of operating temperature in main generator of a two-stage absorption refrigeration machine working on an aqueous solution of lithium bromide

This paper examines the thermal characteristics of a two-stage absorption refrigeration machine. When carrying out a numerical analysis, it turned out that the secondary generator’s temperature was not constant, and it was also found that the coefficient of thermal performance of this cycle increased significantly at the beginning, then stabilized at a certain value for the temperature degree of the primary generator. But this result is not the right value for calculating the absorption refrigeration cycle; it might cause crystallization inside the cycle and This was verified based on the thermodynamic relationship chart (h-X-T) for LiBr-water solution. In addition, the decisive point for determining the appropriate temperature is to study the change in refrigeration capacity in the process when the temperature of the generator changes. In this case, the design temperature for the primary generator should be in the range between the temperature corresponding to the highest refrigeration capacity and the temperature far from the crystallization phenomenon.

Novel design of a CCHP system to boost nearly zero-carbon building concept

The accumulation of carbon dioxide in the atmosphere is responsible for global warming. To address this issue, this study develops and optimizes a novel and economically viable combined cooling, heating, and power (CCHP) system for an educational building with minimal CO2 emissions. The main components of the system include a gas turbine cycle, a molten carbonate fuel cell, a heating system, an electric chiller, and an absorption chiller. Optimization is conducted based on a 4E (energy, exergy, economic, and environmental) analysis using TRNSYS and MATLAB software. The optimized CCHP system has a unit product cost of $52.44/h with an overall exergy efficiency of 44.34 %, generating 0.39 kg of CO2/kWh. Furthermore, the objective of a nearly zero-carbon system is achieved by integrating carbon capture and storage (CCS) into the original CCHP system. A novel cryogenic carbon capture unit is implemented to capture CO2 from the flue gas. Integrating CCS reduces CO2 emissions by up to 91 %, presenting a cost-effective approach to carbon offset. Although there is a modest increase in operational costs ($53.46/h) and a slight decrease in exergy efficiency (43.3 %), these trade-offs are necessary to attain an environmentally responsible system. Overall, the optimized CCHP system with the integrated CCS shows potential as an energy-efficient solution for the selected educational building while reducing CO2 emissions.

Novel working fluid pair of methanol/betaine-urea for absorption refrigeration system driven by low-temperature heat sources

An absorption refrigeration system (ARS) designed for low-temperature heat sources like industrial waste heat, solar-heated water, or geothermal heat can offer substantial energy-saving benefits. This study explores a novel working fluid pair comprising methanol and betaine-urea (BE-UR), forming a deep eutectic solvent (DES) system. This design capitalizes on methanol's high enthalpy of vaporization, the low heat capacity of the working pair, and the appropriate intensity and strength of the hydrogen bonding network within the solution. The proposed fluid pair shows full solubility of BE-UR in methanol at a mole ratio of 1.81 to 1 (methanol to BE-UR), with an equilibrium vapor pressure dropping to 8.59 kPa at 303.15 K. Molecular dynamics simulations unveil a microscale solution structure, showcasing a hydrogen bond network and unbonded methanol in the concentrated working fluid pair. This configuration enhances the absorption process of methanol vapor in the ARS absorption unit. Aspen Plus simulations predict a coefficient of performance (COP) exceeding 0.85, comparable to H2O/LiBr in single effect-ARS and outperforming NH3/H2O in SE-ARS by approximately 30 %, while maintaining a lower cycle ratio of about 2.

AbSolut - Integration of Absorption Technologies in District Heating and Cooling Systems for Enhanced Economic and Ecological Impact

District heating (DH) systems play a crucial role in meeting heating demands across the European Union (EU) and Austria, with significant potential for energy efficiency improvements and decarbonization. However, the transition towards climate neutrality by 2040 poses significant challenges, particularly in decarbonizing existing DH systems and integrating renewable energy sources. This work explores the application of absorption technologies, specifically absorption heat exchangers (AHX), absorption chillers (AC), and absorption heat pumps (AHP), in optimizing DH systems. The study investigates the utilization of AHX as transfer substations to increase heat capacity within existing grids by up to 30%, facilitating the integration of renewables and reducing distribution heat losses. Additionally, AC implementation for cooling supply demonstrates efficiency improvements through dynamic operation modes, renewable energy integration, and reduced electricity demand. Furthermore, AHP for waste heat utilization in DH power plants showcases environmental benefits, cost savings, and enhanced energy security. Through detailed techno-economic analyses and case studies, the paper evaluates the viability and economic feasibility of absorption technologies in DH applications. Challenges such as system integration, spatial requirements, and driving energy optimization are addressed, offering insights into overcoming barriers to adoption. Overall, the research highlights the transformative potential of absorption technologies in enhancing the efficiency, sustainability, and resilience of DH systems. By leveraging these technologies, DH operators and stakeholders can navigate the transition towards climate neutrality, while ensuring reliable and cost-effective heating and cooling solutions for urban areas.

