Hybrid Refrigeration System Research Articles

Effect of adsorption kinetics on the performance of the vapor compression-adsorption hybrid cycle

The adsorption cooling system is considered as environmental-friendly technology that can be driven by low temperature heat source. We focus on adsorption-vapor compression hybrid refrigeration system which is one of the reasonable options to reduce the consumption of fossil fuels. In this system, the evaporator of adsorption cycle work as the evaporative subcooler for the refrigerant of vapor compression cycle. Performance predictions of the hybrid system require to solve unsteady state governing equations of adsorption cycle including the adsorption characteristics parameters. In our study, the performance of the hybrid system was analyzed by calculating the adsorption kinetics in the model. We have calculated in many conditions such as different adsorption and desorption time or heat medium mass flow rate ratio. The result showed that unsteady model could grasp the adsorption characteristics on system performance analysis. This system has a capacity to improve the vapor compression cycle performance as much as 10% by using 1kW waste heat depend on operating conditions.

Investigation on the Performance of a Solar Hybrid Refrigeration System Using Environmentally Friendly Fluids

In order to evaluate the performance of a hybrid compression / ejection refrigeration system using solar energy at low or medium temperature, a simulation model of its behavior based on those of its various components has been developed. It includes in particular for the ejector, a 1-D model of the "constant section mixing" type developed in optimal transition regime. The refrigerants tested are steam for the ejector loop and the R1234yf (replacing the R134a) for the mechanical compression loop. The behavior of the H2O vapor flowing in the ejector is considered that of the perfect gas. The properties of refrigerants are calculated using REFPROP® software, everywhere else. For a cooling capacity of 10 kW and air conditioning operating conditions, the model allows to determine the main parameters of the ejector and its entrainment ratio, the thermal and mechanical COP of the whole refrigeration system as well as the necessary surface of the solar collector. Furthermore, the influence of the temperature of the boiler, the condenser, the intercooler as well as that of the evaporator on the mechanical COP of the hybrid system and the solar collection surface in particular, were examined. The results highlight that the solar refrigeration system with hybrid cycle compression/ejection using the refrigerants H2O/R1234yf allows an increase of the mechanical COP higher than 50% compared to that of the conventional refrigeration system and thus constitutes an acceptable ecologically system that can compete with the latter.

Cooling Performance Analysis of the Lab-Scale Hybrid Oyster Refrigeration System

Compared with the waste-to-heat and electricity-based hybrid refrigeration system, the innovative lab-scale refrigeration system integrated with the DC and AC cooling units that able to use solar and electricity as energy resources. Previous studies found that temperature control and uniform temperature distribution in refrigeration systems are both critical factors reducing vibrio growth on raw oysters and saving energy consumption. Therefore, this refrigeration system also equipped a specially designed divider and was used to test various air circulation strategies to achieve uniform temperature distribution in six individual compartments. The objective is to investigate and evaluate the effects of air circulation strategies and operating conditions on the cooling performance, including temperature distribution, standard deviation of compartment temperatures, and cooling time using a factorial design method. Results indicated the maximum temperature difference between the compartments was 8.9 ± 2.0 °C, 6.7 ± 2.0 °C, and 4.8 ± 2.0 °C in the scenarios of no air circulation, natural air circulation, and combined natural and forced air circulation, respectively. The interaction of fan location and fan direction showed a significant effect on the compartment temperatures while there was no significant effect on cooling time. A circulation fan on the lower part of the 12-volt section with an air supply from the 12- to 110-volt section was determined as the optimal condition to achieve relatively uniform temperature distribution. Refrigeration system also achieved a cooling temperature of 7.2 °C within 150 min to meet regulations. To that end, the innovative hybrid oyster refrigeration system will benefit oyster industries, as well as the aquaculture farmers in terms of complying with regulations and energy savings.

