Flat Plate Solar Air Heater Research Articles

Investigation and optimization of design parameters for the thermal performance of a flat-plate solar air heater with sensible heat storage medium

Investigation and optimization of design parameters for the thermal performance of a flat-plate solar air heater with sensible heat storage medium

The indirect solar dryers with innovative solar air heaters designs: A review article

AbstractThe drying process is considered an effective technique for preserving foods and agricultural products from spoilage. Moreover, the drying process lessens the products' weight, volume, and packaging, which prompts a reduction in the products' transportation costs. The drying technique with solar energy represents an ancient method, still alluring due to solar energy abundance and cost‐effectiveness. In this article, the previous manuscripts concerned with studying and analyzing indirect solar dryer systems that utilize innovative solar air heaters (SAHs) are reviewed. The results and conclusions are discussed intensively to clarify the significance of utilizing this type of drying technique. The effect of many parameters on the thermal performance and efficiency of the dryer systems has been investigated. The investigated parameters included the incident solar radiation, air flow rates, outlet solar air heater temperature, absorber plate material, moisture content of the agricultural products, and the shape and configuration of the SAH. Moreover, the manuscript outlines the drying rate mathematical models that were used to validate the experimental findings. Based on the review, it is found that solar dryer systems with modified SAHs designs rather than flat plate SAH have considerable effects on enhancing thermal performance and efficiency.

Thermo-hydraulic performance of solar air heater with finned absorber plate forming multiple rectangular air flow passages in parallel under laminar flow conditions

The paper presents results of an analysis carried out using the governing equations to compare the heat transfer performance of a uniformly heated flat plate with longitudinal fins, which form multiple rectangular air flow passages in parallel below the plate and cover whole of the passage surface, with that of the low aspect ratio rectangular duct typical of conventional flat plate solar air heater at equal pumping power under laminar flow conditions. The heat transfer rate at equal pumping power for the plate with 1 mm thick steel fins at pitch of 25 mm and 40 mm is found to be about 2.7 and 2.5 times, respectively, over the duct without fins. The heat transfer study is followed by thermo-hydraulic performance study of the solar air heater with absorber plate having longitudinal fins forming multiple rectangular air flow passages in parallel. The finned solar air heater with low air mass flow rates has been found to provide 28–31 % better thermal efficiency than the conventional solar air heater at equal pumping power. The results of the study can be utilized for the development of enhanced performance finned solar air heater operating with low air mass rates to deliver high temperature air.

Mathematical and simulation-based analysis of the thermal and electrical performance of a flat plate solar air heater coupled with thermoelectric generators (TEGs)

The thermal performance of a flat plate solar air heater coupled with thermoelectric generators has been studied. A model of the collector was designed and simulations using SCILAB software were carried out to assess its performance. The design was carried out by analyzing the various heat and mass transfer processes which occurred in the components of the air heating system. The analysis resulted in the formulation of mathematical expressions that modeled the conversion of solar energy from the sun into thermal energy absorbed by the air flowing through the collector. The temperatures of the various components of the collector were determined using the finite forward difference discretization method. The cumulative energy generated by the heat source was 87 MJ while the energy gained by the heated exit air amounted to 37 MJ, bringing about a system thermal efficiency of 42%. The electrical efficiency of the model was 8.3%.

Design a low-cost, medium-scale, flat plate solar air heater: An experimental and simulation study

The most efficient solar air heater is expensive, and attempts to reduce costs lead to reduced efficiency. The current study presents a low-cost, medium-scale, flat plate solar air heater's design, simulation, and experimental thermal analysis. Carbon steel, thermocol, window glass, and aerosol spray paint were utilized for fabrication to decrease manufacturing costs. Initially, a mathematical model was developed, and experimental tests on this system were carried out with different absorber plates and glass covers in various weather conditions. The air mass flow rate of the collector is set at 0.073 kg/s. According to the experimental results, the solar air collector with a finned steel absorption plate, black paint, and double-glazing exhibit optimal performance. Under average solar radiation and ambient temperature of 910 W/m2 and 29.44 °C, respectively, the maximum thermal efficiency is 60.81 %, the average thermal efficiency is 56.01 %, and the average air temperature difference between the inlet and outlet is 40 °C. Whereas, for the solar air collector with plain steel absorber plate and single glazing, the least desirable performance was observed with a maximum collector efficiency of 45.76 %, an average thermal efficiency of 39.22 %, and an average air temperature difference of 20.14 °C between inlet and outlet under average solar radiation and ambient temperature of 810 W/m2 and 29.98 °C, respectively. Compared to the results, the thermal performance of solar air collectors with a finned steel absorption plate, black paint, and double-glazing was improved by 14 % to 20 % under different conditions. In addition, the solar air heater was designed, and a simulation study was performed in COMSOL Multiphysics software to find the temperature distribution of the glass cover and absorber plate. The experimental findings demonstrated that this convenient and cost-effective solar air collector was designed successfully and can be utilized in heating applications.

