Thermodynamic analysis of two-component, two-phase flow in solar collectors with application to a direct-expansion solar-assisted heat pump

Aziz, Wajid; Chaturvedi, Sushil K.; Kheireddine, A.

doi:10.1016/s0360-5442(98)00089-9

Cited by 37 publications

(8 citation statements)

References 10 publications

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“…Aziz et al [22], conducted a numerical analysis of a solar collector which was employed as an evaporator of a heat pump cycle. In order to evaluate the size of a solar collector multiphase flow of (R-123-R134a) mixture is analysed, thermodynamic and heat transfer characteristics were calculated.…”

Section: Nomenclaturementioning

confidence: 99%

“…The effect of various mass flow rate of the mixture, solar radiation and inlet pressure on the heat transfer coefficient and collector tube length was also taken into account. Authors concluded that both mass flow rate and solar radiation have important effects on the collector size and heat transfer coefficient of the mixture where operating pressure does not have any significant effect on the tube length of collector [22].…”

Section: Nomenclaturementioning

confidence: 99%

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Mathematical modelling and simulation of multiphase flow in a flat plate solar energy collector

Helvaci

Khan

2015

Energy Conversion and Management

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a b s t r a c tNon-conventional collectors where organic fluid or refrigerant experience a phase change have many advantages over conventional collectors which have either air or relatively high temperature boiling liquid. Increase in heat transfer coefficient and system efficiency, corrosion prevention and freeze protection are the main benefits of the first type. In this study, a detailed numerical model of a flat plate collector is developed to investigate the fluid mean temperature, useful heat gain and heat transfer coefficient along the collector tube. The refrigerant HFC-134a was used in the simulation as the working fluid of the collector. The model can both predict the location where the fluid undergoes a phase change in the tube and the state at the exit under given inlet conditions. The effect of boiling on the heat transfer coefficient of the fluid is also investigated. Simulations were performed at three different mass flow rates (0.001, 0.005 and 0.01 kg/s) and three different operating pressures (4, 6 and 8 bar) to be able to see the effect of mass flow rate and pressure on plate temperature, heat loss coefficient, efficiency of the collector and the heat transfer coefficient of the fluid. The simulation results indicate that the heat transfer coefficient of the fluid increases from 153.54 W/m 2 K to 610.27 W/m 2 K in multiphase flow region. In the liquid single phase region, the collector efficiency rises from 60.2% to 68.8% and the heat transfer coefficient of the fluid increases from 39.24 W/m 2 K to 392.31 W/m 2 K with an increased flow rate whereas the collector efficiency decreases from 72.5% to 62.3% as the operating pressure increases from 4 bar to 8 bar. In order to validate the simulation model an experimental test rig was built and the experiments were performed with HFE 7000 as working thermo-fluid. A new simulation model utilizing HFE 7000 has been developed and the outlet temperature of the fluid was compared with the measured outlet temperature. Both measured and simulated results have shown close conformity.

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Section: Nomenclaturementioning

confidence: 99%

Section: Nomenclaturementioning

confidence: 99%

Mathematical modelling and simulation of multiphase flow in a flat plate solar energy collector

Helvaci

Khan

2015

Energy Conversion and Management

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“…Later on, Chaturvedi and Abazeri [5] simulated the performance of said DXSAHP during a period; they arrived to the conclusion that the most important parameters related to the design were the solar collector area, evaporation temperature, rotational speed of the compressor and the thermo-physical properties of the working fluid. At a later time, Aziz and Chaturvedi [6] experimented with the same DXSAHP design and concluded that a variation in the mass flow of the refrigerant affects significantly its heat transfer coefficient, and that the change in piping diameter and collector pressure are irrelevant, being the collector size the most critical dimension that affects the performance of the working fluid. Other authors such as Ito et al [7] also experimented with the collector dimensions and construction, concluding that they do not have a significant effect on the DXSAHP's performance, as long as it is not working under extreme conditions and the solar radiation index is at its maximum.…”

