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In this study, a solar-driven combined cooling-heating and power system is proposed to achieve higher energy efficiency. Influences of compression ratio and direct normal irradiance are reported to evaluate the impact of design parameters. A compressed air energy system technology is utilized in the solar-driven Brayton cycle to run it in the peak consumption time, and a Rankine cycle is employed as an axillary cycle for more power generation. Results prove that the proposed system provides 11.75 MW pure power besides 3.2 MW heating and 6.8 MW cooling loads and it is able to run 5 hr in compressor deactivated mode passing peak consumption hours. Overall energy efficiency of the proposed system is estimated by more than 55% considering solar inlet beams energy, and 89% ignoring solar tower energy loss. The most exergy destructor component of the proposed system is solar heat absorber by 72% of general system destructed exergy. [ABSTRACT FROM AUTHOR]

The aim of the study is to review the use of gas products of natural and synthetic origin and their future application prospects. To achieve this goal, a number of high-tech technologies were pre-sented and analysed. The phase equilibrium parameters of inert and fluorine-containing gases were shown, as well as the temperature ranges in which certain refrigerants can be applied. Ex-amples of cooler schemes for providing rectification processes at 28 and 210 K were given. The processes of refrigeration cycles in T-s diagrams of neon and R116 (hexafluoroethane) were shown. Schemes of helium systems for heat removal at the level of 5…28 K were considered. The areas of application of Xe, Kr, Ne, and He in modern technologies, particularly in laser technology, space exploration, lamp industry, and medicine, were highlighted. The most signifi-cant result of the work is the determination of the important role of isotopic components of inert gases for the future of energy, functional diagnostics, metrology, and other fields. In semicon-ductor manufacturing, many inert gases are used as protective environments and working media in ion-plasma and ion-beam etching in vacuum chambers. In plasma chemical surface treatment, substances containing one or more halogen atoms act as active gases. The significance of the results achieved is evident in that, in the context of a global shortage of technical gases, the de-velopment of resource-saving technologies is becoming relevant. Among these, gas product re-cycling, where gas concentrates were obtained from used mixtures, enriched, and subjected to deep purification for the secondary use of target products, is the most promising.

A mathematical model based on energy and exergy methods is established to analyze the performance of an auto-cascade refrigeration system at varying compositions of the mixed refrigerants, condensation temperature, evaporation temperature, and vapor quality at the condenser outlet. Furthermore, grey correlation theory is employed to assess the correlation degrees between refrigerant mass fractions and system performance, enabling the identification of the state that has the greatest impact on the output parameters. It has been concluded that while maintaining a constant mass fraction of R600a, an increase in the mass fraction of R1150 (State 1) leads to a higher cooling capacity but a decrease in exergy efficiency. The performance decreases with the increase of the R600a mass fraction (State 2) as the R1150 mass fraction is unchanged. When the component of R14 is constant while the other two components R600a/R1150 vary (State 3), and the COP exists as the optimal value. The mixture of R600a/R1150/R14 with a mass fraction of 0.5:0.2:0.3 has better performance at COP of 0.5027 and exergy efficiency of 29.43% under a condensation temperature of 30 °C. Based on the results of the grey correlation degree, the greatest factor in cooling capacity is State 1, while the COP and exergy efficiency are primarily controlled by State 3. [ABSTRACT FROM AUTHOR]

