Design Of Refrigeration System Research Articles

Mathematical model of an air-filled alpha stirling refrigerator

This work develops a mathematical model for an alpha Stirling refrigerator with air as the working fluid and will be useful in optimizing the mechanical design of these machines. Two pistons cyclically compress and expand air while moving sinusoidally in separate chambers connected by a regenerator, thus creating a temperature difference across the system. A complete non-linear mathematical model of the machine, including air thermodynamics, and heat transfer from the walls, as well as heat transfer and fluid resistance in the regenerator, is developed. Non-dimensional groups are derived, and the mathematical model is numerically solved. The heat transfer and work are found for both chambers, and the coefficient of performance of each chamber is calculated. Important design parameters are varied and their effect on refrigerator performance determined. This sensitivity analysis, which shows what the significant parameters are, is a useful tool for the design of practical Stirling refrigeration systems.

Design and performance characteristics of solar adsorption refrigeration system using parabolic trough collector: Experimental and statistical optimization technique

The current work demonstrates a developed model of a solar adsorption refrigeration system with specific requirements and specifications. The recent scheme can be employed as a refrigerator and cooler unit suitable for remote areas. The unit runs through a parabolic trough solar collector (PTC) and uses olive waste as adsorbent with methanol as adsorbate. Cooling production, COP (coefficient of performance, and COPa (cycle gross coefficient of performance) were used to assess the system performance. The system’s design optimum parameters in this study were arrived to through statistical and experimental methods. The lowest temperature attained in the refrigerated space was 4°C and the equivalent ambient temperature was 27°C. The temperature started to decrease steadily at 20:30 – when the actual cooling started – until it reached 4°C at 01:30 in the next day when it rose again. The highest COPa obtained was 0.75.

A dimensionless numerical analysis for the optimization of an active magnetic regenerative refrigerant cycle

Refrigeration by an active magnetic regenerative system (AMR) is potentially more attractive, as compared to conventional techniques. Indeed, devices based upon an AMR cycle are more efficient, compact, environment-friendly and can operate over a broad range of temperatures. In this paper, attention is focused to the near room-temperature range. On the other hand, however, the AMR cycle poses a variety of complex problems, in terms of fluid dynamics, heat transfer and magnetic field. In order to identify the optimal operational parameters, the design and optimization of a magnetic refrigeration system can be supported by modelling. In this paper, a dimensionless approach was adopted to simulate an AMR cycle following a Brayton regenerative cycle. In the simulation, the temperature range that has been explored is 260 – 280 K and 275 – 295 K. The heat transfer mediums are, respectively, water–glycol mixture (50% by weight) and pure water. The Gd0.8Dy0.2 alloy and pure Gd have been chosen as constituent material for the regenerator of the AMR cycle. With this model, the influence of the different parameters on cycle efficiency has been analysed. In particular, the study has been focused on the influence of the secondary fluid properties, magnetic material particle diameter, fluid blow time, secondary fluid mass flow rate, regenerator geometry and effect of axial thermal conduction. The model enables to find optimal dimensionless numbers in order to maximize the cycle performances. The results can be extended to widely different situations and therefore can be easily employed for the design and the optimization of new experimental prototypes. Copyright © 2012 John Wiley & Sons, Ltd.

Hygienic Design and Microbial Control of Refrigeration and Air Conditioning Systems for Food Processing and Packaging Plants

The critical control points of the refrigeration and air conditioning systems serving the food processing and packaging plants are analyzed from the hygienic viewpoint. They identified the problems of hygienic design of the various components of refrigeration systems and air conditioning installations, and several solutions are described. The lack of hygienic design of air conditioning and refrigeration systems, and their inadequate cleaning and disinfection procedures, can cause significant economic losses and epidemic diseases in people, employees, or visitors, or in the final food consumers. So, the present manuscript analyses: (1) the microbial control in refrigeration systems, including the control of Legionella, and the limitations of using biocides embedded in plastic materials (for cooling tower filling and air ducts in air conditioning systems); (2) the hygienic design of evaporative coolers (evaporative condensers and cooling towers) as a new way for controlling Legionella contamination; and (3) the microbial contamination and hygienic design of air conditioning systems for food processing and packaging rooms, including the microbial control in the air by means of UV lamps, essential oil aerosolization, and filtration. The interest of the clean rooms and microbiologically controlled environments for food processing and packaging is explained through a case study of slicing and packaging of ready-to-eat meat products.

