Performance Of Solar Air Heater Research Articles

A Simple and Novel Technique for Improving Double Pass Solar Air Heater Performance

A Simple and Novel Technique for Improving Double Pass Solar Air Heater Performance

Thermal performance analysis of apex-up discrete arc ribs solar air heater-an experimental study

The most efficient way to enhance the heat transfer performance of the Solar Air Heater (Sol-AHs) duct is by providing an artificial roughened plate. The present study compared the Thermo-hydraulic performance of a novel apex-up discrete arc rib absorber plate Solar Air Heaters (Sol-AHs) with existing best downstream flow ribs geometries. Furthermore, the parameters air flow angle of attack (α) of 30°, 45° and 60° and Reynolds number of 3000–14000 are examined by considering relative gap width (g/e) as 4, rib height to hydraulic diameter (e/Dh) as 0.045, a ratio of rib pitch to rib element diameter as 10, number of gaps as three. The results show that the new apex-up discrete arc rib absorber plates have superior thermal performance than the existing best apex-down ribs geometries. Maximum augmentation in Nu achieves an α of 30° that is 2.92 times the smooth plate. Thermo-hydraulic performance (THPP) is observed to be optimum at Re of 10000 and α of 30°. Correlation for heat transfer and roughness function obtained for varying air flow angle of attack.

Experimental Performance of Solar Air Heaters for Drying Applications

This paper presents the results of an experimental investigation on an indirect active type of solar dryer, using two distinct solar air collector and their impacts on drying agricultural products. The thermal performance of the proposed collectors has been evaluated using the first and second laws of thermodynamics. Experimental observations were done in climatic conditions Gödöllő, Hungary on the 2nd and 9th of October 2017. The experiments were also carried out to dry 2 kg of sliced apples spread over the drying trays. The mas flow rate of air was maintained as 0.038 kg/s and the dryer was operated from 10:00 a.m. to 3:00 p.m. When a double-pass solar air collector's results are compared to a single-pass solar air collector's, it's evident that the double-pass solar air collector produces much more energy and efficiency. The experimental results showed that single-pass and double-pass collectors have daily efficiencies of 42.77% and 56.10%, respectively, with average exergy efficiency values ranging from 31% to 49% for single-pass and 51% to 67% for double-pass. The most significant aspect determining the collectors' thermal efficiency was the temperature rise between the collector outlet and inlet. The average drying efficiencies of the solar dryer for the single and double-pass collectors were evaluated as 12.16% and 16.45%, respectively. The maximum temperature rise for double-pass was determined to be 20 °C, whereas single-pass was found to be 6.5 °C. Furthermore, the highest drying rate was achieved when sliced apples were dried with a double-pass collector mode. It reduced 52% of the water content in the apple in the same amount of time as single-pass drying, compared to 35% in the case of single-pass drying.

Effect of roughness parameters on performance of solar air heater having artificial wavy roughness using CFD

The current study used Ansys FLUENT software to perform a computational fluid dynamics analysis of a solar air heater with artificial wavy roughness. Roughness elements were studied for twelve wavy surface configurations with rib heights (e) of 0.7 mm, 1 mm, and 1.4 mm and pitch (p) of 10, 15, 20, and 25 mm. A 2D computational domain is modelled and the involved differential equations are solved using a finite volume method. To solve the transport equations for turbulent flow and energy dissipation rate, the RNG k-ε turbulence model with enhanced wall function is employed. For a uniform heat flow of 1000 W/m2, the effect of roughness parameter on Nusselt number, friction factor, and thermo-hydraulic performance parameter (THPP) is investigated. On the basis of the THPP, the best geometric parameter values are found in the Reynolds Number (Re) range of 3800–18,000. At Re of 12,000, the optimal THPP is 1.96, which corresponds to a rib height of 0.7 mm and a pitch of 15 mm.

Techniques used in Evaluating Performance of Solar Air Heater (SAH) Comprised of Winglet Type Roughness- A Review

There are multiple resource of energies but if we talk about renewable energy then solar energy is one of the renewable energy which is in demand because it is feasible and cheap. Flat - plate solar air heaters (SAHs) are simplistic and stylish, and their heating pathway of implementation requires care and support. increasing Room temperature, elimination of moist from farm commodities, increasing temperature of industrialized goods, hardening of wood or timber, and other uses for SAHs are frequent. well there are several issues in SAH, but the biggest issues with the SAH is its ineffectiveness, which is caused by atmosphere's lower heat transferring ability. We present introduces on the work performed by a lot of scientists to boost the effectiveness of solar air heaters (SAHs) with various kinds of roughness area in this research article.