ИНТЕНСИФИКАЦИЯ КОНДЕНСАЦИИ ХЛАДАГЕНТА В ПАРОВОЙ КОМПРЕССОРНОЙ ХОЛОДИЛЬНОЙ УСТАНОВКЕ

An option is considered to intensify the condensation of refrigerant in an ammonia refrigeration unit by increasing the heat transfer coefficient to a cold coolant and the heat transfer coefficient with an acceptable increase in the hydraulic resistance of the condenser

EXERGOECONOMIC ANALYSIS OF A HYBRID SYSTEM OF WASTE INCINERATION AND ABSORPTION REFRIGERATION

The current global scenario presents a significant increase in energy demand for HVAC-R (Heating, Ventilation, Air Conditioning and Refrigeration) systems. Considering also that Brazil has the sixth most expensive energy in the world and that there is currently a greater scarcity of natural resources for energy generation, it is necessary to seek viable alternatives with lower energy consumption to the currently most used models, without any quality loss. On the other hand, absorption refrigeration and waste incineration systems can be lines of studies and research to be considered, considering that it is possible to reduce electrical energy consumption and also the environmental impacts that the usual compression refrigeration systems provide. . . In this context, one of the segments of Thermal Systems Engineering studied is the exergoeconomic analysis that comprises the concepts of Heat Transfer, Fluid Mechanics and Thermodynamics, based on the Second Law of Thermodynamics and which uses the notions of optimization and economic analysis. Therefore, this work aims to perform an exergoeconomic analysis of a hybrid system of waste incineration and absorption refrigeration, with the specific objective of developing an exergoeconomic model for the hybrid system. Absorption incinerator-refrigerator. This is an exploratory bibliographic research using an absorption refrigerator from the Center for Research and Development of Self-Sustainable Energy (NPDEAS) of the Federal University of Paraná, in which a model was made with a macroscopic approach of the mass and heat transfer phenomena of a absorption refrigeration cycle, applying the principles of conservation of mass and energy in steady state for each component of the cycle, that is, each component will be considered as a single control volume. It is expected that it will be possible to predict the behavior of the absorption refrigeration system and that it will be possible to develop a scientific analysis tool to design, control and optimize absorption refrigeration systems, using waste incineration. The highest exergy destroyed was verified in the desorber with about 0.9461 kW and through the exergoeconomic analysis of the incinerator, it was found that the cost rate associated with the product of the incineration gases was $ 39,926.31 per year.

Theoretical study of a novel intermediate temperature photovoltaic/thermal system equipped with heat pipe and evacuated tube

Solar photovoltaic/thermal (PV/T) technology has enormous promise in the field of renewable cogeneration as a key technology to increase the utilization rate of solar energy. The structural restrictions of PV/T and the high power temperature coefficient of solar cells make PV/T mostly used in low-temperature situations. However, the combination of intermediate temperature PV/T and low-grade energy utilization devices can create a wider range of application values, including absorption refrigeration, seawater desalination, and the organic Rankine cycle. To increase the overall efficiency and thermal energy grade of the PV/T system, a novel heat pipe evacuated tube PV/T (HE-PV/T) system is proposed. The heat transfer is modeled using distributed parameters, and the thermoelectric performance and temperature uniformity are computed through numerical simulation. The impacts of different parameters on the thermodynamic performance of the HE-PV/T system are examined. Compared with traditional flat plate PV/T, the system's overall energy utilization efficiency and exergy efficiency have been significantly increased. When the inlet temperature is 80.0 °C, the overall energy and exergy efficiency of the HE-PV/T system can reach 33.55 % and 7.92 %, which is 29.66 % and 21.97 % higher than that of flat plate PV/T. Besides, the temperature distribution of the HE-PV/T is more uniform, which is beneficial for reducing thermal stress and mechanical damage. The property superiority and thermodynamic feasibility of the HE-PV/T system at medium temperature are demonstrated.