Refrigeration Unit Research Articles

Case study: Design of an absorption refrigeration system for milk preservation in Jalisco, Mexico

This article presents a case study focused on designing a refrigeration system for milk storage in a town of Jalisco, Mexico. An absorption refrigeration unit is proposed, activated with a geothermal heat source from an existing well. An economic analysis of the proposal and its comparison with a conventional system and a solar system is presented. The proposed system must provide refrigeration to the warehouse (cold room) with a cooling load of 5 kW, with a geothermal heat source temperature of 80 °C for the single effect system and 163 °C for the double effect system. For the design of the warehouse, the thermal loads were obtained through ceilings and walls, by lighting, infiltration, and by occupation, through the EnergyPlus software. The results show values of monthly thermal loads ranging between 0.94 and 1.1 kW. The single-effect system achieved a COP of 0.85 costing approximately $13,083, while the double-effect system reached a COP of 1.38 with a cost of $18,144.

Development of a new type of household appliances – refrigerators with a heating chamber

The object of this study is absorption-type refrigeration appliances, which allow to expand the functionality of household appliances without additional energy consumption.
 Investigated problem: The aim of this study: firstly, due to the novelty of the proposed technique, it was necessary to show the real possibility of obtaining the temperature level required for technological processes (up to 70 °C); secondly, taking into account the experience gained in experimental studies, it was necessary to propose new designs for solving the problems of refrigeration and heat treatment of food products and raw materials in domestic conditions.
 The main scientific results: It is shown that the development of devices that combine the functions of refrigeration storage and heat treatment of food products, semi-finished products and agricultural raw materials can become a promising area for energy saving in household appliances. In such household combined appliances, the heat released during the implementation of the refrigeration cycle is not immediately removed to the environment, but is transferred to a special heating chamber, while the temperature in the volume of the heating chamber is maintained higher than the air temperature in the room. The effect of energy saving is achieved by expanding the functionality of household appliances without attracting additional energy costs.
 The original designs of combined absorption-type household appliances are proposed, a description of their operation, advantages and disadvantages, and areas of application are given.
 The area of practical use of the research results: In the course of experimental studies, it was shown that the introduction of an additional heating chamber into the structure of household absorption refrigerators, thermally connected with the lifting section by the dephlegmator of the absorption refrigeration unit, does not lead to an increase in energy consumption (according to the test results below than in the standard version by 5 %) and does not impair the performance of the cooling chambers.
 The area of practical use of the research results: household energy-saving appliances.
 Innovative technological product: the use of an evaporation-condensation cycle that provides highly efficient heat transfer at a distance of up to 1 meter from the heat dissipation zone of the refrigeration unit to the usable volume of the heating chamber of the household appliance.

Entropy-statistical analysis of the efficiency of cycles of refrigeration units of household refrigerators

Objective. The aim of the work is to determine the thermodynamic efficiency of the modernized refrigeration unit of a household refrigerator compared to the basic model using the entropystatistical method.Method. В ходе работы при проведении исследований применен научный метод системного анализа, а также энтропийно-статистический метод термодинамического анализа при определении эффективности холодильного цикла бытового холодильника.Result. The analysis of the distribution of energy costs to compensate for the production of entropy by the nodes of the refrigeration unit is carried out. This analysis allows us to visually assess the energy losses in the cycle of a household refrigerator. The analysis was carried out for the most popular refrigerants R134a and R600a when used in household refrigerators. Based on the calculations carried out, comparative diagrams of energy losses in cycle processes are constructed. The entropy-statistical analysis of the thermodynamic efficiency indicators of the cycle confirms the advantages of the modernized refrigeration unit of the household refrigerator.statistical method.Conclusion. In the course of the work, it was confirmed that the use of an upgraded refrigeration unit will reduce the total energy costs, and the chosen research method will visually assess the energy losses for the elements of the refrigeration unit cycle.

Multi-Method Simulation and Multi-Objective Optimization for Energy-Flexibility-Potential Assessment of Food-Production Process Cooling

