Solar Air Heater Channel Research Articles

Fluid Flow and Thermal Characteristics of an Obtuse-Angled Trapezoidal Solar Air Heater Channel With Corner Modifications and Ribs on Absorber Plates

Fluid Flow and Thermal Characteristics of an Obtuse-Angled Trapezoidal Solar Air Heater Channel With Corner Modifications and Ribs on Absorber Plates

Computational insights into the thermal performance enhancement of solar air heater channel through metal foam integration

Computational insights into the thermal performance enhancement of solar air heater channel through metal foam integration

CFD analysis of artificially roughened solar air heater: a comparative study of C-Shape, reverse C-Shape, and reverse R-Shape roughness element

Solar Air Heater (SAH) serves as a pivotal device for converting solar radiation into heat applications. This study focuses on enhancing the performance of SAH through modifications to the absorber surface by introducing ribs as artificial roughness. A two-dimensional CFD analysis investigates the impact of C-shape, reverse C-shape, and reverse R-shape ribs on thermal and hydraulic performance within the SAH channel. RNG (k-ϵ) turbulence model is employed for numerical simulation and model accuracy is validated against established correlations and literature results. The numerical analysis involves the designing and modelling of the SAH using a constant pitch ratio (P/e) of 14.285 and a height ratio (e/D) of 0.021. The Reynolds number (Re) from 4000 to 18000 was considered for the present study. The result reveals that the present rib geometries significantly enhance heat transfer and fluid mixing, leading to substantial improvements in Nusselt number (Nu) and friction factor (f) by 2.5 to 3.3 times and 2.8 to 5.05 times respectively over smooth duct SAH. The C-shape rib configuration attains the highest Thermohydraulic Performance Factor (THPF) at approximately 2.0078 for a Re of 4000 over reverse C-shape, and reverse R-shape ribs.

Flow and thermal behavior of solar air heater with grooved roughness

A simple and eco-friendly solar air heater (SAH) converts renewable solar energy into useful thermal energy. The implementation of roughness on the absorber plate of a solar air heater improves its air heating capability. The hot air thus produced is used in different applications such as agricultural, dairy, food processing, and cement industries. Towards that, a 2D numerical study is carried out with rectangular groove as a roughness with the RNG k−Ɛ turbulent model. The study has been carried out to find a SAH with higher performance. Two thermodynamic models are adopted to identify and qualify the best channel. The performance of the best SAH channel has been identified by the highest thermal enhancement factor (TEF) and to increase the exergetic ratio (Ɛth). A detailed study of introducing rectangular groove on heat transfer, pressure drop, thermal enhancement factor (TEF) and exergetic ratio (Ɛth) is conducted, by varying the geometrical parameters of rectangular grooves in the range of Re from 7000 to 17000. Geometrical parameters such as relative length (α), relative pitch (β) and relative height (λ) are varied in the range of 0.0067–0.040, 0.0333 to 0.10, and 0.1 to 0.5, respectively, to optimize the performance of the SAH. Higher exergetic ratio is found around the same parametric values where we get the highest TEF value. The maximum TEF is found around 1.455 at α = 0.020, β = 0.0667, and λ = 0.30 at Re of 17000 and the corresponding exergetic ratio is found around 0.9949. The length of the groove is found to augment both heat transfer and pressure drop of the solar air heater due to increased disruption of thermal and hydrodynamic boundary layers. Rate of augmentation of heat transfer decreases in case of α≥ 0.0333 due to formation of an additional stagnant zone inside the groove. The flow and thermal analysis shows that although local heat transfer within the rectangular groove is less, the rectangular groove improves the channel's overall heat transfer. Convective heat transfer coefficient is found relatively higher where there is a change in shear stress gradient.

