Combined Refrigeration Cycle Research Articles

Product Refrigeration Load Analysis On Contact Plate Freezer On Compressor Performance At PT. Trimitra Makmur, Tarakan, North Kalimantan

Contact plate freezer (CPF) is a cooling machine unit for freezing products which of course will maintain product freshness. In Order to runs smoothly, one thing that must be considered of the cooling system is the cooling load on the freezer contact plate. The cooling load is the amount of heat absorbed per unit time. The refrigeration cycle at PT. Trimitra Makmur uses a combined refrigeration cycle (multi-stage cycle), uses two cycles of vapor compression using two single-stage compressors. The two compressors used have the same power of 55.92 kW. The cooling load on the contact plate freezer consists of product heat load, water heat load, internal heat load, and transmission heat load. In The contact plate freezer, infiltration or heat load from the outside air are not counted because during production the contact plate freezer door is closed tightly so that the air exchange value is very small and can be neglected. In this study, the average total load on contact plate freezer 1 was 23.07079 kW, so that the average total load on the three contact plate freezers at PT. Trimitra Makmur is 69.21237 kW. The results of data collection and calculations show that the COP (Coefficient of Performance) value for the high-stage cycle is 4.33, so that the high-stage compressor power used is 1/4.33 of the cooling capacity of the contact plate freezer. Whereas in the booster cycle, a COP of 6.49 was obtained, so that the booster compressor power used was 1/6.49 of the cooling capacity of the contact plate freezer. 

Enhancing the performance of a CO2 combined refrigeration and power (CRP) cycle driven by engine exhaust gas by using heat exchangers in optimized locations

Carbon Dioxide (CO2) has proven its efficiency as a working medium for power and cooling productions in vehicles and refrigerated trucks driven by engine exhaust gases. The main drawbacks of this system are the high/low critical pressure/temperature of the CO2 which leads to high compressor power and low efficiency. In the present paper two modifications by insertion of two heat exchangers in bottom and top CO2 compound cycles driven by engine exhaust gas are proposed to overcome on these drawbacks. Energy and exergy analysis are used to evaluate and compare their performances with the basic system. The results show that (i) the feasibility of using the proposed systems was justified and has proven potentials of energy and fuel consumption saving compared to traditional engine + stand-alone refrigerator, (ii) proposed modifications on the basic system (System I) by incorporated heat exchangers (System II and System III) has proven its potential for higher energy efficiency and refrigeration capacity and can recover about 18.33%, 20.38% and 19.22% of the energy of the exhaust gases for driven the compound CO2 cycle, (iii) parametric, comparison and optimization studies, showed that the proposed system (system II) has the highest refrigeration capacity, energy efficiency and fuel consumption cost saving with optimal values of 20.4%, 0.1819 kg/kWh, 7.1%, respectively.

Improving the Engine Efficiency Using a New Combined Refrigeration Cycle for Low-Temperature Heat Source (Waste Heat Recovery)

Passenger and commercial internal combustion engines have relatively large dissipated thermal energy sources that can be used for initiating thermodynamic refrigeration cycles at low temperatures while improving engine efficiency. Researchers have focused on combined power-refrigeration cycles in past studies. This paper presents the operation and performance of a new combined refrigeration system driven by waste heat recovery within the internal combustion engines. For this purpose, the effects of several parameters on the performance of the cycle are examined. Results show that an increase in the engine water temperature, exhaust gas temperature, part-load ratio (PLR), generator temperature, as well as adsorption evaporator temperature had a positive effect on the performance of the cycle. However, the rise in condenser temperature of the adsorption cooling system leads to bad performance. Also, the results indicate that the application of the adsorption refrigeration cycle in the combined cooling cycle, along with the increase in the refrigeration cycle performance by up to 65%, also improves the efficiency of the internal combustion engine.