The current research aims at finding a new appropriate way to optimize and reduce water consumption by using various forms of pinch technology in petrochemical complexes due to high rate of water consumption. For this purpose, precise studies were conducted on ethylene plant. In this research, cracked gas compressor (CGC) system was considered to analyze energy and minimize water consumption of heat exchanger network (HEN). Initially, process of the CGC system has been simulated with Aspen HYSYS. Next, Aspen Energy Analyzer software was used to identify cooling water (CW) heat exchangers and economic analysis of HEN. Consequently, composite curves and grand composite curves and other results of HEN simulation were examined. The results of HEN simulation indicate that 91% of cooling loads provided by CW utility is the most widely used fresh water. Despite water circulation system of cooling tower (CT), the rate of water loss is high in this utility. As the design temperature is 40 °C and the minimum approach temperature (ΔTmin) is 10 °C, the new utility pinch point has been estimated 50 °C. In proposed modified case, air coolers were considered before the CW heat exchangers of the CGC system. In this way, air-cooled (AC) utility covers up cooling loads up to 50 °C in the modified unit. Then, the modified unit was compared with main unit. In the modified unit, 78% of cooling loads of the HEN have been covered by AC utility in which this action leads to 86% reduction in energy and water consumption of CW heat exchangers and CT. By reducing the rate of water loss in CT circulation systems, cost of supplying fresh water reduced to the lowest possible which leads to 34% optimization in HEN operating cost in the modified unit. Also in the CGC system, steam turbine is used for supplying power consumption of compressor used to CW steam turbine condenser. This condenser is the most commonly used equipment in terms of water consumption, so that there is 32% more than the total water consumption of the HEN. In the last part of this study, AC steam turbine condenser replaced the CW steam turbine condenser in the modified case. So in this case, the use of AC steam turbine condenser with power consumption (980 kw) leads to 98% reduction in water consumption of the steam turbine condenser. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A thermodynamic analysis of a simple inverse cycle is proposed as a means to evaluate mixtures of CO 2 and four organic substances (propane, iso-butane, dimethyl-ether and propylene) as working fluids. The cycle features an internal heat exchanger and is designed to cool down a finite heat capacity flow on the cold side. The analysis covers trans-critical as well as sub-critical cycles. For each organic substance, the composition is optimized. Flammability is accounted for. Dimethyl-ether (DME) turns out to be the best option, as a relatively low mass fraction of this compound is sufficient for reaching the thermodynamic optimum. In this way, a simple, sub-critical refrigeration system may be obtained featuring a non-flammable working fluid and a significant COP increase with respect to pure CO 2. [ABSTRACT FROM AUTHOR]

The Gifford-McMahon cryocoolers are considered to be prominent candidates for the cooling of high-temperature superconducting magnets, liquefaction of permanent gases, helium recondensation in magnetic resonance imaging machines, cooling of superconducting quantum interference device, etc. In this paper, multi-dimensional numerical simulation is performed to visualize the oscillating heat and fluid flow processes that happen in a mechanically driven GM cryocooler. Influence of the ideal gas equation and real gas equation of states on the cooling behaviour is explained. The minimum achievable refrigeration temperature of a uniform mesh regenerator is compared with a multi-mesh regenerator. It is noticed that a multi-mesh regenerator produces a lower refrigeration temperature as compared to a uniform mesh regenerator. In addition to this, a one-dimensional simulation is conducted and results are compared with multi-dimensional numerical simulation. The no-load temperature value calculated by the one-dimensional model and multi-dimensional model with ideal gas is lower than that of real gas equations. Additionally, the refrigerating capacity calculated by the one-dimensional model and multi-dimensional model with the ideal gas equation is higher than those of the real gas equation of state. [ABSTRACT FROM AUTHOR]

Copyright of Revista Tecno Lógicas is the property of Instituto Tecnologico Metropolitano and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For store and maintain products, ingredients, and other perishables at a safe temperature, there is a growing need for low‐temperature refrigeration systems. In this study, a new multi‐objective exergetic criterion is proposed for the optimization of refrigeration cycles, the conventional coefficient of performance (COP) maximization method results in high evaporator temperature, which is in contrast with the philosophy of the invention and design of refrigeration cycles. Thus, it is not a suitable platform for comparing different refrigeration cycles. This research aims to define a practical performance analysis parameter for designing and comparing refrigeration cycles. The novelty of this research is incorporating the impact of evaporator temperature into the COP concept. A performance comparison of the multi‐objective optimization is drawn with that of the maximum COP state on a transcritical carbon dioxide refrigeration cycle. According to the comparison, the evaporator temperature at the optimal state of multi‐objective exergetic optimization was 44 K lower than that of the maximum COP state, which demonstrates the excellent performance of the method. The results of the new multi‐objective exergetic optimization can be used to design low‐temperature evaporation refrigeration cycles. In the end, the flowchart of the suggested performance optimization is presented. Exergy of power at the optimal point of exergetic optimization is about 77% higher than the maximum COP. A comparison of the results obtained from maximum performance coefficient with optimal point of exergetic optimization suggests that the performance coefficient at optimum state of exergetic optimization is about 58% lower than the maximum COP. [ABSTRACT FROM AUTHOR]

Direct air capture (DAC) is one of the most potential technologies to mitigate CO2 emission. Adsorption technology is recognized as a promising CO2 capture method in view of its desirable characteristics including reusability of adsorbents and low capital investment. To further improve thermal performance, evaporation/condensation heat of vapor compression refrigeration (VCR) cycle in air condition system of buildings is adopted for adsorption/desorption process of DAC. Thermal performance of a 4-step temperature swing adsorption process (TSA) is analyzed at various adsorption/desorption temperatures by using different adsorbents. Analysis on Coefficient of Performance (COP) of VCR cycle is also conducted in search for a balance between adsorbent and refrigerant. Taking both real working capacity and COP into consideration, Mg-MOF-74&R134a is the best choice for more amounts of CO2. Real working capacity of Mg-MOF-74 is up to 0.38 mol•kg−1 at 70 °C, which is twice as much as that of zeolite 13X. While zeolite 13X&R134a shows the best performance of two cycles in view of exergy efficiency and COP, which could reach 81.9% and 7.21, respectively, at 35 °C. These matches will provide some guidelines for the practical application of the combination of DAC with heating, ventilation and air conditioning (HVAC).

