Refrigeration Compressor Research Articles

Experimental investigation and regression analysis on the characteristics of the JT refrigerator operating with natural refrigerant mixtures

This paper presents the results of the analysis of the experimental characteristics of the closed-cycle Joule-Thomson (JT) refrigerator operating on a nitrogen-hydrocarbon refrigerant mixture. Designing such energy-efficient refrigeration machines involves the calculation and experimental determination of the optimal values of the “charge” composition of the mixture components. The design process must take into account the change in the “circulating” composition of the mixture components. In the paper, we present the results of regression analysis of the “circulating” composition of the mixture components of a JT low-performance refrigerator (compressor volumetric flow rate less than 25 m3/h). Such refrigerators can be used for thermostatting objects at the temperatures down to −160 °C. The results are given in the form of relationships for specific refrigeration capacity and a number of efficiency indicators. In the considered component concentration range, the relative root-mean-square regression error was less than 12.6 %. Finally, we determined the optimal concentrations of the mixture components of the JT refrigerator having a compressor with a volumetric flow rate of 4.36 m3/h which corresponds to the maximum value of specific refrigerating capacity Qt/Ve [19,87 W/(m3/h)] at the temperature of the evaporator inlet of −150 °C. The results of approbation the proposed regression method on a prototype low-temperature freezer based on a JT refrigerator operating with MMR and the limits of applicability of the developed regression models are determined. These relationships provide valuable insights for designing stock-produced devices of varying standard sizes, reducing development time and cost while leveraging comparable operating cycles and working body compositions.

A Universal Mixing Rule for the High-Pressure Viscosity of Oil/Refrigerant Mixtures

Abstract Bearing life analysis for the rolling element bearings in refrigeration compressors requires an accurate estimate of the film thickness. An alternative is offered here to the experimentally challenging pressure–viscosity measurements of oils diluted by refrigerants or the film thickness measurements of the same in an optical rig.

Выбор способа снижения трения в разрабатываемых для импортозамещения ротационных холодильных компрессорах

The article discusses one of the methods for reducing friction, used for newly developed rotary compressors as part of import substitution work. The experience of using rotary refrigeration compressors is analyzed and the main factors determining refrigeration capacity are identified. Methods used in aerospace engineering and power engineering to reduce friction and increase the service life of mechanical elements and assemblies using metallic and non-metallic materials have been identified, and the most promising materials and development trends have been analyzed. A fairly common method of reducing friction, based on the weariness effect, is chosen for study. Based on already known results, a technical solution based on the wear-free effect has been proposed to reduce friction of a refrigeration compressor with a rolling rotor.

Measurement of Ammonia Leakage by TDLAS in Mid-Infrared Combined with an EMD-SG Filter Method

Ammonia (NH3) has been used as the main refrigerant in various types of cold storages, exceeding 90% of cooling applications. However, NH3 leakage occurs frequently due to damage of the refrigeration compressor, resulting in environmental pollution and intoxication accidents. Therefore, reliable and highly sensitive NH3 detection is a critical requirement in cold storage. In this paper, tunable diode laser absorption spectroscopy (TDLAS) is used to measure NH3 leakage, where a new denoising method combining empirical mode decomposition with the Savitzky-Golay smoothing algorithm (EMD-SG) is proposed to improve the signal-to-noise ratio (SNR) of absorbance signals. The results show that a 5.5 times improvement of SNR and 86% reduction of the linear fitting error in calibration is obtained; furthermore, this system achieves a detection limit of 0.2 ppm at an average time of 69 s by Allan variance analysis. Hence, it can be concluded that the EMD-SG algorithm can effectively improve the performance of TDLAS systems to meet the requirements for NH3 leakage detection in cold storages.

Possibility of replacing two-stage refrigeration compressors with low-speed ones

Possibility of replacing two-stage refrigeration compressors with low-speed ones

Surrogate model-based multi-objective design optimization of vibration suppression effect of acoustic black holes and damping materials on a rectangular plate