Proposal and parametric study of solar absorption/dual compression hybrid refrigeration system for temperature and humidity independent control application

The solar absorption refrigeration technology plays a major role in the building energy saving and emission reduction. According to the concept of energy cascade utilization, this paper proposes a novel solar absorption/dual compression hybrid refrigeration (SADC-HR) system, which consists of solar-driven single effect absorption refrigeration (SSAR) subsystem and power-driven dual-source dual-compression refrigeration (PDCR) subsystem. An air-cooled compression refrigeration (ACR) cycle is integrated with the water-cooled compression refrigeration (WCR) cycle to make up the PDCR subsystem, so as to satisfy the all-weather space cooling/heating demand. The SADC-HR system achieves the cascade production and utilization of cold energy for the temperature and humidity independent control air conditioning system. The thermodynamic model of the SADC-HR system is built to evaluate the system performance and operating parameters, and the comparisons with two conventional systems are also discussed. The results indicate that there are optimum generating temperature of 70 °C and optimum evaporating temperature of 18 °C for the SSAR subsystem to obtain the lowest power consumption at low solar intensity of 450 W/m2. The SADC-HR system also exhibits better economic performance, and its solar collector area is respectively 55.79% and 34.75% lower than that of the conventional SSAR system and solar absorption-compression cascade refrigeration (SA-CCR) system at low solar intensity of 450 W/m2. In addition, the proposed system shows the better energy-saving performance as well as a smaller environmental impact, whose power consumption is reduced by 61.47% compared with the conventional SA-CCR system at solar intensity of 800 W/m2, and the present case study demonstrates that total seasonal electricity consumption in the SADC-HR system decreases a value of 25.32% which corresponds to a decline of 21580.66 kg of CO2 emission in comparison with the conventional ACR system.

Thermal and Mechanical Design for Refrigeration System of 10 MW Class HTS Wind Power Generator

A 10 MW class high temperature superconducting (HTS) wind power generator is being developed using REBCO wires for offshore installations. The REBCO coil operates at 35 K and is cooled via forced circulation of helium gas cooled though a heat exchanger in a rotating neon reservoir. Thermal and structural designs should be conducted to ensure that the structure can withstand mechanical stress created by the large torque from the 10 MW power, before building a cryogenic refrigeration system. This paper describes the design of supporting structures and the corresponding thermal characteristics of the HTS magnet. The supporting structure considers Lorentz force in the HTS magnet, fully coupled with an electromagnetic design result of the 10 MW class generator, under full load conditions. To estimate total heat loss, thermal radiation and heat loss at current leads are considered. A thermal analysis combined with cooling channels where the cold helium gas flows is performed to verify if the maximum temperature of the coil meets the design criteria. The analysis and design results are applied to develop a novel “neon-helium hybrid refrigeration system” for the 10 MW HTS wind power generator.

Prospect of solar-driven ejector-compression hybrid refrigeration system with low GWP refrigerants in summer of Guangzhou and Beijing

Abstract In this paper, the prospect of low-GWP refrigerants used in solar-driven ejector-compression hybrid refrigeration system was analyzed and evaluated based on the solar radiation data in summer of Beijing and Guangzhou. Prominent environmental friendly alternative refrigerants, including HCFO-1233zd(E), HFO-1336mzz(Z), HFO-1234ze(Z), HCFO-1224yd(Z) and HC-600 were chosen as the working fluids to address the environmental concerns, while HFC-245fa was used as the baseline refrigerant. The hybrid refrigeration system composed of an ejector refrigeration system as the upper stage and a vapor compression system as the bottom stage, respectively. The results indicated that the system with HFO-1234ze(Z) showed the highest COP. HFO-1234ze(Z) was followed by HCFO-1233zd(E) and HC-600, and all of them showed higher COP than that of HFC-245fa. The system with HC-600 needed more electric energy than any other systems, while HFO-1336mzz(Z) consumed the lowest electric power. Meanwhile, the performances of HFO-1234ze(Z) and HFC-245fa systems were further compared. It was found that for both working fluids, the heat load of the condenser (Qe,c), total electric energy consumption (We) and electric energy of compressor (Wcom) in August were the highest in Beijing, while in Guangzhou, the highest of them was achieved in September. It was also suggested that the solar radiation had no influence on the relative magnitude of the Qe,c, We and Wcom between HFO-1234ze(Z) and HFC-245fa systems. The Qe,c, We and Wcom of the system with HFO-1234ze(Z) were higher than those of HFC-245fa by 0.8%, 4.44%, and 3.55%, respectively.