A critical research topic is the improvement of the system performance by efficiently cooling carbon dioxide in transcritical vapor compression cycles. In this study, a distributed compression cycle system (DCCS) is proposed. For the DCCS, the transcritical CO2 from the gas cooler outlet is not further subcooled but boosted. It is then cooled by conventional heat sink conditions. The DCCS performance under different operating conditions with variations in the second boost ratio is calculated by a thermodynamical cycle model. It is shown that the DCCS can effectively improve the system performance compared with the baseline system, with the maximum refrigeration COP increase ranging from 8.2% to 10.76% at a constant gas cooler outlet temperature. The refrigeration capacity is increased up to approximately 26%. The maximum refrigeration COP increase ranges from 8.57% to 13.51% at a constant evaporating temperature. The ideal second boost ratio requirements in DCCS are not high, and the additional system power consumption for the second boost is not more than 20% compared with the baseline system. The DCCS still has advantages in terms of the system COP compared with current systems that only adopt a single subcooling technology. The proposed DCCS provides a new path for improving and refining the performance of the carbon dioxide transcritical vapor compression cycle systems.

Copyright of Transactions the Japan Society of Refrigerating & Air Conditioning Engineers is the property of Japan Society of Refrigerating & Air Conditioning Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Machining stainless steel produces a high temperature in the cutting zone, leads to a decrease in the tool's longevity and also adversely affects the surface quality of the workpiece. Conventional cooling techniques are not effective in achieving better surface finish and less tool wear formation. This research introduces a novel refrigeration cycle-based workpiece cooling process to improve the machinability of AISI 304 stainless steel. The influence of this method in cutting zone temperature, surface roughness, tool wear formation and workpiece microstructure were compared with those of dry machining. The experimental results demonstrate that the proposed method provides a better surface finish, reducing roughness by 9 %, lowering the cutting zone temperature by 24 %–60 %, and minimizing wear on cutting tools under specific machining conditions. These findings can offer valuable insights for the manufacturing industry.

• A hybrid solar cooling system for refrigerator vehicle is studied. • The system is primarily run by PV-operated DC compressor. • AC compressor which is run by vehicle electrical source support the DC compressor. • Detailed electrical characteristics of the PV modules is modelled and validated. • Detailed thermodynamic and heat transfer analysis of the system is analyzed. This study focused on investigating the annual performance of a novel hybrid solar-driven cooling system that can be used on refrigerator vehicles. The cooling system is mainly driven by a DC compressor which is powered by a PV array, while an AC compressor which is powered by the car alternator assists the cooling system when the cooling load is higher than the capacity of the DC compressor. Detailed electrical modeling of the PV panels in the array is performed based on an algorithm that comprises a set of mathematical equations and is validated against the manufacturer's test data. The detailed transient electrical power generation of the PV array is analyzed. The effect of solar irradiation and ambient temperature on the performance of the PV modules is presented. Considering the refrigeration cycle, detailed thermodynamics and heat transfer analysis on the cycle are carried out. The effect of ambient temperature and refrigerator compartment temperature on the performance of the refrigeration cycle is investigated. It is concluded that an increase in ambient temperature decreases the performance of both the PV panel and the refrigeration cycle. While an increase in refrigerator compartment temperature increases the performance of the refrigeration cycle. [ABSTRACT FROM AUTHOR]

The refrigeration cycle of an air source heat pump system is an important information that reveals critical operating data, such as the cooling capacity, power consumption, and performance of a system during operation. Operating data, such as refrigerant pressure and enthalpy in situ, can be difficult to measure. Therefore, this study developed an in situ refrigeration cycle measurement method using the airside data of an air source heat pump. A method for measuring the refrigeration cycle is proposed using the characteristics of evaporation, compression, condensation, and expansion processes. The distance function was analyzed by normalizing the difference between the refrigerant pressure and enthalpy of the existing and proposed measurement methods. In addition, the distance function for the maximum error of the pressure and enthalpy measurement devices was analyzed and compared with the distance function of the entire data used in the evaluation. All the evaluation data had low distance function values with a maximum difference of 5%, confirming the reliability of the proposed refrigeration cycle measurement method. The power consumption and calculated COP were also evaluated using the proposed method. The Mean Bias Error (MBE) of power consumption and COP were 0.15% and 0.04%, and the coefficient of variation of root-mean-square error (CvRMSE) was 8.967% and 7.14%, respectively. [ABSTRACT FROM AUTHOR]

