Ejector Air Conditioning System Research Articles

Thermal performance assessment of an ejector air-conditioning system with parabolic trough collector using R718 as a refrigerant: A case study in Algerian desert region

This paper investigates a safety control room with 18 kW of cooling load, where a parabolic trough collector is connected to an R718 ejector air-conditioning subsystem. Engineering Equation Solver is used as a programming tool to conduct the dynamic study of the proposed system. After model validation, the optical thermal and exergy efficiency of studied solar collector, main ejector diameters, ejector mass ratio, coefficient of performance of ejector air-conditioning subsystem, and solar performance coefficient (or system thermal ratio) have been accurately determined under different operating conditions. Regarding the studied solar collector, its optical, thermal, and energy performances are acceptable, with values of 79.15 %, 67.06 %, and 19.14 %, respectively. At the best-operating conditions (Tg = 413.15 K, Te = 283.15 K, and Tc = 298.15 K), the maximum performance of the ejector air-conditioning loop was estimated at 1.193, while the system thermal ratio for the studied solar air conditioner was 0.81. For a steady-state thermal operation, a hot storage tank was incorporated between the studied solar collector and the ejector air-conditioning subsystem with two different storage liquids (Therminol VP-1 oil and Hitec XL molten salt); the daily maximum storage temperature reached was thus 424.15 K.

Modelling and thermodynamic analysis of ejector flow for application at design and off design operating conditions in an ejector air conditioner

Ejector flow in an ejector air conditioning system using R245fa is analysed for entrainment ratio and potential refrigeration effect, at varying temperature and heat input conditions in the generator ranging from 60C to 100C and 2kW to 5kW respectively. The effect of varying generator temperature in cooling capacity of the system when the vapour ejectoris operating at design evaporator and condenser temperatures of 10C and 35C respectively is investigated. The mathematical model of the vapour ejector with optimum area ratio is developed and validated. A critical entrainment ratio of 0.385 is obtained corresponding to generator temperature of 100C. When the generator temperature is varied from 60C to 100C, the cooling capacity range from 0.3kW at generator heat input of 2 kW to 1.78 kW at 5 kW heat input. Further, the operation of the system is analysed for off design operating condition corresponding to reduced heat input rate in the generator. In that case the state of primary refrigerant flow in ejector inlet will be two phase and a mathematical model for two-phase ejector flow is developed and validated. Ejector flow analysis revealed the minimum quality of flow at ejector inlet to maintain adequate backpressure for condensation to occur range from 0.72 at 60C to 0.22 at 100C. The corresponding refrigeration refrigeration effect produced is less than the respective designed operation value byits 12.2% to 8%. Further, analysis of the system shows that at least 7 kW heat input at 100C is required to produce 1 ton of cooling effect.
 Ejector flow in an ejector air conditioning system using R245fa is analysed for entrainment ratio and potential refrigeration effect, at varying temperature and heat input conditions in the generator ranging from 60C to 100C and 2kW to 5kW respectively. The effect of varying generator temperature in cooling capacity of the system when the vapour ejectoris operating at design evaporator and condenser temperatures of 10C and 35C respectively is investigated. The mathematical model of the vapour ejector with optimum area ratio is developed and validated. A critical entrainment ratio of 0.385 is obtained corresponding to generator temperature of 100C. When the generator temperature is varied from 60C to 100C, the cooling capacity range from 0.3kW at generator heat input of 2 kW to 1.78 kW at 5 kW heat input. Further, the operation of the system is analysed for off design operating condition corresponding to reduced heat input rate in the generator. In that case the state of primary refrigerant flow in ejector inlet will be two phase and a mathematical model for two-phase ejector flow is developed and validated. Ejector flow analysis revealed the minimum quality of flow at ejector inlet to maintain adequate backpressure for condensation to occur range from 0.72 at 60C to 0.22 at 100C. The corresponding refrigeration refrigeration effect produced is less than the respective designed operation value byits 12.2% to 8%. Further, analysis of the system shows that at least 7 kW heat input at 100C is required to produce 1 ton of cooling effect.

