Performance testing of a novel ejector refrigerator for various controlled conditions

The paper presents the experimental results of a novel ejector refrigerator that was designed to be suitable for an air‐conditioning application using vacuum tube solar collectors for vapour generation. The primary flow of the ejector is controlled using a spindle in order to provide fine tuning for ejector operation as heat input changes with solar radiation. Water, the most environmentally friendly substance is used as the working fluid. The performance of the ejector was tested for a range of controlled primary flows, boiler temperatures, condensation capacities using different primary nozzles with different lengths. The effect of the operating conditions and nozzle length on the performance of the ejector was analyzed. It was found that in the tested boiler temperature range of 84–96°C the maximum cooling capacity (4.01 kW) of the ejector with short nozzle is much higher than that of the ejector with long nozzle (2.9 kW) on the spindle position of 21 mm. However, the ejector with long nozzle has increased COP when the boiler temperature is below 88°C and has higher critical back pressure. Copyright © 2010 John Wiley & Sons, Ltd.     

Cycle improvements to ejector‐expansion transcritical CO2 two‐stage refrigeration cycle

In this paper, a new configuration of ejector‐expansion transcritical CO₂ (TRCC) refrigeration cycle is presented, which uses an internal heat exchanger and intercooler to enhance the performance of the new cycle. The theoretical analysis on the performance characteristics was carried out for the new cycle based on the first and second laws of thermodynamics. It was found that, compared with the conventional transcritical CO₂ cycle and ejector‐expansion transcritical CO₂ cycle, the simulation results show that the coefficient of performance and second law efficiency of the new cycle were increased by about 55.5 and 26%, respectively, under the operating conditions that evaporator temperature is 10°C, gas cooler outlet temperature is 40°C and gas cooler pressure is optimum pressure. It is also concluded that the entrainment ratio for the new ejector‐expansion TRCC cycle is on average 35% higher than that of the conventional ejector‐expansion TRCC cycle. The analysis results are of significance to provide theoretical basis for design optimization of the transcritical CO₂ refrigeration cycle with an ejector‐expansion device, internal heat exchanger and intercooler. Copyright © 2007 John Wiley & Sons, Ltd.     

Experimental investigation of the performance of a solar‐assisted ground‐source heat pump system for greenhouse heating

The main objective of the present study is to investigate the performance characteristics of a solar‐assisted ground‐source heat pump system (SAGSHPS) for greenhouse heating with a 50 m vertical 1¼ in nominal diameter U‐bend ground heat exchanger. This system was designed and installed in the Solar Energy Institute, Ege University, Izmir (568 degree days cooling, base: 22°C, 1226 degree days heating, base: 18°C), Turkey. Based upon the measurements made in the heating mode, the heat extraction rate from the soil is found to be, on average, 54.08 Wm^?1 of bore depth, while the required borehole length in meter per kW of heating capacity is obtained as 12.57. The entering water temperature to the unit ranges from 8.2 to 16.2°C, with an average value of 9.1°C. The greenhouse air is at a maximum day temperature of 25°C and night temperature of 14°C with a relative humidity of 40%. The heating coefficient of performance of the heat pump (COP_HP) is about 2.13 at the end of a cloudy day, while it is about 2.84 at the end of sunny day and fluctuates between these values in other times. The COP values for the whole system are also obtained to be 5–15% lower than COP_HP. Copyright © 2004 John Wiley & Sons, Ltd.     

Thermal design of parabolic solar concentrator adsorption refrigeration system

This study presents a thermal design of solar-powered adsorption refrigeration with the type of activated carbon-methanol pair. The designed module consists of an evacuated glass tube equipped with a parabolic solar concentrator as generator, sorption bed, evaporator, and condenser units. A thermodynamic design procedure and a mathematical model of a steady state system with activated carbon refrigerator have been developed. The adsorber is heated by solar energy collected by a parabolic solar concentrator. The temperature of the working pair in the adsorber, the amount of methanol leaving and reabsorb bed, and the refrigerated box was estimated. An optimize design of the system to achieve higher cycle COP was presented. Maximum cycle COP = 0.576 and COP_net = 0.375 with T _max reached 157.8°C, T _B = 57.5°C, M _ac = 0.907 kg, and the concentration of methanoldesorped equal to 0.206 kg/kg _ac .     

