Design Of Refrigeration System Research Articles

Progress in design of adsorption refrigeration systems. Evaporators

Adsorption heat pumps are becoming increasingly popular. Due to their design, they enable application of low-temperature heat sources. Evaporators for adsorption chillers make one of the basic design elements determining the correct operation of these devices. The specificity of operation in low pressures and temperatures is the reason why their design significantly differs from that of conventional evaporators. The pluralities of existing solutions as well as the lack of a systematic review of them cause difficulties in correct evaluation and choice of design. The paper presents the current state of art as well as a review of the existing solutions of evaporators used in adsorption heat pumps. The purpose of the review research is to present various solutions of evaporators as well as indicating their advantages and disadvantages in order facilitate the choice of the optimal design.

Mathematical Simulation of the Thermodynamic Processes Associated with the Vapour-Injected Scroll Compressor

Both the major energetic crisis and the global warming, which influence the worldwide economy and the future of the society, determine the development of energetic and ecological performances of both the refrigeration equipment and air conditioning systems. Thus, there is a worldwide supported effort made in order to decrease the carbon dioxide emissions resulted from the burning of fossil fuels and the other greenhouse effect gas emissions. This article presents a refrigeration system design model using a vapour injection scroll compressor and tube in tube evaporators working with refrigerant R407C. The refrigerant circuit comprises of a main evaporator, a secondary evaporator (for the injection process), scroll compressor, condenser and five expansion valves. Furthermore it uses R407C as refrigerant. The secondary refrigerant for both the main and the secondary evaporator is a 50% concentration solution of propylene-glycol and water. Secondary circuit comprises of a pump, an electric boiler, an expansion vessel and a by-pass circuit made of many stop valves. The condenser is cooled with mains water.

A comparative study of CO2 refrigeration systems

Abstract The refrigeration systems with CO2 seem to be attractive choices for the design of refrigeration systems with small environmental impact. The objective of this work is the comparison of different transcritical CO2 refrigeration systems and the determination of the most promising configurations. A typical system (evaporator, compressor, gas cooler, expansion valve) is the reference system and it is compared with a system with internal heat exchanger, a parallel compression system, a two-stage compression system and a system with mechanical subcooling after the gas collector. The examined systems produce refrigeration at one temperature level and they are examined for various operation scenarios. More specifically, the refrigeration temperature is examined from −35 °C to +5 °C, while the condenser temperature (or the gas cooler outlet temperature) from 35 °C to 50 °C. The analysis is conducted with developed models in Engineering Equation Solver (EES). According to the results, all the examined systems are more efficient than the reference system for all the examined scenarios. The system with the mechanical subcooling and the two-stage compression system are found to be the most efficient choices with a mean coefficient of performance enhancement at 75.8% and 49.8% respectively.

Exergy characteristics of R404A indirect refrigeration system using CO2 as a secondary refrigerant

In this paper, R404 refrigeration system is evaluated to understand the exergy characteristics of an indirect refrigeration system for R404A that adopted CO2 as a secondary refrigerant. This provides basic data for the optimal design of indirect refrigeration system for the R404A. The results are summarized as follows. It was confirmed that the system’s exergy loss increased as the R404A condensation temperature, the CO2 cooler temperature difference, and the CO2 mass flow rate increased under a fixed experimental condition. However, the system’s exergy loss decreased as the CO2 evaporation temperature increased. It was also found that the exergy loss of the R404A refrigeration system was higher than that of the CO2 secondary refrigerant system. It was also confirmed that total exergy loss of the R404A refrigeration system and the indirect refrigeration system tended to be inversely related to the coefficient of performance. Regardless of any experimental conditions, the exergy loss rate of components was the largest in the compressor, followed by the R404A condenser, the expansion valve, the internal heat exchanger, the CO2 cooler, the CO2 evaporator and the pump. Therefore, in conclusion, it is necessary to reduce exergy loss in the compressor and the R404A condenser to improve the overall performance of this system.

