Efficiency Of Solar Air Collector Research Articles

Effect of absorber shape on energy, exergy efficiency and enviro‐economic analysis of solar air collector: An experimental study

AbstractThe efficiency of solar air collectors, which are intended to convert solar energy into thermal energy, is the subject of numerous studies that aim to assess and improve it. Solutions for sustainable energy heavily rely on these systems. Making the right choice regarding the best method for absorbing solar radiation and reducing heat losses is what will ultimately lead to their improved performance. In this work, wavy and corrugated absorbers were suggested inside a solar air collector. The aim of this article is to study experimentally the thermal performance of the solar air collector when using wavy shape of absorber and corrugated shape of absorber instead of the flat shape of absorber under the same weather conditions of Sfax region central‐eastern of Tunisia. The suggested shapes of absorber augmented sun exposure and heating area. The results obtained from this experimental study show that switching from a flat plate absorber to both wavy and corrugated absorbers resulting significant performance gains. The absorber with waves showed a significant improvement in daily thermal efficiency of 22.89%, and the absorber with corrugations showed an even greater improvement of 40.56%. Comparable patterns were noted in daily exergy efficiency, where the corrugated absorber demonstrated an astounding 44.83% increase and the wavy absorber provided a 23.24% improvement. Notably, when total cost savings and monthly CO2 reduction were taken into account, the corrugated absorber turned out to be the best option. These findings highlight the importance of absorber form in optimizing thermal and energy efficiency, which may have positive effects on the economy and environment.

Multi-objective optimization design of solar air collector with a frustum-shaped protrusion

The artificial convex is arranged on the absorber plate of a solar air collector can significantly improve the solar utilization efficiency. The heat transfer efficiency is determined by the geometric types of protrusion and its arrangement in the heating channel. In this study, four parameters, the height and gap of the protrusion structure, the arrangement spacing of the V-shaped structure, and the airflow attack angle are considered to reflect the effect of protrusion on fluid flow and heat transfer characteristics in the solar air collector. Considering the interactive coupling relationship among various structure and location parameters, taking the maximum average Nusselt number, minimum friction coefficient, and maximum comprehensive heat transfer coefficient (THPP) as the objective functions, the Response Surface Method (RSM) is adopted to comprehensively analyze the impact of multiple factors on the thermal efficiency of solar air collector, and thus obtains the optimal design parameters of solar air collector with the optimal comprehensive performance. Comparing with the univariate method, the THPP value of the optimized structure by RSM is 3.6% higher than that by the univariate method. The value of thermal efficient of the optimized structure by RSM is 26% higher than that of the smooth plate solar air collector. When the Reynolds number is higher than 10000, the value of thermal efficient of the optimized structure by RSM is much higher than those of the published references. In addition, the contribution of different influencing factors to improving the comprehensive performance of solar air collector was obtained, which is meaningful for providing theoretical basis for engineering optimization design.

Numerical investigation of the effect of using louver baffles on thermal performance in solar air collectors

AbstractConventional flat plate solar air collectors have advantages such as low cost and simple design. However, their thermal efficiency is lower than that of other designs. The thermal efficiency of these collectors can be increased by detailed examination of parameters such as the shape, size, arrangement and material of the air duct. In this study, it is aimed to improve the thermal efficiency of solar air collectors. The effect of louver baffles, which were not previously used in solar air collectors, on thermal efficiency was investigated numerically via computational fluid dynamics. Three different solar air collectors with flat plates, segmented baffles, and louver baffles were compared in terms of thermal efficiency. In addition, pressure drops in solar air collectors were investigated. The mass flow rate of the air in all collectors is assumed to be 0.04 kg/s. Analyzes were carried out between 09:00 and 16:00. The thermal efficiency values obtained during the day for solar air collectors with flat plate, segmented baffles and louver baffles are 27.66%–56.35%, 29.57%–58.82% and 30.09%–59.47%, respectively. The daily thermal efficiency values obtained for solar air collectors with flat plate, segmented baffles and louver baffles are 46.98%, 49.18% and 49.87%, respectively. The pressure drop for solar air collectors with flat plate, segmented baffles and louver baffles were found to be 4.62, 18.82 and 5.96 Pa, respectively. Based on the data obtained from this study, louver baffles are recommended for use in solar heating applications due to their high thermal efficiency and low pressure drop.