The acoustic black hole (ABH) is a ground-breaking passive technology for vibration reduction and noise attenuation, characterized by its ability to manipulate flexural waves. When multiple two-dimensional ABHs are embedded in an irregular shaped complex plate structure used in engineering, such as the support plate of a refrigerator compressor, its vibration characteristics often cannot be solved through analytical or semi-analytical methods, resulting in the inability to carry out subsequent ABH optimization design. To address this issue, we propose a high-precision modelling method that combines surrogate models with finite element methods to construct a vibration characteristic database of the compressor support plate embedded with multiple ABHs in all design spaces of the ABH and damping materials geometric parameters using limited sample data. A high-precision surrogate model was constructed based on the vibration response data of the ABH plate under 50 parameter combinations of ABH and damping layer, and the fitting accuracy of the surrogate model was verified through vibration response data under another 25 parameter combinations. Based on the constructed surrogate model, the Multi-objective Genetic Algorithm (MOGA) was employed to optimize the five parameters of ABH and damping layer simultaneously, aiming to maximize the vibration reduction effect of the ABHs. Our investigation reveals that the optimized ABH and damping materials significantly improve the vibration suppression effect in a wide frequency range compared to the unoptimized structures. Finally, experimental verification was conducted to solidify the accuracy and efficacy of our approach in enhancing vibration reduction effect for irregular shaped complex plate structures using acoustic black holes.

Comparative study on performance of counter-flow dew-point indirect evaporative cooling systems via a more realistic and experimentally validated three-dimensional model

Dew-point indirect evaporative cooling (DPIEC) technology is designed and applied as a low carbon-emission and high energy-efficient air conditioning (AC) solution without employing non-environmentally friendly refrigerant and mechanical compressor for cooling in building sector. A more realistic three-dimensional (3-D) model of the DPIEC that better captures the fundamental thermodynamic of its operation is proposed. It considers the variability of air thermal properties and is employed to investigate the DPIEC's performance for three possible arrangements. The 3-D model is classified as configurations 1, 2 and 3 based on the relative flow direction between primary/secondary air and spray water. Experimental results indicate that the model can well evaluate the thermodynamic performance. Additionally, the influence of crucial factors on the performance is parametrically studied by employing three performance indexes. Comparison reveals that configuration 1 can achieve the highest effectiveness and cooling capacity. Results also show that the secondary-to-primary air ratio should be confined to around 0.3 to achieve maximum cooling capacity, and the optimal channel gap should be limited to the range from 3 to 4 mm. Comparatively, the relative flow direction between the spray water and the primary/secondary air has a greater effect on the thermodynamic performance than the spray water inlet velocity.

Substantiation of the possibility of gas liquefaction in oil–free low–speed refrigeration compressors

BACKGROUND: Existing refrigeration machines contain four main units, i.e., compressor, condenser, expander, and evaporator that perform the refrigeration cycle. Currently, the liquefaction of the refrigerant occurs in the condenser. The creation of the conditions under which condensation of the working fluid would occur in the compressor unit would make the development of a compact refrigeration machine possible by eliminating the condenser from it.
 AIMS: This work aims to investigate the possibility of creating a compact refrigeration machine with the implementation of the condensation process of the working fluid in the compression chamber of the compressor.
 MATERIALS AND METHODS: The object of the study is a low–speed compressor, in which the pressure ratio significantly exceeds known analogs and simultaneously the temperature is significantly lower than that of high–speed machines because of the creation of conditions under which compression occurs with polytropic indicators below 1.08. The research method involves determining the gas temperature at critical pressure and comparing the obtained result with the critical temperature. The system of equations and assumptions used relates to the model with lumped parameters of the working fluid.
 RESULTS: The results obtained on the compression of such refrigerants as ammonia, carbon dioxide, R12, R22, and Freon–134a showed the possibility of obtaining the required pressures in a low–speed machine at temperatures significantly below the critical temperature.
 CONCLUSIONS: This work examines and proposes to study further those working fluids of refrigeration machines that can go into the liquid phase in a low–speed compressor unit because of their characteristics and operating parameters in the refrigeration machine. Further experimental confirmation of this will enable partial or complete elimination of the condenser unit in the refrigeration machine.

Analysis of Flexibility Potential of a Cold Warehouse with Different Refrigeration Compressors

The research into new approaches to shift from fossil fuels to renewable energy sources (RES) has surged as environmental issues are on the rise, and fossil fuel sources are becoming scarce. The flexibility potential of cold supply systems has been discussed widely in the literature, firstly due to their high share of electricity consumption worldwide and secondly because of their potential to store thermal energy in the form of cold energy. However, finding a clear definition of flexibility and a concise approach for its quantification is still under progress. In this work, a comprehensive definition of the flexibility of energy systems and a novel methodology for its quantification are introduced. The methodology was applied on a cold warehouse with real data regarding its cold energy demand. The cold warehouse was first modeled via oemof, which is a modular open source framework developed in Python 3.8 using a mixed integer linear programming (MILP) optimization approach. The operation optimization of the cold warehouse was conducted for three goals, namely “minimization of electricity costs”, “minimization of CO2 emissions”, and “minimization of maximum used electric power (peak load minimization)”. Additionally, the effect of using different types of refrigeration compressors on the optimized operation of the cold warehouse was investigated. The results suggest that a cold warehouse possesses a high level of flexibility potential, which can be taken advantage of to reduce the electricity cost by up to 50%, the CO2 emissions between 25% to 30%, and the maximum used electric power by 50%. Different compressor types produced very similar results, although their flexibility level may vary.

