Compression Cycle Research Articles

Sandwich-structured graphene composite sponge with multiple cyclic compression for waste liquid treatment under dynamic electrical stimulation response

3D porous graphene nanosponge has broad application prospects in intelligent sensing, wastewater treatment, environmental remediation and other fields. However, the previously reported graphene-based 3D structure sponge column usually has difficulty achieving compression resistance and excellent adsorption effect. In this study, a novel, simple and low-cost sandwich structure is assembled. The carbon fiber/reduced graphene oxide/polydimethylsiloxane (CF/rGO/P) with excellent compression electrical properties is used as the intermediate layer, and the flexible polyvinylidene fluoride/rGO/P (PV/rGO/P) is used as the upper and lower layers. A composite assembled graphene sponge column with outer pressure resistance and middle compression resistance is prepared. Results show that this composite sponge has a small resistance(30–100 Ω/cm). Under 60% compression deformation, the resistance sensitivity could reach 36.44. The physical adsorption of methylene blue (MB) dye has reached more than 93.7% after 24 h, and the electrochemical adsorption rate is 3.12 times faster than the physical adsorption rate. This sandwich assembly structure exhibits an excellent positive synergistic effect, maintaining high adsorption and desorption properties for MB dyes under high compression cycles. It can be applied to the recovery of cationic dyes in the dynamic flow waste liquid, thereby broadening the application of hydrogel graphene nanosponge in the field of environmental protection.

Simple preparation superhydrophobic melamine sponge via one-step emulsion polymerization for continuous oil/water separation in harsh environment

The oil spill and industrial oily wastewater in large quantities has caused severe harm to the environment and human health, which make an urgent requirement to develop low-cost, eco-friendly, stable performance and highly efficient oil/water separation materials. Herein, a superhydrophobic/superlipophilic melamine sponge with excellent hydrophobic stability was successfully fabricated via one-step emulsion polymerization. During polymerization, trimethylolpropane triacrylate (TMPTA) and polyethylene imine (PEI) form robust microspheres, and polydimethylsilane (PDMS) cross-links to form hydrophobic coating on the original sponge skeleton. The modified sponge could continuously separate various immiscible oil/water mixtures under harsh conditions (including strong acids, strong bases, salts). Even after 10 consecutive cycles, the separation efficiency for toluene and petroleum ether exceeds 99.87%. In addition, the as-prepared sponge exhibited extraordinarily high oil absorption capacities (with a maximum saturated oil absorption of 107.31 g/g for chloroform) and excellent reversible compressibility (up to 100 compression cycles). More importantly, the pore size of modified sponge was adjusted through a simple mechanical compression strategy so that the compressed sponge met the particle size screening requirements to effectively separate the surfactant-stabilized water-in-oil emulsions. Based on the simple preparation protocol, fluorine-free raw materials, and excellent properties, the MS-TMPTA/PEI-PDMS sponge presented here have extremely promising application potential in oil/water separation.

All-Nanochitin-Derived, Super-Compressible, Elastic, and Robust Carbon Honeycombs and Their Pressure-Sensing Properties over an Ultrawide Temperature Range.

Elastic carbon aerogels show great potential for various applications but are often hindered by structure-derived fatigue failure, weak elasticity with low compressibility, and low stress and height retention. Herein, we demonstrate a super-elastic and fatigue-resistant nanochitin-derived carbon honeycomb with honeycomb-like anisotropic microstructures and carbon-based molecular structures, which was tailored by optimizing the nanochitin concentrations and carbonization temperatures. The carbon honeycomb fabricated at a nanochitin concentration of 1.0 wt % and a carbonization temperature of 900 °C demonstrated anisotropic honeycomb channels, nanofibrous network channel walls with few cracks, and weak interactions between the carbonized nanochitin, which afforded high compressibility with up to 90% strain and complete recovery. In particular, the carbon honeycomb provided good fatigue resistance with high stress and height retentions of 87 and 94%, respectively, after more than 10,000 compression cycles at 90% strain. Moreover, the tailored anisotropic honeycomb channels and molecular structures endowed the carbon honeycomb with elasticity even under severe conditions, such as exposure to flame (approximately 1000 °C) and liquid nitrogen (approximately -196 °C). Owing to these properties, the nanochitin-derived carbon honeycomb could act as a high-sensitivity pressure sensor for a wide working pressure range of 0-185.5 kPa and ultrawide temperature range of -196-600 °C. This study can provide a promising route to develop all-biomass-derived, super-elastic, and fatigue-resistant carbon materials for pressure sensing under harsh conditions and for versatile electronic applications.

