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Jie Deng - One of the best experts on this subject based on the ideXlab platform.

  • dynamic thermal performance prediction model for the flat plate solar Collectors based on the two node lumped heat capacitance method
    Solar Energy, 2016
    Co-Authors: Jie Deng, Guofeng Yuan, Chun Chang, Xudong Yang
    Abstract:

    Abstract Two-node lumped heat capacitance model of the flat-plate solar Collectors is derived strictly based on the concept of the Collector flow efficiency factor F ′ . It is found that the obtained first-order differential model turns out to be the amended quasi-dynamic test (QDT) model. The Collector dynamic response time constant τ d is identified referring to the first-order response system in automatic control theory. Then the dynamic thermal performance prediction model for the flat-plate solar Collectors on the basis of the amended QDT model is deduced using integral treatment within a small time interval in order to extend the thermal inertia correction model (TICM) to be fit for different conditions, such as moderate or intensive change rates of the Collector Inlet Temperature, wide-range ratios of the diffuse radiation to global radiation, different incidence angles, etc. Correlation between the presented prediction model and the TICM base on the steady-state test (SST) for the flat-plate solar Collectors is elucidated and the relation between the Collector dynamic response time constant τ d and the static time constant τ C is elaborated. Finally, experimental tests of both the steady-state tests and dynamic tests with a specific flat-plate solar air Collector are conducted to verify the performance of the proposed dynamic prediction model and corresponding parameters. It is verified that the presented prediction model in terms of the Collector dynamic response time constant τ d can accurately predict the dynamic thermal performances of the flat-plate solar air Collector under different conditions.

  • Validation of a simple dynamic thermal performance characterization model based on the piston flow concept for flat-plate solar Collectors
    Solar Energy, 2016
    Co-Authors: Jie Deng, Ming Yang, Zhu Xiaolin, Jianhua Fan, Guofeng Yuan, Zhifeng Wang
    Abstract:

    Abstract A simple dynamic characterization model of flat-plate solar Collectors based on the piston flow concept is used both to identify the Collector characteristic parameters and to predict the dynamic thermal performance. The heat transport time originally defined as (1 −  e −1 ) −1 τ C by Amrizal et al. (2012) for the model turns out to be the Collector static response time constant τ C by analytical derivation. The nonlinear least squares method is applied to determine the characteristic parameters of a flat-plate solar air Collector previously tested by the authors. Then the obtained parameters are used to predict the dynamic behavior of the Collector outlet Temperature. The model coefficients particularly c 3 in the simple dynamic characterization model are examined by the Collector dynamic prediction under variable meteorological conditions. Meanwhile, the prediction accuracy of the simple dynamic model based on the first-order difference method is compared to that of the numerical solution of the Collector ordinary differential equation (ODE) model using the fourth-order Runge-Kutta method. The improved thermal inertia model (TIM) on the basis of closed-form solution presented by Deng et al. (2016a) is also considered. The results show that the prediction performance of the simple dynamic model is nearly as accurate as the ODE numerical solution and the TIM by Deng et al. (2016a) except some special conditions such as sharply changed solar irradiance and Collector Inlet Temperature.

D.b. Turkington - One of the best experts on this subject based on the ideXlab platform.

  • An analysis of solar heating systems that use vapor-compression cycles
    Solar Energy, 2003
    Co-Authors: M. Suzuki, Michael D. Devine, Hillel Kumin, D.b. Turkington
    Abstract:

    Abstract This paper analyzes the technical and economic performance of solar heating systems that use vapor-compression cycles, circulating a compressible fluid as the working fluid. With conventional solar heating systems that use water or as their working fluid, the Collector Inlet Temperature is equal to that of the storage outlet Temperature. Operating the system on a cold day can result in large thermal losses to the surroundings and, thus, low useful heat gains. A vapor-compression cycle may be attractive because it allows the Collector Inlet Temperature to be lowered so that the heat gain of the Collector can be increased. Such a system is simulated and a preliminary economic analysis performed. The results indicate that the vapor-compression system can collect almost 50% more solar energy than a conventional system if the Collector area of the two systems are the same.

Philip C. Eames - One of the best experts on this subject based on the ideXlab platform.

  • Experimental investigation and optimisation study of a direct thermosyphon heat-pipe evacuated tube solar water heater subjected to a northern maritime climate
    International Journal of Ambient Energy, 2010
    Co-Authors: David A.g. Redpath, Philip C. Eames
    Abstract:

    A proprietary heat-pipe Evacuated Tube Solar Water Heater (ETSWH) originally designed for collection of solar energy using forced fluid circulation was operated using thermosyphon fluid circulation. The thermal performance of this solar water heating system was monitored from October 2006 to June 2007. The ETSWH array was inclined with the expected Collector outlet at a higher datum level than the expected Collector Inlet to provide a hydrostatic pressure differential across the manifold. During the monitoring period it was observed that thermosyphon flow was not always in the expected direction, with flow reversal occurring when the Collector Inlet Temperature was greater than that of the outlet. When the evacuated tube solar water heater manifold was inclined at 1° to the horizontal, reverse fluid flow was observed to occur for 69% of the monitored diurnal periods. Diurnal reverse circulation lowers system efficiency by reducing thermal stratification in the hot water storage tank via convective entrainment and mixing. The thermal performance of the ETSWH was monitored continuously from January 2007 to June 2007 with the manifold inclined at 5° to the horizontal. Over this time period it was found that fluid flow reversal arose for 22% of the diurnal periods considered, resulting in a 47% improvement in diurnal storage efficiency compared to when the system had its manifold inclined at 1°. The long term diurnal storage efficiency of the optimised system inclined at 5” was measured as 66%.

