Double-pass Flat Plate Solar Air Research Articles

The Experimental Investigation of Double -Pass Solar Air Heater with V-Corrugated Plate, Phase -Change Material and Baffles Under Recycling Operation

The current paper presents an experimental work that had been implemented to observe the performance of an improved solar air heater and compared it with that of a conventional double-pass flat plate solar air heater. Improvements that have been added include the use of a V-shaped corrugated plate at an angle of 60 degrees, the addition of wood baffles in the lower pass and the use of phase-changing materials PCM as well as air recycling conditions. The heater was designed and tested under the weather conditions prevailing in the Duhok Governorate (latitude 36° 52' 1.52" N and longitude 42° 59' 18.42" E) in the Kurdistan Region of Iraq. The phase-changing material PCM is paraffin wax. The gathered results showed that the improvements that were added to the solar air heater significantly improved the performance at different mass flow values (0.037, 0.057, 0.077 kg/sec). For example, the maximum values of useful heat transfer at mass flow rates (0.037, 0.057, and 0.077kg/s) are 1.68, 1.86, and 2.34 kW, respectively, and the daily efficiency for improving and conventional heater value at mass flow rate 0.037kg/s for 15,16, and 17 of February on 2022 was (84% and 45%), (86% and 46%), and (91% and 60%), respectively.

PEMANFAATAN KOLEKTOR SURYA SEBAGAI ENERGI ALTERNATIF DESALINASI AIR LAUT UNTUK MENGATASI KRISIS AIR BERSIH

This research examined the effect of air velocity and the efficiency of double-pass flat plate solar air heater with two glass covers on the performance of solar desalination unit based on heat pump with using humidification and dehumidification processes. This unit consists of a heat pump, humidifier, dehumidifier, and double-pass flat plate solar air heater with two glass covers. The research was conducted in an indoor experiment. Solar energy generated from solar simulator using halogen lamps. In this research the air flow rate was varied at 3 metres per second, 4 metres per second, 5 metres per second, and 6 metres per second, while the intensity of solar radiation at 828 Watts per meter squared. At each variation in air velocity, sea water temperature was conditioned at a constant temperature of 45 degrees celcius, the compressor was operated at a constant rotation of 900 rpm, volumetric flow rate of sea water inlet 300 liters per hour into humidifier and sea water in this system was re-circulated. The research result showed that the volume of fresh water production increases with increasing air velocity inlet into humidifier. This solar desalination unit could produce fresh water maximum 2470 milliliters per hour in air velocity 6 metres per second.

Enhanced Double-Pass Solar Air Heater With and Without Porous Medium

An energy and exergy study has been done on a double-pass flat-plate solar air collector with and without porous medium embedded inside the lower channel of the collector. Energy conservation equations are used to derive the energy-governing equations for all components of the collector. A second law analysis (the second law of thermodynamics) was carried out to optimize the mass flow rate, which leads to optimization of the energy efficiency. Theoretical results for energy and exergy efficiencies are plotted for the cases of with and without embedded porous medium. Results of this research show that the porous medium embedded inside the lower channel leads to an increase in the thermal efficiency of the collector of more than 30% compared with the case without porous medium, hence showing the importance of employing porous medium in thermal solar collectors. On the other hand, the pressure drop in the air caused by friction with porous medium is not negligible and is also studied here, using the second law analysis.

EXTERNAL RECYCLE ON UPWARD-TYPE DOUBLE-PASS SOLAR AIR HEATERS

The external recycle effect on collector efficiency in an upward-type double-pass flat-plate solar air heater is investigated theoretically. Application of recycle to a solar air heater has two conflicting effects: the desirable effect of increasing the heat transfer coefficient and the undesirable effect of decreasing the heat transfer driving force (temperature difference). The theoretical predictions show that more than 150% improvement in collector efficiency is obtainable if external recycling is carried out in a way that the advantage effect compensates for the disadvantage effect. The collector performance improvement increases with increasing recycling ratio, especially when operating at a lower airflow rate with higher inlet air temperature. The collector efficiency obtained with a double-pass device with recycling improves the efficiency obtained with a single-pass device of the same size with recycling.

Collector efficiency of upward-type double-pass solar air heaters with fins attached

The collector efficiency of upward-type double-pass flat plate solar air heaters with fins attached and external recycle is investigated theoretically. The double-pass device was constructed by inserting the absorbing plate into the air conduit to divide it into two channels (the upper and lower channels). The double-pass device introduced here was designed for creating a solar collector with heat transfer area double as well as the extended area of fins between the absorbing plate and heated air. Moreover, the advantage of external recycle application to solar air heaters is the enhancement of forced heat convection strength, resulting in considerable device heat transfer performance improvement. This advantage may compensate for the remixing at the inlet which decreases the heat transfer transfer-driving force decrement (temperature difference).