Analytical investigation of jet impingement solar air heater with dimple-roughened absorber surface via thermal and effective analysis

In this study, the thermal and effective efficiencies (ηthe and ηeff, respectively) of a dimple-roughened jet impingement solar air heater (DRJISAH) are analytically examined. The analysis is performed based on the following conditions: Reynolds number (Re) = 3000–24000; solar irradiance (Isr) = 700–1000 W/m2; dimple height ratio (ed/Dhd) = 0.016–0.031; dimple pitch ratio (pd/Dhd) = 0.269–0.810; arc angle (αd) = 30°–75°. An enhancement in ηthe by 18%–29% is achieved, which is corresponding to the ηthe of a jet impingement solar air heater. The ηeff of a DRJISAH is greater than that of a flat-plate solar air heater (FPSAH). However, at high values of Re, the useful thermal energy gain is dominated by frictional losses in the duct; thus, the FPSAH has a higher ηeff value than the DRJISAH. The optimum ηthe and ηeff for the DRJISAH are 74% and 70%, respectively, at ed/Dhd = 0.031, pd/Dhd = 0.269, αd = 60°, and Isr = 1000 W/m2. In addition, each dimple parameter is plotted against Re to obtain the best ηeff for the specified Re.

Enhanced Heat Transfer Performance of Multiple Triangular Air Flow Passages in Parallel With Inclined Fins for Flat Plate Solar Air Heater

Abstract This paper presents results of a study of heat transfer performance of multiple equilateral triangular parallel air flow passages below a uniformly heated flat plate having inclined fins of different thickness, length, and material covering a part of the side walls of the duct for transition to early turbulent regimes using appropriate experimental heat transfer coefficient and friction factor correlations from the literature. The heat transfer performance enhancement at equal pumping power has been measured in terms of a performance parameter (hA/hsAs), where hA is the product of heat transfer coefficient and total heat transfer area for the finned triangular duct, and hsAs is the product for the triangular duct with heated flat plate without fins and adiabatic side walls. The values of the performance parameter for steel fins integral with the heated plate are found to be 1.71–1.78 for 1.0 mm thick fins of 15 mm length and 1.94–2.04 for 1.5 mm thick fins of 20 mm length. For aluminum fins, the performance parameter is 2.36–2.54 for 30 mm long fins of 1–1.5 mm thickness. The results of the presented novel scheme of the finned heated plate can be utilized for the development of enhanced performance solar air heater with the finned absorber plate. Since the presented scheme enhances heat transfer without increased pumping power penalty, the existing smooth rectangular duct solar collectors can be modified for enhanced performance.

Comprehensive energy, exergy, enviro-exergy, and thermo-hydraulic performance assessment of a flat plate solar air heater with different obstacles

• Performance assessment of a solar air heater with different air barriers is performed. • Air obstacles can significantly enhance the system's energy and exergy efficiencies. • Vertical cylindrical obstacles have a greater performance compared to others. • Energy and exergy efficiencies can be enhanced up to 70% and 105%, respectively. • Relative CO 2 reduction potential is improved up to 170%. Although obstacles on the absorber surface of a solar air heater (SAH) can increase the thermal efficiency by creating turbulent conditions, they might reduce the system's exergy efficiency due to an increase in the pressure drop. In the present work, a 3-dimensional computational fluid dynamics (3D CFD) model is first developed to simulate conical obstacles, and the developed model is then validated using the available experimental data. To find optimal design features, obstacles with various shapes/geometries such as cylindrical, spherical, hemispherical, pyramidal, and cubical are investigated. To attain this goal, a comprehensive study is conducted by including energy, exergy, enviro-exergy, and thermo-hydraulic analyses. The results reveal that vertical cylindrical obstacles have better performance than other geometries as well as a flat absorber without obstacles. The average daily thermal efficiency of the system is increased by 69.16%, and the exergy efficiency of the system is increased by 103.16%. The relative CO 2 reduction potential (RCDRP) for a SAH with vertical cylinders is improved up to 168.7%. In addition, the vertical cylinder with a daily average thermo-hydraulic performance parameter of 1.2 shows the greatest thermo-hydraulic performance parameter (THPP) among other geometries, and the pyramidal obstacle with the THPP of 0.66 has the minimum performance.

