Refrigeration Effect Research Articles

Impact of refrigeration of different Resin composite restorative materials on the marginal adaptation in class II restorations

BackgroundThe pre-polymerization temperature of resin composite restorative materials could influence their adaptation to cavity details. As a current debate is existing about the refrigeration of resin composite restorative materials, this study was designed to assess the effect of refrigeration of 3 types of resin composite restorative materials with different matrix systems on their marginal adaptation in Class II restorations.MethodsForty-two sound maxillary molars, each with two separated Class II cavities, were used in this study. The teeth were assigned into 3 main groups (n = 14) according to the restorative /adhesive system used; an Ormocer-based composite (Admira Fusion/Futurabond M+, Voco GmbH, Cuxhaven, Germany), a methacrylate modified Ormocer-based (Ceram.X SphereTEC One/Prime&Bond Universal, Dentsply Sirona GmbH Konstanz, Germany), and a methacrylate-based (Tetric N-Ceram/Tetric N-Bond Universal, Ivoclar Vivadent AG, Schaan, Liechtenstein). Each group was then divided into 2 subgroups (n = 14) according to the gingival margin location; 1 mm above and 1 mm below the cemento-enamel junction (C.E.J). Each subgroup was further divided into 2 categories (n = 7) according to the storage temperature; stored at room temperature or stored in refrigerator at 4°- 5° C. Epoxy resin replicas were observed under scanning electron microscope (SEM) to examine the marginal gaps. A gab scoring system was used to assess the marginal adaptation of each restoration by giving scores on the basis of measurements of the maximum marginal gaps. The data obtained were statistically analyzed using the Chi-square test at a significance level of p < 0.05.ResultsNone of the tested groups exhibited 100% gap-free margins irrespective of margin location or storage temperature. For both storage temperatures, no statistically significant difference was observed among all tested groups either with margins located above or below C.E.J (p > 0.05). As well, there was no statistically significant difference when comparing both marginal locations for each material (p > 0.05). Regarding the effect of storage temperature, statistically significant difference was only observed between the room-temperature stored groups with margins located above C.E.J and their corresponding groups stored in refrigerator (p < 0.05).ConclusionThe refrigeration of resin composite restorative materials prior to the restorative procedures revealed a deleterious effect on marginal adaptation of the restorations with margins located in enamel regardless the type of material used.

Simulation analysis and optimization of thermoelectric refrigeration and air conditioning

Abstract Thermoelectric refrigeration technology is mainly through the Peltier effect to achieve refrigeration, thermoelectric refrigeration air conditioning needs to be combined with a certain air flow rate to realize the separation of cold and heat, and make full use of the cold end to realize the refrigeration function, or else the refrigeration efficiency is seriously affected. Based on the ICEPAK simulation platform of ANSYS, we analyze the influence of structure and parameter settings on the conversion efficiency of thermoelectric refrigeration air conditioning fan under the established boundary conditions, establish the relationship between air flow rate and temperature drop value, and put forward the optimization of the product structure design scheme, and the results of the optimization scheme show that there is a peak in the operating current at a certain heat dissipation efficiency; and lengthening the length of the air ducts through the optimization of the structure can enhance the refrigeration effect of the air conditioner.

Modeling of magnetocaloric effect in RE2X2Y ternary compounds for cooling technology using hybrid intelligent learning computational methods

