Refrigeration Machine Research Articles

Влияние механической деформации на магнитные свойства и магнитокалорический эффект в пленках Gd

In W/Gd/W/MgO heterostructures, the dependence of mechanical stresses in the Gd film on the crystallographic orientation of the MgO substrate was revealed. Variations in the interplanar spacings in MgO in different orientations create tensile elastic stresses up to 0.22 GPa in the Gd film, which are transferred through the damping layer W. It is found that these stresses affect the isothermal magnetization curves, the corresponding change in the magnetic part of the entropy at the Curie point Tc = 293 K, and the relative cooling capacity (RCP). This allows us to consider mechanical stresses as a factor in controlling the magnetocaloric cycle, which increases the efficiency of the refrigeration machine, when mechanical loading is synchronized with the heating-cooling cycles of the ferromagnet.

Оценка степени влияния фактора подвижности стенок щели при расчёте величины протечек в рабочей части спирального компрессора. Часть 1

The scroll type compressor is widely used in the medium capacity segment of refrigeration and air conditioning technology including heat pumps. Today there is an active process of changing from hydrofluorocarbons to natural refrigerants with low global warming potential. CO2, with its low critical point and correspondingly high operating pressures, is gaining in importance. For operation with new refrigerants, the scroll compressor has to be adapted to take account of all its design features, the most important of which are the clearances in the machine's flow area. It has to be considered that the thermodynamic properties of carbon dioxide, different from hydrofluorocarbons, have a significant influence on the volume and energy values of the compressor. In this case relevance consists in increase of accuracy of compressor losses calculation and prediction of refrigeration machine characteristics. As the basic volumetric losses in the scroll compressor are leakages of working substance in its working part, and the process of flow of medium is unsteady, their quantitative component causes interest. The purpose of this work is to clarify the physical basis of the leakage process in the radial clearance and the degree of influence of various factors on it. Such analysis gives further opportunity to refine the methodology of calculation of leakages of compressed medium, taking into account the mobility factor of gap walls. It will raise accuracy of the received results which can serve as a base to prognosis of optimum characteristics of the compressor, due to their approximation and will allow to optimize designing of refrigerating machines at the chosen modes of work.

Experimental investigation and exergetic modelling of R718/LiBr bubble pump operated absorption refrigeration machine

Experimental investigation and exergetic modelling of R718/LiBr bubble pump operated absorption refrigeration machine

Influence of mechanical deformation on magnetic properties and magnetocaloric effect in Gd films

In W/Gd/W/MgO heterostructures, the dependence of mechanical stresses in the Gd film on the crystallographic orientation of the MgO substrate was revealed. Variations in the interplanar spacings in MgO in different orientations create tensile elastic stresses up to 0.22 GPa in the Gd film, which are transferred through the damping layer W. It is found that these stresses affect the isothermal magnetization curves, the corresponding change in the magnetic part of the entropy at the Curie point T_c=293 K, and the relative cooling capacity (RCP). This allows us to consider mechanical stresses as a factor in controlling the magnetocaloric cycle, which increases the efficiency of the refrigeration machine, when mechanical loading is synchronized with the heating-cooling cycles of the ferromagnet. Keywords: magnetocaloric effect, entropy, microdeformations, microstresses.

Improving the Environmental Efficiency of Engineering Systems Operating under the Scheme of Secondary Use of Thermal Energy

Refrigerating machines are used in many areas to produce artificial cold. In the course of its operation, each refrigeration unit generates a lot of heat by compressing the refrigerant, which is not used in any way in the future, and during condensation is released into the environment in the form of water vapor. The use of chlorine-containing refrigerants destroys the ozone layer. To reduce environmental damage, a water reuse system was created and a technology for using low-temperature heat that is released during the operation of the refrigeration machine was developed. This paper offers various design solutions aimed at the comprehensive modernization of the cooling system of the ice palace "Puck" in Sochi to reduce its impact on the environment. In the course of the research, a refrigeration unit was developed allowing utilization, accumulation, and channeling of condensation heat for the secondary use of thermal energy by other engineering systems at the facility, thereby reducing emissions of harmful substances into the Earth's atmosphere and increasing the technological capabilities of cooling. Methods that allow making the necessary calculations and selecting equipment for the implementation of the developed systems on ice arenas are also proposed.

