Double Pass Solar Air Heater Research Articles

Effect of roughness elements on thermal and thermohydraulic performance of double pass solar air heater duct having discrete multi V-shaped and staggered rib roughness on both sides of the absorber plate

ABSTRACTIn this work, an experimental setup consisting of a double pass solar air heater duct provided with discrete multi V-shaped and staggered rib as artificial roughness on both sides of the absorber plate has been designed and fabricated. The parameters of interest investigated experimentally cover a wide range of Reynolds number (Re) from 2000 to 20000, relative staggered rib pitch (p’/p) from 0.2 to 0.8, relative staggered rib size (r/e) from 1 to 4, and relative roughness width (W/w) from 5 to 8. Experimental data related to heat transfer, pressure loss, and thermohydraulic performance has been determined. Substantial improvement has been obtained with some penalty of friction losses.

Experimental Investigation of Thermal Performance of a Single and Double Pass Solar Air Heater with Arc Like Structures as the Absorber Plate

Experimental Investigation of Thermal Performance of a Single and Double Pass Solar Air Heater with Arc Like Structures as the Absorber Plate

Artificial bee colony algorithm for thermohydraulic optimization of flat plate solar air heaters

Determination of thermal efficiency is not a sufficient tool for solar air heaters because of disregarded energy consumption by fans. Most of the solar air heaters are equipped with fans in order to overcome pressure drops. Thermohydraulic efficiency is more favorable than thermal efficiency in terms of the design of solar energy conversion systems. In this present study, Artificial bee colony (ABC) based optimum design and operation algorithm is developed for Single pass solar air heater (SPSAH) and for Double parallel pass solar air heater (DPPSAH) which maximizes thermohydraulic efficiency. In order to solve the algorithm, channel depth is treated as a design variable, and air mass flow rate is defined as an operation parameter. Furthermore, energy balance equations are written for solar air heaters and solved for steady-state condition. As a result, optimum design and operation values are obtained from the algorithm for different collector lengths and solar insolation levels.

Performance studies on a forced convection solar dryer integrated with a paraffin wax–based latent heat storage system

This manuscript presents the performance studies on a forced convection solar dryer integrated with a paraffin wax-based shell and tube latent heat storage unit. The solar dryer consists of two double-pass solar air heaters, a paraffin wax-based shell and tube latent heat storage module, a blower, and a drying chamber. The dryer was tested by drying 20kg of red chilli in the drying air temperature range of 36–60°C. The initial average moisture content of the chilli was 73.5% (w.b.) and was reduced to the final moisture content of 9.7% (w.b.) in 4 consecutive days. The dryer was operated daily for 10h from 8:00h to 18:00h. The performance of each component of the drying system was evaluated using energy and exergy analyses. The average energy and exergy efficiency of the first solar heater were found to be 32.4% and 0.9%, respectively while for the second solar heater connected in the series with the first one were 14.1% and 0.8%, respectively. The energy and exergy efficiency of the latent heat storage unit were in the range of 43.6–49.8% and 18.3–20.5%, respectively. The exergy efficiency of the drying chamber was found to be between 24.6% and 98.1% with an average of 52.2%. The specific energy consumption of the chilli and the overall efficiency of the drying system were 6.8kWh per kg of moisture and 10.8%, respectively. The electrical energy consumption of the dryer was 0.7kWh per kg of moisture which was only 10.3% of the specific energy consumption of the chilli.

Performance Analysis of Double Pass Solar Air Heater with Bottom Extended Surface

Abstract A model of solar air heater with selective absorber coating with longitudinal fins at the bottom of absorber has been prepared to produce hot gases by consuming solar energy in day time. It is kept in position in such a way that air will flow due to forced convection and the entire setup placed at an angle of 15° to 17° inclination as per the considered global position (20.2961° N, 85.8245° E). Air flow rate is increased by applying a DC suction fan at outlet which sucks the air to flow over extended surfaces which are present at bottom inlet channel. Special selective coating applied over the entire Aluminum absorber plate to increase the heat absorbing capacity. Average ambient, inlet and plate temperatures are recorded daily along with solar flux. It is found that the instantaneous efficiency and air outlet temperature increased up to 69% and 94 °C respectively. Theoretical analysis has been made as well for the present set up. The difference between the theoretical and experimental values lies within 1.23-9.75%.

