Influence Of Refrigeration Research Articles

Thermodynamic analysis and optimization of hydrogen liquefaction system with binary refrigerant precooling cycle

A hydrogen liquefaction process is proposed with the liquid natural gas utilization, binary refrigerant precooling and helium cryogenic cycles combined, and a general model is built for analyzing the variation of hot and cold composite curves and heat transfer temperature difference (HTTD) along with refrigerant parameters. The relationship between temperature and enthalpy of the precooling cycle and the variation of HTTD are deduced. Based on this, the composite curves and HTTD curves are constructed, and the influence of refrigerant on the HTTD and the refrigerant outlet temperature is analyzed. The optimization procedure of refrigerant is proposed based on the temperature-enthalpy relationship and HTTD considering the temperature glide. For the proposed hydrogen liquefaction system, the optimal binary refrigerant includes 60.21 % nitrogen and 39.79 % propane (mass fraction), and its mass flow rate and inlet temperature are 23,821.96 kg/h and −199.72 °C, respectively. The corresponding specific energy consumption (SEC) of the hydrogen liquefaction system is 4.44 kWh/kgLH2, reduced by 10.30 %, and the coefficient of performance (COP) and exergy efficiency are 27.10 % and 28.26 %, increased by 11.34 % and 17.80 %, respectively.

Research on energy saving potentials using pure and zeotropic refrigerants in data center cooling systems

Zeotropic refrigerants possess the characteristic of temperature glide during phase-change process, making them suitable for temperature matching between cold and hot sources and reducing total temperature differences. In this manuscript, the applicability of two commonly used refrigerants, zeotropic refrigerant R407C and pure refrigerant R134a in data center cooling systems are investigated. Firstly, the heat transfer and flow characteristics of R407C and R134a are studied to obtain boiling heat transfer empirical correlations. Secondly, a data center cooling model is established, and modeling calculations are conducted based on experimental results. Finally, the influence of refrigerants on the energy saving effect are calculated based on the model. Experimental results demonstrate that R134a exhibits a 48.3% higher boiling heat transfer coefficient compared to R407C at heat flux 16500 W/m2. However, when considering a data center cooling system, using R407C as working fluid shows the advantage of temperature matching as heat transfer area increases. Based on modeling results, at large heat transfer area, the annual cooling load factor using R407C at low mass flow rate is 0.5% lower than that of using R134a at low mass flow rate, and 22.5% lower than that of using R134a at large mass flow rate for typical climate city Harbin.

Energy and Exergy Analysis of an Automobile Hybrid Ejector Refrigeration System Utilizing Its Exhaust Waste Heat

Abstract A major current focus of refrigeration and air-conditioning research is energy usage and environmental impact (e.g., the influence of refrigerants and air-conditioning systems on ozone layer depletion and global warming). The ejector-based refrigeration system is a technology that, it is hoped, can save power while using environment-friendly refrigerants to reduce any adverse effects on nature. The reduction of compressor dependency is the first and essential aim of this study; the second is to demonstrate the replacement of R134a with the new refrigerant R1234yf in motor vehicle air-conditioning systems, establishing the benefits of employing R1234yf in conjunction with a hybrid air-conditioning system. In such a system, the engine's exhaust gases are used to operate the ejector. A numerical model has been developed which estimates the ejector entrainment ratio at a specified spindle and primary nozzle exit position. A theoretical model using energy and exergy analysis illustrates the impact of hybrid systems on performance under different operating conditions (i.e., engine exhaust, ambient air, and evaporator temperatures). At a specified exhaust temperature, a detailed comparison has been conducted between a current air-conditioning system with R134a and the hybrid system with R1234yf. It was found that the R1234yf hybrid system reduced compressor energy consumption by 44.43% and operating exhaust heat levels by 12.79%. The coefficient of performance increased by 41.42%, while the exergetic efficiency reduced from 37.14% to 13.85%. Cooling capacity dropped by 12.73%. The hybrid air-conditioning system based on R1234yf demonstrated tremendous potential for improving vehicle air-conditioning system efficiency.

