The Experts below are selected from a list of 20565 Experts worldwide ranked by ideXlab platform
Gunter Rockendorf - One of the best experts on this subject based on the ideXlab platform.
-
simulation and evaluation of solar thermal combi systems with direct integration of solar heat into the space heating loop
Energy Procedia, 2016Co-Authors: Jens Glembin, Thomas Haselhorst, Jan Steinweg, Gunter RockendorfAbstract:Abstract Usually, solar heat in combi systems is used via a Buffer Storage. In contrast to that, the solar collectors may be connected directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within system simulations for different layouts and heating elements. The simulations show significant reductions in the final energy demand as well as an increasing solar yield due to less thermal losses of the Storage tank compared to the usual solution with one Buffer Storage. A prototype of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar yield, particularly at low radiation levels. Since only a few manufacturers provide such system solutions with a direct solar integration, the results may have an important impact on the future development of combi systems.
-
direct integration of solar heat into the space heating circuit
Solar Energy, 2016Co-Authors: Jens Glembin, Thomas Haselhorst, Jan Steinweg, Sebastian Foste, Gunter RockendorfAbstract:Abstract Solar heat in solar thermal combisystems is usually used via a Buffer Storage. Alternatively, the solar collectors may be connected directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within system simulations for different layouts and heating elements. The operation of these systems requires a control strategy, which distributes the solar heat optimally between the potential heat sinks leading to the lowest overall energy consumption. This way a solar fraction may be achieved which is comparable to usual combisystems equipped with a three times larger Buffer Storage. A prototype of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar yield, particularly at low radiation levels. The direct solar heating increases the solar fraction of combisystems significantly or alternatively decreases the necessary Storage volume considerably if a certain system performance is desired.
-
simulation and evaluation of different boiler implementations and configurations in solar thermal combi systems
Energy Procedia, 2012Co-Authors: Jens Glembin, Gunter Rockendorf, Mario Adam, Jorn Deidert, Kati Jagnow, Hans Peter WirthAbstract:Abstract This simulation study investigates both different boiler specifications and various kinds of boiler integration in solar thermal combi systems with the help of a new developed fossil fuel boiler model. For each variant, the simulation outcomes to be discussed are the annual boiler efficiency, the cycling rate and, as the main indicator, the primary energy savings of the complete system. The results indicate that the effects of a solar thermal system on the annual boiler efficiency are small. Besides the system layout the annual amounts of hot water and space heating demand and their temperature levels affect the impact of the solar thermal system. Each additional Storage tank, which is heated by conventional energy, should be analyzed critically due to their additional heat losses, which reduce the system efficiency. The latter is particularly true for a boiler Buffer Storage. This study points out that the savings of primary and final energy are the most important indicators for the assessment of solar thermal combi systems. Subsystem indicators like the annual values of collector yield and boiler efficiency give additional information, but they are not sufficient for a full evaluation of a complete system.
Jens Glembin - One of the best experts on this subject based on the ideXlab platform.
-
simulation and evaluation of solar thermal combi systems with direct integration of solar heat into the space heating loop
Energy Procedia, 2016Co-Authors: Jens Glembin, Thomas Haselhorst, Jan Steinweg, Gunter RockendorfAbstract:Abstract Usually, solar heat in combi systems is used via a Buffer Storage. In contrast to that, the solar collectors may be connected directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within system simulations for different layouts and heating elements. The simulations show significant reductions in the final energy demand as well as an increasing solar yield due to less thermal losses of the Storage tank compared to the usual solution with one Buffer Storage. A prototype of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar yield, particularly at low radiation levels. Since only a few manufacturers provide such system solutions with a direct solar integration, the results may have an important impact on the future development of combi systems.
-
direct integration of solar heat into the space heating circuit
Solar Energy, 2016Co-Authors: Jens Glembin, Thomas Haselhorst, Jan Steinweg, Sebastian Foste, Gunter RockendorfAbstract:Abstract Solar heat in solar thermal combisystems is usually used via a Buffer Storage. Alternatively, the solar collectors may be connected directly to the space heating circuit in order to store the heat in the building itself. Such a direct solar integration is investigated within system simulations for different layouts and heating elements. The operation of these systems requires a control strategy, which distributes the solar heat optimally between the potential heat sinks leading to the lowest overall energy consumption. This way a solar fraction may be achieved which is comparable to usual combisystems equipped with a three times larger Buffer Storage. A prototype of one of the investigated heating concepts within a single family house proofs the functionality of the system concept and the high solar yield, particularly at low radiation levels. The direct solar heating increases the solar fraction of combisystems significantly or alternatively decreases the necessary Storage volume considerably if a certain system performance is desired.
