Refrigeration Conditioning Research Articles

Experimental investigation on a closed-cycle single-stage turbo-refrigerator for deep freezing

Turbo-refrigerator based on reverse Brayton cycle is an attractive solution for providing refrigeration at ultra-low temperatures below −60 °C for deep freezing. Employing a motor-driven turboexpander compressor (MTEC) not only allows the turbo-refrigerator to achieve high compactness, reliability and flexibility, but also leads to new operating characteristics especially in a closed cycle. This paper aims to investigate the operating characteristics of a closed-cycle single-stage turbo-refrigerator with a MTEC. A high-speed turbo-refrigerator system with the design refrigeration temperature of −86 °C was manufactured and then tested under variable rotating speeds and refrigeration conditions. Test results show that a refrigeration temperature below −96.4 °C was obtained in a pull-down progress. Compared with a fixed-speed operation, variable-speed operation enables the independent control of the refrigeration temperature and the cooling capacity. With the decrease in the refrigeration temperature (or in the cooling capacity), the rotating speed has a greater effect on the COP than that on the cooling capacity (or on the refrigeration temperature). The mass flow rate along with the compression and expansion work shows a decreasing trend as the refrigeration temperature decreases at a fixed speed of the MTEC. The advanced exergy analysis shows a total exergy efficiency of 0.42 (with a COP of 0.62 at refrigeration temperature of −86 °C) could be expected with component improvement in the near future, and it is of the priority to increase the efficiency of the turboexpander.

Effects of Different Viol Types on Egg Shell Microbiology in Table Eggs at Different Storage Temperatures

The purpose of this research was to examine the impact of storing table hen eggs in egg cardboard box viol, plastic box viol, and cardboard viols at various temperatures on the microbiology of the egg shell. A total of 150 table chicken eggs were used in the study. The eggs were randomly distributed into three groups: standard cardboard viol, plastic box viol, and cardboard box viol. The eggs were stored at room temperature and in the refrigerator for 28 days. On the 0, 7, 14, 21, and 28 days of the experiment, five eggs from each group were analyzed for total bacteria (TAMB), mold-yeast, and coliform. The Viol type x storage temperature interaction effect was significant (P<0.05) only on egg shell mold-yeast, but its effect on the TAMB and coliforms was insignificant. The effect of viol types on shell coliforms was insignificant. Egg TAMB and mold-yeast counts were found to be lower in plastic box viols than in other groups (P <0.05). TAMB and mold-yeast count were found to be higher in eggs that were stored in refrigerator conditions than in room conditions (P <0.05). From a microbial perspective, it can be said that storing eggs in plastic box viols is more suitable in terms of hygiene during storage.

Improving performance of air conditioning system by using variable-circuit heat exchanger: Based on the Chinese APF standard

For finned-tube heat exchangers, owing to the extremely different refrigerant pressure drop characteristics between condensation and evaporation processes, the optimum refrigerant circuits of these two conditions are different. However, for a typical heat pump type air conditioner, refrigerant circuit of the conventional heat exchanger (CHX) is fixed no matter what operation condition is conducted. To solve this problem, a modified variable-circuit heat exchanger (VCHX) is developed for air conditioner outdoor unit applications. The VCHX, for which the refrigerant circuit can be easily switched by using a globe valve, could provide better matching characteristics between refrigerant circuit and operation condition variations. With a developed simulation model, refrigerant circuit of the VCHX is optimized by using the entropy generation minimization theory. Then, comparative experimental works were conducted to investigate the performance of VCHX and CHX systems in detail. Experimental results show that the presented VCHX is more suitable for high heating capacity and low cooling capacity applications. Based on the Chinese APF (annual performance factor) Standard, the VCHX system yields 6.5% higher APF value over CHX system. Significantly, economic analysis indicates that the investment payback period of VCHX system is 1.46 year, which is much lower than the designed lifetime of a residential air conditioner. In general, the VCHX technique has a great application potential for improving the overall performance of a heat pump type air conditioner.

