Chinese Kang Research Articles

Inheritance and Development of Chinese Kang in Interior Space

The Chinese kang is an ancient technology that combines an integrated household system for cooking, sleeping, and heating. Most of the existing research focuses on the energy performance of Chinese kang and its impact on the interior environment and tries to adapt it to the modern interior space through the improvement of its technology. However, if we only focus on the research and improvement of the technical level of Chinese kang, it is not conducive to the effective inheritance and development of the culture. This paper studies the concept of 'inheritance and development' of Chinese kang culture more comprehensively from the perspective of interior design. The study proves that Chinese kang is not only a survival necessity to cope with cold, but also an expression of people's emotional catharsis and psychological needs, and that the intangible values of Chinese kang culture can be integrated into tangible modern living spaces and developed in the process of modernisation. The results of the study can be used as a starting point for enriching the Chinese kang culture and interior living culture from different perspectives in the future.

Numerical simulation research on heat transfer characteristics of a Chinese kang

In order to obtain the thermal physical parameters of heat transfer in Chinese kang, the fluid-solid coupling heat transfer is analyzed through the Fluent and Static Structural modules in ANSYS. The indoor temperature field changes under different external influences are obtained, and the distribution characteristics of the severity of the thermal damage area of the kang body are basically grasped. The temperature distribution in the heated area of the Chinese kang is not uniform, and the temperature of the kang body changes more slowly than air. One hour after the heating is stopped, the temperature of the kang body can still continue to rise. The equivalent elastic strain value near the smoke heating area is higher, and the value is between 1.2752 × 10−12–1.5939 × 10−12 m/m. This area has a higher risk of thermal damage and structural deformation. The traditional Chinese kang has good thermal inertia and has a 5 h warmth retention effect after heating is stopped.

Winter vacation, indoor air pollution and respiratory health among rural college students: A case study in Gansu Province, China

Indoor air pollution (IAP) is one of the most important risk factors contributing to respiratory health. This study aims to assess the respiratory effects of IAP caused by coal stoves and Chinese kang among rural college students during the winter vacation in Gansu Province, China. Seventy rural college students took the questionnaire survey, urine collection and spirometry tests before, during and after their winter vacations. IAP levels were evaluated by IAP exposure index. Linear mixed effect model and generalized linear mixed models were used to estimate the effect of IAP exposure index presented on respiratory health. Comparing with before and after the winter vacation, we found that there were the greater incidences of respiratory symptoms (χ2 = 19.54; p < 0.05) and the higher levels of urinary 8-epi-prostaglandin F2 alpha (8-epi-PGF2α), and the FEV1/FVC ratio decreased significantly during the winter vacation(p < 0.05). Every 1 unit increase in IAP exposure index was associated with an increase of 10.11% (95%CI: 0.97%–20.08%) 8-epi-PGF2α after adjusting for other variables (p < 0.05); and the risk of respiratory symptoms increases by 42% (OR: 1.42; 95%CI: 1.09–1.84) for every 1 increase in IAP exposure index. Our results indicate that, even during a short vacation period, the IAP caused by the use of coal stoves and Chinese kang in rural areas is associated with adverse respiratory health effects among healthy young adults, highlighting the importance of mitigating pollution from Chinese kang and coal stove.

Experimental evaluation of a capillary heating bed driven by an air source heat pump and solar energy

The traditional Chinese kang is a widely used domestic heating system in rural areas in northern China. However, such system could cause serious air pollution due to burning of biomass materials or coal. An improved bed heating system is introduced in this study to reform the traditional kang, using a capillary mat as a heating terminal, an air source heat pump (ASHP) and a solar energy as the heat source. An experimental prototype was built in a residential house in Xi’an, China, and tests were conducted to evaluate the system’s feasibility and performance under different operational modes. Results showed that the system could effectively provide an acceptable thermal environment for a separately heated room and with a reduced consumption of carbon-based fuel. When the system was completely driven by the ASHP, the daily electricity consumption of the ASHP is only 5.5 kWh with a supply water temperature of 40°C. When coupling the ASHP with the solar energy, the daily hours of solar energy utilization ranged from 3.5 to 4.5 h per day when the ratio of the solar thermal collector area to the floor area was approximately 1.0. The available ratio (days of utilized solar energy to the days comprising the full heating season) exceeded 66.0% over three heating seasons. The system was shown to be a feasible and energy-efficient heating strategy for rural buildings.