Cooling technology that employs magnetocaloric effect of magnetic refrigerants has been lately recognized as a green system with immense potential to meet the global refrigeration demand. Hugeness of magnetocaloric impact is one of the major factors which determines the choice of magnetic refrigerants for cooling applications. This research endeavour explores and models magnetocaloric effect (MCE) in ternary system of compounds which combine rare-earth metals (RE = Tm, Er, Ho, Dy, Tb and Gd) due to the localized f-orbital electrons, transition metals (X = Co, Cu and Ni) due to their ferromagnetism near room temperature and other metals (Y = Al, Ga, In, Cd and Sn) using genetic algorithm hybridized support vector regression (GSVR) computational approach. The results of Gaussian transformation function-based hybrid model (G-MCE-GSVR) and polynomial transformation function-based hybrid model (P-MCE-GSVR) are compared with stepwise regression-based model (SR-MCE) using different performance metrics such as mean absolute error (MAE), correlation coefficient (CC) and root mean square error (RMSE). G-MCE-GSVR model outperforms P-MCE-GSVR model using testing data samples with improvement of 66.93 % for RMSE metric, 5.69 % for CC metric and 68.58 % for MAE metric. Similarly, the P-MCE-GSVR model performs better than SR-MCE with improvements of 60.36 %, 37.63 % and 63.41 % corresponding to performance metrics RMSE, CC and MAE, respectively. G-MCE-GSVR model was also employed for investigating the influence of applied magnetic field on magnetocaloric effect in system of RE2X2Y ternary materials. The outstanding performance demonstrated by the developed models coupled with the obtained huge magnetocaloric effect would be of great significance in strengthening practical implementation of magnetic cooling technology for addressing energy crisis and global refrigeration demand.

Numerical Simulation and Experimental Research on Effect of Flow Regimes for Refrigeration Performance of Wave Rotor

Abstract Wave rotors exchange energy through the interaction of fluids with different pressures to produce a cooling effect without the application of mechanical parts, which makes them suitable for the complex flow field environments. But the flow situation inside the wave rotor is complex, and research on the impact of various flow regimes for the refrigeration efficiency is currently incomplete. This study deals with the numerical simulation and the experimental verification of a four-port fixed rotor gas wave refrigerator. Various typical flow regimes within the wave rotor were obtained through simulation to analyze their impact on the refrigeration efficiency. To further demonstrate the effectiveness of the simulation results, experimental verification was conducted. The simulation results indicate that separation bubbles and vortices will be respectively generated on the upper and lower walls of the wave rotor tube during the gradual opening stage. Vortex affects the airflow flow and causes detachment of separation bubbles as the airflow moves, which results in the loss of pressure energy and kinetic energy of the incident gas. As a result, the loss caused by the gradual opening process leads to a decrease in the self-expansion ability of high-pressure gas during the gradual closing stage, thereby affecting the refrigeration effect. Therefore, reducing the influence of vortices plays an important role in improving the cooling efficiency of wave rotors. Finally, this study analyzes the main factors that affect the cooling effect within the wave rotor through flow regime and provides new insights for improving refrigeration efficiency.

Effect of refrigeration and reheating on the lipid oxidation and volatile compounds in silver carp surimi gels.

As unsaturated and saturated aldehydes, ketones are known to be responsible for off-odors in surimi products, and they are mainly derived from lipid oxidation. Because surimi-based products are rich in unsaturated fatty acids, they are prone to producing off-odors during the refrigeration and reheating processes, which are common treatments for leftovers. The present study investigated the color, lipid oxidation productions, fatty acid profiles and volatile components in surimi gels during refrigeration at 4 °C for 3 days with multiple reheating. The results revealed that the accumulation rate of hydroperoxides was higher in the refrigeration stage, whereas the decomposition rate was higher during reheating in surimi gels. Both refrigeration and reheating treatments promoted conjugated diene values, acid values and carbonyl values. Nevertheless, reheating treatment decreased tohiobarbituric acid reactive substances and whiteness. The contents of unsaturated fatty acids, especially α-linolenic acid, arachidonic acid, eicosapentaenoic acid and docosahexaenoic acid, were reduced, whereas the contents of saturated fatty acids increased during refrigeration and multiple reheating. The unsaturated fatty acids were lost as a result of their oxidative deterioration. The volatile components profile showed that the accumulation of volatile components mainly occurred in the refrigeration stage. Multivariate data analysis was utilized to further clarify whether the off-odors in surimi gels were mainly generated in refrigeration. Refrigeration and reheating both contributed to lipid oxidation and the generation of volatile compounds in surimi gels, but the off-odors were mainly generated during refrigeration. This research provides a novel understanding of the formation of food odors in processing. © 2024 Society of Chemical Industry.

