Combined Vapor Compression Research Articles

Assessment of single rotor expander-compressor device in combined organic Rankine cycle (ORC) and vapor compression refrigeration cycle (VCR)

An environmental degradation due to consumption of fossil fuel based high grade energy releasing greenhouse gases is a pressing issue around the world. The use of low-grade heat from renewable energy sources using organic Rankine cycle is an attractive solution to reduce of emission of greenhouse gases and protect the environment. This paper investigates the potential of a new single rotor expander-compressor device in a combined Vapor Compression Refrigeration (VCR) cycle and an organic Rankine cycle (ORC). The numerical model of combined ORC-VCR is developed and validated. The thermal performance of combined cycle has been evaluated under the influence of evaporation temperature of ORC (62.75 °C–89.7 °C) and VCR (−20 °C–5 °C), condensation temperature of ORC (20 °C–45 °C) and rotor speed (500–3000 rpm) at a constant hot source (water) temperature of 95 °C. The maximum cooling effect, heat-to-cooling efficiency, and exergy efficiency achieved are found to be 5.38 kW, 56% and 63% when the evaporation temperature of ORC and VCR is 62.75 °C and −5 °C, and condensation temperature of ORC is 20.5 °C. Moreover, cooling effect increases linearly with the rotor speed, however, the heat-to-cooling efficiency and exergy efficiency are not affected by the rotor speed.

Experimental and numerical study on performance of hybrid refrigeration system that combines vapor compression and thermoelectric systems

As high-quality food preservation has become an important aspect of daily life, a need has developed for domestic household refrigerators with a wide refrigeration temperature range. The temperature range of domestic household refrigerators is generally above −20 °C. In this study, a hybrid refrigeration system that combined vapor compression refrigeration (VCR) and a thermoelectric refrigerator (TER) is investigated for the freezer compartment of a domestic refrigerator with a volume of 0.018 m3. Although an additional 99.5 W of electrical power is consumed, a lower temperature of −38.1 °C is experimentally achieved in the deep freezer compartment of a compact VCR–TER system, with no noise or mechanical parts. In contrast, a temperature of only −8.8 °C is obtained in a typical VCR system. A three-dimensional numerical model is applied to study the performance of the finned heat sink of the TER using FLUENT. The effects of the fin height and fin pitch on the thermal resistance and pressure drop are investigated. The results show that the thermal resistance decreases with an increase in the fin height and increases with an increase in the fin pitch. An optimized finned heat sink with a fin height of 50 mm is obtained, which has a thermal resistance of 0.05 °C/W. It has a higher cooling capacity of 53.6 W than the heat sink with the original fin height of 30 mm. The VCR–TER system has potential application to low-temperature domestic refrigeration systems with a small size and small cooling capacity.

Evaluation of the possibility of using propane and hydrofluorolefin group refrigerants as an eco-friendly replacement for R134a in combined heat transformers

In connection with the gradual reduction in the use of refrigerants of HFC groups, regulated by the Paris Agreement, its amendments and additions, the question arises of finding environmentally friendly working fluids with high thermodynamic efficiency in the thermal transformer cycle. The article discusses the possibility of using refrigerants from the HFO and propane group as environmentally friendly substitutes for R134a for combined vapor compression thermal transformers. The evaluation of the thermodynamic efficiency of the machines for the joint production of heat and cold, produced on the basis of the entropy method of thermodynamic analysis, is carried out. The results of modeling a single-stage combined heat transformer showed the thermodynamic feasibility of using R290 as a substitute for R134a. The analysis of the results obtained showed the limited possibility of effective use of refrigerants of the HFO group as working bodies of combined heat transformers.

Energy-efficient air conditioning system of a data processing center

BACKGROUND: Currently, because of the rapid development of digital technologies, an increasing amount of computer computing power is required where data processing centers are built, which sometimes require power consumption in the megawatt range. For stable year-round operation of data centers, reliable engineering is required, which includes air conditioning systems (ACS) for year-round use with a given level of reliability. Several traditional methods of data center cooling are available, namely, precision air conditioners based on vapor compression refrigeration machines (PCRMs) and systems with intermediate coolant (so-called chillerfancoil systems). However, in modern settings, when the required capacity of data centers increases every year and the framework for environmental friendliness and energy efficiency of installations becomes stricter, new, more energy-efficient, and environmentally friendly solutions for data center cooling is needed.
 AIM: This study aims to compare the proposed energy-efficient ACS with combined vapor compres-sion and indirect-evaporative cycle with the most commonly used ACSs in data centers and to deter-mine the boundaries of transition between the operating modes of the proposed ACS in a data center operating in Moscow as an example.
 METHODS: This study employs the following methods: analysis of existing data center cooling sys-tems, determination of a typical design set of outdoor air parameters in the region under consideration, and calculation by comparative analysis of the energy consumption of the proposed and traditional ACSs for data centers.
 RESULTS: From our study, the different ACSs currently used for data centers, namely, precision air conditioners and chillerfancoil systems are highlighted. The main components of each system, the advantages and disadvantages observed in the design, installation, and commissioning processes, and the operation of the systems are described. An alternative ACS that combines PCRM and indirect-evaporative cooling is proposed. The comparative analysis of the proposed scheme and traditional so-lutions demonstrates that the combined ACS allows significant reduction in the energy consumption for data-center cooling. Therefore, under the conditions in Moscow, the proposed system for a particu-lar year will consume energy that is two times less than a chillerfancoil system with free cooling and 2.5 times less than a system with precision air conditioners that operate on the traditional vapor-compression cycles.
 CONCLUSION: The comparative analysis of the proposed energy-efficient ACS with combined vapor compression and indirect-evaporative cycle with the most commonly used ACS in data centers con-firms its high energy efficiency and provides greater environmental safety. The boundaries of the tran-sition between the operating modes of the proposed ACS are determined in a data center that operates in Moscow as an example, which exhibits high energy efficiency and reliable operation.