A State-of-the-Art Review of Compact Vapor Compression Refrigeration Systems and Their Applications

We present a critical review of the literature on the fundamentals, design, and application aspects of compact and miniature mechanical vapor compression refrigeration systems. Examples of such systems are those envisaged for electronics and personal cooling. In comparison to other refrigeration technologies (e.g., solid-state), vapor compression enables the attainment of low evaporating temperatures while maintaining a large cooling capacity per unit power input to the system. Over the past decade, there have been a significant number of studies devoted to the miniaturization of system components, with the most critical being the compressor. When compared with competing cooling technologies, such as flow boiling in microchannels, jet impingement, and spray cooling, refrigeration is the only one capable of lowering the junction temperature to values below the ambient temperature. The combination of vapor compression refrigeration with the aforementioned technologies is also possible, necessary, and beneficial, since it increases greatly the potential for reducing the system size. For each main application, this paper sheds some light on the thermodynamic and thermal aspects of the cooling cycle and on recent developments regarding its components (compressor, heat exchangers, and expansion device). Whenever appropriate, issues and challenges associated with the different cycle designs are addressed. An overview of the ongoing efforts in competing technologies is also presented.

ANALISA TEKNIS DAN EKONOMIS PERENCANAAN SISTEM PENDINGIN RUANG PALKAH IKAN DENGAN SISTEM KOMPRESI UAP MENGGUNAKAN REFRIGERAN R22(MONOKLORO DIFLURO METANA)

The fish refrigeration process purposes to resist the bacterium cause fresh fish be rotten. Generally the fishermen using ice to refrigerate the fish. This method has weak like the ice easy to melt so the fresh fish quality be bad and least simple in operation .One of alternative can use to keep the fresh fish quality is using the refrigerant system. Refrigerant is main component of the refrigeration system.In this system scheme is refrigerant weared is Refrigerant Monokloro difluro methane ( R-22).). this refrigerant is not flammable and nontoxic.( sumanto,1985) The temperature of the fish holds KM Trevally design that using the refrigeration system is -5°C According to the analysis of refrigeration system design for condensing temperature at 30°C and evaporating temperature at -10 ° C, the result showed that the value of coefficient of performance is about 9.9 The refrigeration system using R22 gives the fish hold capacity twice bigger than icing method. Refrigerant's fish hold system purpose 22 need investment cost as big as Rp 196.729.600,00 and Total overall cost if utilizes system refrigerasi's fish hold as big as Rp 236.198.012,00. Of analisis's result by use of method Net Present Value (NPV) with interest rate 15 % pertahun investments by borrows capitals at Bank for investment acquisition Ratch Coolant System Fishes Out by use of tech refrigerasi can be said reasonable with Break Event Point of investment will be reached on time 2.1 year .

Influence of Nusselt number on weight loss during chilling process

The coupling of the heat and mass transfer occurs on foods during chilling process. The temperature of foods is reduced while weight changes with time. Chilling time and weight loss involve the operating cost and are affected by the design of refrigeration system. The aim of this work was to determine the correlations of Nu-Re-Pr and Sh-Re-Sc used to predict chilling time and weight loss, respectively for infinite cylindrical shape of food products. The correlations were obtained by estimating coefficients of heat and mass transfer based on analytical solution method and regression analysis of related dimensionless numbers. The experiments were carried out at different air velocities (0.75 to 4.3 m/s) and air temperatures (-10 to 3°C) on different sizes of infinite cylindrical plasters (3.8 and 5.5cm in diameters). The correlations were validated through experiments by measuring chilling time and weight loss of Vietnamese sausages compared with predicted values.

Optimal design and operation of a C3MR refrigeration system for natural gas liquefaction

LNG liquefaction is an energy-intensive process. Energy efficiency is the major concern in LNG liquefaction process design and operation. In this paper, a new methodology for LNG liquefaction synthesis targeting energy consumption minimization is presented. It is based on thermodynamic analysis, mathematical programming, and rigorous simulation. The procedure for MINLP (mixed-integer non-linear programming) model development and simplification is described in detail. LINDOGlobal solver in GAMS is employed to solve the MINLP problem and the optimization results are further validated through rigorous simulations. Based on the development, the optimal design and operational conditions for LNG liquefaction process can be simultaneously achieved. A C3MR LNG liquefaction process is employed to demonstrate the efficacy of the developed methodology. Comprehensive thermodynamic analysis is also conducted to give insights of the optimization results.

Design of an ejector cycle refrigeration system

A design procedure, based on a one-dimensional simulation, is presented for an ejection refrigeration system. Heat exchangers are included in the calculation, accounting for temperature differences between the fluids and for pressure losses. The ideal gas assumption, which is quite common in the literature concerning ejector systems, is avoided. Furthermore, the supersonic diffuser is designed with a continuous profile, without cylindrical piece, controlling the variation of momentum along the flow path and accounting for friction. At design conditions, this should reduce the irreversibility due to the normal shock. A comparison between different operating fluids is presented and R245fa is selected. The results of the design procedure and the expected performance, in terms of first and second law efficiency, are presented.