An Assessment of Heating Load Reduction by a Solar Air Heater in a Residential Passive Ventilation System

In this paper, the authors examined the technology to maximize the use of renewable energy. Passive ventilation systems are expected to reduce the energy consumption of the fan and the maintenance burden. In addition, the wall-mounted solar air heater can supply thermal energy without using any energy at all. Therefore, this paper presents a “passive ventilation system with a solar air heater” that combines a passive ventilation system with the solar air heater to preheat the air. This system can reduce the ventilation load. To evaluate the solar air heater performance in a real environment, we developed a simulation for calculating the heat collection capacity of the solar air heater, and then the system was implemented in a real building for verification. The simulation performs hourly unsteady calculations, allowing for accurate evaluation of the annual simulation. Based on the measurement results, the effects of heating load reduction and prediction methods are presented. The solar air heater reduced the monthly ventilation load by up to 50% or more, and by at least 15%. It was also confirmed that there was a high correlation between the actual measurements and the simulation results.

Study and analysis of performance of solar air heaters with different inlet temperatures

Energy is the foundation of a sustainable and quality life. In many structures, we need energy to meet our daily needs. The rate of energy consumption is a pattern or gradual lifestyle. Extensive energy sources can be organized into two classifications: regular and non-regular. Solar air heaters are widely used as energy storage equipment to provide warm air at medium temperatures for heating and drying applications. An attempt was made to transfer heat through the absorbent plate using roughness. The experimental assembly was made using several components such as flat glass, wood, collector, entrance and exit door. The collector produces hot air with the aid of solar radiation.

Effects of Louvered Parameters on Exergetic Performance of Louvered Finned Solar Air Heater

The aim of the present study to improve the performance of solar air heater because of low thermo-physical properties of air. In the current work, an attempt has been made to improve the performance of the heater by employing louvered fins to the absorber plate, as it not only enhances heat transfer coefficient but also improve heat transfer area. The effect of exergy performance on the geometrical parameters of louvered fin i.e., louvered angle, louvered pitch and louvered length has been studied and analyzed. The results are compared to plane solar air heater (PSAH) to evaluate the effectiveness of louvered finned solar air heater (LFSAH). The exergy efficiency of LFSAH is comparatively higher for all the operating conditions except for higher mass flow rate where it may even go below that of PSAH; possibly due to the higher pressure drop and more loss of exergy at high mass flow rate. In addition, the results conclude that for louvered parameters viz., louvered angle 20°, fin pitch to louvered pitch ratio 0.75 and louvered length to louvered pitch ratio 1.25, high exergy performance of SAH is obtained as compared to other louvered parameter values.

Parametric analysis of artificial rib roughness for the enhancement of thermohydraulic performance of solar air heater: A review

Solar air heaters (SAHs) convert incident solar radiation to thermal energy on an absorber plate. Smooth absorber plates have a low convective heat transfer rate in traditional ducts. Artificial rib roughness is applied to the bottom sides of the absorber plate in order to improve heat transfer in SAHs. However, when the rib roughness is employed over the absorber plate of the airflow side, it also increases the pressure loss due to friction. The purpose of this work is to provide researchers with a scientific perspective on the geometry, structure of ribs, flow directions, and laminar zone in order to maximize heat transfer and reduce friction. This review article discusses different roughness parameters, various artificial roughness geometries, and thermohydraulic performance. Nusselt number and friction factor correlations have also been incorporated in this review article which is developed by various scientists based on their respective experimental results for various roughness parameters. The paper also provides a thorough analysis of current research, summarises prior developments, and speculates on potential future routes for developing new heat transfer systems. Furthermore, this review paper will assist researchers and academics in developing a sound understanding of the effects of roughness on the absorber plate.

Numerical Simulation of Solar Air Heater using Paraffin Wax-Aluminum Compound as Phase Changing Material

This paper presents a theoretical investigation of solar air heater using phase change material (PCM). PCM used in present configuration is homogenous mixture of paraffin wax with Aluminium powder. The purpose of using Aluminium powder with paraffin wax is to increase the thermal conductivity. PCM mixtures are encapsulated in cylinders and are used as solar absorbers. Using MATLAB program, the effect of different parameters is studied. It has been observed that with increase in mass flow rate, air outlet temperature decreases and freezing time of cylinder decreases. However, at constant mass flow rate, with increase in cylinder radius, air temperature decreases and while freezing time increase sharply. The different parameters have to be chosen such that performance of solar air heater can be optimized.