  • DIURNAL REVERSE FLUID FLOW IN THERMOSYPHON EVACUATED TUBE SOLAR WATER HEATERS IN A NORTHERN MARITIME CLIMATE
    2007
    Co-Authors: David A.g. Redpath, Philip C. Eames
    Abstract:

    Proprietary evacuated tube solar water heaters have superior thermal performance in Northern Maritime climates compared with proprietary flat plate solar water heaters. Typically delivering 5-15% more thermal energy per annum, this is, however, achieved with higher capital costs. The adoption of thermosyphon fluid circulation compared with forced circulation systems allows the capital cost of solar water heating systems to be reduced, reliability increased and similar levels of performance to be achieved, for well designed systems. The thermal performance of an evacuated tube solar water heater system utilising thermosyphon fluid circulation subjected to Northern Maritime climatic conditions at the University of Ulster was monitored from the 23 rd of September to 21 st of November 2006. Measurements including Collector outlet Temperatures, mean bulk tank Temperatures, ambient Temperatures, and incident solar radiation levels were used to determine diurnal efficiency. The manifold of an evacuated tube solar water heater was inclined at 1˚: the manifold outlet being higher than the Inlet. During the monitoring period it appeared that thermosyphon flow did not always occur in the direction expected. It was deduced that flow reversal had occurred when the Collector Inlet Temperature was greater than that of the outlet. Comparison of the calculated diurnal efficiency for the days when flow reversal occurred with those when it did not indicated that flow reversal reduced the mean calculated diurnal efficiency by approximately 13%.

Guofeng Yuan - One of the best experts on this subject based on the ideXlab platform.

  • dynamic thermal performance prediction model for the flat plate solar Collectors based on the two node lumped heat capacitance method
    Solar Energy, 2016
    Co-Authors: Jie Deng, Guofeng Yuan, Chun Chang, Xudong Yang
    Abstract:

    Abstract Two-node lumped heat capacitance model of the flat-plate solar Collectors is derived strictly based on the concept of the Collector flow efficiency factor F ′ . It is found that the obtained first-order differential model turns out to be the amended quasi-dynamic test (QDT) model. The Collector dynamic response time constant τ d is identified referring to the first-order response system in automatic control theory. Then the dynamic thermal performance prediction model for the flat-plate solar Collectors on the basis of the amended QDT model is deduced using integral treatment within a small time interval in order to extend the thermal inertia correction model (TICM) to be fit for different conditions, such as moderate or intensive change rates of the Collector Inlet Temperature, wide-range ratios of the diffuse radiation to global radiation, different incidence angles, etc. Correlation between the presented prediction model and the TICM base on the steady-state test (SST) for the flat-plate solar Collectors is elucidated and the relation between the Collector dynamic response time constant τ d and the static time constant τ C is elaborated. Finally, experimental tests of both the steady-state tests and dynamic tests with a specific flat-plate solar air Collector are conducted to verify the performance of the proposed dynamic prediction model and corresponding parameters. It is verified that the presented prediction model in terms of the Collector dynamic response time constant τ d can accurately predict the dynamic thermal performances of the flat-plate solar air Collector under different conditions.

  • Validation of a simple dynamic thermal performance characterization model based on the piston flow concept for flat-plate solar Collectors
    Solar Energy, 2016
    Co-Authors: Jie Deng, Ming Yang, Zhu Xiaolin, Jianhua Fan, Guofeng Yuan, Zhifeng Wang
    Abstract:

    Abstract A simple dynamic characterization model of flat-plate solar Collectors based on the piston flow concept is used both to identify the Collector characteristic parameters and to predict the dynamic thermal performance. The heat transport time originally defined as (1 −  e −1 ) −1 τ C by Amrizal et al. (2012) for the model turns out to be the Collector static response time constant τ C by analytical derivation. The nonlinear least squares method is applied to determine the characteristic parameters of a flat-plate solar air Collector previously tested by the authors. Then the obtained parameters are used to predict the dynamic behavior of the Collector outlet Temperature. The model coefficients particularly c 3 in the simple dynamic characterization model are examined by the Collector dynamic prediction under variable meteorological conditions. Meanwhile, the prediction accuracy of the simple dynamic model based on the first-order difference method is compared to that of the numerical solution of the Collector ordinary differential equation (ODE) model using the fourth-order Runge-Kutta method. The improved thermal inertia model (TIM) on the basis of closed-form solution presented by Deng et al. (2016a) is also considered. The results show that the prediction performance of the simple dynamic model is nearly as accurate as the ODE numerical solution and the TIM by Deng et al. (2016a) except some special conditions such as sharply changed solar irradiance and Collector Inlet Temperature.

M. Suzuki - One of the best experts on this subject based on the ideXlab platform.

  • An analysis of solar heating systems that use vapor-compression cycles
    Solar Energy, 2003
    Co-Authors: M. Suzuki, Michael D. Devine, Hillel Kumin, D.b. Turkington
    Abstract:

    Abstract This paper analyzes the technical and economic performance of solar heating systems that use vapor-compression cycles, circulating a compressible fluid as the working fluid. With conventional solar heating systems that use water or as their working fluid, the Collector Inlet Temperature is equal to that of the storage outlet Temperature. Operating the system on a cold day can result in large thermal losses to the surroundings and, thus, low useful heat gains. A vapor-compression cycle may be attractive because it allows the Collector Inlet Temperature to be lowered so that the heat gain of the Collector can be increased. Such a system is simulated and a preliminary economic analysis performed. The results indicate that the vapor-compression system can collect almost 50% more solar energy than a conventional system if the Collector area of the two systems are the same.