Numerical Solution and Validation of a Dynamic Model of Solar Collectors Working With Varying Fluid Flow Rate

Hilmer, Frank; Vajen, Klaus; Ratka, A.; Ackermann, H.; Fuhs, W.; Melsheimer, O.

doi:10.1016/s0038-092x(98)00142-x

Cited by 33 publications

(10 citation statements)

References 19 publications

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“…A comprehensive validation of steady state and dynamic models for unglazed collectors is presented by Hilmer (1999). As a result commonly used models with one capacity show good agreement to measured data of 10 minute time steps for constant mass flow rates.…”

Section: Glazed and Unglazed Collectorsmentioning

confidence: 89%

Models of Sub-Components and Validation for the IEA SHC Task 44 / HPP Annex 38

Bertram¹,

Carbonell²,

Perers³

et al. 2012

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Section: Glazed and Unglazed Collectorsmentioning

confidence: 89%

Models of Sub-Components and Validation for the IEA SHC Task 44 / HPP Annex 38

Bertram¹,

Carbonell²,

Perers³

et al. 2012

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“…The first control strategy is bang-bang control. This strategy is commonly used in practice with mass flow rate values switching from 0.00001kg/s (during periods without solar radiation) to 0.1kg/s (during periods with solar radiation) [7,43]. The second control strategy is adapted from [7].…”

Section: Primary and Secondary Loop Mass Flow Ratesmentioning

confidence: 99%

Optimal flow control of a forced circulation solar water heating system with energy storage units and connecting pipes

2016

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Degree:Master of Engineering (Electrical Engineering)Keywords: Flat plate solar collector, flow rate optimization, maximum energy extraction, system thermal losses, thermal comfort.Solar water heating systems (SWHS) have fast become a suitable alternative to conventional water heating systems due to growing energy demands. A SWHS generally consists of a solar collector (which is used to convert solar radiation to heat), a water storage tank, and a flow control device such as a pump in the case of forced circulation SWHS. Extensive research and analysis on the operation and performance of these systems has been conducted, and results show that optimal flow control is an important factor that can be used to improve the performance and efficiency of SWHS.This study focuses on pump flow rate optimization for forced circulation SWHS with pipes.The system analyzed consists of an array of flat plate solar collectors, two storage tanks (one for the circulation fluid and one for the water), a heat exchanger, two pumps, and connecting pipes which are considered as one of the components of the SWHS so as to account for their thermal effects. The proposed model is developed using mainly the first and second laws of thermodynamics. The model is used to maximize the difference between the energy extracted from the solar collector and the combined sum of the energy extracted by the heat exchanger and corresponding energies used by the pumps in the primary and secondary loops. The objective function maximizes the overall system energy gain whilst minimizing the sum of the energy extracted by the heat exchanger and energy used by the corresponding pumps in the secondary loop to conserve the stored energy and meet the user requirement of water tank temperatures.The model is solved using the fmincon solver in MATLAB's optimization toolbox. When compared to other flow control techniques, in particular the most suitable energy efficient control strategy, the results of this study show a significant increase in the system's overall energy gain. The results also illustrate the effects of system pipe thermal losses for the different control strategies, hence highlighting the importance of developing a model that takes such losses into account so as to improve the overall accuracy of the model. Sonenergie-waterverwarmingstelsels (SWV) het vinnig 'n geskikte alternatief vir konvensionele waterverwarmingstelsels geword, weens die groeiende vraag na energie. 'n SWV bestaan gewoonlik uit 'n sonkollektor wat gebruik word om sonstraling om te skakel na hitte, 'n opgaartenk vir water, en 'n vloeibeheertoestel soos 'n pomp, in die geval van geforseerde sirkulasie SWV. Uitgebreide navorsing en ontleding op die werking en prestasie van hierdie stelsels is uitgevoer en die resultate toon dat die optimale vloeibeheer 'n belangrike faktor is wat gebruik kan word om die prestasie en doeltreffendheid van SWV verbeter. OPSOMMINGHierdie studie fokus op die optimering van die vloeitempo van 'n pomp vir geforseerde sirkulasie sonenergie-waterverwarmingste...

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“…[3][4][5][6][7][8][9][10][11][12]. Due to changing environmental (ambient air temperature, wind speed, and solar radiation) and operating conditions, the performance of the solar collector varies with time.…”

Section: Introductionmentioning

confidence: 99%

“…They concluded that the time constant for the nodes is on the order of several minutes. Hilmer et al [5] also use a distributed-node mathematical model (up to three nodes), but they use a solution procedure that can handle variable flow rates. Based on the fact that some of the heat resistances of a conventional flat-plate solar collector are smaller than others, Kamminga derived a 4-node mathematical model (cover, absorber, fluid, and insulation).…”

Section: Introductionmentioning

confidence: 99%

Flat-Plate Solar Collector in Transient Operation: Modeling and Measurements

Mueller

Abu-Mulaweh

2014

Journal of Thermal Science and Engineering Applications

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This paper describes a mathematical model for simulating the transient processes which occur in liquid flat-plate solar collectors. A discrete nodal model that represents the flat-plate solar collector's layers and the storage tank is employed. The model is based on solving a system of coupled differential equations which describe the energy conservation for the glass cover, air gap, absorber, fluid, insulation, and the storage tank. Inputs to the model include the time-varying liquid flow rate, incident solar radiation, and the ambient air temperature, as well as the volume of liquid in the storage tank and initial temperature of the system. The system of differential equations is solved iteratively using an implicit, finite-difference formulation executed with MATLAB software. In order to verify the proposed method, an experiment was designed and conducted on different days with variable ambient conditions and flow rates. The comparison between the computed and measured results of the transient fluid temperature at the collector outlet shows good agreement. The proposed method is extremely general and flexible accounting for variable ambient conditions and flow rates and allowing for a geometrical and thermophysical description of all major components of the solar collector system, including the storage tank. The validated, general model is suitable to investigate the effectiveness of various components without the necessity of carrying out experimental work, and the flexible computational scheme is useful for transient simulations of energy systems.

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Numerical Solution and Validation of a Dynamic Model of Solar Collectors Working With Varying Fluid Flow Rate

Cited by 33 publications

References 19 publications

Models of Sub-Components and Validation for the IEA SHC Task 44 / HPP Annex 38

Models of Sub-Components and Validation for the IEA SHC Task 44 / HPP Annex 38

Optimal flow control of a forced circulation solar water heating system with energy storage units and connecting pipes

Flat-Plate Solar Collector in Transient Operation: Modeling and Measurements

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