Two-phase flow modelling of a solar concentrator applied as ammonia vapor generator in an absorption refrigerator

Ortega, N.; Garcı́a-Valladares, O.; Best, R.; Gómez, V.H.

doi:10.1016/j.renene.2007.11.016

Cited by 20 publications

(15 citation statements)

References 19 publications

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“…Experimental values are previewed along with their associated error bars. A good agreement to within ±10% occurs between our numerical results and the experimental ones all over the plotted range, better than the numerical model used by Santos-Gonzá lez et al and discussed by Ortega et al [16].…”

Section: Validationsupporting

confidence: 87%

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Effect of Using Twisted Tape Inserts on Performance of Compound Parabolic Concentrators

Eldakamawy¹,

hanafi²,

Kassem³

2015

JOCET

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Abstract-Modeling of a compound parabolic collector with bare tubular absorber was performed, regarding its geometrical, optical and thermal features. The developed model was validated via two recent experiments showing accepted agreement with the experimental results. After that we studied the effect of inserting different configurations of twisted tapes in the absorber tube on the thermal efficiency, the pumping power and the thermal performance factor. It was concluded that inserting twisted tapes is much favorable when the flow was laminar rather than being in transition or turbulent regimes.Index Terms-Compound parabolic concentrators, heat transfer enhancement, modeling, swirl flow.

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Section: Validationsupporting

confidence: 87%

“…where is the Stefan-Boltzmann, the effective emmissivity between the absorber and the cover is [8] , / = ̅ 1− 2̅ (16) Similarly the radiation exchange between the absorber and the reflector, and between the reflector and the cover, respectively are…”

Section: Thermal Analysismentioning

confidence: 99%

Effect of Using Twisted Tape Inserts on Performance of Compound Parabolic Concentrators

Eldakamawy¹,

hanafi²,

Kassem³

2015

JOCET

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“…The initial conditions introduced in the numerical model were the geometry of the CPC, the boundary conditions, the location (latitude and longitude), date and time of the test. With this information, the model can predict the increment of temperature between the inlet and outlet of the CPC, the energy gain by the transport fluid, efficiency and pressure drop as well as other flow variables, along the system [7].…”

Section: Numerical Modelmentioning

confidence: 99%

Design and Evaluation of a Compound Parabolic Concentrator for Heat Generation of Thermal Processes

et al. 2014

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A solar concentrator was designed using a detailed one-dimensional numerical model previously developed to describe the heat and fluid-dynamic behavior inside a compound parabolic concentrator (CPC). The governing equations (continuity, momentum and energy) inside the CPC absorber tube, together with the energy equation in the tube wall and the thermal analysis in the solar concentrator were solved. Two CPC geometries were proposed based on numerical simulation and commercial availability of materials; one of this is tested in this work. A ray tracing analysis was made for this configuration to quantify optical energy losses due to truncation. Then, a module with aperture area of 2.1 m 2 was constructed. The module has 12 CPCs, each one with real concentration ratio of 1.8, acceptance angle of 30°, and a tubular receiver covered by a selective surface. An experimental setup was designed and built to test different operational conditions for the module; for example mass flow rate and inlet temperature. The experimental setup has the following elements: The CPC, two water storage tanks, a recirculation pump, and a support structure that allows positioning the CPC at different angles. Experimental results obtained using the Mexican standard NMX-ES-001- NORMEX-2005 show that this technology could be able to supply stable temperatures for industrial processes. However, a new prototype is going to be developed and constructed in order to improve some manufacturing errors detected in these experimental tests. NomenclatureA Cross section area [m 2 ] e Specific energy (h+v 2 /2+gz sin ) [J/kg] g Acceleration due to gravity force [m/s 2 ] h Enthalpy [J/kg] I Solar irradiance [W/m 2 ] m Mass [kg] . m Mass flow rate [kg/s] p Perimeter [m] P Pressure [Pa] I. Santos-González et al. / Energy Procedia 57 ( 2014 ) 2956 -2965 2957 . q Heat flow per unit area [W/m 2 ] Q Heat energy [W] t Time [s] T Temperature [°C] v Velocity [m . s -1 ] x g Vapour quality [dimensionless] Greek letters P Pressure drop [Pa] T Temperature difference [°C] z Axial discretization step [m] Efficiency [dimensionless] Inclination angle of absorber tube [degree] Density [kg/m 3 ] w

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“…Nevertheless, the main disadvantage of the above proposed systems is the thermal loss due to the indirect coupling between the solar array and the refrigeration cycle, in addition to the higher initial investment imposed by the increasing number of the components. Ortega et al [6] included a compound parabolic concentrator (CPC) coupled directly with a single effect solar absorption system with a capacity of 3.8 kW, in order to reduce the thermal losses and the number of the components. The reported system has a theoretical CPC efficiency of 0.46 and a COP in the cycle of 0.45 that results in a global efficiency of 0.21.…”

Section: Introductionmentioning

confidence: 99%

Numerical simulation and design of a parabolic trough solar collector used as a direct generator in a solar-GAX cooling cycle?

Sauceda¹,

Velázquez²,

Garcı́a-Valladares

et al. 2011

J Mech Sci Technol

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In this work, a solar parabolic trough collector (PTC) has been dimensioned and its technical feasibility has been evaluated in order to be used as ammonia direct vapor generator in an advanced absorption air-cooled Solar-GAX cycle of 10.6 kW cooling capacity. A detailed numerical simulation model that takes into account the geometry and the optical, thermal and fluid dynamic behavior of the PTC has been developed. The model has been solved in order to reach minimal thermal losses through the PTC, and maximum coefficient of performance (COP) of the Solar-GAX cycle. Under design conditions, the solar PTC efficiency, the COP of the Solar-GAX cycle and the global efficiency of the system were 0.62, 0.87 y and 0.54 respectively. The calculated efficiency is 25.5 % higher than that provided by a single effect water-lithium bromide cycle coupled in an indirect form with a solar PTC system.

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Two-phase flow modelling of a solar concentrator applied as ammonia vapor generator in an absorption refrigerator

Cited by 20 publications

References 19 publications

Effect of Using Twisted Tape Inserts on Performance of Compound Parabolic Concentrators

Effect of Using Twisted Tape Inserts on Performance of Compound Parabolic Concentrators

Design and Evaluation of a Compound Parabolic Concentrator for Heat Generation of Thermal Processes

Numerical simulation and design of a parabolic trough solar collector used as a direct generator in a solar-GAX cooling cycle?

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