A Comparative Study of Nusselt Number Correlations for Smooth Surfaced Equilateral Triangular Duct for Flat Plate Solar Air Heater

A Comparative Study of Nusselt Number Correlations for Smooth Surfaced Equilateral Triangular Duct for Flat Plate Solar Air Heater

Detailed Investigation of Heat Transfer Enhancement of Louvered-Winglet Vortex Generators Mounted on Flat-Plate Solar Air Heaters

Detailed Investigation of Heat Transfer Enhancement of Louvered-Winglet Vortex Generators Mounted on Flat-Plate Solar Air Heaters

Experimental investigations of thermal performance for flat and dimpled plate solar air heater under turbulent flow conditions

Conversion of solar energy into useful thermal energy through solar air heaters (SAH) enhances the practical application of the available solar energy. A comparative thermal analysis of two SAH’s having different absorber plates is elucidated here. Experiments were conducted on a flat plate solar air heater (FPSAH) as well as on dimpled plate solar air heater (DPSAH) during bright and sunny days from 0930 am to 1430 pm at IIT (ISM) Dhanbad on six different days for six different flow rates between 0.028 kg /sec to 0.051 kg /sec (i.e. Re value = 5500 to 10300). For these two SAH’s, different parameters and thermal properties were evaluated and compared. Quantitively, it is shown that the temperature difference, average extracted power, heat transfer coefficient, instantaneous efficiency and the effective efficiency of the DPSAH is higher than the FPSAH. Subsequently, it has been also observed that, the rise in effective efficiency of DPSAH at higher mass flow rates (MFR) is not significant; hence it is less suitable for high flow rate operations.

Thermo-hydraulic and exergetic performance of a cost-effective solar air heater: CFD and experimental study

An experimental and computational fluid dynamics (CFD) study is carried out to investigate the impact of secondary flow strengthening the thermo-hydraulic performance of discrete multiple inclined baffles in a flat plate solar air heater (SAH) with semi-cylindrical sidewalls. Initially, for a fixed relative baffle height (Rh = 0.1), the relative baffle pitch (Rp) for continuous baffles is varied in the range of 0.6–1 to obtain the optimum baffle pitch for 6000 <Re < 14000. The impact of gaps at leading, trailing, and both leading and trailing apices are studied as three different configurations with the optimum Rp. A maximum thermo-hydraulic performance of 2.69 is obtained for the gap at the trailing apex. The proposed design has a higher collector efficiency, 55–70%, compared to the ribbed rectangular SAH design exhibiting 30–55%. With lower exergy losses, the present SAH design has higher exergetic efficiency (1.5%–2.2%)than ribbed rectangular SAH (0.9%–1.7%) for the range of Re studied. Further, at low Re, the present SAH design has a higher coefficient of performance, indicating that it is cost-effective than ribbed rectangular SAH designs.

Numerical simulation of the transient turbulent natural convection in an inclined rectangular shaped solar air heater

Due to high energy demand and adverse effect of global warming, improving the performance of solar thermal systems is of great importance. In this respect, the transient flow and thermal behavior of turbulent naturally ventilated airflow in a flat plate solar air heater (SAH) are investigated numerically. To achieve this aim, conservation of mass, momentum, and energy equations are solved for the turbulent airflow concurrently with the conduction equation inside the solid element using finite element method (FEM). The low Reynolds turbulence model is applied in the calculation of turbulent stress and heat flux, and the Boussinesq approximation is applied for computing buoyancy forces associated with the density gradient. The surface radiation is also considered explicitly in the calculations to obtain more accurate and reliable results. It is found that although based on the considered location the maximum incident radiation occurs at the optimum angle of 30°, the maximum flow rate reach to its peak when the inclination angle is 60°, in which the total increase of incident radiation is nearly 17%. It is also found that the rate of heat transfer is a decreasing function of the inclination angle (30⩽θ⩽90), such that the overall rate of heat transfer reduction is around 50%. Further, investigation of the impacts of solar radiation and air duct width on thermal performance showed that by increasing both parameter the rate of heat transfer and air flow increase by about 35% and 100% respectively. The exclusive analysis of the effects of sudden climate change on the SAH’s behavior revealed that a short time climate change leads to zero incident radiation, and considerable fluctuations in outlet temperature and flow rate.