Biological behavior of Chrysomya putoria (Wiedemann, 1819) (Diptera: Calliphoridae) after refrigeration: Logistics for use in Biotherapy

The influence of refrigeration on the post-embryonic development of Chrysomya putoria larvae was evaluated, regarding its resistance in the logistics of storage and distribution in biotherapy. Previously sterilized larvae were submitted to four periods of storage under refrigeration (T1=12 h, T2=24 h, T3=48 h and T4=72 h) and control (without sterilization and refrigeration). Newly hatched larvae (0.200 g) were stored between 3 and 9ºC. After refrigeration, 40 neo-larvae (in triplicate) were transferred to 50 g of protein diet and incubated in an acclimatized chamber. There was a significant difference in the larval body mass (T1 and T2) and in the duration of larval, pupal and total development (T3 and T4). The sex ratios found in the four treatments did not differ from what was expected. Normality rates were 100% for all treatments. There was no significant difference between the Control, T1 and T2 treatments for larval, pupal and total viability. There was a significant difference between control (C) and T4 (larval viability), between C, T3 and T4 (pupa) and between C and T4 (total). C. putoria has resistance under refrigeration and storage of up to 56 h, presenting viability above 70% for use in biotherapy.

Multi-scale evaluation of ejector performances: The influence of refrigerants and ejector design

Ejector refrigeration systems pose a promising alternative to vapour compressor technologies. Still, they have not been penetrating the market because of the strong dependency of the ejector behaviour (“component-scale”) on the underlying fluid-dynamics (“local-scale”), which directly affects the system performances (“system-scale”). Furthermore, within the broader discussion concerning refrigerant phase-out, the refrigerant selection is a cutting-edge and challenging task, especially because the ejector performance is influenced by the coupling taking place between the working fluid and component design. This paper contributes to the broader framework of ejector research investigating the complex relationships between the factors mentioned above that arise during the operation of a standard ejector refrigeration system. An integrated model (CFD-LPM) has been applied to compare fourth generation and natural refrigerants (R1233zd(E), R1234yf, R1234ze(E), R290, R1270, and R600a) to commonly used refrigerants (R134a, R245fa, R152a) on five ejector geometries, obtained changing the nozzle exit position and the mixing chamber throat dimension from a reference case. Based on the results in terms of performance curves, tested refrigerants could be divided into three groups: (i) R1270 and R290, having higher COP (0.5–1.03) but lower critical temperature Tcrit (20.7–25.0 °C), (ii) R134a, R152a, R1234yf, R1234ze R600a, with an intermediate value of COP (0.27–0.83) and critical temperature Tcrit (22.8–28.0 °C), (iii) R245fa and R1233zd, with lower COP (0.25–0.58) but higher critical temperature Tcrit (26.0–31.0 °C). Increasing nozzle exit position has been found to slightly affect the performances (+5% COP) while the ejector entrainment process has been found to highly depend on the mixing chamber diameter (up to + 35% COP). One of the tested geometries has been then selected, with R290 as operative fluid, to perform a boundary conditions sensitivity analysis. This led to the definition of a system performance map for different system temperature levels at the generator and evaporator.

The Influence of Refrigerants on Energy Indicators of Hermetic Compressors

The Influence of Refrigerants on Energy Indicators of Hermetic Compressors

The influence of oil-refrigerant mixture on thermal and physical processes on friction joints

The paper deals with the influence of refrigerants dissolved in oil on the thermo-physical properties of the lubricant and the operation of friction joints in refrigeration machines. It is demonstrated that in the axial and circumferential directions the bearing temperature, if lubricated with a mixture of T-30 – R-22 is significantly lower than when lubricated with T30 oil.