Experimental Study of a Solar Air Heater With a New Arrangement of Transverse Longitudinal Baffles

This study presents a new design for improving the convection heat transfer coefficients of double-pass solar air heater. Three cases were described by using a different number of transverse baffles (three, five, and seven) in the lower channel of the collectors; steel mesh sheets were also used to enlarge the heat transfer area. All collectors have a space of 25 mm between its glass covers and a 50 mm depth of air channel. Furthermore, this work examined the effect of air flow rate and baffles number on device's thermal efficiency and outlet temperature. The experimental results indicate raises in the thermal efficiency as the air flow rate goes from 0.011 kg/s to 0.038 kg/s. A maximum efficiency of 68% was obtained from the case of seven baffles at the air flow rate of 0.038 kg/s. Moreover, the difference between collector's inlet and outlet temperatures, ΔT, indicated an inverse relationship with air flow rate. Thus, the results show ΔT increases as the air flow rate reduced. The maximum temperature difference recorded was 54 °C, which achieved using seven baffled solar air heater at 0.011 kg/s air flow rate in the middle of the day. It has also been found that thermal efficiency of double-pass solar air heater is greater than single-pass solar air heater, using same air flow rate and number of baffles. Finally, the pressure drop associated with increasing the number of baffles and air flow rate was deliberated.

Experimental investigation on performance of a double pass artificial roughened solar air heater duct having roughness elements of the combination of discrete multi V shaped and staggered ribs

Double pass solar air heater (DPSAH) provided with roughness on each side of the absorbing surface is considered as a significant and interesting design advancement that has been used to enhance the performance of the collector. In this paper an experimental analysis has been conducted to study the effect of roughness parameters on thermohydraulic performance of double pass duct having discrete multi V shaped and staggered rib. The study has involved the values of Reynolds number (Re) from 2000 to 20000 and relative staggered rib size (r/e) from 1 to 2.5. Other parameters like relative staggered rib position (P′/P) of 0.2, angle of attack (α) of 60°, relative gap distance (Gd/Lv) of 0.70, relative pitch ratio (p/e) of 10, relative roughness height (e/D) of 0.043 and relative gap width (g/e) of 1.0 are kept constant. Based on the study, heat transfer and pressure drop in single and double pass mode have been estimated at range of ribs and performance parameters and results are compared with smooth ducts under same operating conditions. It has been found that the roughness geometry used on each side of the plate in double pass mode enhances both frictional losses as well as heat dissipation rate.

Performance improvement of a double-pass V-corrugated solar air heater under recycling operation

ABSTRACTThe device performance of double-pass V-corrugated solar air heaters with external recycle was investigated experimentally and theoretically. The comparison between V-corrugated and flat-plate collectors was made to show the thermal efficiency improvement with various operating parameters. The results show that the collector efficiency improvement of the recycling double-pass V-corrugated operation is much higher than those of the other configurations under various recycle ratios and mass flow rates. However, there exists the penalty on the power consumption increment due to implementing V-corrugated channel into the solar air heaters, an economic consideration on both the heat-transfer efficiency enhancement and power consumption increment for the double-pass V-corrugated device was also delineated. The experimental setup was carried out to validate the theoretical predictions, and the fairly good agreement between both results was achieved with the error analysis of 0.48-1.83%.

Heat transfer and friction factor correlation development for double-pass solar air heater having V-shaped ribs as roughness elements

In this present study, an experimental investigation has been carried out for a roughened double-pass solar air heater. The respective variation in other parameters, such as relative roughness pitch (p/e), relative roughness height (e/Dh), and angle of attack (α), were 5–20, 0.022–0.044, and 30°–75°, respectively. The effect of roughness and operating parameters on Nusselt number (Nu) and friction factor (f) has been determined, and the results are compared with those of a smooth absorber plate; considerable enhancement in both heat transfer and friction factor is noticed. Utilizing these experimental data, correlations for Nusselt number and friction factor correlations were also developed.

