bluuebunny/crossref_metadata_2025_split huggingface dataset:
Numerical-experimental investigation of liquid slugging in the suction muffler of a hermetic reciprocating compressor
Authors: Bianchi M , Deschamps C J , Rodrigues T T , Paladino E E 
Published: September 2021

Abstract
Refrigerant in the liquid phase and lubricating oil that circulate in refrigeration systems may reach the compression chamber of compressors. This phenomenon of liquid slugging is detrimental to reciprocating compressors because it can damage valves and other components. A three-dimensional Eulerian multiphase model was developed using the software ANSYS CFX to predict the gas-liquid flow in a simplified suction muffler geometry. In addition, an experimental bench was designed to allow the injection of specified volumes of lubricant oil into the suction muffler and measurement of the volume that reaches the muffler outlet. The liquid slugging was observed through glass windows positioned in the test section and recorded with a high-speed camera. Measurements showed that the phenomenon of liquid slugging is random and that the volume of liquid reaching the muffler outlet increases with the oil injection pressure. The numerical model was able to predict the oil volume that reaches the muffler outlet in agreement with measurements in the case of high injection pressures, but it overpredicted the volume when the injection pressure was decreased. The visualization showed changes in the liquid phase morphology that are difficult to predict since closure models for a two-fluid model are typically developed for dispersed morphology.
Experimental analysis of reed valve movement for different reed valve designs tested in an impact fatigue test system
Authors: Tofique Muhammad Waqas , Löf Alexander , Millward Chris 
Published: September 2021

Abstract
Impact fatigue is a phenomenon that is the main cause of failure of reed valves in compressor systems. This phenomenon occurs in compressors due to repeated opening and closing of reed valves during suction and exhaust cycles of compressors. When the valve opens it creates bending fatigue stresses in the body of reed valve; when the valve closes it strikes against the valve plate creating impact stresses. This reed valve movement and impact is repeated billions of times. This cyclic movement influences the impact fatigue life of the reed valve and, hence, the performance of a compressor. The valve movement can be defined in terms of valve frequency, valve lift, valve velocity and impact velocity. Inside a reciprocating compressor, a number of parameters including the valve design, valve material, compressor operating frequency and suction/exhaust pressure influence the reed valve movement.
In this paper, we studied the valve movement parameters for three different suction reed valve designs manufactured from Flap-X – a martensitic stainless steel grade developed for reed valves – tested in a custom-built impact fatigue test system. The valves were excited into movement using compressed air pulses varying in frequency up to 300 Hz and varying pulse width. The valve displacement and frequency was recorded by a laser sensor at 10 000 frames per second. Before starting each test, the operating conditions such as the operating frequency and the air pulse width were pre-set in the impact fatigue test system’s control software while the applied pressure was kept constant during the test. The valve response was measured to be different for the different valve designs tested in this study. The reed valve design influenced the important reed movement parameters such as the valve lift, valve velocity, impact velocity and the frequency of valve vibrations. The valves were not tested to failure as the focus of this study was to collect the dynamic data of valve movement. However, for a practical impact fatigue testing of the reed valves intended to achieve fracture of valves, the testing should be conducted at higher frequencies to reduce test times as well as for a stable amplitude of vibration and impact velocity as shown in this study. The information obtained from this study shows the applicability of the presented impact fatigue test system to study the reed valve movement as well as their impact fatigue characteristics.
Continuous Cooling Compressor for water refrigerant heat pump
Authors: Shoyama T. , Sun H. , Kawano B. , Matsui M. 
Published: September 2021

Abstract
A turbo compressor was developed for water refrigerant heat pumps equipped with continuous cooling compression, in which the vapour is continuously cooled during the compression process by the latent heat of evaporation of the liquid water refrigerant sprayed into the impeller channels. One of the disadvantages of water refrigerant is that the discharge temperature during vapour compression is higher than that of fluorocarbon refrigerant. Multi-stage compression with intercooling are one of the solutions, the system becomes large. In continuous cooling compression, fine particles of water are sprayed from a nozzle embedded inside the impeller, and the water vapour in compression process is directly cooled to the saturation temperature. Therefore, if sufficient amount of spray is present, the compression process follows the saturation line in p-h diagram. Water is supplied to the spray nozzle after pressurized to 10 MPa or more using the centrifugal effect of rotor rotation. A small nozzle was developed that suppresses rotor imbalance and can withstand the load of centrifugal force. A followability index was defined as a reference for the droplets to follow the vapour flow and evaporate before colliding with the blade surface. A water-refrigerant heat pump system was constructed, and the degree of superheat of the discharged vapour was evaluated while changing the spray amount. Increasing the amount of spray decreased the superheat but COP also decreased. Saturated compression was demonstrated above a certain amount of spray, but the impeller flow was choked due to the droplet evaporation. It is desirable to assume a sufficient choke margin, or to develop a special CFD code that can take into account the droplet evaporation.
Geometric Optimisation of a Coupled Vane Compressor
Authors: Chen Q J , Ooi K T 
Published: September 2021