An Experimental Study omn Evaporative Condenser in Air Conditioning Systems Using R744

Nowadays, the use of refrigerants has low GWP and zero ODP applying refrigeration and air conditioning systems is an important concern. There has been a lot of research taking about refrigeration systems using R744. In this study, we focus on the use of the mix of water and air for an evaporative condenser through an experiment to study the heat transfer efficiency between water and the R744. The results of this study show that it is feasible to use water to cool down R744 to a subcritical state. The data obtained show that the R744 temperature at the outlet condenser gradually decreases with each change in the number of tube layers, the condensing pressure is stable at 73 bar with a pressure drop of 0.4 bar. The water temperature is stable between 26oC and 28oC, and the air outlet temperature from the indoor unit gradually decreases from 28oC to 16.8oC. With the 3 configurations of the condenser, the coefficient of performance gradually increases from 3.6 to 4.5 respectively.

Processing and Nutritional Evaluation of Amla (Phyllanthus emblica) Pomace

Background: Amla (Phyllanthus emblica), popularly known as the Indian gooseberry, belongs to Euphorbiaceae family is known for its cool, refreshing, pleasant taste and utilised for various products and beverages. During processing, massive amounts of amla pomace that is an abundant source of polyphenols, ascorbic acid, dietary fibre and tannins is discarded as waste. Methods: The research was undertaken to standardize the process of dehydration and nutritional evaluation of amla pomace. The physico-functional properties, sensory evaluation, particle size distribution and its effect on hydration properties, microbial load was carried out from initial to 45 days of storage at both ambient and refrigerated temperature conditions for amla pomace powder. Results: The physico-functional properties indicated pH 3.44, colour L* 86.47, a* -0.74 and b* 11.13, particle density 1.23 g/cm3, water holding capacity 12.30 g/g, water binding capacity 12.37 g/g and swelling capacity 13 mL/g. The nutrient composition was found to have good amount of total dietary fibre (41.7g) with abundant minerals like calcium (128mg), phosphorus (116mg) and magnesium (48mg) along with low fat (0.18g), low carbohydrate (7g) and low calorific value (36 Kcal) per 100g. The phytonutrients, viz., ascorbic acid, tannins and polyphenols were 432, 524 and 677 mg per 100g, respectively. The Sensory scores of Amla pomace were good and the microbial counts were within the permissible limits during 45 days of storage period. Hence, amla pomace powder, a nutritious by-product can be utilized effectively as a functional ingredient in value added products.

Pressure Drop and Heat Transfer Characteristics of TiO2/R1234yf Nanorefrigerant: A Numerical Approach

Global warming is one of the most dangerous ecological issues facing the globe. Refrigerants are a major contributor to global warming. This investigation mainly focuses on the analysis of a greener nanorefrigerant. Nanorefrigerant can improve the efficiency of refrigeration and air conditioning systems that use vapor compression. In the present investigation, mathematical and computational methods are used to assess the heat transfer and pressure drop properties of TiO2/R1234yf. In order to analyze the heat transfer characteristics and the transport features of the innovative nanorefrigerant, appropriate mathematical predictive models were adapted from earlier investigations. The models are validated by the experiments using TiO2/POE nanolubricant as a test fluid. The investigation was conducted with a temperature range of 10 °C to 40 °C and a volume percentage of nano-sized TiO2 particles in R1234yf refrigerant ranging from 0.2 to 1%. According to the research, the introduction of nanoparticles increases viscosity, thermal conductivity, and density. However, as the amount of nanoparticles rises, the specific heat capacity of the nano-enhanced refrigerant decreases. The nanorefrigerant’s heat transfer coefficient and pressure drop are improved by 134.03% and 80.77%, respectively. The outcomes observed from the predictive technique and the simulation approach had an average absolute variation of 9.91%.

Perspective role of phase change materials for energy efficiency in Algeria

Various measures have been considered in Algeria to improve energy efficiency but other effective ways are promising such as integration of phase change materials. The potential of these smart materials is reviewed for energy efficiency improvement in various systems including energy storage, refrigeration, and air conditioning, building envelope as well as cooling of photovoltaic systems. The literature review shows the high potential of this new class of materials. The survey indicates up to 12% energy savings due to integration of these new materials in refrigeration, 17.82% for air conditioning systems, and 10% for photovoltaics. The highest impact was achieved for the building envelope where energy savings of 34.8% were reported. On the other hand, limitations, challenges, and future concerns are revealed and highlighted for both researchers and policy-makers. New eco-friendly materials should be searched and adapted to the Algerian climate zones. Artificial intelligence can be a handy tool for material selection and optimization of thermal performance. Investment should be implemented together with adequate policy and awareness. Finally, the Algerian building regulations should be updated to include this new class of materials in buildings.

