Thermal performance of a novel heating bed system integrated with a stack effect tunnel

The traditional widely used Chinese Kang heating system has been gradually becoming obsolete, due to the coal or wood burning emission that causes poor indoor air quality. In the interest to preserve the rural life, this study evaluated the performance of a retrofitted traditional Kang heating system with the use of alternative clean energy in a rural-dwelling in Xi'an, China. An air source heat pump (ASHP) was applied to drive the heating bed system, and an indoor stack effect tunnel was incorporated to induce the stack effect and to enhance the heating efficiency. A series of experiments were carried out by varying the exhaust tunnel height and heating mode. The system was shown to have produced significant improvement of the indoor air temperature and satisfied the Chinese standard, GB/T 50824-2013 for rural buildings. For the same mean outdoor temperature, when the stack effect tunnel height was extended from 1.0 m to 1.5 m, a 9.3% improvement in the heat release was obtained. When the heating mode changes from a single flue bottom surface heating to the combined flue bottom and vertical tunnel's lateral surface heating, the enhancement was 43.9%. The system would provide a sustainable way to renovate, upgrade and preserve the traditional Kang system with a use of a cleaner energy source.