Prospect Evaluation of Low-GWP Refrigerants R1233zd(E) and R1336mzz(Z) Used in Solar-Driven Ejector-Vapor Compression Hybrid Refrigeration System

In this paper, the entrainment ratio, pump work, heat loads of heat exchangers and COPthermal were theoretically evaluated for a solar-driven ejector-vapor compression hybrid refrigeration system with R1233zd(E) and R1336mzz(Z) as the working fluids. The evaluation of the utilization potentials of R1233zd(E) and R1336mzz(Z) was presented by comparing the system performance with that of R245fa, a commonly used refrigerant in the ejector system. The results indicated that the systems with R1233zd(E) and R1336mzz(Z) had a higher entrainment ratio and lower pump work. The pump works when using R1233zd(E) and R1336mzz(Z) can be up to 14.59% and 38.05% lower than those of R245fa, respectively. Meanwhile, the system showed the highest COPthermal utilizing R1233zd(E) followed by that of R245fa, with the R1336mzz(Z) system having the lowest value. The differences between R1233zd(E) and R1336mzz(Z) systems, R1233zd(E) and R245fa systems were 4.33% and 2.0%, respectively. This paper was expected to provide a good reference for the utilizing prospect of R1233zd(E) and R1336mzz(Z) in ejector refrigeration systems.

Performance analysis and multi-objective optimization of cooling tower assisted vapor compression-absorption cascaded and hybrid refrigeration systems

ABSTRACTPresent work compares and optimizes the performance of cooling tower assisted cascaded and hybrid configurations of vapor compression-absorption integrated refrigeration system. Both the systems are designed to estimate their performance, size, and cost for the cooling capacity of 100 kW. Further, optimization strategies based on the Coefficient of Performance (COP), operational cost, and investment cost are followed to make the systems competitive. Four optimization cases, i.e. the COP single-objective, the total operational cost single-objective, the total investment cost single-objective, and the multi-objective optimization are performed and compared for both the systems. Comparative study of cascaded refrigeration system (CRS) with hybrid refrigeration system (HRS) shows that the COP and second law efficiency of CRS is 82.1% and 25.0%, respectively more as compared to HRS; whereas, the CO2 penalty cost of CRS is almost half of HRS. The efficient energy utilization and lower CO2 emission yields 46.1% lower annual operational cost in HRS as compared to CRS. Further, the economic analysis predicts that the investment cost of CRS is 10% less than that of HRS for same cooling capacity. Therefore, based on combined energy, exergy, environmental, and economic (4E) analyses, it can be concluded that the performance of CRS is better as compared to HRS.

Thermodynamic analysis of ejector-assisted vapour compression–absorption hybrid refrigeration system

ABSTRACT The vapour compression–absorption hybrid refrigeration system (VCAHRS) is a potential alternative refrigeration technology as it economises the use of energy resources. The main issues observed with VCAHRS are low overall COP and large size of system which is mainly due to the poor performance of absorption section. Absorption section, while assisted by an ejector, can improve the overall performance of VCAHRS. It is shown that at low generator temperatures, the ejector-assisted absorption section provides better performance than the conventional absorption system adapted in VCAHRS. Simulation results show that the overall COP of VCAHRS is improved by 22.6%, whereas the COP improvement of 25.2% is observed in the absorption section. The total irreversibility of the system is reduced by 38.8% using ejector at optimum generator temperature which is found to be 92.1°C while varying it from 117.9°C. Therefore, ejector-assisted VCAHRS also permits the utilisation of low temperature heat source.

Performance comparison of two absorption-compression hybrid refrigeration systems using R1234yf/ionic liquid as working pair

R1234yf (2,3,3,3-tetrafluoroprop-1-ene)/ionic liquid is a kind of environment-friendly working pair, which can overcome the disadvantages of H2O/LiBr and NH3/H2O. In this work, three new working pairs R1234yf/[HMIM][TfO], R1234yf/[HMIM][PF6], R1234yf/[HMIM][BF4] were proposed and new solubility data for them were determined. Two new absorption-compression hybrid refrigeration systems were proposed to improve the cooling performances of the single-effect absorption refrigeration system using R1234yf/[HMIM][TfO], R1234yf/[HMIM][PF6] and R1234yf/[HMIM][BF4] as working pair. The effects of compressor position, compression ratio (r), generation temperature (Tg), evaporation temperature (Te), condensation temperature (Tc) and absorption temperature (Ta) on the coefficient of performance (COP) and circulation ratio (f) were analyzed. Comparison result shows that the two systems can effectively improve the cooling performance of the single-effect absorption refrigeration system including increasing COP, reducing the heat load of condenser and f, and enlarge the operation range of Tg, Ta, and Te. Putting compressor between evaporator and absorber is a better choice than putting it between generator and condenser. R1234yf/[HMIM][TfO] shows better cooling performance than R1234yf/[HMIM][PF6] and R1234yf/[HMIM][BF4] due to its favorable thermophysical properties.