Optimization of compressor work, power and heat on efficiency refrigerant r290 on split ac

The vapor compression cycle refrigeration machine is the type of refrigeration machine that is most widely used today, generally the medium used as a working fluid that transfers heat from the product being cooled to its environment is a synthetic refrigerant. The working fluid is called refrigerant. Refrigerant is the main working fluid used in air conditioning systems to absorb heat and convert it in the refrigeration system. This then encourages countries in the world including Indonesia to then jointly carry out prevention and improvement by making agreements. Then this agreement was known as the Vienna Convention in 1985 followed by the Montreal agreement in 1987. In order to reduce the impact of ODS (Ozone Depleting Substances), in 1992 Indonesia signed the Montreal protocol. At that time, Indonesia also launched the "Indonesian Country for the phase Out of Ozone Depleting Substances (ODS) under the Montreal Protocol". This study aims to compare the work of compression, heat absorbed, and the electric power used by the split type refrigeration machine between refrigerant R-22 and refrigerant R-290. These results and analysis show that R-290 has a higher value than R-22 in compression performance. R22 power consumption is 0.30 kw and R290 is 0.26. R290 this is influenced by the light work of the compressor so that it will have an impact on electric power consumption. The power consumption of R290 is 42% less than R22. The heat absorbed by R 22 is smaller than that using hydrocarbons. The results of the optimization of compressor work, power and heat variables show an effect on efficiency.

Analisis Perbandingan Kinerja Refrigeran R134a dan MC-22 pada AC Split

AC (Air Conditioner) is one of the cooling machines, whose use is currently increasing. One important component that helps cooling the AC (Air Conditioner) is the refrigerant. Refrigerant is a kind of material or substance in the form of liquid and gas which is usually flowed in the refrigeration machine installation. The purpose of this study was to determine the performance (COP), electrical energy consumption, and cooling rate from the use of refrigerants R134a and MC-22. The independent variables in this research are refrigerant R134a and refrigerant MC-22. The dependent variable in this study is COP (Coefficient of Performance), electrical energy consumption, and cooling rate. The control variable in this study was using time variations. The research material is refrigerant R134a and MC-22 The results of this study showed that R134a refrigerant has a better COP value than MC-22 refrigerant, where the COP value at 60 minutes for R134a refrigerant is 8.6 while for MC-22 refrigerant is 8.0. At 60 minutes the use of refrigerant R134a, the electrical energy used is 385.00 W.h. Meanwhile, 60 minutes of the use of refrigerant MC-22, the electrical energy used is 455.40 W.h.

REFRIGERATION MACHINES IN THE SYSTEM OF CONSISTENT MANAGEMENT OF ELECTRIC ENERGY CONSUMPTION OF THE COMPLEX ENTERPRISE-INDUSTRIAL REFRIGERATOR

The strategy of the coordinated management of electric consumption of the industrial refrigerator of the enterprise of a food complex on production of foodstuff is offered. The structure of the integrated intelligent power management system of the refrigerator enterprise has been developed, in which the systems of automated control of electricity metering and control of the refrigeration trajectory of refrigeration chambers are built-in. The system uses a situation center, industrial Internet of Things (IIoT), digital platform “FOOD” with software (freezing of food products). According to the ASUE-ACS command, the upper level of the industrial refrigerator and its software fulfill the set parameters of the portfolio of orders for active and reactive capacities of the food complex enterprises. An algorithm for controlling an industrial refrigerator during periods of power system power limitations has been developed. It is proved that the reduction of specific energy consumption for the production of one ton of frozen food during the period of power system power limitations and fan outages is possible only by optimizing the technological and energy parameters of refrigeration machines. Technologies for reducing energy consumption by controlling the reactive and active power of synchronous motors of reciprocating compressors and frequency control of asynchronous motors of screw compressors and asynchronous motors of evaporating condensers are presented. Simulation of the geometry of the in-chamber loading of the refrigerating chambers of an industrial refrigerator is performed. New approaches to the choice of adaptive regulators of synchronous motor exciters have been developed, which are coordinated in real time with the energy modes of operation of refrigeration machines and the geometry of refrigeration chamber loading. The possibility of improving the efficiency of power management regimes of food industry enterprises through coordinated automated control of cooling and freezing of meat products, poultry, fish, dairy products, fruits and the use of automated power management systems by building expert and human-machine decision making systems. The developed systems will allow to meet the requirements of energy generating companies for active and reactive loads, reduce costs in the power grid and maintain the voltage in the nodes of electrical receivers within the established norms.