This work aims to develop an advanced control strategy for a thermal management system (TMS) with both passive and active cooling/heating for an electric bike (e-bike) to primarily maintain temperatures of key powertrain components, including battery, inverter, motor, charger, and DC/DC converter. To establish the control strategy, various commands used in the TMS are first categorized into two types, binary commands (for valve control) and analog commands (for fan, pump, and compressor control). Next, the TMS control strategy is designed as the combination of a High-Level Controller (HLC) and a Low-Level Controller (LLC). The binary commands are derived using HLC, which takes ambient conditions, and temperatures of heat generated components as the inputs. Meanwhile, the LLC is used to calculate the analog commands through fuzzy inferences, after taking the outputs of HLC, ambient conditions, temperatures of the motor and battery, and electric power consumption of pumps as the inputs. A plant model of the e-bike powertrain integrating regenerative braking features with the TMS is built to support the control development and evaluation. Numerical simulations under the HWFET drive cycle have been carried out to realize the performance of the TMS using the proposed control strategy in terms of managing the key components’ temperatures and their power consumption.

An overview analysis of research and development in the field of air and refrigeration low-flow compressors based on low-speed long-stroke piston stages is presented and an assessment of scientific and technological prerequisites for improving their energy efficiency and competitiveness is carried out. Two promising directions are considered in which such compressors can find effective application: increasing the gas pressure from atmospheric pressure to medium and high pressures; implementation of combined processes of compression and condensation of refrigerants in the working chamber of the stage. A number of scientific problems have been proposed and substantiated, the solution of which will make it possible to create competitive compressor units applicable in refrigeration and cryogenic engineering, thermostatting and life support systems, medicine and pharmaceuticals, petrochemical and oil and gas industries, small-scale energy, transport.

Domestic refrigerators have caused various energy-related issues for years. Replacing old refrigerants, using more flexible components, and reducing power consumption have been the main concerns of manufacturers. It is an improper use of energy and resources to implement each new change in the construction of the refrigeration cycle by trial and error. Therefore, virtual labs can assist designers in investigating potential changes before implementing that in practice. This work describes the procedure by which a flexible software is developed to simulate each component of the refrigeration cycle and predict the desired variables in an efficient time. In this software, the amount of refrigerant charge and the degree of superheat are provided as input variables; geometrical parameters for each component are considered in detail. The tube-by-tube and map-based methods are implemented to model the heat exchangers and compressor, respectively. Heat transfer between the suction line and capillary tube is simulated as well. Eventually, the performance parameters with all thermodynamic properties of the cycle at any arbitrary location can be reported as outputs. The case studies showed that the coefficient of performance will increase from 1.58 to 2.1, and from 2 to 2.2 by tuning the suction-line-heat-exchanger and evaporator fan speed, respectively.

In this paper, an exergoeconomic and exergetic sustainability analysis of a dual-pressure organic Rankine cycle (ORC) and vapor compression refrigeration cycle (VCRC) driven by waste heat is performed for power generation and cooling production. In addition, the most suitable fluid couple among the thirty-five different fluid pairs was investigated for the proposed combined system. The results indicate that the highest energy utilization factor, exergy efficiency, the system coefficient of performance, and net power are calculated for the R123-R141b fluid pair. In terms of exergetic sustainability indicators, the best performance results are obtained for the R123-R141b fluid combination. The minimum unit electricity generation cost and the shortest payback period are calculated as 0.0664 $/kWh and 2.5 years, respectively, for the R123-R290 fluid pair. The system component with the highest exergy destruction is the boiler, with 21.67%. The result of the parametric analysis showed that the thermodynamic performance parameters increase with the increment of the ORC's boiling temperature. In addition, with the increasing boiling temperature, the environmental effect factor of the system decreases, while the exergetic sustainability index increases. Additionally, as the boiling temperature increases, the total system cost increases, while the unit electricity production cost and payback period decrease. It is suggested to use a R123-R141b fluid couple among fluid pairs created as a result of thermodynamic, exergoeconomic and sustainability analysis. [ABSTRACT FROM AUTHOR]

The compressor is one important component in the transcritical CO2 (carbon dioxide) refrigeration cycle. The CO2 compressor has a small volume at the same refrigeration capacity because its refrigeration capacity per unit volume is large. The radial compressor often used in the CO2 refrigeration cycle has complex internal flow and difficult blade modeling. The paper presented a new centrifugal compressor with radial flow, whose blades are straight and easy to process. Taking a single stage compressor blade for example, the effects of the velocity coefficient, energy head coefficient, rotational speed of the moving blade, blade height, inlet radius and radial distance of the blade on the efficiency and pressure ratio were studied. According to the conclusions, the paper designed and simulated the blades of two compressors of the transcritical CO2 two-stage refrigeration cycle. Simulation result showed that the efficiencies of the two compressors were respectively 84.97% and 87.23%.