Design, Construction and Testing of a Solar Adsorption Refrigerator Using Synthesised Zeolite A and Water as Adsorbent/Adsorbate Pair

This paper presents the design and construction of a simple Zeolite-water solar adsorption refrigeration system which has been fabricated and tested in the Department of Mechanical Engineering, Ahmadu Bello University, Zaria, Nigeria at a geographical location of latitude 11o11’’NE. The theory on which this design is based is on the use of Zeolite-water adsorbent/ adsorbate pair to produce refrigeration. The energy source is a parabolic trough solar concentrator that collects and radiates solar thermal energy onto an air tight black coated absorber (generator) charged with Zeolite and water placed at the trough’s focal point. The absorber adsorbs and desorbs the adsorbate and produces refrigeration as vapor is released through a condenser and an evaporator. Constructional details of the system show the systems height at 1.2 m, parabolic trough dimensions of 0.6m by 0.45m, the cold chamber, has a capacity of 36 liters. The system was evaluated by leaving it outside under solar radiation and monitoring temperatures at various points inside the collector, the generator, and the evaporator through the use of thermocouple sensors. The highest and lowest temperatures of the absorber were 60.1°C and 25°C respectively. The lowest refrigeration temperature of 9.8°C was attained with 179J of cooling.

Design and Performance Study of a Novel Refrigeration System

In order to solve the problems of pressure drop and leakage in the refrigerant circuit, a novel continuous adsorption system suited to use low heat source (75-85 oC) was designed and set up. To analyze and compare with the conventional system to reveal the similarity and difference, this paper sets up the mathematical models for these two systems. The adsorbers, condensers and evaporators in these two systems are exactly the same and the two systems are compared by working at the identical conditions, which is not feasible in real experimental lab. All the parameters and models used in this calculation are based on experimental results. Analysis demonstrates that the two kinds of system have very close performances, that is, the novel system has a relatively higher cooling capacity while the conventional system has a relatively higher COP.

Improvement of solar-electric compression refrigeration system through ejector-assisted vapour compression chiller for space conditioning in subtropical climate

In this study, improvement was made for the solar-electric compression refrigeration system by incorporating the ejector design to a conventional vapour compression chiller within the system. Through year-round dynamic simulation, the performances of the ejector-assisted vapour compression chiller (EAVCC) were evaluated under the intermittent and changing supply of solar energy in the subtropical climate. In addition, the effect of three common refrigerants, R22, R134a and R410A on the EAVCC was assessed and compared. It was found that the coefficient of performance of the chiller was increased and the total primary energy consumption of the system was decreased for all the three refrigerants, in which the degree of enhancement from R134a was the most significant. It was also noted that the effect of R410A on EAVCC was not apparent, and the overall system energy improvement was marginal. With appropriate ejector design and refrigerant selection of the solar-electric compression refrigeration system, the reduction potential of year-round primary energy consumption could be more than 5%. This would be certainly helpful in promoting the application of solar air-conditioning for building use in the subtropical climate.

A Design of a Commercial Ice Pond Refrigeration System for Long-term Potato Storage

A Design of a Commercial Ice Pond Refrigeration System for Long-term Potato Storage

Validation of a vapour compression refrigeration system design model

This paper presents the validation of a design model for vapour compression refrigeration systems developed by Akintunde (2004a). This model was used to design a vapour compression refrigeration system. The experimental set-up is made up of: a compressorreciprocating type, 0.746 kW capacity, using R134a as working fluid, with cylinder stoke volume of 32.7 cm; evaporator and condenser, bare coil tube-in-tube serpentine copper coil. The cycle performance was evaluated through the following parameters; Cooling load (Qe); Condensing load (Qc); Coefficient of performance (COP) and mass flow rate. The R values (calculating using excel) of the COPs under subcooling and superheating with the degree of subcooling and superheating conditions were 80.7% and 88% respectively. While the correlations between the COPs under the same conditions were 88% and 99.9%. The present analysis showed that the model results are comparable to the actual system from both quantitative and qualitative points of view. Under the same operational conditions, maximum absolute deviations of the variable parameters – mass flow rate, COP and circulating water temperature, are within the range of 16%.