Optimization of Flat-Plate Solar Air Heater for Drying Mangifera Indica by Using Karush Kuhn Tucker (KKT) Conditions

The increase of the world demographic distribution makes the continuous and large-scale production of food necessary. Some of these are perishable fruits and vegetables, whose handling times between harvest and consumption should be short. In order to reduce the amount of food wasted in storage and distribution stages, the implementation of a dehydrator system is proposed. This kind of systems regulates the airflow and the air temperature in closed and controlled environments with the aim of extracting the food moisture in order to preserve it for longer periods. With the arrival of alternative energies and their multiple applications, this works presents the design and the development of a system for drying tropical fruits, specifically Mangifera Indica, using the sun as primary source of energy in flat solar collector in order to replace the electrical consumption of conventional drying equipment, offering an alternative in areas with limited access to the electricity network. In addition, optimization algorithms have been used to compute the mechanical design parameters, and six designs with manufacturing variations have been compared, obtaining as max outlet temperature a value of 66 °C.

A study on heat transfer enhancement for solar air heaters with ripple surface

Flat-Plate solar air heater (SAH) is utilized widely to relieve the fossil energy crisis nowadays. With the aim to improve the efficiency of the devices, heat transfer and flow characteristic in a solar air heater with novel inclined groove ripple surfaces were investigated in this work. The effect of three different parameters, such as groove amplitude, attack angle, and array number, on the overall performance of air heater was analyzed in the range of Reynolds number from 12000 to 24000. The inclined grooves on the ripple surface have a significant impact on the working fluid for generating longitudinal swirl flow in the duct of air heater, which mixes the air to enhance heat transfer, Nu/Nu0 = 1.21–3.38, and leads to a moderate increase of pressure drop in the same time, f/f0 = 1.54–6.96. The solar air heater composed with ripple surface is of excellent overall thermo-hydraulic performance, Nusselt numbers are 1.04–1.94 times higher than the smooth duct at same blowing energy consumption.

Impact of Secondary Flow on the Exergetic Performance of a Cost-Effective Solar Air Heater Design: CFD and Experimental Study

An experimental and computational fluid dynamics (CFD) study is carried out to investigate the impact of the strength of secondary flow on the thermo-hydraulic performance of discrete multiple inclined baffles in a flat plate solar air heater (SAH) with semi-cylindrical sidewalls. Initially, for a fixed relative baffle height (Rh = 0.1), the relative baffle pitch (Rp) for continuous baffles is varied in the range of 0.6 to 1 to obtain the optimum baffle pitch for 6000 < Re < 14000. The maximum thermohydraulic performance parameter (THPP) is obtained as 2.28 for Rp = 0.75 at Re = 6000. With this optimum Rp, the impact of gaps at leading, at trailing, and at both leading and trailing apices is studied as three different configurations. Maximum heat transfer enhancement of 2.47 times is obtained for multiple inclined baffles with the gap at trailing apex for Re = 14000 with a corresponding increment of 3.07 times in friction factor (f). Maximum THPP is obtained as 2.69 for gap at the trailing apex for Re = 6000. With lower exergy losses, the present SAH design has higher exergetic efficiency, collector efficiency and is cost-effective compared to ribbed rectangular SAH.

Energy, exergy, economic and environmental assessment of double pass V-corrugated-perforated finned solar air heater at different air mass ratios