Evaluation of a solar-driven adsorption desalination system for Brazilian semiarid region

In this study, the effect of using a hybrid solar thermal-activated adsorption desalination system for brackish water is evaluated under the climatic conditions of the Brazilian semiarid region. The proposed theoretical model utilizes climatic data from the meteorological station in Campina Grande, PB, and adsorptive kinetics data of Fuji Davison RD 260 silica gel to predict the performance indices of the specific daily water production (SDWP), specific cooling power (SCP), and coefficient of performance (COP) performance coefficients over a characteristic day. The SDWP value of 6.26 m3/ton, SCP ranging from 50 to 300 W/kg, and an average COP of 0.5 were obtained, considering variations in global horizontal irradiance in the ACDS system and transient ambient temperature. It was observed that both the production of desalinated water and the refrigeration effect increase with the rise in daily solar irradiance. The variation in the number of solar collectors used in the system and their optimality, as well as the variation in the salinity index of the feed source, impacted the evaluated performance coefficients.

An Overview of the Energy Savings, Utilization, and Emission Reductions of Boilers

Industries and power plants use boilers extensively as a steam generating system. Boilers use a substantial amount of the world's energy supply. Much more fossil fuel can be saved and CO2 emissions can be decreased with even a slight increase in boiler efficiency. This paper outlines the energy consumption of boilers, the methods used to assess their energy efficiency, the losses that have occurred and their reasons, the role that maintenance activities play in preventing heat loss, the quantity of waste energy recovered, and the methods of raising public awareness of energy consumption. On the aforementioned subjects, the most recent published literature has been examined and reported. This includes journal articles, PhD and MSc theses, conference proceedings, reports, and online resources. The high temperature flue gas or boiler exhaust is discovered to be a significant source of energy loss. Also, for a variety of reasons, there are certain other inevitable losses. However, waste heat may be captured and used to provide power, heat, refrigeration effect, and other useful forms of energy utilizing a variety of methods. By doing planned maintenance, one may increase a boiler's efficiency and keep it operating at peak performance. Staff members must regularly participate in education programs and seminars aimed at raising knowledge about energy consumption. As a result, they will be better able to comprehend the significance of the energy utilized in the boiler system and the effects of their activities on it.

Comparative analysis of radiant air-conditioning systems combined with two different types of solar-powered dehumidification methods

Abstract This paper proposes a solar liquid desiccant radiation air-conditioning system(SLDRS) and a solar desiccant wheel radiant air-conditioning system(SDWRS) that combine with a phase change energy storage radiation terminal, solar energy, and heat pump system. The models of the two systems are simulated with the transient system tool (TRNSYS) to compare the refrigeration and dehumidification effects and energy saving of the two systems. The results show that the total refrigeration capacity of the SLDRS is reduced by 20.45% compared with the solar desiccant wheel radiation air-conditioning system, the monthly average dehumidification capacity is increased by 37.09%, and the total energy consumption is reduced by 712.9 KW·h. It is evident that the cooling and dehumidifying effect and energy efficiency of the SLDRS are superior to those of the SDWRS.