Combined Vapour Compression Refrigeration System with Ejector usage: A Review

Combined Vapour Compression Refrigeration System with Ejector usage: A Review

Performance analysis of a combined vapor compression cycle and ejector cycle for refrigeration cogeneration

A hybrid vapor compression refrigeration (HVCR) system, which combines a vapor compression refrigeration (VCR) system and an ejector refrigeration (ER) system, was developed. The waste heat energy from the gas cooler in the VCR system is applied as driven source towards ER system.Thermodynamic investigations on the performance of the HVCR system, using CO2 as a refrigerant, are performed with energetic and exergetic methods, and the comparative analyses with the VCR system are conducted. Comprehensive effects of key operating parameters on the system performance are also studied. The results indicate that for the same cooling capacity, the coefficient of performance (COP) of the HVCR system shows 25% higher COP and the total mechanical power consumption is reduced by 20% than that of conventional VCR system, respectively. The performance characteristics of the proposed cycle show its application potential in cooling and air-conditioning.

Analytical Model of a Combined Adsorption Cooling and Mechanical Vapor Compression Refrigeration System

ABSTRACTA combined adsorption and mechanical vapor compression system is a reasonable option to reduce the consumption of fossil fuels for air conditioning by utilizing waste heat. Performance predictions of combined adsorption and mechanical vapor compression systems require detailed dynamic modeling because the transitional characteristics explain the nature of the adsorption system. It is, however, desirable to simplify the model for practical use at engineering stages. Since the mechanical vapor compression system is based on the steady-state thermodynamic cycle, a semi-steady-state modeling of adsorption cycles would be functional for analysis of combined systems. In our study, the analytical solution of transient simulation for adsorption cycles was combined with a steady-state mathematical model of the mechanical vapor compression system. The performance of the combined system was analyzed based on the model developed, taking into account the cycle time of the adsorption cycle. The results show the performance characteristics as well as the energy-saving potential of the combined system.

Thermoeconomic and environmental analyses of a low water consumption combined steam power plant and refrigeration chillers-Part 2: Thermoeconomic and environmental analysis

The present paper is the continuation of Part 1 of a comprehensive study on new low water consumption combined steam power plants (SPP) and refrigeration chillers. Environmental, exergy, and thermoeconomic analyses of the steam power plant with natural draft wet cooling tower (SPP-NDWCT) as the base system, combined vapor compression refrigeration and the base system (VCR-SPP-NDWCT), and combined absorption heat pump and the base system (ABHP-SPP-NDWCT) are developed. The exergy analysis is conducted to analyze and compare the systems from an exergetic point of view and the thermoeconomic analysis is done to obtain the unit cost of the water loss in the systems’ cooling towers. The environmental analysis is also carried out to obtain the annual environmental revenue of the saved water compared to the annual economic and environmental costs caused by consuming more fuel in the ABHP-SPP-NDWCT system. The results demonstrated that the NDWCT exergy loss, exergy destruction and total cost value decreased by 12%, 10.7% and 1.8% in ABHP-SPP-NDWCT system, respectively. Thus, the ABHP-SPP-NDWCT system could replace the conventional SPP-NDWCT system in regions where the environmental- economic value of water is higher than 1.081$/l.

Selection of Distributed Power-Generating Systems Based on Electric, Heating, and Cooling Loads

A generalized thermodynamic model is developed to describe combined cooling, heating, and power generating systems. This model is based on reversible power generation and refrigeration devices with practical, irreversible heat exchanger processes. It provides information on a system’s performance and allows easy comparisons among different systems at different loading conditions. Using both the first and second laws as well as the carbon dioxide production rate allows one to make a first-order system assessment of its energy usage and environment impact. The consistency of the exergy destruction rate and the first law performance ensures that the thermodynamic system boundaries are correctly and completely defined. The importance of the total thermal load to the required power ratio (HLRP) as a scaling parameter is demonstrated. A number of trends for limited conditions can be delineated even though the reported results confirmed that generalized trends are not identifiable because of the systems’ complexities. The results demonstrate that the combined vapor compression∕absorption refrigeration has higher first law utilization factors and lower carbon dioxide production rate for systems with high refrigeration to total thermal load ratios for all HLRP values. Fuel cell systems outperform engine systems for large refrigeration load applications. An illustration of combining these results to an economic analysis is presented.