A solar desalination system using humidification–dehumidification process: experimental study and comparison with the theoretical results

In this study, influence of the different system operating conditions on the performance of a solar desalination system using humidification-dehumidification process have been investigated experimentally under the climatological conditions of Ankara (40°N, 33°E), Turkey. An experimental set-up that consists of a double-pass flat plate solar air heater with two glass covers, pad humidifier, dehumidifying exchanger and water storage tank was designed and manufactured. Working principle of the set-up is based on the idea of closed water and open-air cycles. A series of tests were performed on it in outdoor environment, in order to assess the effect of mass flow rate of the feed water, process air and cooling water, double-pass flat plate solar air heater, initial water temperature and amount of the water inside the storage tank on the productivity of the system. Additionally, an evacuated tubular solar water heater unit was integrated to the existing system and the effect of this integration on the performance of the system was examined. Solar radiation, wind speed, relative humidity, mass flow rate of the feed water, process air and cooling water, mass of condensate water and temperatures at various locations were obtained during the experiments.The results of the experimental study showed that under certain operating conditions, the system productivity decreases about 15% if double-pass solar air heater is not used and significant improvement on the productivity of the system is achieved by increasing the initial water temperature inside the storage tank. In addition, productivity of the system increases with increasing the feed water mass flow rate and quantity of water inside the storage tank. However, productivity of the system remains approximately the same when the air mass flow rate is increased. Moreover, increasing the cooling water mass flow rate results in the improvement on the productivity of the system investigated. Finally, results obtained from the present investigation were compared with the theoretical study and a good agreement between them is observed.

Theoretical investigation of a humidification-dehumidification desalination system configured by a double-pass flat plate solar air heater

The aim of this study is to investigate theoretically the effect of different system operating conditions, types of air heater, and some different design parameters and a weather condition on a solar water desalination system performance under the climatological conditions of Ankara (40 °N,33 °E), Turkey. For this purpose, a computer simulation program based on the mathematical model is developed by means of MATLAB software. In this simulation program, the fourth order Runge-Kutta method is used to solve the energy balance equations numerically. The desalination unit is configured by a double-pass flat plate solar air heater with two glass covers, humidifying tower, storage tank and dehumidifying exchanger. The system used in this work is based on the idea of closed water and open air cycles. Air is heated by using a double-pass solar air heater whereas water is not heated. The system productivity is increased up to 8% by using a double-pass solar air heater compared to a singlepass solar air heater and decreased about 30% without double-pass solar air heater under the same operating conditions. Significant development on the productivity of the system is achieved by increasing the humidifier inlet water and air mass flow rates. At a constant water mass flow rate, however, the productivity of the unit increases with the increasing of air mass flow rate to an optimum value and decreases after that value. In addition, theoretical results indicate that there is a significant improvement on the system performance as the inital water temperature and water mass in the storage tank is increased. Moreover, increasing the cooling water mass flow rate and decreasing its temperature lead to appreciable improvement on the unit productivity. It is also found that, the system performance is strongly affected by the double-pass solar air heater area and slightly influenced by the bottom heat loss coefficient of the solar air heater and storage tank (especially, when its temperature is lower than the ambient air temperature). Finally, the productivity of the unit that consists of a double-pass solar air heater with two glass covers is not influenced by the wind speed variations as much as double-pass solar air heater with one glass cover.

06/00874 Heat-transfer enhancement in double-pass flat plate solar air heaters with recycle: Ho, D. C. et al. Energy, 2005, 30, (15), 2796–2817.

A brief introduction of the energy status quo is presented, followed by the existing solar thermal power plant technologies. The solar chimney power plant (SCPP) technology is presented. Later, a comprehensive introduction on the research and development of SCPP system is presented.

Effect of porous media on the performance of the double-pass flat plate solar air heater

The heat transfer characteristics and performance of the double-pass flat plate solar air heater with and without porous media are studied numerically. The mathematical models described the heat transfer characteristics of the double-pass flat plate solar air heater are derived from the energy conservation equations. The implicit method of finite-difference scheme is employed to solve these models. The effect of the thermal conductivity of the porous media on the heat transfer characteristics and performance is considered. The results obtained from the model are validated by comparison with experimental data of previous researchers. There is reasonable agreement between the present model and experiment.

On the performance and entropy generation of the double-pass solar air heater with longitudinal fins

The performance and entropy generation of the double-pass flat plate solar air heater with longitudinal fins are studied numerically. The mathematical models described the heat transfer characteristics of the double-pass flat plate solar air heater derived from the conservation equations of energy. The predictions are done at air mass flow rate ranging between 0.02 and 0.1 kg/s. The effects of the inlet condition of working fluid and dimension of the solar air heater on the heat transfer characteristics, performance, and entropy generation are considered.