An Exergy-Based Metric for Evaluating Solar Thermal Absorber Technologies for Gas Heating

2011 ◽  
Author(s):  
Maritza Ruiz ◽  
Van P. Carey
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Loss Factor ◽  
Performance Metrics ◽  
Solar Thermal ◽  
Pumping Power ◽  
Central Receiver ◽  
Gas Heating ◽  
Goodness Factor ◽  
Solar Receiver

The energy conversion effectiveness of the central receiver absorber in concentrating solar thermal power systems is dictated primarily by heat losses, material temperature limits, and pumping power losses. To deliver concentrated solar energy to a gas for process heat applications or gas cycle power generation, there are a wide variety of compact heat exchanger finned surfaces that could be used to enhance the convective transfer of absorbed solar energy to the gas stream flowing through the absorber. In such circumstances, a key design objective for the absorber is to maximize the heat transfer thermodynamic performance while minimizing the pumping power necessary to drive the gas flow through the fin matrix. This paper explores the use of different performance metrics to quantify the combined heat transfer, thermodynamic and pressure loss effectiveness of enhanced fins surfaces used in solar thermal absorbers for gas heating. Previously defined heat exchanger performance metrics, such as the “goodness factor”, are considered, and we develop and explore the use of a new metric, the “loss factor”, for determining the preferred enhanced fin matrix surfaces for concentrated solar absorbers. The loss factor, defined as the normalized exergy loss in the receiver, can be used for nondimensional analysis of the desirable qualities in an optimized solar receiver design. In comparison to previous goodness factor methods, the loss factor metric has the advantage that it quantifies the trade-off between trying to maximize the solar exergy transferred to the gas (high heat transfer rate and delivery at high temperature) and minimizing the pumping exergy loss. In this study, the loss factor is used to compare current solar receiver designs, and designs that use a variety of available plate-finned compact heat transfer surfaces with known Colburn factor (j) and friction factor (f) characteristics. These examples demonstrate how the loss factor metric can be used to design and optimize novel solar central receiver systems, and they indicate fin matrix surfaces that are particularly attractive for this type of application.

Central Receiver System Solar Power Plant Using Molten Salt as Heat Transfer Fluid

2008 ◽  
Vol 130 (2) ◽  
Author(s):  
J. Ignacio Ortega ◽  
J. Ignacio Burgaleta ◽  
Félix M. Téllez
Keyword(s):  
Heat Transfer ◽  
Power Generation ◽  
Molten Salt ◽  
Thermal Power ◽  
Solar Thermal ◽  
Heat Transfer Fluid ◽  
Solar Thermal Power ◽  
Central Receiver ◽  
Spanish Legislation ◽  
Solar Thermal Power Generation

Of all the technologies being developed for solar thermal power generation, central receiver systems (CRSs) are able to work at the highest temperatures and to achieve higher efficiencies in electricity production. The combination of this concept and the choice of molten salts as the heat transfer fluid, in both the receiver and heat storage, enables solar collection to be decoupled from electricity generation better than water∕steam systems, yielding high capacity factors with solar-only or low hybridization ratios. These advantages, along with the benefits of Spanish legislation on solar energy, moved SENER to promote the 17MWe Solar TRES plant. It will be the first commercial CRS plant with molten-salt storage and will help consolidate this technology for future higher-capacity plants. This paper describes the basic concept developed in this demonstration project, reviewing the experience accumulated in the previous Solar TWO project, and present design innovations, as a consequence of the development work performed by SENER and CIEMAT and of the technical conditions imposed by Spanish legislation on solar thermal power generation.

3D Computational Analysis of Thermal and Hydraulic Performance of Louvered Fin Heat Exchanger With Variable Louver Angle and Louver Pitch

2016 ◽  
Author(s):  
Abdulkerim Okbaz ◽  
Ali Pınarbaşı ◽  
Ali Bahadır Olcay
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Pressure Drop ◽  
Flow Characteristics ◽  
Hydraulic Performance ◽  
Double Row ◽  
Louvered Fin ◽  
Goodness Factor ◽  
Fluid Flow Characteristics ◽  
Louvered Fins