Photovoltaic thermoelectric cooling system for off-grid vaccine refrigerator: an experimental study

The rapidly rising demand for refrigeration technologies, mainly in refrigeration and air conditioning, medical applications, and electronic component cooling, produced much more energy than required. Thermoelectric refrigeration is an innovative way to use additional energy to cool and reserve cooling. In this research, a photovoltaic-thermoelectric refrigeration system capable of sustaining vaccine storage within the limit of 2–8 °C has been established by experimentally optimizing its volume and performance. The design specification is to cool the volume using forced convection to the desired temperature range in less than 30 min and sustain retained heat for at least the next hour. The experimental research is divided into two stages: the first determines the optimal volume of vaccine storage under different testing conditions using only grid power, and the second analyses storage performance using solar energy through photo voltaic (PV) integration. The solar direct drive and the solar drive with battery support have been timed, revealing a holding period of 4 h, 46 min and 5 h, 29 min, respectively. The refrigerator's design criteria, prospective characteristics, and final design are all thoroughly highlighted. Finally, we conclude that this research will likely benefit the modeling and analysis of thermoelectric cooling systems.

Effect of Aloe vera and carboxymethyl cellulose-derived binary blend edible coating on the shelf life of fresh-cut apple.

In recent years, the demand and market for minimally processed fruits are increasing worldwide. Fresh-cut apples are extremely sensitive to environmental factors including oxygen, temperature, and microorganisms in resulting the browning of apples. Therefore, in this study, different concentration of blended edible-coating solution was prepared using Aloe vera and carboxymethyl cellulose (1:1, 1:2, 2:1, 3:3, 3:2, 4:2, 2:4, 3:4, and 4:3, respectively). Lease particle size (101.74 ± 0.67 nm) of the coating solution was observed with 3% A. vera and 2% carboxymethyl cellulose (CMC). Afterward, the shelf life of the apples was evaluated for 10 days at refrigeration condition. Results showed that a significant difference was found in weight loss of coated (6.42%-10.26%) and uncoated apples (8.12%-15.32%) for 2-10 days. Moreover, the titrable acidity of the cut apples increased during the storage time. Rheological data emerged that the viscosity of the coating solution decreases with the increasing temperature from 0 to 50°C. Fourier transform infrared spectroscopy data confirmed the presence of hydroxyl group (-OH), C=O, C-O, and N-H banding in the A. vera, CMC, and blend-coating solution. The blend solution indicated excellent antimicrobial efficiency. Total phenolic content of coated and uncoated apples at 0 day was 737.55 mg GAE kg-1 for uncoated and 717.88 mg GAE kg-1, respectively. Whereas, aerobic and psychrotrophic bacteria counts for edible coated apples significantly lower than control apples. For coated apples, aerobic and psychrotrophic bacteria counts were 1.59 ± 0.84 and 1.25 ± 0.49 log CFU g-1 were 4.26 ± 0.67 and 2.68 ± 0.22 log CFU g-1 at 10th day, respectively. Overall, it can be inferred that blend of A. vera and carboxymethyl cellulose could be used as a nontoxic potential anti-browning and antimicrobial component for the enhancement of the shelf life and additional nutritional value of fresh-cut apples.

THE EFFECT OF POMEGRANATE AND GRAPE SEED EXTRACTS ON THE SHELF LIFE OF GOOSE MEAT DURING REFRIGERATED STORAGE

The aim of this study is to investigate the effects of pomegranate and grape seed extracts on the shelf life of goose meat samples stored in refrigerator conditions. Seven different sample groups were created including control (C), pomegranate seed extracts (PSE1, PSE2), grape seed extracts (GSE1, GSE2), and antioxidants (BHA, BHT). Prepared goose meat sample groups were stored under refrigerator conditions for 10 days and lipid oxidation, moisture, pH and color properties were analyzed during this period. The extracts decreased the TBA values of the samples compared to the control group (P<0.05). Antioxidative effects of synthetic antioxidants and extracts added to goose meat samples were determined as BHA > GSE2 = GSE1 = PSE2 = BHT > PSE1, respectively. Grape and pomegranate seed extracts have strong antioxidant activity, and it can be recommended that these extracts can be used as natural antioxidants in the preservation of goose meat.