Abstract
The coupled vane compressor (CVC) is a rotary compressor with two coupled vanes which slide diametrically through the rotor during operation. As compared to most other rotary vane compressors, this CVC works well with small rotor-to-stator diameter ratio, typically less than that for all existing rotary compressors (>0.7). Hence, CVC has probably the most compact design among all rotary compressors, thus saving materials and manufacturing cost. This compressor is intended for use in room air-conditioners and refrigerators. Currently, mathematical model and measurement have been carried out to determine the working characteristics of this compressor. In this paper, a genetic algorithm with constraints handling has been devised and linked with the verified mathematical model of the CVC to search for a set of geometrical parameters which produces highest COP when working in the refrigeration cycle. During this optimisation search process, the significant design variables such as rotor radius, cylinder radius, vane thickness and valve reed thickness are allowed to vary.
In this paper, the details on the application of the optimization process, constraints handling and descriptions, objective function definitions as well as the details of optimization implementation will be presented and discussed. Results obtained will be shown and deliberated. The results show that this optimization study reconfirms the value of optimisation in compressor design.
Design optimization and test of the novel FeTu ‘compander’, utilising organic fluids within a closed cycle for HVACR applications
Authors: Subert J , Fenton J P , Hinchliffe K , Arbon I M 
Published: September 2021

Abstract
HVACR performance is influenced by the efficiency of the compression and expansion process. The ability to operate oil-free; with non-toxic, inert, natural working fluids such as air or CO2 holds high environmental value.
This paper presents data of the FeTu™ compander operating in a closed cycle, for means of heating and cooling. A novel system, where compression and expansion is a continuous and simultaneous process; inherently regenerating energy to assist the compression process by expanding within a positive displacement chamber. This study documents the oil-free performance with organic working fluids pertaining to HVACR applications.
Commercial 1D modelling software; GTSuite (GTS) is used to optimise cooling capacity (Q) and Coefficient of Performance (CoP). Different volume ratios (VR), pre-charge pressures, temperature inputs (ΔT) and running speeds are analysed. A multi-faceted test rig is built to compare and validate all performance data against the GTS fluid model which, once calibrated, can then be used with a high degree of certainty in predicting the performance of other applications and ΔTs. Increasing the system pre-charge pressure has a proportional impact on capacity, so this phenomenon is tested to consider the conflicting impacts of higher pressure against increased viscosity, with respect to volumetric efficiency.
The CoP of the system ranges from 1 to 5 across typical HVACR ΔTs. Low VR offers highest CoP but lowest Q, so the optimal trade-off is explored. The strengths & weaknesses are then comparatively documented against incumbent vapour cycle systems.
Comparison of Two Reverse-cycle Defrosting Methods for a R290 Split Room Air Conditioner
Authors: Du Y J , Wu J H , Wang C , Lei B W 
Published: September 2021

Abstract
R290 has obvious advantages in aspects of environmental protection and thermal properties, and researches on R290 room air conditioners (RACs) are attracting more and more attention. As for R290 RAC, the suction temperature is continuously low and a large number of refrigerants are dissolved in the compressor oil sump during defrosting process, resulting in a longer time length of the start-up process after defrosting. Two reverse-cycle defrosting methods, the discharge-throttling method (DTM) and suction-discharge bypass method (SDBM) are proposed in order to solve these problems. This paper compares the two defrosting methods on an R290 RAC by experiment and the results show that the defrosting time of DTM is relatively short, but the temperature at the inlet and outlet of the indoor heat exchanger is relatively low after defrosting. The SDBM can alleviate the situation of low suction temperature in the defrosting process, but the viscosity of the oil sump is large in the early stage of defrosting and the time length of the start-up process after defrosting is longer. Both methods have their own advantages and disadvantages, and the paper will provide an experimental basis for the reliability study of R290 RACs.
Part load performance of single and two stage compressors — a comparative experimental study in a R410A chiller unit
Authors: Inampudi S , Botticella F , Elbel S 
Published: September 2021

Abstract
The rising cooling needs for the residential and commercial air conditioning sectors and the requirement of higher SEER values increased the focus on energy efficient part load performance. Although several studies exist on the topic of capacity modulation, there is no comprehensive study that compares different modulation strategies in the same experimental facility. In a first step, this paper aims to experimentally compare two different capacity controls for scroll compressors (single speed vs two stage compressor) using the same R410A water chiller having a nominal cooling capacity of 8kW. The tests were conducted according to AHRI Standard 551/591 (2018). The Integrated Part Load Value (IPLV.SI) was used to fairly compare all the different capacity modulation strategies. Based on the experimental results, differences on the order of 8% in IPLV.SI are found.
A study into the impact of chloride ions on the make-up hydrogen compressors
Authors: Fouladivanda M , Heidary M A 
Published: September 2021