Heat transfer and performance analysis of SAH having new transverse finned absorber of lateral gaps and central holes

An experimental work is presented on the performance of solar air heater (SAH) has new designed absorber of finned transverse plate of lateral gaps and central holes. Moreover, a complete heat transfer analysis of the radiation and convection and SAH thermal performance are presented and discussed. The performance of this transverse SAH (TR_SAH) is compared with identical conventional flat plate SAH (FP_SAH) for single (SP) and double-pass (DP) airflow and air mass flow rates (AMFR) of 0.025, 0.05, and 0.075 kg/s. The experimental study is performed under hot climate conditions of Upper Egypt. The findings show that for all studied cases, TR_SAH has higher energy gain, output air temperature, thermal efficiency, and Nusselt number on the absorber plate, thermal-hydraulic performance parameter, and pressure drop compared to FP_SAH. The energy loss and radiation and convection Nusselt number on the TR_SAH glass plate is lower than that of FP_SAH. The maximum TR_SAH energy efficiency of value of about 89% is achieved in the case of DP airflow and high AMFR of 0.075 kg/s, with an enhancement of 24.2% compared to FP_SAH. The higher TR_SAH efficiency at these conditions reflects the optimal TR_SAH absorber design especially at high AMFR and using DP airflow. Despite TR_SAH air pumping power is greater than FP_SAH but it has a negligible effect on net energy gain.

Solar air heater having multiple V-ribs with Multiple-Symmetric gaps as roughness elements on Absorber-Plate: A parametric study

Conversion of solar energy into thermal energy using solar collectors is the most promising way for itsapplicability. Artificial roughness applied underside of the solar heat-collector is a preferably advantageous technique to enhance the solar air heater performance. In the present study, a comprehensive parametric analysis of the multi-V-ribs-with-symmetric-multi-gaps type of roughness elements (which employed over the heat-collector plate) has been conducted. Two novel roughness parameters (discreteness ratio and aspect ratio) are introduced and their impact is analyzed on thermo-hydraulic performance of the solar air heater (SAH). Moreover, relative roughness width, relative gap width, relative rib-height and relative rib-pitch impact are also assessed. The output parameter (i.e., Nusselt number and friction factor) has been estimated from the experimentally measured data under steady-state conditions. An increment of 6.46 times in Nusselt number along with 5.67 times in friction factor is observed in a comparison to a smooth SAH. The maximum thermo-hydraulic performance parameter for the present investigation is 4.24, which is comparatively higher. The generalized mathematical expressions for Nusselt number and friction factor are developed. The predicted results are found in the deviation of 7.28% and 8.45% for Nusselt number and friction factor.

Factors influencing the performance of solar air heater (SAH) having artificial coarseness: a review

A review of studies focused on promoting the rate of heat transfer with the help of an optimum rise in friction factor, by offering a simulated irregularity to the interior surface of the absorber plate of SAH, is expressed. In this article an effort has been made to explore different coarseness configurations as used by number of researchers to boost the SAH heat transfer rate. Furthermore, different correlations developed by researchers for Nusselt number and friction factor are also presented. On the basis of these correlations, thermohydraulic performance variable was calculated and attributed for various coarseness configurations. Friction factor and Colburn factor of various coarseness configurations have also been compared and presented. This review focused on use of different coarseness configurations with different coarseness parameter and flow parameter is deeply discussed from which future researchers can easily identify that which coarseness is to be used for designing SAH duct for the better augmentation of heat transfer and friction factor. It also helps the researchers to determine the optimum value of coarseness parameter so that the SAH works efficiently and effectively.

Energy, exergy, and economic analysis of tubular solar air heater with porous material: An experimental study

• Solar air heater having new designed tubular absorber is examined experimentally. • Assessment of the new tubular air heater with porous medium is presented. • Using porous material with tubular heater enhances its energy efficiency by 8.9% • Using porous media with tubular heater enhances its exergy efficiency by 8.2% • Tubular air heater is more effective compared to flat one based 4E analyses. The performance of solar air heater of having a new design tubular absorber of adjacent parallel tubes called tubular is investigated experimentally via energy, exergy, energy payback time, exergoeconomic, and enviroeconomic approaches. Moreover, the impact of utilizing porous material on the tubular heat performance is analyzed and compared to flat plate air heater at air mass flow rates; 0.075, 0.05, and 0.025 kg/s for single and double passes. Results indicate that the tubular heater has higher net energy gain, output air temperature, energy and exergy efficiencies, and smaller energy loss compared to the flat heater. Using porous material and double pass increases the output air temperature of tubular air heater by 3.4 °C and flat one by 17.7 °C at 0.025 kg/s. Moreover, utilizing porous material with the tubular heater at 0.075 kg/s enhances the energy efficiency by 3.5% and 8.9% and exergy efficiency by 8.2% and 0.9% for single and double pass, respectively. Air pumping power of the tubular heater is greater than flat but its value is very small to influence the tubular net useful energy. Finally, the tubular air heater is more effective compared to flat based on energy payback time, energy cost, exergoeconomic, and enviroeconomic parameters.

