Disadvantages of "fire kang": waste of effective resources (wood consumed in the process of heat production, etc. ); Not environmentally friendly (pollutants that affect people and the environment when burning); Heating is labor-intensive (manual operation); Temperature control is not easy to grasp; The scope of application is not wide (only in rural areas).
When burning kang, you need a stove. Kang is not easy to burn, and most problems will appear on the stove.
The traditional old-fashioned cooking stoves in China have the disadvantages of nothing, two highs, three highs and four lows.
No: the ventilation is unreasonable. The old stove has no ventilation duct (ash-falling kang), and it is ventilated only by adding firewood. The air entering from the wood entrance cannot be directly mixed with the fuel through the fuel layer, so the fuel cannot be fully burned. At the same time, a large amount of cold air coming in from the firewood inlet lowers the temperature in the furnace when passing through the fuel surface, taking away some heat, so that some combustible gases and carbon can not be fully oxidized. As the saying goes: "if there is no ventilation under the stove, firewood will be caught;" If you want to burn well, you have to choose to burn. "
Two heights: the pot is high and the fire is high. The old stove only considers the convenience of cooking and the labor-saving of adding firewood, and does not pay attention to the burning and saving of fuel. No matter how high the pot is, the distance between the navel and the ground is so great that the flame can't fully contact the bottom of the pot and a lot of heat energy is lost. This kind of stove boils slowly and takes a long time to cook. Just because "the pot is higher than the kang, the smoke choked back;" The distance between fire and fire is high, and the firewood burns. "
Three big: big wood mouth, big stove chamber and big smoke inlet (stove throat eye). Because of the "big three", the flame in the old stove is not concentrated, the flame is red, and the temperature of the stove chamber is low. There is no firestop ring in the furnace. When the wood is on fire, it rushes to the throat of the furnace, and the flame forms a diagonal line. The flame stays in the furnace chamber for a short time, which increases the radiation loss of combustion heat energy and makes some heat escape from the furnace door and the smoke inlet in vain.
Four noes: no grate, no oven door, no fire ring, no fire hole insert plate. Because the old stove has no grate, the ventilation effect in the stove is not good, the fuel can not be fully burned, and endless combustion and carbon suffocation occur. Because there is no oven door at the wood inlet, a large amount of cold air enters the furnace from the oven door, which reduces the temperature in the furnace, affects the combustion effect and increases the heat loss. Because there is no firestop ring in the furnace cavity, the flame and high-temperature flue gas in the furnace stay in the furnace for a short time, and the flame can not fully contact the bottom of the pot when it runs to the throat, so the heating area of the bottom of the pot is small, cooking is slow, time is long, and fuel is consumed. Because there is no insert plate in the old stove throat, the flue of the stove throat is left very small, and when there is no wind, the smoke can't be discharged, so there is no smoke, no smoke suppression and no fire. The flue of the furnace throat is very large. On windy days, the smoke in the kang is heavy, and fireworks are drawn into the kang, which leads to the phenomenon of not liking to boil and cooking slowly. At the same time, the furnace is not insulated, and the kang cools quickly, which also increases the smoke loss. Therefore, the old stove consumes wood, coal, labor and time, and its thermal efficiency is low.
At the same time, Lao Kang still has the disadvantages of nothing, nothing, three obstacles and four deep obstacles:
Nothing: the cold wall of the old kang has no insulation layer. In winter, the inner skin of the cold wall (front wall, back wall and gable wall) in the kang is sometimes frosted and frozen, and the heat loss in the kang is great. At the same time, if the interior wall is plastered improperly, it will be ventilated and not easy to burn. If the insulation layer is added to the cold wall, ventilation can be prevented and heat loss in the kang can be reduced.