PERFORMANCE ANALYSIS OF A SOLAR-DRIVEN EJECTOR AIR CONDITIONING SYSTEM UNDER EL-OUED CLIMATIC CONDITIONS, ALGERIA

In order to understand the behavior and to determine the effective operational parameters of a solar-driven ejector air conditioning system at low or medium temperature, a dynamic model depends on the principles of conservation, the momentum mass and energy is developed. For this purpose, the thermodynamic characteristics of the liquid and vapor refrigerant were identified using the Engineering Equation Solver (EES) software. Linear Fresnel solar reflector has been used as a tool to convert solar energy into thermal energy. Water (R718) was used as a refrigerant. The operational conditions for the studied solar-driven ejector air conditioning system are as follows: evaporator temperature “Te =283.15 K”, condenser temperature “Tc =305.15 K”, and generator temperature “Tg = 373.15 K”. The performance of the ejector air conditioning system was compared as a function of the operating parameters of the subsystem. The average value of thermal efficiency of the Fresnel linear concentrator has reached 31.60 %, the drive ratio “ω” is 0.4934, the performance value of the ejector air conditioning subsystem “COPejc” is 60.664 % and the average value of the thermal performance of the machine “STR” has touched 19.17 %. The results obtained through this scientific subject are stimulating and encouraging, where this technique can be used for air conditioning in desert areas in southern Algeria, where fossil energy (petroleum, gas, etc.) is extracted and produced in various types.

Applying a variable geometry ejector in a solar ejector refrigeration system

Abstract This paper presents an experimental study of the influence of a variable geometry ejector (VGE) design on the performance of a small-scale, 1.5 kW nominal capacity solar heat driven ejector air-conditioning system under real-life working conditions. Under variable operating conditions (e.g. solar radiation, ambient temperature) fixed geometry ejector performs poorly, therefore the objective of the present work was to prove the benefit of the VGE concept. In the experimentally tested VGE the area ratio through a movable spindle (SP) and the nozzle exit position (NXP) can be adjusted in order to respond to the operating conditions. The results showed very stable operation of the cooling cycle during the experiments. Both NXP, SP had considerable influences on the cooling cycle performance. An optimal NXP was identified, which did not change with various operating conditions. Similarly, SP also showed an optimum; however, the optimum point depended strongly on the operating conditions. The results clearly indicated the benefit of using the VGE design over the fixed geometry. COP improvement was as high as 24% with a maximum of 0.29 corresponding to a cooling capacity of 1.6 kW when compared to a fixed geometry ejector. The study also confirmed the importance of using a variable-speed pump in the ejector cycle.

Optimization of a hybrid ejector air conditioning system with PSOGA

In this paper, a model-based optimization strategy for a hybrid ejector air conditioning system is presented. By investigating the operating characteristics of the energy consuming components, the energy consumption models for generator, compressor, fans and pump are developed with experimental validation. The validation results indicate the proposed models are accurate enough for optimization issue. Then, the optimization problem is formulated with objective to achieve minimum energy consumption while meets the required cooling loads at the same time. The physical constraints and interaction between components are also illustrated. In order to solve this optimization problem, a PSOGA optimization approach is proposed. PSOGA takes the advantages of both particle swarm optimization (pso) and genetic algorithm (ga) with fast convergent speed and high accuracy. The cooling load is obtained based on corresponding temperature collected from 6am to 20pm on a single day. The comparison result between traditional on-off control and proposed PSOGA indicates the better performance of PSOGA with more energy saving achieved. Additional, the energy saving effect achieves its highest value at 32°C with 17%.

Modeling of a hybrid ejector air conditioning system using artificial neural networks

In order to predict the performance of a hybrid ejector air conditioning system, neural network is chosen to model the proposed platform. First, three different types of neural networks, namely multi-layer perceptron (MLP), radial basis function (RBF) and support vector machine (SVM) are applied to model the component of a hybrid ejector air conditioning system. The MLP outperforms other two networks in this research and therefore it is selected to model the whole system. Since there is no formal criterion about input selection so far, a date-mining algorithm, boosting tree, is employed before system modeling to search the most significant parameters among the 19 input variables and the five most influential parameters of them are selected to be the final input of the system model. And the result shows a good agreement between predicted and measured value which indicates the excellent ability of MLP.