The new textbook Automation of Refrigeration Units

The new textbook Automation of Refrigeration Units, published by Intermedia (St. Petersburg) in April 2022, presents the program contents of the special subject Automation of Refrigeration Units developed to train students based on the federal state educational standard of higher education. The textbook contains lecture course content from the Department of Refrigeration Machines of the Astrakhan State Technical University and its branch, the Dmitrov Fishing-Industry Technological Institute.
 Zhiltsov IB, Novikov IV. Automation of refrigeration units: a textbook. St. Petersburg: Information Center Intermedia, 2022. 258 p. ISBN 978-5-4383-0240-7

Mass flow prediction in a refrigeration machine using artificial neural networks

Measuring mass flow rate in refrigeration systems with flow meters can be expensive when taking into account the cost of the equipment itself and the costs related to installation and maintenance. A mode based on Artificial Neural Networks can be used to predict the value of the mass flow, at a low cost, through easily observed and measured parameters, like temperatures. Additionally, well-known correlations to calculate parameters that directly influence the mass flow rate can be used as input data for the model to improve its accuracy. Within this context, the present study aims to develop a Multilayer Perceptrons model to predict the mass flow rate of a refrigeration systems. The model developed was optimized using one hidden layer with four neurons, Adam as the optimizer and softplus as the activation function. Later, it is presented an alternative mass flow rate meter, using an Artificial Neural Network model programmed in a microcontrolled circuit with only three temperatures as inputs. To develop the model, experimental data were collected in a refrigeration machine at several operating points. Step disturbances were introduced in the mass flow rate to produce transient data. Two different data sets were considered in the training process. The first data set contained only steady-state data and in the second data set, there were steady-state plus transient data. The mass flow rate estimated through the proposed model presented an average error of 0.79 % when considering steady-state and transient data in the training process, and 0.81 % when considering only steady-state data in the training procedure. The final embedded system developed predicted the mass flow rate with an average error of 1.22 %.

Evaluation of the effects of entrainment ratios on the performance parameters of a refrigeration machine having dual evaporator ejector system with R134a and R456A

In this study, a dual evaporator ejector system (DEES) was experimentally investigated in order to determine the effective cooling capacities depending on entrainment ratios (ER). An experimental performance analysis was conducted on the system to assess the range of entrainment ratio in which both evaporators can operate effectively. To this end, superheating temperatures, compressor isentropic efficiencies, compression ratios, pressures at the ejector outlet, cooling capacities, and throttling ratios (for TXV#1) were analysed in association with entrainment ratio values to determine the upper and lower limits for effective operating conditions. The results show that the compressor isentropic efficiency drops with the increase of entrainment ratio. Isentropic efficiency was calculated as 0.69 and 0.71 for R134a and R456A, respectively, when the entrainment ratio was above 0.8. Special attention was paid to the superheating temperatures of the second evaporator of the system. When the entrainment ratio was higher than 0.8, the superheating temperatures was found to be 35 °C for R134a and 30 °C for R456A. Because an expansion device was utilized before the evaporator#2, very low evaporation pressures were obtained in the evaporator#2; but this caused an excessive increase in the superheating temperatures. It can be asserted that both evaporators can be operated at the desired cooling capacities, when the entrainment ratio is between 0.4 and 0.8. Finally, although the cooling performance of R134a was 10% higher than that of R456A, the coefficient of performance (COP) of R456A was higher than R134a.

