Compressor Discharge Research Articles

Study of Heterogeneous Plasma Created by Magneto-Plasma Compressor and Erosive Capillary Discharge

Magneto-plasma compressor with a pulsed capillary erosive plasma generator (MPC-EP) has been designed, manufactured and tested at the first time. This MPC-EP was used to study the physical properties of a high-energy long-lived heterogeneous plasma (ELHP) created by pulsed capillary erosive plasma generator (EP) at the wide range of pressure and temperature. The results of measurements of the parameters of the shock wave created by the MPC-EP, as well as optical spectroscopy and soft X-ray spectroscopy are presented.

INVESTIGATION OF CONJUGATED HEAT TRANSFER FOR A RADIAL TURBINE WITH IMPINGEMENT COOLING

Radial turbine is widely used in micro-turbines, turbochargers, small jet engines and expanders, and the pursue of high system efficiency has resulted in elevated turbine inlet temperatures for some of its applications, threatening its reliability. There are, however, few cooling studies on radial turbines. This paper studies the jet impingement cooling of a turbocharger radial turbine. A small amount of air (coolant), which could come from compressor discharge cooled by an intercooler, is injected through a few jet holes on the heat shield of the turbine onto the upper part of turbine backdisc, to cool the rotor blades and the backdisc. Parameters that may affect the cooling were studied by a Conjugated Heat Transfer (CHT) numerical simulation using steady flow calculations. The influences to the cooling effects by different coolant-to-turbine mass flow ratios, Coolant-to-turbine inlet temperature ratio, number of the jets etc. were analysed by a steady flow simulation. The simulation results show that, when four jet holes are placed at blade leading edge radius, using 1.0% ~ 3.0% of the main gas mass flow of coolant, the average temperature on leading edge, inducer hub and backdisc surface is reduced by 2K ~ 17K,27K ~ 65K and 51K ~ 70K respectively. Turbine efficiency is mostly reduced little over 1% point.

Performance and Optimization Study of R290 as Alternative Refrigerant for R22 in Low Temperature Heat Pump System

This paper mainly studies the replacement performance of R290 in R22 low temperature heat pump system from the experimental point of view. By comparing the performance differences under different working conditions, it is found that when R22 is directly extracted from the original system and filled with R290, the heat capacity and COP of the system are attenuated, and the compressor discharge temperature and pressure of the R290 system are higher than those of the original R22 system in low temperature environment. Through the analysis of the system components, it can be considered that the main reason for the above phenomenon is that the compressor displacement of the R22 system is too large and does not match the R290 system. Therefore, in order to meet the safety requirements of the system and improve the overall performance of R290 in the low temperature heat pump system at the same time, it is considered to replace the compressor with a smaller displacement which is more matched with R290 in the system. The experimental results show that the compressor displacement optimization of the R290 low temperature heat pump system can effectively reduce the exhaust temperature and pressure of the system and improve the overall performance of the system. The COP of the optimized R290 low temperature heat pump system is 6.5% higher than that of the original R22 system, and the exhaust temperature in the low temperature environment is reduced by 36% to below 80 C.

Experimental research on the concentration distribution characteristics of dual-temperature refrigeration system using R290/R600a based on separation condensation

• Experiments were studied to obtain R290/R600a concentration distribution behavior. • Linear relationships between circulation and charged concentration are discovered. • Experimental prediction correlations on the circulating concentrations are obtained. • Variations of mixture concentration as operation parameters are analyzed. In this paper, R290/R600a dual-temperature refrigeration system based on separation condensation approach with two evaporators is experimentally investigated. Refrigerant concentration distribution characteristics of zeotropic mixture R290/R600a are obtained through gas chromatography method. Moreover, the difference between charged concentration and circulating concentration are explored. The results show that circulating refrigerant concentration at different sampling positions deviate from charge refrigerant concentration. The circulating refrigerant concentration of low boiling component R290 at compressor discharge port is 11.9% higher than its charged concentration. Based on the analysis of refrigerant concentration deviation relationship, the experimental prediction correlations on circulating refrigerant concentrations are obtained. In addition, the effects of operation parameters including compressor frequency and ambient temperature on concentration distribution are also investigated. The present work provides a guide for refrigerant circulating concentration prediction and selection of charged refrigerant composition. Furthermore, this could reveal an in-depth understanding on refrigerant circulating concentration distribution characteristics.

