scholarly journals Thermal Performance Improvement of Solar Parabolic Dish System Using Modified Spiral Coil Tubular Receiver

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Rajkumar Malviya ◽  
Prashant V. Baredar ◽  
Anil Kumar
Keyword(s):  
Thermal Performance ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Anodized Aluminum ◽  
Innovative Design ◽  
Spiral Coil ◽  
Parabolic Dish ◽  
Turbulence Effect ◽  
Solar Thermal Applications

The present research intends to design an efficient receiver for solar thermal applications with a solar dish concentrator system. Thermal and dynamic analysis is carried out for different convolutions of a spiral coil, and experiments are performed for testing the modified absorber. Experimental results are validated for the spiral absorber with numerical results. Three receivers of different numbers of convolutions are analyzed, and simulation steps are performed for these receivers to make improvements in the system efficiency. Finally, 5 convolutions of a spiral coil tubular absorber are taken for the modified design of the system. Absorber position for every spiral convolution is kept at the focus of the concentrated solar dish collector to achieve maximum efficiency. Material used for the reflective surface is anodized aluminum and copper for the absorber. The diameter of the aperture for the parabolic dish collector is 1.4 m. The maximum absorber temperature for May month comes out to be 296°C, and the maximum working fluid outlet temperature is found to be 294.2°C which is near to simulating temperature of 289.59°C and 288.15°C, respectively. This innovative design of the absorber consists of a feature of a 5 mm extension to the spiral tube at the exit and entry; hence, the turbulence effect could be overcome. Experimental thermal efficiency was found the highest (i.e., η th max = 75.98 % ) for May. This work emphasizes on improving thermal performance by obtaining optimum absorber size using convolution strategy. Investigation of 5 convolutions of spiral coil tubular absorber with extended ends for obtaining optimum performance than existing work is the superiority of this work.

scholarly journals Heat Transfer Augmentation of Concentrated Solar Absorber Using Modified Surface Contour

2021 ◽  
Vol 11 (1) ◽  
pp. 24-33
Author(s):  
Ramalingam Senthil ◽  
Arvind Chezian ◽  
Zackir Hussain Ajmal Arsath
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Cavity Surface ◽  
Solar Absorbers ◽  
Surface Contour ◽  
Parabolic Dish ◽  
Plain Surface ◽  
Surface Modified

This work aims to compare the cavity surface contour’s thermal performance to that of the solar absorber’s plain surface contour for Scheffler type parabolic dish collectors. The absorber is tested for the temperature range up to 600°C without working fluid and 180°C with the working fluid. The modified absorber surface's thermal performance is compared with the flat surface absorber with and without heat transfer fluid. The peak temperature reached by the surface modified absorber (534°C) is about 8.6% more than that of the unmodified absorber (492°C) during an outdoor test without fluid. The energy efficiency of cavity surface absorber and plain surface absorber are 67.65% and 61.84%, respectively. The contoured cavity surface produces a more uniform temperature distribution and a higher heat absorption rate than the plain surface. The results are beneficial to the design of high-temperature solar absorbers for concentrated solar collectors.

scholarly journals Experimental Study of Thermal Performance of One-Ended Evacuated Tubes for Producing Hot Air

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Ashish Kumar ◽  
Sanjeev Kumar ◽  
Utkarsh Nagar ◽  
Avadhesh Yadav
Keyword(s):  
Thermal Performance ◽  
Temperature Difference ◽  
Air Flow ◽  
Climatic Conditions ◽  
Working Fluid ◽  
Outlet Temperature ◽  
Flow Rates ◽  
Solar Air Collector ◽  
Evacuated Tubes ◽  
Evacuated Tube

The thermal performance of an evacuated tube solar air collector is experimentally investigated at different air flow rates. Air is used as a working fluid in experimental setup and tested in Indian climatic conditions. The evacuated tube solar air collector consists of fifteen evacuated tubes and manifold channel. The manifold channel consists of a hollow pipe (square pipe) in centre through which air flows. The temperature difference and efficiency are studied with different air flow rates. The reflectors are used to enhance the performance of evacuated tubes solar air collector. It is observed that in case of reflector evacuated tube solar air collector gives higher outlet temperature and temperature difference and has better thermal performance as compared to the case without reflector. The maximum outlet temperature and temperature difference of air are found to be 97.4°C and 74.4°C at a flow rate of 6.70 kg/hr.

scholarly journals Heat Transfer Augmentation of Concentrated Solar Absorber Using Modified Surface Contour