Integrated design optimization method for novel vapour-compression-cycle-based environmental control systems

The aircraft Environmental Control System (ECS) is the primary consumer of non-propulsive power at cruise conditions, hence, its performance optimization is crucial for the reduction of specific fuel consumption. A novel integrated system design optimization method is presented: thermodynamic cycle, component sizing and working fluid are taken into account simultaneously. This method was applied to the ECS of large rotorcraft based on a Vapour Compression Cycle system electrically driven by a high-speed centrifugal compressor. Steady-state and lumped parameter system component models have been developed using the Modelica acausal modelling language. The optimization design framework consists of an in-house code, featuring a Python-Modelica interface. The study case refers to a critical operating condition: the helicopter is on the ground during a hot and humid day. The working fluid is R-134a. The multi-objective optimization targets the maximization of the system efficiency and the minimization of system weight. The results show that more efficient systems can be designed only with heavier components. The design feasibility of high-speed centrifugal compressors is demonstrated. The advantage of an integrated system design optimization framework for complex energy systems is proved, allowing for the analysis of the impact of both component design and working fluid on system performance.

Efficiency assessments of a compound cooling system for low-humidity applications

Present work introduces the utilization of a concentric vertical pipe heat exchanger for indirect evaporative cooling. The device is coupled to a heat pump cooler, i.e., vapour compression cycle, as a pre-cooler and pre-dehumidifier of outdoor fresh air, to reduce the cooling load exerted on the evaporator. The proposed configuration borrows concepts from cooling tower operation, which enables the recirculation of room exhaust air, stabilizing its temperature before purging, also reducing the thermal load exerted over the condenser. An experimental analysis of the setup was performed, obtaining an average temperature drop, between intake and exhaust, of ∼ 10 °C. Against standalone configuration, this resulted in a 19%, and 29%, decrease of the cooling load, and required electrical input, respectively. Moreover, the inclusion of the indirect evaporative cooling setup reduced operation time by ∼ 40%; from 36 to ∼ 18 min per hour, resulting in long-term economic savings between 41 and 44% against stock energy consumption. Based on the surplus of energy achieved, this paper conducts a redesign and optimization of the heat exchangers. Through an inverse heat transfer approach, the device footprint can be reduced between 35.8 and 38.9% in terms of its weight, and 45.5 to 44.4% in terms of its surface area; features particularly useful when it comes to limitations in structural load capacity and/or space availability. The conducted redimensioning analysis revealed initial investment savings, between 36.2 and 39.7% of total cost, which albeit lower than operational-related savings, are still comparable when it comes to the design and operation of an air handling unit. Based on obtained results, the integration of the proposed setup does enhance the performance of the stock heat pump cooler, without increasing overall energy expenditure costs, thus is presented as an affordable, retrofittable, option for air conditioning systems operating in arid and semi-arid climates.

Highly Flexible, Self-Bonding, Self-Healing, and Conductive Soft Pressure Sensors Based on Dicarboxylic Cellulose Nanofiber Hydrogels.