Abstract
The presence of unwanted chemicals in process lines and downstream equipment causes defects and failures, which sometimes have significant impacts on systems and imposes extra costs for the production process. In this study, one pair of four-stage make-up hydrogen compressors is investigated. These reciprocating compressors which serve as a part of the hydrogen treating unit have failed approximately simultaneously. The feed of these compressors is net hydrogen-rich gas from the Pacol process. Both dry compressors have shown similar problems in the first and second stages. The simultaneous rise in the cylinder temperature and decrease in the flow has forced shut-down of the compressors for the next actions in the process. Initial inspections have revealed some kind of deposits covered the cylinder and its components. The valves, liquid tested and results have shown significant leakage of all the suction and discharge valves of the cylinders. Moreover, the thickness of all piston rings have decreased up to 50 percent which is more than allowable values. The compositions of deposits, tested by X-ray fluorescence (XRF) and X-ray diffraction (XRD), result from the analysis shown that it contains 35.2 percent (mass fractions) of Chlorine and 27.5 percent of Iron, and noticeable amount of Sulfur or Phosphor. XRD analysis has reported that the Iron Chloride Hydrate is the main part of the fouling sample. In this paper, the impact of the aforementioned chemicals on the compressor components are investigated, and some approaches are proposed to absorb or inhibit these chemicals.
Basic design procedure for an internally geared screw compressor
Authors: Read Matthew 
Published: September 2021

Abstract
The internally geared gerotor type of positive displacement machine is widely used for pumping applications, but can also be used to achieve internal compression or expansion of a working fluid. A further development of this configuration is the application of helical twist to the inner and outer rotors. Previous studies have shown that this can decrease the power transferred between rotors, and increase the relative maximum flow areas at the inlet and discharge ports. There are possible benefits to this configuration when compared to conventional twin-screw machines, including reduced leakage area, stiffer rotors, and co-directional thermal expansion of rotors. However, no experimental data is currently available for this configuration, and optimising the geometry of the gerotor screw machine requires a detailed understanding of the porting, leakage flows and mechanical losses. An experimental programme is being conducted to investigate the influence of these factors on performance. This paper discusses preliminary results from geometrical analysis leading to a simple design procedure. The basic design of an internally geared air compressor is demonstrated, based on the operation characteristics of a conventional twin screw machine.
A study on the kinematics of a new Schukey-type rotary compressor
Authors: Cui B , Becker K , Lüdersen U , Gottschlich M , Kabelac S 
Published: September 2021

Abstract
A new type of rotary compressor, called “rotary-chamber compressor”, consists of two interlocking rotors with 4 wings each, that perform non-uniform rotary movements. Both rotors have the same direction of rotation, while one rotor is accelerating, the other rotor is retarding. After surpassing a specific mark, the sequence changes and the leading rotor begins to retard and vice versa. Due to the resulting relative phase difference, the volume between the two wings is changing periodically, which allows pulsating working chambers. The technology was first introduced by its founder Jürgen Schukey in 1987. Since then, no further development on this machine is known to us except our own. In this contribution, a study on the kinematics of the rotary-chamber-compressor is presented. Initial studies have shown that changes in the kinematics of the rotors will have a direct influence on the thermodynamical variables, which, if optimized, can lead to an increased performance of the machine. Therefore, a mathematical model has been developed to obtain the performance parameters from different kinematic concepts by using numerical CFD analysis. Furthermore, additional optimization possibilities will be listed and discussed.
Time parametrizations in long-range interacting Bose-Einstein condensates
Authors: Konishi Eiji 
Published: September 2021

Abstract
Time-reparametrization invariance in general relativistic space-time does not allow us to single out a time in quantum mechanics in a mechanical way of measurement. Motivated by this problem, we examine this gauge invariance in the ground state of the quasi-stationary coarse-grained state of a long-range interacting closed system of identical or identified, macroscopic, and spatiotemporally inhomogeneous Bose–Einstein condensates in the thermodynamic and Newtonian limits. As a result, we find that it is a theoretical counterexample of this gauge invariance, except for proper-time translational invariance, at a coarse-grained level.
Associations of Family Distress, Family Income, and Acculturation on Pediatric Cognitive Performance Using the NIH Toolbox: Implications for Clinical and Research Settings
Authors: Thompson Ryan C , Montena Alexandra L , Liu Kevin , Watson Jessica , Warren Stacie L 
Published: September 2021

Abstract

Objective
There is a growing recognition that the use of conventional norms (e.g., age, sex, years of education, race) as proxies to capture a broad range of sociocultural variability on cognitive performance is suboptimal, limiting sample representativeness. The present study evaluated the incremental utility of family income, family conflict, and acculturation beyond the established associations of age, gender,maternal years of education, and race on cognitive performance.