Polymeric Coatings With Superior Tribological Performance for Lightweight Materials in HFO-1234yf Refrigerant

As global warming concerns continue to rise, research has shifted toward developing more climate-friendly refrigerants for air-conditioning and refrigeration compressors, with HFO-1234yf being a prominent candidate. In line with the need for lightweight engineering in electric vehicles, advanced composite coatings are necessary to improve the surface properties of parts and system components made from light metals such as magnesium and aluminum, which typically have poor tribological performance. This study investigates the tribological performance of advanced polymeric coatings (aromatic thermosetting copolyester [ATSP]-, polytetrafluoroethylene [PTFE]-, and polyether ether ketone [PEEK]-based) on lightweight aluminum alloy substrates in the presence of HFO-1234yf refrigerant and polyalkylene glycol (PAG) lubricant under starved lubrication conditions. Using a high-pressure tribometer, scuffing pressure, friction, and wear experiments were conducted, with all three coatings exhibiting excellent tribological performance compared to the bare substrate. Notably, PEEK and ATSP coatings demonstrated superior performance with high load-to-failure, low coefficient of friction, and negligible wear. Results also showed ATSP to have superior durability against a broad range of stress levels, while PEEK coating partially wears out at higher stress levels. These findings provide valuable insights for developing robust coatings on lightweight materials for high-stress applications.

Eco-efficiency analysis and intensification of cryogenic extractive distillation process for separating CO2–C2H6 azeotrope through vapor recompression strategy

The cryogenic extractive distillation process for CO2-ethane separation from natural gas involves four distillation columns in series and a rather high amount of energy from boiler and refrigeration compressors. This study proposes the intensification of a real plant located in China using a vapor recompression (VR) strategy to revamp it. The conventional process and the intensification configurations were designed by simulation in UniSim software. A utility plant with cooling water, steam generation, and propane refrigeration sections was also considered for realistic results regarding water consumption, CO2 emissions, and utility costs. Additionally, in order to establish an overall means for performance analysis, such indicators were grouped in a joint evaluation approach using the Comparative Eco-Efficiency Index. Results show that the VR1 scheme applied between the depropanizer condenser and the deethanizer reboiler provides savings of 24.2 % and 24.5 % in energy and water consumption, respectively; therefore, savings of 25.5 % and 21.4 % in CO2 emissions and utility costs were achieved, respectively, which increased the process's eco-efficiency by 41.9 %. As a point of interest, 33 months are necessary to recover the corresponding investment on the compressor and heat exchanger.

ANALISA HASIL UJI KOMPRESOR SISTEM REFRIGERASI MENGGUNAKAN INVERTER

One of the largest uses of electrical energy is electrical energy used in air conditioning. Electrical power consumption for air conditioning has a figure of about 50-60% of the total electrical energy consumption of a building. In the industrial world, air conditioning or refrigeration systems are used to maintain the temperature conditions of raw materials or products produced with the intention of extending storage life through the cooling process. Refrigeration systems use compressor motors as a medium to circulate refrigerant throughout the system. This study aims to compare three parameters in a refrigeration system that uses an inverter on its compressor motor compared to a conventional refrigeration system. The three parameters are electrical power, cooling capacity and COP (Coefficient of performance). The research was conducted using an analysis-based method of existing systems. Data collection was carried out twice in steady conditions. The results of this study obtained the following data: The use of inverters in refrigeration compressors decreased electrical power by 18.3% increased COP in refrigeration systems by 44.1% and increased cooling capacity by 31.2%.

Two-phase lubrication characteristics of journal bearing in refrigerant-oil system under high-pressure environment considering gaseous cavitation

The journal-bearing system is crucial for the reliability of refrigerant compressors that operate under high-ambient-pressure environments. The pressure changes rapidly, which hereby results in the variation in solubility of refrigerant in oil, and causes gaseous cavitation of the refrigerant-oil mixture in the bearing. However, the cavitation mechanism under high-pressure environments is not well understood, and its impact on lubrication characteristics has been rarely discussed. In this paper, a numerical model is developed to simultaneously solve the gaseous cavitation and two-phase lubrication problems. The first systematic comparison of lubrication characteristics for constant-eccentricity journal bearings, in such a special environment, between the classical Reynolds boundary and gaseous cavitation boundary is presented. Results indicate the load-carrying capacity is reduced by about 3% at a lower eccentricity of 0.3, but is greatly enhanced by about 21% at a higher eccentricity of 0.9 due to the gaseous cavitation. Meanwhile, the ‘reverse’ flow rate is found to reach -0.057 at the end side of the bearing owing to sub-ambient pressure up to -1 MPa at the eccentricity of 0.8. The cavitation-induced sub-ambient pressure should be addressed for the design of the bearing operating in such pressurized refrigerant environments as ambient gas might be sucked into the bearing.