Conductive hydrogels have gained a great deal of interest in the flexible electronics industry because of their remarkable inherent properties. However, a significant challenge remains for balancing hydrogel's conductivity, self-healing, and strength properties. Herein, double network ionic hydrogels were fabricated by concurrently introducing borax into dicarboxylic cellulose nanofiber (DCNFs) and polyacrylamide (PAM) hydrogels. The incorporation of borax provided a superabsorbent feature to the PAM/DCNF hydrogels (without borax) with the equilibrium water absorption rate increased from 552 to 1800% after 42 h. The compressive strength of the prepared hydrogel was 935 kPa compared to 132 kPa for the PAM hydrogel, with high cycling stability (stable after 1000 compression cycles with 50% strain). The hydrogel pressure sensor had a very sensitive response (gauge factor = 1.36) in the strain range from 10 to 80%, which made it possible to detect mechanical motion accurately and reliably. The developed hydrogels with high-performance, environmentally friendly properties are promising for use in future artificial skin and human-machine interface applications.

Wood-inspired elastic and conductive cellulose aerogel with anisotropic tubular and multilayered structure for wearable pressure sensors and supercapacitors

Cellulose nanofiber (CNF) aerogels hold considerable potential in wearable devices as pressure sensors and flexible electrochemical energy storage. However, the undirectional assembly of CNFs results in poor mechanical performance, which limits their application in structural engineering. In this study, we propose an anisotropic aerogel with both elastic and conductive properties inspired by the micro-nanostructure of natural wood. One-dimensional TEMPO cellulose nanofibers (TOCNF) were utilized as structural building blocks, while two-dimensional reduced graphene oxide (rGO) served as the electron transfer platform, owing to their high mechanical strength. The directionally aligned tubular structure composed of multilayered sheets was formed through rapid unidirectional freezing and subsequent steam heating reduction. These structures efficiently transferred stress throughout the porous skeleton, resulting in TOCNF-rGO aerogels with high compressibility and excellent fatigue resistance (2000 cycles at 60 % strain). The aerogel also exhibited high sensitivity, wide detection range, relatively fast response, and excellent compression cycle stability, making it suitable for accurately detecting various human biological and motion signals. Additionally, TOCNF-rGO can be assembled into a flexible all-solid-state symmetric supercapacitor that delivers excellent electrochemical performance. It is expected that this biomass-derived aerogel will be a versatile material for flexible electronic devices for energy conversion and storage.

CO2 reverse cycles equipped with a bladeless turboexpander

Efficient and resilient chiller cycles at MW-scale are often needed in industry, and the growing interest in energy communities and electrification has increased attention to reverse cycle performance also in their utilisation as heat pumps.This work evaluates the optimal thermodynamic performance and economic features of CO2 refrigeration cycles comparing several layouts adopting a lamination valve (or expansion valve), an ejector and a bladeless (or Tesla) turboexpander, at various cold-source temperatures and refrigerant pressure levels. Carbon dioxide is a favourable substitute for traditional refrigerants, thanks to its low global warming potential (GWP) and adequate thermophysical properties. Tesla turboexpanders are a promising technology as small-scale machinery for energy harvesting, thanks to their low sensitivity to downscaling effects while retaining high rotor efficiency. The beneficial effect of introducing such an expansion device with respect to conventional base layout and state-of-the-art ejector layout was assessed. Simulations were conducted using and improving the existing WTEMP-EVO modelling tool.The results show that the use of a Tesla expander provides benefits in terms of augmented coefficient of performance (COP) in a range between 8% and 22%, depending on the cycle layout and cold-source temperature; moreover, thermo-economic analysis shows a lower specific cost for turboexpander layouts, while economic optimisation ensures lower specific costs for both simple compression and two-stage intercooled compression cycles, at the expense of a slightly reduced COP.