A review of solar air collectors with baffles and porous medium: Types and applications

The current study and discussion in detail about the use of different types of porous media and barriers inside solar air heaters is our goal in this survey paper. The effect of different barriers and porous materials of different shapes and types within the solar air collectors and the effect of engineering parameters on heat transfer procedures and fluid movement were discussed by examining their thermal and hydraulic performance. Numerical and experimental analyses were presented on different types of flat solar air collectors containing differently shaped baffles or various porous media with different strategies to enhance heat transfer such as fluid flow measurement, pressure drop control, and checking their thermal and hydraulic performance by measuring the increase in air temperature at intensity Solar radiation and fluid mass flow. Studies show that the presence of porous barriers or media enhances the heat transfer process and increases the efficiency of solar air collectors. The types different of solar air collectors have been shown. We concluded this review to present various applications of solar air collectors such as cooling and heating various buildings, heating air for combustion processes, and drying coal and paper.

CFD model of acceleration of thermal-hydrodynamic processes in solar air collectors

Recent studies on increasing the thermal-hydrodynamic efficiency of solar air collectors have been carried out on the installation of barriers of various shapes on the surface of the absorber, and this method ensures a significant increase in the energy efficiency of the collector. The transfer of the air flow washing the surface of the absorber from a laminar flow state to an accelerated lumped air flow is carried out by installing obstacles. Installation of barriers is the main factor in increasing the heat transfer in solar air collectors and prolongs the time of air flow in the collector. The barrier solar air collector has a high local heat transfer coefficient, and the Nusselt number value is up to 3.5 times higher than that of the flat plate solar air collector. Also, this article presents the results of CFD modeling of the air flow in the solar air collector, the results of which can be used in the theoretical research of the solar air collector.

Improving Thermal Efficiency of Solar Air Collector by Creating Turbulent Flow Using New Baffles Combinations

The study shows an experimental investigation for a solar air collector with a single pass by adding rectangular baffles for different positions inside the channel. The aim of this study is to improve the thermal efficiency for this collector, and that through testing four cases of baffles positions (mode 1, 2, 3, 4). The study was done under different operating conditions by changing the mass flow rates and positions of baffles. The results show the effectiveness of the baffles in improving the efficiency of the collector, The study also proved that the baffles positions affect thermal efficiency, where the greatest efficiency was recorded in the fourth mode and then in the positioning of obstacles at the middle of the channel for the mode 2 and the mode 4 with a percentage of 76.61 and 90.9, at mass flow rate m=0.0522 kg/s, while the pressure drop was very high in the mode 4, and after that the mode 2. Through the conditions of the study and taking into account all the results; we can say that the best case was mode 2.

A new operating model for improving thermal efficiency of double-glazed solar air-phase change material collector: An experimental study

The heat storage type solar air collectors that only release heat at night have a low thermal efficiency. In this study, an experiment is conducted on a double-glazed solar air-phase change material (PCM) collector. An effective new operating model that performing air heating simultaneously in the energy storage stage is proposed to improve the overall efficiency of the heat storage type solar air collector. During the experiment, air heating is started at different times each day according to the degree of heat storage of the PCM. It is found the nighttime air heating is affected by the degree of heat storage of the PCM, the airflow velocity of air channel, and the inlet air temperature. The thermal efficiency of the solar air collector depends on the air heating start time during the day and airflow velocity of air channel. Under different weather conditions and operating conditions, the solar thermal efficiencies ranged from 34.51 % to 44.49 %. The results show that under the premise of ensuring the complete melting of the PCM, properly performing the air heating in the daytime can not only ensure nighttime air heating, but also improve the overall thermal efficiency.

The experimental study of energy features for solar air heaters with different turbulator configurations

AbstractTo assess the thermal performance in the climate conditions of western and central Iraq, the advantages of using a solar air collector with various turbulator absorber plates are experimentally explored. Four distinct kinds of absorber plates are provided flat plate (F), triangular (T), rectangular (R), and circular (C) turbulators at different air mass flow rates. The collector's economic properties and overall thermal performance are compared to the conventional flat plate turbulator heating systems. The main findings suggest that delta turbulators improve collector economics and overall thermal performance by generating vortex and dampening the formation of the thermal boundary layer in the direction of airflow. Furthermore, when the mass flow rate increases, the thermal performance improves, and the efficiency increases for all mass flow rates, resulting in good thermal performance for the rectangular plate collector when compared to other collectors. When compared to other types of configurations, the daily average efficiency of solar air collectors for flat plate (F), triangular (T), rectangular (R), and circular (C) turbulators are 28%, 67%, 39%, and 48%, respectively, at 50° tilt angle while at 90° tilt angle they are 44%, 76%, 54%, and 63%, respectively, as ṁ = 0.0377 kg/s. The maximum daily average efficiency fitted with rectangular turbulators have about 86% at the largest ṁ = 0.1 kg/s. This study will also give a unique direction to the work trend in the western and central parts of Iraq throughout the winter months.