Influence of refrigeration and freezing storage on the instrumental texture of corn dough and empanadas

Influence of refrigeration and freezing storage on the instrumental texture of corn dough and empanadas

Influence of Refrigeration on Histamine-Producing Bacteria and Biogenic Amines Content During Ripening of Ras Cheese

Cheese is a histamine-rich food and may contain biogenic amines formed during ripening process, due to degradation of proteins through proteolysis. Therefore, histamine producing bacteria and biogenic amines content were studied during ripening of ras cheese at refrigeration temperature 4±1oC for 10 weeks using HPLC. Three batches of Ras cheese were manufactured using Egyptian conventional method. From each batch, samples collected at zero, 2, 4, 6, 8 and 10 weeks after cheese manufacture. The obtained results revealed that Enterobacteriaceae and Enterococci had the same pattern during ripening of ras cheese with a significant decrease from (5.0x108±7.02x106 at zero day until reach 4.60x10±0.24x10 cfu/g at week 10 of storage), (from 3.46x105±3.17x104 at day zero until reach to 2.20x10±0.23x10 cfu/g at week 10 of storage), respectively. Lactobacilli count showed fluctuation during ripening period where the highest count recorded at 2nd and 10th week 4.40x105±0.25x105 and 4.40x105±0.15x105 cfu/g, respectively. Enterobacteriaceae, enterococci and lactobacilli producing histamine were identified. Investigated biogenic amines (Cadaverine, Histamine and Tyramine) significantly decrease during ripening of ras cheese while, Putrescine showing fluctuation during ripening. Therefore, to protect consumers from biogenic amines poisoning, factors that enhance biogenic amines formation during cheese processing should be controlled.

Influence of refrigeration or freezing on human milk macronutrients and energy content in early lactation: Results from a tertiary centre survey.

Neonates with severe conditions that cannot be breastfed should receive fresh or preserved expressed human milk in addition to parenteral nutrition. To identify the time during lactation when the macronutrients provide maximum energy and evaluate the effect of refrigeration and freezing. We analyzed the composition of fresh milk, refrigerated at +4°C and frozen at -20°C, expressed by mothers of 60 preterm and 30 term infants from a level III maternity, in colostrum, transitional, and mature milk. In fresh milk, the protein level constantly decreases during lactation, with a significant difference after 3 weeks of lactation. Preterm milk of day 21 and day 30 had significantly lower protein than term milk (1.27 versus 1.43 g/dL, P=0.015 and 1.13 versus 1.28 g/dL, P=0.001). Refrigeration for 72 hours of term milk decreased protein content less than freezing. Preterm colostrum has significantly less protein after 48 hours of refrigeration or freezing. Preterm milk from day 60 lost carbohydrates if refrigerated 72 hours or frozen for 2 months. Lipids in preterm colostrum decrease after 8 weeks of freezing. Refrigeration for up to 72 hours did not change significantly the energy value of colostrum or transitional milk. Freezing preterm milk more than 2 weeks leads to significant loss of energy. Milk frozen for more than 2 weeks contains less protein and energy than milk refrigerated for up to 72 hours. In the absence of milk bank access, in common settings, short-term refrigeration is preferable to long-term freezing.

Characterizing the Flow of Thickened Barium and Non-barium Liquid Recipes Using the IDDSI Flow Test

The use of thickened liquids for dysphagia management has become wide-spread.Videofluoroscopy is commonly used to determine dysphagia severity and to evaluatethe effectiveness of interventions, including texture modification, but this requires theuse of radio-opaque contrast media. In order for the results of a videofluoroscopy tohave validity with respect to confirming swallowing safety and efficiency on differentliquid consistencies, it is important to understand the flow characteristics of the contrastmedia used and how the flow of these stimuli compares to the flow of liquids that areprovided outside the assessment context. In this study, we explored the flowcharacteristics of 20% w/v barium and non-barium stimuli prepared using starch andgum thickeners to reach the slightly, mildly and moderately thick liquid categoriesdefined by the International Dysphagia Diet Standardisation Initiative (IDDSI). Our goalwas to identify recipes that would produce stimuli with stable flow properties over a 3h time frame post mixing. Thickener concentration was titrated to achieve matchingflow (i.e., IDDSI Flow Test results within a 1 ml range) across the four stimulus types(non-barium starch, non-barium gum, barium starch, barium gum) within each IDDSIlevel. The combination of barium and thickeners resulted in further thickening,particularly with starch-based thickening agents. A probe of the influence ofrefrigeration showed no difference in flow measures between chilled and roomtemperature stimuli over a 3-h time frame. Overall, recipes with stable flow overthree hours were identified for all barium and non-barium liquids tested.