Experimental analysis on the structural seismic behavior of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting

The structural seismic performance of steel frame-precast steel reinforced concrete (SRC) infill wall with lateral force resisting is analyzed, and the structural strength of steel frame-precast SRC infill wall with lateral force resisting is improved. The structural seismic performance optimization model of SRC lateral force resisting wall based on buckling restrained brace is proposed. Through the finite element simulation software, the seismic performance and response results of ordinary steel frames, buckling restrained braced steel frames and a relatively new type of sacrificial-energy dissipation braced steel frames under earthquake are compared and analyzed to demonstrate the applicability and performance advantages of sacrificial-energy dissipation braced steel frames in the steel frame braced structure system. Under the action of horizontal earthquake, the supporting members experience reciprocating axial tension and compression cycles, which dissipate a large amount of seismic energy input into the structure. Therefore, the buckling restraint support method can be used in the structure to improve the support strength. Under horizontal reciprocating load action of earthquake, the ability to consume seismic energy through self-hysteresis of the brace is poor. Experimental research shows that, the unbalanced force formed in the beam of the frame beam under seismic action will form a plastic hinge at the beam end at both ends of the frame beam. Especially when the brace is buckling unstable and the stiffness of the frame beam is small, the plastic hinge effect at the beam end is significant. This phenomenon may cause damage to the frame beam or even local floor subsidence. The buckling restraint support has a full hysteresis area under axial tension and compression, and its mechanical performance is excellent. It is obviously superior to ordinary steel bracing in energy dissipation capacity and seismic performance. It can accurately predict the bearing capacity of reinforced concrete under strong earthquake, and the energy dissipation distribution is more in line with the requirements of “energy seismic design method”.

Theoretical and experimental study on the selection of pure and mixed refrigerants for a power-cooling system driven by ultra-low-grade heat

This study theoretically and experimentally evaluates the performance of a system that combines an organic Rankine cycle (ORC) and a vapor compression cycle (VCC) driven by ultra-low-grade heat (ULGH). A systematic method is developed for the selection of pure refrigerants for the efficient performance of ORC over a temperature range between 50°C to 100°C. Binary and ternary mixtures are developed followed by sensitivity analyses and composition optimization to determine the optimal performance of these mixtures. Several experimental tests are conducted to ensure the operability of the system with the developed refrigerants. The results show that the use of ternary and binary mixtures enhances the performance of the system with lower GWP and ODP compared to pure refrigerants. Several mixtures are developed with energy efficiencies higher than 9% at a heat source temperature of 75°C. A mixture of R142b/R152a/R600 improves the energy efficiency of the system by 22.80%, reduces the back work ratio by 19.40% with an increase in the evaporation capacity by 13.25%. The methodology and results presented herein will be useful in the development, design, and optimization of power and cooling systems driven by ULGH with pure and mixed refrigerants.

The performance of shallow GSHP in buildings for heating and cooling: A case study in Jordan

The versatility of heat pump technology in heating and cooling applications is attracting much attention. Thanks to its great efficiency and inexpensive capital and operating expenses, it has found widespread use. One major downside was a sharp decline in heat output and COP as outside temperatures fell. When calculating the COP of such devices, ambient temperature is a major factor. According to studies done in the past, working in a comfortable temperature range is much better than doing so in extreme heat or cold. The ambient conditions near the surface are more stable and less prone to fluctuations than the air temperature at the surface. In this study, we compare the efficiency of two different working fluids (R134a and R290) in an ideal vapor compression cycle when operating at subsurface (-2 m) ground temperature and at the temperature of home water wells in northern Jordan. The heating and cooling modes are the focus of this research. The proposed system is mathematically modeled, validated, and solved. The results show that the heat pump's efficiency improves by 10% to 11.2% during the colder months. Meanwhile, summertime improvements ranged from 9.8% to 27.4%. Last but not least, R290 refrigerant could replace R134a if the risk of ignition is considered.