The Analysis of the Use of Intercooler on a Multi Stage Cold Storage Simulator Toward the Compressor Work

Multistage type cold storage is a refrigeration machine required in an industry because it functions to store food products for a long time. Bali, as a world tourist destination, will rely heavily on this cooling system in preparing services for tourists, especially in the food and beverage sector. Multistage type cold storage is designed to reach the evaporator temperature below -30oC thus the used compressor performance must be able to produce maximum refrigeration effect. Two compressors placed in succession or connected in series complete this cold storage system, which is expected to achieve higher operating pressures. The temperature occurring due to the pressure increase on the second compressor will be anticipated by installing an intercooler aiming at preventing excessive heat or over heat during the compression. The extent to which the important role of the intercooler as a stabilizer of operating temperature in this cooling cycle will be shown in its working cycle with a Mollier diagram (P-h diagram). The data obtained during the operation of the multistage type cold storage is then transferred to the P-h diagram of R134A to determine the cycle diagram and the enthalpy which then determines the amount of COP, the maximum temperature achieved by the system, and its energy requirements. The calculation results obtained using the intercooler COP is 1.83, and the maximum temperature achieved is 67oC, and the energy consumption seen from the total entalphy difference due to compression work is 81 kJ/kg. Without using the intercooler, the system’s COP is 1.72 and the maximum temperature achieved is 94.9oC and 86 kJ/kg of energy consumption. The energy required for the operational becomes more eficient and the heat released to the environment is much less, therefore the multistage cold storage with intercooler can be categorized as an eco-friendly technology.

EN Thermodynamic analysis of a real marine refrigeration system for cruise ship "Scarlet Lady"

This paper presents an energy analysis of the marine refrigeration system as a component of the machi­nery system of the cruise liner “Scalet Lady”. This type of ship is one of the most complex types from an energy point of view, which is associated with a wide variety of energy consumers. The study uses two methods of thermodynamic analysis of real cycles: the method of cycles and entropy-statistical method. For the analysis, the experimental data on the operating modes of the marine refrigeration system has been used. According to the results of processing the experimental data, a thermodynamic cycle has been formed and an energy calculation of the cycle has been performed using classical methods for two-stage refrigeration machines. With the help of the cycle model, the external irreversibility is determined by successively reducing the energy efficiency of the ideal cycle. The Lorentz cycle has been chosen as an ideal model, taking into account the variable temperatures of heat supply and removal during heat exchange “heat source – phase transformations of the refrigerant R407f”. Along with the evaluation of efficiency, the distribution of losses by the components of the refrigeration system has been established, energy weaknesses that require improvement has been identified, and the most effective ways to reduce energy costs have been outlined. Analytical conclusions have a graphical interpretation of the thermodynamic efficiency assessment for the real refrigeration cycle. It has been established that in the considered real cycle of a marine refrige­ration system, the greatest influence on energy efficiency is exerted by external irreversibility in the condenser, in particular, in the overheating zone (25.64% of the total energy consumption of the plant). The effect of irreversibility in the compressor is not fixed

Analisa kerja alat uji prestasi mesin pendingin udara dengan kapasitas daya kompresor 1 PK

The purpose of the study was to determine the temperature value at each point of the refrigeration performance tool, heat absorption, refrigerant flow rate, compressor power, and the working speed of the refrigeration performance test tool or (Coefficient Of Performance) COP during the 60 minute test time. The method that will be used in this research is to modify the test equipment and conduct real experiments by analyzing several variables that affect the performance of the air conditioning system. The independent variables in this study were the refrigerant pressure of 60 Psi, 70 Psi, and 80 Psi. The addition of several components of measuring instruments that function to display data will be carried out at each point as needed. Digital reading of data will function to display test result data in the form of numbers for air temperature, temperature, and refrigerant pressure in the air conditioning machine (AC). The study was conducted in a room with a size of 4 x 5 x 2.5 meters, and using LG AC with a compressor power of 1 PK. Based on the test results, changes in temperature that occur at each point of the performance of the air conditioning machine and heat absorption affect the temperature changes of each cooling machine performance, namely the use of 60 Psi of 23.9 C for 70 Psi of 24.8 C and 80 Psi is 22.1 C. Then changes to heat absorption by the condenser and evaporator are at a refrigerant pressure of 60 Psi of 171.6 kJ/s for 70 Psi of 201.1 kJ/s and 80 Psi of 215.3 kJ/s. And the heat absorption that occurs in the evaporator with a pressure of 60 Psi is 143.3 kJ/s for 70 Psi of 161.6 kJ/s and 80 Psi is 172.2 kJ/s. The resulting refrigerant flow rate and compressor power, for the refrigerant flow rate, affect the changes that occur in the use of 60 Psi of 0.003 kg/s, for 70 Psi of 0.004 kg/s, and 80 Psi of 0.005 kg/s. Then for the compressor power at the use of 60 Psi of 0.446 kW, for 70 Psi of 0.521 kW, and 80 Psi of 0.611 kW. The refrigerant flow rate value of the refrigeration machine performance test tool or COP produced at a refrigerant pressure of 60 Psi is 3.26 for 70 Psi, namely 4.45 and 80 Psi is 5.11.

