1,259 Works

Performance comparison of very low GWP R404A alternatives in a commercial freezer application

S. SPLETZER, J. MEDINA & N. ROBERTS
International efforts to reduce the global warming impact of refrigerants are advancing, as evidenced by the Kigali Agreement and European F-Gas regulations. R-404A is widely used for medium and low temperature refrigeration applications. Given the GWP of this HFC blend (GWP100 Year = 3,922 per AR4), lower GWP alternatives are required. For smaller self-contained equipment, several new very low GWP HFC-HFO blends are now under consideration, such as XL40 (R-454A), XL20 (R-454C), and R-455A. While...

Multi-temperature transport refrigerator with an eutectic refrigerating system.

L. VAITKUS & V. DAGILIS
An eutectic refrigerator uses a phase-change material to store energy and produce a cooling effect. Such system offers multiple advantages and in some cases is an optimal choice. Traditionally, these refrigerators are built as single compartment refrigerators, in which the inside air temperature depends on the crystallization temperature of the phase-change material. A multi-temperature refrigerator with both fresh and frozen food compartments would offer new opportunities for the user. However, a traditional approach used in...

Operation parameters of a walk-in cooler after retrofiting R404A with R448A.

T. LOKIETEK & P. WISNIK
Results of measurements of running parameters in a refrigeration system, for R-404A-R-448A retrofit scenario, are presented and compared. Analyses includes energy and power consumption comparison of the reciprocating compressor in a one-evaporator compression refrigeration system running at selected temperature and superheating settings. Test is conducted in order to resemble live system retrofit conditions and adjustmenst rather than laboratory one. Paper shows that conducting R-448A retrofit, results in energy efficiency as a benefit for end user.

Assessment of refrigerant selection for ejection system driven by low-grade heat.

K. SMIERCIEW, A. KEDZIERSKI M., D. BUTRYMOWICZ & Et Al.
Selection of the working fluid for the refrigeration and solar air-conditioning systems is the crucial problem because of the strong influence of the thermodynamic properties on the system efficiency. Moreover, the working fluids should fulfil the environmental criteria such as zero ODP (Ozone Depletion Potential) and as low GWP (Greenhouse Warming Potential) as possible. Therefore the natural fluids or new synthetic fluids are thought as the best option. The paper deals with theoretical analysis of...

Numerical modelling of heat and mass transfer processes in chinese cabbage cold storage chamber.

M. KOLODZIEJCZYK, D. BUTRYMOWICZ, K. SMIERCIEW & J. GAGAN
This paper is devoted to numerical modelling of heat and mass transfer phenomena in the cold storage chambers of vegetables. The main objective of the paper is to work out the model of the cold storage chamber that takes into account heat transfer, transpiration and respiration processes for the exemplary case of Chinese cabbage storage. The thermal non-equilibrium model of heat transfer in porous media was applied both to the bed of vegetables and to...

Low GWP refrigerants era has started – Compressor manufacturer experience.

M. ZGLICZYNSKI
Embraco for many years is present as a one of the more active companies in promoting hermetic compressors for use with natural refrigerants worldwide. Apart of isobutane in household type of appliances, propane is becoming the main option in light commercial plug-in systems as R404A and R134a natural alternative. Recent F-Gas EU regulation as well as similar legislation in other parts of the planet, in order to mitigate climate change, are considering ban of high...

Geometrical aspects of novel internally geared screw machine.

M. READ, N. STOSIC & I. SMITH
Cylindrical helical gearing can be used in a positive displacement machine where an externally lobed inner gear rotates inside an internally lobed outer gear while maintaining continuous lines of contact between the gears. This creates a series of separate working chambers between the rotors. In this type of machine the rotors have parallel axes of rotation, and both rotors can be free to rotate about their own axes. Fixed end plates are proposed as a...

Evaluation of the discharge pressure pulsation in reciprocating compressor using computer simulation tools and experimental validation.

J. SEDLIAK, I. BENDIK & M. ČAJA
Discharge muffler is an important part of the reciprocating compressor which affects acoustic performance of the refrigeration system. Pulsation energy transferred from the discharge system of the compressor to the refrigerator can excite mechanical structures of the appliance. Optimization of the design in terms of acoustic performance, thermodynamic properties and cost is always a challenge for engineers. Discharge muffler of reciprocating compressors shall work well with different refrigerants. Availability of numerical acoustic simulation programs helps...