Steam jet ejector cooling powered by waste or solar heat

A small scale steam jet ejector experimental setup was designed and manufactured. This ejector setup consists of an open loop configuration and the boiler operate in the temperature range of T_b = 85–140 °C. The typical evaporator liquid temperatures range from T_e = 5 °C to 10 °C while the typical water-cooled condenser pressure ranges from P_c = 1.70 kPa to 5.63 kPa (T_c = 15–35 °C). The boiler is powered by two 4 kW electric elements while a 3 kW electric element simulates the cooling load in the evaporator. The electric elements are controlled by means of variacs.Primary nozzles with throat diameters of 2.5 mm, 3.0 mm and 3.5 mm are tested while the secondary ejector throat diameter remains unchanged at 18 mm. These primary nozzles allow the boiler to operate in the temperature range of T_b = 85–110 °C. When the nozzle throat diameter is increased, the minimum boiler temperature decreases. A primary nozzle with a 3.5 mm throat diameter was tested at a boiler temperature of T_b = 95 °C, an evaporator temperature of T_e = 10 °C and a critical condenser pressure of P_crit = 2.67 kPa (22.6 °C). The system's COP is 0.253.In a case study the experimental data of a solar powered steam jet ejector air conditioner is investigated. Solar powered steam ejector air conditioning systems are technical and economical viable when compared to conventional vapour compression air conditioners. Such a system can either utilise flat plate or evacuated tube solar thermal collectors depending on the type of solar energy available.     

Performance characteristics of two combined ejector–absorption cycles

The paper describes the performance of an ammonia–water combined ejector–absorption cycle as refrigerator using two simple models. In the first an ejector draws vapour from an evaporator and discharges to a condenser. In the second, an ejector draws vapour from an evaporator and discharges to an absorber. The thermodynamics cycles and ejector operation on the temperature–entropy charts are shown. The thermodynamics of the combined ejector–absorption cycle are simulated by a suitable method and a corresponding computer code, based on analytic functions, describes the behaviour of the binary mixture NH₃–H₂O. It was found from the first model that the refrigerator (theoretical) coefficient of performance (COP) varied from 1.099 to 1.355 when the operation conditions were: generation temperature (237°C), condenser temperature (25.9–30.6°C), absorber temperature (48.6–59.1°C) and evaporator temperature (−1.1–7.7°C). In the second the theoretical COP vary from 0.274 to 0.382 when the operation conditions were: generation temperature (237°C), condenser temperature (91°C), absorber temperature (76.7–81°C) and evaporator temperature (−1.1–7.7°C).     

Temperature–enthalpy/entropy charts of combined ejector–absorption cycle using NH3–H2O

This paper describes the performance of an ammonia–water combine ejector–absorption cycle as refrigerator and heat pump. This combination brings together the advantages of absorption and ejector systems. Also, thermodynamic cycles on the temperature–enthalpy and temperature–entropy charts are shown. The thermodynamics of the combined ejector–absorption cycles are simulated by a suitable method and a corresponding computer code, based on analytic functions describing the behaviour of the binary mixture NH₃–H₂O. It is found that in the case of the refrigerator and heat pump, the theoretical coefficient of performance (COP) or the theoretical heat gain factor (HGF) vary from 1.6 to 90.4 per cent and 0.7 to 37.6 per cent, greater than those of the conventional absorption system, respectively. The operation conditions were: generator temperature (205.5 to 237.1°C), condenser temperature (25.9 to 37.4°C) and evaporator temperature (−8.4 to 5°C). Copyright © 2000 John Wiley & Sons, Ltd.     

Thermodynamic properties and performance evaluation of [EMIM] [DMP]-H2O working pair for absorption cooling cycle

The combination of ionic liquid-refrigerant based [EMIM][DMP]-H₂O as an alternative working pair for single effect vapor absorption cycles (VACs) is assessed and optimized by using energy and exergy based performances. Thermodynamics properties of binary mixture of [EMIM] [DMP]-H₂O like Dühring's (P-T-x1) and h-T-X1 plots are computed from the activity coefficient based non-random two-liquid model (NRTL) model. Further modeling and simulation of VACs are accomplished in open source Scilab as mathematical programing software and used to ascertain the optimal generator temperature established on energetic and exergetic COP. Optimal results include an extensive range of temperatures like T_e from 2.5 to 15°C and T_a and T_c from 30 to 45°C. Simulation of the single effect VAC with SHE by using [EMIM][DMP]-H₂O mixture at T_e = 10°C, T_g = 100°C, T_a = 30°C, and T_c = 40°C were evaluated and compared with the 5 working fluids. Simulation outcomes depicted greater COP of 0.82 for [EMIM][DMP]-H₂O in comparison with NH₃-H₂O, EMISE-H₂O, [EMIM][BF4]-H₂O and nearly equal to LiBr-H₂O (COP = 0.83). In addition, the effect of T_g on the COP, ECOP f _, and composition are compared and optimized for the evaporation temperature range from 2.5 to 15°C, T_a/T_c from 30 to 45°C and cooling water (CW) flow in series and parallel. Additionally, the optimal T_g exhibited distinction based on energy and exergy analysis. Thus, it resulted in optimized performances of [EMIM] [DMP]-H₂O that can be suitable to replace corrosive aqueous LiBr in VACs.     