Method
Hierarchical linear regressions evaluated the incremental utility of sociocultural factors on National Institutes of Health Toolbox in a nationally representative sample of pre-adolescent children (n = 11,878; Mage = 10.0 years; Adolescent Brain Cognitive Development Study). A regression-based norming procedure was implemented for significant models. Paired sample t-tests were used to compare original and newly created demographically corrected T-scores.

Results
Nearly all regression models predicted performance on the NIH-TB subtests and composite scores (p &lt; .005). Greater family income and lower family conflict predicted better performance, although the effect sizes were small by traditional standards. Acculturation scores did not explain additional variance in cognitive performance. Lastly, there were no significant differences between the original and newly created demographically corrected T-scores (Mdiff &lt; 0.50).

Conclusions
The present study highlights that, although family income, family conflict, and acculturation have been shown to routinely influence cognitive performance in preadolescent children, the NIH-TB appears to be highly robust to individual differences in sociocultural factors in children between ages 9 and 10. Contextual and temporal implications of the present results are discussed.
Effects of chronic and acute predation risk on sexual ornamentation and mating preferences
Authors: Frommen Joachim G , Thünken Timo , Santostefano Francesca , Balzarini Valentina , Hettyey Attila 
Published: September 2021

AbstractPhenotypic plasticity is widespread in animals. Still, how plastic responses to predator presence affect traits under sexual selection and influence mating preferences is not well understood. Here, we examined how simulated chronic predator presence during development and acute predator presence during mate choice affect the expression of male secondary sexual traits and female mating preference in the three-spined stickleback, Gasterosteus aculeatus. Males reared under chronic predator presence developed less intense red breeding coloration but showed higher courtship activity than males that grew up in a predator-free environment. Acute predator presence during mate choice trials did not influence male behavior or ornamentation. Predator presence experienced during development did not affect female mating preferences, whereas acute predator presence altered preferences for male courtship activity. Male body size and eye coloration influenced the intensity of female mating preferences, while the trait changing most in response to predator presence during development (red coloration) had no significant impact. The observed interplay between developmental plasticity in male ornamental traits and environment-dependent female mating preferences may lead to dynamic processes altering the strength and direction of sexual selection depending on both the chronic and acute risk of predation. These processes may contribute to the maintenance of within- and among-population variation in secondary sexual traits, and may, ultimately, facilitate speciation.
Cross talk: trafficking and functional impact of maternal exosomes at the feto-maternal interface under normal and pathologic states
Authors: Tantengco Ourlad Alzeus G , Radnaa Enkhtuya , Shahin Hend , Kechichian Talar , Menon Ramkumar 
Published: September 2021

AbstractFetal cell-derived exosomes promote inflammation in uterine and cervical cells to promote labor and delivery. However, the effect of maternal exosomes on fetal cells is still not known. We tested the hypothesis that cervical cells exposed to infectious and oxidative stress (OS) signals produce exosomes that can induce inflammation at the feto-maternal interface (FMi). Exosomes isolated from medium samples from human ectocervical epithelial cells (ecto), endocervical epithelial cells (endo), and cervical stromal cells (stroma) in normal cell culture (control) or exposed to infection or OS conditions were characterized based on morphology, size, quantity, expression of tetraspanin markers, and cargo proteins. Human decidual cells, chorion trophoblast cells (CTC), chorion mesenchymal cells (CMC), amnion mesenchymal cells (AMC), and amnion epithelial cells (AEC) were treated with control, LPS-, or OS-treated cervical exosomes. Enzyme-linked immunosorbent assay for pro-inflammatory cytokines and progesterone was done to determine the recipient cells’ inflammatory status. Ecto, endo, and stroma released ∼110 nm, cup-shaped exosomes. LPS and OS treatments did not affect exosome size; however, OS significantly increased the number of exosomes released by all cervical cells. Cervical exosomes were detected by fluorescence microscopy in each target cell after treatment. Exosomes from LPS- and CSE-treated cervical cells increased the inflammatory cytokine levels in the decidual cells, CMC, AMC, and AEC. LPS-treated stromal cell exosomes increased IL-6, IL-8, and progesterone in CTC. In conclusion, infection and OS can produce inflammatory cargo-enriched cervical exosomes that can destabilize FMi cells. However, the refractoriness of CTC to exosome treatments suggests a barrier function of the chorion at the FMi.