Hydrogen liquefaction process using carbon dioxide as a pre-coolant for carbon capture and utilization

With the increasing demand for hydrogen (H2), producing liquefied H2 with a high energy density (10.1 MJ/L) has become essential. Research on the H2 liquefaction process, specifically, the effects of various refrigerants and cooling cycles has been conducted. Yet, large-scale use of carbon dioxide (CO2) in H2 liquefaction hasn't been achieved. In this study, a cooling cycle that uses captured CO2 as a refrigerant in large quantities was selected for a 100 tpd H2 liquefaction process. Optimization minimized the specific energy consumption (SEC), leading to SEC of 7.3 kWh/kgLH2, a coefficient of performance of 0.17, a figure of merit of 0.33, a specific exergy efficiency (SEE) of 33 %, and an overall exergy efficiency of 82.2 %. Performance indicators were compared with other processes, showing that the SEC and SEE were improved by 43 % and 50 % compared to commercial processes and by 4 % and 6 % compared to previous studies using CO2. This study used 5.7 times more CO2 at the same capacity, utilizing 47.8 Mt of CO2, representing 14 % of the CO2 utilization amount of the total carbon capture and utilization (CCU) project. Thus, the results should facilitate the development of hydrogen liquefaction processes for use in CCU applications in the future.

Advanced vapour compression refrigeration system dispersed with hybrid Nanolubricants: ANN-Based approach

In this study, the R600a refrigerator’s performance evaluation has been investigated utilizing the implementation of hybrid nanolubricants (SiO2/CuO) at various quantities and mass charges. The outcomes of the experiments compared to those achieved using SiO2/CuO hybrid nanolubricants and R600a charges are examined. Hybrid nanolubricants are used as substitutes for pure lubricants, and the performance parameters are assessed against the results of the experiments. SiO2 at 0.2 g/L and CuO at 0.4 g/L hybrid nanolubricants provided an optimal cooling effect of 259 W and consumed a minimum quantity of energy of 73 W resulting in a maximum enhanced predicted COP value of 3.547 compared to experimental results. The clean lubricant system resulted in a minimum COP and refrigeration effect of 2.6 and 246 W and consumed more energy of 95 W. It has been observed that adding hybrid nanoparticles to compressor mineral oil substantially loweredcompressor energy consumption and enhancedrefrigeration effect, refrigerator performance. By using the ANN prediction approach, the use of SiO2/CuO hybrid nanolubricants led to maximum increased COP, refrigeration effect, and lower energy consumption when compared with experimental findings.

COMPARATIVE THERMODYNAMIC AND ENVIRONMENTAL ANALYSIS OF VAPOR COMPRESSION REFRIGERATION SYSTEM USING C-PENTANE AS REFRIGERANT

The selection of refrigerant is one of the most important parameters when designing a cooling system. Hydrocarbon refrigerants have low primary energy requirements for effective cooling capacity and favourable thermodynamic properties that reduce both direct and indirect greenhouse gas emissions. In this study, a comparative performance and environmental analysis of the vapor compression refrigeration cycle using C-Pentane as the refrigerant was performed. The cooling performance and environmental effect of C-Pentane has been compared with the cooling performance and environmental effect of R134A, R407C and R404A refrigerants in the cooling system. During the analysis, the cooling system was examined under different operating conditions. The highest coefficient of performance (COP) value in the analysis was 6.485 for the refrigeration cycle using C-Pentane, and this value was obtained at 0 oC evaporator temperature and 25 oC condenser temperature operating condition. According to the Life Cycle Climate Performance (LCCP) analysis for refrigerants, the lowest total emission value belongs to C-Pentane. Direct Emission (DE) value and indirect emission (IE) value of C-Pentane are 57.5 kgCO2 and 24928.04 kgCO2, respectively.

The pressure-volume relationship in an ideal Stirling refrigerator

Hysteresis losses in the heat transfer between compressing or expanding gas and the adjacent wall is said to play an important role in Stirling machines, where it increases the amount of required p-V work. Previous studies have linked hysteresis loss with the pressure phase shift. In the context of this research, the effect of the pressure phase shift on the net p-V work in a single space is examined.A Sage model of a single space piston-cylinder device is used to investigate the underlying mechanisms of the pressure phase shift. The Sage model is validated using an experimental piston seal rig. In addition, the time dependence of heat transfer is discussed along with how it affects the pressure phase shift, using an iterative model. The Schmidt equations were manipulated to determine the phase shift between pressure and volumetric oscillation in an ideal Stirling refrigerator.The results of this investigation are surprising. It was found that even in the case of an idealized Stirling refrigerator, the phase shift between pressure and volume is non-zero in order to produce a refrigeration effect.