2021 ◽  
Vol 11 (1) ◽  
pp. 24-33
Author(s):  
Ramalingam Senthil ◽  
Arvind Chezian ◽  
Zackir Hussain Ajmal Arsath
Keyword(s):  
Heat Transfer ◽  
Thermal Performance ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Cavity Surface ◽  
Solar Absorbers ◽  
Surface Contour ◽  
Parabolic Dish ◽  
Plain Surface ◽  
Surface Modified

This work aims to compare the cavity surface contour’s thermal performance to that of the solar absorber’s plain surface contour for Scheffler type parabolic dish collectors. The absorber is tested for the temperature range up to 600°C without working fluid and 180°C with the working fluid. The modified absorber surface's thermal performance is compared with the flat surface absorber with and without heat transfer fluid. The peak temperature reached by the surface modified absorber (534°C) is about 8.6% more than that of the unmodified absorber (492°C) during an outdoor test without fluid. The energy efficiency of cavity surface absorber and plain surface absorber are 67.65% and 61.84%, respectively. The contoured cavity surface produces a more uniform temperature distribution and a higher heat absorption rate than the plain surface. The results are beneficial to the design of high-temperature solar absorbers for concentrated solar collectors.

Experimental study of thermohydraulic characteristics and irreversibility analysis of novel axial corrugated tube with spring tape inserts

2020 ◽  
Vol 92 (3) ◽  
pp. 30901
Author(s):  
Suvanjan Bhattacharyya ◽  
Debraj Sarkar ◽  
Ulavathi Shettar Mahabaleshwar ◽  
Manoj K. Soni ◽  
M. Mohanraj
Keyword(s):  
Heat Transfer ◽  
Experimental Study ◽  
Thermal Performance ◽  
Working Fluid ◽  
The Novel ◽  
Heat Exchanger Tube ◽  
Heat Transfer Augmentation ◽  
Corrugated Tube ◽  
The Impact ◽  
Exchanger Tube

The current study experimentally investigates the heat transfer augmentation on the novel axial corrugated heat exchanger tube in which the spring tape is introduced. Air (Pr = 0.707) is used as a working fluid. In order to augment the thermohydraulic performance, a corrugated tube with inserts is offered. The experimental study is further extended by varying the important parameters like spring ratio (y = 1.5, 2.0, 2.5) and Reynolds number (Re = 10 000–52 000). The angular pitch between the two neighboring corrugations and the angle of the corrugation is kept constant through the experiments at β = 1200 and α = 600 respectively, while two different corrugations heights (h) are analyzed. While increasing the corrugation height and decreasing the spring ratio, the impact of the swirling effect improves the thermal performance of the system. The maximum thermal performance is obtained when the corrugation height is h = 0.2 and spring ratio y = 1.5. Eventually, correlations for predicting friction factor (f) and Nusselt number (Nu) are developed.

INFLUENCE OF WORKING FLUID ON THERMAL PERFORMANCE OF THERMOSYPHONS FOR APPLICATION IN HIGH PRESSURE VACUUM TUBE SOLAR COLLECTORS

2020 ◽  
Author(s):  
Guilherme Antonio Bartmeyer ◽  
Victor Vaurek Dimbarre ◽  
Pedro Leineker Ochoski Machado ◽  
PAULO HENRIQUE DIAS DOS SANTOS ◽  
Thiago Antonini Alves
Keyword(s):  
High Pressure ◽  
Thermal Performance ◽  
Working Fluid ◽  
Solar Collectors ◽  
Vacuum Tube

scholarly journals Parametric CFD Thermal Performance Analysis of Full, Medium, Half and Short Length Dimple Solar Air Tube

2021 ◽  
Vol 13 (11) ◽  
pp. 6462
Author(s):  
Mir Waqas Alam ◽  
Basma Souayeh
Keyword(s):  
Thermal Performance ◽  
Energy Transport ◽  
Hydraulic Performance ◽  
Short Length ◽  
Working Fluid ◽  
Solar Air Heater ◽  
Hydraulic Characteristics ◽  
Height Ratio ◽  
Pitch Ratio ◽  
Full Medium