Performance analysis of automotive air conditioning systems with electric compressors using R1234yf refrigerant: Insights into power consumption, cooling capacity, and energy efficiency

R1234yf, a low global warming potential (GWP) refrigerant, offers a promising alternative to traditional refrigerants like R134a. This study analyzes automotive air conditioning systems (AAC) equipped with electric compressors and utilizing R1234yf refrigerant. The interrelationships between refrigerant charge, compressor speed, power consumption, cooling capacity, and energy efficiency are examined. The results show that increasing refrigerant charge and compressor speed leads to higher power consumption due to increased compressor work. However, higher refrigerant charges and compressor speeds improve cooling capacity in line with heat transfer principles. As refrigerant charge and compressor speed increase, the energy efficiency, measured by the Coefficient of Performance (COP), tends to decrease, indicating a trade-off between cooling capacity and energy efficiency. Optimizing refrigerant charge and compressor speed is crucial to strike a balance between cooling performance and energy efficiency. R134a outperforms R1234yf, with an average percent difference in COP approximately 25% higher at all compressor speeds. This study contributes to the understanding of AAC system performance and guides the development of energy-efficient automotive air conditioning. Future research can further explore system components and conditions to enhance energy efficiency and advance air conditioning technology.

Performance improvement of twin screw refrigeration compressors for chillers by modifying the suction arrangement

To improve the efficiency of the twin-screw refrigeration compressor at a high speed of about 3000 rpm, the suction arrangement was investigated in this paper. Several simplified CFD models of a twin-screw refrigeration compressor for chillers were established to parametrically analyze the influence of the suction delay, rotor wrap angle, and suction bearing distance. The parametric studies showed that the volumetric efficiency could be improved by 3 % by a suction delay of 18°, and more volumetric efficiency could be improved by shortening the length of it. The optimal delay angle was found to be linear with the rotational speed. Increasing the wrap angle from 300° to 330°, the volumetric efficiency decreased by 2–3 %, and the adiabatic efficiency increased by about 0.2 %. By increasing the distance between the suction bearings and the rotor end face from 5 mm to 80 mm, the isentropic efficiency increases by about 1.4 %. Based on the parametric studies, two modified machines were built and tested by experiments. Experimental results showed that the volumetric efficiency of machines #1 and #2 increased by 1.5 % at 3000 rpm. The isentropic efficiency of machine #2 increased by 0.78 % at 3000 rpm and 1.27 % at 3300 rpm.

Performance of hybrid electric vehicle air-conditioning using SiO2/POE nanolubricant

The automobile air-conditioning (AAC) system uses the most energy among all auxiliary components in hybrid electric vehicles (HEV) with an electrically-driven compressor (AAC-EDC). Incorporating nanolubricant improves AAC-EDC performance and reduces battery and AAC component size. This study aims to assess the performance of an AAC-EDC system by employing SiO2/POE nanolubricants. The performance of the AAC-EDC was examined using SiO2/POE with a volume concentration of up to 0.01 %, a refrigerant charge of 120–160 g, and a compressor speed of 1200–3840 rpm. The performance of the AAC system was measured by its heat absorption, compressor work, coefficient of performance (COP), and EDC power consumption. The SiO2/POE was stable for 30 days with a zeta potential of 102.5 mV. The SiO2/POE demonstrated superior performance over the pure POE lubricants. The compressor work and power consumption were reduced to 26.17 % and 11.97 %, respectively. The lowest expansion valve discharge temperature of 9.6 °C was achieved at 160 g refrigerant charge and compressor speed of 3840 rpm. The nanolubricant attained the highest COP of 3.36 at 1860 rpm speed and 160 g charge. The SiO2/POE nanolubricant with a volume concentration of 0.01 % is highly recommended for optimal performance in the AAC-EDC system.

Experimental investigation of usage of POE lubricants with Al2O3, graphene or CNT nanoparticles in a refrigeration compressor.