Experimental and simulation study on the thermal performance of a novel flue composite wall

The traditional Chinese kang is widely used in rural areas of northern China for space heating in winter. However, recently, the development and application of the Chinese kang system begin to decline due to its low efficiency and poor thermal performance. A flue composite wall (FCW) is proposed in this paper to improve the energy efficiency by recovering the waste heat form the exhaust smoke discharged from the kang body. Moreover, the FCW works together with the kang system to improve the indoor thermal environment, as a supplementary heating facility. To investigate the performance of the FCW, experimental test and numerical simulation were employed. The experiment results showed that, at the end of the heating stage, the average temperature and the heat flux of FCW surface could reach 295.59 K and 29.8 W/m2. Based on the test results, a numerical model was validated and then used to optimize the structure design of the FCW. The simulation results showed that a better thermal performance achieved when the insulation-to-flue ratio was 2, the smoke stopper thickness was 20–50 mm and the smoke flow velocity was 1.15 m/s-1.55 m/s, respectively.

Emissions Inventory of Smoldering Chinese Kangs and Their Contribution to PM2.5 Pollution in Lanzhou City

Considering regional differences in economic development, the activity level of smoldering Chinese kangs was confirmed by surveys in typical areas in Lanzhou City. An emissions inventory of smoldering Chinese kangs in Lanzhou City in 2016 was established using the emissions factor approach. The emissions amounts of SO2, NOx, NH3, CO, volatile organic compounds (VOCs), PM10, PM2.5, organic carbon (OC) and elemental carbon (EC) were 340.8, 201.8, 106.0, 36628.2, 4997.2, 6070.3, 5645.1, 1089.3, and 1233.1 t·a-1, respectively. Emissions amounts were allocated by spatial and temporal characteristics. The emissions were concentrated from November to mid-April of the following year. Spatially, there were significant differences in emissions at different economic levels. The high value areas of emissions were mainly concentrated in the southern part of Yuzhong, central Yongdeng, and south of Qilihe. The weather research and forecasting with chemistry (WRF-Chem) model was used to determine the average contribution of smoldering Chinese kangs to PM2.5 concentration in Lanzhou City during the heating season. The simulation results were improved after applying the emissions inventory. The average PM2.5 concentration at Lanyuan Hotel (in the city) and Yuzhong Station (in the countryside) increased 32 μg·m-3 and 34 μg·m-3 in the simulation, respectively, and the corresponding rates of pollution contribution were 37.6% and 49.2%. Thus, researching and enacting scientific control measures for smoldering Chinese kang pollutants is significant to improving regional air quality.

Experimental and numerical research on the performance of an energy-saving elevated kang in rural buildings of northeast China

Traditional Chinese Kang is frequently used for space heating in rural areas of northern China, since it is easy to construct and offers various benefits for a rural building, including cooking, heating, providing a place for sleeping and so on. However, various problems, such as smoke leakage, non-uniformity of the kang surface temperature and so on, exist in a rural building heated by Chinese kang. Here, a novel kang system called energy-saving elevated kang (ESEK) is proposed based on the ordinary elevated kang (OEK) model. Experimental results showed that the comprehensive efficiency can be improved by 6.06%. Under the same operation condition, the indoor temperature of ESEK is 2.2 °C–5.3 °C higher than that of OEK, creating a more comfortable indoor thermal environment. In addition, the temperature field of the upper surface and the velocity field of flue gas of ESEK under different boundary conditions were studied in detail using the Fluent software. Simulation results indicated that the temperature of ESEK has better uniformity. Furthermore, the optimal inlet velocity of flue gas should be between 0.5 m/s and 0.7 m/s. The ESEK proposed in this paper is suitable for application in rural buildings to improve the indoor thermal environment.