TWO PHASE CFD FLOW ANALYSIS OF R134a AND R1234yf REFRIGERANTS AND ITS EFFECT ON COOLING PERFORMANCE IN AN AUTOMOBILE HVAC EVAPORATOR CORE

The purpose of this research is to conduct a two-phase fluid analysis and simulation for examining the influence of refrigerant (R134a/R1234yf) properties on cooling performance of an automobile HVAC (Heating, Ventilation and Air Conditioning) evaporator core and compare their performances. In this research, streamline deviation, static pressure, velocity magnitude, pressure co-efficiency, Reynolds number and turbulent kinetic energy play a key role in the comparison of the refrigerants R1234yf and R134a two-phase fluids. Subsequently, it was found that R134a properties were better towards the cooling performance of an automobile HVAC evaporator core.

The Influence of Liquid Refrigerant on Refrigerating Compressors Sliding Surfaces

Reasons of compressors failures are connected with different operating conditions of individual parts. One of compressor damage reasons is pouring it over with liquid refrigerant. The purpose of this work was to carry out tests concerning the influence of refrigerant being in the liquid phase on piston compressor sliding surfaces. Tests were carried out in the mixture of synthetic polyester oil with liquid refrigerant R134a. The tests were performed with the use of the friction machine and the pair type block-on-ring simulating the refrigerating compressor inside and with the use of the real refrigerating compressor. The obtained results confirm the unfavourable influence of liquid refrigerant on friction elements in the refrigerating compressor. The role of hydrodynamic phenomena in the development of damage to the compressors has been showed.

Influence of refrigeration and cassava starch biofilm use on enzymatic browning in mangaba fruit (Hancornia speciosa)

The mangaba tree fruit has several nutritional properties and its market interest is growing, although its limited shelf life has made storage and trade over long distances impossible. The present study aimed to quantify peroxidase (POD) and polyphenol oxidase (PPO) enzymes activity in the pulp of mangaba fruits coated by cassava starch biofilm. Fruits were harvested in a home orchard and were evaluated after 3, 6 and 9 days of storage. POD activity was higher than PPO activity in both temperatures and in all storage times tested for the fruits harvested in the home orchard. The temperature of 25 °C was the one that best inhibited the activity of both enzymes. Data showed no statistical difference regarding POD activity in the pulp related to the starch concentration used in the biofilm. As for PPO, the lowest activity was found in the pulp of fruit coated with the highest starch concentration tested (4%). Additional keywords: Hancornia speciosa Gomes; native Cerrado plant; peroxidase; polyphenol oxidase.

Using dynamic simulation to quantify the effect of carbon-saving measures for a UK supermarket

A standard UK supermarket design is used to simulate the energy performance, and subsequent CO2 emissions, of a modern-day UK supermarket building. Retrofit measures are proposed to reduce these CO2 emissions by over 50%, mostly due to demand-side measures but also accounting for likely onsite supply-side solutions. The influence of refrigeration and lighting in such buildings is explored and the possible use of heat recovery systems discussed. The air-tightness of supermarket buildings is also highlighted as a potential area for significant energy savings. Finally, the reliance on grid electricity is demonstrated for non-domestic buildings with a high electrical energy use. A combined approach of energy efficiency and low-carbon offsite electrical generation is suggested from the described case study as the most successful strategy to achieve large carbon savings (i.e. >50%) in existing supermarket buildings.

Preparation, Rheological Study, and Characterization of an Organogel as a System for Transdermal Release of Active Principles

The use of formulations containing Pluronic® gel as a vehicle and permeabilizing agent for transdermal preparations has increased in recent years. We prepared and compared two transdermal formulations for drug administration as an alternative to oral or parenteral administration. In formulations containing Pluronic® F127 gel or pluronic lecithin organogel (PLO), rheological, structural (transmission electron microscopy) and physicochemical characteristics were studied under different conditions of composition, temperature, and time from 24 hr to 3 months after preparation. Rheological studies at 20–25°C and at 4°C to study the influence of refrigeration on viscosity and pH showed that both formulas were thermoreversible. Unilamellar vesicles smaller than 1 μm in diameter were seen in the PLO formulation on TEM observation. The characteristics of these excipients may facilitate the application and may avoid the gastrointestinal tract and the first-pass effect.

