The Experts below are selected from a list of 2595 Experts worldwide ranked by ideXlab platform
Ho-ming Yeh - One of the best experts on this subject based on the ideXlab platform.
-
upward type flat Plate solar air heaters attached with fins and operated by an internal recycling for improved performance
Journal of The Taiwan Institute of Chemical Engineers, 2012Co-Authors: Ho-ming YehAbstract:Abstract The effect of internal recycle on the collector efficiency in upward-type flat-Plate solar air heaters attached with fins has been investigated theoretically. The equations for predicting the outlet air temperature and the collector efficiency were derived from the energy balances on the Absorbing Plate and flow air. Considerable improvement in collector efficiency is obtainable if collector is attached with fins to extend the heat-transfer area, and if the operation is carried out with an internal recycle to increase the fluid velocity, leading to improved heat transfer coefficient. The enhancement in collector efficiency increases with increasing reflux ratio, especially for operating at lower air flow rate with higher inlet air temperature. It is found that more than 100% of improvement in collector efficiency is obtained by recycling operation. Furthermore, the performance in the device operated with internal recycle overcomes that in the same-size device operated with external recycle.
-
collector efficiency of upward type double pass solar air heaters with fins attached
International Communications in Heat and Mass Transfer, 2011Co-Authors: Ho-ming Yeh, Tsungching ChenAbstract: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).
-
heat transfer enhancement in double pass flat Plate solar air heaters with recycle
Energy, 2005Co-Authors: Ho-ming Yeh, R C WangAbstract:This work theoretically and experimentally investigates a device for inserting an Absorbing Plate into the double-pass channel in a flat-Plate solar air heater with recycle. This method substantially improves the collector efficiency by increasing the fluid velocity. The results are represented graphically and compared with a downward-type single-pass solar air heater. Considerable improvement in heat transfer is obtainable by employing recycle-type double-pass devices instead of single-pass devices or a conventional double-pass heater with the same flow rate. The Absorbing Plate location influence on heat-transfer efficiency enhancement and the hydraulic dissipated power increment is also discussed.
-
collector efficiency of double flow solar air heaters with fins attached
Energy, 2002Co-Authors: Ho-ming Yeh, J Z HouAbstract:A design for inserting an Absorbing Plate to divide the air duct into two channels (the upper and the lower) for double-flow operation in solar air heaters with fins attached over and under the Absorbing Plate has been investigated both experimentally and analytically. The present work is restricted to the case where the outside air is being heated directly, and the configuration investigated here will have lower collector efficiency if the inlet-air temperature is substantially higher than the ambient temperature because of the far greater potential for heat loss from the top. However, the double-flow device introduced here was designed for creating a solar collector with heat-transfer area double between the Absorbing Plate and heated air. This advantage may compensate for the heat loss from the top when the inlet-air temperature is higher than the ambient temperature. The agreement of the theoretical predictions with those measured values from the experimental results is fairly good. Considerable improvement in collector efficiency of solar air heaters with fins attached is obtained by employing such a double-flow device, instead of using a single-flow example and operating at the same total flow rate. Both the theoretical predictions and experimental results showed that the optimal fraction of airflow rate in upper and lower subchannels is around the value of 0.5. The effect of the flow-rate ratio of the two air streams of flowing over and under the Absorbing Plate on the enhancement of collector efficiency is also investigated.
-
the improvement of collector efficiency in solar air heaters by simultaneously air flow over and under the Absorbing Plate
Energy, 1999Co-Authors: Ho-ming Yeh, Junze HouAbstract:The performance of double-flow type solar air heaters, in which air is flowing simultaneously over and under the Absorbing Plate, is more effective than that of the devices with only one flow channel over or under the Absorbing Plate because the heat-transfer area in double-flow systems is double. The effect of the fraction of mass flow rate in the upper or lower flow channel of a double-flow device on collector efficiencies, has also been investigated theoretically and experimentally. Considerable improvement in collector performance is obtained by employing a double-flow type solar air heater, instead of using a single-flow device, if the mass flow rates in both flow channels are kept the same.
Hikmet Esen - One of the best experts on this subject based on the ideXlab platform.
-
experimental investigation of thermal performance of a double flow solar air heater having aluminium cans
Renewable Energy, 2009Co-Authors: Filiz Ozgen, Mehmet Esen, Hikmet EsenAbstract:Abstract This study experimentally investigates a device for inserting an Absorbing Plate made of aluminium cans into the double-pass channel in a flat-Plate solar air heater (SAH). This method substantially improves the collector efficiency by increasing the fluid velocity and enhancing the heat-transfer coefficient between the absorber Plate and air. These types of collectors had been designed as a proposal to use aluminium materials to build absorber Plates of SAHs at a suitable cost. The collector had been covered with a 4-mm single glass Plate, in order to reduce convective loses to the atmosphere. Three different absorber Plates had been designed and tested for experimental study. In the first type (Type I), cans had been staggered as zigzag on absorber Plate, while in Type II they were arranged in order. Type III is a flat Plate (without cans). Experiments had been performed for air mass flow rates of 0.03 kg/s and 0.05 kg/s. The highest efficiency had been obtained for Type I at 0.05 kg/s. Also, comparison between the thermal efficiency of the SAH tested in this study with the ones reported in the literature had been presented, and a good agreement had been found.