In this study, the use of nanolubricants containing Al2O3, graphene, and carbon nanotubes (CNTs) at different mass fractions in a refrigeration compressor was experimentally investigated. The required electrical power of the compressor was measured to determine the effect of the use of nanolubricants. Nanoparticles used in the preparation of nanolubricants were gradually added to the lubricant to determine the optimum nanoparticle mass fraction for each nanoparticle type. Thus, it was found that the compressor operated safely and efficiently with nanolubricants. Furthermore, the optimum mass fractions were determined to be 0.750% for Al2O3, 0.250% for graphene, and 0.250% for CNTs for operating conditions of this study. As a result, the required electrical power of the compressor decreased by 6.26, 6.82, and 5.55% with the addition of Al2O3, graphene, and CNT nanoparticles at optimum mass fractions of 0.750, 0.250, and 0.250% to the lubricant, respectively, compared to the compressor using pure oil. Moreover, density and dynamic viscosity of the nanolubricant samples used in the experiments were also measured, and their kinematic viscosity, which is an important parameter for lubricants, was calculated. It was determined that the kinematic viscosity continuously increased with increasing nanoparticle fraction. In conclusion, nanolubricants containing nanoparticles above the optimum mass fraction increase the required electrical power of the compressor. It is concluded that nanoparticle fractions should not be used above the optimum value in nanolubricant applications.

Semi-supervised diagnosis method of refrigeration compressor hidden defect based on convolutional transformer autoencoder model

Improving product quality and service life by diagnosing defects in compressors through vibration signal analysis of the compressor's shell is challenging due to strong noise interference and limited labeled samples. The paper proposed a semi-supervised diagnosis method based on the convolution Transformer autoencoder (CTAE) for diagnosing hidden defects with small samples and strong noise. Firstly, an optimized variational modal decomposition is utilized to decouple and reduce noise from the raw vibrations, and the decomposition results are concatenated with the vibration signals as input to the model; Secondly, the CTAE is employed to learn the feature distribution of unlabeled samples and to extract and fuse local and global features from the input data; Finally, a labeled samples are used to fine-tune the model and to fuse features from multi-sensor information. The results of using a compressor dataset for validation show that the proposed method has high diagnosis accuracy and robustness with limited labeled samples and different signal-to-noise ratios.

Advances in liquefied natural gas processes

Over the past 30 years, a considerable world trade in LNG has developed. Today, LNG represents a significant component of the energy consumption of many countries and has been profitable to both the exporting host countries and their energy company partners. The attention of LNG producers have now been directed towards improved production. All latest plants have been sized around this number. Some of them have been designed by optimizing existing layout, other brand new and few required the optimization of centrifugal compressors and so the introduction of some novelty to maximize production given a certain driver. Improvements in the aerodynamic design have been necessary to maximize efficiency and increase operating range; advanced rotordynamic design to handle more capacity, new casings to increase design pressure and reduce the number are some of the innovations introduced to advance LNG operations. Novelties have not been limited to main refrigerant compressor but also to auxiliaries such as Boil Off Gas (BOG), CO2, End Flash. Eventually also new drivers have been qualified for LNG plant operations and other are under study for its high efficiency and possible future application. Extensive application of modular construction techniques will reduce the time and cost of construction in remote areas of the world. This article aims to explain, in layman terms, LNG basic knowledge, exploration, production and advancement. Throughout the article, references have been drawn from a wide range of resources and author’s personal industry experience. It is intended to use the article as a vehicle to share oil & gas industry knowledge with a wide range of audience.

Experimental and numerical investigation of a compact vapor compression refrigeration system for cooling of avionics in harsh environments

The power density and heat dissipation requirements of electric/electronics devices have significantly increased due to miniaturization. This is especially critical with the emergence of the “more electric aircraft concept” (MEA), which demands higher heat dissipation. The future thermal management systems must possess high heat removal capability and effectively handle heat loads of individual components in line with MEA objectives. Moreover, they should perform optimally in the highly dynamic and harsh aviation environments, e.g. elavated temperatures. Compact vapor compression refrigeration (VCR) systems have garnered interest as they excel in eliminating high heat flux and keeping device temperatures lower to ensure better performance in challenging environments. This paper presents the design, development, and testing of a compact VCR system applicable at the device level. The studied compact refrigeration system, with dimensions of 600 mm × 400 mm × 250 mm and weighing 2.8 kg, utilizes R134a as its working fluid and incorporates a miniature refrigeration compressor. It achieves heat dissipation of up to 623 W at an ambient temperature of 50°C, attaining a COP of 2.7 while maintaining device temperatures lower than or close to ambient levels. Through simulations and experiments, the system's dynamic performance is assessed under varying heat loads and ambient temperatures. Experimental validation of the model has been carried out at various conditions. Overall, the proposed compact vapor compression system proves to be an excellent solution for thermal management in harsh conditions, aligning well with the requirements of the modern electric aircraft concepts.