HFCs phase-down: new international and national challenges.

D. COULOMB
The Kigali amendment was adopted in October 2016. Even if there was a final consensus to phase down HFCs, some international decisions still need to be made in 2017 and 2018, and national plans regarding refrigerants must be reviewed and implemented.

Thermodynamic analysis of performance of liquid injector for ejection refrigeration system.

A. PAWLUCZUK, D. BUTRYMOWICZ, K. SMIERCIEW & Et Al.
Paper deals with thermodynamic analysis of operation of the system with two-phase vapour-liquid injector as a liquid pump in ejection refrigeration systems. The analysis cover the following fluids: isobutane R600a, butane R600, propane R290, R245fa, R134a, R1234yf, and R1234ze(E). The simple balance model of the injector as well as obtained results were presented and discussed in the paper.

A simple theoretical study of a new multi-chamber rotary compressor with different refrigerants.

D. LIM Y., A. SARIP, Q. ANG C. & Et Al.
A new multi-chamber rotary compressor (MCRC) is introduced in this paper. This new compressor is designed to achieve better compactness and energy efficiency. The design and working principle of the new compressor will be presented in this paper. A mathematical model is developed and the theoretical performances of R-134a, R32 and R1234yf are investigated and presented in this paper. Various key parameters including the Coefficient of Performance (COP) of each refrigerant is calculated and analyzed.

Heat transfer in small air compressor.

J. TUHOVCAK, J. HEJCIK & M. JICHA
Heat transfer inside the reciprocating compressor influences the efficiency. Gas superheating in the suction line is responsible for about half of the thermodynamics losses and decreases mass flow through the compressor. Inside the cylinder, the heat transfer increases the amount of work necessary for compression process. Therefore, analyzing the heat transfer between the compressor components brings better overview on temperature distribution and consequently may show the possibilities of improvement. This paper presents a thermal analysis...

Design of vapour ejector for refrigeration system based on CFD simulation.

K. SMIERCIEW, D. BUTRYMOWICZ, J. GAGAN & Et Al.
Renewable energy sources may be applied to drive refrigeration and air-conditioning systems, e.g. solar radiation, geothermal resources, heat derived from biomass combustion or waste heat rejected form various thermal processes. In this case absorption systems or ejection refrigeration systems may be used for cooling applications. The paper deals with numerical simulation applied for design of the ejector. Designed ejector is dedicated to the low-temperature driven ejection refrigeration system operating for district cooling system. Temperature and...

Thermo-economic approach to optimize air conditioning systems.

N. ZHYKHAREVA & M. KHMELNIUK
The mathematical model of the air conditioning system is based on the analysis of thermoeconomic indications of energy efficiency, which can be solved in complex: the determination of optimal parameters; determining the optimal device and optimization of operating modes of the refrigeration system. The model takes into account that the energy of the refrigeration unit may be transmitted in the form of heat and mechanical work under optimum conditions of the compressor. On the basis...

Modelling of droplets evaporation in ejector heat exchanger.

V. KOGUT, V. BUSHMANOV, I. BUTOVSKYI & Et Al.
In process of industry development load of an environment grows. The problem of creation of effective methods of purification of flue gases acquires the increasing relevance. The scheme of the refrigerator with the ejector heat exchanger is provided. The solution of this question is proposed in use of the refrigeration unit with the heat exchanger ejector. Cooling of a gas flow is carried out due to injection of finely divided drops in the dispersed gas...

Numerical investigation of working fluid influence on stirling refrigeration machine performance.

M. KHMELNIUK, V. TRANDAFILOV V., O. OSTAPENKO & Et Al.
This paper presents the main results of mathematical modeling operating cycle rotary-vane gas refrigerating machine that affect installation, machine control and working processes occurring in it at the specified criteria. A procedure and a graphical method for the rotary-vane gas refrigerating machine (RVGRM) are proposed. A parametric study of the main geometric variables and temperature variables on the thermal behavior of the system is analyzed. The model considers polytrope index for the compression and expansion...

High efficient integrated CO2 refrigeration systems with ejectors and pivoting compressor arrangements.

A. HAFNER
Equipment manufacturers of refrigeration units are facing challenges related to the legislative requirements forcing them to implement less conventional refrigerants with lower Global Warming Potential (GWP). The newly introduced next generation of hydrofluorocarbons (HFCs) with ultra-low GWPs do have a very short (atmospheric) lifetime, however, the decomposing products are highly toxic in combination with water, short life HFCs and their blends do not represent a safe and sustainable alternative. CO2, a natural working fluid applied...