LOW-COST OPERATING LPG REFRIGERATOR SYSTEM

The study explores the use of liquefied petroleum gas (LPG) as a refrigerant in domestic refrigerators to provide continuous refrigeration in areas without steady electricity supply. LPG, consisting of propane, butane, and isobutene, is cost-effective and environmentally friendly with no Ozone Depletion Potential or Global Warming Potential. The experiment compared the performance of an LPG-based refrigerator to one using R134a, finding LPG to be more efficient. By analyzing the refrigeration effect over time, the study determined the optimum cooling effect based on valve and capillary tube settings. LPG undergoes a phase change in the capillary tube, resulting in a drop in pressure and temperature, allowing it to produce a refrigerating effect. The Coefficient of Performance (COP) of an LPG refrigerator was found to be higher than a traditional refrigerator. Overall, using LPG as a refrigerant in refrigerators can be a sustainable and environmentally friendly solution for regions with unreliable electricity access. Key Words: LPG, REFRIGERATOR, REFRIGERANT, OZONE DEPLETION POTENTIAL.

Assessment of using different ozone-friendly R22 alternative refrigerants in residential air conditioners in a high-ambient temperature country

The performance of a vapor compression refrigeration system (VCRS)-based residential air conditioner operating in a high-ambient temperature (HAT) country was investigated using six zero-ODP (ozone depletion potential) refrigerants as replacements to R22. The non-flammable alternative refrigerants considered in the present research were R134a, R404A, R407C, R410A, R448A, and R507A. Using the basic conservation laws, the VCRS was modeled during steady-state operation and solved using engineering equation solver (EES) software. Coefficient of performance (COP), pressures and temperatures at compressor suction and discharge, Global Warming Potential (GWP), critical pressure and temperature, compressor pressure ratio, volumetric cooling capacity (VCC) specific cooling capacity (SCC), and refrigeration effect were utilized as assessment criteria for the alternative refrigerants considered. From these refrigerants, the highest values of suction pressure, discharge temperature, and condenser pressure were attained by R410A. In addition, the discharge temperatures for all refrigerants, except R134a, were all higher than their corresponding critical values, causing a quicker drop in the VCRS’s performance. As an alternative refrigerant, R407C showed the highest SCC of 141.0 kJ/kg followed directly by 139.2 and 138.0 kJ/kg for R410A and R448A, respectively. A reverse trend was found for VCC with respective values of 4722 and 3775 kJ/m3 for R410A and R448A. Lower volume flow rates and smaller-sized compressors are expected for higher VCC refrigerants. The same trend was found for the compressor’s specific work input and condenser’s specific heat transfer with values of (51.14, 46.82, and 45.38 kJ/kg) and (190.3, 187.8, and 183.4 kJ/kg) for R410A, R407C, and R448A, respectively. For applications in HAT countries, larger condenser’s specific heat transfer makes the refrigerant more applicable. Conversely, with respect to COP, refrigerant R134a with a value of 3.075 was the superior alternative followed by R448A and R407C with respective COPs of 3.042 and 3.011. Based on the overall assessment in terms of environmental obligation, COP, compressor input power, refrigerant flow rate required, and all the evaluations made in this research, refrigerant R448A was recommended as the most appropriate substitute to R22 which can effectively be used in residential air conditioners in a HAT country.

