Refrigeration Method Research Articles

Compositions optimization method based on the effective refrigeration effect for Mixed-refrigerant Joule-Thomson refrigerators cooling distributed-temperature heat loads

Mixed-refrigerant Joule-Thomson refrigeration (MJTR) is the dominant technology for cooling distributed-temperature heat loads, such as natural gas liquefaction. The mixed refrigerant determines the refrigeration cycle's performance (cooling temperature and efficiency, etc.). However, the current mathematical methods for mixed refrigerants’ optimization are time-consuming. In this paper, a mixed refrigerant optimization method based on the effective refrigeration effect is proposed. The equivalent enthalpy (EH˙) of temperature difference is proposed to predict the temperature difference distribution in the recuperator without cycle simulation. The optimization objective is to optimizeEH˙much closer to zero. In each step, only one component is adjusted, which is determined through its’ effective refrigeration effect, i.e., the partial molar enthalpy difference, in the optimization process. This method is applied to natural gas liquefaction (LNG), nitrogen liquefaction (LN2) and Cryo-compressed hydrogen storage (CcH2) systems. The exergy efficiencies in LNG, LN2 and CcH2 systems are 0.462, 0.390 and 0.421, which increase about 23.9%, 22.4% and 23.5% compared to references, respectively. The optimization time is less than 10 min per case in this study. This method can optimize mixed refrigerants in MJTR cooling various distributed-temperature heat loads.

SlMsrB5 contributes to the chilling tolerance induced by methyl jasmonate in postharvest tomato fruit

Chilling injury (CI) is a common phenomenon during low temperature storage for most fruits, reducing the effectiveness of refrigeration methods. Methyl jasmonate (MeJA) has been extensively employed to extend the shelf life of fruits during cold storage. However, the mechanism of MeJA inducing fruit resistance to CI requires further investigation. The study found that treating tomatoes with 0.05 mM MeJA inhibited CI by regulating the reactive oxygen species (ROS) metabolism, polyamines, and jasmonic acid (JA) signaling pathway, as well as cold response pathway. Interestingly, the expression of SlMsrB5 in tomato was up-regulated under MeJA treatment, showing an increase of 36.44% to 161.75% compared to the control fruit. Notably, silencing the expression of SlMsrB5 led to a continuously increased in CI incidence by 52.17% and CI index by 36.58% compared to the control fruit at the end of storage. Additionally, the silencing of SlMsrB5 weakened the inhibitory impact of MeJA on CI and reduced its induction effects on the aforementioned indicators. In addition, correlation analysis showed that the transcription of SlMsrB5 has a negative correlation with ROS related indicators under MeJA treatment, while was highly correlated with the aforementioned induction effects controlled by MeJA. Therefore, this study demonstrates a new basis for revealing the underlying mechanisms in the MeJA-regulated chilling resistance in postharvest fruits.

Experimental study of the absorption refrigeration using ocean thermal energy and its under-lying prospects

The construction of a maritime cold chain network with islands as node is an important avenue for the economic development of the island, in which efficient refrigeration technology is essential to the development of the marine industry. Motivated by the substantial resources of tropical ocean, an absorption-compression refrigeration device is constructed and its technical feasibility is firstly demonstrated by experiment, achieving a refrigerating capacity of 6.8 kW and 10.2 kW at the evaporation temperature of −24.5 °C and −18 °C, respectively. The pressure rise by the compressor has been reduced by 185 kPa when compared to traditional vapor-compression refrigeration. The energy-saving potential of different refrigeration methods is also summarized, with the proposed refrigeration achieving the highest level of energy-efficient ratio, EER = 6.57. Especially, the proposed refrigeration can be cascaded with power generation, desalination, chilled-soil agriculture, and aquaculture to realize the gradient utilization of ocean thermal energy and hence improve the overall economy. This work opens up a new path for promoting and developing the use of ocean thermal energy for blue ocean economy in tropical oceans with bathymetry depths of 300 m or higher.

Experimental and Simulation Research on Heat Pipe Thermal Management System Coupled with Battery Thermo-Electric Model

The lithium-ion battery is widely used in the power system of pure electric vehicles and hybrid electric vehicles due to its high energy density. However, the chemical and electrochemical reactions generate a lot of heat. If the heat is not transferred through some refrigeration methods in time, it will lead to a rapid rise in the temperature of the battery. In this paper, an electric–thermal coupling model of a cylindrical Panasonic 21700 battery was proposed by using offline parameter identification method. Based on this model, a battery thermal management system using a heat pipe was established. The experimental results show that the model can simulate the actual performance of battery well. When the ambient temperature is 25 °C, the battery parameters change little and battery performance is better. The heat pipe battery thermal management system performs better than the non-heat pipe battery system in the discharge process, and can control the battery temperature well at low and high temperatures. Changing the refrigerant temperature can achieve a better thermal management effect under suitable ambient temperature conditions.