Hybrid electric vehicle absorption-compression refrigeration system

The air-conditioning system of electric vehicles shortens the driving mileage of the car. Therefore, a set of absorption-compression hybrid refrigeration system for hybrid electric vehicle are designed. The system consists of power system, absorption refrigeration cycle and compression refrigeration cycle. By using the waste heat of micro gas turbine to drive the absorption refrigeration subsystem, the power consumption of the compressor driven by battery power is reduced, as well. The feasibility of the system is discussed through the thermodynamic cycle calculation. The results show that, a bus air-conditioning with cooling load of 30 kW, the waste heat emitted by a micro gas turbine with a power of 35 kW drives an absorption refrigeration cycle, which can provide about 15 kW of cooling capacity, and the remaining part needs to be compensated by the compression refrigeration cycle, which consumes about 6.71 kW of compressor power. At the same time, compared with the absorption-compression combined refrigeration and electric compression refrigeration, the energy efficiency is improved by about 37.1 %.

Conventional and advanced exergy analysis of parallel and series compression-ejection hybrid refrigeration system for a household refrigerator with R290

Both conventional and advanced exergy analysis methods were adopted to compare parallel and series compression-ejection hybrid refrigeration system for a two-temperature R290 refrigerator. The calculation was performed through Matlab and CoolProp. The results over typical design conditions showed that the exergy efficiency of the series system is 5.17% higher than the parallel system, and the exergy destructions of the compressor (30.59% for parallel and 31.22% for series) and the ejector (19.36% for parallel and 22.65% for series) are the biggest of the total system. Results from advanced exergy analysis showed that the compressor possesses highest improvement priority as its avoidable exergy destruction rate is the biggest, 42.76% of the total for parallel system and 41.28% for series system. The endogenous avoidable exergy destruction rates of the compressor and the ejector are larger than their exogenous parts in both systems, indicating it is most important to improve their own efficiency. However, the condenser’s endogenous avoidable exergy destruction rates are smaller than their exogenous part, so it is more effective by improving other system components rather than itself. The influence of the interactions among the components on the system performance was also evaluated based on their mexogenous exergy destruction.

Process development and exergy analysis of a novel hybrid fuel cell-absorption refrigeration system utilizing nanofluid as the absorbent liquid

A hybrid system including high-temperature polymer fuel cell with capacity of 5 kW along with fuel processing unit for producing rich hydrogen from natural gas integrated by a 3 kW absorption chiller has been developed. The waste heat of flue gas from the burners is utilized in the ammonia-water absorption chiller for refrigerating purposes. The hybrid refrigeration system is simulated by Aspen HYSYS software in a steady state condition. After defining the properties of nanoparticles in HYSYS software, the water-based nanofluids are employed as absorbent liquid for increasing of COP in the refrigeration system, and their effects have been evaluated on overall system performance. The electrochemical model of the fuel cell as well as the main parameters of refrigeration system have been validated with experimental results and similar works. Electrical efficiency and overall efficiency of the hybrid system are equal to 36% and 77.3%, respectively. The overall efficiency in the presence of silver nanofluid can be increased up to 81%. Exergy analysis has been conducted for the hybrid system, and the obtained exergy efficiency of the system is equal to 29%. Sensitivity analysis has been employed for evaluating of significant parameters on the hybrid system performance.