Since the last decade of the 20th century, there has been increasing attention to the use of CO 2 as a working fluid in transcritical refrigeration and cooling cycles. Transcritical cycles suffer from a heavy expansion loss, requiring specific means for its mitigation. Moreover, most applications for cooling or refrigeration are cooling a stream that is not changing phase, therefore has a finite heat capacity and does not well match with the evaporation curve of any pure fluid. In this work, to overcome these limitations (low COP and poor matching of heat exchanges curves) the potential of using a second component, mixed with CO 2 , has been assessed. For this purpose, several fluids have been investigated, from synthetic refrigerants, such as R1233zd(E) or R1234yf, to hydrocarbons, such as n-butane, or n-pentane and alcohols, like dimethyl ether. To investigate the effects of the addition of the second element in the CO 2 transcritical cycles, several configurations have been investigated, from the base refrigeration cycle to the double evaporator ejector cycle. All examined mixtures show a COP improvement with respect to pure CO 2. However, the mixture with R1234yf has the flattest evaporation curve and hence, in the case of a constant specific heat of the fluid to be cooled, gives the best result. The quantity of R1234yf that must be added to the mixture never exceeds 15%. [ABSTRACT FROM AUTHOR]

An important part of technical education is the presentation of processes through experiments and demonstration tools. This direct sensual experience is one of the sources of knowledge acquisition. The illustration provides a deeper understanding of the curriculum, making the cognitive process more intense. In this study we present a refrigerator model we have designed and implemented. Measurements are then performed on a real refrigerator to study the compressor refrigeration process. The locations where data were acquired are shown on the model. [ABSTRACT FROM AUTHOR]

The refrigeration cycle of an air source heat pump system is an important information that reveals critical operating data, such as the cooling capacity, power consumption, and performance of a system during operation. Operating data, such as refrigerant pressure and enthalpy in situ, can be difficult to measure. Therefore, this study developed an in situ refrigeration cycle measurement method using the airside data of an air source heat pump. A method for measuring the refrigeration cycle is proposed using the characteristics of evaporation, compression, condensation, and expansion processes. The distance function was analyzed by normalizing the difference between the refrigerant pressure and enthalpy of the existing and proposed measurement methods. In addition, the distance function for the maximum error of the pressure and enthalpy measurement devices was analyzed and compared with the distance function of the entire data used in the evaluation. All the evaluation data had low distance function values with a maximum difference of 5%, confirming the reliability of the proposed refrigeration cycle measurement method. The power consumption and calculated COP were also evaluated using the proposed method. The Mean Bias Error (MBE) of power consumption and COP were 0.15% and 0.04%, and the coefficient of variation of root-mean-square error (CvRMSE) was 8.967% and 7.14%, respectively.

Copyright of Journal of Refrigeration is the property of Journal of Refrigeration Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Refrigeration Technology is the property of Shanghai Society of Refrigeration and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In the current work, thermodynamic examination for cogeneration of electricity and cooling based on a polymer exchange membrane (PEM) fuel cell was carried out. To the waste energy in the fuel cell, an absorption refrigeration unit is employed in two modes with ejector and without ejector. This system includes a PEM-FC, an absorption refrigeration unit, a hydrogen storage tank, an ejector, and an air compressor. The produced thermal energy in the fuel cell is received entirely by a working fluid and is given to the absorption chiller generator. The system simulation was carried out from two perspectives of energy and fuel saving. Findings showed that the energy efficiency of the combined cooling and power (CCP) unit and the CCP system equipped with the ejector (CCP-E) was 63.72% and 78.33%, respectively. It indicated that adding the ejector to the system increases the energy efficiency of the system by 23%. The fuel economy percentages of the CCP system and CCP-E were 44.43% and 45.9%, respectively. The results also showed that adding the ejector in the refrigeration system increases the system performance by up to 44%. The presence of the ejector causes the working fluid flow in the evaporator to increase with the suction of the secondary flow, and the cooling capacity increases significantly. Moreover, with increasing generator and evaporator pressure, the suction ratio of the cooling system equipped with the ejector decreases and increases, respectively. • Development of a combined cycle based on the PEM-FC and H 2 storage system. • Comparative analysis of two refrigeration cycles integrated with PEM-FC. • The energy efficiencies of the CCP and the CCP-E were 63.72% and 78.33%. • Using ejector in the absorption chiller cycle increases the COP by up to 44%. [ABSTRACT FROM AUTHOR]