A comprehensive investigation on thermal management of large‐capacity pouch cell using micro heat pipe array

A proper and effective battery thermal management system (BTMS) is critical for large‐capacity pouch cells to guarantee a suitable operating temperature and temperature difference. Hence, in this paper, a micro heat pipe array (MHPA) is utilized to build the thermal management system for large‐capacity pouch cells. In order to study the property of BTMS in depth, experimental and numerical investigation are carried out by considering the C‐rate, working medium, air velocity and duty. The experimental results present that the T_max can be maintained below 43.7°C and the ΔT is below 4.9°C at the discharge rate of 3C in the battery module with MHPA‐liquid. Moreover, the T_max of the battery module with MHPA‐liquid falls as the air velocity increases. The simulation results show that the variation and distribution of temperature matched well with experimental results. It demonstrates that the MHPA‐based BTMS is viable and effective for large‐capacity pouch cell battery, even at high C‐rate and cycle duty.     

Numerical Simulation of the Performance of a Capillary Thermal Driven Ejector Refrigerator

A capillary driven ejector refrigerator is a new refrigeration system that can use solar energy and other low-grade heat sources. In this paper, the performance of the refrigeration system is simulated numerically by use of an iteration algorithm and block exchanging technology for all unit models. The flow and heat transfer characteristics in a solar collector, generator, ejector, condenser, and evaporator are analyzed and calculated. The results show that when the generating temperature is higher than 75–80°C and the environmental temperature is lower than 35°C, the system can work normally; the coefficient of performance of this refrigeration system is in the range of 0.05–0.15 by use of water as a refrigerant. The cooling capacity and COP increase with an increasing generative temperature and decreasing condensing pressure.     

Performance of hybrid refrigeration system using ammonia

This paper investigates the performance of a hybrid refrigeration system that combines sorption–conventional vapour compression refrigeration machine driven by dual source (heat and/or electricity). The dual source makes the system highly flexible and energy efficient. The ammonia refrigerant (R717) is used in both adsorption and associated conventional refrigeration cycles. The model of thermal compressor corresponds to a multiple pair of compact adsorption generators operating out of phase with both heat and mass recovery for continuous cooling production and better efficiency. Each generator is based on a plate heat exchanger concept using the activated carbon–ammonia pair. The model of conventional vapour compressor is a reciprocating compressor from Frigopol. The hybrid refrigeration performances are presented mainly for ice making and air conditioning applications (T_C = 40 °C, −5 °C < T_E < 20 °C). The exhaust temperature of the compressor (driving temperature for thermal compressor) varies from 90 °C to 250 °C. The results show a cooling production ranging from 4 kW to 12 kW with back-up mode (both cycles not operating simultaneously) and from 8 kW to 24 kW with complementary mode (both cycles operating simultaneously). The effective overall COP based on the total equivalent heat rate input varies from 0.24 to 0.76.     

Design and parametric investigation of an ejector in an air-conditioning system

This paper discusses the behavior of ammonia (R-717) through an ejector, operating in an air-conditioning system with a low temperature thermal source. For the detailed calculation of the proposed system a method has been developed, which employs analytical functions describing the thermodynamic properties of the ammonia. The proposed cycle has been compared with the Carnot cycle working at the same temperature levels. The influence of three major parameters: generator, condenser and evaporator temperature, on ejector efficiency and coefficient of performance is discussed. Also the maximum value of COP was estimated by correlation of the three temperatures for constant superheated temperature (100°C). The design conditions were generator temperature (76.11–79.57°C), condenser temperature (34–42°C) and evaporator temperature (4–12°C).     