In the present study, 3-D numerical simulations on heat and fluid flow characteristics of double-row multi-louvered fins heat exchanger are carried out. The heat transfer improvement and the corresponding pressure drop amounts were investigated depending on louver angles in the range of 20° ≤θ≤ 30°, louver pitches of Lp = 2,7mm, 3,5mm and 3,8mm and frontal velocities of Uin between 1.22 m/s and 3 m/s. The results are reported in terms of Colburn j-factor, Fanning friction factor f and area goodness factor j/f based on louver angle, louver pitch and Reynolds number. To understand local behavior of flow around louvered fins and heat exchanger tubes, flow visualization results of velocity vectors and stream-lines with temperature counters are presented. It is investigated that increasing louver angle enhances convective heat transfer while hydraulic performance decreases due to increased pressure drop. The flow noticeably behaves louver directed for all louver angles The flow can easily travel between different fins. This case study has been done to design and manufacture an industrial louver fin heat exchanger.

scholarly journals Optimization of a New Design of Molten Salt-to-CO2 Heat Exchanger Using Exergy Destruction Minimization

Entropy ◽  
2020 ◽  
Vol 22 (8) ◽  
pp. 883
Author(s):  
María José Montes ◽  
José Ignacio Linares ◽  
Rubén Barbero ◽  
Beatriz Yolanda Moratilla
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Molten Salt ◽  
High Heat ◽  
Exergy Destruction ◽  
Solar Thermal Energy ◽  
Heat Exchanger Design ◽  
Central Receiver ◽  
High Heat Transfer ◽  
Supercritical Phase

One of the ways to make cost-competitive electricity, from concentrated solar thermal energy, is increasing the thermoelectric conversion efficiency. To achieve this objective, the most promising scheme is a molten salt central receiver, coupled to a supercritical carbon dioxide cycle. A key element to be developed in this scheme is the molten salt-to-CO2 heat exchanger. This paper presents a heat exchanger design that avoids the molten salt plugging and the mechanical stress due to the high pressure of the CO2, while improving the heat transfer of the supercritical phase, due to its compactness with a high heat transfer area. This design is based on a honeycomb-like configuration, in which a thermal unit consists of a circular channel for the molten salt surrounded by six smaller trapezoidal ducts for the CO2. Further, an optimization based on the exergy destruction minimization has been accomplished, obtained the best working conditions of this heat exchanger: a temperature approach of 50 °C between both streams and a CO2 pressure drop of 2.7 bar.

Fluid-Solid Coupled Simulation of a Novel Platelet Heat Exchanger Used in Solar Thermal Thruster

2014 ◽  
Vol 598 ◽  
pp. 281-287 ◽  
Author(s):  
Bao Yu Xing ◽  
Min Chao Huang ◽  
Mou Sen Cheng ◽  
Kun Liu
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Transfer Characteristic ◽  
Solar Thermal ◽  
Coupled Heat Transfer ◽  
Aerospace Applications ◽  
Heat Transfer Efficiency ◽  
Transfer Method ◽  
Solar Thermal Propulsion ◽  
Solar Thermal System

Solar thermal propulsion is a potential technology in aerospace applications, and it is a significant issue to improve the heat transfer efficiency of the solar thermal thruster. This paper proposes a novel platelet configuration to be used in the heat exchanger core, which is the most important component of solar thermal system. The platelet passage can enhance the heat transfer between the propellant and the hot core heated by the concentrated sunlight. Based on fluid-solid coupled heat transfer method, the paper utilized the platelet heat transfer characteristic to simulate the heat transfer and flow field of the platelet passage.The simulation result shows that the propellant can be heated to the design temperature of 2300K in the platelet passage of the solar thermal propulsion system, and the fluid-solid coupled method can solve the heat transfer in the platelet structure more precisely.

Air-Side Heat-Transfer Enhancement by a New Winglet-Type Vortex Generator Array in a Plain-Fin Round-Tube Heat Exchanger

2010 ◽  
Vol 132 (7) ◽  
Author(s):  
J. He ◽  
L. Liu ◽  
A. M. Jacobi
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Vortex Generator ◽  
Round Tube ◽  
Number Range ◽  
Tube Heat Exchanger ◽  
Large Pair ◽  
Goodness Factor ◽  
The Impact ◽  
Heat Transfer Improvement