PERFORMANCE ANALYSIS OF TRANSCRITICAL CO2 REFRIGERATION SYSTEM FOR SUPERMARKET APPLICATION

Environmental issues becomes a priority on the refrigeration system development. The mainissues are global warming and ozone depletion which are emitted from the conventional refrigeration system.One of the natural and clean refrigerants is Carbon dioxide (CO2). CO2 refrigeration system however still haslow performance when operating at high ambient temperature. This study aim is to investigate the performanceof CO2 transcritical refrigeration system in high outdoor temperature. The research was carried out bytheoretical study and numerical analysis of the refrigeration system using the EES (Engineering EquationSolver) program. Data input and simulation validation were obtained from experimental and secondary data.The result showed that the coefficient of performance (COP) decreased gradually with the outdoor temperaturevariation increasing. With temperature input increases between 25oC – 45oC, the performance (indicated byoverall COP) decreased by 3.0 %. These results will be significantly important for a preliminary reference toimprove the CO2 refrigeration system design in hot climate temperature application.

Optimisation of the evaporator of a refrigerator employing hydrocarbon as a refrigerant

ABSTRACT The refrigeration and air conditioning system is a booming research in the research area. In refrigeration, the scientists focus on the new refrigerant in order to reduce the global warming potential (GWP), high coefficient of performance (COP) and meet zero ozone depletion potential (ODP). Not only the new refrigerant as a solution to attain zero ODP, high COP and at the same time to optimise the design of refrigeration system to meet ODP and COP as a required level. This paper aims to optimise the design of a double refrigerator evaporator for a refrigerator employing non ozone-depleting hydrocarbon refrigerant using brine as a secondary solution with a low GWP. It is done by numerical modelling followed by the parametric modelling using CATIA V5.

Development and performance of a heat driven R141b ejector air conditioner: Application in hot climate country

This paper proposes the design, construction, and test of a prototype R141b ejector refrigeration system. It was used as an air conditioner for a hot climate country (Thailand). The prototype machine was designed to work as a water chiller to provide thermal comfort condition for the tested room with the cooling capacity up to 4500 W. It was driven by hot water with temperatures of 90–98 °C. The condenser was cooled by water, which was provided by a cooling tower, with temperatures of 28–32 °C. CFD simulation was also employed to design the ejector. The tested results indicated that the prototype R141b ejector refrigerator working as an air conditioner was satisfactory in operating conditions consistent with a hot climate (Thailand's environment). The temperature of the air conditioned space was around 23 to 25 °C with the cooling load of 4500 W. The coefficient of performance (COP) was between 0.42 and 0.47.

Accurate modeling of vapor–liquid equilibria of binary mixtures of refrigerants using intelligent models

Developing simple, accurate and general models for prediction of different properties of hydrofluorocarbons (HFCs) and hydrocarbons (HCs) with hydrofluoro-olefins (HFOs) mixtures is of crucial importance in the design of new refrigeration system. In this communication, four computer based models namely Radial Basis Function Neural Network, Multilayer Perceptron Neural Network, Least Square Support Vector Machine optimized by Coupled Simulated Annealing and Adaptive Neuro Fuzzy Inference System trained by Hybrid method were used for prediction of vapor–liquid equilibrium (VLE) for binary mixtures of different HFC and HC compounds with HFO refrigerants. Results reveal that the developed models are accurate and effective for prediction of experimental VLE data for different systems. However, the RBF-NN model provides better predictions compared to other models. Moreover, the predictions of the developed models were better than the Peng-Robinson (PR) and Soave–Redlich–Kwong (SRK) equations of state (EoSs).