THE PERFORMANCES OF A MODIFIED EJECTOR AIR CONDITIONING CYCLE

Residential and commercial air conditioning systems have contributed to high electricity usage and cost in daily living. People nowadays look forward to environmental friendly products, as well as saving operating cost. Air conditioning system using ejector as two phase expansion valve was studied earlier to obtain better performance in terms of energy saving. The purpose of this study was to prove that ejector air conditioning system has better coefficient of performance (COP) than conventional air conditioning system. Two refrigerant cycles, including standard cycle and modified ejector cycle had been studied and their characteristics were investigated. Electrically heated ambient air was used to obtain higher ambient air temperatures. The experiments were run by using R22 and R290. The experiments were carried out by using standard cycle and modified ejector cycle system. On top of that, analyses were conducted on the results obtained from the experiments. Moreover, it had been proved that modified ejector cycle had higher COP than standard refrigeration cycle.

Determination of the ejector dimensions of a bus air-conditioning system using analytical and numerical methods

Comfortable journey with commercial buses is an essential goal of transportation companies. An air-conditioning system can play an important role for this comfortable journey but it can put extra load on the engine and extra cost in the fuel consumption. The purpose of this work is to increase the performance of air-conditioning system of the buses by reducing the load on the engine and fuel consumption. Using a two-phase ejector as an expansion valve can increase the coefficient of performance (COP) of the air-conditioning system. An improvement in the COP can reduce the empty vehicle weight and fuel consumption of buses. Two-phase ejector dimensions can be determined using the empirical methods available in the literature. In this paper, the two-phase ejector dimensions of air conditioning system for a bus are calculated using the analytical and numerical methods. First of all, the thermodynamic analysis of the vapor-compression refrigeration cycle with a two-phase ejector is performed, and then the ejector dimensions are subsequently determined. The cooling loads of the midibus and bus with R134a as a refrigerant are assumed to be 14 kW and 32 kW, respectively. The total length of the two-phase ejector for the midibuses and buses due to these cooling loads, are computed to be 480.8 mm and 793.1 mm, respectively. Also, an experimental setup is installed on a midibus air conditioner to turn it into the ejector air conditioning system to validate theoretical results with the experimental study.

Thermodynamic analysis of the two-phase ejector air-conditioning system for buses

Air-conditioning compressors of the buses are usually operated with the power taken from the engine of the buses. Therefore, an improvement in the air-conditioning system will reduce the fuel consumption of the buses. The improvement in the coefficient of performance (COP) of the air-conditioning system can be provided by using the two-phase ejector as an expansion valve in the air-conditioning system. In this study, the thermodynamic analysis of bus air-conditioning system enhanced with a two-phase ejector and two evaporators is performed. Thermodynamic analysis is made assuming that the mixing process in ejector occurs at constant cross-sectional area and constant pressure. The increase rate in the COP with respect to conventional system is analyzed in terms of the subcooling, condenser and evaporator temperatures. The analysis shows that COP improvement of the system by using the two phase ejector as an expansion device is 15% depending on design parameters of the existing bus air-conditioning system.

Experimental investigations of solar driven ejector air-conditioning system

Abstract Recently, a rapid growth in various applications of ejector refrigeration systems has been observed in numerous sectors. With the applications based on solar or waste energy, designed to supply the motive energy have becoming widespread, a real alternative to compression devices in air-conditioning technologies has become a fact. Furthermore, it has been shown that ejector systems may effectively compete with absorption systems under temperature of the motive heat source lower than 80 °C. This paper presents experimental investigations carried out on a specially constructed prototype/stand for the ejector air-conditioning, operating with isobutane as a working fluid under motive vapour temperature below 75 °C. The effects of operation parameters have been thoroughly analysed. The ejector cycle performance coefficient was presented and discussed. The loss coefficient for the ejector was determined as well. It has been shown that loss coefficient in the investigated set-up is higher than 0.75.

Performance Analysis of a Solar-powered Ejector Air-conditioning Cycle with Heavier Hydrocarbons as Refrigerants

In this paper the overall performance of the solar-powered ejector air-conditioning system, using pentane (R601) and hexane (R602) as a refrigerants, is presented. The modeling process and the efficiency of solar vapor generator (SVG) were shown. The effects of condenser and generator temperatures were examined. Simulation results indicated that condensing temperature had a strong influence on the ejector's performance. Maximum overall systems’ value of COP, obtained for refrigerants R601 and R602, were 0.1 and 0.5, respectively, at Te=12°C, Tc=30°C, and G=800 W·m-2. Generator temperatures were 100–190°C for pentane and 100–200°C for hexane.