Prediction of the tensile strength of tablets using LSTM networks on compression profiles

This publication's objective was to predict the tensile strength of tablets using an analysis of process data comprising compression pressure, sampling timestamps, and punch positions. A recurrent neuronal network, specifically designed with Long Short-Term Memory layers, was utilized to accommodate the time-series characteristics of the data. A dataset from 344 tablet compression cycles was employed for model training, after which the model demonstrated a predictive ability with a coefficient of determination of 0.954 on test data from 804 tableting cycles. The foundational database incorporated data from both pure substances and mixtures consisting of up to four components compressed at various compression pressures and with three different tablet masses. Interestingly, the prediction errors did not exhibit any significant correlation with specific materials, mixtures, maximum compression pressures, or tablet weights. With the aid of the model, it was possible to calculate the entire tabletability profile of twelve substances from just a single compression process each. Models of this nature bear promising potential for future application in the research and development of formulations as well as in production processes to predict tensile strength.

Experimental evaluation of a vapor compression cycle integrated with a phase change material storage tank based on two strategies

In this survey, the integration of a vapor compression cycle with a phase change material (PCM) storage tank has been evaluated experimentally during the hottest days of five cities with different weather conditions: Tehran, Ramsar Hamedan, Bushehr, and Ahvaz. The temperature conditions for outdoor (condenser, compressor, etc.) and indoor (evaporator) air conditioning units are provided with the help of two separated test chambers and a controller system. The desired system has been examined based on two scenarios. In each scenario, the system is assessed for the conventional air conditioning (AC) system (with no PCM involved) and the AC plus PCM unit. Based on scenario 1 operating strategy, the results indicate that adding the PCM tank decreases the total daily COP compared to the conventional AC unit, which varies from 32.07% for Bushehr city to 17.23% for Tehran city. Whereas the AC plus PCM system’s performance enhances during on-peak hours compared to the conventional AC system, which varies from 65.99% for Hamedan city to 12.84% for Bushehr city. Based on scenario 2 operating strategy, adding the PCM storage tank to the conventional AC unit increases total electric energy consumption over 24 h, which varies from 29.35% for Bushehr city to 5.49% for Tehran city. While it leads to shaving the electric peak load from 45.11% to 67.02% in which the highest peak load shaving belongs to Tehran and the least is related to Bushehr city.

Exergoeconomic and environmental analyses of a geothermal-powered tri-generation system: A study of CO2 emission reduction

A geothermal-powered tri-generation system is presented and discussed from thermodynamic, exergoeconomic, payback period, extended-environmental, and exergoenvironmental perspectives. The designed system consists of an organic flash cycle assisted by a two-phase ejector and a vapor compression cycle that utilizes a zeotropic working fluid of Isobutane/Pentane. To further recover waste heat, an electrolyzer unit is utilized as a subsystem for producing H2. All the system outputs except for the exergoenvironmental index and exergoeconomic factor reach the highest point when the mass fraction of Pentane increases. According to a parametric study, the greatest variations in system products are related to changes in the flash tank temperature. Furthermore, the system outputs indicate a non-linear relationship with the mass fraction of Pentane. The temperature of evaporators has a substantial influence on the system's cooling capacity. Meanwhile, the remaining output parameters remain steady or show minor changes. By increasing the flash tank temperature, the costs related to electricity, cooling, and H2 all decreased before gradually increasing. The two-phase ejector has the highest exergy destruction rate because of the energy lost in the mixing process.

Self-strengthening and conductive cellulose composite hydrogel for high sensitivity strain sensor and flexible triboelectric nanogenerator