In the present decade, research regarding solar thermal air heaters (SAHs) has noticed a continuous progression in thermo-hydraulic performance augmentation approaches. There now exists a wide variety of thermo-hydraulic performance augmentation approaches and researchers have designated various structures. Nevertheless, there seems to be no generalization to any of the approaches employed. The present numerical investigation reports on the thermo-hydraulic characteristics and thermal performance for flow through a varied length (full, medium, half, and short length) dimple solar air heater (SAH) tube. The study highlights recent developments on enhanced tubes to augment heat transfer in SAH. The influence of different length ratio, dimple height ratio (H), and pitch ratio (s) on thermo-hydraulic characteristics have been investigated in the Reynolds number (Re) range from 5000 to 25,000. Air is used as the working fluid. The commercial software ANSYS Fluent is used for simulation. The shear stress transport (SST) model is used as the turbulence model. Thermal energy transport coefficient is increased in the full-length dimple tube (FLDT), compared to the medium-length dimple tube (MLDT), half-length dimple tube (HLDT) and short-length dimple tube (SLDT). Similarly, the pitch ratio (s) has more influence on Nusselt number (Nu) compared to the dimple height ratio (H). The friction factor decreases with an increase in pitch ratio. Nu increases and f decreases with increasing Re for all combinations of H and s. Low s and higher H yields high enhancement of HT and PD. Integration of artificial roughness on the tube increases the values of Nu and f by 5.12 times and 77.23 times for H = 0.07, s = 1.0 at Re value of 5000 and 25,000, respectively, in regard to the plain tube. For all the tested cases, the thermo-hydraulic performances (η) are greater than unity.

Dynamic Optimization of an Evaporator by a Nonlinear Model Predictive Controller for Operation at Modular Micro Rectification

2009 ◽  
Author(s):  
Ralf Knauss ◽  
Lukas E. Wiesegger ◽  
Rolf Marr ◽  
Ju¨rgen J. Brandner
Keyword(s):  
Mass Flow ◽  
Dynamic Optimization ◽  
Nonlinear Model ◽  
Process Models ◽  
Maximum Efficiency ◽  
Local Optimum ◽  
Outlet Temperature ◽  
Time Step ◽  
Unit Operations ◽  
Vapor Fraction

Arranging micro-structured equipment to plants whole production processes can be realized with maximum efficiency in tightest space. Unit operations are thereby represented as individual functional modules in shape of micro devices. In a multi unit operation plant a correspondingly large number of manipulable variables have to be coordinated. Due to the design of micro-scaled devices plants form sophisticated systems, while for a fully optimized control still no common satisfying solutions exist. A system of modular, discontinuous phase contacting, micro rectification consists of unit operations heating, cooling, mixing and separating. Heat exchangers, mixers and cyclones for phase separation can be arranged to a counter-current rectification system with maximum mass-transfer efficiency every unit. Operating an electrical heated evaporator for modular rectification purposes a strong coupling of mass flow with the vapor fraction and the outlet temperature can be observed [4]. Operating at a predefined state for mass flow, temperature and vapor fraction may only be possible with difficulties using traditional methods of linear control technology. For dynamic optimization of the multivariable micro-structured evaporator principle of Nonlinear Model Predictive Control (NMPC) was generically formulated in C++ and implemented to LABVIEW 7. Every discrete time step an objective function is generated from nonlinear process models in the form of grouped NARX-polynomials. Optimal sequences of control actions for plant operation are evolved. The resulting constrained cost function is non-convex making detection of relative local optimum a difficult task. This obstacle can be gone around using heuristic optimization algorithm in combination with traditional techniques. Based on experimental results it was demonstrated that NMPC keeps the coupled variables mass flow and temperature energy saving with minimal control activity in the entire two-phase region on their set-points.

scholarly journals Thermodynamic Analysis of Irreversible Desiccant Systems

Entropy ◽  
2018 ◽  
Vol 20 (8) ◽  
pp. 595 ◽  
Author(s):  
Niccolò Giannetti ◽  
Seiichi Yamaguchi ◽  
Andrea Rocchetti ◽  
Kiyoshi Saito
Keyword(s):  
Control Volume ◽  
Ideal Gas ◽  
Maximum Efficiency ◽  
Working Fluid ◽  
Specific System ◽  
Equilibrium Relationship ◽  
Working Medium ◽  
Vapour Mixture ◽  
Energy Balances ◽  
Relationship Of

A new general thermodynamic mapping of desiccant systems’ performance is conducted to estimate the potentiality and determine the proper application field of the technology. This targets certain room conditions and given outdoor temperature and humidity prior to the selection of the specific desiccant material and technical details of the system configuration. This allows the choice of the operative state of the system to be independent from the limitations of the specific design and working fluid. An expression of the entropy balance suitable for describing the operability of a desiccant system at steady state is obtained by applying a control volume approach, defining sensible and latent effectiveness parameters, and assuming ideal gas behaviour of the air-vapour mixture. This formulation, together with mass and energy balances, is used to conduct a general screening of the system performance. The theoretical advantage and limitation of desiccant dehumidification air conditioning, maximum efficiency for given conditions constraints, least irreversible configuration for a given operative target, and characteristics of the system for a target efficiency can be obtained from this thermodynamic mapping. Once the thermo-physical properties and the thermodynamic equilibrium relationship of the liquid desiccant mixture or solid coating material are known, this method can be applied to a specific technical case to select the most appropriate working medium and guide the specific system design to achieve the target performance.

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