An experimental study on heat transfer of CO 2 solid–gas two phase flow with dry ice sublimation

Knowledge on heat transfer characteristics of CO 2 solid–gas two phase flow is important to design of some new refrigeration systems. Continuously obtaining CO 2 solid–gas fluid flow in a closed loop is necessary to measure its heat transfer. In this paper, an experiment set-up is designed, constructed and tested in order to measure the temperatures, pressures of the CO 2 solid–gas two phase flow, and also further its heat transfer characteristics. As the first step of the investigation, the measurement work is conducted in a horizontal circular tube. Based on the obtained results, it is verified the present experiment set-up can continuously obtain CO 2 solid–gas fluid flow in the closed loop and also heat transfer measurement is possible. The results show an average value 310 W/(m 2 K) of heat convective coefficient is experimentally obtained in the present range, which is higher than that of gas flow. The Nusselt number is found to increase along the tube length in the sublimation area. In addition, some knowledge on the heat transfer characteristic of the CO 2 solid–gas flow is learned from the present study.

VAPOR–LIQUID EQUILIBRIUM MODELING FOR MIXTURES OF HFC-32 + ISOBUTANE AND HFC-32 + HFO-1234ze(E)

Vapor–liquid equilibrium (VLE) have been successfully modeled for the binary mixtures of difluoromethane (HFC-32) + isobutane and difluoromethane + trans-1,3,3,3-tetrafluoropropene (HFO-1234ze(E)). These mixtures are considered as possible replacements for conventional refrigerants far from negligible global warming potential (GWP). A multifluid approach explicit in the Helmholtz free energy forms the basis of the model. The independent variables are the temperature, density, and composition. Accurate published equations of state for pure HFC-32, isobutane, and HFO-1234ze(E) are incorporated to calculate the Helmholtz free energy of each component. Typical uncertainties of bubble- and dew-point pressures calculated using the model are within 2%. Although adjustable parameters of the model are determined only from experimental VLE data, it is highly probable that the model reasonably predicts other thermodynamic properties such as enthalpy and heat capacities. Therefore, the model allows practical design and simulation of refrigeration systems using the mixtures as a working fluid.

Optimum design of ejector refrigeration systems with environmentally benign fluids

A design methodology for simple ejector refrigeration systems of fixed cooling capacity operating with fixed temperatures of the external fluids entering the generator, the condenser and the evaporator is presented and applied for a particular combination of these four parameters. The results establish the existence of optimum values for the refrigerant pressure in the generator ( P G ) and the temperature difference in the heat exchangers (Δ T) which minimize the total thermal conductance of the system. These optimum values of P G and Δ T are particularly interesting since they yield high values for the coefficient of performance and the exergetic efficiency of the system. They have been determined for four refrigerants (R134a, R152a, R290, and R600a). An objective function, which to a first approximation is proportional to the product of the capital and operational costs, is defined and used to compare the performance of the system with these refrigerants.

Multiscale modelling of postharvest storage of fruit and vegetables in a plant factory context

AbstractAfter harvest, fruit and vegetables produced in plant factories need to be stored under refrigerated conditions. There has been an interest in the use of mathematical models for optimising the operation, design and control of postharvest refrigeration systems. These mathematical models are applied to predict the physical and chemical phenomena that take place during postharvest handling of horticultural products. Nowadays, with the availability of more powerful computers at a reasonable price, it is feasible to investigate the details of the flow behaviour in large-scale refrigeration systems at a very small spatial and temporal scale. In this presentation an overview will be given of advances in the application of mathematical models for predicting and optimising fluid flow, heat and mass transfer and associated phenomena during postharvest refrigeration of horticultural products. Special attention will be paid to the multiscale formalism to describe heat and mass transfer phenomena over a wide range of spatial scales.

Design and Comparative analysis of Adsorption Refrigeration System for Refrigerants R-134a and R-410a

Design and Comparative analysis of Adsorption Refrigeration System for Refrigerants R-134a and R-410a

Performance evaluation and optimal design of supermarket refrigeration systems with supermarket model “SuperSim”, Part I: Model description and validation

Conventional supermarket refrigeration systems are responsible for considerable CO 2 emissions due to high energy consumption and large quantities of refrigerant leakage. In the effort to conserve energy and reduce environmental impacts, an efficient design tool for the analysis, evaluation and comparison of the performance of alternative system designs and controls is required. This paper provides a description of the modelling procedure employed in the supermarket simulation model ‘SuperSim’ for the simulation of the performance of centralised vapour compression refrigeration systems and their interaction with the building envelope and HVAC systems. The model which has been validated against data from a supermarket has been used for the comparison of R404A and CO 2 refrigeration systems and the optimisation of the performance of transcritical CO 2 systems. These results are presented in Part II of the paper.