Absorber Type Optimization for Night-Shift Operation of Solar Air Heater

In the current study, the effect of using heat storage materials aimed at the night shift operation was studied by simulation tools. The Finite Volume Method (FVM) is used as a method to discretize the governing equations in the 2-D domain, and the RNG K- turbulence model is applied for simulation. The effect of absorption type based on five different materials such as Aluminum, Water, Asphalt, Graphite, and Sand on the performance of solar air heaters (SAH) is carried out thermally. The results show that the optimum material to obtain the maximum difference in temperature (38.32 K) between the absorber and the surrounding occurs once the asphalt is used, while the sand is the worst case, which is (31.71 K). Following, the focus is on the best absorber for night time operation. The Lumped Parameter Analysis is applied to the time required to dissipate the heat energy from the storage layer to reduce it to the assumed final temperature of a 5-degree difference (higher) than the ambient. After solving the transient equation, it is found that water can operate the system for a longer period (4.31 hrs.) as well as Graphite can operate the system for a shorter period (0.46 hrs.). Then ten different velocities in the entry section are used to consider the influences on the system performance. The results show that the velocity has a significant effect on the outlet temperature and operation period for night time.

Optimization of tube arrangement and phase change material for enhanced performance of solar air heater- A numerical analysis

Application of Solar Air Heater (SAH) could be extended to off sunshine hours by integrating SAH with a Thermal Energy Storage System (TESS). Design optimization of TESS will enhance thermal performance of SAH integrated with TESS. Mass flow rate and inlet temperature of air, type of Phase Change Material (PCM), alignment and dimensions of tubes in TESS play an important role in its design optimization. In the present study, numerical analysis using ANSYS FLUENT was carried out to optimize the design of TESS. Mass flow rate of air in terms of velocity at the inlet was changed from 3.5 m/s to 5.5 m/s in a step of 0.5 m/s. Three different PCMs including paraffin wax, n-octadecane, calciumchloride hexahydrate (CaCl2•6H2O) were considered. Inline, staggered and circular arrangement of tubes were considered in the TESS. Temperature of air at inlet to TESS is changed to 40 °C, 50 °C, 60 °C, 75 °C, 100 °C and 125 °C. Results are obtained in terms of average tube wall temperature, average PCM temperature in tubes, average surface heat transfer coefficient and average heat absorbed by PCM. Tubes in staggered arrangement increased heat absorbed by PCM by 10.45% and 48.03% respectively with paraffin wax and CaCl2•6H2O as PCM compared to tubes in inline arrangement. There is insignificant improvement (0.09%) between staggered and inline grid arrangements when n-octadecane was used as PCM. Tubes in circular arrangement increased heat absorbed by PCM by 9.17%, 1.55% and 1.08% respectively with paraffin wax, n-octadecane and CaCl2•6H2O as PCM compared to tubes in staggered arrangement. Similarly, it increased heat absorbed by PCM by 17.89%, 1.63% and 48.59% respectively compared to tubes in inline arrangement.

Experimentally validated 3D simulation and performance optimization of a solar air duct with modified conical vortex generators

Providing flow-disturbing components on the effective heat transfer area of the absorber plate is the most efficient thermohydraulic performance enhancement technique employed in a solar air heater. The present investigation aims at finding the optimal set of geometrical parameters for a solar air heater with modified conical vortex generators. Optimization approach is adopted considering the thermohydraulic performance of the proposed design of the solar air heater. Experimentally validated numerical simulations for different parameters of the vortex generators like relative pitch ratio of 8 to 15, relative vortex generator height ratio of 0.17 to 0.34 and Reynolds number range of 3000 to 16,000 are optimized using Grey relational analysis and Overall evaluation criteria. Performance of solar air heater under different investigated parameters is analysed using performance indices like Nusselt number, friction factor, thermal performance enhancement factor, friction enhancement factor and thermo-hydraulic enhancement factor. A maximum Nusselt number of 142.4 is observed for relative pitch ratio of 8 and relative vortex generator height ratio of 0.34. Optimized geometrical parameters are predicted for different percentage weightage set on thermal and hydraulic performances. Correlation equations for Nusselt number and friction factor are developed for the overall range of investigated parameters.