The energy efficiency of the hydrogen liquefaction process is studied, and a general model of the hydrogen liquefaction process is built for analyzing the energy efficiency and the influence of multiple parameters. Energy and exergy analysis models of the typical single-pass cycle and multiple-pass cycle are developed. The specific relationships among the parameters and energy efficiency of the total liquefaction system are deduced. A hydrogen liquefaction process with precooling nitrogen and cryogenic helium cycles is studied. For the precooling and cryogenic cycles, the SEC and net power consumption of the cryogenic helium cycle have different variation trends along with the precooling temperature and hydrogen liquefaction ratio. Their optimal values are identified to be −194 °C and 0.9453, and the corresponding SEC, exergy efficiency, total capital expense, and total annual cost are 3.619 kWh/kg LH2 , 33.44%, 82.58%, 8.263 M$, and 531.62 M$/yr, respectively. The proposed model can be used in the design and operation stages to analyze the variation of energy efficiency along with multiple parameters of the hydrogen liquefaction process. • General model is developed for analyzing the energy efficiency of the hydrogen liquefaction process. • Relationships between operating parameters and energy/exergy efficiency of refrigeration cycles are deduced. • Influences of precooling temperature and hydrogen liquefaction ratio are analyzed for a liquefaction process. • The specific energy consumption and exergy efficiency are 3.619 kWh/kg LH2 and 82.58%. [ABSTRACT FROM AUTHOR]

Natural gas, that has been processed and met certain specifications, is sent to consumers through pipeline. Gas condensation within the pipeline should be avoided because it has negative impacts. Hydrocarbon dew point is a measure of the easiness of gas condensation. To meet the hydrocarbon dew point, heavy hydrocarbon should be extracted in dew point control unit (DPCU). The extraction is done by gas cooling in gas chiller followed by separating the liquid formed in low temperature separator (LTS). The gas chiller functions as an evaporator in the DPCU refrigeration cycle. Propane is a common refrigerant in the DPCU. In addition, ammonia is also a potential refrigerant due to its normal boiling point being close to the hydrocarbon dew point. Refrigeration cycle performance depends on evaporator temperature, condensor temperature, and the inherent pressure-enthalpy (PH) characteristic of the selected refrigerant. This study aimed to compare the performance from ammonia and propane against the change of evaporator and condenser temperature. This study was a dry research using Aspen Hysys V11.0 simulation software (academic license). The refrigeration cycle was a simple cycle with fixed variables in the form of evaporator load, saturated liquid at outlet condenser, and saturated vapour at outlet evaporator. This study indicated that at the same evaporator load, evaporator temperature, and condenser temperature, ammonia refrigeration cycle was better than the propane because coefficient of performance (COP) of ammonia was higher than propane. This study also modeled COP changes of propane and ammonia as mathematical equation. Quantitatively, it appeared that COP of propane was more sensitive than ammonia against both evaporator and condenser temperature changes. Keywords: ammonia; condenser; evaporator; propane; refrigeration cycle; simulation A B S T R A K Gas alam yang telah diolah dan sesuai spesifikasinya dikirim ke konsumen melalui pipa. Kondensasi gas dalam pipa harus dihindari karena menimbulkan dampak negatif. Titik embun hidrokarbon menjadi ukuran kemudahan proses kondensasi gas. Untuk mencapai titik embun hidrokarbon yang diinginkan, maka hidrokarbon berat harus diekstraksi di dew point control unit (DPCU). Ekstraksi dilakukan dengan cara mendinginkan gas di gas chiller lalu memisahkan cairan yang terbentuk di low temperature separator (LTS). Gas chiller tersebut berfungsi sebagai evaporator pada siklus refrigerasi DPCU. Propana adalah refrigeran yang umum digunakan di DPCU. Selain itu, amonia juga menjadi refrigeran yang potensial karena kedekatan titik didih normalnya terhadap titik embun hidrokarbon yang diinginkan. Performa siklus refrigerasi dipengaruhi oleh temperatur evaporator, temperatur kondensor, dan karakteristik tekanan-entalpi (PH) yang melekat pada refrigeran yang dipilih. Penelitian ini bertujuan untuk membandingkan performa siklus refrigerasi propana dan amonia terhadap perubahan temperatur evaporator dan kondensor. Penelitian ini merupakan penelitian kering yang menggunakan perangkat lunak simulasi Aspen Hysys V11.0 (lisensi akademik). Siklus refrigerasi yang digunakan adalah simple cycle dengan variabel tetap berupa beban evaporator, kondisi cair jenuh outlet kondensor, dan kondisi uap jenuh outlet evaporator. Hasil penelitian ini menunjukkan bahwa pada beban evaporator, temperatur evaporator, dan temperatur kondensor yang sama, maka siklus refrigerasi amonia lebih baik dari propana karena COP amonia lebih tinggi dari propana. Penelitian ini juga memodelkan nilai COP propana dan amonia sebagai persamaan matematika. Secara kuantitatif, terlihat bahwa COP amonia lebih stabil dari propana terhadap perubahan temperatur evaporator dan kondensor. Kata kunci: amonia; evaporator; kondensor; propana; siklus refrigerasi; simulasi