Air Refrigeration Methods for Comparison Simulation Bench

Air Refrigeration Methods for Comparison Simulation Bench

High-performance polymer-based regenerative elastocaloric cooler

Alternative methods of refrigeration are critical for performance optimization and environ- mental sustainability. Prototype systems using caloric materials have shown the advantages of a high coefficient of performance (COP) and low global warming potential. Elastocaloric elastomers can meet ongoing needs, but their implementation in functional heat pumps or coolers remains challenging due to their requirement for a large deformation and low thermal conductivity. Moreover, a scalable design is required to achieve high cooling power. As a leap forward for the use of polymers in larger scale caloric devices, we developed experimental elastocaloric polymer coolers with two different geometries using natural rubber tubes. We confirmed that a suitable geometry partially compensated for the low thermal conductivity and led to performances comparable to those of other caloric devices. Several operating conditions were tested to determine the optimal temperature span, cooling power, and COP for both device geometries. Under a specific operating condition, one of the prototypes exhibited a maximum temperature span > 8 K, a maximum COP of 6, and an output cooling power of 1.5 W; this power outperforms other prototypes based on polymers or ceramics. The parallelization of rubber tubes will facilitate realistic elastocaloric polymer coolers on a larger scale.

A Thermoelectric Refrigerator Using Arduino

Refrigerator and air conditioners are the most energy consuming home appliances and for this reason many researchers had performed work to enhance performance of the refrigeration systems. Most of the research work done so far deals with an objective of low energy consumption and refrigeration effect enhancement. Thermoelectric refrigeration is one of the techniques used for producing refrigeration effect. Thermoelectric devices are developed based on Peltier and Seeback effect which has experienced a major advances and developments in recent years. The coefficient of performance of the thermoelectric refrigeration is less when it is used alone, hence thermoelectric refrigeration is often used with other methods of refrigeration. This paper presents a review of some work been done on the thermoelectric refrigeration over the years. Some of the research and development work carried out by different researchers on TER system has been thoroughly reviewed in this paper. The study envelopes the various applications of TER system and development of devices. This paper summarizes the advancement in thermoelectric refrigeration, thermoelectric materials, design methodologies, application in domestic appliances and performance enhancement techniques based on the literature.

Energy efficiency evaluation method of refrigeration and air conditioning in intelligent buildings based on improved entropy value method

Energy efficiency evaluation method of refrigeration and air conditioning in intelligent buildings based on improved entropy value method

Energy efficiency evaluation method of refrigeration and air conditioning in intelligent buildings based on improved entropy value method

In order to improve the accuracy and precision of the evaluation of cold source energy efficiency, this paper proposes an evaluation method of cold source energy efficiency of refrigeration and air conditioning in intelligent buildings based on the improved entropy method. On the basis of analysing the energy efficiency ratio composition of refrigeration and air conditioning system, the calculation process of energy efficiency ratio is refined by using refrigeration energy efficiency transport function. Then the AHM improved entropy method was used to optimise the weight ratio process, and the efficient and accurate evaluation of the cooling source energy efficiency of refrigeration and air conditioning was completed by adjusting the weight ratio. The experimental results show that the average evaluation accuracy of the proposed method is 95.9% and the average evaluation accuracy is 96.3%, which proves that the proposed method achieves the design expectation.

Preparation and Performance of n-Dodecane Microencapsulated Phase Change Cold Storage Materials

Cold chain transportation is currently a hot research topic. Since the traditional refrigeration methods lead to the consumption of large amounts of energy, the search for new energy storage materials is a major trend. In the present contribution, n-dodecane/PMMA microencapsulated phase change materials were prepared by suspension polymerization for ice-temperature cold chain transportation and their preparation parameters were explored using the encapsulation ratio as optimization indicator. The results show that the n-dodecane-containing microcapsules have a maximum encapsulation ratio of 93.2% when using a core-to-wall ratio of 3:1, 5% of emulsifier, 30% of crosslinker, and 2000 rpm of emulsification speed. The phase transition temperature and enthalpy are −2°C and 195.9 kJ/kg, respectively. The microcapsules prepared with the optimized process parameters have good microscopic morphology, high energy storage efficiency, uniform particle size and good thermal stability, making them ideal materials for cold chain transportation.