Effect of pasteurization, dehumidification, refrigeration and maturation on the composition, quality and acceptability of Scaptotrigona depilis honey

Honey from stingless bees has parameters that are different from those produced by Apis mellifera. These differences have led to studies of honey conservation techniques. In this context, it is necessary to evaluate whether the use of different conservation processes impacts the quality and chemical composition of this type of honey. The aim of this study was to conduct sensory analysis and determine the chemical profile, quality, and antioxidant activity of S. depilis honey subjected to different conservation processes. The physicochemical characteristics were determined in the fresh sample (time-point zero sample) and after freezing, pasteurization, dehumidification and maturation for 180 days. The reducing sugar, apparent sucrose, total acidity, moisture, water-insoluble solids, minerals, diastatic activity, Brix, color and hydroxymethylfurfural (HMF) levels were determined. These samples were also evaluated for their volatile composition and sensory aspects. After 180 days, the processed honeys showed changes in the phenolic content, and dehumidification was the treatment that most interfered with the phenolic content of the samples. The physicochemical properties that presented significant differences were the acidity, moisture, diastatic activity and color for the matured honey and the HMF levels in the dehumidification and pasteurization treatments. The main volatile compounds differed in each treatment in relation to the untreated honey. The sensory acceptance test showed significant differences for some of the attributes evaluated and the preference of consumers was for the untreated honey.

Design of nonflammable mixed refrigerants based on the partial molar enthalpy difference in mixed-refrigerant Joule-Thomson refrigerators with/no pre-cooling stage

Mixed-refrigerant Joule-Thomson refrigeration (MJTR) is an important cooling method at temperatures from 80 to 230 K. It can be used in cryosurgery, high-temperature superconductivity and sensor cooling etc. However, most of the studies are on nitrogen-hydrocarbon refrigerants, which are not allowed in applications where there is a special need to avoid flammability risks. Therefore, non-flammable mixed refrigerants were investigated in this study.The composition of the mixed refrigerant is a key factor in the system performance (refrigeration temperature, refrigeration capacity, etc). However, the purely mathematical optimization methods lack system knowledge in the optimization of the process, and may have the disadvantages of being a time-consuming process. In this study, the isothermal throttling effect of mixed refrigerants is optimized, and the optimization process is based on the partial molar enthalpy difference of each component. The method is based on thermodynamic properties and is time-saving relative to purely mathematical optimization techniques.Non-flammable mixed refrigerants (NFMR) with refrigeration temperatures from 100 K to 140 K were designed in this study. The results show that the designed mixed refrigerant has a higher COP compared to the reference. Argon has an advantage at refrigeration temperatures from 120 K to 140 K, while nitrogen has an advantage from 100 K to 120 K. In addition, mixed refrigerants for systems with pre-cooling stage were optimized and the results showed that the highest exergy efficiency is achieved at a pre-cooling temperature of 250 K. The exergy efficiencies with pre-cooling stage are nearly twice as high as those without that. Therefore, a pre-cooling stage for nonflammable mixed refrigerants is necessary where there is no requirement for system size.

Influences of distributed J-T effect on the performance of mixed-refrigerant Joule-Thomson refrigeration cycle

In a mixed-refrigerant Joule-Thomson (MRJT) cycle, the working fluid usually produces a throttling effect in the expansion element. However, the high-pressure flow in the recuperator could also generate a throttling effect due to the narrow channels, i.e., the distributed Joule-Thomson effect (DJTE). Previously published studies indicated that the cooling performance of cryocoolers would be improved by DJTE accompanying the heat recovery process. However, most of the current research on this phenomenon is focused on the heat transfer characteristics of the cryocooler itself, with a lack of research on the effect of DJTE on the cycle performance in much detail.Therefore, a detailed investigation of the influence pattern of DJTE on the cycle performance is carried out by combining with the exergy analysis. The simulation is conducted under three quintessential conditions of the recuperator. The results indicate that it is possible to manipulate the DJTE to maintain satisfactory cycle performance under specific conditions. In addition, at a constant minimum temperature difference in the recuperator, the maximum achievable DJTE is closely related to the isothermal throttling effect of the mixed refrigerant. The conclusions of this paper clarify the effect and the application value of DJTE on the cycle efficiency, which provide a reference for determining reasonable operating conditions and ensuring the cycle efficiency in practical applications.

