The Experts below are selected from a list of 294 Experts worldwide ranked by ideXlab platform
Aouf A. Al-tabbakh - One of the best experts on this subject based on the ideXlab platform.
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Computer simulation of a two phase thermosyphon solar domestic hot water heating system
Energy Conversion and Management, 1999Co-Authors: Khalid A. Joudi, Aouf A. Al-tabbakhAbstract:The present work deals with a theoretical analysis by computer simulation of a two phase thermosyphon solar domestic hot water system using R-11 as a working fluid. The performance was studied by the aid of a simulation procedure for a typical day period divided into equal time intervals of 15 min. Instantaneous values of solar radiation intensity and ambient Temperature were applied at the beginning of each time step. The insolation was calculated according to the procedure suggested by ASHRAE. The variation of ambient Temperature during the day was approximated by a sine function. The variation of working fluid properties with Temperature was also taken into account. The computer program and calculation procedure were first validated by comparing the results with established results of single phase systems. Then, calculations were performed for the two phase thermosyphon system to evaluate mass flow rate, saturation pressure and Temperature in the collector and condenser, together with Tank Temperature, and collector and condenser thermal efficiencies. These calculated values were obtained for three cases, namely, the no loading case of no water withdrawal from the Tank, continuous loading and intermittent loading. The results obtained showed that, in the two phase system, the saturation pressure and Temperature increase continuously during the day and follow the Tank Temperature pattern. This makes the system pressure dependent on the Tank loading. The collector efficiency did not reveal a serious change with the loading condition. This behavior differs from that which occurs in the single phase system, where the collector efficiency increases considerably with loading. Comparison of the two phase system with a single phase system of the same collector area and Tank volume showed a significant increase in collector efficiency and Tank Temperature for the case of the two phase system.
Khalid A. Joudi - One of the best experts on this subject based on the ideXlab platform.
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Computational model for a prism shaped storage solar collector with a right triangular cross section
Energy Conversion and Management, 2004Co-Authors: Khalid A. Joudi, I.a. Hussein, Ammar A. FarhanAbstract:Abstract The performance of a prism shaped storage solar collector with a right triangular cross sectional area was investigated numerically. The ANSYS software release 5.4 was used for this purpose. Modifications were introduced embodying water properties and making the software compatible with the different types of loads. The behavior of parameters related to performance such as Temperature, velocity distributions, mean Tank Temperature, total stored energy and the best location of the inlet and outlet water flows were investigated systematically. A new idea of introducing an internal horizontal adiabatic partition was investigated. The length of the partition and its location along the height of the storage collector was analyzed to give optimum stored energy and maximum possible mean Tank Temperature. The results showed that the performance of the storage collector can be improved by using the partition. The mean Tank Temperature reached 37 °C in the 1st of January and 46 °C in the 21st of June without partition. The results of this study showed good agreement with the theoretical and experimental results available in the literature.
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Computer simulation of a two phase thermosyphon solar domestic hot water heating system
Energy Conversion and Management, 1999Co-Authors: Khalid A. Joudi, Aouf A. Al-tabbakhAbstract:The present work deals with a theoretical analysis by computer simulation of a two phase thermosyphon solar domestic hot water system using R-11 as a working fluid. The performance was studied by the aid of a simulation procedure for a typical day period divided into equal time intervals of 15 min. Instantaneous values of solar radiation intensity and ambient Temperature were applied at the beginning of each time step. The insolation was calculated according to the procedure suggested by ASHRAE. The variation of ambient Temperature during the day was approximated by a sine function. The variation of working fluid properties with Temperature was also taken into account. The computer program and calculation procedure were first validated by comparing the results with established results of single phase systems. Then, calculations were performed for the two phase thermosyphon system to evaluate mass flow rate, saturation pressure and Temperature in the collector and condenser, together with Tank Temperature, and collector and condenser thermal efficiencies. These calculated values were obtained for three cases, namely, the no loading case of no water withdrawal from the Tank, continuous loading and intermittent loading. The results obtained showed that, in the two phase system, the saturation pressure and Temperature increase continuously during the day and follow the Tank Temperature pattern. This makes the system pressure dependent on the Tank loading. The collector efficiency did not reveal a serious change with the loading condition. This behavior differs from that which occurs in the single phase system, where the collector efficiency increases considerably with loading. Comparison of the two phase system with a single phase system of the same collector area and Tank volume showed a significant increase in collector efficiency and Tank Temperature for the case of the two phase system.