Quality characteristics of sweet potato leaves (Ipomoea batatasL.) as influenced by processing and storage conditions

This study investigated the effects of blanching, drying and storage conditions on the quality characteristics of sweet potato leaves (SWPL). SWPL (unblanched and steamed blanched at 90 C for 1 min) were oven-dried (50 C for 72 hours), packaged in polyethylene bags, stored at ambient temperature (28±2 C) and refrigerated (7±2 C) for nine weeks. The rehydration ratio, beta carotene, phenolic content, mineral content, and their soup sensory properties were determined at three weeks intervals using standard methods. Rehydration ratio, beta carotene and phenolic contents ranged from 9.46-10.50, 0.10-0.70 g/100 g and 16.40-29.20 g/100 g respectively. The refrigerated blanched samples contained a greater amount of calcium (496.35) and zinc (1.64) than unblanched samples at the end of nine-week storage. The soups prepared from refrigerated blanched dried SWPL were rated similar to fresh SWPL. The combined processing methods of blanching, drying and refrigeration preserved the nutrients in SWPL with better rehydration and organoleptic properties.

Design and implementation of a new portable hybrid solar atmospheric water-generation system

Abstract During recent years, atmospheric water generation (AWG) has garnered significant attention among researchers as a viable solution to the water-scarcity problem. Generally, AWG requires dehumidification, which includes two main principles of refrigeration and sorption. Among refrigeration methods, thermoelectric coolers are suitable and, among sorption methods, it is best to utilize desiccant materials with high sorption capacity and low heat generation. In the present study, a portable hybrid/integrated solar AWG system was designed and tested under realistic conditions of Babol, Iran (36.5387°N, 52.6765°E) over four typical summer days between 14 and 31 August 2021. Two models (Models A and B) were designed and evaluated. Temperature, relative humidity, solar irradiance and water-production data were recorded to assess the system performance (i.e. the ratio between the generated water and consumed power in ml/W.hour) and economically analyse the system. Based on the results acquired, the maximum water production in the proposed configuration (acquired from Model B) was 2.12 l/m2.day at an average relative humidity and a temperature of 52% and 36°C, respectively. The desired AWG system had a system performance of 0.19 ml/W.hour, annual water production of 774.4 l/m2, production cost of 0.0246 $/l/m2 and a payback period of 1.19 years.

A mathematical model of critical releasable charge for R290 indoor leakage of split-type household air conditioners

The leakage of hydrochlorofluorocarbons and hydrofluorocarbons used as refrigerants will not only cause ozone depletion and global warming, but also pollute indoor air. Propane (R290) not only does not damage the ozone layer and has a negligible greenhouse effect, but also its charge is about 20–50% of that of hydrochlorofluorocarbons and hydrofluorocarbons, and the releasable charge is lower. In the previous study, a refrigerant pump-down method was proposed to control the R290 releasable charge of split-type household air conditioners (STHACs) under off-mode below the critical releasable charge (CRC) to prevent fires. CRC varies with leakage conditions, such as leak hole sizes, the distance between the installation height of the indoor unit (IDU) and the ignition source (dispersion distance), and the construction of IDU, etc. In this study, a mathematical model is developed to predict the CRCs for STHACs with different capacities and constructions under various leak conditions. The model is verified to have a deviation within 10% for the vast majority of data-points by ignition experiment and CFD model. For safety, the CRC prediction formula is optimized to under-predict CRCs properly, therefore, CRCs for various STHACs and leak conditions are determined to prevent the formation of flammable mixtures even directly under IDU, and the indoor air quality will also be improved. For the used 1 HP STHAC, the predicted CRC is 6.6 g under a 0.5 mm2 leak hole and a 0.7 m dispersion distance.

