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ABSTRACT
This work discusses the utilization of multi tube tank heat exchanger for waste heat recovery. The thermal behavior of the system is studied in order to understand the contribution of the different heat transfer modes governing the system. As application, heating water in residential application from chimney heat recovery is considered. A prototype illustrating the suggested system is implemented and tested. Different waste heat scenarios by varying the quantity of burned firewood (heat input) are experimented. The temperature at different parts of the system and the gas flow rates of the exhaust pipes are measured. Measurements showed that the temperature of 95 L tank of water can be increased by 68°C within one hour. Obtained results show that the convection and radiation exchanges at the bottom surface of the tank have a considerable impact on the total heat transfer rate of the water (as high as 70%). Moreover, the proposed system allows saving 9.8 L of gasoline, 10.6 L of diesel or 15 kg of wood for 12 hours of chimney operation.
Acknowledgement
A short account of this work is published in Case Studies in Thermal Engineering.
| Nomenclature | ||
| h | = | Convective heat transfer coefficient, W.m−2.K−1 |
| L | = | Pipe length, m |
| Q | = | Volume flow rate, m3s−1 |
| t | = | Time, s |
| V | = | Volume, m3 |
| E | = | Energy, J |
| C | = | Specific heat, J.kg−1.K−1 |
| T | = | Temperature, °C |
| Di | = | Pipe inner diameter, m |
| D | = | Diameter, m |
| Nu | = | Nusselt number |
| n | = | Number of pipes |
| U | = | Overall heat transfer coefficient, W.m−2.K−1 |
| AL | = | Lateral surface of the pipe, m2 |
| Re | = | Reynolds Number |
| f | = | Friction coefficient |
| g | = | Gravity acceleration, m.s−2 |
| hf | = | Head losses, m |
| Pr | = | Prandtl Number |
| Greek symbols | ||
| = | Mass flow rate, kg.s−1 | |
| ρ | = | Density, kg.m−3 |
| = | Rate of Energy, W | |
| Δ | = | Difference |
| μ | = | Dynamic viscosity, kg.m−1.s−1 |
| Subscripts | ||
| w | = | Water |
| rad | = | Radiation |
| conv | = | Convection |
| t | = | Tank |
| in | = | Inner |
| out | = | Outer |
| g | = | Gas |
| i | = | Initial |
| max | = | Maximum |
| l | = | lost |
Additional information
Notes on contributors
Mahmoud Khaled
Mahmoud Khaled is assistant professor of Fluid Mechanics and Heat Transfer at the school of Engineering of the Lebanese International University. In 2009, he obtained his Ph.D. degree from the University of Nantes (France). His thesis work concerned the experimental and analytical analyzes of vehicle underhood aerothermal management. Since 2010, he is a member of Fluid Mechanics, Heat and Thermodynamics research group at the Lebanese International University. His current research activities focus on the underhood aerothermal phenomena, external vehicle aerodynamics, heat exchangers modeling and laminar flows.
Mohamad Ramadan
Mohamad Ramadan is assistant professor at the school of Engineering of the Lebanese International University. In 2010, he obtained his Ph.D. degree from the Ecole des Mines de Paris (France). His thesis work concerned the development of a new numerical method “Multi-Mesh Method” to speed-up numerical calculation, in the software Forge3. Between 2011 and 2013 he did a post-doc at the “Ecole Centrale de Nantes” on fluid structure interaction (France). Since 2013, he is a member of Fluid Mechanics, Heat and Thermodynamics research group at the Lebanese International University. His current research activities focus on Numerical method, Energy recovery and Renewable energy.