Experimental Study of Thermal Hydraulic Performance Improvement in Solar Air Heater Channel With V-Shaped Porous Baffles

Abstract Experiments have been conducted to determine how several geometrical parameters of V-shaped porous baffles influence flow characteristics and heat transfer in a rectangular channel. Experiments were conducted on geometric parameters, namely, a relative baffle height (e/H) of 0.4–1, a relative baffle pitch (P/e) of 3–6, open area ratio values of 21–34%, and a single attack angle (α) of 60 deg. Using Reynolds numbers ranging from 2500 to 12,000, V-shaped porous baffles have been examined. Based on a relative baffle pitch of 5, a relative baffle height of 1, and an open area ratio of 21%, the maximum increases in the Nusselt number (Nu) and friction factor (f) were 2.84 and 7 times, respectively. A maximum value of 1.69 is found at e/H = 0.40, P/e = 6, and b = 34% for the thermo-hydraulic performance parameter. Correlations for (Nu) and (f) are developed as functions of P/e, e/H, and Re.

Numerical Investigation for Turbulent Flow through a Solar Air Heater Channel with a Different Curved Baffles Geometry and Position

Numerical Investigation for Turbulent Flow through a Solar Air Heater Channel with a Different Curved Baffles Geometry and Position

Computational fluid dynamics-based parametric study on the performance of solar air heater channel.

Computational fluid dynamics (CFD) plays a prominent role in the design and development of solar air heaters. The previous investigations have lagged in using a radiation model for the solar heat input; instead, most of the researchers simulated a constant heat flux model. Moreover, an extensive study on the geometrical and boundary conditions like confinement and transition length, suction, and blowing effects has not been studied. The present investigation deals with the aforementioned effects on the flow and heat transfer characteristics of the SAH channel, which is designed for residential space heating. The finite volume-based solver Ansys Fluent is used for finding the field variables. The confinement height is varied from 25 to 150mm, and the transition length is varied from 250 to 1000mm. The suction and blowing effect is investigated by changing the flow direction across the channel. Even though the temperature rise is less significant with respect to confinement height and transition length, the effective efficiency increases with decreasing channel height and increasing transition length. In general, blowing of air across the channel gives better performance than suction. When comparing them, the influence is less in temperature rise and more in pressure drop for the channel height of 25mm, whereas the channel height of 150mm has better influence in temperature rise and less influence in pressure drop.

Utilising fractional porous interface for high thermal performance of serpentine wavy channel solar air heater

This work investigates the thermohydraulic performance of a porous serpentine wavy channel solar air heater. Comprehensive illustration on the effect of fractional porous interface (25%≤ξ≤100%), channel porosity (90%≤φ≤100%) and Reynolds number 2000≤Re≤11000 on the thermohydraulic performance of solar air heater design is presented. Experiments are performed and numerical results are validated to conduct further investigations for the optimization of the input variables. This study is a unique idea that broadly presents the scope of thermal performance improvement by utilizing the porous media in fraction and varying porosity in solar air heater channel and highly useful for the researchers of this field. Finite volume method based computational fluid dynamics tool is used to conduct numerical investigations, Forchheimer equation is used to account the effect of porous media and surface to surface (S2S) radiation model to capture the effect of shape factor and emitted radiation in collector channel. It is obtained that ξ of 25% and φ of 93% delineated the best thermohydraulic performance (THPP) of 4.52 for the present solar air heater design. While, the obtained thermohydraulic performance is 186% times higher compared to the smooth design. The excellent results that come into the light from numerical investigation are the secondary flow formation in the porous and flow zones at higher Reynolds number and lower fraction of porous region (ξ), and for all configurations of ξ at large channel porosity (φ). Hence, results of this investigation not only present the best operational configuration to obtain higher thermal performance, but also present the measures to reduce the material cost of porous media and consequently pumping power.