Numerical and experimental study of a combined solar Chinese kang and solar air heating system based on Qinghai demonstration building

To meet the heating demand in north China and reduce the pollution of traditional Chinese kang, a novel combined heating system consists of solar kang system and solar air heating system is proposed. The solar air system is built for the residents’ daily heating demand. The solar kang system can store the solar energy collected in the daytime and provide a good sleeping environment at night.In this study, demonstration buildings are built in Huzhu, Qinghai province and one of them is chosen to test its thermal performance. Three different operation modes: only the solar air system works, only the solar kang system works and the whole combined system works are tested. A mathematic model of the room and combined system is built based on the demonstrating building. Output simulation results are compared with experiment data. The result shows the combined system can rise the indoor air temperature significantly and the simulation result can fit the experiment well. The indoor air temperature can keep about 18°C when the ambient average temperature is 5°C. Kang surface temperature can keep above 26°C during the night at the same condition. The study proves the excellent heating performance of the combined system.

A simplified model for dynamic analysis of the indoor thermal environment of rooms with a Chinese kang

This paper uses thermodynamics equilibrium theory to develop a mathematical model for dynamic thermal processes pertaining to rooms with a Chinese kang (a heatable brick bed). The model is developed through analysis of the dynamic thermal equilibrium of indoor air temperature and the temperature of interior and exterior surfaces of the building envelopes of rooms with a kang. It is developed and solved using a thermal reaction coefficient. Based on data from a field test, a simplified mathematical model of thermal processes in such a room is presented. The model only takes into account the radiation heat transfer between the exterior surface of the kang's faceplate and the other interior surfaces of the building envelope, while ignoring the reciprocal radiation heat transfer between all other interior surfaces. A simplified mathematical model pertaining to the Chinese kang is also put forward. This model does not take into account the reciprocal radiation heat transfer between the interior surfaces of the Chinese kang. By combining these two models, the hourly values pertaining to indoor air temperature and exterior temperature of the kang's faceplate can be predicted for different burning modes of the Chinese kang. MATLAB was used for calculating the target temperatures and solving the thermal reaction coefficient. The model was validated by error analysis and correlation analysis, the result of which shows that this mathematical model can accurately predict various characteristics concerning the temperatures in a room with a Chinese kang.

A glazed transpired solar wall system for improving indoor environment of rural buildings in northeast China

In rural areas of northeast China, residents often use a traditional Chinese kang for domestic heating. However, this heating method is associated with an uncomfortable thermal environment and poor indoor air quality. Therefore, this paper proposes a glazed transpired collector (GTC) based solar wall system, as a solution. Similar to air conditioning systems, the GTC is able to generate various airflow settings, which is one creative concept of the proposed system. Experimental and numerical studies were conducted to investigate the space heating and indoor air-quality improving performance of the system. The experimental results show that the average indoor temperatures can be increased from 12.12 °C to 16.17–18.19 °C, relevant to the various operating modes. The return-air mode reduces the concentrations of CO, CO2, PM2.5, and PM10 by 34.8%, 20.3%, 14.4%, and 11.6%, respectively. The reductions relevant to the mixture mode are 69.6%, 28.0%, 45.0%, and 41.6%, respectively, and those to the fresh-air mode are 73.9%, 42.7%, 56.2%, and 58.1%, respectively. By numerically simulating the distributions of indoor air temperature and the concentrations of CO, CO2, PM2.5, and PM10, the GTC-based solar wall system is able to enhance the uniformity of temperature distribution and dilute indoor pollutant concentrations. To conclude, a summary of the simple and easy operating manual of the solar wall system is presented in this paper. The solar wall system can solve the problem of unacceptable indoor thermal comfort and indoor environmental pollution in rural dwellings in cold climates.

