Research On Thermal Efficiency Analysis And Application Of Rural Elevated Kangs

Energy is the most basic material needs of human survival and development. Household heating plays an important role in many energy demand aspects, and there are many expressions about human existence conditions that are associated with food and warmth. Although energy use for cooking is solved effectively in rural areas, the low indoor temperature and bad thermal comfort still is the major problem in China.For a long time, the heating appliances in rural areas of China are mainly Chinese kangs and stoves. The two appliances can help rural residents against the extreme cold, but indoor thermal comfort is still poor during winter. In the present social and economic development level in western rural areas of China, farmers have inadequate capability to pay for household heating. Therefore, how to use the appropriate technology to improve the thermal comfort of bedroom without increasing fuel use and economic burden becomes the main purpose of this study. Based on real economic conditions and energy utilization in rural areas of China, to improve or innovate the traditional kangs is a major way to enhance the quality of life in rural areas and ecological environment protection, and which has an important strategic significance on sustainable energy use in rural areas of China.In this study, we selected two observation villages and built new energy-saving elevated kangs in Zhuanglang County by referencing the existing research results. Based on the daily life scenes of farmers, this study gets the continuous time series data by indoor and outdoor temperature observation in bedrooms of elevated kangs and traditional kangs. And then a mathematical model is established with matlab7.0programming that simulates energy for household heating during winter. Under certain room temperature conditions, we estimated fuel savings by using elevated kangs, or the indoor temperature range improved by elevated kangs more than traditional kangs with same amount fuel, and assessed the thermal efficiency and promote prospect of elevated kangs accordingly. The study is to provide a scientific basis to adjust rural energy policy and perfect the public service system, which will make up the insufficiency in previous research.Summary of main contents are as follows:(1) Household energy consumption investigation.In this study, we learn the current energy use of farmers from questionnaire investigation, and the number of fuel is weighted, the behavior and the way of energy use from farmers are observed. At present, the types of existing energy sources are crop straw, fire grass, firewood (wood fuel), animal dung, coal, electricity, biogas transformed from biomass and solar energy. Rural living energy use mainly includes cooking, Kang bed-stove, furnace, lighting, electrical home appliances and cleaning. From the statistical analysis of the household energy consumption, we found that many different types of energy are used especially the more commercial energy and less clean energy, but biomass energy is the dominant leader, currently. Thus, the kinds of energy use needs to be diversified. At present, heating by kangs can account for the largest proportion of the total energy consumption in two observation villages. In addition to maintain basic survival needs by cooking and heating, energy for improving the life quality by lighting, electrical home appliances and cleaning are seldom used,which indicated that total energy consumption being lower in rural areas, and energy type and structure need to be further optimized.(2) The general data statistics of temperature observations.First, when the first-hand material is obtained, the temperature data is analyzed with rationality and some mutation data is corrected. Then, the temperature data of observations is made by general characteristics of statistics from hourly and daily. The results showed that the variation coefficient and daily change of indoor temperature is smaller but the outdoors is larger, because the change of temperature is inhibited by heating.Second, outdoor temperature of observation is almost consistent with the temperature of the meteorological stations of Zhuanglang County. Last, the change rule of indoor and outdoor temperature from hourly and daily is analyzed further. We found that the temperature changes over the155day period produced a U shaped curve and the lowest temperature appeared on January. On a daily (24h) basis, the highest temperature was recorded about15:00hr, while the lowest was recorded about06:00hr. The daily change in temperature produced an inverted U shaped curve. The highest temperature of indoors appeared time is about1-2hours later than outdoors which derived from the heat transfer lagging effect by indoors. During the whole observation period, although indoor temperature is lower, indoor heating effect is good by using elevated kangs.(3) Accumulated temperature difference simulation analysis.In order to fully reflect the change characteristics of temperature data in time series, the temperature change trend in a day and the whole heating period is simulated by mathematical surface method. MATLAB7.0was used to simulate the trend surfaces of the observed temperature data, and found that the quadratic trend surface model provided the best fit. Through the estimation accumulated temperature difference, we transformed the accumulated temperature difference into fuel need. It means that if the elevated kangs used same amount fuel as traditional kangs, how did the elevated kangs improve the indoor temperature range? Or if the elevated kangs had same amount accumulated temperature difference as traditional kangs, how much fuel did the elevated kangs can save? Moreover, energy use for heating to a suitable temperature is assessed which is based on the16℃as the standard of heating energy use under the rural suitable indoor temperature, and the rural household affordability for heating energy is analyzed too. These revealed that elevated kangs had the obvious effect on increasing indoor temperature range, promoting energy conservation and emission reduction, and reducing economic spending of farmers.(4) Heat balance process simulation analysis.First of all, based on the heat dissipation of the kang and enclosure structure, a simplified analysis on heating process of the kangs’ room is made, which provide the basis for establishing and calculating heat balance equation. Second, a dynamic simulation analysis on heating process of the kangs’room is made by establishing heat balance equation and the corresponding mathematical model, which can reveal thermal efficiency of two types of kangs greatly. Thirdly, based on real life of farmers, size and material of building enclosure structure, the amount and type of fuel, MATLAB7.0was used to writing program for solving heat balance equation. Among them, the determination of reasonable building enclosure structure parameters has a great significance on solving heat balance equation. Finally, the heat balance results are simulated by operating procedures and fuel trend processing, thermal efficiency of two types of kangs is obtained.(5)Evaluating environment-economic benefit and popularizing prospect analysis.Based on improving the indoor thermal comfort, reducing farmers’ economic expenditure and influence on ecological environment, the environment-economic benefit of elevated kangs is analyzed further, which is prerequisite for popularizing elevated kangs in large-scale. Therefore, it is found that elevated kangs have remarkable environment-economic benefit and social, economic, ecological value of popularization and application by establishing environmental-economic benefit evaluation model. In addition, based on the investigation, practice experience, and the reference of the existing research results, this study put forward the technical specifications of elevated kangs which are suitable for using biomass energy for heating by northwest farmers. Finally, the popularizing measures and policy suggestions are put forward.In brief, this study built the experimental sites and made research on thermal efficiency analysis and application of elevated kangs, and put forward the technical specifications of elevated kangs that are suitable for the northwest region, which can provide theoretical and practical basis for improving the rural residents’ life quality, making ecological environment better, reducing greenhouse-gas emissions and innovating energy use technology. So it has a great significance on rural sustainable development and new rural construction in China.