Thermodynamic study of multistage absorption cycles using low‐temperature heat

The use of low‐temperature heat (between 50 and 90°C) is studied to drive absorption systems in two different applications: refrigeration and heat pump cycles. Double‐ and triple‐stage absorption systems are modelled and simulated, allowing a comparison between the absorbent–refrigerant solutions H₂O–NH₃, LiNO₃–NH₃ and NaSCN–NH₃. The results obtained for the double‐stage cycle show that in the refrigeration cycle the LiNO₃–NH₃ solution operates with a COP of 0.32, the H₂O–NH₃ pair with a COP of 0.29 and the NaSCN–NH₃ solution with a COP of 0.27, when it evaporates at ?15°C, condenses and absorbs refrigerant at 40°C and generates vapour at 90°C. The results are presented for double‐ and triple‐stage absorption systems with evaporation temperatures ranging between ?40 and 0°C and condensation temperatures ranging from 15°C to 45°C. The results obtained for the double‐stage heat pump cycle show that the LiNO₃–NH₃ solution reaches a COP of 1.32, the NaSCN–NH₃ pair a COP of 1.30 and the H₂O–NH₃ mixture a COP of 1.24, when it condenses and absorbs refrigerant at 50°C, evaporates at 0°C and generates vapour at 90°C. For the double‐ and triple‐stage cycles, the results are presented for evaporation temperatures ranging between 0 and 15°C. The minimum temperature required in the generators to operate the refrigeration and heat pump cycles are also presented. Copyright © 2002 John Wiley & Sons, Ltd.     

Thermodynamic analysis and performance optimization of organic rankine cycles for the conversion of low‐to‐moderate grade geothermal heat

The present study considers a thermodynamic analysis and performance optimization of geothermal power cycles. The proposed binary‐cycles operate with moderately low temperature and liquid‐dominated geothermal resources in the range of 110°C to 160°C, and cooling air at ambient conditions of 25°C and 101.3 kPa reference temperature and atmospheric pressure, respectively. A thermodynamic optimization process and an irreversibility analysis were performed to maximize the power output while minimizing the overall exergy destruction and improving the First‐law and Second‐law efficiencies of the cycle. Maximum net power output was observed to increase exponentially with the geothermal resource temperature to yield 16–49 kW per unit mass flow rate of the geothermal fluid for the non‐regenerative organic Rankine cycles (ORCs), as compared with 8–34 kW for the regenerative cycles. The cycle First‐law efficiency was determined in the range of 8–15% for the investigated geothermal binary power cycles. Maximum Second‐law efficiency of approximately 56% was achieved by the ORC with an internal heat exchanger. In addition, a performance analysis of selected pure organic fluids such as R123, R152a, isobutane and n‐pentane, with boiling points in the range of ?24°C to 36°C, was conducted under saturation temperature and subcritical pressure operating conditions of the turbine. Organic fluids with higher boiling point temperature, such as n‐pentane, were recommended for non‐regenerative cycles. The regenerative ORCs, however, require organic fluids with lower vapour specific heat capacity (i.e. isobutane) for an optimal operation of the binary‐cycle. Copyright © 2015 John Wiley & Sons, Ltd.     

Performance investigation of a solar water distiller integrated with a parabolic collector using fuzzy technique

A recent study of the design of solar distillation with solar radiation concentration was carried out by an independent device. Transformer oil was used as a fluid to transfer heat to the distilled basin. The design and operational variables are essential, such as distiller dimensions, concentration ratio, pressure, and temperature. A mathematical model was proposed to simulate the system for 2 July 2018 from 10 am to 4 pm  in the climatic conditions of the city of Kirkuk, Iraq. Fuzzy logic (FL) was used to select the affected parameters: water temperature (T_w), water pressure (P_w), glass temperature (T_g), and vapor pressure (P_g) which have a separated membership function that control the linguistic variables. The results showed that the best performance of the distiller is at T_w = 100°C, P_g = 10 000 Pa, T_g = 20°C, and P_w = 20 000 Pa, and concentration ratio of 30. This study used FL to analyze solar distiller performance and identify optimum temperature, pressure, and concentration ratio on the productivity of solar distiller.     

Study of a novel solar adsorption cooling system and a solar absorption cooling system with new CPC collectors

One two-phase thermo-syphon silica gel-water solar adsorption chiller and LiBr-H₂O absorption chiller with new medium CPC (Compound Parabolic Concentrator) solar collectors were investigated. The reliability of adsorption chiller can be improved, because there is only one vacuum valve in this innovative design. Medium temperature evacuated-tube CPC solar collectors were firstly utilized in the LiBr-H₂O air conditioning system. The former system was applied in north of China at Latitude 37.45° (Dezhou city, China), the latter system was applied at Latitude 36.65° (Jinan city, China). Experimental results showed that the adsorption chiller can be powered by 55 °C of hot water. The adsorption chiller can provide 15 °C of chilled water from 9:30 to 17:00, the average solar COP (COPs) of the system is 0.16. In the absorption cooling system, the efficiency of the medium temperature evacuated-tube CPC solar collector can reach 0.5 when the hot water temperature is 125 °C. The absorption chiller can provide 15 °C of chilled water from 11:00 to 15:30, and the average solar COPs of absorption system is 0.19.     