-
simulation and evaluation of different boiler implementations and configurations in solar thermal combi systems
Energy Procedia, 2012Co-Authors: Jens Glembin, Gunter Rockendorf, Mario Adam, Jorn Deidert, Kati Jagnow, Hans Peter WirthAbstract:Abstract This simulation study investigates both different boiler specifications and various kinds of boiler integration in solar thermal combi systems with the help of a new developed fossil fuel boiler model. For each variant, the simulation outcomes to be discussed are the annual boiler efficiency, the cycling rate and, as the main indicator, the primary energy savings of the complete system. The results indicate that the effects of a solar thermal system on the annual boiler efficiency are small. Besides the system layout the annual amounts of hot water and space heating demand and their temperature levels affect the impact of the solar thermal system. Each additional Storage tank, which is heated by conventional energy, should be analyzed critically due to their additional heat losses, which reduce the system efficiency. The latter is particularly true for a boiler Buffer Storage. This study points out that the savings of primary and final energy are the most important indicators for the assessment of solar thermal combi systems. Subsystem indicators like the annual values of collector yield and boiler efficiency give additional information, but they are not sufficient for a full evaluation of a complete system.
Mahmood Farzanehgord - One of the best experts on this subject based on the ideXlab platform.
-
mathematical modeling of fast filling process at cng refueling stations considering connecting pipes
Journal of Natural Gas Science and Engineering, 2015Co-Authors: Javad Khadem, Morteza Saadattarghi, Mahmood FarzanehgordAbstract:Abstract One of the most important parameter in design of a compressed natural gas refueling station is detailed modeling of fast filling process. In this work, a new mathematical model was developed to analyze the fast filling process at compressed natural gas refueling stations. This new model is unique because connecting pipes between reservoir tanks and on-board vehicle cylinder also were taken into account. To model the process, the equation of state, continuity, momentum and energy equations have been solved for different parts of the system. The results have been validated against the experimental data to investigate effects of connecting pipes. The mass flow rate numerical values are in good agreement with the experimental values. The study carried out for both cascade and Buffer Storage systems. Variations of pressure and Mach number at different parts of the system, effects of the initial reservoir tank temperature on natural gas vehicle in-cylinder pressure and temperature are presented. The results show that pressure loss through pipes is very important and should be considered. Mass flow rate between reservoir tank and on-board cylinder is nearly constant (as the flow is chocked) during filling. Temperature growth rate at the beginning of the process is higher for the Buffer system. It is also found that there is a temperature rise around 85 K for ideal gas model.
-
effects of Storage types and conditions on compressed hydrogen fuelling stations performance
International Journal of Hydrogen Energy, 2012Co-Authors: Mahmood Farzanehgord, Mahdi Deymidashtebayaz, Hamid Reza Rahbari, Hamid NiazmandAbstract:In hydrogen fuelling stations hydrogen is usually stored in the high-pressure Buffer or cascade Storage systems. Buffer Storage system includes a single pressure reservoir, while the cascade Storage system is usually divided into three reservoirs at low, medium and high-pressure levels. In the present study, first and second laws of thermodynamics have been employed to analyze the filling process associated with these two Storage systems. The important parameters such as filling time, filled mass and compressor input work have been examined in detail. Assuming the same final vehicle on-board in-cylinder pressure for both Storage systems, the results reveal that filling time of the Buffer Storage system is much less than the cascade Storage system. However, the filled mass related to the Buffer system for the same conditions is approximately equal of the cascade system. Furthermore, the Buffer system is accompanied with much higher entropy generation as compared to the cascade Storage system, which directly reflects in the amount of required compressor input work. Entropy generation minimization has also been employed to determine the optimized low and medium-pressure reservoir pressures for the cascade Storage system, which corresponds to the lowest required compressor input work for a specific high-pressure reservoir in the cascade systems.