Indirect Evaluation of the Electrocaloric Effect in PbZrTiO3 (20/80)-Based Epitaxial Thin Film Structures

Electrocaloric effect is the adiabatic temperature change in a dielectric material when an electric field is applied or removed, and it can be considered as an alternative refrigeration method. Materials with ferroelectric order exhibit large temperature variations in the vicinity of a phase transition, while antiferroelectrics and relaxors may exhibit a negative electrocaloric effect. In this study, the temperature variation in polarization was investigated for epitaxial ferroelectric thin film structures based on PbZrTiO3 materials in simple or complex multilayered structures. We propose the intriguing possibility of a giant negative electrocaloric effect (ΔT = −3.7 K at room temperature and ΔT = −5.5 K at 370 K) in a simple epitaxial Pb(ZrTi)O3 capacitor. Furthermore, it was shown that abnormal temperature variation in polarization is dependent on the non-FE component introduced in a multilayered structure. No significant variation in polarization with temperature was obtained for PZT/STON multilayered structures around room temperature. However, for PZT/BST or PZT/Nb2O5 multilayers, an abnormal temperature variation in polarization was revealed, which was similar to a simple PZT layer. The giant and negative ∆T values were attributed to internal fields and defects formed due to the large depolarization fields when the high polarization of the FE component was not fully compensated either by the electrodes or by the interface with an insulator layer. The presented results make Pb(ZrTi)O3-based structures promising for cooling applications operating near room temperature.

A Review on Experimental Analysis on Hybrid Vapour Compression Refrigeration System

Abstract: A vapor-compression refrigeration system is a system that uses liquid refrigerant in a closed system which circulates the refrigerant through four stages in which it is alternately compressed and expanded, changing it from liquid to vapor. As this change happens, heat is either absorbed or expelled by the system, resulting in a change in temperature of the surrounding air that is passing over the unit's components. Nearly all of the refrigeration systems we use today use this cycle to accomplish cooling. VCRS system is made up of four main components: the evaporator, condenser, compressor and expansion valve. The evaporator and condenser are both a series of coils that are designed to create more surface area for the refrigerant to react with. Meanwhile, the compressor and expansion valve are mechanical units that control the amount of pressure and temperature change that occurs between the two stages. It was named after Jean Charles Athanase Peltier, the physicist who discovered the effect in 1834. Peltier discovered that when current is made to flow through a circuit consisting of two different types of conductors, a heating or cooling effect is observed at the junctions between the two materials. This change in temperature at the junction is called the Peltier effect. When electric current is passed through a circuit consisting of two different conductors, a cooling effect is observed in one junction whereas another junction experiences a rise in temperature. This change in temperatures at the junctions is called the Peltier effect. The effect is found to be even stronger when two different semiconductors are used in place of conductors in the circuit. In this journal Two methods of refrigeration work together to get a good coefficient of performance (COP). The both vapour compression refrigeration method which good in control the inside temperature and peltier effect by combined together in a single setup. The heat generated from the two dissimilar semiconductors are used to change the complete phase transformation of the refrigerant system before entering into the compressor. The combined system we call it as hybrid experimental system. The COP of thermoelectric system in combined with VCRS is increased by proper heat dissipation, from hot side of the peltier units and these heat fluxes utilized by VCRS for its own benefit.

Study on a coalbed methane liquefaction system based on thermoacoustic refrigeration method

Recovery of coalbed methane (CBM) is significant for the safe production of coal mines, environmental protection, and clean energy supply. A novel CBM liquefaction process composed of a looped three-stage thermoacoustic engine and three pulse tube coolers (PTCs) is proposed. Each PTC is connected to one thermoacoustic engine unit by bypass. Potential liquefaction processes using thermoacoustically driven PTCs are proposed and studied numerically. The operating parameters of the system are globally optimized by performing genetic algorithm procedures, using specific power consumption (SPC) as the objective function. Additionally, exergy analyses are conducted on the main components of the system to reveal the potential directions for improvement. It is found that a three-stage thermoacoustically driven PTCs is an appropriate configuration considering the overall efficiency and geometric compactness of the system. The optimized SPC of the system is 0.58 kWh·Nm−3, which is comparable to that of the traditional liquefiers. The overall exergy efficiency of the system is 36.25%. Total exergy loss of the three PTCs is 4.978 kW, accounting for 80% of that of the system. Having the advantages of being driven by heat instead of electricity, safe operation, compact structure, and high efficiency, the proposed liquefaction process is promising for small-scale gas reserves, especially for CBM.