Particularities of R134a Refrigerant Temperature Variations in a Transient Convective Regime during Vaporization in Rectangular Microchannels.

An analysis of the R134a (tetrafluoroetane) coolant’s non-stationary behavior in rectangular microchannels was conducted with the help of a newly proposed miniature refrigerating machine of our own design and construction. The experimental device incorporated, on the same plate, a condenser, a lamination tube and a vaporizer, all of which integrated rectangular microchannels. The size of the rectangular microchannels was determined by laser profilometry. R-134a coolant vapors were pressurized using a small ASPEN rotary compressor. Using the variable soft spheres (VSS) model, the mean free path, Knudsen and Reynolds numbers, as well as the dimensionless velocity profile can be assessed analytically. In order to determine the average dimensionless temperature drop in the vaporizer’s rectangular microchannels, in non-stationary regime, an analytical solution for incompressible flow with slip at the walls, fully developed flow and laminar regime was used, by aid of an integral transform approach. In the experimental study, the transitional distribution of temperature was tracked while modifying the R134a flow through the rectangular microchannels. Coolant flow was then maintained at a constant, while the amount of heat absorbed by the vaporizer was varied using multiple electric resistors. A comparative analysis of the analytical and experimental values was conducted.

Research Summary and Literature Review on Modelling and Simulation of Heat Pumps for Simultaneous Heating and Cooling for Buildings

A heat pump for simultaneous heating and cooling (HPS) is a refrigeration machine by which the productions of heating and cooling energies are simultaneously valorized. This introductory article presents the uses of heat pump productions under the form of an analysis of thermal demands of different types of buildings and a literature review of real installations and experimental systems, which are the basis of the construction of numerical models. The applications of HPSs are diverse: space heating and cooling, domestic hot water (DHW), hot water for desalination process, etc. Means and methods for improving the performance of refrigeration cycles and the management of heat and cold productions are developed, including modeling and simulation. New refrigeration circuit architectures were designed. A focus is paid on refrigerants. Prototypes combining heating-cooling, heating-cooling-DHW and cooling-desalination have been developed, built and tested to validate the models. Even though a strong simultaneity of thermal demands is essential, the results show that HPSs are generally very efficient systems.

THEORETICAL FOUNDATIONS FOR ASSESSING THE RELIABILITY OF REFRIGERATION MACHINE EQUIPMENT ON THE BASIS OF THE NEURO-FUZZY METHOD FOR IDENTIFYING THEIR STATE

In order to design modern smart enterprises such as industrial refrigerators with a high level of reliability of their operation while maintaining the proper quality of cooling, freezing and storage of various types of products, the article analyzes the current level of safety and time to failure of equipment for refrigeration equipment for refrigeration of industrial refrigerators and system analysis of the technical system of equipment of refrigeration machines to determine the requirements for the system for assessing the level of safety of equipment of enterprises – industrial refrigerators. A methodology has been developed for analyzing the state of the equipment of refrigeration machines of industrial refrigerators, as an object of malfunctions. Models of possible malfunctions are constructed with the identification of relationships between technological parameters of operability, reliability and emergency situations. A situational model of the state of the refrigeration machine as a source of malfunctions has been developed, which is distinguished by the ability to identify relationships between parameters, events – the causes of emergencies and the state of refrigeration supply of refrigeration chambers. Knowledge about fuzzy situations is structured and fuzzy reliability models are constructed that characterize the state of the equipment. The practical value of the study lies in the development of a methodology for assessing the reliability and durability of refrigeration equipment based on a neuron-fuzzy identification method, creating a knowledge base and a system for managing the refrigeration plant performance process. Thus, it is possible to manage systems for predicting and monitoring emergency situations in systems for operational monitoring of technological processes for freezing the results of eating.