Process cooling for food production is an energy-intensive industry with complex interactions and restrictions that complicate the ability to utilize energy-flexibility due to unforeseen consequences in production. Therefore, methods for assessing the potential flexibility in individual facilities to enable the active participation of process-cooling facilities in the electricity system are essential, but not yet well discussed in the literature. Therefore, this paper introduces an assessment method based on multi-method simulation and multi-objective optimization for investigating energy flexibility in process cooling, with a case study of a Danish process-cooling facility for canned-meat food production. Multi-method simulation is used in this paper: multi-agent-based simulation to investigate individual entities within the process-cooling system and the system’s behavior; discrete-event simulation to explore the entire process-cooling flow; and system dynamics to capture the thermophysical properties of the refrigeration unit and states of the refrigerated environment. A simulation library is developed, and is able to represent a generic production-flow of the canned-food process cooling. A data-driven symbolic-regression approach determines the complex logic of individual agents. Using a binary tuple-matrix for refrigeration-schedule optimization, the refrigeration-cycle operation is determined, based on weather forecasts, electricity price, and electricity CO2 emissions without violating individual room-temperature limits. The simulation results of one-week’s production in October 2020 show that 32% of energy costs can be saved and 822 kg of CO2 emissions can be reduced. The results thereby show the energy-flexibility potential in the process-cooling facilities, with the benefit of overall production cost and CO2 emissions reduction; at the same time, the production quality and throughput are not influenced.

A novel solar operated DC compressor refrigerator with thermal energy storage

ABSTRACT In this work, the performance of HC600a and HFC134a refrigerant-based solar refrigerator with DC compressor was simulated and experimentally compared. Simulation of photovoltaic panel output was done with respect to three parameters: hourly average solar insolation, wind speed, and ambient temperature. This study includes the analysis of different seasons, involving both sunny and cloudy conditions for the compressor speeds of 2000, 2500, 3000 and 3500 rpm. The deviation encountered in this study is acceptable, and it is within 5% of the experimental values. HC600a system was seen having a maximum cooling energy of 3234 kJ with maximum system energy utilization efficiency of 14.3% at 3500 rpm in the summer season, while HFC134a showed 3198 kJ of maximum cooling energy with 14.1% of system energy utilization efficiency at 3000 rpm. The HC600a was seen producing maximum annual ice production of about 3175 kg, which was 8.5% higher than that of HFC134a. Finally, the DC compressor speeds for both the refrigerants were optimized for achieving maximum annual ice production. Overall, the solar-based refrigeration unit with HC600a was found to be the appropriate choice with thermal energy storage than that of the existing refrigeration unit with HFC134a for Chennai climatic conditions.

Analysis of the Energy Efficiency of the Air Conditioning System Based on Absorption Refrigeration Machine with Connection of Heat Pump and Solar Collectors

This article proposes and analyzes a circuit solution for providing heat supply to the generator of an absorption refrigeration machine (AHM) in centralized air conditioning systems using a heat pump unit (HPU) and solar collectors (SOL). Previously, such schemes have already been considered in the scientific works of Russian and foreign authors. The aim of the work is to propose new circuit solutions aimed at improving such systems, as well as confirming higher energy efficiency. This goal is achieved by solving the following problems: additional supply of the circuit with a common storage tank, operation of the absorption refrigeration machine generator and the condenser of the heat pump unit based on a common heat exchanger. Such a solution for the air conditioning complex based on an absorption refrigeration unit has been proposed for the first time. The most important results are the possibility of obtaining high values of the coefficient of performance, the possibility of achieving a number of technological advantages, increasing reliability and efficiency, as well as reducing the metal consumption of an absorption-type plant operating from solar collectors and a heat pump plant compared to similar systems. The significance of the obtained results lies in the fact that the use of a common storage tank and a combined heat exchanger (AHM generator / HPU heater) provides a significant increase in the coefficient of performance, a decrease in the metal consumption (reduction in costs) of the main equipment.

Carbon emissions from refrigeration used in the UK food industry

The food and beverage industry is the largest manufacturing sector in the UK. Food cold chains are energy intensive and use high global warming refrigerants. The aim of this work was to benchmark the existing UK cold chain and provide robust evidence-based data on greenhouse gas (GHG) emissions in 2019. Only emissions from refrigeration within UK borders was considered. Both Scope 1 emissions from refrigerant leakage (fugitive) and diesel for the transport refrigeration units (TRUs) as well as Scope 2 emissions from electrical power usage were estimated. These were estimated to be 12.9 MtCO2e per annum which represents 3.5% of the total UK annual territorial GHG emissions. Eighty-three percent of the Scope 1 emissions were fugitive, and 56% of these were from retail refrigeration. Agriculture and fisheries were the sectors with the lowest fugitive emissions accounting for only 3.7% of the total. Scope 2 emissions accounted for 54% of the emissions and tended to increase towards the consumer end of the cold chain, with 1.5% in agriculture and fisheries and 38% in domestic refrigeration. The FAOSTAT value of GWP used for f-gas emissions is not representative of UK emissions. UK government statistics may be underestimating domestic refrigerator emissions as they are not using real life energy consumption.