Application of single blow technique for heat transfer measurement in packed bed of carrot.

A. LAPIŃSKI, D. BUTRYMOWICZ, J. GAGAN & Et Al.
The non-invasive measurement of the mean heat transfer coefficient for the packed bed of fruits and vegetables may be thought as still open issue. There is a clear need for the assessment of heat transfer conditions for various types of fruits and vegetables in order to accurately predict the thermal load that is necessary to select refrigeration equipment for cold storage chamber. Additionally, there is significant development in numerical modelling of heat and mass transfer...

Evaluation of the discharge pressure pulsation in reciprocating compressor using computer simulation tools and experimental validation.

J. SEDLIAK, T. BENDIK N. & M. ČAJA
Discharge muffler is an important part of the reciprocating compressor which affects acoustic performance of the refrigeration system. Pulsation energy transferred from the discharge system of the compressor to the refrigerator can excite mechanical structures of the appliance. Optimization of the design in terms of acoustic performance, thermodynamic properties and cost is always a challenge for engineers. Discharge muffler of reciprocating compressors shall work well with different refrigerants. Availability of numerical acoustic simulation programs helps...

On-line discharge capacity detection for linear compressor.

H. ZOU, C. LI, M. TANG & Et Al.
In this paper, an on-line discharge capacity detection method for linear compressor is presented so that the capacity regulation control system of linear compressor can adjust its output upon the real working conditions. A mechatronic parameter, the vertical component of motional electromotive force, is applied as the character for discharge capacity detection. According to the variation tendency of this parameter, the pumping point and the top dead center (TDC) of the piston can be detected...

Measurement of the permeability of suction filter in reciprocating compressor.

R. RUMAN, J. ŠUSTEK & P. TOMLEIN
The paper deals with permeability measurement of suction filter sample used in semi-hermetic reciprocating compressor. The main goal of the work was to verify the assumption that the suction filter made from thin stainless-steel grid can be considered as a porous medium and if it is possible to apply 1-D porous media model based on Darcy’s law and Forchheimer equation in CFD simulation for this application. For this purpose there were carried out experimental measurements...

Energetic efficiency of cooling circuit depending on the charge of the previous and new alternative refrigerant.

J. ŠUSTEK & P. TOMLEIN
Energetic efficiency of cooling circuit influences the amount of refrigerant, which is changing when refrigerants with high GWP are substituted by refrigerants with low GWP. Substitution of R404A for R449A or R448A was carried on experimental cooling box with own cooling circuit and original refrigerant R404A with air cooled condenser. Heating load was selected adequately to cooling output of evaporator, which was possible to regulate by speed of ventilators. Cooling circuit was tested by ClimaCheck....

Numerical modelling of finned heat exchanger.

K. SMIERCIEW, M. KOLODZIEJCZYK, J. GAGAN & Et Al.
The fin-and-tube heat exchanger has been extensively used in refrigeration, heat pump, and air-conditioning engineering. Modelling approach for finned air coolers in application to the refrigerated storage was presented. The air cooler unit is usually taken into account in modelling of the cold storage chambers with very simplified geometry and physics. Results of numerical modelling using the computational fluid dynamics (CFD) software ANSYS FLUENT of fin-and-tube air cooler with porous media conditions is presented in...

Influence of ejectors on the selection of compressors in carbon dioxide booster systems.

O. JAVERSCHEK, M. REICHLE & J. KARBINER
In carbon dioxide booster systems ejectors can now take over a part of the job previously done only by compressors, creating certain pressure lifts. This gives extra options for designing energy efficient refrigeration systems. The influence on the operating conditions of the compressors in the system is shown in examples, by varying load conditions in a warm climate. The chosen system includes medium and low temperature load in a supermarket installation. The impact of the...

Pressure pulsations passive damping in compressors manifolds: experimental and numerical approach development

P. MŁYNARCZYK
Pressure pulsations in volumetric compressor manifolds have a high impact on compression power requirement and the reliability of manifold operation. These pulsations induce vibrations, noise, and in some cases, mechanical failure of piping or compressor valves. For pressure pulsation attenuation, different types of mufflers are applied using a design based upon the Helmholtz resonator approach. This design is particularly effective for constant revolution speed compressors. For contemporary applications of variable revolution speed compressors, other pressure...

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