Cooling capacity of experimental system with natural refrigerant circulation and condenser radiative cooling

The surface of the Earth is a source of radiation of thermal energy, which, passing through the atmosphere, is partially absorbed while the bulk of the energy is released into the surrounding outer space. A cooling technique based on this physical phenomenon is known as radiative cooling (RC). It is possible to reduce the consumption of electricity for cooling, as well as to reduce capital costs, by integrating the unit with radiative cooling directly into the circulation circuit of the refrigerant of the refrigeration machine. An experimental refrigeration system has been designed, in which in the cold periods of the year the removal of heat from the cooled object is carried out due to the mode of natural circulation of the refrigerant from the evaporator to the heat exchanger, cooled by radiative cooling. A refrigeration system with natural circulation and radiative cooling of the refrigerant R134a was experimentally studied during the autumn period in Almaty. The experimental study established that the chamber is cooled with the help of the examined system while the temperature in the cooled volume is maintained by 5...7 K above ambient air temperature at night. The dependence of the air temperature in the refrigerating chamber on the temperature of the atmospheric air has been determined. A procedure for assessing the cooling capacity of the system has been devised. The study reported here demonstrated the possibility of using radiative cooling to remove heat under the mode of natural circulation of the refrigerant. The refrigeration system reduces energy consumption in the cold seasons by diverting heat to the environment without the compressor operating

Desain Cold Storage untuk Pembekuan Ikan Laut Menggunakan Perangkat Lunak Coolselector®2

The process of cooling and freezing carried out on fish products is one of the preservation methods that apply a cooling machine in its operation. The refrigeration machine used applies a steam compression refrigeration system with R404A refrigerant as its working fluid. A design that is not following the standards can result in significant losses both in material and economic terms. Besides, the wrong model can also cause the performance of the engine to cool down. The purpose of this study is to design and analyze the performance of cold storage for freezing fish using Coolselector®2 software version 3.6.1. Performance analysis is based on superheating and subcooling temperature variations to determine its effect on the performance of the cooling engine. Changes for superheat temperatures carried out at the 8K, 9K, 10K, 11K and 12K levels while the subcooling temperature is considered constant at the 3K level. Variations were made at subcooling temperatures at the 3K, 4K, 5K, 6K and 7K levels with superheat temperatures considered consistent at the 5K level. The result of cold storage room design shows that the room has a cooling capacity of 14.54 kW. Analysis of the performance of the engine coolant design shows that the refrigeration machine has excellent performance. It will be proved by the higher subcooling and superheat temperatures, the COP also increase. The most top COP is at the 12K superheat temperature level of 2.045, while for the subcooling temperature at the 7K level of 3.144

ANALISA KOEFISIEN UJUK KERJA MESIN PENDINGIN (CHILLER) UNIT 1 PADA POWER HOUSE

Each refrigerant has different characteristic properties which affect the refrigeration effect and the resulting coefficient of performance (COP). A refrigeration machine that works by cooling water is called a refrigeration machine chillers. Chiller is an air conditioner with no cooling system direct. In this indirect cooling system, the refrigeration engine does not instantly cools the air in every room. Refrigeration machine cools water demin first, then this cold demin water is used for cool the air in the room. Cold demin water as cooling medium to reduce the temperature of a wide room at power house (PH) PLTA Musi. The method used in working on this practical work report is:by making observations or observations in the field, conducting interviews (interview) with supervisors and practical work supervisors regarding theoretical data (specification data). In this study, the Cooling Performance Coefficient (COP) was analyzed On Power House (PH) PT PLN (PERSERO) UL PLTA Musi The results of this study get the conclusion, namely: The coefficient of performance (COP) on the machine chiller unit 1 in Power House PLTA Musi by 4.22 is smaller than specification coefficient. This indicates that the cooling system is working properly optimal.