Study of Solar Photovoltaic Array for Air Conditioning System

The vapor compression refrigeration (VCR) and air conditioning systems are widely used for cooling, refrigeration, air conditioning, heating purposes and consumes more than 33% of the world energy. Solar energy is available abundantly as renewable energy source in summer when requirement of comfort is in peak demand. The electrical energy is replaced with solar energy by properly selecting solar panels, battery, inverter, charge controllers for storing fruits and vegetables in rural areas due to uncertain pattern of grid electricity. In the paper, solar power VCR system is designed and simulated with Simulink to estimate the performance in terms of irradiance and temperature. It is found that with rise in irradiance, current and power outcome increases. The solar system is CO2 free with substantial saving of 9700 whereas conventional VCR system produces 5292 kg of CO2 during life time of solar PV system.

Investigation of Bioactivity Degradation During Storage of Sour Cherry (Prunus cerasus L.) Peel Extract.

Limited number of researches in the literature have been reported to examine degradation stability by regression methods. Monitoring storage stability of plant extracts containing phytochemicals has become a special field. This study aims to develop model equations to examine the stability of total phenolic material (TPM) and total anthocyanin (TA) in the sour cherry peel extract under several conditions, such as keeping the samples in a freezer (-20°C), refrigerator (4°C) and room temperature (25°C) conditions. In addition, two types of ambient conditions (under dark and light, respectively) were applied to observe the effect of sunlight on oxidation. The storage stability was monitored in terms of TPM and TA. 8 different polynomial regression equations were produced for the data obtained under each condition in order to define the deterioration of the TPM and TA during 60 days of the storage. Keeping the samples in the light at ambient conditions was the least efficient for stability (~10 days), while the shelf life of the product could have been quite long with the storage in the freezer after opening the package of the product. The most suitable condition for both TPM and TA has been determined as -20°C with the calculation of degradation days as 157 and 115 (R^2 = 0.9874 / 0.9265, and average error rates = 0.207097% / 0.119541%).

Perancangan Sistem Pendingin dan Tata Udara pada Ruang Mesin produksi di PT. X untuk Menjaga Performa dan Ketahanan Komponen Mesin

Several influencing factors, including temperature, air cleanliness, and humidity levels, are necessary to preserve the performance and durability of engine components against injury. Many mechanical and electrical components of the machine were damaged at Company X because the room's temperature, air quality, and humidity did not comply with the machine's standard operating conditions. If nothing is done to enhance the engine room's air conditioning, the engine will sustain greater damage. The purpose of this research is to design a cooling and air-conditioning system in the production machine space in PT. X to maintain the performance and durability of machine components. The engine compartment is 104 m2. The design of the refrigeration and air conditioning systems includes the calculation of the required capacity, analysis, and the creation of design drawings in the engine compartment. According to the calculation, the required engine room refrigeration capacity unit is 9.36 kW with 1640 l/s. This capacity incorporates the requirement for fresh air, which is 245 l/s. With this capacity, the engine's optimal temperature and oxygen quality can be attained.

Topical caffeine-loaded nanostructured lipid carriers for enhanced treatment of cellulite: A 32 full factorial design optimization and in vivo evaluation in rats