Triboelectric nanogenerators (TENGs) as promising energy harvesting devices have gained increasing attention. However, the fabrication of TENG simultaneously meets the requirements of green start feedstock, flexible, stretchable, and environmentally friendly remains challenging. Herein, the hydroxyethyl cellulose macromonomer (HECM) simultaneously bearing acrylate and hydroxyl groups was first synthesized and used as a crosslinker to prepare the chemically and physically dual-crosslinked cellulose composite hydrogel for an electrode material of stretchable TENG. Meanwhile, the in-situ polymerization of pyrrole endowed the hydrogel with satisfactory conductivity of 0.40 S/m. More impressively, the synergies of the cellulose rigid skeleton and the construction of the dual-crosslinking network significantly improved the mechanical toughness, and the hydrogel exhibited excellent self-strengthening through cyclic compression mechanical training, the self-strengthening efficiency reached 124.7 % after 10 compression cycles. Given these features, the hydrogel was used as wearable strain sensors with extremely high sensitivity (GF = 3.95) for real-time monitoring human motions. Additionally, the hydrogel showed practical applications in stretchable H-TENG for converting mechanical energy into electric energy to light LEDs and power a digital watch, and in self-powered wearable sensors to distinguish human motions and English letters. This work provided a promising strategy for fabricating sustainable, eco-friendly energy harvesting and self-powered electronic devices.

Multifunctional elastic aerogels of nanofibrous metal−organic framework for thermal insulation and broadband low-frequency sound absorption

Generally, porous materials are good candidates for sound absorption and thermal insulation. However, low sound absorption coefficient under 1000 Hz, low mechanical stability and poor consistency of performance hinders the wide applications of porous materials. In this study, we develop a kind of aerogel (PAN@ZIF-8-Kevlar aerogel) with well-designed hierarchical and tortuous porous structures to consume the low-frequency sound, hinder thermal transmission. The sound absorption coefficient of the PAN@ZIF-8-Kevlar is as high as 0.99 at 500Hz; average sound absorption coefficient of the material at 250, 500, 750, and 1000 Hz reaches 0.73. In addition, the thermal conductivity of PAN@ZIF-8-Kevlar is similar to that of air, thermal conductivity is near that 24.61 mW m−1 K−1. Notably, the PAN@ZIF-8-Kevlar aerogels also exhibit durable and stable cycling performance. The material retains its structural stability and retains its original low frequency sound absorption properties after 500 compression cycles. The hydrophobic material provides them with good moisture resistance (the water contacts angle (WCA) of PAN@ZIF-8-Kevlar-90 wt% aerogel was 143.3°). These favorable properties indicate that the composite nanofibers aerogel has potential options for sound absorption, thermal insulation in vehicles, buildings, and indoor reverberation.

Performance enhancement of metal hydride hydrogen compressors using a novel operating procedure

The H2 refueling infrastructure's capital and operating expenses are mostly driven by the cost of hydrogen compression. To effectively address this issue, thermally driven H2 compression using metal hydrides (MH) may be used. For industrial customers who have the required infrastructure, such as H2 pipelines, low-grade heat sources, etc., metal hydride hydrogen compressors (MHHC) are particularly promising. However, the H2 compression cycle time issue is brought on by the poor thermal conductivity of the MH's powder. In the present study, a novel MHHC operating procedure is examined numerically. This procedure offers two possible options: The first is referred to as a “Multiple-Cycle Simultaneous Procedure’ (MCSiP for short), as the MH beds' sensible cooling (or sensible heating) and hydrogen's absorption (or desorption) processes start simultaneously and the final pressure is reached after a number of sub-cycles of compression. The second one, dubbed the ”Multiple-Cycle Sequential Procedure“ (MCSeP for short), is similar to the MCSiP mode except that the MH beds' sensible cooling (or sensible heating) as well as the hydrogen's absorption (or desorption) start out sequentially. To evaluate the impact of this procedure on the compressor’s performance, a theoretical model was established and effectively validated by comparison with experimental results reported in the literature. The simulation findings show that the suggested procedure compresses more hydrogen mass at high pressure and is faster than the other operating methods. For instance, 140 NL H2 at a pressure of 110 bar can be obtained with a 70% reduction in compression time compared to the commonly used operating mode utilizing 1.0 kg of MmNi4.6Al0.4 as low pressure MH and 0.832 kg of Ti0.99Zr0.01V0.43Fe0.099Cr0.05Mn1.5 as high pressure MH and operating conditions of 20 bar supply pressure, 293 K absorption temperature, and 373 K desorption temperature.