Energy and exergy analysis of a novel ejector-absorption combined refrigeration cycle using natural refrigerants

Energy and exergy analysis of a novel ejector-absorption combined refrigeration cycle using natural refrigerants

Energy and exergy analysis of a novel ejector-absorption combined refrigeration cycle using natural refrigerants

Energy and exergy analysis of a novel ejector-absorption combined refrigeration cycle using natural refrigerants

Thermodynamic performance study on a novel absorption‐ compression cascade refrigeration activated by an internal combustion engine

A novel cascade refrigeration system was presented and studied, which could supply low-temperature cooling capacity for fishing boats and refrigerated trucks at a low energy cost. The cycle was cascaded by a high-temperature stage of absorption-compression combined refrigeration cycle and a low-temperature stage of the CO2 subcritical compression refrigeration cycle. The presented cascade cycle could not only utilize adequately the waste heat of the engine but also utilize adequately the excellent performance of the CO2 subcritical cycle operating on a low-temperature working condition. The high-temperature stage cycle had three solution modes, which could bring about an effective waste heat utilization of the engine and effectively decrease power consumption. Based on the proposed cascade cycle, a fundamental thermodynamic model was constructed and solved under different operating modes. The obtained results indicated that the performance coefficient of the cascade refrigeration system could reach 3.26, which was significantly higher than 2.1 of the traditional two-stage compression cascade refrigeration system. Moreover, the exergetic efficiency of the cascade refrigeration system could reach about 0.52 under the conditions of evaporating at −35°C and condensing at 40°C. The research findings can provide an effective solution for the utilization of waste heat in refrigerated trucks and fishing boats. Novelty Statement The novelty of this work lied in that a novel absorption-compression cascade refrigeration cycle was proposed, which can supply low temperature cooling capacity for refrigerant trucks and fisher vessels by extremely utilizing the waste heat exhaust gases and jacket water from internal combustion engine of vehicles or ships.

Multi-mode analysis of a CO2-based combined refrigeration and power cycle for engine waste heat recovery

To realize the adjustable allocation of refrigeration and power in a combined refrigeration and power cycle, this study proposes a multi-mode cycle using CO2 as the working fluid. A refrigerated truck is selected as the research objective, the refrigeration demand and power demands of which vary frequently with different transportation conditions. The proposed system is driven by the exhaust gas of the main diesel engine and can replace the original refrigerator and related small-scale diesel engine. Three operating modes can be realized for different energy demands: full refrigeration output, combined refrigeration and power output, and full power output. The results indicate that the proposed system exhibits considerable potential for energy saving and diversified energy supply capacity. Following optimization of the configuration and parameters, the proposed energy solution (engine + proposed system) under the mode of combined refrigeration and power output can achieve a 2.9% fuel saving and 4.8% power increase simultaneously versus the original energy solution (engine + refrigerator) under refrigeration condition, 3.4% fuel saving and 1.6% power increase simultaneously under freezing conditions. The fuel economy is correspondingly improved 7.4% and 4.9%. Moreover, the proposed method can provide greater refrigeration and power capacities under the full refrigeration output and full power output modes.

Thermodynamic performance assessment of solar-based combined power and absorption refrigeration cycle

Concentrated solar power technology has gained rapid pace in the area of sustainable energy. In recent years concentrated solar power is being appreciated worldwide as they effectively convert available solar energy to its true potential resultant energy. In this context, the principal objective of this research is to develop a model driven on solar thermal integrated with a cogeneration cycle. The effect on power generation was noted by varying parameters such as DNI, turbine inlet pressure, mass flow rate of molten salt and turbine entrance temperature was ascertained on energy and exergy efficiencies of cogenerated driven cycle. From the results it was observed, a gradual growth at turbine entry pressure ranging between 180 bar to 220 bar causes an eventual rise in first law related efficiency and exergy related efficiency of Rankine and cogeneration cycle from (31.115% to 31.44%; 42.05% to 42.56%) and (42.03% to 42.14%; 56.04% to 56.55%).

A novel absorption–compression combined refrigeration cycle activated by engine waste heat

Absorption refrigeration is an admirable means of refrigeration to use waste heat and decrease electricity and power consumption in air conditioning and refrigeration. A novel absorption–compression combined refrigeration cycle, which is driven by waste heat from the internal combustion engine of overload vehicles, vessels, or diesel generating sets, is proposed and investigated in this study. The high-pressure generator and the low-pressure generator are activated by exhaust gases and coolant liquids from the engine, respectively. Correspondingly, the high- and low-pressure compressors and solution pump are driven by the output power from the engine. The proposed refrigeration cycle can use the waste heat of the engine to the greatest extent and decrease engine power consumption. First, the thermodynamic circle model of the combined system was constructed. Then, the model was solved under different control strategies and operating modes. Theoretical calculation results show that the proposed combined cycle had a higher performance coefficient compared with compression refrigeration. The calculation results can be used as a reliable design, control strategy, and optimization tool for the combined refrigeration cycle future utilization in overload vehicles, vessels, or diesel generating sets.

