Principle of burning kang

The sleeping apparatus made of earth or bricks in the north to protect against the cold while sleeping is called "kang".

Disadvantages of the "kang": waste of effective resources (wood consumed in heat production, etc.); not environmentally friendly (pollutants produced by combustion that affect both people and the environment); labor-intensive heating (manual operation); temperature control is not easy to grasp; and its application is not widespread (limited to rural areas).

Burning fire kang needs stove, fire kang is not good, most of the problems will appear in the stove.

China's traditional old-fashioned stove has one not, two high, three big, four no drawbacks:

One not: ventilation unreasonable. The old stove has no ventilation channel (ash kang), only by adding firewood ventilation, from adding firewood into the mouth of the air can not directly through the fuel layer and fuel blending uniformity, so the fuel can not be fully combusted. At the same time, a large amount of cold air coming in from the wood-adding port lowers the temperature inside the stove when passing through the fuel surface, taking away part of the heat, making some combustible gases and carbon not fully oxidized. As the saying goes, "If you don't ventilate the stove, the firewood will be trapped; if you want to burn well, you have to pick and burn".

Two high: high pots and pans, high hanging fire. The old-style stove only consider the convenience of cooking and add firewood to save energy, but did not pay attention to the burning of fuel and saving. Whether the pot with the pot is built very high, the pot umbilical cord and the distance from the ground is very large, so that the flame can not fully contact the bottom of the pot, a large amount of heat energy are lost. This stove is slow to open the pot, cooking time is long, it is "the pot is higher than the kang, smoke back to choke; hanging fire distance is high, firewood into a pile of burning".

The three big ones are: the large wood-adding port, the large stove chamber, and the large smoke-entry port (stove throat). The old stove because of this "three big" so that the stove flame is not centralized, the fire red, stove temperature is low. There is no fire ring in the stove, firewood on fire to run to the stove throat eye, the fire into a diagonal line, the flame stays in the chamber for a shorter period of time, increasing the loss of combustion heat radiation, so that a part of the heat from the stove door and smoke inlet ran away for nothing.

Four no: no grate, no door, no fire ring, no stove eye insert. The old stove because of no grate to make the stove ventilation effect is not good, the fuel can not be fully combusted, the phenomenon of burning and smothering carbon. Due to add firewood mouth no door, a lot of cold air from the door into the stove, reducing the temperature inside the stove, affecting the combustion effect, increasing the heat loss. Because there is no fire ring in the stove chamber, the flame and high temperature smoke in the stove stays for a short period of time, the flame runs to the stove throat and can't fully contact the bottom of the pot, the heating area of the bottom of the pot is small, the cooking is slow, the time is long, and the cost of fuel. As the old stove has no stove throat insert, thus causing the stove throat eye flue left small, no wind days when the pumping force is small, the smoke can not be discharged, the appearance of prairie smoke, pressure smoke and do not like to start a fire; stove throat eye flue left large, in the windy days, the kang of the pumping force is large, smoke and fire and all pumped into the kang, the appearance of the phenomenon does not like to open the pot, cooking slow. At the same time, the stove does not keep warm, the kang cools quickly, and also increases the smoke loss. So: the old stove cost wood, coal, labor, time, low thermal efficiency.

At the same time, the old-style kang has the disadvantages of one thing, two things, three obstacles, four deep:

One thing: the cold wall part of the old-style kang has no heat preservation layer. In winter, the inner wall of the cold wall part of the kang (the front wall, the back wall, and the mountain wall) is sometimes frosted, hung with ice, and there is a great loss of heat in the kang. At the same time, if the inner wall is not tightly plastered, it is not easy to burn because of air permeability. If you add a thermal insulation layer to the cold wall part, you can prevent air permeability and reduce the heat loss in the kang.

Two no's: the surface of the old-style kang is not flat, and the second is not strict. In the past, the old-style kang is "no matter what kind of kang surface is built, and finally all the mud leveling". This is wrong. If the surface of the kang is not flat, the resistance of the smoke when it touches the bottom surface of the kang surface will be big, which affects the speed of smoke distribution and smoke exhaust, and if the surface of the kang is not tight, the force of the pillar bricks in the kang will be uneven, which will result in the phenomenon of the kang surface material being broken and the collapse of the kang. The contact between the kang surface material is not good, the kang surface mud thin thickness is not uniform, and directly affect the heat transfer effect of the kang surface.