Influence of refrigeration and carbon dioxide addition to raw milk on microbial levels, free monosaccharides and myo -inositol content of raw and pasteurized milk

The influence of CO2 treatment on free monosaccharides and myo-inositol in raw and pasteurized milk during cold storage was studied. Pasteurization did not cause significant changes in the monosaccharide fraction. No variations in the level of galactose and myo-inositol in untreated and CO2-treated samples were observed during cold storage. The content of glucose decreased considerably during cold storage due to bacterial growth in pasteurized milk. During cold storage of pasteurized milk no changes in N-acetylgalactosamine were observed, whereas N-acetylglucosamine decreased considerably after 15 days. No differences between untreated and CO2-treated milks were found. A substantial decrease in N-acetylglucosamine and a gradual increase in N-acetylgalactosamine were observed in raw milk during cold storage. The former was attributed to consumption of this hexosamine by microorganisms and the latter was probably due to microbial glycosidic enzymes. The addition of CO2 to raw milk proved to be a useful treatment for milk preservation without modifying the free monosaccharide fraction.

Use of the single cell gel electrophoresis assay (Comet assay) as a technique for monitoring low-temperature treated and �irradiated muscle tissues

The influence of refrigeration, freezing, repetitive freezing-thawing, and irradiation on meat quality were evaluated by detecting DNA damage to beef muscle tissues using the single cell gel electrophoresis assay (Comet assay). Comet tail lengths indicating DNA damage levels increased with refrigeration time up to 10 days. In the case of frozen storage, the damage was increased only for the first 15 days of storage, but after that, decreased slightly and the tail lengths at 15 days were similar to those of 3˜5 days refrigerated storage. Tail lengths resulting from repetitive freezing-thawing were increased after two cycles of treatment and three cycles produced longer tails than those that had been refrigerated for 10 days or kept in frozen storage for 60 days. Irradiation from 1 to 10 kGy caused the most serious DNA damage among the treatments compared in this study. The two kinds of muscle tissue were similar in the pattern of results obtained from the Comet assay. The mean tail length of the comets reflected approximately the increasing patterns of DNA damage, but the differences of values between the extents of treatment were somewhat insignificant and anomalous. Therefore, we used the concept of relative damage index (RDI) calculated from per cent cells data for each tail length range and representing a state of DNA damage. Significantly different values in RDI’s made it possible to discriminate samples according to the treatment levels within each treatment.

Effect of refrigeration on bactericidal activity of four preserved multiple-dose injectable drug products

The influence of refrigeration on the bactericidal capability of preservative systems in multiple-dose injectable drug products was studied. Commercially available multiple-dose injectable drug products containing preservatives--atropine/phenol, lidocaine/methylparaben, cyanocobalamin/benzyl alcohol and diphenhydramine/benzethonium chloride--were divided into two groups, one to be maintained under refrigeration (5C) and the other to be maintained at room temperature (25C). In separate tests the multiple-dose vials (MDVs) were individually inoculated with the following organisms: Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Serratia marcescens, and cultured to establish bacterial concentrations at 0, 1, 2, 4, 8 and 24 hours. Bacteria in the preservative systems tested remained viable significantly longer under refrigeration. (Data for diphenhydramine/benzethonium were not obtainable with the methodology used.) It is recommended that sterile medications maintained in preserved MDVs be stored at romm temperature after initial use (i.e., after exposure to possible contamination) unless drug stability considerations dictate otherwise.

Influence of refrigeration on aflatoxin production by strains of Aspergillus flavus.

Strains of Aspergillus flavus that produce high concentrations of aflatoxin in cultures incubated at room temperature also produced these toxins in significant concentrations under conditions simulating household refrigeration (7.5° to 10 °C). The rate of toxin production at 10 °C was markedly influenced by preincubating cultures at room temperature for 24 hours. Solid cultures yielded higher concentrations of toxin than liquid cultures under the prevailing experimental conditions.