CFD Analysis on Rectangular Shaped Variable Height Turbulators Fitted in a Solar Air Heater for Improved Thermal Performance

There have been various studies on the effect of turbulators of different shapes integrated with the absorber plate's underside for improved performance. However, a study on rectangular profiled variable height turbulators along the flow direction is not available. In this paper, an attempt has been made to explore in detail this aspect. The roughness of different kinds on the heat transfer surface mainly creates turbulence and breaks the laminar sub-layer, enhancing the heat transfer rate. In the present work, a solar air heater's performance incorporated rectangular profiled variable height turbulators of different configurations, i.e. increasing height turbulators, decreasing height turbulators and constant height turbulators, are being numerically investigated. For the base model, i.e. without any turbulators, a numerical and experimental analysis has been carried to establish the present analysis's overall validity. All tested turbulators show better performance compared to the base model. Configuration, which has to decrease in height towards the flow direction, shows relatively higher performance in terms of heat transfer coefficient, outlet temperature, and thermohydraulic enhancement factor than that of the other configurations. It is found from the analysis that for decreasing height turbulators, there is an enhancement of 21% to 0.2% for the Reynolds number from 3000 to 15000, respectively. For the higher Reynolds number above 15000, the THEF will be lesser than the base model.

Numerical Analysis of a Solar Air Heater With Jet Impingement—Comparison of Performance Between Jet Designs

Abstract One of the ways to improve the performance of solar air heaters (SAHs) is to use jet impingement on the absorber plate to cause turbulence mixing of air in contact with the plate and thereby augment the heat transfer coefficient. Although the jet impingement is a prospective way of improving the SAH performance, comparison of performance between jet designs is not performed so far. The objective of this work is to compare the thermo-hydraulic performance of a SAH with jet impingement through conical protruding jets and circular jets using finite element method based comsol multiphysics software. The simulation studies were conducted for solar radiation in the range 500–1000 W/m2 and mass flowrate in the range 0.01–0.028 kg/s. The flow physics of the jet impingement process is investigated to understand the heat transfer and fluid flow behavior of the SAH with the chosen jet designs thereby obtain their performance insights. The outlet hot air temperature from the heater and its thermal efficiency are compared for different mass flowrates and solar radiations. Also the temperature distributions in the jet plate with the jet configurations are captured and their heat transfer characteristics compared with understand the thermo-fluidic behavior of the SAH. The results demonstrate improved performance of the novel conical protruded jet design that enhances the thermal efficiency up to 78.52%, which is an increase of 13.53% compared with the circular jet design. More elongated streamlines and higher turbulent kinetic energy with increased mass flowrate leading to a wide jet affected area inside the duct are the main reasons of its improved performance.

Thermo-Hydraulic Performance Characteristics and Optimization of Protrusion Rib Roughness in Solar Air Heater

To enhance the thermal performance of solar air heaters (SAHs), protrusion ribs on the absorber are considered to be an attractive solution due to their several advantages. These ribs do not cause a significant pressure drop in the SAH duct and help to enhance the heat transfer to flowing air. On the other hand, a degree of roughness of the protrusion rib on the absorber can be produced by pressing the indenting device without adding additional mass. In this paper, the thermo-hydraulic performances of different roughnesses of the conical protrusion rib on the absorber plate have been evaluated by the mutual consideration of thermal as well as hydraulic performance in term of net effective efficiency. Therefore, an analytical technique has been exploited to predict the characteristics of the net effective efficiency under various operating conditions, such as the flow Reynolds number, temperature increase parameter and insolation. The effects of the conical protrusion rib roughness—namely the relative rib pitch (p/e) and relative rib height e/D) in the ranges of 6–12 and 0.200–0.044, respectively—have been evaluated. The highest value of net effective efficiency of 70.92% was achieved at a p/e of 10 and e/D of 0.0289. The optimization of the rib parameters has been carried out in different ranges of temperature increase parameters for the highest values of net effective efficiency. A unique combination of rib parameters—a p/e of 10 and e/D of 0.044—are observed to lead to the best performance when operating a solar air heater with a temperature increase parameter of more than 0.00789 K·m2/W.