Heating Water Using the Recovered Waste Heat from Boilers in HVAC Applications-Thermal Modeling and Parametric Analysis PDF

The current tendency in the energy sector is to reduce fossil fuel-based energy investments in favor of an energy approach focusing on renewable energy concepts. On the other hand, Heating, Ventilating and Air Conditioning HVAC has changed from being luxury to essential need for people and comprises many energy components that require to be well managed. The present work concerns a coupling between these two energy domains and particularly aims to apply heat recovery concepts to HVAC applications. It particularly uses the energy waste from the exhaust gases of boilers to heat/preheat water. The heat exchanger considered is concentric tube heat exchanger. A thermal modeling of the heat recovery system applied to boilers as well as a corresponding iterative code are developed and presented. Calculations with the code are performed and give magnitude orders of energy saving and management in HVAC applications. A parametric analysis based on several geometrical configurations and boiler heating loads is carried out. It was shown that water can be heated from 20 °C (68 F) to up to 100 °C (212 F) depending on the mass flow rate. The most efficient configuration is for water flowing in the inner tube with an inner to outer diameter ratio of 0.75.