Definition and performance simulations of a novel solar-driven hybrid absorption-thermochemical refrigeration system

This paper proposes a novel hybrid refrigeration system with energy storage, driven by low-grade solar heat and consisting of a single-stage absorption cycle coupled with a thermochemical process by sharing the same condenser, evaporator and refrigerant fluid. A first screening of ammonia-based working pairs for evaporation temperatures of −10 °C, condensation temperatures of 30 °C and heat source temperatures of 80 °C reveals LiNO3 as suitable sorbent salt for the absorption subsystem, and BaCl2, PbBr2, SrCl2, LiCl, NH4Br and SnCl2 as candidate reactive salts in the thermochemical subsystem. The subsequent parametric study indicates that the absorption subsystem with NH3/LiNO3 reaches close-to-maximum COP at the indicated conditions, and the thermochemical subsystem delivers its highest COP with the NH3/BaCl2 pair. Then, the power-storage and performance-storage relationships of the thermochemical subsystem are analyzed for the NH3/BaCl2 pair with respect to variations in operating conditions and several implementation parameters of the reactive composite. Finally, the performance of the hybrid system with the (NH3/LiNO3 + NH3/BaCl2) pair combination is compared to its subsystems against a variable demand profile calculated from climatic data of July in Barcelona, Spain. A novel indicator is defined to assess demand coverage: the Coefficient of Satisfaction of Demand (CSD). Depending on solar collector field area and amount of refrigerant storable by the thermochemical subsystem, the hybrid system reaches up to 24% higher CSD than the reference system (a solar single-stage absorption refrigerator with no storage), and at least 14% higher COP than the thermochemical process.

Multi-objective assessment, optimization and application of a grid-connected combined cooling, heating and power system with compressed air energy storage and hybrid refrigeration

As one of attractive technology of energy conservation, combined cooling, heating and power (CCHP) system has brought about widespread attention. However, the variability of users demand has limited the application of CCHP system. To ensure stable and efficient operation, the compressed air energy storage is considered to be integrated with CCHP system. A grid-connected CCHP system with compressed air energy storage (CAES) and hybrid refrigeration is proposed in this paper. The power from grid is stored in CAES at off-peak time and released at on-peak time. The hybrid refrigeration system including LiBr absorption chiller and electric compression refrigerator provides cooling load to users. A multi-objective assessment and optimization synthetically considering energy, economy and environment are presented. The multi-objective indicator used as objective function to optimize each component capacity of the proposed CCHP system. A sensitive analysis of key parameters and performance comparison with conventional CCHP system have been carried out. The results shows that when the capacity of gas turbine is 691 kW, the comprehensive performance of the proposed CCHP system is the optimal performance. The power price, natural gas price, compression ratio and turbine inlet temperature of CAES have great influence on the performance of the proposed CCHP system. Meanwhile, the multi-objective indicator’s value of the proposed CCHP system is more than conventional CCHP system 4.85%.

Energy savings of hybrid dew-point evaporative cooler and micro-channel separated heat pipe cooling systems for computer data centers

The world has entered the Age of Big Data with large data centers consuming large amounts of energy. 30%–50% of the energy delivered to a typical data center is consumed by the space cooling system. Dew-point evaporative coolers and heat pipes both utilizing natural cold resources can significantly reduce these refrigeration costs. This paper presents two hybrid cooling systems combining dew-point evaporative coolers with heat pipes for computing and data center cooling systems. The energy-saving potentials of two these hybrid cooling systems were analysed through calculations with comparisons with a traditional vapour compression refrigeration system. The results show that the average annual coefficients of performance (COP) of the ideal hybrid refrigeration systems are 33 and 34 which leads to annual energy savings of nearly 90% compared with vapour compression refrigeration.

Advanced Analysis of Dew Point Control Unit of Hybrid Refrigeration Systems in Gas Refineries

In this paper, an advanced analysis of a novel hybrid compression-absorption refrigeration system (HCARS) for natural gas dew point control unit in a gas refinery is presented. This unit separates the heavy hydrocarbon molecules in the natural gas, which is traditionally carried out by natural gas cooling in a compression refrigeration cycle (CRS). The power input required for the refrigeration cycle compressors is usually provided by gas turbines. The low efficiency of gas turbines and the excessive power required for running the CRS compressors have made it crucial to investigate different means to decrease the energy consumption of this cooling system. The waste heat of gas turbines flue gas can be recovered and utilized as the heating source for running an absorption refrigeration system (ARS) to provide part of the needed cooling load; hence, a hybrid compression absorption refrigeration system (HCARS) is launched. In this work, the application of HCARS is extended to the Fajr-e-Jam gas refinery currently operating with a CRS, and an advanced exergetic analysis of the proposed ARS is performed to further improve the proposed system. The effect of different variables on the performance of the proposed HCARS is also inspected. The proposed system and these analyses are novel for the gas refinery dew point control unit. Real CRS operational data are utilized in all the investigations, and proper means are presented for the validation of the simulation results. The proposed system resulted in 63% additional cooling capacity of the HCARS (12550 KW) in comparison to the current CRS (7670 kW) for the equal natural gas consumption, which overall saves about 50000 SCMD of natural gas. Based on the exergy analysis of all the equipment, the exergy efficiency of the proposed ARS is 0.155. In addition, the parametric study of the effects of the gas turbine flue gas exit temperature and flow rate, ambient temperature, partial load operation of CRS, absorption solution flow rate, and concentration on the HCARS performance is carried out. These studies should provide the information needed for operating the proposed system in different situations.