Experimental Assessment on Heat Transfer and Smoke Flow Characteristics of a Typical Elevated Chinese Kang

Chinese kangs are widely used by 175 million people for sleeping and home heating in rural Northern China. However, there are lack of some basic and critical studies on heat transfer and smoke flow characteristics of the kangs, which definitely hinder the development of Chinese kangs. This study presents an experimental assessment on a typically elevated Chinese kang. The heat gain, heat storage, and the heat release performance of the kang body are investigated, respectively, by combining the test data and theoretical analysis. The main results show that the smoke temperature at the inlet face of the kang flue varies within 250°C–600°C as the stove works for the most times. The smoke velocity in the kang flue is about 0.1 m/s–0.4 m/s, and the flow status is determined to be turbulent. The heat exchange between the smoke and the kang plates is mainly by natural convection. The surface temperature of the upper kang plate has significant temporal variation, and its distribution at the center part is reasonably uniform. The radiative heat from the kang plates plays a big role in the total heat release, accounting for 60.6% for the upper plate and 83.3% for the lower plate.

Thermal analysis of a new solar kang system

Abstract The solar kang, which integrates the positive features of the solar air collecting system and the conventional Chinese kang, could serve as a low-polluting heating device alterative to the traditional kang, feasible for the rural households in northern China. On the basis of the dynamic heat transfer model developed in the previous work, we conducted a series of numerical parametric analysis in the light of energy storage of the kang body, energy distribution, and temperature variations of the upper kang plate. It was found that the solar kang body normally absorbed most of the airflow heat input due to large convective heat transfer area in the air space. The thermal physical parameters of the upper kang plate, including the thermal capacity and the thermal conductivity, had significant influence on the kang's heat transfer process and the according temperature variations. The results from this numerical study could be useful for the thermal design of such new local heating systems.

Structure Updates Chinese Kang Technical Countermeasures

Along with the progress of the society, the development of economy, China's heated kang facilities and people's living needs of the contradictions increasingly sharp, plus the increasingly serious energy problem, the author thinks that regional both building facilities to modern rural construction of organic renewal is the only way. Therefore, this paper puts forward structure update kang, the performance adjustment, structure, material and construction points are introduced, and the energy-saving benefit is analyzed. Hope can solve the traditional fire resistance and the new technology with the bottleneck problem.

A new Chinese solar kang and its dynamic heat transfer model

A Chinese kang, normally serving as the heated bed and the heat recovery of a cooking stove, is widespread in northern rural China and generally regarded as an energy-efficient heating system. However, major drawbacks of the system, including high levels of indoor pollution emissions and the great deal of effort required for solid fuel loading and re-loading, need to be alleviated. Thus, we developed a new kang system that integrates a low-cost, easily maintained solar air collector into the convectional Chinese kang system. Based on the thermal process, a heat transfer model is developed to simulate its dynamic characteristics. And then, by using the model validation, we found that the model could present the kang's transient behavior correctly, and therefore serve for the design proposals or check analysis in the future research, such as the thermal storage design of the kang plates, appropriate solar collecting area design, indoor thermal impact prediction, etc.

Thermal Environment of Traditional Dwelling Houses in Dry Hot and Dry Cold Climate Zone of China in Winter

In order to master the indoor thermal environment of the traditional dwelling houses in dry hot and dry cold climate zones in winter, the east Gansu province is taken for example to study. Indoor and outdoor air temperature, relative humidity, solar radiation intensity and wind speed were obtained by using field-tested methods for the traditional dwelling houses in this region in winter, and the clothing form and activity of people were surveyed by way of questionnaire. And then, the influence of house orientation, indoor heat sources and insulation on the indoor thermal environment is analyzed, the WCI (wind chill index) is used to evaluate the indoor and outdoor thermal environment at last. The results show that: the indoor temperature can raise about 8.3 °C when the house orientation is better and Chinese kang as the heating heat source. The good practice on local structure is worthy of following for other houses, such as adobe posted solid brick wall, double windows, wooden sash windows and so on. However, people still feel very cool or cold about the indoor temperature for much of the day, and even people feel very cold for 5% of the day. At the end of thesis, some methods about the indoor thermal environment improvement are proposed.