Cooling performance and energy saving of a compression–absorption refrigeration system driven by a gas engine

The prototype of combined vapour compression–absorption refrigeration system was set up, where a gas engine drove directly an open screw compressor in a vapour compression refrigeration chiller and waste heat from the gas engine was used to operate absorption refrigeration cycle. The experimental procedure and results showed that the combined refrigeration system was feasible. The cooling capacity of the prototype reached about 589 kW at the Chinese rated conditions of air conditioning (the inlet and outlet temperatures of chilled water are 12 and 7°C, the inlet and outlet temperatures of cooling water are 30 and 35°C, respectively). Primary energy rate (PER) and comparative primary energy saving were used to evaluate energy utilization efficiency of the combined refrigeration system. The calculated results showed that the PER of the prototype was about 1.81 and the prototype saved more than 25% of primary energy compared to a conventional electrically driven vapour compression refrigeration unit. Error analysis showed that the total error of the combined cooling system measurement was about 4.2% in this work. Copyright © 2006 John Wiley & Sons, Ltd.

Optimum performance of a heat engine‐driven combined vapour compression–absorption–ejector heat pump

Optimum performance of an endoreversible heat engine-driven heat pump cycle, based on a combination of an absorption cycle with a vapour and ejector compression cycles is investigated. This combination increases the performance of the conventional ejector and absorption cycles and provides high performance for heating. The analysis show that the combined heat pump cycle has a significant increase in system performance over the heat engine-driven vapour compression or absorption heat pump cycle and heat engine-driven combined vapour compression and absorption heat pump cycle. Copyright © 2000 John Wiley & Sons, Ltd.

Performance analysis of a heat engine driven combined vapor compression–absorption–ejector refrigerator

An endoreversible heat engine driven refrigeration cycle based on the combination of an absorption cycle with vapor and ejector compression cycles is described. This integration maximizes the performance of the conventional ejector and absorption cycles and provides high performance for refrigeration. The analysis shows that the combined cycle has a significant increase in system performance over the heat engine driven vapor compression refrigerators and heat engine driven combined vapor compression and absorption refrigerators.

Optimum performance of a heat engine-driven combined vapour compression-absorption-ejector heat pump

Optimum performance of an endoreversible heat engine-driven heat pump cycle, based on a combination of an absorption cycle with a vapour and ejector compression cycles is investigated. This combination increases the performance of the conventional ejector and absorption cycles and provides high performance for heating. The analysis show that the combined heat pump cycle has a significant increase in system performance over the heat engine-driven vapour compression or absorption heat pump cycle and heat engine-driven combined vapour compression and absorption heat pump cycle. Copyright © 2000 John Wiley & Sons, Ltd.

Performance of irreversible combined cycles for cryogenic refrigeration

The effects of thermal resistances and internal irreversibilities on the performance of combined cycles (combined four stage vapour compression cycles and solar driven combined Brayton power and refrigeration cycles) for cryogenic refrigeration were investigated. Improved equations for the coefficient of performance of the systems under consideration were obtained. It was found that for the same cooling load and cryogenic temperature, the performances of the two systems are almost the same, regardless of greater energy consumption of the combined vapour compression cycle.

Optimal performance of an irreversible, heat engine-driven, combined vapor compression and absorption refrigerator

By employing finite-time thermodynamic approach, the optimum performance of an irreversible heat engine-driven combined vapor compression and absorption refrigerator system is investigated. To get closer to real machines, the effects of thermal resistances and internal irreversibilities on the performance of the combined cycle is considered. The analysis show that the combined cycle has a significant increase in system performance over the heat engine-driven vapor-compression refrigerators.

The performance of irreversible combined heat-pump cycles

The effects of thermal resistances and internal irreversibilities on the performance of combined heat-pump cycles (combined vapour compression - vapour compression heat pumping and combined vapour compression - absorption heat pumping) were investigated using a finite-time thermodynamic approach. Improved equations for the coefficient of performance of the systems under consideration were obtained. It was found that combined vapour compression heat pumping is more effective than combined vapour compression - absorption heat pumping for the same heating load regardless of its energy consumption being greater.

97/03219 Solar powered combined ejector vapour compression cycle for air conditioning and refrigeration

97/03219 Solar powered combined ejector vapour compression cycle for air conditioning and refrigeration

Performance analysis of R22 DMF turbo absorption refrigeration system

Vapour absorption refrigeration systems are getting more and more important because of the recent energy crisis. The present work is to analyse a combined vapour compression and vapour absorption system for refrigeration which can operate on industrial waste processes steam. In this system, steam expands in the turbine, and the work of the turbine is fed to a compressor of the vapour compression refrigeration system, which runs the compression part of the system. The exhaust steam of the turbine is fed to a generator of the vapour absorption system, and thus, the absorption part is run. The above system has been analysed with the aid of a computer, varying steam pressure (3–7 bar), flow rate of steam (100–400 kg/h) and evaporator temperature (−5–10°C). The detailed parametric study has been done to show the effect of the above parameters on system performance. A comparative study of the combined system and absorption system has been made with DMF + R22 as the working fluid. The results indicate the superiority of the combined system over the absorption system.