Thermo-economic assessment and application of CCHP system with dehumidification and hybrid refrigeration

Combined cooling, heating and power (CCHP) systems have widely theoretical researched and practical applied to solve the energy and environment problems. The schemes of CCHP systems are important to select, which can best satisfy users demand with high thermal economy and low pollutant emission. In this paper, a novel scheme of CCHP system with dehumidification and hybrid refrigeration is proposed, where an internal combustion engine (ICE) is utilized as a prime mover. The absorption dehumidifier is driven by jacket water of ICE to provide dehumidification, and hybrid refrigeration system is consisted of absorption chiller and electric compression refrigerator. A thermo-economic model of the CCHP system is established, and a comprehensive evaluation criteria is proposed as objective function. The analytic hierarchy process and the constrained nonlinear programming solution are employed to optimize design and operation strategy of the ICE-CCHP system. This research discuss its application in a case: the CCHP system apply to following the electric load (FEL), and the optimum equipment capacity of the CCHP system is obtained. Furthermore, the sensitivity analysis is carried out to assess effects on performance of the CCHP system.

Performance analysis of solar absorption-subcooled compression hybrid refrigeration system in subtropical city

Solar absorption-subcooled compression hybrid refrigeration system is a new type of efficient and economical solar refrigeration device which always meets the demand of cooling load with the change of solar irradiance. The performance of the hybrid system is higher due to the improvement of evaporator temperature of absorption subsystem. But simultaneously, the variation of working process as well as performance is complicated since the absorption and compression subsystems are coupled strongly. Based on the measured meteorological data of Guangzhou, a subtropical city in south China, a corresponding parametric model has been developed for the hybrid refrigeration system, and a program written by Fortran has been used to analyze the performance of the hybrid system under different external conditions. As the condensation temperature ranges from 38°C to 50°C, the working time fraction of the absorption subsystem increases from 75% to 85%. Besides, the energy saving fraction also increases from 5.31% to 6.02%. The average COP of the absorption subsystem is improved from 0.366 to 0.407. However, when the temperature of the absorption increases from 36°C to 48°C, the average COP of hybrid system decreases from 2.703 to 2.312. Moreover, the working time fraction of the absorption subsystem decreases from 80% to 71.7%. The energy saving fraction falls from 5.67% to 5.08%. In addition, when the evaporate temperature increases from 4°C to 14°C, the average COP of the absorption subsystem decreases from 0.384 to 0.365. The work of the compressor decreases from 48.2 kW to 32.8 kW and the corresponding average COP of the absorption subsystem is improved from 2.591 to 3.082.

Performance Comparison between an Absorption-compression Hybrid Refrigeration System and a Double-effect Absorption Refrigeration Sys-tem

Conventional absorption refrigeration systems (ARSs), which are mainly driven by heat, have a competitive primary energy efficiency (PEE) compared with chillers driven by electricity. In the typical ARS, a large quantity of high-temperature heat is supplied into the generator, while a substantial amount of low-temperature heat is rejected to the environment from the condenser, it’s a huge waste. In order to decrease the input heat for generator and enhance the performance of conventional ARS, a kind of absorption-compression hybrid refrigeration system recovering condensation heat for generation (RCHG-ARS) was ever proposed. In the present study, the models of both RCHG-ARS and double-effect absorption refrigeration system (DEARS) are established, and the effects of different parameters on them are simulated and compared with each other. As a conclusion, the PEE of RCHG-ARS can be 29.0% higher than that of DEARS, and RCHG-ARS has a wider working conditions than DEARS due to the existence of the compressor.