Alternative positions of internal heat exchanger for CO2 booster refrigeration system: Thermodynamic analysis and annual thermal performance evaluation

• Three CO2 booster systems with different locations of IHX are proposed. • Thermodynamics models of booster systems are developed and annual performance is studied. • S1 is the optimal solution system to improve COP, which is enhanced by 0.6% - 6.36%. • By adding IHX, the APF of CO2 booster system can be improved significantly. • IHX can improve annual performance in subtropical and tropical climatic regions. Refrigeration systems running on transcritical CO 2 cycle are considered an alternative to phase-down the use of hydrofluorocarbons (HFCs) in response to the Kigali Amendment. Responding to the need to improve the efficiency of CO 2 booster systems and to identify optimum system designs, thermodynamic models of three booster systems are proposed with the use of an internal heat exchanger (IHX). Findings from this study suggest that placing the IHX with a low-temperature fluid side at the suction line of high pressure stage compressor and high-temperature fluid side at the outlet of gas cooler represents the most optimal approach in improving the coefficient of performance (COP) of the booster system. When operating in the transcritical conditions, the COP values can be improved by 6.35% at the IHX thermal effectiveness of 0.8 and by 6.48% at the ratio of medium temperature load to low temperature load of 6. Using IHX can significantly reduce the compressor discharge pressure, which can be reduced by 0.55 MPa at the ambient temperature of 40 °C. Furthermore, by adding IHX, the annual performance factor of CO 2 system can be improved significantly by 1.68% and the annual total power consumption can be decreased by 6.48% in the tropical climate. It can be concluded that IHX can improve the COP values of a booster system when operating in the subtropical and tropical regions.

Thermodynamic Analysis of Eco-Friendly Refrigerant Mixtures as an Alternative to HFC-134a in Household Refrigerator

Nowadays, research has been focused on refrigerants from Hydrofluorocarbons (HFCs), which are not harmful to the ozone layer. Because of replacing refrigerants from chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs). HFCs are used in many applications, including refrigerants, aerosols, solvents, and blowing agents for insulating foams. However, some HFCs have relatively high global warming potential (GWP) and are subject to further examination due to growing concerns about global climate change. The present work’s main objective is to select eco-friendly refrigerants from AC5, R430A and R440A, combining two or more refrigerants from HC, HFC and HFO groups as a direct substitute HFC-134a in a household refrigerator. The performance of the domestic refrigerator with liquid suction heat exchanger (LSHX) was compared in terms of compressor discharge temperature, coefficient of performance (COP), volumetric cooling capacity (VCC), and power consumption of a compressor. It was found that the average COP of R440A and R430A was higher by approximately 2.5% and 1.47% than HFC-134a. However, the COP of AC5 was 6.1% lower than that of HFC-134a. The VCC of R430A is almost equal to HFC-134a. The results also show that AC5, R440A and R430A consume less power than HFC-134a. The compressor outlet temperature with R440A, AC5 provide higher values than HFC-134a, which affects the compressor life. The best overall performance was achieved with the refrigerant R430A in the household refrigerator and suggested an alternative to HFC134a, which also has a very low GWP from the environmental safety perspective.

Influence of key parameters on the performance of a helium cryogenic system in refrigeration and liquefaction modes

At present, medium-scale helium cryogenic system is commonly based on modified Claude cycle with two expanders in series. In this study, considering the minimum allowable heat exchanger temperature difference (MHTDamd), the influence of key parameters (including compressor discharge pressure (Pcd) , temperature at the inlet of expander1 (Tin-EXP1) and temperature at the inlet of Joule-Thomson valve (Tin-JT)) on the system performance (including refrigeration capacity (RC)/liquefaction rate (LR), specific energy consumption (SEC) and total UA of the heat exchangers (UAtotal)) of the helium cryogenic system is investigated and analyzed in refrigeration and liquefaction modes, respectively. The results show that in refrigeration and liquefaction modes, the optimal ranges of Pcd, Tin-EXP1, and Tin-JT are within 8 ∼ 10 bar, 30 ∼ 45 K and 5.2 K ∼ 7.2 K, respectively. Furthermore, the constraint relation between UAtotal and SEC is obtained. By using genetic algorithm (GA), it is found that keeping constraint SEC within 100%∼115% of the chosen SEC from the optimal range can achieve a relatively economic trade-offs between SEC and UAtotal. In the end, a comparison of T-S diagram obtained from design and experimental values in refrigeration and liquefaction modes is carried out, respectively. The maximum temperature deviation is within 5%, which verifies the accuracy of the calculation models. The optimized results in this study are also applicable to the same processes with mass flow rate of compressor lower than 100 g/s.