Thermal Investigations of Double Pass Solar Air Heater with Two Types of Porous Media of Different Thermal Conductivity

This study describes an experimental investigation of the thermal efficiency of stainless steel mesh and steel wool as a porous medium in the lower channel of a double pass solar air heater. An experimental setup was planned and developed. Various types of porous media with high thermal conductivity and with different porosities have been tested. The effects of the porosity of wire mesh, the thermal conductivity of porous media, mass flow rate, and the intensity of radiation have been studied. Experimental results show that thermal efficiency with using porous media is greater than without using porous media. When used steel wool as a porous medium, the thermal efficiency reached 79.82 percent while it can be achieved 76. The percent by using stainless mesh as porous material. The reduction in porosity increasing thermal efficiency. The thermal efficiency of multi-pass solar air collector when used steel wool as porous media is 6, 12.6 and31.7percent higher than without porous media at porosity 98.75, 97.5, and 96.25percent. While it can increase 8.1 and 28.5 percent at porosity 97.875 and 95.75 percent when using stainless steel as porous media.

Heat transfer and fluid flow characteristics of solar air heater duct with non-uniform ribs

This article presents a solar air heater channel artificially made rough with a transverse roughness in square-wave shape, investigated for the enhancement in heat transfer and fluid flow characteristics. Non-uniform profile of the ribs has been used by providing periodic gaps for reduction in eddies behind the rib. The research incorporates relative roughness width from 10–310, relative roughness pitch = 10, relative roughness height = 0.043, and Reynolds number from 3000–15000, respectively. The procedure followed for the CFD investigation has been confirmed with the experimental results. The maximum increment in Nusselt number was 2.22, and the consequent value for the friction factor increment of 3.44 was obtained. The highest THPP value of 1.49 was obtained while maximum thermal efficiency of 68.6% was achieved. The non-uniform ribs were found better as compared to uniform ribs. The results have been demonstrated using graphical contours and streamlines.

Effect of fabricated V-rib roughness experimentally investigated in a rectangular channel of solar air heater: a comprehensive review.

Solar power is one of the main sources of renewable energy which helps for protecting the environmental and reducing pollution. Technologies and systems for utilizing solar power are the area of research and development for a number of decades. In a solar air heater (SAH), use of fabricated irregularities on its wide face is an effective technique to augment heat discharge for flowing air with a moderate rise in frictional conduct. The necessary conditions for building an effective roughness design are to pick roughness patterns and its geometrical factors such that they may govern the nature of fluid flow with a rise in the heat discharge and lowering pumping losses. Continuous efforts are being carried out by various researchers to optimize the roughness parameters that deliver high heat release rates with low cost of pressure penalty or better thermo-hydraulic performance parameter (THPP). The researchers dominantly studied V-shaped of roughness design because of its better performance characteristics. The main intent of the present paper is to appraise or compile the influence of various V-shaped rib roughness on the thermal behavior of SAH. The outcomes of different V-designed rib roughness in terms of Nusselt number (Nu), and friction factor (f), statistical correlations established related to geometrical parameters and THPP are summarized. A comparative study using different V-designed ribs are also discussed to guide the future research and improvements.

Experimental Study of Jet Impinging Double-Pass Solar Air Heater Using Wire-Mesh. (Dept. M)

window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag("js", new Date()); gtag("config", "UA-72322659-1");

Experimental and numerical investigation on irregular spacing of the ribs in the entry length of a solar air heater channel

An experimental test rig is utilized to measure the effects of the flow configuration and particularly the rib geometry, on the thermal performances of solar air heaters. Since the heat transfer rate within the entry length is relatively high, the implementation of the ribs needs to be justified. Computational fluid dynamics simulations are also conducted to support the experiments and to provide detailed visualization of the flow field. The experimental data approves that the numerical simulation can estimate the heat transfer and pressure drop with reasonable accuracy. It appears from the results that achieving a particular spacing between the first ribs within the entry length, greater than the normal spacing in the fully developed region, yields a better performance. It is shown that in relatively short channels where the ratio of channel length to hydraulic diameter is small, the application of wider spacing in the entry length results in almost the same heat transfer rates, while it benefits from a much smaller pressure drop. In a presented case study, the application of irregular spacing improves the thermal performance of a flat plate solar collector by 11% compared to the collectors having ribs with regular spacing.

