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

Zhang, Bo; Chen, Liu; Zhang, Xiaoyan; Wang, Mei; Ji, Changfa; Song, Ki-Il

doi:10.3390/en11051279

Cited by 5 publications

(5 citation statements)

References 18 publications

(39 reference statements)

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“…the HPWH's COP. As expected [14], the transcritical system was found to be much more sensitive to the water inlet temperature that the R410A-based system. For the lower water inlet temperature in Table 5, the COP of the transcritical HPWH improved the COP of the R410A-based HPWH.…”

Section: Resultssupporting

confidence: 75%

“…There exist differences between the performance predicted by theoretical models and the actual behaviour contrasted experimentally [23]. Usually, generic adjustments of experimental data are used [14], in which isentropic efficiency is expressed as function of suction and discharge pressures [13,24].…”

Section: Model Descriptionmentioning

confidence: 99%

“…The performance of CO 2 heat pumps is very sensitive to operating conditions [13], basically due to the temperature profile of the CO 2 at the gas cooler. It is presumed that, for the application considered here, where evaporator temperatures will be warm and water outlet temperatures moderate, the CO 2 heat pump could result advantageous over the conventional at some point [14]. However, this is not straightforward to assume beforehand, as the water inlet temperature will also be moderately high, limiting the water temperature rise at the gas cooler, and thus the gas cooler performance.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Comparison of Transcritical CO2 and Conventional Refrigerant Heat Pump Water Heaters for Domestic Applications

et al. 2019

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Although CO 2 as refrigerant is well known for having the lowest global warming potential (GWP), and commercial domestic heat pump water heater systems exist, its long expected wide spread use has not fully unfolded. Indeed, CO 2 poses some technological difficulties with respect to conventional refrigerants, but currently, these difficulties have been largely overcome. Numerous studies show that CO 2 heat pump water heaters can improve the coefficient of performance (COP) of conventional ones in the given conditions. In this study, the performances of transcritical CO 2 and R410A heat pump water heaters were compared for an integrated nearly zero-energy building (NZEB) application. The thermodynamic cycle of two commercial systems were modelled integrating experimental data, and these models were then used to analyse both heat pumps receiving and producing hot water at equal temperatures, operating at the same ambient temperature. Within the range of operation of the system, it is unclear which would achieve the better COP, as it depends critically on the conditions of operation, which in turn depend on the ambient conditions and especially on the actual use of the water. Technology changes on each side of the line of equal performance conditions of operation (EPOC), a useful design tool developed in the study. The transcritical CO 2 is more sensitive to operating conditions, and thus offers greater flexibility to the designer, as it allows improving performance by optimising the global system design.

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Section: Resultssupporting

confidence: 75%

Section: Model Descriptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparison of Transcritical CO2 and Conventional Refrigerant Heat Pump Water Heaters for Domestic Applications

et al. 2019

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“…However, the TCIC cycle had the least exergy loss. Another work was reported by Zhang et al (2018). They developed a simulation model to study the parametric sensitivity of three transcritical CO 2 cycles with expanders: 1) a conventional single-stage system with an expander, 2) a two-stage compression with an intercooler and the expander drives the secondstage compressor, and 3) a two-stage compression with an intercooler and the expander driving the first-stage compressor.…”

Section: Simulation Work Of Vcr Systems With Expandersmentioning

confidence: 99%

A review on expanders and their performance in vapour compression refrigeration systems

Murthy

Subiantoro

Norris

et al. 2019

International Journal of Refrigeration

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“…The theoretical analysis of the cycle performance characteristics was carried out for both refrigerants according to the first and second laws of thermodynamics. Zhang et al [23] conducted a sensitivity study for three typical expander-based transcritical CO 2 cycles, including a two-stage cycle. The sensitivities of the maximum COP to the key operating parameters, including the inlet pressure of the gas cooler, the temperatures at evaporator inlet and gas cooler outlet, the inter-stage pressure, and the isentropic efficiency of expander, were obtained.…”

Section: Introductionmentioning

confidence: 99%

Effects of Intercooling and Inter-Stage Heat Recovery on the Performance of Two-Stage Transcritical CO2 Cycles for Residential Heating Applications

Mhanna

Juan

et al. 2019

Energies

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Due to the harmful effects of synthetic refrigerants, such as chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs)n the environment, natural refrigerants like carbon dioxide (CO 2 ) have been attracting great interest. The higher inter-stage superheating of CO 2 makes it difficult to predict the effects of the intercooling on heating performance of a two-stage transcritical CO 2 cycle. In addition, very little is known about the potential of inter-stage heat rejection recovery in the heating performance enhancement of this cycle. In order to explore the effects of intercooling and inter-stage heat rejection recovery potential, three "sub-cycles"-(1) a sub-cycle with heat recovery, (2) a sub-cycle without heat recovery, and (3) a sub-cycle without intercooling-were modeled in Engineering Equation Solver (EES) software for three commonly-used two-stage transcritical cycles:(1) an intercooler cycle, (2) a flash cycle, and (3) a split cycle. Then, the discharge pressure and intermediate pressure were simultaneously optimized. Based on the optimization results, the heating performance of the sub-cycles for each cycle were compared. The results demonstrate that the incorporation of intercooling without heat recovery was detrimental to the heating performance in comparison to the absence of intercooling. It is also clear that there is a great potential for heating performance improvement through inter-stage heat recovery.

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

Cited by 5 publications

References 18 publications

Comparison of Transcritical CO2 and Conventional Refrigerant Heat Pump Water Heaters for Domestic Applications

Comparison of Transcritical CO2 and Conventional Refrigerant Heat Pump Water Heaters for Domestic Applications

A review on expanders and their performance in vapour compression refrigeration systems

Effects of Intercooling and Inter-Stage Heat Recovery on the Performance of Two-Stage Transcritical CO2 Cycles for Residential Heating Applications

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