Theoretical analysis on a variable interstage compressor matching CO2 two-stage refrigeration (VICMTR) system

In the two-stage refrigeration cycle, the interstage volume ratio between the low-stage and high-stage compressors is closely associated with the operating conditions and will determine the seasonal energy performance ratio (SEPR). In this study, a variable interstage compressor matching CO2 two-stage refrigeration (VICMTR) system is proposed. Five common matching options can be achieved by switching on the on–off valves in pairs and starting compressor in a compressor unit. The performance of these matching options and application feasibility in several cities are theoretically studied. The results indicate that the optimum matching can be obtained for the maximum coefficient of performance, maximum cooling capacity per compressor and low discharge temperature, respectively. H2L7 matching can recover more expansion work from expansion valve Ⅱ compared with other four matching options (HxLy, x and y are the basic quantities of high-stage and low-stage compressors). When the evaporation temperature is –48 °C, the SEPR of the VICTRM system in Beijing is 1.141, increased by 0.21% ∼ 1.87% compared with traditional fixed interstage matching system, the annual energy consumption is 63187.2 kWh, reduced by 0.19% ∼ 2.96%. The VICTRM system with eight compressors is suitable for moderate and warm climate cities. The proposed system can adapt to the variable ambient conditions in a year.

Thermodynamic Performance Analysis of Hydrocarbon Based Domestic Refrigeration System

The use of synthesized refrigerants has several environmental concerns. The most widely used substances like hydro fluorocarbons (HFCs), chlorofluorocarbons (CFCs) and hydro chlorofluorocarbons (HCFCs) have either high global warming potential (GWP), high ozone depletion potential (ODP) or long atmospheric life time. With the growing demand of healthier atmosphere, the study of other alternative substances is very important. This paper presents theoretical thermodynamic performance analysis of hydrocarbon based domestic vapour compression refrigeration system. Propane (R-290), isobutane (R-600a) and butane (R-600) were used. Then, the results were compared with the performance of currently most commonly used tetrafluoroethane (R-134a). These hydrocarbons have zero ODP and very negligible GWP. Different parameters, like coefficient of performance (COP), refrigeration effect, compressor work input and compressor discharge temperature were investigated. Evaporator and condenser temperatures, subcooling, superheating and compressor isentropic efficiency were the variables used for this study. MATLAB software has been used in the mathematical analysis. COP values were found comparable to that of R134a. All the hydrocarbons investigated gave beyond 150% refrigeration effect compared to R-134a for the same mass flow rate. But this was at the expense of higher compressor work input. This research also revealed that the compressor discharge temperature is much lower for R-600a and R-600. Generally, these hydrocarbons showed that they are a good alternative to R134a based on the thermodynamic point of view.

Experimental investigation of Al2O3 nanosuspension in vapor compression refrigeration system using tetrafluoroethane and iso-butane refrigerants

The indirect emissions due to energy consumption by refrigeration system has contributed potentially to global warming. The infusion of nanoparticle-based suspension (nanofluid) have shown significant improvement in heat transfer for refrigeration application with the noteworthy reduction in energy consumption. Experimental work was carried out with an aim to reduce indirect emissions from the refrigeration system. Thus, the present work consist of the performance investigation of aluminum oxide (Al2O3) nanoparticle suspension in a vapor compression refrigeration system with varying refrigerant mass charges. The refrigerants used for the experiment are tetrafluoroethane (R134a) which is high in GWP (Global Warming Potential) and isobutane (R600a) which has low GWP. Mineral oil (MO) and POE (Polyolester Oil) were used as the base fluid for the synthesis of Al2O3 based nanofluid with mass fractions of 0.02%, 0.04%,0.07%, and 0.1%.Varying mass charges of 150 gm, 180 gm, and 200 gm of R134a and R600a refrigerant were employed in the experiment to work with each mass fraction of nanofluid. The refrigeration system is designed to work within the cycle range of −6 °C to 30 °C for R134a and R600a refrigerant. Experimental results showed improvement in COP by 41.8%, reduction in power consumption 31.85%, increment in compressor discharge pressure by 12.56%, reduction in evaporator pressure by 3.94%, and reduction in pull-down time by 23.5% by using 200 gm of R600a-MO with 0.1 wt% of Al2O3 based-suspension. Also, there is a significant reduction in exergy destruction observed in a different component of the refrigeration system by using the nanosuspension compared to the pure refrigerant.