Second, there is no: the surface of the old kang is uneven and loose. In the past, it was said that no matter how the kang surface was built, it was finally smoothed with mud. This practice is wrong. When the kang surface is uneven, the flow resistance of flue gas in contact with the bottom of the kang surface will be great, which will affect the distribution of flue gas and the speed of smoke exhaust. If the kang surface is not tight, the column bricks in the kang will be unevenly stressed, causing the material on the kang surface to break and collapse. The poor contact of materials on the kang surface and the uneven thickness of soil on the kang surface directly affect the heat transfer effect of the kang surface.
Three resistances: the old kang blocks the smoke emission with bricks, which leads to the concentration of smoke and stops on the kang, so the resistance of the kang is great when it emits smoke. Kang caves are mostly built by horizontal dead wall method, which covers a large area, so the heating area of kang surface is small. At the same time, some fire-facing bricks and windward bricks are placed in the kang hole, which causes great resistance to smoke exhaust in the kang. Because there is no transverse smoke confluence at the top of the kang, the kang surface is a bridge brick, which causes poor smoke exhaust and large smoke resistance at the top of the kang. This "three resistance" makes the kang not easy to burn, and the heat is not full, which increases the temperature difference between the kang head and the kang tip.
Four depths: kang cave depth, doghouse depth, stuffy furnace depth, and old-style kang ash room depth. This "four depths" make the kang store a lot of cold air. When the stove is ignited, the cold air and hot smoke in the kang will form heat exchange, resulting in eddy current, which makes the stove difficult to burn. These cold air also absorbs and takes away a lot of heat, making it burn more fuel without heat.
In short, because of these shortcomings, the old stove kang is often not easy to burn, the kang is not hot and the house is not warm; In order to keep the kang heating room warm, it is necessary to build more stoves and burn more fuel, which will consume coal, wood, labor, time and materials.
So, what's the difference between the old and new kang stoves?
From the above analysis, we know that the old stove has no ventilation pipe, and the stove has a big chamber, a big door and a big throat. Firewood can't be fully burned, which leads to great heat loss and wastes firewood, coal and time. The structure of the old kang is unreasonable: the ash room, stuffy stove, "kennel" and kang cave are all deep, which not only wastes a lot of materials when building the kang, but also stores a lot of cold air in the kang, making it cold and cold. Sometimes the smoke from the kang stove makes the room full of smoke and dust, which makes people cry. In some stoves, flames come out from the outside of the stove mouth, and the kang is overheated locally, sometimes causing fires. In a word, the heat utilization rate of the old kang stove is only about 20%, which not only wastes a lot of fuel, but also prolongs the cooking time. The kang is not fully heated, which is unsafe and unsanitary.
According to the scientific principles of combustion and heat transfer, the new kang furnace was designed reasonably: the heat balance and economic operation of the kang furnace were optimized, the relative distance between the stove, the boiler wall and the stove chamber, the hanging height, the flue and ventilation, and the structure inside the kang furnace were reformed, the heat preservation measures of the kang furnace were added, the waste heat utilization effect was improved, and the heating surface and heat dissipation surface of the kang were expanded. Therefore, the new kang stove has reasonable structure, good ventilation, full combustion of firewood and grass, fast ignition of the stove body, good heat transfer and insulation performance, and the heat energy utilization rate of the kang stove reaches about 50%. Therefore, Xinkang furnace is fuel-efficient, time-saving, easy to burn, warm in the room, convenient to use, safe and hygienic.
"Northern high-efficiency prefabricated overhead kang stove" (commonly known as "hanging kang") was successfully developed by rural energy science and technology personnel in Liaoning Province during the "Seventh Five-Year Plan" and "Eighth Five-Year Plan" on the basis of repeated research and continuous practice in building structure, fluid mechanics, thermodynamics, meteorology and other disciplines. The thermal efficiency of the cooker is increased from 14%- 18% to 25%-35%, and the comprehensive thermal efficiency of the kang stove is increased from about 45% to over 70%. The kang is spacious, smooth in smoke exhaust, reasonable in structure, adjustable in temperature according to seasonal needs, suitable in temperature, not only high in thermal efficiency, but also beautiful in appearance. It is deeply loved by farmers and is called "Simmons" in farmers' homes.