The impact of a vortex-generation technique for air-side heat-transfer improvement is experimentally investigated through full-scale wind-tunnel testing of a plain-fin round-tube heat exchanger under dry-surface conditions. Inspired by the formation locomotion of animals in nature, a new vortex generator (VG) array deployed in a “V” is proposed in the present work, aiming to create constructive interference between vortices. The array is composed of two delta-winglet pairs and placed at an attack angle of 10 deg or 30 deg. Its effectiveness is compared with a baseline configuration and two conventional single-pair designs placed at 30 deg, a small pair with half the area of the array and a large pair with the same area as the array. The frontal air velocity considered ranges from 2.3 m/s to 5.5 m/s, corresponding to a Reynolds number range based on the hydraulic diameter of 1400–3400. The experimental results show little impact of the 10 deg array and a moderate heat-transfer improvement of up to 32% for the small pair, both introducing additional pressure loss of approximately 20–40%. For the 30 deg array and the large pair, similar augmentation of 25–55% in air-side heat-transfer coefficient is obtained accompanied by average pressure drop penalties of 90% and 140%, respectively. Performance evaluation using the criteria of the modified area goodness factor and the volume goodness factor indicates the superiority of the heat exchanger enhanced by the 30 deg array among all the investigated VGs. The VG array is found more effective at comparatively low Reynolds numbers, representative of many heating, ventilation, air-conditioning, and refrigeration applications and compact heat-exchanger designs.

Convective Heat Transfer in a Helical Coil Solar Thermal Collector

2010 ◽  
Author(s):  
Allan May ◽  
Tadhg S. O’Donovan
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Three Dimensional ◽  
Solar Thermal ◽  
Helical Coil ◽  
Dean Number ◽  
Flux Boundary Condition ◽  
Uniform Wall ◽  
Flow Variables ◽  
Coil Heat Exchanger

Three dimensional solar concentrators can achieve concentration ratios in excess of 100 and optical efficiencies in excess of 95% throughout the day without the need for tracking. A helical coil heat exchanger has been designed and investigated numerically as the receiver for this solar thermal application. A computational fluid dynamics (CFD) model of a laminar flow in the heat exchanger was developed in ANSYS CFX and a uniform wall flux boundary condition applied to the outer surface. Due to the curvature of the pipe, Dean Vortices were setup within the flow that substantially increased the overall heat transfer to the solar receiver without significantly increasing the pressure drop across the heat exchanger. A full parametric study is conducted to investigate the effects of geometric properties (dimensionless pitch, coil radius etc) and flow variables (Reynolds number, Dean number, Helical number). The variation of the circumferentially averaged heat transfer coefficient with distance along the heat exchanger is reported. It has been shown that the flow is fully developed after approximately 3.5 turns of the heat exchanger coil and will remain stable throughout the remainder of the heat exchanger.

scholarly journals Numerical Heat Transfer Investigation in a Solar Receiver Heat Exchanger Channel with Punched Elliptical-Winglet Vortex Generators

2021 ◽  
Vol 25 (10) ◽  
pp. 105-114
Author(s):  
Pitak Promthaisong ◽  
Pongjet Promvonge ◽  
Chitakorn Khanoknaiyakarn ◽  
Sompol Skullong
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Vortex Generators ◽  
Numerical Heat Transfer ◽  
Solar Receiver

Enhanced Thermal-Hydraulic Performance of a Wavy-Plate-Fin Compact Heat Exchanger: Effect of Corrugation Severity

2006 ◽  
Author(s):  
Arun Muley ◽  
Joseph B. Borghese ◽  
Steve L. White ◽  
Raj M. Manglik
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Aspect Ratio ◽  
Control Volume ◽  
Three Dimensional ◽  
Compact Heat Exchanger ◽  
Flow Recirculation ◽  
Periodic Boundary Layer ◽  
Transfer Behavior ◽  
Goodness Factor

Enhanced forced-convective heat transfer behavior of air flows (Pr ~ 0.7) in a compact heat exchanger with three-dimensional, sinusoidal-wavy-plate fins is investigated both experimentally and computationally. Plate-fins with three different corrugation aspect ratio γ = (2A/L) = 0.0667, 0.1333, and 0.2667 are explored. Experimental j and f measurements are presented for flow rates in the range 500 < Re < 5000. Computational results, based on control-volume techniques, are obtained for periodically-fully-developed flows with 10 ≤ Re ≤ 1000. The numerically simulated local temperature and flow field map shows the complex influence of corrugation aspect-ratio γ, and the concomitant j and f predictions are in good agreement with experimental measurements. Both j and f increase with γ to reflect the relatively stronger flow recirculation in the wall-trough regions, and spatially more frequent periodic boundary-layer disruptions upstream of the corrugation peaks that enhance heat transfer in plate-fin channels. The relative enhancement, as measured by the Area Goodness Factor (j/f), however is found to be highest with γ = 0.0667.

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