Measurement Method and Experimental Analysis of Liquid Entrainment for a Flooded Evaporator of a Water-Cooled Centrifugal Chiller Based on Energy Balance

Liquid entrainment in a flooded evaporator has an important impact on the performance and safety of a water-cooled centrifugal chiller. In this paper, two methods for measuring the liquid entrainment factor in the evaporator of a centrifugal chiller based on energy balance are proposed. Method 1 involves only the heat exchange capacity of the evaporator and Method 2 involves both evaporator and condenser. The applicable conditions of the methods are discussed. Experimental measurements on the flooded evaporator of a single-stage water-cooled centrifugal chiller with refrigerant R134a show that, for a system with good thermal balance, there is little difference in the entrainment factor values obtained by the two methods. Method 2 was found to have slightly higher measurement accuracy, compared to Method 1. The uncertainty propagation analysis shows that for Method 2, the inlet and outlet water temperatures of the evaporator and condenser, motor input power, motor efficiency, transmission power loss and compressor suction and discharge temperatures are important factors. The experimental results show that the variation of the evaporator entrainment factor with refrigerant charge amount is different for different cooling capacity. At 700 and 800 refrigeration ton (RT), the entrainment factor of the test evaporator increases with the increase of refrigerant charge and the growth rate gradually accelerates. For the chiller tested, when the entrainment factor reaches 0.89% and 1.02%, respectively, at 700 ton and 800 ton, the rapid increase of the entrainment factor leads to a significant decrease in the coefficient of performance (COP) during the charging process. Based on the analysis of the experimental results, it is recommended that the maximum entrainment factor for efficient operation of the centrifugal chiller should be controlled within 1%.

Energy Analysis of HFC-152a, HFO-1234yf and HFC/HFO Mixtures as a Direct Substitute to HFC-134a in a Domestic Refrigerator

Abstract The Kyoto protocol emphasized the need of replacement of HFC refrigerant due to their high GWP values that causes pollution in the environment. So in this paper the refrigerants R1234yf, R152a and HFOs/HFCs mixtures of R134a/R152a/R1234yf such as ARM42 (in the ratio of 8.5/14 /77.5 by mass), ARM42a (in the ratio of 7/11/82 by mass) with a view of replacement of the refrigerant HFC-134a in a domestic refrigerator were analyzed theoretically. Volumetric cooling capacity, compressor discharge temperature, coefficient of performance, compressor energy consumption and refrigeration capacity are the main parameters to estimate the performance of the refrigerator. The results are revealed that HFC-152a had gave a superior performance as compared to HFC-134a in terms of COP and equal cooling and volumetric cooling capacities. However, the refrigerant HFC-152a was flammable and runs with high compressor outlet temperature which may restrict its usage. The HFO refrigerant R1234yf showed an almost equal volumetric cooling capacity, compressor energy consumption, refrigerating effect and COP when compared with HFC-134a. Among the refrigerants ARM42 and ARM42a, the refrigerant ARM42a was selected as a good alternative for HFC-134a because the Volumetric cooling capacity and COP of ARM42a were almost equal to HFC-134a. Therefore ARM42a had better choice of direct substitute to HFC-134a in a domestic refrigerator when the corresponding safety requirements are adopted. So on overall comparison of every property of refrigerants we can conclude that R1234yf can be treated as best alternative to HFC-134a in a domestic refrigerator.