Impact of multi-staggered rib parameters of the ‘W’ shaped roughness on the performance of a solar air heater channel

ABSTRACT 8The collection efficiency of a solar air heater can be enhanced by employing artificial roughness as one of the modus operandi to create turbulence which helps in breaking the laminar sub-layer. The present investigation takes into account the impact of multi-staggered rib parameters of the W-rib roughness on the performance of the solar air heater channel. The chosen geometry in the current investigation is novel in a way that no such combination of roughness in the form of ribs has ever been tried earlier. The dimensionless factors for investigation were varied to study the effect of staggered ribs in the form of relative staggered pitch (p/P) 0.45–0.75 and relative staggered rib length (w/e) 1.5–6.0 for Reynolds number in the workable range of solar air heater channel as 4000–14000. Other parameters/factors were kept constant by selecting the optimal values from available works as relative roughness pitch (P/e) 12, relative roughness height (e/Dh) 0.0423, angle of attack (α) 60°, relative gap width (g/e) 1, number of gaps (n) 2. The augmentation in Nusselt number ratio has emerged in the range of 2.3–4.1, optimum values of p/P and w/e correspond to 0.65 and 4.5, respectively. A comparison with geometries under the analogous flow and thermal conditions has also been carried out.

CFD Analysis of Airflow Through Prism Obstacles Inside Solar Air Heater Channel

This study presents an analysis of airflow through prism obstacles inside a trapezoidal solar air heater channel using a computational fluid dynamics method. The purpose is to now the best configuration of gap ratio (S/H) 0.7, 1, 1.3 for 30° obstacle folded angle. The air is 2.62 m/s and the air temperature is 299 K. The channel wall boundary condition is heat flux with a constant value of 620 W/m2 is attached alongside the wall of the channel. The equation is Pressure-velocity coupling performed with SIMPLE. Renormalization-group (RNG) k-ε is chosen as a turbulent model. The simulation result presents temperature distribution, airflow vector in the middle plane of a channel. The obstacle can create backflow. It can increase the air temperature in a channel.

Investigational analysis of roughened solar air heater channel having W-shaped ribs with symmetrical gaps along with staggered ribs

ABSTRACT An investigational analysis upon heat exchange and friction misfortunes was led on the roughened rectangular solar-oriented air heater channel. The counterfeit roughness as W-shaped ribs utilizing symmetrical gaps alongside staggered ribs was made using round wires on one side of the wall as it were. The scope of parameters was viewed as using Reynolds number (Re) from 4000 to 14000, relative roughness pitch (P/e) 10–14, relative gap width (g/e) 0.5–2.0, relative staggered rib length (w/e) 1.5–6.0, relative staggered pitch (p/P) 0.45–0.75, number of gaps (n) 1–4, approach angle (α) 60°, relative roughness height (e/Dh) 0.0423, duct aspect ratio (W/H) 10. Utilizing these parameters in the picked range, the far-reaching examination of the framework has been practised. The most extreme growth in Nusselt number proportion was recorded 4.10 practically equivalent to Re = 12000, P/e = 12, g/e = 1, w/e = 4.5, p/P = .65 and n = 2. THEP was likewise determined and the most extreme improvement was observed to be 3.24.

Computational Fluid Dynamics Based Numerical Simulation of Thermal and Thermo-hydraulic Performance of a Solar Air Heater Channel Having Various Ribs on Absorber Plates

Computational Fluid Dynamics Based Numerical Simulation of Thermal and Thermo-hydraulic Performance of a Solar Air Heater Channel Having Various Ribs on Absorber Plates

Thermal behavior in a solar air heater channel roughened with delta-shaped vortex generators