Modeling the magnetic cooling efficiency of spinel ferrite magnetocaloric compounds for magnetic refrigeration application using hybrid intelligent computational methods

Spinel ferrite exhibits large magnetocaloric effect that promotes its candidature for solid state magnetic refrigeration technology. This method of cooling is promising and can conveniently replace the gas-compression method of refrigeration due to its energy saving capacity and ecological cleanliness. Among the available magnetocaloric materials, spinel ferrite metal oxide enjoys low production cost, non-toxicity, ease of preparation and non-oxidative. However, effective utilization of this magnetocaloric material for cooling technology requires determination of its magnetic cooling efficiency which is subjected to time consuming, intensive and laborious experimental procedures. This work employs the applied magnetic field, ionic radii and the concentrations of spinel ferrite constituents to develop a genetically hybridized support vector regression model (G-SVR) and extreme learning machine (ELM) intelligent model for determining magnetic cooling efficiency of spinel ferrite compounds. The developed G-SVR model outperforms ELM model for the testing set of spinel ferrite samples with percentage improvement of 60.57%, 19.69% and 64.73% using root mean square error, correlation coefficient and mean absolute error respectively, as performance measuring parameters. Influence of metal ions such as zinc, nickel and cadmium on magnetic cooling efficiency of various kinds of spinel ferrite compounds was investigated using the developed models. The presented intelligent approaches for spinel ferrite magnetic cooling efficiency determination in this work, with characteristic lower cost, quickness, effectiveness and precision would definitely facilitate and strengthen practical implementation of magnetic refrigeration technology for energy conservation and environmental friendliness.

Flammable refrigerant leakage hazards control for split-type household air conditioners

Propane (R290) is expected to be employed in air conditioners and heat pumps, whereas the flammability slows down its uptake. In this study, the leakage hazards control of an R290 split-type household air conditioner (STHAC) with 5 mm diameter finned-tube heat exchangers under off-mode were investigated through concentration measurement and ignition experiments. The critical releasable charges under which a fire may or may not occur at different installation heights were obtained and examined through ignition test. A refrigerant pump-down method was proposed to evacuate the R290 in the indoor unit (IDU) by the compressor to below the critical releasable charge under off-mode. Therefore, the leakage hazards would be enormously decreased, and it could be equally used for other flammable refrigerants or commercial refrigeration units. Besides, a deconvolution method was employed to correct the deviation of measured R290 concentration caused by response time. It is found that the critical releasable charge was 4.3 g and 8 g under a 1 mm leak hole at 1.8 m and 2.2 m installation height of IDU respectively with 1.5 m ignition height from the floor. A formula was proposed to acquire the number of compressor revolutions during the pump-down process. Moreover, the deconvolution method could effectively correct the deviation caused by the response time, but the deconvoluted concentration was still lower than the actual concentration due to the “averaging” effect at the inlet and sample cell of the detector, especially under a small releasable charge below 17.8 g.

Optical Trapping of High-Aspect-Ratio NaYF Hexagonal Prisms for kHz-MHz Gravitational Wave Detectors.

We present experimental results on optical trapping of Yb-doped β-NaYF subwavelength-thickness high-aspect-ratio hexagonal prisms with a micron-scale radius. The prisms are trapped in vacuum using an optical standing wave, with the normal vector to their face oriented along the beam propagation direction, yielding much higher trapping frequencies than those typically achieved with microspheres of similar mass. This platelike geometry simultaneously enables trapping with low photon-recoil-heating, high mass, and high trap frequency, potentially leading to advances in high frequency gravitational wave searches in the Levitated Sensor Detector, currently under construction. The material used here has previously been shown to exhibit internal cooling via laser refrigeration when optically trapped and illuminated with light of suitable wavelength. Employing such laser refrigeration methods in the context of our work may enable higher trapping intensity and thus higher trap frequencies for gravitational wave searches approaching the several hundred kilohertz range.

Atmospheric Water Generator

Abstract: An Atmospheric Water Generator is a device which is extracts water vapor from the humid air. By using different dehumidification technique. the water vapor accumulated then water is then filtered and purified through several filters including carbon, and reverse osmosis, and UV sterilization lights. The result is pure drinking water from the air. an Atmospheric Water Generator Works on the same principle as a refrigerators and air conditioners i.e on the principle of vapor compression refrigeration. in atmospheric water generator air passing through evaporator coil which temperature maintain below dew point temperature of water by vapour compression refrigeration method air condenses to to dew point temperature water vapor separate from air then collected water vapor is passed through a filtration system and it is then stored in a tank. The major aim or objective of our project is to provide safe and clean drinking water to those areas which are facing water shortage problems or where water transportation through regular means is expensive (especially rural areas). Our project hopes to reduce this problem by providing an atmospheric water generator that will run via bicycle-gear arrangement or stand-alone renewable source of energy i.e either solar or wind.