Mechanical and deformation characteristics of rotary compressor discharge valve

The discharge valve plays an important role in the rotary compressor. For better understanding the mechanical characteristics of discharge valve in the process of movement, a mechanical model considering the coupling effect with limiter is established. Some major parameters, i.e., displacement, stress, stiffness and elastic force, are obtained to characterize the mechanical properties of the discharge valve. Two cases of valve component are calculated by the mechanical model, and the results indicated that the profile of limiter has an important influence on the movement of discharge valve. In order to verify the accuracy of the model, finite element method and high-speed photography are used. The comparison results show the calculation error of valve stiffness obtained by the model is within 3.9% compared with the finite element method results, and the valve motion is consistent with the high-speed photography results. Based on the above analysis, the profile of limiter in one valve component is optimized. The initial winding displacement of the valve is advanced from 2.115 mm to 1.453 mm after the optimization of limiter profile, which exhibits better limiting effect.

A methodology for identifying the most suitable measurements for engine level and component level gas path diagnostics of a micro gas turbine

Recently, the utilization of micro gas turbines in smart grids are rising that makes the part-load operation principal situation of the engine service. This leads to faster life consumption that increases the importance of the diagnostics process. Gas path analysis is an effective method for gas turbine diagnostics. Complex dynamics of gas turbine induces challenging conditions to perform applicable gas path analysis. This study aims to facilitate MGT gas path diagnostics through reducing the number of monitoring parameters and preparation a pattern for engine level and component level health assessment in both full and part load operation of a recuperated micro gas turbine. To attain this goal a model is proposed to simulate MGT off-design performance which is validated against experimental data in healthy and degraded operation modes. Fouling in compressor, turbine and recuperator and erosion in compressor and turbine as the most common degradations in the gas turbine are considered. The fault simulation is performed by changing the health parameters of gas path components. According to the result investigation, a matrix comprises deviation contours of four parameters, Power, fuel flow, compressor discharge pressure, and exhaust gas temperature is presented and analyzed. The analysis shows that monitoring these parameters makes it possible to perform engine level and component level diagnostics through evaluating a binary code (generated by mentioned parameter variations) against the fault effects pattern in different load fractions and fault severities. The simulation also showed that the most power drop occurred under the compressor fouling by about 8.7% while the most reduction in thermal efficiency is observed under recuperator fouling by about 7.84%. Furthermore, the investigation showed the maximum decrease in the surge margin induced by the compressor fouling during the lower part-load operation by about 45.7% while in the higher loads created by the turbine fouling by about 14%.

Experimental Investigation of a Split Air Conditioning Using Condensate as Direct Evaporative Cooling

Split air conditioning systems produce reasonable amount of condensate which is usually not utilized and thrown away to the environment. On the other hand, it consumes a lot of energy during operation. The aim of this study is to investigate the improvement of air conditioning systems performance utilizing condensate. A direct evaporative cooling using condensate is incorporated on a 0.74 ton-cooling capacity of split air conditioning to decrease the air temperature before entering the condenser. Performances of the split air conditioning with and without direct evaporative cooling are compared and presented in this paper. The results show that the use of direct evaporative cooling using condensate into the air before passing through the condenser reduces the compressor discharge pressure. The decrease of the condenser pressure led to 4.7% and 7% reduction of power consumption for air conditioner without cooling load and air conditioner with 2000 W cooling load, respectively. The cooling effect and coefficient of performance (COP) increase with the decrease of compressor power. The use of direct evaporative cooling with condensate into the air before entering the condensing system can enhance the system performance and protect the environment.

Accurate noise modeling for petrochemical plants - impact of compressor Piping

Compressor piping is a dominant noise source in petrochemical plants with large centrifugal compressors. Acoustic insulation is used on compressor suction, discharge and recycle lines as a measure to mitigate noise radiating from compressor piping. This paper will demonstrate using case studies the importance of acoustic insulation on compressor piping as the primary and most cost effective noise control method for both community and in-plant noise. Case studies include the predicted and measured noise levels obtained during post startup noise surveys. This paper will also illustrate that to obtain good agreement with measured noise levels it is imperative to accurately model the piping sources following the actual piping layout and account for distance attenuation. A cost-benefit analysis of using complete compressor houses and/or acoustic blankets will be presented along with the efficacy of various types of acoustic insulation including elastomeric foam and aerogel based insulation systems. Different acoustic requirements for hot and cold insulation systems will also be presented.