Three obstacles: the old-style kang head of the kang is blocked with bricks to share smoke, resulting in smoke in the head of the kang to concentrate and pause, so the head of the kang to share smoke resistance. Most of the holes in the kang are made of horizontal dead wall, occupying a large area, the heat area of the kang surface is small, and at the same time, some fire bricks and wind bricks are placed in the holes in the kang, resulting in a large resistance to smoke exhaustion in the kang. The top of the kang has no horizontal convergence path for smoke, but is built with bridging bricks, resulting in poor smoke exhaust and high resistance to smoke coming out of the top of the kang. This "three resistance" makes the kang not good to burn and can not be full of kang heat, increasing the temperature difference between the kang head and the kang head.

Four deep: the old-style kang's "kang hole is deep", "dog kennel is deep", "smothering stove is deep", and "ash drop chamber is deep". The "four depths" of the kang are These "four depths" allow a lot of cold air to be stored in the kang. When the stove is lit, the cold air inside the kang and the hot flue gas will form a heat exchange and produce eddy currents, causing the stove to burn badly. These cold air also need to absorb and take away a lot of heat, so that more burning fuel kang is not hot.

In short, the old-style stove kang due to the influence of these shortcomings, so often is not good to burn, the kang is not hot, the house is not warm; in order to make the kang hot house warm, you have to build more stoves, more fuel, resulting in the cost of coal, firewood, labor, time and materials.

So what is the difference between the old and new kangstoves?

Through the above analysis we have learned that the old-style stove has no ventilation channel, the stove chamber is big, the stove door is big, the throat eye is big, the firewood can not be fully combusted, the heat loss is very large, the cost of firewood, the cost of coal, and the time-consuming. The structure of the old-style kang is unreasonable: the ash-falling chamber, the stuffy stove, the "dog's nest" and the hole in the kang are all very deep, which not only wastes a lot of material when building the kang, but also stores a lot of cold air in the kang, so that the kang is cool and the house is cold. Sometimes the smoke from the kang and stove filled the room with smoke and dust, choking people to the point of tears and snot. In some stoves, the fire escapes from the mouth of the stove and the kang is overheated locally, sometimes causing fires. In short, the old-style kang stove heat utilization rate of only about 20%, both a waste of a lot of fuel, but also extend the cooking time, the kang can not be all hot, but also unsafe, unhygienic.

The new type of kang stove is designed reasonably according to the scientific principle of combustion and heat transfer: the heat balance and economic operation of the kang stove are preferred, the hearth, the relative distance between the pot wall and the stove and the height of the hanging fire, the flue and the ventilation, and the structure of the kang, etc., and additional heat preservation measures are set up for the kang stove to improve the effect of the utilization of residual heat and expand the heating surface of the kang and the surface of the heat dissipation. Therefore, the new-style kang stove has reasonable structure, good ventilation, sufficient burning of firewood and grass, fast stove fire, good heat transfer and heat preservation, and the heat utilization rate of the kang stove reaches about 50%. Therefore, the new-style kang stove saves fuel, saves time, good burning, kang hot, house warm, easy to use, safe and hygienic.

"Northern efficient prefabricated assembly overhead kang even stove" (commonly known as "hanging kang") is Liaoning Province, rural energy science and technology personnel in the "Seventh Five-Year Plan", During the period of "Eighth Five-Year Plan", it was successfully developed based on repeated research and practice in various disciplines such as building structure science, fluid mechanics, thermodynamics, meteorology, etc. The heat efficiency of the stove has changed from the past to the present. The thermal efficiency of the stove has increased from 14%-18% to 25%-35%, and the combined thermal efficiency of the kang and stove has increased from about 45% to more than 70%. Spacious kang, smoke exhaust smooth, reasonable structure, kang temperature can do according to seasonal mediation, the temperature is appropriate, not only high thermal efficiency, and beautiful appearance, type for the bed, by the majority of farmers are welcome, known as farmers at home "Simmons".