Theoretical research of the performance of a novel enhanced transcritical CO2 refrigeration cycle for power and cold generation

Three different refrigeration cycles, namely the vapor compression cycle, the combined refrigeration cycle and the new combined refrigeration cycle for power and cold, are investigated. The principles of mass and energy conservation are applied to every component of the systems, and the resulted linear system of equations was numerically solved. It was found that the new proposed cycle had a lower optimum gas cooler pressure than other refrigeration cycles, and this would enhance the lifetime and safety of the system. Besides, it was found that the coefficient of performance of the new cycle is higher than that of the vapor compression and combined refrigeration cycles 110% and 50%, respectively. The exergy efficiency was approximately 78% and 58% higher than that of the vapor and combined refrigeration cycles, respectively. Furthermore, the exergoeconomic results of the new cycle showed that the total unit cost was lower by 16.6% and 13% than that for the vapor compression and combined refrigeration cycles, respectively.

Exergoeconomic optimisation of basic and regenerative triple-evaporator combined power and refrigeration cycles

This paper deals with reconstruction of conventional combined cooling and power (CCCP) cycle for producing simultaneous power and cooling outputs for triple applications of freezing, refrigeration and air-conditioning. The proposed systems are integrated from organic Rankine cycles (ORCs) and an ejector refrigeration cycle (ERC). Single- and multi-objective optimisations of the proposed systems are conducted from energy, exergy and exergoeconomic viewpoints, using genetic algorithm (GA). The results of optimisation revealed that the thermal efficiency of the basic triple-evaporator CCP (B-TECCP) and regenerative TECCP (R-TECCP) systems can be improved by 7.48% and 6.23%, respectively, whereas the exergy efficiency of the proposed systems is enhanced by 10.83% and 6.84%, respectively. In addition, the sum unit cost of product of the system is also decreased by 11.88% and 15.19% for B-TECCP and R-TECCP systems, respectively, through this optimisation mode. At last, a comprehensive parametric study is performed to give more information from operating conditions of the proposed systems for designers.

First and second law analyses of syngas fueled novel combined power and double-ejector refrigeration cycle

ABSTRACTThe proposed work pertains to the development of a power and refrigeration cycle which combines the Rankine cycle and the double-ejector refrigeration cycle. The resulting cycle would be driven by syngas/waste heats which are available at the exit of steam turbines and heat recovery steam generators, and this cycle will produce power as well as refrigeration. Observations show the increase in first and second law efficiencies of 6.3 and 3.15% by employment of ejectors when coupled to a combined power cycle. The results clearly reveal that thermodynamic investigation based on the first law analysis is inadequate and hence more meaningful evaluation needs to be included in the second law analysis.

Energy and exergy analyses of a novel combined heating, power and absorption-ejector refrigeration cycle driven by biomass fuel

In this paper, a new combined power, heating and refrigeration system is proposed, which combines the ammonia-water power/refrigeration system and steam ejector refrigeration system (SERS). This system was driven by biomass fuels and can produce both power and refrigeration simultaneously, besides according to the temperature of inlet streams into absorbers and rate of heat losses, these heat losses are used as floor heating. Moreover, high grade heat source is used in SERS; therefore, the entrainment ratio and efficiency of system are increased. The results show that the turbine inlet ammonia-water concentration, turbine outlet mass flow rate and turbine efficiency have effects on the turbine power output, refrigeration output, efficiency and exergy destruction in each component in the combined cycle.

Adapting Temperate Crops to Tropical Lowland through Solar Thermal Chilled Water Soil Cooling Process

The availability of most temperate crops is a function of changing season. Thus, their insufficient global supply and consequent seasonal do cause increase in prices. The effect is more pronounced in the tropical countries that too depend on importation of these crops because of unfavorable soil condition to cultivate them (due to high soil temperature). Growing these crops in the tropics requires soil temperature to be as low as it is in the temperate climate. Soil cooling with chilled water from the combined organic rankine and absorption refrigeration cycles presented in this paper aims at utilization of virtutl “free” solar thermal energy as input to run combined organic rankine and absorption refrigeration plant and producing chilled water as output for soil cooling process. The technical feasibility is established based on the overall value of coefficient of performance (COP) and the estimated area of solar collector per unit cooling load while the economic viability is established based on capital and operating costs to be incurred per unit cooling load.