Experimental absorption refrigeration equipment with a generator driven by waste heat was manufactured and tested, with 2,2,2-trifluoroethane/1-methylpyrrolidine as the working fluid pair. A plate generator was used to reduce the heat transfer distance and to decrease the start-up time. However, the flow paths of the plate generator were not large enough to separate the refrigerant vapor from the two-phase flow. Therefore, a gas-liquid separator was introduced, and a cooling coil was embedded as a partial condenser in the separator to cool the refrigerant vapor and to condense the absorbent contained within it, thus increasing the concentration of the refrigerant vapor. The separator successfully separated the refrigerant from the solution in all tested conditions. The cooling rate of the partial condenser was varied from 143 to 222 W by changing the flow rate of cooling water. Then, a calculation model for the partial condenser was constructed to analyze its characteristics. In the calculation model, the helical coil partial condenser was modeled by being divided into 10 horizontal columns. It was assumed that only the solution phase had the concentration distribution from the bulk flow to the liquid-vapor interface. We show that a heat and mass transfer area of 0.04 m2 is needed to achieve an outlet vapor concentration of 0.95.

In this study, a thermodynamic analysis of an industrial cabinet designed for industrial cabinet systems used in the food industry and providing simultaneous heating and cooling has been made. During the study, energy and exergy analyzes were carried out by using the engineering equation solver program to thermodynamic analysis of seven different refrigerants in the system designed by determining the mass-flow rate to obtain 10 kW heating power, which was selected by using the coolselector two program by using the refrigerant temperature values and operating pressure values. The condenser dew point temperature was kept at +30 °C and the evaporator dew point temperature was kept at -1 °C. Calculations were made under atmospheric conditions by keeping subcooling at -2 °C, superheating at +5 °C, and ambient temperature at 20 °C. The coefficients determining the system performance were obtained for the highest R22 refrigerant and the lowest for R513A refrigerant. The exergy heating efficiency was obtained in the highest R22 and lowest R407C refrigerants, respectively. The calculated exergy cooling efficiencies were observed to be the highest R407C and the lowest R513A, respectively. The results of the study are presented in graphics. It has been revealed that the most suitable fluid in the designed industrial cabinet system is the system using R22. [ABSTRACT FROM AUTHOR]

A theoretical investigation is presented about a double evaporator ejector refrigeration cycle (DEERC). Special attention is paid to take into account the influence of the sub-cooling and superheating effects induced by an internal heat exchanger (IHX). The ejector is introduced into the baseline cycle in order to mitigate the throttling process losses and increase the compressor suction pressure. Moreover, the IHX has the structure of a concentric counter-flow type heat exchanger and is intentionally used to ensure that the fluid at the compressor inlet is vapor. To assess accurately the influence of the IHX on the DEERC performance, a mathematical model is derived in the frame of the dominant one-dimensional theory for ejectors. The model also accounts for the friction effect in the ejector mixing section. The equations of this model are solved using an Engineering Equation Solver (EES) for different fluids. These are: R134a as baseline fluid and other environment friendly refrigerants used for comparison, namely, R1234yf, R1234ze, R600, R600a, R290, R717 and R1270. The simulation results show that the DEERC with an IHX can achieve COP (the coefficient of performance) improvements from 5.2 until 10%. [ABSTRACT FROM AUTHOR]