An assessment of a flat plate double pass (DP) solar air heater (SAH) having V-corrugated absorber (C_SAH) and corrugated-perforated absorber (CP_SAH) via energy, exergy, economic and environmental approaches (4E) is presented experimentally. The study is performed at four different levels of air mass flow ratios inside the flat plate solar air heater with two levels of absorber plates i.e. C_SAH and CP_SAH. C_SAH and CP_SAH performance is compared with flat SAH (F_SAH) performance. The results show that F_SAH achieves the lowest daily energy efficiency values of 52.5%, 55.86%, 54.77%, and 56.7% while CP_SAH achieves the highest of 67.67%, 69.7%,71.85%, and 70.8% at SP, 1/3 DP, 2/3 DP, and DP conditions, respectively. Moreover, C_SAH and the CP_SAH achieve maximum daily efficiency of 70.58% and 71.85% at 2/3 DP condition. CP_SAH achieves average daily exergy efficiency of 0.78%, 0.89%, 0.97%, and 0.92% with percentage increments of 47%, 55%, 76%, and 54% compared to F_SAH at same previous conditions, respectively. F_SAH at SP condition achieves the maximum energy cost of 0.0427 $/kWh while CP_SAH at 2/3 DP condition achieves the minimum energy cost of 0.0324 $/kWh. The proposed CP_SAH at 2/3 DP condition is the most suitable from the studied cases.

Effect of combined U-shaped and semi-circular rib on heat transfer augmentation of solar air heater-A CFD study

This paper presents the numerical analysis on the impact of combined U-shaped rib and semi-circular rib on heat transfer augmentation of flat plate solar air heater system.The analysis is done using the ANSYS Fluent software for various flow Reynolds number ranging from 8000 to 17000. The ribs are placed alternately on the underside of heated plate for a fixed stream-wise pitch of 35mm. The rib height is so chosen that the diameter of semi-circular rib equals the rib height of U-shaped rib. The rib height (e) is varied as 2mm, 3mm and 4mm. The analysis reveals that the combined ribs augment the heat transfer to a maximum extent of about 1.67 times as compared to the smooth duct. Ribs of greater height are found to produce greater enhancement in heat transfer due to increased flow mixing effect. The friction factor is found to increase with rib height and the highest increase is found to be about 1.73 times as compared to smooth duct for Re=8000.

An in depth evaluation of matrix, external upstream and downstream recycles on a double pass flat plate solar air heater efficacy

In the present study, the thermal and thermohydraulic characteristics of different types of double pass solar air heaters (DPSAHs) containing three flow channels were analytically investigated. The analyses were conducted at air mass flow rates of 0.01, 0.015, 0.025 kg/s and different reflux ratios of 0.1 to 1. The effects of upstream and downstream recycling patterns were analyzed. Moreover, the impacts of matrix placed between the absorber plate and the second glass cover with various porosities, and variation of solar radiation intensity on the DPSAH performance were examined. Furthermore, the pressure drop due to the existence of matrix was considered to obtain more realistic outcomes. The results demonstrated that as to the downward recycling pattern, using matrix leads to an increase in the DPSAH thermal efficiency presenting the thermal efficiency of 79%; however, it brings about a reduction in its thermohydraulic efficiency at high mass flow rates and reflux ratios and high fan power cost is incurred, subsequently. The most compelling result is: if we consider an upstream recycling pattern, it is true that we have overlooked a certain amount of the DPSAH efficiency compared to a matrix-based downward recycling DPSAH (about 7% less efficiency); however, at high mass flow rates and reflux ratios the thermal efficiency of DPSAH is similar to that of a matrix-based upward recycling DPSAH, and in this way, not only the hot air demand is supplied, also the extra fan power cost and the cost of providing a suitable matrix are eliminated.

Energy, exergy, and enviroeconomic assessment of double and single pass solar air heaters having a new design absorber

This paper experimentally examines the performance of solar air heater (SAH) having a newly designed tubular absorber comprising adjacent parallel tubes called tubular SAH (T_SAH) via energy, exergy, and enviroeconomic standpoints. A comparative performance assessment between T_SAH and flat plate solar air heater (F_SAH) at diverse air mass flow rates (MFRs) of 0.075, 0.05, and 0.025 kg/s is performed. Experiments for both heaters are tested using two flow pass arrangements of single-pass (SP) and double-pass (DP). The results reveal that maximum enhancement in thermal and exergy efficiencies of 133 % and 330 %, respectively is obtained when using SP T_SAH against SP F_SAH at air MFR of 0.025 kg/s. It is found that when there is an increase in air MFR, there is a significant increment in thermal efficiency, whereas there is a reduction in exergy efficiency. Despite the performance in the case of T_SAH is more effective than F_SAH, the enhancement in the case of DP F_SAH due to using DP flow configuration is greater than that of DP T_SAH. Finally, the results indicate that the carbon credit earned regarding the amount CO2 mitigated for SP F_SAH and SP T_SAH at MFR of 0.075 kg/s is estimated at 391.6 $/year and 561.9 $/year, respectively.