Exergoeconomic evaluation and optimisation of a novel combined power and absorption-ejector refrigeration cycle driven by natural gas

This study deals with exergoeconomic analysis of a combined power and refrigeration system. Actually, in the presented cycle, the ammonia-water power/refrigeration system and the steam ejector refrigeration system (SERS) are combined. This system has the capability to produce refrigeration in diverse temperatures and quantities. It is worth noting that, the high level energy source is used to produce refrigeration in SERS due to which, the proper refrigeration capacity has been obtained. Moreover, according to exergoeconomic point of view, the exergy cost balance for each component is considered, so the rate of exergy cost generation within the system is determined. The sensitivity analysis is done to investigate the effect of changes effective parameters of system on the product cost rate. Finally, the optimisation process is carried out by minimising the investment cost of equipment and cost of exergy destruction.

Performance optimization of irreversible combined Carnot refrigerator based on ecological criterion

This work presents a computational model based on exergy analysis for refrigeration cycles by taking the profit finite-time ecological optimization criterion as the objective. Firstly we investigate a generalized irreversible single refrigeration cycle with losses of heat leakage, internal irreversibility and external irreversibility, using this criterion. Then, we apply this study to a two-stage generalized irreversible combined refrigeration cycle. The optimal coefficient of performance (COP) and corresponding ecological function (E) of the combined cycle with respect to the two combined cycle design parameters (β1 and β2) are analyzed. This analysis identifies lower and upper bounds to the maximum ecological function and corresponding COP of the combined cycle. These results were compared with those of the single cycle. Finally we establish the optimal COP and maximum ecological function rational regions that define the design parameter limits of performed combined refrigeration cycles.

Combined Cycle for Power Generation and Refrigeration Using Low Temperature Heat Sources

A combined refrigeration and power cycle, which uses ammonia-water as the working fluid, is proposed by combining Rankine and vapour absorption cycles with an advantage of varying refrigeration capacity to power output ratio. The study investigates the usage of low temperature heat sources for the cycle operation. Results of parametric analysis are presented, which show the scope for optimization. Results of thermodynamic optimization of the cycle for second law efficiency performed using genetic algorithm for different ambient temperatures are also presented. The cycle shows good potential for obtaining refrigeration and power generation.

A novel ejector-absorption combined refrigeration cycle

This paper presents a novel ejector-absorption combined refrigeration cycle. When the temperature of the heat source is high enough, this cycle will work as a double-effect cycle. If the temperature of the heat source is lower than required temperature of heat source used to drive conventional double-effect absorption refrigeration cycle but much higher than required temperature of heat source used to drive conventional single-effect absorption refrigeration cycle, the COP of new cycle will also be higher than that of conventional single-effect absorption refrigeration cycle. Simulation results show that the COP of the cycle is 30% higher than that of the conventional single-effect absorption refrigeration cycle at some working conditions even in the later case.

Profit rate performance optimization for a generalized irreversible combined refrigeration cycle

Finite-time exergoeconomic performance of a Newtonian heat transfer law system generalized irreversible combined refrigeration cycle model with finite-rate heat transfer, heat leakage and internal irreversibility is presented in this paper. The operation of the generalized irreversible combined refrigeration cycle is viewed as a production process with exergy as its output. The performance optimization of the cycle is performed by taking profit as the objective. The optimal profit rate, optimal COP (coefficient of performance), as well as the relation between the optimal profit rate and COP of the cycle are derived. The focus of this paper is to obtain the compromise optimization between economics (profit rate) and the energy utilization factor (COP) for the cycle, by searching the optimum COP at maximum profit rate, which is termed as the finite time exergoeconomic performance bound. Moreover, the effects of various factors, including heat leakage, internal irreversibility and the price ratio, on the profit rate performance of the cycle are analysed by detailed numerical examples.

Thermodynamic analysis of load-leveling hyper energy converting and utilization system

Abstract Load-leveling hyper energy converting and utilization system (LHECUS) is a hybrid cycle which utilizes ammonia–water mixture as the working fluid in a combined power generation and refrigeration cycle. The power generation cycle functions as a Kalina cycle and an absorption refrigeration cycle is combined with it as a bottoming cycle. LHECUS is designed to utilize the waste heat from industry to produce cooling and power simultaneously. The refrigeration effect can be either transported to end-use sectors by means of a solution transportation absorption chiller (STA) as solution concentration difference or stored for demand load leveling. This paper shows a simulation of the LHECUS cycle. A computer model was written to balance the cycle and key parameters for optimizing the cycle were identified.