Optimal heat pump integration in industrial processes

Among the options for industrial waste heat recovery and reuse which are currently discussed, heat pumping receives far less attention than other technologies (e.g. organic rankine cycles). This, in particular, can be linked to a lack of comprehensive methods for optimal design of industrial heat pump and refrigeration systems, which must take into account technical insights, mathematical principles and state-of-the-art features. Such methods could serve in a twofold manner: (1) in providing a foundation for analysis of heat pump economic and energetic saving potentials in different industries, and further (2) in giving directions for experimentalists and equipment manufacturers to adapt and develop heat pump equipment to better fit the process needs.This work presents a novel heat pump synthesis method embedded in a computational framework to provide a basis for such analysis. The superstructure-based approach is solved in a decomposition solution strategy based on mathematical programming. Heat pump features are incorporated in a comprehensive way while considering technical limitations and providing a set of solutions to allow expert-based decision making at the final stage.Benchmarking is completed by applying the method on a set of literature cases which yields improved-cost solutions between 5% and 30% compared to those reported previously. An extended version of one case is presented considering fluid selection, heat exchanger network (HEN) cost estimations, and technical constraints. The extended case highlights a trade-off between energy efficiency and system complexity expressed in number of compression stages, gas- and sub-cooling. This is especially evident when comparing the solutions with 3 and 5 compression stages causing an increase of the COP from 2.9 to 3.1 at 3% increase in total annualized costs (TAC).

Integrative thermodynamic optimization of a vapor compression refrigeration system based on dynamic system responses

We optimized the internal structure (heat exchanger areas) of a dynamic vapor compression refrigeration system for maximum global system performance described by the coefficient of performance (COP), refrigeration rate, second law efficiency, and pull-down time. The numerical optimization was subjected to fixed system heat transfer surface, and the relative sizes of condenser and evaporator were selected optimally via parametric sweeps. Optimization results demonstrated the existence of distinct optimal area allocation for each objective function considered herein while higher evaporator to condenser global heat transfer ratio was preferred in all cases. Maximum COP was achieved, for instance, with smaller evaporator area than maximum second law efficiency that yielded shorter pull-down time and lower refrigerated space temperature in exchange for slightly higher compressor power and total exergy destruction. In summary, this work provides insights into the selection of an optimal refrigeration system design based on its dynamic responses and physical implications.

Variation principle in calculating the flow of a two-phase mixture in the pipes of the cooling systems in high-rise buildings

The analytical solution of one of the urgent problems of modern hydromechanics and heat engineering about the distribution of gas and liquid phases along the channel cross-section, the thickness of the annular layer and their connection with the mass content of the gas phase in the gas-liquid flow is given in the paper.The analytical method is based on the fundamental laws of theoretical mechanics and thermophysics on the minimum of energy dissipation and the minimum rate of increase in the system entropy, which determine the stability of stationary states and processes. Obtained dependencies disclose the physical laws of the motion of two-phase media and can be used in hydraulic calculations during the design and operation of refrigeration and air conditioning systems.

Simulation of Transcritical CO2 Refrigeration System with Booster Hot Gas Bypass in Tropical Climate

A Simulation computer becomes significant important for performance analysis since there is high cost and time allocation to build an experimental rig, especially for CO2 refrigeration system. Besides, to modify the rig also need additional cos and time. One of computer program simulation that is very eligible to refrigeration system is Engineering Equation System (EES). In term of CO2 refrigeration system, environmental issues becomes priority on the refrigeration system development since the Carbon dioxide (CO2) is natural and clean refrigerant. This study aims is to analysis the EES simulation effectiveness to perform CO2 transcritical refrigeration system with booster hot gas bypass in high outdoor temperature. The research was carried out by theoretical study and numerical analysis of the refrigeration system using the EES program. Data input and simulation validation were obtained from experimental and secondary data. The result showed that the coefficient of performance (COP) decreased gradually with the outdoor temperature variation increasing. The results show the program can calculate the performance of the refrigeration system with quick running time and accurate. So, it will be significant important for the preliminary reference to improve the CO2 refrigeration system design for the hot climate temperature.

