Theoretical and experimental investigation of a combined R134a and transcritical CO2 heat pump for space heating

Yang, Dongfang; Song, Yulong; Cao, Feng; Jin, Lei; Wang, Xiaolin

doi:10.1016/j.ijrefrig.2016.07.016

Cited by 66 publications

(23 citation statements)

References 20 publications

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“…Luckily some of the Natrefs such as CO 2 (R‐744) have superior characteristics than Synrefs. Comparative studies of natural R‐744 and synthetic R‐134a refrigerants show encouraging results . Recent theoretical and experimental analyses show promising future of Natrefs in commercial heating, cooling, and refrigeration .…”

Section: Sun Powered Co2 Systemsmentioning

confidence: 97%

“…Comparative studies of natural R-744 and synthetic R-134a refrigerants show encouraging results. [225][226][227] Recent theoretical and experimental analyses show promising future of Natrefs in commercial heating, cooling, and refrigeration. 128,[228][229][230] There are also some advanced refrigeration systems developed using CO 2 as mediating fluid.…”

Section: Sun Powered Co 2 Systemsmentioning

confidence: 99%

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Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook

2019

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Summary Refrigerants bearing high global warming potential (GWP) and ozone depletion potential (ODP) were outlawed or facing time‐beared permission under the Montreal (1987), Kyoto (1997) protocols, F‐Gas law (2015), Paris Accord (2016), and recent Kigali Amendment to Montreal Protocol (2019). In order to modify followed by the paradigm shift of existing heating and cooling systems, American Society of Heating, Refrigeration, and Air‐Conditioning Engineers (ASHRAE) envisaged natural and synthetic refrigerants (Synrefs) are under investigation globally. Carbon dioxide (CO2) is a popular natural refrigerant (Natref) replacing Synrefs used in commercial heating, ventilation, air conditioning, and refrigeration (HVAC&R) systems globally. A rampant rise is observed in markets of Asia (Japan and China), North America (the United States and Canada), the Australian continent, and Africa (South Africa) by reaching 20 000 CO2‐stores around the globe. The European markets are leading the utilization of CO2 in the heat pump, and refrigeration, CO2 based markets estimate 14% of the total food retail stores (400 m2). Japan is the second leading market of CO2 heat pump and refrigeration with more than 10 200 CO2 condensing units. CO2 transcritical systems have a share of more than 10% in only European market (large stores); however, their share is less than 10% of total stores in other major markets of the world. New pump and compressor‐driven transcritical CO2 systems integrate ejectors, condensers, and booster systems to reduce energy consumptions, enhance efficiency, efficacy, and coefficient of performance. This article reports a critical review of the CO2 based heating, cooling, and refrigeration system and presents updated literature along with barriers and challenges on commercial use of Natref‐based heating and cooling applications worldwide.

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Section: Sun Powered Co2 Systemsmentioning

confidence: 97%

Section: Sun Powered Co 2 Systemsmentioning

confidence: 99%

Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook

2019

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“…The Cheng et al flow pattern based evaporation heat transfer and two phase frictional pressure drop models for have been widely used for simulations of CO2 refrigeration, air-conditioning and heat pump systems by a number of researchers [61][62][63][64][65]. For example, in order to improve the system performance of the CO2 heat pump, it is necessary to develop an optimum design and a control method for the CO2 heat pump water heater.…”

Section: Simulations Of Co2 Thermal Systems Using the Cheng Et Al Momentioning

confidence: 99%

“…The model is a useful tool for analysing the behaviour in transient and steady conditions simulating various operating conditions of the heat pump including solar radiation, ambient temperature, wind speed and atmospheric conditions. Yang et al [65] investigated experimentally a prototype of combined R134a and transcritical CO2 heat pump. The experimental results demonstrated that the combined system could operate reliably and supply stable temperature hot water over a wide range of ambient temperatures and feed water temperatures.…”

Section: Simulations Of Co2 Thermal Systems Using the Cheng Et Al Momentioning

confidence: 99%

Flow Boiling Heat Transfer and Two-Phase Flow of Carbon Dioxide: Fundamentals, Mechanistic Models and Applications

