The overall heat efficiency of the traditional Kang-Lianzo is only about 40%, so people always use more fuel to maintain the room at a comfortable temperature and so waste fuel.
Some problems of the traditional Kang-Lianzao:
- Temperature unwell distributed - the high temperature smoke from the stove is detained in the front part of the Kang because of the dividing walls and the soot/ ash deposits. The surface temperature of Kang at the stove end is higher than at the other end. The temperature can reach 90°C in the hottest areas and even destroy the bedding.
- Waste heat - because the smoke moves in narrow, straight channels, the rate of smoke flow is too quick and it does not have enough time to transfer heat to the Kang. The smoke in chimney still remains high temperature.
- Low heat capacity of Kang body - this results in waste heat and too high temperatures.
Since 1985 the local governments have responded to the national conservation and rural energy construction policy to implement a new technique line for both heating and cooking. To promote heat efficiency, industrialized production and commercial distribution were supported by new Kang-Lianzao social popularization.
It can increase the room temperature by 4-5°C. The heat comes from smoke flow of the stove and depends on the exchange time and the heat transfer area. The heat transfer time depends on the velocity of smoke flow. When normal burning starts, the smoke flow velocity reaches 3m/sec in the channel. The high temperature smoke flows into the kang, spreads out and its velocity drops quickly to about 0.1 m/sec after 1-1.5 metres in the bed. Due to turbulence the smoke fills the spaces and has time to transfer its heat.