Micro-scale heat and electricity generation by a hybrid solar collector-chimney, thermoelectric, and wind turbine

In the present study, a hybrid system that is fueled with solar energy is proposed. The system includes a solar air collector, solar chimney, thermoelectric generators, and Savonius wind turbine. The absorber plate and the passing air in the duct of the collector act as the heat source and heat sink of the thermoelectric generators respectively. As the air receives heat, it becomes less dense and goes up in the chimney due to buoyancy and the chimney effect. The chimney provides the required air velocity for the wind turbine. In addition, the hot air can be used for other purposes later, such as heating, or drying processes. The results reveal that the efficiency of solar air collector, thermoelectric generator efficiency, and power coefficient of Savonius wind turbine in a certain hour are 61%, 4.54%, and 19.56%, respectively. The average velocity of outlet air from the chimney is 2.32 m/s which can produce 2.17 W by the wind turbine. Additionally, the economic analysis demonstrated that net present value, and payback are approximately 19,707 $ and 1.34 years. Finally, the environmental analysis showed that this system has the potential to reduce emitted carbon dioxide by 5111 kg/year.

Enhancement of thermal efficiency of solar air collector by using discrete double arc reverse shaped roughness on the absorber plate

A solar air collector (SAC) is a heating device that applies warm air to dry agricultural products and for a variety of engineering purposes. The underside of the absorber plate used discrete double arc reverse shaped artificial roughness, outside testing performance for heat transfer coefficient, h, and thermal efficiency, ηth features of solar air collector were carried out in this article. During the outdoor experimental test, the following parameters were used: relative roughness pitch (p/e) = 8.33, relative roughness height (e/Dh) = 0.027, arc angle (α) = 60°, Reynolds Number (Re) = 3000 to 14000, and aspect ratio (W/H) = 8. Also, the outdoor test was performed at 11:00 A.M. before noon to 2:00P.M. afternoon with solar radiation intensities ranging from 860 W/m2 to 895 W/m2. The impact of various factors on heat transmission and thermal efficiency is compared to that of a smooth absorber duct under identical conditions of flow. Over the smooth duct, the maximum increases in coefficient of heat transfer and thermal efficiency are 2.88 and 1.29 times, respectively.

Research on the collect heat performance of new type collector

ABSTRACT In order to further improve the efficiency of solar air collector and reduce energy waste, this paper propose a semi-circular baffle solar air collector. The semi-circular baffle is used to enhance the disturbance of air so as to improve the outlet temperature of air and the thermal efficiency of the collector. This paper compares and calculates the different semicircle diameters, different collector lengths and different number of baffle plates. The dimensionless analysis of the model is carried out. The results show that the outlet temperature of the new collector is 27 K higher than that of the traditional collector, and the collector efficiency is increased by nearly 20%.The air outlet temperature of the new collector is proportional to the dimensionless parameters, while the collector efficiency is inversely proportional. When the dimensionless number is 7.5, the outlet temperature is 334.0 K, the collector efficiency is 54.7%, and the pressure loss is 15.3 Pa. At this time, the outlet temperature and collector efficiency are the most appropriate. When the number of baffle groups is 8, the outlet temperature of air is 350.8 K, the collector efficiency is 71.2%, and the pressure loss is 22.0 Pa. The collector has the best collector effect. Compared with the baffle collector, the outlet temperature and heat collection efficiency of the new collector are higher than those of the baffle collector under the little difference pressure loss.

Experimental Investigation of Drying Kinetics of Green Chilli and Okra using Indirect Solar Dryer with Evaluation of Dryer Performance

ABSTRACT In this study, green chillies and okra were dried using an indirect type solar dryer ITSD dryer and their drying kinetics were evaluated. The initial moisture content (MC) of green chilli was 8.3984 kg/kg of dry basis (db) and it was reduced to final MC of 0.2218 kg/kg of db. Also, MC of okra reduced from 10.1234 to 0.3348 kg/kg of db. The efficiency of solar air collector and the drying efficiency were estimated during the drying of green chilli and okra. The activation energy was found to be 32.484 and 25.330 kJ/mol and effective moisture diffusion coefficient was found to be 1.464 × 10-−9 and 5.1798 × 10-−9 m2/s for green chilli and okra, respectively. The surface transfer coefficients (both heat and mass) of green chilli and okra were estimated. Uncertainty analysis was performed on all the measured and derived drying parameters.