The goal of this study was the development and evaluation of semisolid caffeine (CAF) loaded nanostructured lipid carriers (NLCs) for topical treatment of cellulite. CAF-loaded NLC formulations were prepared via high-speed homogenization followed by ultrasonication. A 32 full factorial design was employed for formulation optimization. The total lipid content (%) and the liquid lipid content per total lipids (%) were chosen as factors, whereas particle size (PS), polydispersity index (PDI), zeta potential (|ZP|) and viscosity (VIS) were selected as responses. The design suggested CAF-NLC3 as the optimum formulation consisting of a total lipid content of 15% w/w (palmitic acid and soft paraffin/isopropyl myristate, 7:3 w/w) and a surfactant content of 10% w/w (Tween 80/lecithin, 8:1.2 w/w). CAF-NLC3 revealed PS, PDI, ZP, VIS and CAF content values of 318.8 nm, 0.253, −41.1 mV, 18.0 Pa.s and 97.57%, respectively. It showed a pseudoplastic rheological behavior, acceptable pH value (5.25), good spreadability (1.12 mm2/g) and spherical shape employing transmission electron microscopy. Differential scanning calorimetry and X-ray diffraction demonstrated the amorphization of CAF in CAF-NLC3. CAF-NLC3 remained stable for 3 months at room and refrigeration conditions. A single topical application of CAF-NLC3 on shaved abdominal skins of Wistar rats revealed enhanced skin retention of CAF by 2-fold and 1.4-fold after 4 h when compared with plain CAF gel (CAF-P) and marketed CAF gel (CAF-M), respectively. Furthermore, CAF-NLC3 exhibited a superior anti-cellulite activity in comparison with CAF-P and CAF-M through elevating extracellular matrix components (collagen 1, elastin and hyaluronic acid) and stimulating the brown adipose tissue thermogenesis via up-regulating UCP1 and PPAR-γ expression. In addition, CAF-NLC3 prominently increased lipolysis through HSL activity and decreased pro-inflammatory cytokines such as ICAM-1 and VCAM-1 after 30 days of treatment on a high fat diet-induced cellulite rat model. These findings were further confirmed by histopathological examination supported by morphometric analysis. Therefore, incorporation of CAF in a semisolid NLC formulation would be a promising cosmetic approach for the topical treatment of cellulite.

Application of atomized hydrosols to rainbow trout fillets as an easy preservative

In this study, a storage box including an ultrasonic atomizer was obtained with a 3D printer, and atomized hydrosols of thyme and lavender were applied to the fish meat at regular intervals under refrigeration conditions (3±1℃) for 6 days. The effects of application with atomized hydrosols on lipid oxidation (malondialdehyde levels), peroxide value (PV), total volatile basic nitrogen (TVB-N) level, microbiologic level, color changes, and texture parameters were investigated. The results of the study showed that aerosolizing hydrosol droplets on the meat protected the quality significantly as the storage period increased and that the ultrasonic atomizer could be used effectively in the preservation of food quality.

Study of frost layer growth process on horizontal cold surfaces in the channels

Based on the layer-by-layer growth phenomenon existing in the actual formation of frost layer, we constructed a frost model with supporting criterion and studied the growth process of the frost layer on the horizontal cold surface at the bottom of the channel. Comparison with relevant experimental data revealed a maximum error of 25.3% in the calculated thickness and 13.1% in the density. The change in density and thickness over time under different working conditions, especially the variation in the thermal resistance under refrigeration conditions, were analyzed from local and overall perspectives. From a local perspective, thickness and density were highest at the frost front and slowly decrease along the flow direction before increase again at the end of the frost layer by 7.3% and 32.9% respectively. The local thermal resistance of the frost layer first increased sharply along the flow direction, reached a local peak and then decreased slowly. From an overall perspective, both the average thickness and average density increased with time, while the average thermal resistance first increased sharply with time, reached a peak, and then decreased slowly.

Ways to use refrigerators that use heat to cool vehicles.

BACKGROUND: Today, most of the heat that is released during the combustion of fuel in internal combustion engines goes into the environment along with exhaust gases. However, additional energy can be used for refrigeration and air conditioning. Previously, there were only two ways to use exhaust heat for cooling: absorption machines and ejector chillers. But now, thanks to the development of organic Rankine cycles, there are new possibilities for cooling vehicles.
 AIMS: Conduct a theoretical analysis of the possibility of introducing mobile air conditioning and refrigeration systems in transport using various types of refrigeration machines that operate on the basis of heat.
 MATERIALS AND METHODS: Modeling of typical cooling cycles was carried out in the ASPEN HYSYS software environment. The most effective substances were selected from the absence of supercritical conditions.
 RESULTS: Depending on the selected cycle type, simulation results were obtained that corresponded to the calculated parameters. The coefficients of performance were determined under various ambient conditions and generator temperatures.
 CONCLUSIONS: A theoretical analysis of various cooling cycles for use in transport has been carried out. The results of the calculations show that the task of ensuring the cooling of the cabin or cargo is carried out even in the harsh operating conditions of the refrigeration system.