Experimental studies on a closed cycle compressor operated metal hydride based cooling system with large hydrogen inventory

The current manuscript reports the experimental results of a closed loop metal hydride (MH) based compressor driven cooling system (CDCS) employing large-scale reactors. Two identical tube bundle reactors (TBR) with 19 MH tubes were designed, constructed and packed with 26.5 kg La0.8Ce0.2Ni5 alloy each for the experiments. The TBR modules were coupled with a custom-built compressor to provide cooling effect in quasi-continuous mode of operation. The compressor was tested to operate smoothly up to a hydrogen flow rate of 0.5 g. s−1 in the temperature range of 10–35 °C, yielding pressure ratio up to 12.8. Test runs were performed by altering refrigeration temperature (10–20 °C), sink temperature (30–35 °C), and half-cycle time (120–600 s). The maximum cooling power attained at 20 °C refrigeration temperature and 30 °C sink temperature was 1.44 kW, generating 537.3 kJ cooling within 600 s. The corresponding mean coefficient of performance (COP) and specific cooling power (SCP) were 0.95 and 36.4 W.kg−1 for 480 s half-cycle time. To avoid overheating of the compressor base, the half-cycle time was restricted to maximum of 600 s.

METHOD FOR EVALUATING EFFICIENCY OF REFRIGERATION UNITS BASED ON SINGLE-STAGE COMPRESSION CYCLE

The development of automation and programming tools is one of the priority areas determined by the State Program "National Technology Initiative," which requires the development of methods on the basis of which algorithms will be built.At the same time, energy saving is one of the directions for the development of refrigeration equipment. This issue is paid attention both at the state level (Federal Law No. 261-FZ "On Energy Saving and Increasing Energy Efficiency and Amending Certain Legislative Acts of the Russian Federation") and by the users of refrigeration equipment themselves, since the share of electricity consumed by refrigeration equipment is a significant part of the total energy balance of a particular enterprise. For example, the share of energy consumption of air conditioning systems in Europe ranges from 2% to 6%.The existing systems for monitoring the operating parameters of the refrigeration plant do not fully use their resource, since they are very often used only to identify emergencies and alarm them.This article describes the procedure for assessing the energy efficiency of refrigeration plants operating on a single-stage compression cycle with single throttling, which allows to evaluate both at the design stage and during the operation of the refrigeration plant, and allows to obtain a distribution of losses by elements and processes of the refrigeration plant.

Quantitative comparison of the performance of vapor compression cycles with compressor vapor or liquid injection

Increasing the Coefficient of Performance (COP) of vapor compression cycles has been a major focus for decades. Significant improvements can be brought by modifying multistage compressor to flooded single-stage compressor to approach isothermal compression. This work presents the comparative analysis of the cycle performance of a flash tank economized system (FTES), multiple refrigerant injection system (MRIS) and an oil flooded system (OFS). Thermodynamic models of each of these systems using ideal mixing models of refrigerants with the flooding agents are presented. Additionally, mixing effectiveness is introduced as a metric to evaluate the non-ideal mixing of the OFS. Results show that in MRIS, an increase in the number of injection ports significantly increases the COP of the cycle between 18% and 51% for air conditioning and refrigeration applications. The OFS shows that increasing the oil mass flow rate increases the COP significantly above the baseline cycle, benefiting higher temperature lift applications. At evaporating temperature of -40 ℃, relative COP for MRIS with 2 injection points is 7.5% higher than FTES and 5.0% higher than OFS. Further, quantification of the influence of the non-ideal mixing model for OFS showed that a mixing effectiveness of 80% results in 21% degradation of system COP suggesting the ideal mixing assumption has significant influence on the potential for an OFS.