Drying and dynamic performance of well-adapted solar assisted heat pump drying system

A new type of well-adapted solar assisted heat pump drying system (SAHPDS) was put forward to choose and switch more efficient and energy-saving drying mode according to outdoor environment. The drying characteristics of shiitake mushroom, energy consumption level and running characteristics of system under five drying modes were investigated systematically. The drying modes were independent solar drying system (ISDS), independent closed heat pump drying system (ICHPDS), and SAHPDS of closed, open and semi-open modes. The results concluded drying system performed well in each mode. In ISDS, inlet air temperature of drying chamber can reach above 50 °C, heat collection efficiency of solar air collector (SAC) is 0.562 and SMER is 3.56 kg/kWh. In ICHPDS, the average COP is negatively correlated with air temperature and loading capacity, while positively correlated with air speed. In SAHPDS (assisted only by SAC), the average air temperature is 59.17, 62.38 and 60.83 °C in open, closed and semi-open modes at air speed of 3.5 m/s. With the corresponding modes, the heat collection efficiency of SAC was 0.526, 0.223 and 0.434 respectively. The average COP is 3.08, 2.68 and 3.20, which is significantly more energy-saving than ICHPDS mode in order to obtain same air temperature. In the later drying period, it switched to the closed drying mode of SAHPDS (only assisted by solar collector (SC)). In addition, the energy saving rate can reach 37.96% compared with ICHPDS under the same condition. The study provides a guidance and reference for the operation mode switch of SAHPDS with higher energy saving and efficiency.

Experimental analysis and exergetic assessment of the solar air collector with delta winglet vortex generators and baffles

To increase the efficiency of solar air collectors (SACs), the combined effects of baffles and delta winglet vortex generator (DWLVG) on the performance of SAC have been investigated. An experimental setup has been made, and numerical simulation is carried out in Ansys Fluent. The numerical investigation is validated by the experimental study and focused on the number of baffles as well as the number and the height of DWLVG. The results show that the SAC with no baffles and DWLVG has the lowest efficiency with the maximum value of 13%, while for SAC with six baffles and three pairs of DWLVG, the efficiency reaches up to 20%. The exergy analysis of three cases, SAC without baffles and DWLVG, SAC with six baffles without DWLVG, and SAC with six baffles and three pairs of DWLVG, shows that the maximum exergy efficiency of the SAC is 30.44% and occurs when the height ratio and the number of DWLVG pairs are 0.5 and 3. The results show that for SAC with six baffles and three pairs of DWLVG, the energy and exergy efficiency improve 7.4% and 12% on an average basis compared to the typical flat plate SAC, respectively. This improvement in thermal and exergy efficiency is due to the implementation of DWLVG which produces more turbulence and eliminates the vortices generated at the corners of SAC.

Theoretical and experimental research on effect of fins attachment on operating parameters and thermal efficiency of solar air collector

Flat plate air collector is a type of heat exchanger which absorbs radiated solar energy and exchanges it to heat. According to low efficiency of this type of collectors, a suitable approach is investigated in this paper so as to increase thermal performance of the system. Thermal efficiency of solar collector for two models C1 (without fins) and C2 (with fins) both of 1 m2 surface area with forced convection flow is studied theoretically and experimentally. Rectangular fins are attached over back board in air channel to create turbulence in air flow. In order to measure air temperature, 17 thermal sensors (LM35) are exploited, among which 11 were mounted on absorber plate and the remaining 6 on the back board. Physical design of experimental model are performed in Solidwork and programming of theoretical work in Matlab software. In this research, a fan with constant mass flow rate of 0.033 kg/s is utilized for producing air flow. Results indicate that applying fins in air channel not only reduces Nusselt number from 19.67 to 16.23, but also due to decreasing hydraulic diameter and creating air flow turbulence, causes increase of heat transfer coefficient from absorber plate to air flow and consequently reduction of total heat loss and higher outlet air temperatures. Average difference of outlet air temperature between experimental and theoretical results for both collectors (C1 and C2) was recorded respectively as 7.6% and 9.4%. Thermal efficiency was respectively calculated 30% and 51% for experimental types with and without fins and 33% and 55% for those of theoretical work which generally seem reasonable.