-
studying effects of Storage types on performance of cng filling stations
Journal of Natural Gas Science and Engineering, 2011Co-Authors: Mahmood Farzanehgord, Mahdi Deymidashtebayaz, Hamid Reza RahbariAbstract:Abstract At CNG filling station, compressed natural gas must be stored in Storage system in order to make the utilization of the station more efficient. There are two systems for storing natural gas namely Buffer and cascade Storage systems. In Buffer Storage, CNG is stored at single high-pressure reservoirs. The cascade Storage system is usually divided into three reservoirs, generally termed low, medium and high-pressure reservoirs. In current study, based on first and second laws of thermodynamics, conversation of mass and real gas assumptions, a theoretical analysis has been developed to study effects of reservation type on performance of CNG filling stations and filling process. Considering the same final natural gas vehicle cylinder (NGV) on-board in-cylinder pressure for both Storage systems, the results show that each Storage type has advantages over the other. The best configuration should be selected by balancing these advantages.
Hans Peter Wirth - One of the best experts on this subject based on the ideXlab platform.
-
simulation and evaluation of different boiler implementations and configurations in solar thermal combi systems
Energy Procedia, 2012Co-Authors: Jens Glembin, Gunter Rockendorf, Mario Adam, Jorn Deidert, Kati Jagnow, Hans Peter WirthAbstract:Abstract This simulation study investigates both different boiler specifications and various kinds of boiler integration in solar thermal combi systems with the help of a new developed fossil fuel boiler model. For each variant, the simulation outcomes to be discussed are the annual boiler efficiency, the cycling rate and, as the main indicator, the primary energy savings of the complete system. The results indicate that the effects of a solar thermal system on the annual boiler efficiency are small. Besides the system layout the annual amounts of hot water and space heating demand and their temperature levels affect the impact of the solar thermal system. Each additional Storage tank, which is heated by conventional energy, should be analyzed critically due to their additional heat losses, which reduce the system efficiency. The latter is particularly true for a boiler Buffer Storage. This study points out that the savings of primary and final energy are the most important indicators for the assessment of solar thermal combi systems. Subsystem indicators like the annual values of collector yield and boiler efficiency give additional information, but they are not sufficient for a full evaluation of a complete system.
Hamid Reza Rahbari - One of the best experts on this subject based on the ideXlab platform.
-
effects of Storage types and conditions on compressed hydrogen fuelling stations performance
International Journal of Hydrogen Energy, 2012Co-Authors: Mahmood Farzanehgord, Mahdi Deymidashtebayaz, Hamid Reza Rahbari, Hamid NiazmandAbstract:In hydrogen fuelling stations hydrogen is usually stored in the high-pressure Buffer or cascade Storage systems. Buffer Storage system includes a single pressure reservoir, while the cascade Storage system is usually divided into three reservoirs at low, medium and high-pressure levels. In the present study, first and second laws of thermodynamics have been employed to analyze the filling process associated with these two Storage systems. The important parameters such as filling time, filled mass and compressor input work have been examined in detail. Assuming the same final vehicle on-board in-cylinder pressure for both Storage systems, the results reveal that filling time of the Buffer Storage system is much less than the cascade Storage system. However, the filled mass related to the Buffer system for the same conditions is approximately equal of the cascade system. Furthermore, the Buffer system is accompanied with much higher entropy generation as compared to the cascade Storage system, which directly reflects in the amount of required compressor input work. Entropy generation minimization has also been employed to determine the optimized low and medium-pressure reservoir pressures for the cascade Storage system, which corresponds to the lowest required compressor input work for a specific high-pressure reservoir in the cascade systems.
-
studying effects of Storage types on performance of cng filling stations
Journal of Natural Gas Science and Engineering, 2011Co-Authors: Mahmood Farzanehgord, Mahdi Deymidashtebayaz, Hamid Reza RahbariAbstract:Abstract At CNG filling station, compressed natural gas must be stored in Storage system in order to make the utilization of the station more efficient. There are two systems for storing natural gas namely Buffer and cascade Storage systems. In Buffer Storage, CNG is stored at single high-pressure reservoirs. The cascade Storage system is usually divided into three reservoirs, generally termed low, medium and high-pressure reservoirs. In current study, based on first and second laws of thermodynamics, conversation of mass and real gas assumptions, a theoretical analysis has been developed to study effects of reservation type on performance of CNG filling stations and filling process. Considering the same final natural gas vehicle cylinder (NGV) on-board in-cylinder pressure for both Storage systems, the results show that each Storage type has advantages over the other. The best configuration should be selected by balancing these advantages.
