Hamdi Kessentini | Ecole Nationale d'Ingénieurs de Tunis (ENIT) (original) (raw)
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Papers by Hamdi Kessentini
The aim of this work is to develop a numerical code able to predict the thermal behavior of a dou... more The aim of this work is to develop a numerical code able to predict the thermal behavior of a double tank integrated collector storage system (ICS) with compound parabolic concentrator (CPC). The developed numerical model is based on the detailed analysis of the different forms of heat transfers occurring in the ICS system. The balance equations of each element of the system have been established and solved by means of a transient algorithm. A prototype of an ICS device was constructed and experimentally tested outdoors in order to observe the variation of water temperature in the storage tanks. The experimental results are presented and the validity of the model is examined by comparison of the theoretical results with experiments which demonstrates a good agreement. The numerical model is then used to perform theoretical study on the present ICS solar heater. The simulation results of the variation of the thermal efficiency are presented. The results of the yearly parametric study of the effect of the concentrators reflectivity, the absorber emissivity and the use of double glazing on the thermal performance of the ICS system are also presented and discussed. The developed numerical tool within this work can be considered as important for the study of double tanked ICS solar water heater regarding its transient thermal behavior.
In this work a three dimensional heat transfer analysis of honeycomb Transparent Insulation Mater... more In this work a three dimensional heat transfer analysis of honeycomb Transparent Insulation Materials (TIM) destined for improving the efficiency of flat plate solar collectors is performed. The cellular and repetitive nature of the TIM structure has allowed simplify the problem and simulate a single isolated cell with opaque and adiabatic walls. The combined heat transfer by radiation and conduction across the isolated cell is treated by means of the solution of the energy equation in its three dimensional form which is coupled to the Radiative Transfer Equation (RTE). The Finite Volume Method is used for the resolution of the RTE. The numerical results are compared to experimental measurements of the heat transfer coefficient on various honeycomb TIM given by different authors in the literature showing a reasonable agreement. The 3D simulations have allowed to study in detail the thermal behavior of the TIM and to understand the real physics of the problem. Finally, a parametric study is conducted in order to investigate the effect of the variation of the most relevant optical and dimensional parameters of the TIM on the heat transfer.
Innovative flat plate solar collector with TIM is presented. The overheating protection system co... more Innovative flat plate solar collector with TIM is presented. The overheating protection system consisting of a ventilation channel with thermally actuated door is designed. The numerical model and the experimental tests are performed. The validation with experiments shows good agreement. A parametric study is performed to optimize the system design. a b s t r a c t In this work a flat plate collector (FPC) with plastic transparent insulation materials (TIM) and a low-cost overheating protection system destined for heat supply from 80 to 120 C is presented. A ventilation channel with a thermally actuated door is inserted below the absorber allowing to protect the collector from stagnation conditions, while preserving good performance during normal operation. This collector is intended to have not only a comparable efficiency with the available commercial collectors but also low cost. For this objective, a prototype has been constructed and experimentally tested and in parallel, a numerical model has been implemented. The proposed numerical model is based on the resolution of the different components of the solar collector by means of a modular object-oriented platform. Indoor and outdoor tests have been performed in order to check the effectiveness of the designed overheating protection system and to validate the model. The comparison of the numerical results with experiments has shown a good agreement. Finally, an extended parametric study is performed in order to optimize the collector design: 3125 different configurations of FPC with TIM and ventilation channel were evaluated by means of virtual prototyping. The results allowed to propose the most promising design of a stagnation proof FPC with plastic TIM able to work at an operating temperature of 100 C with good efficiency. The design presented in this paper can be considered promising for increasing the thermal performance of FPC and could be used in industrial applications that need heat at low-to-medium temperature level.
The aim of this work is to develop a numerical code able to predict the thermal behavior of a dou... more The aim of this work is to develop a numerical code able to predict the thermal behavior of a double tank integrated collector storage system (ICS) with compound parabolic concentrator (CPC). The developed numerical model is based on the detailed analysis of the different forms of heat transfers occurring in the ICS system. The balance equations of each element of the system have been established and solved by means of a transient algorithm. A prototype of an ICS device was constructed and experimentally tested outdoors in order to observe the variation of water temperature in the storage tanks. The experimental results are presented and the validity of the model is examined by comparison of the theoretical results with experiments which demonstrates a good agreement. The numerical model is then used to perform theoretical study on the present ICS solar heater. The simulation results of the variation of the thermal efficiency are presented. The results of the yearly parametric study of the effect of the concentrators reflectivity, the absorber emissivity and the use of double glazing on the thermal performance of the ICS system are also presented and discussed. The developed numerical tool within this work can be considered as important for the study of double tanked ICS solar water heater regarding its transient thermal behavior.
In this work a three dimensional heat transfer analysis of honeycomb Transparent Insulation Mater... more In this work a three dimensional heat transfer analysis of honeycomb Transparent Insulation Materials (TIM) destined for improving the efficiency of flat plate solar collectors is performed. The cellular and repetitive nature of the TIM structure has allowed simplify the problem and simulate a single isolated cell with opaque and adiabatic walls. The combined heat transfer by radiation and conduction across the isolated cell is treated by means of the solution of the energy equation in its three dimensional form which is coupled to the Radiative Transfer Equation (RTE). The Finite Volume Method is used for the resolution of the RTE. The numerical results are compared to experimental measurements of the heat transfer coefficient on various honeycomb TIM given by different authors in the literature showing a reasonable agreement. The 3D simulations have allowed to study in detail the thermal behavior of the TIM and to understand the real physics of the problem. Finally, a parametric study is conducted in order to investigate the effect of the variation of the most relevant optical and dimensional parameters of the TIM on the heat transfer.
Innovative flat plate solar collector with TIM is presented. The overheating protection system co... more Innovative flat plate solar collector with TIM is presented. The overheating protection system consisting of a ventilation channel with thermally actuated door is designed. The numerical model and the experimental tests are performed. The validation with experiments shows good agreement. A parametric study is performed to optimize the system design. a b s t r a c t In this work a flat plate collector (FPC) with plastic transparent insulation materials (TIM) and a low-cost overheating protection system destined for heat supply from 80 to 120 C is presented. A ventilation channel with a thermally actuated door is inserted below the absorber allowing to protect the collector from stagnation conditions, while preserving good performance during normal operation. This collector is intended to have not only a comparable efficiency with the available commercial collectors but also low cost. For this objective, a prototype has been constructed and experimentally tested and in parallel, a numerical model has been implemented. The proposed numerical model is based on the resolution of the different components of the solar collector by means of a modular object-oriented platform. Indoor and outdoor tests have been performed in order to check the effectiveness of the designed overheating protection system and to validate the model. The comparison of the numerical results with experiments has shown a good agreement. Finally, an extended parametric study is performed in order to optimize the collector design: 3125 different configurations of FPC with TIM and ventilation channel were evaluated by means of virtual prototyping. The results allowed to propose the most promising design of a stagnation proof FPC with plastic TIM able to work at an operating temperature of 100 C with good efficiency. The design presented in this paper can be considered promising for increasing the thermal performance of FPC and could be used in industrial applications that need heat at low-to-medium temperature level.