-
artificial neural network and wavelet neural network approaches for modelling of a solar air heater
Expert Systems With Applications, 2009Co-Authors: Hikmet Esen, Filiz Ozgen, Mehmet Esen, Abdulkadir SengurAbstract:This paper reports on a modelling study of new solar air heater (SAH) system by using artificial neural network (ANN) and wavelet neural network (WNN) models. In this study, a device for inserting an Absorbing Plate made of aluminium cans into the double-pass channel in a flat-Plate SAH. A SAH system is a multi-variable system that is hard to model by conventional methods. As regards the ANN and WNN methods, it has a superior capability for generalization, and this capability is independent on the dimensionality of the input data's. In this study, an ANN and WNN based methods were intended to adopt SAH system for efficient modelling. To evaluate prediction capabilities of different types of neural network models (ANN and WNN), their best architecture and effective training parameters should be found. The performance of the proposed methodology was evaluated by using several statistical validation parameters. Comparison between predicted and experimental results indicates that the proposed WNN model can be used for estimating the some parameters of SAHs with reasonable accuracy.
-
modelling of a new solar air heater through least squares support vector machines
Expert Systems With Applications, 2009Co-Authors: Hikmet Esen, Filiz Ozgen, Mehmet Esen, Abdulkadir SengurAbstract:This paper reports on a modelling study of new solar air heater (SAH) system efficiency by using least-squares support vector machine (LS-SVM) method. In this study, a device for inserting an Absorbing Plate made of aluminium cans into the double-pass channel in a flat-Plate SAH. A SAH system is a multi-variable system that is hard to model by conventional methods. As regards the LS-SVM, it has a superior capability for generalization, and this capability is independent on the dimensionality of the input data. In this study, a LS-SVM based method was intended to adopt SAH system for efficient modelling. For modelling, different mass flow rates in flow duct and collector types are used and then for obtaining the optimum LS-SVM parameters, such as regularization parameter, and optimum kernel function and parameters, several tests have been carried out. The performance of the proposed methodology was evaluated by using several statistical validation parameters. It is found that root mean squared error (RMSE) value is 0.0024, the coefficient of multiple determinations (R^2) value is 0.9997 and coefficient of variation (cov) value is 2.1194 for the proposed radial basis function (RBF)-kernel LS-SVM method at 0.03kg/s air mass flow rate. It is found that RMSE value is 0.0135, R^2 value is 0.9991 and cov value is 2.9868 for the proposed RBF-kernel LS-SVM method at 0.05kg/s air mass flow rate. Comparison between predicted and experimental results indicates that the proposed LS-SVM model can be used for estimating the efficiency of SAHs with reasonable accuracy.
-
experimental energy and exergy analysis of a double flow solar air heater having different obstacles on absorber Plates
Building and Environment, 2008Co-Authors: Hikmet EsenAbstract:This paper presents an experimental energy and exergy analysis for a novel flat Plate solar air heater (SAH) with several obstacles and without obstacles. For increasing the available heat-transfer area may be achieved if air is flowing simultaneously and separately over and under the different obstacle Absorbing Plates, instead of only flowing either over or under the different obstacle Absorbing Plates, leading to improved collector efficiency. The measured parameters were the inlet and outlet temperatures, the Absorbing Plate temperatures, the ambient temperature, and the solar radiation. Further, the measurements were performed at different values of mass flow rate of air and different levels of Absorbing Plates in flow channel duct. After the analysis of the results, the optimal value of efficiency is middle level of Absorbing Plate in flow channel duct for all operating conditions and the double-flow collector supplied with obstacles appears significantly better than that without obstacles. At the end of this study, the exergy relations are delivered for different SAHs. The results show that the largest irreversibility is occurring at the flat Plate (without obstacles) collector in which collector efficiency is smallest.
Chaofeng Xia - One of the best experts on this subject based on the ideXlab platform.