Real-Time Anomaly Detection in Cold Chain Transportation Using IoT Technology

There are approximately 88 million tonnes of food waste generated annually in the EU alone. Food spoilage during distribution accounts for some of this waste. To minimise this spoilage, it is of utmost importance to maintain the cold chain during the transportation of perishable foods such as meats, fruits, and vegetables. However, these products are often unfortunately wasted in large quantities when unpredictable failures occur in the refrigeration units of transport vehicles. This work proposes a real-time IoT anomaly detection system to detect equipment failures and provide decision support options to warehouse staff and delivery drivers, thus reducing potential food wastage. We developed a bespoke Internet of Things (IoT) solution for real-time product monitoring and alerting during cold chain transportation, which is based on the Digital Matter Eagle cellular data logger and two temperature probes. A visual dashboard was developed to allow logistics staff to perform monitoring, and business-defined temperature thresholds were used to develop a text and email decision support system, notifying relevant staff members if anomalies were detected. The IoT anomaly detection system was deployed with Musgrave Marketplace, Ireland’s largest grocery distributor, in three of their delivery vans operating in the greater Belfast area. Results show that the LTE-M cellular IoT system is power efficient and avoids sending false alerts due to the novel alerting system which was developed based on trip detection.

Thermodynamic and economic analysis of a supermarket transcritical CO2 refrigeration system coupled with solar-fed supercritical CO2 Brayton and organic Rankine cycles

Aiming to reduce the use of conventional energy sources, alternative methods should be applied in order to cover society’s needs. In this context, in the present study, the operation of a transcritical CO2 commercial refrigeration unit is investigated, coupled with two power production cycles. The first cycle is a supercritical CO2 Brayton system that is supplied with heat by a solar field including parabolic trough collectors, while the second one is an organic Rankine cycle, utilizing as a heat source the low enthalpy CO2 exiting the first cycle. The novelty of this system is attributed to the combination an advanced transcritical CO2 refrigeration system with power production cycles that operate under the optimal conditions, as well as to the reason that the operation of the refrigeration unit is independent from the solar energy, since it can provide refrigeration output regardless of the solar heat input. The results prove that the increased number of solar collectors leads to more advantageous power production results, although with higher capital costs. Furthermore, greater energy production is noted when the ambient temperature is lower and abundant solar power is available. For the case of installing five solar collectors and an organic Rankine cycle, it is found that the annual energy production of the total system is 173.72 MWh, while the annual energy consumption of the refrigeration unit is 466.66 MWh, meaning that 37.23 % of energy savings are achieved annually. For the same configuration, according to the life cycle cost analysis, the capital cost is found equal to 243.72 k€, leading to a payback period of 7.6 years. By the end of the project’s lifetime, the operation of the installed system returns 298.42 k€ to the investor.

Thermodynamic analysis of two evaporator vapor compression refrigeration system with low GWP refrigerants in automobiles

Due to the growing demand for refrigerators and air conditioners in automobiles, there is a need for an innovative and efficient design to achieve both refrigeration and air conditioning. To address this, the present work has evaluated a two-evaporator vapor compression system to eliminate the requirement for separate refrigeration and air conditioning units. Theoretical energy and exergy performance assessment of the same is carried out along with the variation in the condenser and evaporators temperature. Various low GWP refrigerants such as R1234yf, HFO1336mzz(Z), R513A, and R450A are compared against high GWP R134a and R452A. The results reveal that maximum exergy efficiency and COP and lowest compressor power of 31.50%, 2.47, and 6.304 kW, respectively, are obtained with HFO1336mzz(Z). After HFO1336mzz(Z), R134a shows the highest exergy efficiency and COP of 30.56% and 2.41, respectively, and the lowest compressor power of 5.61kW. HFO1336mzz(Z) exhibits the optimum performance, whereas R452A shows the worst thermodynamic performance in the system. It is also found that the performance of R450, R513A, R450A, and R1234yf is approximately equivalent to each other. Moreover, component-wise exergy destruction analyses indicate that the efficiency of the compressor needs to be improved as the maximum destruction of 61.84–56.00% occurs in the compressor while the minimum exergy destruction of 0.42–0.54% occurs in the expansion valve. This study proposes the two-evaporator system for both refrigeration and air conditioning in automobiles. It is also found that R450A, R1234yf, R513A, and HFO1336mzz(Z) can be the potential alternative to R134a.