Development of a research cryostat for direct thermoacoustic cooling and conversion of hydrogen

Hydrogen thermoacoustics is a relatively unexplored but promising topic for development of new cryocoolers and hydrogen liquefaction. This paper describes a new research cryostat designed to investigate hydrogen as a working fluid in thermoacoustic systems. The cryostat is a modular, turbo-molecular pump driven, vacuum chamber with a 4.2 K pulse-tube cryocooler capable of 45 W of cooling at 50 K. Using this cryostat, a feasibility study of direct thermoacoustic cooling with ortho-parahydrogen conversion is initiated. An acoustic resonator system is designed to have the fundamental acoustic mode excited via imposed temperature gradient in a porous stack between the ambient environment and cold bar connected to the cryocooler. The generated acoustic waves transfer heat inside another porous stack to produce a refrigeration effect at cryogenic temperatures. In addition, the regenerator solid matrix will be catalyzed for ortho-parahydrogen conversion to demonstrate a novel combination of cooling and conversion of cryogenic hydrogen in a single device. Design, construction, and performance of the cryostat and modelling results for one thermoacoustic system are reported.

Refrigerated storage stimulates isoflavone and γ-aminobutyric acid accumulation in germinated soybeans

This study aims to investigate the quality changes of germinated soybeans during refrigerated storage (4 °C), with an emphasis on the stimulatory effect of refrigeration on their special functional compounds. After germinating for two days, germinated soybeans were stored at 4 °C for seven days, while the germinated soybeans stored at 25 °C served as control group. The results showed that refrigerated storage significantly affected the physiological changes in germinated soybeans. The weight loss rate, browning rate, malondialdehyde (MDA) content and H2O2 content all decreased dramatically during refrigerated storage compared to the control group. The total phenolic and total flavonoid contents of germinated soybeans under refrigeration exhibited a trend of increasing and then decreasing over time. Additionally, during refrigerated storage, the total isoflavone content reached a peak of 8.72 g/kg on the fifth day, in which the content of daidzein and glycitin increased by 45% and 49% respectively, when compared with the control group. Moreover, the content of γ-aminobutyric acid (GABA) peaked on the first day, and kept a high level during storage. In which, the refrigerated group was 2.35-, 2.88-, 1.67-fold respectively after storage for three to seven days. These results indicated that refrigeration stimulated the biosynthesis of isoflavones and GABA in germinated soybeans during storage. More importantly, there was a sequential difference in the timing of the stimulation of the two functional components under refrigeration.

Numerical investigation in effects of refrigerants’ thermodynamic properties on performance of supersonic ejector

ABSTRACT Using zeotropic mixtures with unique temperature glide characteristics as the working medium in heat-driven ejector refrigeration system will potentially reduce the irreversible losses in heat exchange process. However, the intrinsic link between the pure/mixture refrigerants’ thermophysical properties and the entrainment performance of supersonic ejector has not yet been elucidated. In this study, a novel ejector CFD model is established by coupling the real-gas thermodynamic equation and species transport equation, then the relationships between thermophysical properties of pure/mixture refrigerants and ejector’s dimensionless operational parameters were thoroughly investigated. The results indicated that the ejector expansion ratio rises as primary flow inlet temperature or refrigerant’s normal boiling point increases, while the dimensionless parameters of primary nozzle are relatively insensitive to the variation of primary flow inlet temperature and refrigerant’s boiling point, resulted in changes of supersonic jet expansion behaviour. Moreover, the specific volume and adiabatic index change characteristics resulted in minor fluctuations of primary nozzle’s dimensionless parameters. When the bubble point temperature is fixed at 30℃ in the condenser, the saturated vapor/liquid phase pressure glide characteristics of R600a/R1234ze mixture may lead to an increasement of ejector’s compression ratio.