| Winter heating of rural houses in northern China generally adopts the form of kang,and its main heat exchange methods are heat conduction heat exchange,natural convection heat exchange and radiation heat exchange outside the kang.At present,the research on the kang is mainly to improve the structure,material and thermal properties of the kang,and to evaluate the thermal environment of the entire ondol room.In fact,the main activity area of the residents of winter farmhouses in northern China is above the kang,and other areas are short-term residences,and there is a lack of in-depth research on the hot environment above the kang.Therefore,this paper studies the local thermal environment of the ondol room,which is of great significance to improve the living environment of rural residents in northern China in winter and improve the thermal comfort of the kang room.Firstly,this paper systematically summarizes the research and development of traditional kang in China,the internal structure of the kang,the thermal performance of the kang,the combination of kang and modern technology,and the thermal environment of the ondol room,and then compares and analyzes the building structure of similar kang and similar houses in the kang room abroad.Secondly,this paper makes a theoretical analysis of the heat transfer process of the air inside the ondol room,systematically sorts out the heat exchange between the farm house and the outside world and the heat exchange between the air inside the farm house and the human body,based on the heat exchange theory,under the premise of reducing carbon emissions as much as possible and reducing the economic pressure of farmers,effective improvement measures are proposed to improve the local thermal environment above the kang,by increasing the insulation baffles of different heights,adding insulated tables to try to keep the heated air in the foot position of the human body when relaxing and sitting.By changing the position of the flue at the tail of the kang to form a fire wall,the temperature of the wall is increased,the radiant heat transfer to the human body is enhanced and the air in the local area above the kang is heated.Theoretical analysis provides guidance for follow-up research.Third,in order to explore the comfort above the kang in northern farmhouses in winter,this paper investigates the indoor parameters and outdoor environmental parameters of farmhouses with kang as a single heat source in Jiaodong area,China,and conducts a questionnaire survey on the thermal feeling and thermal comfort of residents when sitting above the kang,and uses environmental parameters to calculate the PMV when sitting above the kang.The results showed that the residents were not satisfied with the thermal sensation of the farmhouses with the kang as the single heat source,and the reasons for the residents’ dissatisfaction with the thermal environment were analyzed due to the local heat feeling of cold and the imbalance of hot sensation.The value of calculated PMV is low compared to the actual thermal comfort poll results,mainly because the calculation of PMV ignores the effect of the ondol on the heat transfer of the subject.Fourth,on the basis of the measurement data,a physical model of the ondol room is established,and in order to verify the reliability of the simulation,another set of simulations is set up according to the literature data.In order to reduce the computational pressure,the model is appropriately simplified,the mesh independence verification is performed,and the optimal meshing scheme is selected.Then,the numerical simulation results of the two types of ondol rooms were verified by temperature field and velocity field,and the existing errors were analyzed to judge the reliability of the simulation.It lays a good foundation for the subsequent simulation of improving the thermal environment above the kang.Finally,the numerical simulation of the ondol room with the addition of improvement measures shows that the addition of thermal insulation baffles and insulated tables,as well as the position of the flue at the tail of the kang to form a fire wall,can effectively improve the average temperature of the local thermal environment above the kang,and significantly improve the thermal environment of the residents’ feet.In addition,in order to explore the influence of improvement measures on the thermal environment above the kang under different working conditions,this paper simulates and compares the ondol rooms under different outdoor ambient temperatures to analyze the temperature variation law.As the temperature of the outdoor dry bulb increases,the improvement effect of adding fire walls and insulation baffles gradually decreases.The outdoor dry bulb temperature had little effect on the effect of improving the average air temperature above the kang by adding an adiabatic table,and the increased temperature was always maintained at about 3.67°C... |