Experimental Investigation of One Glass Cover and Three Absorber Plates Two-Pass Solar Air Collector with Thermal Storage

Objective: Improvement of the thermal efficiency of solar air collector is a major issue in researcher’s community. Therefore novel design of solar air collector is constructed. The objectives of this research paper are to obtained the results of novel solar air collector and compare it with conventional type solar air collector. Methods/Statistical Analysis: The experiments are carried out at the different mass flow rate of air on novel design of one glass cover and three absorber plates two-pass solar air collector (OGTh Ap TPSAC) and one glass cover and two absorber plates single-pass solar air collector (OGTwAp SPSAC) operating on the same atmospheric conditions. The various thermal parameters such as heat gain, heat loss and thermal efficiency are determined with respect to time of the day. Findings: Major heat loss in any type of solar air collector is due to convection. To minimise this convection loss, vacuum is formed on top portion of novel designed solar air collector. Both solar air collectors taken for the comparison also has a unique feature of thermal storage. Comparative results show that the novel designed two-pass solar air collector is more thermally efficient than conventional single pass solar air collector. Application/improvements: Such type of solar air collector can be used in drying of fruits, crops; space heating for greenhouse, residential building etc. Keywords: Heat Gain, Heat Loss, Thermal Efficiency, Thermal Storage, Two-Pass Solar Air Collector

Heat transfer and friction factor correlations for solar air collectors with hemispherical protrusion artificial roughness on the absorber plate

In order to improve the efficiency of solar air collectors, this paper presents a novel solar air collector with hemispherical protrusion/dimple on the absorber plate, and analyses the performance from the two aspects of optics and thermodynamics. For the purpose of enhancing the absorption rate, the optical path shinning on the dimple and protrusion artificial roughness was simulated by using TRACEPRO software. The optical path of hemispherical and the spherical cap dimple was simulated too. The conclusions show that the hemispherical dimple is the best in term of the optics. Then the heat transfer performance of the hemispherical protrusion (back of the dimple) was investigated by experiments. The investigation has covered Reynolds number (Re) ranging from 3000 to 11,000, relative roughness height (e/Dh) from 0.033 to 0.1and relative pitch (p/e) from 3.5 to 5.5. In order to determine the enhancement in heat transfer and increment in friction factor, values of Nusselt number and friction factor have been compared with those of smooth duct under similar flow conditions. Correlations for Nusselt number and friction factor have been developed for solar air collector with such hemispherical protrusion artificial roughness, which can provide reference for the design of this kind of collector.

The Parameter Analysis and Performance Comparison of Solar Air Collector

With the social progress and the development of the world economy, the contradiction between energy demand and supply is increasingly outstanding，so saving energy is the important task which the human are facing. Solar energy as a renewable clean energy is one of the potential energy applying on buildings. This article analyzes the geometric parameters of the solar air collector and summarizes the baffle types of the solar air collector and puts forward to methods improving the efficiency of solar air collector.

Designing and Evaluating an Innovative Solar Air Collector with Transpired Absorber and Cover

Applying solar collectors is a popular tool for harnessing solar energy. In this work, a flat plate solar air collector was investigated under direct solar radiation in an endeavor to enhance the thermal efficiency of solar air collector with a slatted glass cover, perforated absorber aluminum sheets (porosity 0.0177, 0.0314 and absorber thickness of 1.25, 2.5 mm) which is the most suitable for a solar dryer. The effects of porosity and thickness on absorber performance of collector were evaluated. Six levels of air mass flow rates (0.0056 to 0.0385 kg m−2 s−1) were adopted. The tests were conducted in three replications on very clear sky days in September and October. The experimental results showed that thermal efficiency of collector was increased by an increase in the porosity of the absorber. The absorber with lower porosity showed a better thermal efficiency at lower air mass flux. In the minimum air flow rate, absorber efficiency with porosity 0.0177 and 0.0314 was 0.31 and 0.29, respectively, whereas at the maximum flow, efficiency showed an enormous change of 0.83 and 0.88, respectively. This solar air heater can be used for drying agricultural products, heating the space of greenhouse, and so forth.

Thermal performance of an solar air collector for drying grain

A physical model about a solar air collector has been constructed, the thermal preformance of the collector has been analysed, an experiment has been done. The present paper compare the data of experiment with theoretical analysis. Study proves that the efficiency of solar air collector will increase when the mass air flow increase, the efficiency of solar air collector varies from 38. 0% to 74. 6% when the mass air flow varies from 0. 01348 kg/m2 to 0. 04621kg/m2, the air temperature rise varies from 29. 0oC to 13. 4oC.