Modeling and simulation of the transcritical CO2 heat pump system

Lin, Kon‐Ping; Kuo, C. S.; Hsieh, Wen Der; Wang, Chi-Chuan

doi:10.1016/j.ijrefrig.2013.08.008

Cited by 26 publications

(4 citation statements)

References 22 publications

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“…The equality of the two properties functions in Equation ( 18) can be solved through an iterative process, providing P 3 [Pa]. Knowing P 3 value that satisfies, Equation ( 16), it is possible to obtain the specific enthalpy at the gas cooler inlet and outlet through Equations ( 5) and (7), respectively. Furthermore, it is possible to obtain the refrigerant mass flow rate from the gas cooler energy balance equation written as in Equation (8).…”

Section: Compressor Isentropic Efficiency Known As a Constantmentioning

confidence: 99%

“…Many polynomial correlations for the compressor isentropic efficiency, as functions of the pressure ratio, can be found in the open literature. The most common are fourth-order (n = 4) and linear (n = 1) correlations [7][8][9]. However, the polynomial order depends on the compressor type, information provided by the compressor manufacturer, or on the regression analysis performed by the researchers.…”

Section: Compressor Isentropic Efficiency Given By a Polynomial Corre...mentioning

confidence: 99%

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The Role of the Compressor Isentropic Efficiency in Non-Intrusive Refrigerant Side Characterization of Transcritical CO2 Heat Pump Water Heaters

Lamas

Costa

2022

Clean Technol.

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Characterizing the refrigerant side of heat pump water heaters (HPWHs) can be intrusive and expensive. On the other hand, direct external measurement techniques can be unfeasible, particularly in commercial HPWHs for residential applications. Non-intrusive in situ characterization methods have already been successfully implemented in subcritical heat pumps. They provide the refrigerant mass flowrate and the equipment energy performance, by using contact temperature sensors and electric power meters. Subcritical suction and discharge-specific enthalpies necessary to apply the method can be obtained from the measured temperatures and their corresponding saturation pressures. Nevertheless, this approach does not apply to the transcritical CO2 HPWHs. In the supercritical region, temperature and pressure are independent variables, and an iterative process regarding the compressor isentropic efficiency has to be considered. However, when isentropic efficiency data are not available, an additional procedure is required, using a validated gas cooler model to verify the physical reliability of the numerical solutions. This work aims at presenting base thermodynamic analysis of a novel methodology for non-intrusive refrigerant side characterization of transcritical CO2 HPWHs, exploring the influence of the compressor isentropic efficiency condition.

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Section: Compressor Isentropic Efficiency Known As a Constantmentioning

confidence: 99%

Section: Compressor Isentropic Efficiency Given By a Polynomial Corre...mentioning

confidence: 99%

The Role of the Compressor Isentropic Efficiency in Non-Intrusive Refrigerant Side Characterization of Transcritical CO2 Heat Pump Water Heaters

Lamas

Costa

2022

Clean Technol.

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“…In the earliest years, prototype CO2 heat pumps have been developed, and their performance characteristics have been investigated experimentally: Nekså et al have developed a prototype heat pump water heater and have clarified its performance characteristics [2]; White et al have constructed a heat pump for water heating and have created a model for performance prediction [3]; Richter et al have compared the performance of a prototype heat pump with that of a conventional one [4]. On the other hand, simulation models for CO2 heat pump transcritical cycles have been developed for [11]. Some studies for performance enhancement of CO2 heat pump transcritical cycles have been conducted: Cavallini et al have conducted a theoretical and experimental analysis to optimize a two-stage cycle [12]; Aprea and Maiorino have conducted an experimental investigation to optimize heat rejection pressure for a split system [13]; Xu et al have conducted an experimental study on performance of a system with ejector under optimum high-side pressure [14]; Qi et al have conducted an experimental investigation to optimize rejection pressure for a water heater [15].…”

Section: Introductionmentioning

confidence: 99%

Numerical analysis on performance enhancement of a CO2 heat pump water heating system by extracting tepid water

Ohkura

Yokoyama

Nakamata

et al. 2015

Energy

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Water heating systems each of which is composed of an air-to-water heat pump using CO2 as a natural refrigerant and a hot water storage tank have been developed, and are expected to contribute to energy saving in residential hot water supply.However, the area of tepid water in the storage tank expands because of heat conduction during long time storage, which leads to a degradation of the system performance.One of the ways to reduce the area of tepid water and enhance the system performance is to extract tepid water from the side of the storage tank. In this paper, the performance enhancement of a CO 2 heat pump water heating system with such a revised storage tank is analyzed by numerical simulation. The simulation model developed previously for a conventional system is extended by modifying the model for the storage tank and verifying its validity through experiments. Through a performance analysis using a standardized hot water demand, it is clarified how system performance 2 values of the revised system are enhanced, and especially how the trade-off relationship between the system efficiency and the volume of unused hot water is improved, in comparison with those of the conventional system.

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“… indicates the refrigerant flowrate, suction ρ defines the density of the refrigerant inlet to the compressor, s V and N are the swept volume and the RPM of the compressor. The volumetric efficiency of the compressor isgiven by[25],…”

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confidence: 99%