Performance of Solar Adsorption Cooling System Using Methanol and Activated Carbon as a Working Pair

The need for renewable energy sources is higher than ever due to rising global warming, climate change, and ozone depletion. For refrigeration and air conditioning applications, adsorption refrigeration systems are viable alternatives cooling techniques. This study is a topic and part of the M.Sc. thesis. A field solar-powered ice maker unit was created, studied, tested, and evaluated on the 13th and 30th of May, 2022. Activated carbon and methanol pair was used to set up a refrigeration system in Baghdad (Al Dora). Experimental tests were carried out outdoors to determine the coefficient of performance COP and specific cooling power SCP of the system. The results showed that the lowest temperature obtained at the evaporative surface was (4 oC) and (3 oC) for the 13th and 30th of May, respectively, at the opening time of the valve between the evaporator and the generator at 9 pm. In addition, the amounts of methanol condensate were (0.340 kg) and (0.344 kg) for the 13th and 30th of May, respectively, while the maximum cycle coefficient of performance (COP) and specific cooling power SCP are about 0.57 and 0.14 kW/kga.c , respectively

Study of breathing behavior and its heat load for a refrigerator through the gasket

Gaskets play an important role in thermal insulation and sealing in refrigerators. In this paper, the aim is to explore the effect of gasket structure on transport characteristics of moisture air. A dynamic breathing behavior measurement platform was built based on the tracer gas technique. The experimental results imply that an inhalation effect, the alternating inhalation-exhalation effect and the exhalation, inhalation, exhalation & inhalation effects occur under the Pull-down, intermittent refrigeration and defrosting-cooling conditions. Since the basic structure is improved by the one of tilted top-edge, large main part height, auxiliary edges and an auxiliary airbag or their combination, the infiltration rate of gasket is decreased by 5.39% ∼ 62.34%. The increase in magnetic attraction force leads to a decrease in the size of the infiltration gap, which plays a role in suppressing the infiltration of moisture air. It is estimated that the infiltration suppression effect of magnetic attraction force is approximately 0.061 g·m−1·h−1·N−1. For enhancing sealing performance, designing as tilted top-edge, adding auxiliary edges, increasing main part height of 2.5 mm and adding an auxiliary airbag are equivalent to the increase of the magnetic strip thickness of 0.1 mm, 0.3 mm, 0.8 mm and 1.4 mm. In addition, heat and moisture transfer of the gasket consumes the cooling capacity of refrigerator. The moisture transfer consumes less cooling consumption, ranging from 13.4% to 16.8%. From the perspective of energy conservation, it is preferred to improve the thermal insulation performance rather than the sealing performance of gasket.

Effect of Different Edible Film Coatings on Microbial Analyses and Organoleptic Attributes of Fresh Cut Kiwi (Actinidia Deliciosa) Green Kiwi Cv. Hayward

The current study aimed to evaluate the effect of different edible film coating of Carboxymethyl cellulose and Aloe vera gel on microbial and sensorial properties of fresh-cut kiwi fruit stored at 4oC for 20 days. The slices of kiwi fruit were covered with Carboxymethyl cellulose and Aloe vera gel while the uncoated samples served as control. The kiwi fruit slices were packaged and cold stored at refrigerator condition and it was conducted with the appropriate methodology at the post-harvest laboratory of the Department of Horticulture, Sam Higginbottom University of Agriculture, Technology and Sciences, Allahabad, during 2022-23. The experiment was laid out in December month of 2022 in a completely randomized design with Nine treatments and three replications. The treatment details viz., Control, Carboxymethyl Cellulose 1.0%, Carboxymethyl Cellulose 1.5%, Aloe vera gel 30%, Aloe vera gel 40%, Carboxymethyl Cellulose 1.0% + Aloe vera gel 30%, Carboxymethyl Cellulose 1.5% + Aloe vera gel 30%, Carboxymethyl Cellulose 1.0% + Aloe vera gel 40% and Carboxymethyl Cellulose 1.5 % + Aloe vera gel 40%. It is concluded that the effect of Treatment T3 i.e., AVG 3 was found to be best in terms of microbial analyses i.e., Yeast and mould count (log CFU/g) (2.07), Total bacterial count (log CFU/g) (3.38) and Spoilage (%) (13.34%) and Sensory evaluation i.e., Colour score (6.17), Taste score (6.19), Odour score (6.13), Texture score (4.89) and Overall acceptability (5.85) i.e., T3. The results highlighted that Aloe vera gel 30% coating improved the quality of stored fresh-cut kiwi fruit slices.