New correlation to predict the heat transfer coefficient during in-tube cooling of turbulent supercritical CO2

Pitla, Srinivas S.; Groll, Eckhard A.; Ramadhyani, S.

doi:10.1016/s0140-7007(01)00098-6

Cited by 177 publications

(68 citation statements)

References 5 publications

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“…(11) and calculated by employing pressure ratios of semi-hermetic compressor of eqn. (12) [10] (11) (12) and finally the compressor work can be calculated as (13)…”

Section: Compressor Modelmentioning

confidence: 99%

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Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

Islam

Sumathy

Gong

et al. 2024

RE&PQJ

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This study reports the numerical analyses of a CO 2 transcritical cycle on solar assisted heat pump water heating system in which evacuated tube U-pipe solar collector is utilized as an evaporator. This simulation model can predict operating characteristics for moderate meteorological conditions of North Dakota. The main purpose of this work is to simulate the overall performance of the heat pump cycle by varying compressor speed. From the analysis the coefficient of performance (COP) value is predicted from 1.5 -2.8 with three different average solar insolation. The results showed that the performance of the system significantly influenced by the compressor speed and solar irradiation. This study also calculated the instantaneous collector efficiency and found in the range of 50 -55%.

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“…(11) and calculated by employing pressure ratios of semi-hermetic compressor of eqn. (12) [10] (11) (12) and finally the compressor work can be calculated as (13)…”

Section: Compressor Modelmentioning

confidence: 99%

“…The water side heat transfer coefficient is determined by Nusselt relationship given by Petukhov and Roizen [11] and the supercritical CO 2 heat transfer coefficient is determined by using Pitla et al [12]. The delivered heat energy to the water can also be defined as a function of enthalpy relation: (20)…”

Section: Gas Cooler/heat Exchanger Modelmentioning

confidence: 99%

Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

Islam

Sumathy

Gong

et al. 2024

RE&PQJ

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“…Re 64 f (7) Meanwhile, for turbulent flow, Colebrook equation was used to calculate friction factor:…”

Section: Pressure Drop Equationsmentioning

confidence: 99%

“…The geometry often used for mathematical model is the circular tube-in-tube heat exchanger, where supercritical CO 2 flow in the inner tube and water flow in the annular space [7]. Most numerical analysis are done by using Renormalization Group (RNG) k-ɛ and Low-Reynolds number (LRN) k-ɛ models as the turbulence model with ANSYS FLUENT CFD codes [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Flow and Heat Transfer Characteristics of CO₂at Vapour and Supercritical Phases in Micro-Channels

et al. 2016

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Abstract. Supercritical carbon dioxide (CO2) has special thermal properties with better heat transfer and flow characteristics. Due to this reason, supercritical CO2 is being used recently in air-condition and refrigeration systems to replace non environmental friendly refrigerants. Even though many researches have been done, there are not many literatures for heat transfer and flow characteristics of supercritical CO2. Therefore, the main purpose of this study is to develop flow and heat transfer CFD models on two different phases; vapour and supercritical of CO2 to investigate the heat transfer characteristics and pressure drop in micro-channels. CO2 is considered to be in different phases with different flow pressures but at same temperature. For the simulation, the CO2 flow was assumed to be turbulent, nonisothermal and Newtonian. The numerical results for both phases are compared. From the numerical analysis, for both vapour and supercritical phases, the heat energy from CO2 gas transferred to water to attain thermal equilibrium. The temperature of CO2 at vapour phase decreased 1.78% compared to supercritical phase, which decreased for 0.56% from the inlet temperature. There was a drastic increase of 72% for average Nu when the phase changed from vapour to supercritical. The average Nu decreased rapidly about 41% after total pressure of 9.0 MPa. Pressure drop ( P ' ) increased together with Reynolds number (Re) for vapour and supercritical phases. When the phase changed from vapour to supercritical, P ' was increased about 26%. The results obtained from this study can provide information for further investigations on supercritical CO2.

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“…However, its safety and environmental properties [1] and its high heat transfer coefficients [2] make CO 2 one of the possible alternatives to the HFCs, especially in heat pumps [3] or in applications with important leakage rates, such as mobile air conditioning and commercial refrigeration [4].…”

Section: Introductionmentioning

confidence: 99%

Experimental analysis of energy performance of modified single-stage CO2 transcritical vapour compression cycles based on vapour injection in the suction line

Cabello

Sánchez

Patiño

et al. 2012

Applied Thermal Engineering

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Abstract.This work presents the experimental evaluation of the energy performance of a modified single-stage CO 2 transcritical refrigeration plant with an internal heat exchanger (IHX) based on vapour injection in suction line. This modification, which is only applicable to refrigeration plants with an expansion process divided in two stages with a liquid receiver between them, consists of extracting saturated vapour from the liquid receiver in order to: decrease the vapour quality at the evaporator inlet, and reduce the superheating degree at the compressor suction by means of the expansion and following injection of the extracted refrigerant. Three different injection points have been evaluated experimentally: before the IHX, after the IHX and just before the suction chamber of the compressor. The experimental measurements show that the cooling capacity and COP can be enhanced in 9.81% and 7.01%, respectively. Furthermore, a reduction in the discharge temperature of the compressor up to 14.7ºC has been measured inside the evaluation range. KEYWORDS

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New correlation to predict the heat transfer coefficient during in-tube cooling of turbulent supercritical CO2

Cited by 177 publications

References 5 publications

Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

Numerical Analysis of Flow and Heat Transfer Characteristics of CO₂at Vapour and Supercritical Phases in Micro-Channels

Experimental analysis of energy performance of modified single-stage CO2 transcritical vapour compression cycles based on vapour injection in the suction line

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New correlation to predict the heat transfer coefficient during in-tube cooling of turbulent supercritical CO2

Cited by 177 publications

References 5 publications

Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

Performance study on solar assisted heat pump water heater using CO2 in a transcritical cycle

Numerical Analysis of Flow and Heat Transfer Characteristics of CO2at Vapour and Supercritical Phases in Micro-Channels

Experimental analysis of energy performance of modified single-stage CO2 transcritical vapour compression cycles based on vapour injection in the suction line

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Product

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Numerical Analysis of Flow and Heat Transfer Characteristics of CO₂at Vapour and Supercritical Phases in Micro-Channels