• For modeling non-equilibrium condensation, the wet steam multi-phase model is used. • Water is applied in ejector refrigeration cycle as economical and non-toxic fluid. • Effects of droplets injection at secondary flow causes reducing COP and ER. • In special case, the steam accompanies by droplets at the outlet of ejector. • Designers and operators should consider effects of droplets in ejector performance. Steam ejector plays a key role in the refrigeration system. The water has been used as a working fluid because water is more economical and non-toxic. The operating fluid often enters the evaporator as a water liquid and droplets evaporate by absorbing heat. Cooling load changing causes the vapor in the outlet of the evaporator to be accompanied by droplets. Therefore, there are droplets at the inlet of secondary nozzle and flow should be simulated as a wet steam flow with injection droplets at the secondary flow. In this paper, the effects of droplets injection at secondary flow have been investigated on the performance of the refrigeration cycle. For this purpose, the Eulerian-Eulerian method has been used and the results have been validated with experimental data. Six cases are considered with different wetness and number of droplets in the secondary flow. The results of case 6 show COP, T ¯ outlet , and ER decrease about 22.93%, 15.66%, and 22.93%, respectively. In addition, the steam accompanies by droplets at the outlet of ejector. Therefore, it is essential for designers and operators to model and consider the effects of the droplets on the wall erosion to optimize the wet steam ejector and refrigeration cycle performance. [ABSTRACT FROM AUTHOR]

The paper presents the results of studying a combination of new technological solutions in the processes of natural gas liquefaction and helium extraction. The most common and effective way to ensure cooling capacity in the natural gas liquefaction process is to use a cascade cycle on mixed refrigerant (MFC) as external cooling. The influence of introducing an absorption refrigeration unit on the technological process has been studied. To extract helium, the combined separation and rectification method is used. The purity of helium obtained is 50% (in moles). The running conditions of operation and the corresponding technical characteristics of the devices are presented and described. The curves of the resulting characteristics of heat exchangers indicate the correctness of the thermohydraulic calculations performed. The relative value of energy costs for obtaining 1 kg of liquefied natural gas in a technological process using MFC is 0,265 kWh/kg of LNG introducing an absorption refrigeration unit into the cycle reduces the ratio presented to 0,1849 kWh/kg of LNG. In the process of extracting helium using an absorption refrigeration unit gives the result of 0,951 and 132,9 kW/kmol of helium respectively. When using an absorption refrigeration unit, the helium extraction rate and power consumption ratio are 0,951 and 132,9 kW/kmol of helium, respectively. Application of the exergic analysis methods to the processes under consideration shows that the greatest value of exergic losses relative to other devices is observed in compressors. A detailed economic analysis has been carried out. It shows that the cost of the product obtained in the normal MFC cycle and in the MFC cycle using an absorption refrigeration machine is $0,1939 and $0,2069 per kg of LNG, respectively. Finally, on the basis of such economic factors as the cost of electricity and the cost of the product, the efficiency of the new cycle was analyzed

Elastocaloric refrigeration technology is considered one of the most promising new high-efficiency refrigeration technologies for replacing conventional vapor compression technology, owing to its high refrigeration efficiency and specific refrigeration power. This paper analyzes and discusses the thermodynamic basis, dynamic theory, materials, and refrigeration cycle as a reference for investigations of the elastocaloric effect of rubber. According to the literature, natural rubber features the best elastic and thermal properties, with a strain of 600% at 0 °C and a maximum temperature change of 12 K. Twisting natural rubber results in a higher temperature change and can reduce the volume of the refrigeration system. When the strain is 300%, the maximum temperature change is 12.9 K, which is 5.4 times that of the untwisted rubber. Theoretical studies regarding the elastocaloric effect of rubber are relatively mature; however, the development of cooling prototype is limited. Further development is required to promote the practical application of elastocaloric refrigeration technology using natural rubber as the working medium. Thus, it is possible to claim that using natural rubber in elastocaloric refrigeration technology is promising.

Distillation is the separation of components in a gas-liquid mixture using the difference in volatility. The distillation-type oil separator developed in this study combines the principles of traditional oil separation and distillation. The feed conditions of a constant pressure of 1 000 kPa in the tower, inlet temperature of 62 °C, and mass ratio of R134a and PAG of 7:3 were simulated using Aspen simulation software. The results show that the lubricating oil in the binary mixture can be removed by the distillation process. In this study an experimental setup was built to test the efficiency of the oil separator to verify its practical feasibility. The effects of the refrigerant circulation flow rate and the top cooling volume on the separation efficiency of the oil separator were investigated separately. The results showed that the oil separation efficiency was as high as 99.967% at a refrigerant mass flow rate of 7.5 g/s and a maximum cooling capacity of 200 W. From the experimental and simulation results, it was determined that introducing the distillation principle into the oil separator for the separation of the refrigerant-lubricant mixture can improve its separation efficiency. The separation efficiency of the distillation-type oil separator was 9.17 % higher than that of a conventional oil separator.