Optimum selection of solar collectors for a solar-driven ejector air conditioning system by experimental and simulation study

In this paper, three different solar collectors are selected to drive the solar ejector air conditioning system for Mediterranean climate. The performance of the three selected solar collector are evaluated by computer simulation and lab test. Computer model is incorporated with a set of heat balance equations being able to analyze heat transfer process occurring in separate regions of the collector. It is found simulation and test has a good agreement. By the analysis of the computer simulation and test result, the solar ejector cooling system using the evacuated tube collector with selective surface and high performance heat pipe can be most economical when operated at the optimum generating temperature of the ejector cooling machine.

Study on the key ejector structures of the waste heat-driven ejector air conditioning system with R236fa as working fluid

The ejector performance is numerically and experimentally studied using R236fa as working fluid to analyze the influence of the key geometries of ejector. The computational fluid dynamics (CFD) was employed to predict the flow process and performance of the ejector. A case study was provided in this paper, in which the angles of nozzle outlet were 8°, 10° and 14°, the distance of nozzle exit to mixing chamber was varied as 23 and 33mm and the length of diffuser was varied as 88 and 103mm. The CFD results were verified with an experiment. It can be concluded that, the ejector with the nozzle outlet angle of 8°, the distance of nozzle exit to mixing chamber of 23mm and the diffuser length of 88mm has the best performance.

Numerical simulation of a solar-assisted ejector air conditioning system with cold storage

Indoor space cooling represents a large potential for solar energy use due to the relative coincidence between energy availability and cooling demand. Solar-assisted air conditioning (AC) applications emerged with the development of high efficiency solar collectors. Energy storage (hot or cold) must be implemented for solar-assisted AC applications when cooling demand is present during intervals without available solar energy and also for cooling capacity optimisation (“peak shaving”). The present paper analyses a solar-assisted ejector cooling system with cold storage. Simulations were carried out over one year considering climatic data for a hot location (Béchar, Algeria) and the performance of the system was assessed for a set of design conditions. Effects of cold storage upon comfort conditions and energy demand were evaluated. Maximum room temperature and overall interval of time during which the room temperature exceeded the set-point value were the parameters used to quantify system performance. It was found that cold storage improved comfort conditions compared to a system without storage. For some design conditions it was found that increasing the cold storage capacity did not result in improved comfort conditions. The control algorithm of the system was identified as the cause of this behaviour. ► Solar-assisted air conditioning is an interesting technology since the peak demand is to some extent synchronous and proportional to the available energy from the Sun. ► Energy storage component is essential in a solar-assisted air conditioning system if the cooling demand is continuous. ► Cold storage system capacity influences both the comfort and the air conditioning system parameters and performance. ► Although simple, cheap and reliable, the ejector cycle lowers the overall efficiency of the solar-assisted air conditioning system.

A solar ejector air-conditioning system using environment-friendly working fluids

In this paper, the performance of the solar-driven ejector air conditioning with several environment-friendly working fluids is studied. The effect of the fluid nature and operating conditions on the ejector performance is examined. This performance is calculated using an empirical correlation. Thermodynamic properties of functioning fluids are obtained with a package REFPROP7. It appears that the refrigerant R717 offers the highest coefficient of performance (COP). For generator temperature TB = 90°C, condenser temperature TC = 35°C and evaporator temperature TE = 15°C and with R717, the COP of ejector air-conditioning system is 0.408. Using a meteorological data for the city of Tunis, the system performance is computed for three collector types. The air-conditioning season and period were taken for six months from April to September. The daily period is between 8 and 17 h. For the solar air-conditioning application, the COP of the overall system varied from 0.21 to 0.28 and the exergy efficiency varied from 0.14 to 0.19 with the same working conditions and total solar radiation (351–875 Wm−2) in July. Copyright © 2008 John Wiley & Sons, Ltd.

Revisiting solar-powered ejector air conditioner––the greener the better

Pervious work on solar-powered ejector air-conditioning system is updated for refrigerant R-142b to replace R-114 as the working fluid. Such update offers viable alternative to the system, which previously used the now banned R-114. Cycles with and without compression enhancements are analyzed to produce variety of systems to suit variety of local considerations. The result of the analysis and simulation introduces not only an environmentally compatible but also a more efficient system.