Despite the various techniques used in strengthening the Solar Air Heater (SAH) through extended surfaces (obstacles) on the absorber plate, its thermal performance remains far from the optimal rate. Accordingly, an experimental study has been conducted to improve the SAH thermal performance. The technique consists in investigating the heat transfer, friction factor and thermal enhancement factor of flow in a rectangular channel artificially roughened with two longitudinally curved delta-shaped baffles configurations. Two cases have been dealt with perforated and non-perforated baffles. This study encompassed for the range of Reynolds number (Re) from 2500 to 12,000, relative longitudinal length of the obstacles on the absorber plate Pl/e from 3 to 5, relative transversal length of the obstacles on the absorber plate Pt/b from 0.6 to 1, relative roughness height (e/H = 0.8) and single attack angle (α = 45°). The obtained results averred a significant augmentation in heat transfer and reduction in pressure drop. Whereas, heat transfer (Nu) and in airflow friction (f) have reached respectively 6.94 and 45.83 times more than smooth channel. In case of perforated longitudinally curved delta-shaped baffles (LCD), the maximum thermal enhancement factor (TEF) rate was found to be around 2.26 when Pl/e and Pt/b are respectively equal to 0.3 and 0.6. However, the non-perforated LCD has reached a maximum of about 2.21. Following a correlation on experimental data of the heat transfer and airflow friction based on the adopted rates, the two parameters have attained deviations of about 12% and 7%, respectively.

Fully developed periodic and thermal performance evaluation of a solar air heater channel with wavy-triangular ribs placed on an absorber plate

The heat transfer rate, flow topology, friction loss and thermal performance factor (TEF) of newly design wavy-triangular ribs mounted on an absorber plate in a solar air heater channel were numerically investigated. The effects of the blockage ratio, BR = 0.02–0.1 and the pitch ratio, PR = 0.4–1.5 were studied in the turbulent flow region, Re = 3000–20,000. The numerical results showed that the RNG k-ε turbulent model is recommended for the present case since the model gives the most accurate predictions compared to other turbulent models. The wavy-triangular ribs induced vortex flows that effectively disrupted the thermal boundary layers leading to enhanced heat transfer rate from the absorber plate to the air. Increasing the Reynolds number (Re) and blockage ratio (BR), while decreasing the pitch ratio (PR) led to increased vortex strength that helps in reducing the thermal boundary layer thickness, thus promoting heat transfer. Over the range investigated, the channel with wavy-triangular ribs provided higher friction factors (f) and Nusselt numbers (Nu) than a smooth channel by 5.8–304% and 13.8–171%, respectively. In addition, the ribs with a blockage ratio of BR = 0.07 and a pitch ratio of PR = 0.5 gave the highest TEF of 2.62 at Re = 3000.

Experimental Study on Double-Pass Solar Air Heater with and without using Phase Change Material

In this paper, an experimental study was conducted to enhance the thermal performance of a double-pass solar air heater (SAH) using phase change material (PCM) for thermal storage at climatic conditions of Baghdad city - Iraq. The double-pass solar air heater integrated with thermal storage system was manufactured and tested to ensure that the air heating reserved after the absence of the sun. The rectangular cavity filled with paraffin wax was used as a latent heat storage and incorporated into the lower channel of solar air heater. Experiments were carried out to evaluate the charging and discharging characteristics of two similar designed solar air collectors with and without using phase change material at a constant air mass flow rate of (0.0375 kg/sec). The parameters that affect the thermal performance of the SAH with and without the PCMs presented by solar radiation, the difference in air temperature, outlet air temperature, instantaneous thermal efficiency, and daily efficiency are evaluated. The experimental results show that when using the PCM, the temperature of the outlet air was enhanced and increased over the ambient temperature by (1.5 - 6.5 C) after sunset for 5 hours period. It was found that the instantaneous thermal efficiency of the heater using thermal storage exceeds 100% after sunset, this is due to a large amount of heat stored in the paraffin wax that has been released during the discharge process. Also, it was found that the daily efficiency of the double pass SAH integrated with and without thermal energy storage unit was (56, 47%) respectively.