Optimal synthesis of compression refrigeration system using a novel MINLP approach

Abstract The optimal design of a compression refrigeration system (CRS) with multiple temperature levels is very important to chemical process industries and also represents considerable challenges in process systems engineering. In this paper, a general methodology for the optimal synthesis of the CRS, which simultaneously integrates CRS and Heat Exchanger Networks (HEN) to minimize the total compressor shaft work consumption based on an MINLP model, has been proposed. The major contribution of this method is in addressing the optimal design of refrigeration cycle with variable refrigeration temperature levels. The method can be used to make major decisions in the CRS design, such as the number of levels, temperature levels, and heat transfer duties. The performance of the developed methodology has been illustrated with a case study of an ethylene CRS in an industrial ethylene plant, and the optimal solution has been examined by rigorous simulations in Aspen Plus to verify its feasibility and consistency.

Optimum design of a solar ejector refrigeration system for various operating scenarios

The objective of this work is to examine a solar ejector refrigeration system under various operating scenarios. Evacuated tube collectors of 100 m2 collecting area coupled to a storage tank of 4 m3 are selected for feeding the generator of the refrigerator. The system is examined for different evaporator temperatures from −10 °C to 10 °C and for different heat rejection temperatures from 30 °C to 50 °C. In every case, the system is optimized by selecting the optimum ejector design and the optimum generator temperature. Different refrigerants are examined as R123, R245fa, R600a and R134a, while the emphasis is given to the R141b. The innovation of this work is based on the systematic examination and optimization of a great range of operating scenarios giving a clear image for the system performance. According to the final results, the R141b is found to be the best candidate in all the operating scenarios. More specifically, the maximum system COP is found to be 0.234 when the system produces refrigeration at 10 °C and rejects heat to the environment at 30 °C. The optimum generator temperatures are found to be from 114 °C to 157 °C and the cooling capacity is ranged from 1.85 kW up to 23.39 kW. The analysis is performed with a developed model in EES (Engineering Equation Solver) under steady-state conditions.

Design of solar adsorption refrigeration system with CPC and study on the heat and mass transfer performance

To overcome the problem that the heat source temperature is limited and the lower part of the adsorption tube cannot effectively absorb the solar radiation when solar radiation as the heat source of the adsorption refrigeration system. From the perspective of enhancing the adsorption refrigeration unit tube to absorb solar radiation, thereby strengthening the heat transfer characteristic of adsorption bed, which can improve the efficiency of the refrigeration unit refrigerating capacity and system refrigeration efficiency. Solar adsorption refrigeration system based on CPC was designed and constructed in this paper. The heat and mass transfer performance of the adsorption refrigeration system were studied. The experimental results show that the temperature of the adsorption bed with parabolic concentrating structure can rise to 100°C under low irradiation condition. When the irradiation intensity is 600 w/m2 and 400 w/m2, the average temperature rising to desorption temperature reaches 0.67°C and 0.50°C, respectively. It can effectively solve the problem that the conventional adsorption bed is difficult to reach the required desorption temperature due to the low power density of the sunlight. In the experiment, the system COP were 0.166 and 0.143 when the system in the irradiance of 600 w/m2 and 400 w/m2.

Design of refrigeration system using refrigerant R134a for macro compartment

The main objective of this study is to analyse and design an optimum cooling system for macro compartment. Current product of the refrigerator is not specified for single function and not compact in size. Hence, a refrigeration system using refrigerant R134a is aimed to provide instant cooling in a macro compartment with sizing about 150 × 150 × 250 mm. The macro compartment is purposely designed to fit a bottle or drink can, which is then cooled to a desired drinking temperature of about 8°C within a period of 1 minute. The study is not only concerned with analysing of heat load of the macro compartment containing drink can, but also focused on determining suitable heat exchanger volume for both evaporator and condenser, calculating compressor displacement value and computing suitable resistance value of the expansion valve. Method of optimization is used to obtain the best solution of the problem. Mollier diagram is necessary in the process of developing the refrigeration system. Selection of blower is made properly to allow air circulation and to increase the flow rate for higher heat transfer rate. Property data are taken precisely from thermodynamic property tables. As the main four components, namely condenser, compressor, evaporator and expansion valve are fully developed, the refrigeration system is complete.