Cheng¹

2019

Proceedings of the 4th World Congress on Momentum, Heat and Mass Transfer

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In order to design evaporators for the CO2 thermal systems effectively, it is essential to understand the fundamentals and mechanisms of flow boiling heat transfer, flow patterns and two-phase flow characteristics of CO2 inside horizontal tubes including both the macro-and micro-channels. The proper prediction models for CO2 flow boiling heat transfer should be relevant to the physical mechanisms and corresponding flow patterns. This paper presents a comprehensive review of flow boiling heat transfer and two-phase flow of CO2 characteristics and their prediction methods. First, the review addresses the extensive experimental studies on flow boiling heat transfer and two-phase flow in macro-channels and micro-channels. Then, The studies of CO2 two-phase flow patterns are summarized. Furthermore, the effects of oil on the flow boiling heat transfer and two-phase pressure drops are analyzed. The generalized mechanistic models for flow boiling heat transfer and two-phase pressure drops of CO2 and a new flow pattern map specially for CO2, which cover both macro-and micro-channels developed by Cheng et al. are presented and compared to the experimental data in the literature. It has been proved that the models and flow maps favorably agree with the experimental data. In the application aspect, comparison of simulation results and the experimental data in the real thermal systems are presented.Keywords: Carbon dioxide, flow boiling, two phase flow, flow patterns, heat transfer, flow pattern map, dryout, mechanisms, mechanistic model and applications.ICMFHT Keynote 2-2 that of R22 and NH3. As the effects of good thermophysical properties, favorably evaporation heat transfer and two-phase flow characteristics of CO2, smaller pipe dimensions can be used in its refrigeration systems. The use of CO2 in these refrigeration systems requires the understanding and prediction of convective boiling, two-phase flow patterns and pressure drops at low temperatures for achieving more accurate designs of evaporators and more energy-efficient cycles using CO2.Furthermore, CO2 has favorable thermal performance when used in air-conditioning and heat pump systems as compared to conventional refrigerants. For example, in the CO2 automobile air-conditioning system. for ambient air temperatures, the heat transfer process on the high pressure side of a CO2 cycle is not a condensation process as in conventional systems but a supercritical gas cooling process [3,4,6]. For the evaporation processes in the evaporator, CO2 evaporates at much higher pressure than conventional refrigerant R134a [1,3]. The physical and transport properties of CO2 are quite different from those of conventional refrigerants at the same saturation temperatures. The physical properties have a significant effect on the evaporation processes including the two-phase flow patterns, evaporation heat transfer characteristics and two-phase frictional pressure drops in the compact heat exchangers with micro-channels. Therefore, it is essential to understand the two-phase flow and...

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“…performed Monte Carlo simulations to investigate the microscopic structure and VLE of the R134a molecule. In recent findings, R134a and other refrigerants combined with CO 2 , show promising results as alternative refrigerants . This can be of great help in mitigating human involvement in global warming.…”

Section: Introductionmentioning

confidence: 99%

Phase Equilibria and Condensed Phase Properties of Fluorinated Alkanes via First Principles Simulations

et al. 2017

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Vapor liquid equilibria (VLE) of organic compounds is governed by weak non‐covalent interactions. This presents a significant challenge in predicting VLE using a first principles approach where density functional theory is used to model system potential. However, a dispersion corrected approach has significantly improved the performance of traditional density functionals. Here, we predict the VLE for a nonpolar carbon tetrafluoride (R14) and polar 1,1,1,2‐tetrafluoroethane (R134a) via first principles Gibbs ensemble Monte Carlo simulations using PBE−D3 density functional. We find that the saturated liquid density for R14 is slightly under predicted for subcritical temperatures, while for R134a it is under predicted at lower reduced temperatures and over predicted at higher reduced temperatures. In the liquid phase, angle‐resolved pair correlation functions indicate slight preference for R143a to align in parallel and antiparallel orientation in the first solvation shell. The vibrational spectra reveal peak broadening in the condensed phase due to solvothermal effects. Overall, we find the PBE−D3 functional performance is better for the nonpolar molecule as compared to the polar one.

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Theoretical and experimental investigation of a combined R134a and transcritical CO2 heat pump for space heating

Cited by 66 publications

References 20 publications

Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook

Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook

Flow Boiling Heat Transfer and Two-Phase Flow of Carbon Dioxide: Fundamentals, Mechanistic Models and Applications

Phase Equilibria and Condensed Phase Properties of Fluorinated Alkanes via First Principles Simulations

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Theoretical and experimental investigation of a combined R134a and transcritical CO2 heat pump for space heating

Cited by 66 publications

References 20 publications

Review of carbon dioxide (CO 2 ) based heating and cooling technologies: Past, present, and future outlook

Review of carbon dioxide (CO 2 ) based heating and cooling technologies: Past, present, and future outlook

Flow Boiling Heat Transfer and Two-Phase Flow of Carbon Dioxide: Fundamentals, Mechanistic Models and Applications

Phase Equilibria and Condensed Phase Properties of Fluorinated Alkanes via First Principles Simulations

Contact Info

Product

Resources

About

Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook

Review of carbon dioxide (CO ₂ ) based heating and cooling technologies: Past, present, and future outlook