An ejector‐enhanced re‐liquefaction process (EERP) for liquid ethylene vessels

For liquid ethylene gas (LEG) vessels, developing high‐efficient re‐liquefaction plant to handle the continuously yielded boil‐off gas (BOG) could significantly improve its energy efficiency. In this study, an ejector enhanced re‐liquefaction process (EERP) for LEG vessels is proposed to improve the performance of the conventional re‐liquefaction process (CRP) with a cascaded two‐stage compression refrigeration cycle. In Aspen HYSYS, an ejector model was developed to analyse the performance of the proposed cycle system. The effects of the evaporating pressure of upper cycle p_{R0 '} and the intermediate pressures of upper and bottom cycles (p_R3 and p_E3) on the performances of both the CRP and EERP were studied. The results show that better performances can be reached with lower p_{R0 '} for the CRP and EERP. In order to achieve the best performances, the optimal p_R3 and p_E3 are, respectively, lifted to 510 kPa and 630 kPa by the EERP. When the proposed cycle system with the EERP is employed to re‐liquefy 3000 kg/h of ethylene BOG, its coefficient of performance (COP) and exergy efficiency can be improved by 2.95–5.31% and 2.70–4.86% over that of the cycle system with the CRP. Correspondingly, the EERP could reduce the total power consumption of 15.7–27.9 kW compared to the CRP. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermodynamic analysis of the CO2‐based Rankine cycle powered by solar energy

Using carbon dioxide as working fluid receives increasing interest since the Kyoto Protocol. In this paper, thermodynamic analysis was conducted for proposed CO₂‐based Rankine cycle powered by solar energy. It can be used to provide power output, refrigeration and hot water. Carbon dioxide is used as working fluid with supercritical state in solar collector. Theoretical analysis was carried out to investigate performances of the CO₂‐based Rankine cycle. The interest was focused on comparison of the performance with that of solar cell and those when using other fluids as working fluids. In addition, the performance and characteristics of the thermodynamic cycle are studied for different seasons. The obtained results show that using CO₂ as working fluid in the Rankine cycle owns maximal thermal efficiency when the working temperature is lower than 250.0°C. The power generation efficiency is about 8%, which is comparable with that of solar cells. But in addition to power generation, the CO₂‐based solar utilization system can also supply thermal energy. Copyright © 2007 John Wiley & Sons, Ltd.     

Screening of novel water/ionic liquid working fluids for absorption thermal energy storage in cooling systems

Absorption thermal energy storage (ATES) is significant for renewable/waste energy utilization in buildings. The ATES systems using ionic liquids (ILs) are explored to avoid crystallization and enhance the performance. Property model and cycle model have been established with verified accuracies. Based on the preliminary screening, seven ILs are found feasible to be ATES working fluids, while four ILs ([DMIM][DMP], [EMIM][Ac], [EMIM][DEP], and [EMIM][EtSO₄]) have been selected for detailed comparisons. The coefficient of performance (COP) and energy storage density (ESD) of the ATES using different H₂O/ILs are compared with H₂O/LiBr. Results show that the operating temperatures of LiBr are constrained by crystallization, limiting the COPs and ESDs under higher generation temperatures and lower condensation temperatures. With varying T_g, [DMIM][DMP] yields higher COPs with T_g above 100°C and [EMIM][Ac] yields comparable ESDs (67.7 vs 67.1 kWh/m³) with T_g around 120°C, as compared with LiBr. The maximum COP is 0.745 for [DMIM][DMP]. With varying T_c, [DMIM][DMP] yields higher COPs with T_c below 38°C and [EMIM][Ac] yields higher ESDs with T_c below 33°C, as compared with LiBr. The maximum ESD is 87.5 kWh/m³ for [EMIM][Ac]. With varying T_e, [DMIM][DMP] yields higher COPs with T_e above 8°C, as compared with LiBr. The maximum ESD of ILs is 104.0 kWh/m³ for [EMIM][EtSO₄]. Comparing with the volume-based ESDs, the differences between ILs and LiBr are smaller for the mass-based ESDs. This work can provide suggestions for the selection of novel working fluids for ATES for performance and reliability enhancement.     

Collector selection for solar ejector cooling system

The performance of a solar ejector cooling system is simulated using three different collectors: a conventional flat plate collector, a high efficiency flat plate collector and a vacuum-tube collector. It is shown that with the proper selection of the generating temperature an optimum COP can be achieved. The solar ejector cooling system using the single-glazed solar collector with selective surface and an enhanced air insulating layer can be most economical when operated at the optimum generating temperature of the ejector cooling machine. In this case, the solar system cost is around 1 USD per watt of cooling capacity for air conditioning applications.