Adiabatic compressed air energy storage technology

Adiabatic compressed air energy storage technology

Parameter study of Variation noise in outdoor of air conditioner

In the outdoor unit of a room air conditioner, the main factors that made it possible to vary the ability of cooling and heating are the development of BLDC motors, advances in inverter technology, and the development of refrigerant volume control technology. The main reason for this change in cooling and heating capacity is that it is possible to change the RPS of compressors. As the range of the compressor's RPS expands, so does the range of response to load variations. This is mainly based on the capacity of the high-pressure refrigerant produced by the compressor. When the compressor rotates at high speed or low speed, the difference in noise occurs depending on the difference in rotational speed. Of course, fans and motors also contribute to noise fluctuations, but the overall governing factor is the greater contribution of refrigerant from compressors and compressors. The refrigerant flows into the cycle configured in the outdoor unit and varies in speed and flow rate depending on the amount of refrigerant. This results in vibration and noise appearing in the form of radiations, resonances, solid sounds, resonances, and so on. There are several factors that can cause vibration or noise changes depending on the flow velocity and flow rate. In this paper, we selected reactance of compressor motors, mufflers directly connected to compressor discharge ports and accumulator at compressor inlet where fluid vibrations occur the most. First of all, reactance of motor responds quickly to load fluctuations and has a large instantaneous torque to instantaneous load fluctuations. The muffler, which is directly connected to the compressor discharge port, is the first Cavity where high-pressure gas meets, and can evaluate the concentration of kinetic energy that generates noise and improve the collection center to reduce fluctuating noise. The Accumulator is the part with the lowest temperature of refrigerant gas entering the compressor, and the rapid change in the flow path causes the most fluid to generate vibration and radiation of the structure. For this reason, we select three elements first. In this paper, we specifically describe the background of selecting three elements of an air conditioning outdoor unit for the variability of noise over RPS changes. We demonstrate that these factors can review the feasibility of the experiment, explain the results of the analysis, and possibility of reduce the variation noise.

Experimental evaluation of electric vehicle compressor lubricating oil robustness for heat pump application

Lubricating oil is the key to electric compressor performance, reliability, and durability in electric vehicle (EV) heat pumps. Previous investigations have revealed the lubricant's impact on fluid properties, component and system performance in vehicle climate control systems, but there have been few studies on heat pump application from the “robustness” perspective. In this study, we experimentally evaluated the robustness of two commercially available lubricants, polyalkylene glycol (PAG) and polyol ester (POE), for an electric scroll compressor in an electric vehicle heat pump by lubricant-refrigerant miscibility test, heat pump bench test and retrieved oil composition analysis. We showed that even if the PAG-R134a mixture kept miscible at low temperature, some insoluble substances would appear in the suction side accumulator below −10 °C, resulting in insufficient oil-return, increased compressor discharge temperature and superheat, and thus poor compressor lubrication. The mass spectrum analysis showed that the insoluble substances were reaction products of moisture and additives in the PAG oil. However, the POE oil used in this study did not show any insoluble substance under the same test condition. By comparison, the POE oil showed better robustness than the PAG. The experimental results indicate that the chemical composition of the lubricant should be carefully considered to ensure the robustness for compressor lubrication in EV heat pumps.

Energetic and exergetic performance comparison of an experimental automotive air conditioning system using refrigerants R1234yf and R134a

In this study, the energetic and exergetic performance merits of an automotive air condition-ing (AAC) system using R134a and R1234yf have been investigated. For this aim, a laboratory AAC system was developed and equipped with devices for mechanical measurements. The refrigeration circuit of the system mainly had an evaporator, condenser, liquid receiver, fixed capacity compressor, and thermostatic expansion valve. The tests were performed by changing the compressor speed and air stream temperatures incoming the condenser and evaporator. Based on energy and exergy analysis, various performance parameters of the AAC system for both refrigerants were determined and presented in comparative graphics. It was found that R1234yf resulted in 0.4–10.9% lower refrigeration capacity, 5.5–11.6% lower COP, and 4.7–16.1°C lower compressor discharge temperature, while yielding 9.3–22.3% higher refrig-erant mass flow rate and 1.1–3.5°C higher conditioned airstream temperature in comparison to R134a. Moreover, the components of the R1234yf system usually destructed more exergy, and the total exergy destruction rate per unit refrigeration capacity of the R1234yf system was 4.1–15.3% greater than that of the R134a one.