Section: Analysis Of the Solar Collectorsmentioning

confidence: 99%

Mathematical Thermal Modelling of a Direct-Expansion Solar-Assisted Heat Pump Using Multi-Objective Optimization Based on the Energy Demand

León-Ruiz

Carvajal-Mariscal

2018

Energies

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An analytical model is proposed to evaluate the performance of a Direct Expansion Solar-Assisted Heat Pump under a given environmental condition. These thermal machines commonly employ uncovered flat plate solar collectors, and given this, the convection phenomenon is taken into account as well as the effect of the diffuse and reflected solar radiation in addition to the normal beam radiation absorbed by the tilted surface of the collectors. The heat pump cycle is modelled through a first law of thermodynamics approach in order to compute the heat yielded through condensation and the minimum heat required by the volume of water in the thermal storage unit. Consequently, the thermal capacity of the heat pump, the ratio at which the system yields heat to a given load of water, is calculated and discussed. The results of the model proposed are compared with the experimental data provided by three research papers with experiments conducted in different geographic coordinates and test rigs operating during diverse atmospheric conditions. A maximum relative error of 20% was obtained and furthermore, a statistical analysis of the data was conducted having found that there is no significant statistical difference between the analytical and experimental data samples within the 95% confidence interval. Finally, based on the thermal capacity, the performance of the heat pump is evaluated and a multi-objective optimization technique is implemented to obtain the best possible combination of factors to further enhance the performance of the heat pump.

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“…The results showed that the zeotropic mixture can potentially improve the COP and the functionality of the system. A thermodynamic assessment was conducted by Aziz et al 22 to evaluate a solar‐assisted heat pump by detecting the best refrigerant mixture. The analysis was conducted by testing the utilization of multi‐phase domain and analyzing the impacts of the critical variables on the functionality of the plant.…”

Section: Introductionmentioning

confidence: 99%

Thermodynamic and thermoeconomic analyses of an ejector/booster enhanced heat pump system with zeotropic mixture

2020

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Summary In the current investigation, a novel ejector‐enhanced heat pump system was presented and comprehensively evaluated using zeotropic mixtures. In the suggested plant, a booster was added to the conventional ejector‐enhanced system to expand its performance. Moreover, the suggested plant was modeled in a way to operate zeotropic mixtures, in order to maximize the productivity of the system. The plant was investigated with regard to energy, exergy, and thermoeconomic analyses to have a deep insight of the performance characteristics, that is, exergy efficiency, COP, and unit price of the product. To this end, a parametric evaluation was conducted to predict the performance characteristics of the plant by changing the value of different input variables. The results of exergy analysis indicated that the maximum exergy annihilation (7.784 kW) was associated with the ejector. The proposed system was also compared with a conventional system, and the findings unfolded that the COP of the proposed system surpassed the conventional system by up to 25%. Moreover, the outcomes of thermoeconomic analysis showed that the unit product cost of the proposed system is 133.596 $/GJ. The outcomes further demonstrated that the highest performance of the plant was concluded using R‐600/R‐143a mixture fluid with R‐600 mass fraction of 0.45. The sensitivity evaluation further indicated that, by enhancing the condenser temperature, exergetic efficiency and heating load increased while COP and unit cost of product decreased. Moreover, there was an optimum local point, in terms of exergetic efficiency (29.5%), when the booster pressure ratio is about 1.4. In addition, at the ejector pressure lift of 1.15, the exergetic efficiency was maximized locally. The heating load of the system, however, increased continually with increasing pressure lift. The proposed system showed a decent functionality with respect to thermodynamic and thermoeconomic criteria.

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Thermodynamic analysis of two-component, two-phase flow in solar collectors with application to a direct-expansion solar-assisted heat pump

Cited by 37 publications

References 10 publications

Mathematical modelling and simulation of multiphase flow in a flat plate solar energy collector

Mathematical modelling and simulation of multiphase flow in a flat plate solar energy collector

Mathematical Thermal Modelling of a Direct-Expansion Solar-Assisted Heat Pump Using Multi-Objective Optimization Based on the Energy Demand

Thermodynamic and thermoeconomic analyses of an ejector/booster enhanced heat pump system with zeotropic mixture

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