Aklilu Tesfamichael Baheta - One of the best experts on this subject based on the ideXlab platform.
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Performance investigation on a thermal energy storage integrated solar collector system using nanofluid
International Journal of Energy Research, 2016Co-Authors: Afolabi L. Owolabi, Hussain H. Al-kayiem, Aklilu Tesfamichael BahetaAbstract:Summary The effect of Fe nanofluid on the performance enhancement on solar water heater integrated with thermal energy storage system is investigated experimentally. A 0.5% wt fraction of Fe nanoparticle was synthesized with the mixture of water/propylene-glycol base fluid. The experimental implementation utilized 40-nm-size Fe nanoparticle, 15 ° collector tilt angle, and 1.5 kg/min mass flow rate heat-transfer fluid circulation. The system efficiency reached 59.5% and 50.5% for with and without nanofluid. The water Tank Temperature was increased by 13 °C during night mode. The average water Tank Temperature at night mode was 47.5 °C, while the average ambient Temperature was 26 °C. The Fe nanofluid improved the system working duration during night mode by an average of 5 h. The techno-economic analysis results showed a yearly estimated cost savings of 28.5% using the Fe nanofluids as heat transfer fluid. The embodied energy emission rate, collector size, and weight can be reduced by 9.5% using nanofluids. Copyright © 2016 John Wiley & Sons, Ltd.
Jiann C. Yang - One of the best experts on this subject based on the ideXlab platform.
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A thermodynamic analysis of refueling of a hydrogen Tank
International Journal of Hydrogen Energy, 2009Co-Authors: Jiann C. YangAbstract:A thermodynamic analysis of refueling of a gaseous hydrogen fuel Tank is described. This study may lend itself to the applications of refueling a hydrogen storage Tank onboard a hydrogen fuel-cell vehicle. The gaseous hydrogen is treated as an ideal or a non-ideal gas. The refueling process is analyzed based on adiabatic, isothermal, or diathermal condition of the Tank. A constant feed-rate is assumed in the analysis. The thermodynamic state of the feed stream also remains constant during refueling. Ideal-gas assumption results in simple closed-form expressions for Tank Temperature, pressure, and other parameters. The non-ideal behavior of high-pressure gaseous hydrogen is addressed using the newly developed equation of state for normal hydrogen, which is based on the reduced Helmholtz free energy formulation. Sample calculations are presented using initial Tank and feed stream conditions commensurate to practical vehicular applications. Comparing to the non-ideal analysis, the ideal-gas assumption always results in under-prediction of the Tank Temperature and pressure irrespective of the filling condition. For a given target Tank pressure, the refueling time is the shortest under adiabatic condition and is the longest under isothermal condition with the Tank being maintained at the initial Tank Temperature. The adiabatic and isothermal conditions can be viewed, respectively, as the lower and upper bounds of the refueling time for a given final target Tank pressure.
Yong Wang - One of the best experts on this subject based on the ideXlab platform.
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A theoretical analysis of the daily performance of a new water Tank with multiple outlets in solar water heating system
Journal of Cleaner Production, 2020Co-Authors: Yong WangAbstract:Abstract A variable-volume Tank featured with multiple outlets is lately proposed to cater for the varying needs of Tank volume. Compared with conventional Tank, the new Tank can help shorten the thermal response time and improve the solar charging performance. In this paper, a mathematical model is developed to simulate the solar charging and discharging performances of the new Tank. The model, based on the one-dimensional multi-node approach, considers the adaptive selection of the operative outlet port. The model shows good agreement of the Tank Temperature development against the computational fluid dynamics simulation and experimental results. Using the model, a parametric study was conducted to analyse the effects of heat demand, initial Tank Temperature and solar insolation. The results show improved heat supply and reduced heat loss achieved by the new Tank. It also demonstrates that the performance of the new Tank is less affected by the heat load, initial Tank Temperature and solar insolation, which contributes to a robust heating system.