Thermodynamic and Economic Evaluation of a Novel Green Methanol Poly-Generation System

Methanol is considered a sustainable alternative energy source due to its ease of storage and high-octane rating. However, the conventional methanol production process is accompanied by resource consumption and significant greenhouse gas emissions. The electrochemical reaction of electrochemically reacted hydrogen (H2) with captured carbon dioxide (CO2) offers an alternative route to methanol production. This paper presents a new green poly-generation system consisting of a parabolic trough solar collector (PTC) unit, an organic Rankine cycle (ORC) unit, a CO2 capture unit, an alkaline electrolysis unit, a green methanol synthesis and distillation unit, and a double-effect lithium bromide absorption refrigeration (ARC) unit. The system mainly produced 147.4 kmol/h of methanol at 99.9% purity, 283,500 kmol/h of domestic hot water, and a cooling load of 1341 kW. A total 361.34 MW of thermal energy was supplied to the ORC by the PTC. The alkaline electrolysis unit generated 464.2 kmol/h of H2 and 230.6 kmol/h of oxygen (O2) while providing H2 for methanol synthesis. Thermodynamic and economic analysis of the system was carried out. The energy and exergy efficiency of the whole system could reach 76% and 22.8%, respectively. The internal rate of return (IRR) for the system without subsidies was 11.394%. The analysis for the methanol price showed that the system was economically viable when the methanol price exceedsed$363.34/ton. This new proposed poly-generation system offers more options for efficiently green methanol production.

DEVELOPMENT AND IMPLEMENTATION OF AN AUTOMATIC SOLAR/AC POWER SUPPLY UNIT FOR A REFRIGERATOR

This work focuses on a solar and AC power supply unit for a refrigerator. The two sources of power supply, an alternating current power supply and solar power supply, each connected to an automatic changeover used to switch power supply to the refrigerator unit. The alternating current power supply and solar power supply both charge the battery interchangeably through the inverter depending on the power source in use. The inverter unit consists of a battery used to store the solar energy needed to keep a constant supply of refrigeration to the refrigerator unit even when there is no alternating current power supply; a transformer which is used to step up the voltage supplied by the battery to match the voltage needed by the refrigerator unit to work properly and also an oscillator which is used to convert the direct current voltage supplied by the battery into alternating current voltage. This aims at maintaining constant operation of the refrigerator unit.

Design and Development of Performance Rating Apparatus for Cold Room Refrigeration Unit Using Cooling-Load Balance Method

Refrigeration systems are composed of many components working together, and their refrigerating capacity depends upon these components constituting the refrigeration system. The design of the refrigeration system does not only consider cooling loads from products but also the operating conditions that change from time to time, especially the ambient temperatures due to global warming and climate change. Therefore, this work aims to develop the apparatus for performance rating of the cold room’s refrigeration unit according to the ASHRAE standard test methods as well as the Eurovent certification programs. The principle of enthalpy change is used to determine the system performance, in general. In this work, the cooling-load balanced method is proposed, which shows a good refrigeration capacity estimation by balancing the cooling load with refrigeration capacity. In addition, the use of an ultrasonic flow meter for refrigerant flow rate measurement is also discussed for additional validation in future works.

Test Bed Emulation of Secondary Loop Refrigeration Units Using Peltier Elements: An Impedance Control Approach

Advanced control methods help to increase the efficiency of refrigerated applications, easing their economic and ecological burden. However, approaches from literature have rarely been validated experimentally. One significant reason is the high expenses when conducting control experiments on full-sized plants. Low-maintenance, low-cost testing facilities constitute a possible remedy. Therefore, this work proposes a test bed refrigeration unit based on Peltier elements, for which impedance control compensates the behavioral differences to an actual secondary loop refrigeration unit. The two-degree-of-freedom control architecture comprises a static feedforward and a PID path that is robustified by choosing a linear design model based on the v-gap metric. Experimental validation using a 260 min cycle shows that the achieved system trajectory lies within sensor accuracy to the desired one for more than 99% of the time, proving adequate emulation. Thus, the proposed concept is suitable to experimentally investigate high-level temperature control algorithms for refrigerated applications.

Modeling of working processes in low-speed reciprocating compressors of compact refrigeration units.

Modeling of working processes in low-speed reciprocating compressors of compact refrigeration units.

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.