Energy and exergy analysis in double-pass solar air heater

In this study, an attempt is made to improve the energy and exergy performance of solar air heater by employing double pass with different absorber surface geometries (roughened, finned, and v-corrugated wire mesh) in the second pass, and also by mounting longitudinal fins in the back side of the absorber plate (first pass). The effect of varied mass flow rate and solar intensity on temperature rise of air, energy efficiency, exergy gain and pressure drop at steady state condition was determined for different types of solar air heaters utilizing an indoor solar simulator. The temperature rise of air, thermal efficiency and exergy gain depends on mass flow rate, surface geometries of absorber and solar intensity, whereas the pressure drop depends on mass flow rate and surface geometries of absorber.

Performances of packed bed double pass solar air heater with different inclinations and transverse wire mesh with different intervals

Solar air heating is a technology in which the solar energy from the sun is captured by an absorbing medium and used to heat the air flowing through the heater. In this study, thermal performance of a double pass solar air heater has been investigated experimentally at different conditions. The experiments were conducted with different inclinations of the collector, with and without wire mesh vertically fixed at the second pass in transverse direction and with different mass flow rates. The effect of air mass flow rate, wire mesh pitch and collector inclination on temperature rise and thermal efficiency have been studied. Results show that efficiency increases with mass flow rate. For the same mass flow rate, the thermal efficiency increases with the decrease in the wire mesh pitch. The maximum daily average efficiency of air heater was 79.8% at 0.025 kg/s mass flow rate, 10 cm wire mesh gap and 9? collector inclination facing south. The highest collector efficiency was observed in solar air heaters with 10 cm wire mesh gap.

Analytical and Experimental Studies of Wire Mesh Packed Double-pass Solar Air Heaters under Recycling Operation

The device performance of a solar air heater featured with recycling as well as wire mesh packed was investigated experimentally and theoretically. The deviations between the theoretical predictions and experimental measurements were calculated within 1.07-9.32%. Comparisons were made among different designs including the single-pass, flat-plate double-pass, and recycling wire mesh packed double-pass operations. The applications of wire mesh and recycle-effect concept to the present study were proposed in aiming to strengthen the convective heat transfer coefficient due to the turbulence enlargement. The collector efficiency of the recycling wire mesh packed double-pass operation is much higher than the other configurations under various recycle ratios and mass flow rates.

Thermal Performance Studies on Multi-pass Flat-plate Solar Air Heater with Longitudinal Fins: An Analytical Approach

In this study, thermal performance of double- and triple-pass solar air heater with longitudinal fins is mathematically evaluated. The effects of parameters, viz. mass flow rate, solar intensity and inlet temperature upon outlet temperature, thermal efficiency and increments in efficiency, power consumption are presented. The analytical solution for the mathematical model involving energy balance equations of different components of solar air heater is obtained using a MATLAB 8.1. Triple-pass solar air heater with fins exhibits better thermal performance, whereas double-pass solar air heater with fins is economically viable within the opted conditions. The results of the analytical models are in good agreement with experimental findings of earlier researchers.

Thermal performance assessment of recyclic double-pass flat and V-corrugated plate solar air heaters

Double-pass solar air heaters occupy an important place among solar air heating systems, because of minimal heat loss and maximum thermal efficiency with marginal heater size and cost. In the present work, investigations related to the thermal performance predictions have been carried out for double-pass flat and V-corrugated absorber plate solar air heaters under recycle operation. The mathematical models proposed herein are solved using an analytical approach that uses an iterative solution procedure. Furthermore, based on simulation results obtained from the analytical study, the optimum value of the recycle ratio, the mass flow rate, the absorptivity and the emissivity at which the heaters yield the maximum value of the thermal efficiency have been identified and presented using response surface methodology (RSM). The results of RSM revealed that the mathematical models are significant. In addition, results of the present study are validated and compared with previous studies. A reasonable agreement and significant improvement have been achieved.

