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

Paniagua, Ignacio López; Álvaro, Ángel Jiménez; Martín, Javier Rodríguez; Fernández, Celina González; Carlier, Rafael Nieto

doi:10.3390/en12030479

Cited by 10 publications

(6 citation statements)

References 21 publications

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“…The thermodynamic properties, flow rate, pressure, and heat transfer efficiency of R32, R290, and R454b are compared in the system compressor, evaporator, and condenser under given conditions. Paniagua et al [18] compared the system performance of transcritical CO 2 and R410A heat pumps in zero-energy comprehensive building applications. Combined with experimental data and models, the situation of two hot pumps receiving and generating hot water at the same ambient temperature was analyzed.…”

Section: Introductionmentioning

confidence: 99%

Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

Wang

Han

et al. 2020

Energies

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A marine seawater source heat pump is based on the relatively stable temperature of seawater, and uses it as the system’s cold and heat source to provide the ship with the necessary cold and heat energy. This technology is one of the important solutions to reduce ship energy consumption. Therefore, in this paper, the heat exchanger in the CO2 heat pump system with graphene nano-fluid refrigerant is experimentally studied, and the influence of related factors on its heat transfer enhancement performance is analyzed. First, the paper describes the transformation of the heat pump system experimental bench, the preparation of six different mass concentrations (0~1 wt.%) of graphene nanofluid and its thermophysical properties. Secondly, this paper defines graphene nanofluids as beneficiary fluids, the heat exchanger gains cold fluid heat exergy increase, and the consumption of hot fluid heat is heat exergy decrease. Based on the heat transfer efficiency and exergy efficiency of the heat exchanger, an exergy transfer model was established for a seawater source of tube heat exchanger. Finally, the article carried out a test of enhanced heat transfer of heat exchangers with different concentrations of graphene nanofluid refrigerants under simulated seawater constant temperature conditions and analyzed the test results using energy and an exergy transfer model. The results show that the enhanced heat transfer effect brought by the low concentration (0~0.1 wt.%) of graphene nanofluid is greater than the effect of its viscosity on the performance and has a good exergy transfer effectiveness. When the concentration of graphene nanofluid is too high, the resistance caused by the increase in viscosity will exceed the enhanced heat transfer gain brought by the nanofluid, which results in a significant decrease in the exergy transfer effectiveness.

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Section: Introductionmentioning

confidence: 99%

Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

Wang

Han

et al. 2020

Energies

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“…The natural working medium, CO 2 , has been studied and applied by people because of its excellent characteristics of zero ODP (ozone depletion potential) and low GWP [1]. Compared to heat pumps using the conventional working medium, the temperature drop curve of the transcritical CO 2 heat pump in the heat release process and the temperature rise curve of the water can form a good matching relationship [2], which not only improves the heat exchange efficiency but also makes it have great advantages in the production of high-temperature hot water [3].…”

Section: Introductionmentioning

confidence: 99%

Performance Analysis of Transcritical CO2 Quasi-Secondary Compression Cycle with Ejector Based on Pinch Point

Yang

Zhang

Wang

et al. 2023

Designs

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To investigate the performance of transcritical CO2 quasi-secondary compression cycle with ejector (TCIEJ) for heat pump water heaters, the thermodynamic model of TCIEJ is established based on the pinch point, and TCEX, TCEJ, and TCI are selected as comparisons. The effects of changing high pressure and ambient temperature on the heating COP and compressor exhaust temperature are analyzed, and the influence of cooling water inlet and outlet temperature and vapor injection pressure on TCIEJ is further analyzed. The results show that there are optimal high pressures that make the heating COP of the four heat pump cycles reach the maximum value, of which TCIEJ has the best performance. At an ambient temperature of −15 °C, the maximum heating COP of TCIEJ increased by about 20.5%, 14.9%, and 7.9% compared with TCEX, TCEJ, and TCI. With the increase in ambient temperature, the optimal high pressure continues to increase, and the corresponding maximum heating COP gradually increases. Selecting the geometric mean of high pressure and evaporation pressure as the optimal vapor injection pressure for TCIEJ, the error is small compared to the actual optimal vapor injection pressure. With the increase in ambient temperature and cooling water outlet temperature, the optimal high pressure of TCIEJ continues to increase, and the correlation formula of optimal high pressure is fitted according to the simulation results.

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“…Steven Brown [5] discussed the refrigeration technology, including transcritical carbon dioxide refrigeration. Ignacio López Paniagua et al [6] conducted a comparative study between the transcritical CO 2 HPWH and the R410A HPWH, and found that the CO 2 HPWH had better performance and broader prospects. Xiufang Liu et al [7] built a transcritical CO 2 HPWH experimental bench and found that coefficient of performance (COP) was positively correlated with water flow and water temperature.…”

Section: Introductionmentioning

confidence: 99%

The Influence of Internal Heat Exchanger on the Performance of Transcritical CO2 Water Source Heat Pump Water Heater

et al. 2020

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The characteristics of the transcritical CO2 heat pump water heater (HPWH) system are; a lower inlet hot water temperature (Ti-hw) (sometimes this is lower than the water source temperature), and an outlet gas cooler temperature (To-gc) which is affected by the Ti-hw and often lower than the critical temperature. In order to study the effects of the internal heat exchanger (IHX) on the operational performance of the transcritical CO2 HPWH when To-gc is low, a transcritical CO2 water source HPWH experiment platform is established to conduct experimental research and comparative analysis on the operational performance of the transcritical CO2 water source HPWH, with or without IHX. It is found that, if only the coefficient of performance (COP) and heating at the optimal exhaust pressure of the transcritical CO2 water source HPWH were considered, COP and the heating of the non-IHX system would be slightly higher than those of the IHX system at the lower hot water flow and water source temperature, and this increase was not obvious. At the higher hot water flow rate and water source temperature, COP and the heating of the non-IHX system were also higher than those of the IHX system, and the increase was obvious. The experiment results showed that, near the optimal exhaust pressure, the variation range of COP and heating of the IHX system is relatively small, and the system has a relatively high stability.

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

Cited by 10 publications

References 21 publications

Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

Performance and Exergy Transfer Analysis of Heat Exchangers with Graphene Nanofluids in Seawater Source Marine Heat Pump System

Performance Analysis of Transcritical CO2 Quasi-Secondary Compression Cycle with Ejector Based on Pinch Point

The Influence of Internal Heat Exchanger on the Performance of Transcritical CO2 Water Source Heat Pump Water Heater

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