Auto Regressive eXogenous (ARX) System Identification of Batch Milk Cooling Process

The dynamic model of the milk cooling process from 36°C to 4°C using chilled water available at 2°C has been carried out. The cooling water temperature is kept constant by using a refrigeration unit. The process being studied was a Packo brand milk cooling tank belonging to KUD SAE Pujon (Malang - Indonesia). A fundamental heat balance method was used to derive the model, leading to a first-order transfer function process. For a 2 hours cooling process then, the gain and time constant values are 1.00 and 42.3548 mins respectively, or G(s)=1/(42.3548s+1) (first order process). Deriving system transfer function through a mechanistic model is considered difficult; therefore, in this paper, we explored process identification via Auto Regressive eXogenous (ARX). Transient simulations could then be performed to identify the dynamic behavior of the cooling process. The system was then identified using several orders of the Auto Regressive eXogenous (ARX) model, and then the results were re-tested on different forms of perturbations and obtained quite accurate results. The transfer function identified through the ARX111 is G(s)=1/(42.3729s+1) (first order process), while via ARX441, the 5th order process was obtained: G(s)=(0.02361s^4+0.000371s^3+0.2331s^2+9.27×10^(-7) s+0.0005826)/(s^5+0.03932s^4+9.873s^3+0.2331s^2+0.02468s+0.0005826). These models particularly useful for process control design and analysis.

‘Getting along’ or ‘getting ahead’? How urban-to-rural newcomers employed at Danfoss in south Denmark build bridging, bonding and linking social capital

The ability to attract skilful workers to a rural area is of fundamental importance for achieving local economic growth (e.g., Aure et al., 2018). However, firms in rural areas often experience difficulties with both recruiting workers and integrating them, to ensure that they will stay long-term (e.g., Gieling et al., 2017). The specific role of a major firm in a rural area for attracting and integrating newcomers is however understudied. This is unfortunate, as such firms appear crucial for local demographic and economic growth. We contribute to fill this gap by exploring how newcomers employed at the Northern Als headquarter of Danfoss – a company with 40,000 employees worldwide that produces thermostatic and refrigeration units – are integrated in various local, family/friendship and firm-related social networks. Based on 10 semi-structured interviews, observations and 35 informal conversations, we investigate how these Danfoss newcomers build bridging, bonding and linking types of social capital (Putnam, 2000). We found two newcomer ideal types. The Bridging Newcomer was most successfully integrated in local communities. The Bonding Newcomer either participated in firm-related networks or sought company with family and close friends outside Northern Als.

Energy, exergy, energy-saving, economic and environmental analysis of a micro-gas turbine-PV/T combined cooling, heating and power (CCHP) system under different operation strategies: Transient simulation

A micro-gas turbine (MGT) combined cooling, heating and power system coupled with low concentrating photovoltaic/thermal-heat hump (LCPV/T-HP) and absorption chiller is proposed in this study. LCPV/T is used as the heat source of HP to realize mutual promotion. The performance of CCHP system under different operation strategies is dynamically simulated and analyzed by TRNSYS software from energy, exergy, energy-saving, economy and environment. The results demonstrate that both high temperature water source heat pump (HWHP) and low temperature water source heat pump (LWHP) achieved better COP in following electric load (FEL) mode. The average COP of HWHP and LWHP are 22.69% and 4.75% higher than the rated COP, respectively. Annual total cost per unit building area (ATCUBA) and carbon dioxide emissions per unit building area (CDEUBA) are also more advantageous in FEL mode, while primary energy consumption per unit building area (PECUBA), ATCUBA and CDEUBA seems less preferable in following thermal load (FTL) mode. The exergy efficiency and energy efficiency of the system in FEL mode are 19.96% and 41.90% in summer, and 25.13% and 59.36% in winter. Additionally, the equipment with higher exergy loss is mainly LCPV/T, gas-fired boiler, absorption refrigeration unit, MGT and hot water generator under the three operation strategies.

THERMAL ENERGY CONSUMPTION DURING MILK PROCESSING IN A COMMERCIAL DAIRY PLANT: A CASE STUDY

Energy is important component of dairy industry. Dairy industry processing mainly based on heat transfer that’s required thermal energy. Thermal energy conservation in dairy plant means to develop a methodology to achieve energy saving to reduce energy costs in processing system. The aim of this study was to investigate consumption of thermal energy of market milk and dairy product per tone of product. The data was analyzed of a commercial dairy plant in January to march 2021.In dairy processing plant, steam was utilized in milk pasteurization, cream pasteurization, butter processing, ghee making, dahi making, butter milk thermization were found as 16.70, 26.60, 47.22, 540.0, 72.50 & 59.90 kg per 1000 kg product, respectively and corresponding thermal energy were45.1, 71.8, 127.9, 1458.0, 195.8 and 161.7 MJ per 1000 kg product processing. The average steam consumption of crate washing was reported as 84.3 kg steam per 1000 crate. The average refrigeration load requirement of dairy plant was found 172.9 TR and corresponding running cost of refrigeration unit was found Rs. 14.25 per TR per hour. The data of this case study was compared with previous study in interpretation of those results.