A Review to Enhance the Efficiency of Double Pass Solar Air Heater

Solar air heater is a most popular device in the space heating and industrial processes applications. But solar air heater has lower heat-transfer coefficient between the absorber plate and the air stream, which results in a lower thermal efficiency of the heater. The solar air heaters efficiency can be affected by various parameters such as collector length, number of channels, depth of channels, type of absorber plate, number and material of glass covers, air inlet temperature and air velocity. The effect of fins, Baffles and porous media on double pass solar air heater will measured by this research study. This aim is to analyze the thermal efficiency of double pass solar air heater and measured the effect of different type of media on the efficiency of it. The effects of major parameters temperature difference, air velocity, pressure difference, mass flow rate of the air has been observed for these perform study.

An experimental investigation of performance of a double pass solar air heater with thermal storage medium

The performance of a double pass solar air heater was experimentally investigated using four different configurations. First configuration contained only absorber plate whereas copper tubes filled with thermal storage medium (paraffin wax) were added on the absorber plate in the second configuration. Aluminum and steel rods as thermal enhancer were inserted in the middle of paraffin wax of each tube for configurations three and four respectively. Second configuration provided useful heat for about 1.5 hours after the sunset compared to first configuration. Configurations three and four provided useful heat for about 2 hours after the sunset. The maximum efficiency of about 96% was achieved using configuration three (i.e. using Aluminum rods in the middle of copper tubes filled with paraffin wax).

Performance of a Photovoltaic or Thermal Double-Pass Solar Air Heater with Different Fin Configurations

Performance of a Photovoltaic or Thermal Double-Pass Solar Air Heater with Different Fin Configurations

Energy and Exergy Analysis of Multi-Pass Flat Plate Solar Air Heater—An Analytical Approach

In this paper, a mathematical model based on the energy balance equations is developed to study the energy and exergy performances of single, double, and triple pass solar air heaters. The energy and exergy performances of solar air heaters are determined by simulation using Matlab-8.1. The influence of mass flow rate on the rise in air temperature, energy efficiency, improvement efficiency, exergy efficiency, and irreversibility are studied. The energy and exergy performance of the triple pass is higher than the single and the double pass conditions. The results obtained from the analytical models are in good agreement with experimental data reported by earlier researchers.

Recycle Effect on Device Performance of Wire Mesh Packed Double-Pass Solar Air Heaters

A new device for inserting an absorber plate to divide a flat-plate channel into two subchannels to conduct double-pass wire mesh packed operations was developed. The proposed wire mesh packed device improves the heat transfer efficiency substantially as compared that to flat-plate single-pass and double-pass operations using the same working dimensions, and the improvement of device performance was investigated experimentally and theoretically. Good agreement between the theoretical prediction and the measured values from the experimental results was achieved. Considerable heat transfer improvement was obtained employing wire mesh packed double-pass operations under the absorber plate with external recycle. The influences of recycle ratio on the heat transfer efficiency and the power consumption increase were also discussed.

Investigation of single and double pass solar air heater with transverse fins and a package wire mesh layer

The purpose of this work is to construct and test single-pass and double-pass solar air heaters (SAHs) with four transverse fins. These fins were painted dark black and placed transversely to create four equal-spaced sections. Sixteen steel wire mesh layers were located between these fins as an alternative to an absorber plate; they had a cross-sectional area of 0.18cm×0.18cm and an internal diameter of 0.02-cm. In this project, the thermal efficiency and outlet temperature were studied in a geographic area located in the city of Famagusta, North Cyprus. The experimental results indicate that the thermal efficiency increases as the air flow rate increases for the range of (0.011-0.032)kg/s. The maximum efficiency obtained using the 7.5-cm high collector was 62.50% for the double-pass SAH and 55% for the single-pass SAH at an air flow rate of 0.032kg/s. Moreover, the thermal efficiency further increases by decreasing the height of the lower air pass of the double-pass SAH. The difference between the inlet temperature and outlet temperature, ΔT, indicated an inverse relationship with air flow rate: ΔT increased as the air mass flow rate decreased. The maximum differences (ΔT) observed were 45.30K for the double-passes SAH and 39.9K for the single-pass SAH at 0.011kg/s, which were recorded during the middle of the day with a maximum solar intensity. The results demonstrate a significant improvement in the thermal efficiency and outlet air temperature.