Energy recovery by means of a radial piston expander in a CO2 refrigeration system

Ferrara, Giovanni; Ferrari, Lorenzo; Fiaschi, Daniele; Galoppi, Giovanni; Karellas, Sotiriοs; Secchi, Riccardo; Tempesti, Duccio

doi:10.1016/j.ijrefrig.2016.07.014

Cited by 31 publications

(11 citation statements)

References 19 publications

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“…It is well known that the most efficient method to improve the performance of transcritical CO 2 cycle is to replace the throttling valve with an expander and recover its expansion work. Therefore, various types of CO 2 expanders were developed and investigated experimentally, such as free piston expander-compressor units [8,9], scroll expander [10], rolling piston expander [11,12], vane rotary expander [13,14], reciprocating piston expander [15,16] and radial piston expander [17]. After more than ten years of continuous development and improvement, the isentropic efficiency of expander was greatly improved, reaching a maximum of 77% [12].…”

Section: Introductionmentioning

confidence: 99%

Parameter Sensitivity Study for Typical Expander-Based Transcritical CO2 Refrigeration Cycles

et al. 2018

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A sensitivity study was conducted for three typical expander-based transcritical CO 2 cycles with the developed simulation model, and the sensitivities of the maximum coefficient of performance (COP) to the key operating parameters, including the inlet pressure of gas cooler, the temperatures at evaporator inlet and gas cooler outlet, the inter-stage pressure and the isentropic efficiency of expander, were obtained. The results showed that the sensitivity to the gas cooler inlet pressure differs greatly before and after the optimal gas cooler inlet pressure. The sensitivity to the intercooler outlet temperature in the two-stage cycles increases sharply to near zero and then keeps almost constant at intercooler outlet temperature of higher than 45 • C. However, the sensitivity stabilizes near zero when the evaporator inlet temperature is very low of −26.1 • C. In two-stage compression with an intercooler and an expander assisting in driving the first-stage compressor (TEADFC) cycle, an abrupt change in the sensitivity of maximum COP to the inter-stage pressure was observed, but disappeared after intercooler outlet temperature exceeds 50 • C. The sensitivity of maximum COP to the expander isentropic efficiency increases almost linearly with the expander isentropic efficiency.

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Section: Introductionmentioning

confidence: 99%

Parameter Sensitivity Study for Typical Expander-Based Transcritical CO2 Refrigeration Cycles

et al. 2018

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“…This power covers a fraction of the necessary power input for the compression process. Even if this device operates with low efficiency of 19% [96], due to the two-phase operation and other losses (e.g., mechanical), the work recovery potential is significant. Baek et al [97] reached an even lower isentropic efficiency of 11% using a reciprocating piston expander, probably due to the internal leakages, resulting however to a COP increase of 10%.…”

Section: Expansion Machine At the Gas Cooler Exitmentioning

confidence: 99%

Review of Experimental Research on Supercritical and Transcritical Thermodynamic Cycles Designed for Heat Recovery Application

et al. 2019

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Supercritical operation is considered a main technique to achieve higher cycle efficiency in various thermodynamic systems. The present paper is a review of experimental investigations on supercritical operation considering both heat-to-upgraded heat and heat-to-power systems. Experimental works are reported and subsequently analyzed. Main findings can be summarized as: steam Rankine cycles does not show much studies in the literature, transcritical organic Rankine cycles are intensely investigated and few plants are already online, carbon dioxide is considered as a promising fluid for closed Brayton and Rankine cycles but its unique properties call for a new thinking in designing cycle components. Transcritical heat pumps are extensively used in domestic and industrial applications, but supercritical heat pumps with a working fluid other than CO2 are scarce. To increase the adoption rate of supercritical thermodynamic systems further research is needed on the heat transfer behavior and the optimal design of compressors and expanders with special attention to the mechanical integrity.

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“…The use of a supercritical cycle, which is mostly due to the required temperature levels, allows a proper matching of the heat capacities of the stored water (pressurized at 1800 kPa) and of the heat pump working fluid (supercritical CO2). With respect to a traditional heat pump, an expander is proposed in place of the throttling valve (21)(22), which allows an increase in COP values [16]. Moreover, the heat pump cycle is deeply Finally, the required compressor work (23)(24), partly supported by the expander), is provided by a PV array, which thus allows a complete solar TEES integration.…”

Section: Description Of Teesmentioning

confidence: 99%

“…The power cycle operating parameters under design conditions are summarized in Table 2. With respect to a traditional heat pump, an expander is proposed in place of the throttling valve (21)(22), which allows an increase in COP values [16]. Moreover, the heat pump cycle is deeply integrated with solar panels and PV collectors.…”

Section: Description Of Teesmentioning

confidence: 99%

“…This matter is correctly addressed by an exergy approach, which is described in the following. From an energy perspective, a marginal round-trip efficiency can be defined in terms of electricity only as in Equation ( 16): (16) In Equation ( 16), contribution from the solar-thermal field is disregarded-solar-thermal input is considered to be a secondary energy of lower quality.…”

Section: Performance Indicators-energymentioning

confidence: 99%

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Thermo-Electric Energy Storage with Solar Heat Integration: Exergy and Exergo-Economic Analysis

et al. 2019

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A Thermo-Electric Energy Storage (TEES) system is proposed to provide peak-load support (1–2 daily hours of operation) for distributed users using small/medium-size photovoltaic systems (4 to 50 kWe). The purpose is to complement the PV with a reliable storage system that cancompensate the produc tivity/load mismatch, aiming at off-grid operation. The proposed TEES applies sensible heat storage, using insulated warm-water reservoirs at 120/160 °C, and cold storage at −10/−20 °C (water and ethylene glycol). The power cycle is a trans-critical CO2 unit including recuperation; in the storage mode, a supercritical heat pump restores heat to the hot reservoir, while a cooling cycle cools the cold reservoir; both the heat pump and cooling cycle operate on photovoltaic (PV) energy, and benefit from solar heat integration at low–medium temperatures (80–120 °C). This allows the achievement of a marginal round-trip efficiency (electric-to-electric) in the range of 50% (not considering solar heat integration).The TEES system is analysed with different resource conditions and parameters settings (hot storage temperature, pressure levels for all cycles, ambient temperature, etc.), making reference to standard days of each month of the year; exergy and exergo-economic analyses are performed to identify the critical items in the complete system and the cost of stored electricity.

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Energy recovery by means of a radial piston expander in a CO2 refrigeration system

Cited by 31 publications

References 19 publications

Parameter Sensitivity Study for Typical Expander-Based Transcritical CO2 Refrigeration Cycles

Parameter Sensitivity Study for Typical Expander-Based Transcritical CO2 Refrigeration Cycles

Review of Experimental Research on Supercritical and Transcritical Thermodynamic Cycles Designed for Heat Recovery Application

Thermo-Electric Energy Storage with Solar Heat Integration: Exergy and Exergo-Economic Analysis

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