-
analytical and experimental studies on the thermal performance of cross corrugated and flat Plate solar air heaters
Applied Energy, 2007Co-Authors: Wenfeng Gao, Wenxian Lin, Tao Liu, Chaofeng XiaAbstract:The cross-corrugated heaters consist of a wavelike Absorbing Plate and a wavelike bottom Plate, which are crosswise positioned to form the air flow channel. Two types of these heaters are considered. For the type 1 heater, the wavelike shape of the Absorbing Plate is along the flow direction and that of the bottom Plate is perpendicular to the flow direction, while for the type 2 heater it is the wavelike shape of the bottom Plate that is along the flow direction and that of the Absorbing Plate is perpendicular to the flow direction. The aims of the use of the cross-corrugated Absorbing Plate and bottom Plate is to enhance the turbulence and the heat-transfer rate inside the air flow channel, which are crucial to the improvement of efficiencies of solar air-heaters. To quantify the achievable improvements with the cross-corrugated Absorbing and bottom Plates, flat-Plate solar air-heaters which have both a flat Absorbing Plate and a flat bottom Plate, are also considered. The thermal performance of these three types of solar air-heaters are analyzed, measured and compared under several configurations and operating conditions. All the analytical and experimental results show that, although the thermal performance of the type 2 heater is just slightly superior to that of the type 1 heater, both of these cross-corrugated solar air-heaters have a much superior thermal performances to that of the flat-Plate one. It is also found that the use of selected coatings on the Absorbing Plates of all the heaters considered can substantially enhance the thermal performances of the heaters, whereas such a selected coating on the bottom Plates or/and the glass covers does not have such a significant effect on the thermal performances of the heaters.
Wenxian Lin - One of the best experts on this subject based on the ideXlab platform.
-
analytical and experimental studies on the thermal performance of cross corrugated and flat Plate solar air heaters
Applied Energy, 2007Co-Authors: Wenfeng Gao, Wenxian Lin, Tao Liu, Chaofeng XiaAbstract:The cross-corrugated heaters consist of a wavelike Absorbing Plate and a wavelike bottom Plate, which are crosswise positioned to form the air flow channel. Two types of these heaters are considered. For the type 1 heater, the wavelike shape of the Absorbing Plate is along the flow direction and that of the bottom Plate is perpendicular to the flow direction, while for the type 2 heater it is the wavelike shape of the bottom Plate that is along the flow direction and that of the Absorbing Plate is perpendicular to the flow direction. The aims of the use of the cross-corrugated Absorbing Plate and bottom Plate is to enhance the turbulence and the heat-transfer rate inside the air flow channel, which are crucial to the improvement of efficiencies of solar air-heaters. To quantify the achievable improvements with the cross-corrugated Absorbing and bottom Plates, flat-Plate solar air-heaters which have both a flat Absorbing Plate and a flat bottom Plate, are also considered. The thermal performance of these three types of solar air-heaters are analyzed, measured and compared under several configurations and operating conditions. All the analytical and experimental results show that, although the thermal performance of the type 2 heater is just slightly superior to that of the type 1 heater, both of these cross-corrugated solar air-heaters have a much superior thermal performances to that of the flat-Plate one. It is also found that the use of selected coatings on the Absorbing Plates of all the heaters considered can substantially enhance the thermal performances of the heaters, whereas such a selected coating on the bottom Plates or/and the glass covers does not have such a significant effect on the thermal performances of the heaters.
Wenfeng Gao - One of the best experts on this subject based on the ideXlab platform.
-
analytical and experimental studies on the thermal performance of cross corrugated and flat Plate solar air heaters
Applied Energy, 2007Co-Authors: Wenfeng Gao, Wenxian Lin, Tao Liu, Chaofeng XiaAbstract:The cross-corrugated heaters consist of a wavelike Absorbing Plate and a wavelike bottom Plate, which are crosswise positioned to form the air flow channel. Two types of these heaters are considered. For the type 1 heater, the wavelike shape of the Absorbing Plate is along the flow direction and that of the bottom Plate is perpendicular to the flow direction, while for the type 2 heater it is the wavelike shape of the bottom Plate that is along the flow direction and that of the Absorbing Plate is perpendicular to the flow direction. The aims of the use of the cross-corrugated Absorbing Plate and bottom Plate is to enhance the turbulence and the heat-transfer rate inside the air flow channel, which are crucial to the improvement of efficiencies of solar air-heaters. To quantify the achievable improvements with the cross-corrugated Absorbing and bottom Plates, flat-Plate solar air-heaters which have both a flat Absorbing Plate and a flat bottom Plate, are also considered. The thermal performance of these three types of solar air-heaters are analyzed, measured and compared under several configurations and operating conditions. All the analytical and experimental results show that, although the thermal performance of the type 2 heater is just slightly superior to that of the type 1 heater, both of these cross-corrugated solar air-heaters have a much superior thermal performances to that of the flat-Plate one. It is also found that the use of selected coatings on the Absorbing Plates of all the heaters considered can substantially enhance the thermal performances of the heaters, whereas such a selected coating on the bottom Plates or/and the glass covers does not have such a significant effect on the thermal performances of the heaters.