Parametric study of a novel organic Rankine cycle combined with a cascade refrigeration cycle (ORC-CRS) using natural refrigerants

This paper presents a novel design of a stand-alone refrigeration system consisting of a combined organic Rankine cycle and a cascade refrigeration system (ORC-CRS) for low-evaporation-temperature applications (from −55°C to −30°C). Natural refrigerants were used as working fluids: toluene for the organic Rankine cycle and NH3/CO2 for the cascade refrigeration system. A parametric study and a regression analysis have been performed to characterize the system and to estimate the overall system coefficient of performance (COPoval) and exergetic efficiency (ηex_oval). The highest values of COPoval and ηex_oval calculated were 0.79 and 31.6%, corresponding to ORC evaporation temperatures of 315°C and 255°C, respectively. Renewable thermal energy sources from 100 to 350°C can be used to drive the facility, thus reducing dependence on fossil fuel and CO2 emissions. This stand-alone facility seems to be a feasible option to exploit low- and medium-grade thermal energy (geothermal, solar, waste heat) in places where the electricity supply is unreliable.

Refrigeration Requirements for Precooling and Fermentation Control in Wine Making

A database is provided which can be used as a guide to determine the maximum refrigeration capacity required during wine making (precooling and fermentation control). Factors such as maximum daily grape intake, temperature of the grapes, precooling period, fermentation rate, heat gain in the fermentation building, heat gain in the refrigerated water distribution system as well as the efficiency of refrigeration systems are considered. Graphs, as well as equations, are provided from which the maximum refrigeration capacity required for grape intakes varying from 25 t - 1 000 t per day can be determined in kJ/h. Provision is made for three different precooling periods. Separate graphs are provided from which the influence of the temperature of the grapes, as well as the influence of heat gain in refrigerated water distribution systems on the overall refrigeration capacity required, can be determined respectively. The database cannot replace thorough detailed refrigeration system design and engineering. However, it provides wine makers with a simple guide whereby designs can be checked, or the use of the capacity of existing systems managed more effectively.

Experimental investigation on waste heat driven activated carbon-methanol adsorption cooling system

This paper presents design and fabrication of an adsorption refrigeration system working with activated carbon-methanol and coupled to the exhaust system of a multi-cylinder turbo-charged diesel engine. We have also carried out experiments to study the cycle time, refrigeration effect and COP of the cycle. This paper is reported of the original experimental data obtained from experimentation of a real adsorption refrigeration setup. We have studied and reported the effects of minimum bed temperature (T 1) and maximum bed temperature (T 3), the two most important parameters influencing the performance of an adsorption refrigeration system. From experimental result it is observed that the maximum temperature (T 3) of the cycle should be kept as high as possible to generate higher volume of methanol from the activated carbon and, hence, higher refrigeration effect and COP. Since, the temperature of hot water circulated through the desorption bed has been restricted to 90 °C, it takes long time duration to achieve T 3 above 80 °C and hence, during the experiment, the maximum temperature of the bed (T 3) has been limited to 80 °C. It is also observed that the minimum temperature of the bed (i.e., the temperature of the bed after end of adsorption) (T 1) should be kept as low as possible to optimize COP of the cycle. The experimental results show that, for T 1 of 30 °C and T 3 of 80 °C, the maximum refrigeration effect is 1519.41 kJ per cycle for the given configuration of the refrigeration system and the cycle COP is 0.21. Uncertainty analysis predicts that variation of experimental COP varies between ±6.59%. This paper also presents different practical problems that faced by the authors during fabrication of the setup, for the benefit of the future researchers. The study also aims to comment on the capability of meeting the air-conditioning requirement of a vehicle by the waste heat associated with exhaust gases only, without requiring any extra power from the engine, thereby reducing fuel consumption and environment pollution.

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