Surface Temperature Distribution of Chinese Kangs

This study is attempted to improve local thermal comfort of Chinese kang through improving the uniformity of the faceplate temperature distribution using computational fluid dynamics simulations. The faceplate temperature of kangs is determined by the heat input to the kangs, the smoke flows, and the kang body materials. The smoke flow rate and the kang body temperature are coupled. The distribution of the faceplate temperature is determined by the interior structure and smoke flow path design. In addition to a recent experimental study using infrared thermal imaging, this study uses computational fluid dynamics simulations to analyze in detail the heat transfer and smoke flow processes in a typical Chinese kang. Different design methods for improving temperature distribution of the kang faceplate are compared. Our results show that the temperature distribution on the faceplate of kang can be made to be more even using simple variations in its design.

Thermal and energy analysis of a Chinese kang

About 67 million Chinese kangs are still used by about 175 million people in China today. The kang utilizes biomass burning for space heating and hence reduces the use of commercial energy. However, the existing design of kangs is largely based on the accumulated experience of craftsmen, for lack of scientific studies and engineering design guidelines. Poor construction of kangs also leads to serious indoor air pollution. In this paper, a macroscopic smoke flow and heat transfer model of an elevated kang is integrated in a widely-used building energy analysis software in China-DeST, and the integrated software can be used for the thermal performance analysis of kang-integrated houses. A typical house with kangs in various villages of northern China is chosen as a case study. The annual performance of the kang under different insulations of building envelope and climatic conditions are discussed. Based on the simulation results, it is found that the thermal comfort requirement of the outside surface of the upper kang plate can be met by a proper construction of the kang and selection of the appropriate firing pattern. The better the insulation of the building envelope is or the better the room air tightness is, the greater the indoor air temperature rise and the greater the building heating load contribution of the kang. In the eight selected cities in northern China, the use of kang can meet 50%–80% of the house heating load.

Chinese kang as a domestic heating system in rural northern China—A review

The Chinese kang is an ancient integrated home system for cooking, sleeping, domestic heating and ventilation. It is still widely used today in nearly 85% of rural homes in northern China. In 2004, there were 67 million kangs used by 175 million people. Existing kang designs are mostly based on the intuition and accumulation of craftsman experience. There is a trend that Chinese kang is gradually replaced by bed and coal-burning radiators, domestic heating stoves, etc. using commercial energy. As rural building heating constitutes 25% of total building energy consumption in China, we consider that the transition and new technologies for rural home heating in northern China is crucial for managing future building energy consumption in China. This paper reviews the basic heat transfer and airflow principles of Chinese kang, as well as describing the traditional grounded kang and the relatively new elevated kang. The thermal performance of the kang is shown by data from literature and field surveys. The future of Chinese kang and research needs is also briefly discussed. There is also a need for scientific study in addition to experience accumulation, to form basis for engineering design.

Field survey on indoor thermal environment of rural residences with coupled Chinese kang and passive solar collecting wall heating in Northeast China

The Chinese kang is the most ancient heating system widely used in rural residences in cold regions of China, especially in Northeast China. Even though the outdoor air temperature is very low, the surface temperature of Chinese kang can still remain above 30 °C. However, a comfort indoor thermal environment cannot be achieved by a Chinese kang alone. Passive solar heating techniques can be coupled with the Chinese kang to improve the indoor thermal conditions. In this study, two field surveys had been conducted in three residences in Dalian of Northeast China to investigate the thermal environments of rural residences with a coupled Chinese elevated kang and passive solar collecting wall heating system. Indoor thermal environments were evaluated with parameters of indoor air temperature and relative humidity, surface temperature of the kang plates, air temperature of the upper/lower vents in passive solar wall and human activities, etc. The description of this survey and the methodology of data analysis are described in details in this paper. The survey results objectively provide the preliminary information regarding the indoor thermal environment of new rural energy-saving residences in winter in Northeast China.

A Note on The Roman Hypocaust, the Korean On-dol, and the Chinese Kang

The Romans developed the hypocaust in the first century BC as a suspended floor supported on columns, which was heated by hot flue gases produced by a furnace at one end and exhausted by a chimney at the other. Later the flues were channelled under the floor and eventually passed through flues in the walls to heat also the vertical surfaces. The development of the Korean on-dol and the Chinese kang was very similar, and both, unlike the hypocaust, are still used today.