Experimental Study for the Energy Efficiency of Hot-Wall Kang

Chinese Kang with two thousand years’ history is a typical heating method using biomass in cold rural areas. It contributes to reducing the demands of coal and to optimizing the energy consumption structure, but its development is limited for low energy efficiency, poor indoor environment and etc. Therefore, we had a study based on experiment on a new reformed hot-wall Kang. The experimental results show that: the hot-wall Kang improved indoor thermal environment to a great extent. The radiation was the main way of heat elimination through the Kang’s surface, and took up about 65% of the total heat supply. The total heat carried by gas was gained by Kang body and chimney, 64.6% and 9.1% respectivley, and the remaining 26.3% was lost by discharged gas. Under the operation simulating residents’ living habit, the heating efficiency of Kang was up to 80.5% in the period of one testing day. The heat loss transferred to the ground through Kang cave and Hot-wall combustion space was 3.17% and 8.27% respectely. It also showed that the dust-ash layer filled in the cave weakened the ground heat loss and had same effect as that of insulation. Other discoveries: the mass flow rate of flue gas during the burning periods varied in the range of 0.04∼0.08 kg/s. It was turbulent flow at a low velocity, companied with two gas temperature layers. Based on the experiment, the thermal and operation character of hot-wall Kang were made clear. Furthermore, a guide for further optimization of the structure was put forward. And the results also supplied some proofs for the study of gas flow and heat transfer with natural ventilation.