Study On Heat Source Characteristics And Heat Transfer Process Of Burning Cave Heating System

Traditional heating systems such as kang, heating wall and burning cave have been used in rural areas of northern China for thousand years. These systems were closely related to human daily life. Crop wastes have been used as heat resources, and a recycling lifestyle has been formed. There are some problems such as low thermal efficiency, poor heating effect, serious indoor pollution, substandard thermal comfort environment in heating period, related to society economic development and dailylife variation. In order to solve the above problems, through measurements in rural areas, and taken cooperation with three craftsmen for many years, a number of initial datas have been collected. Finally, a study line on improving traditional heating systems based on the solutions from experience was formed including discovered more application problems, optimized, theory and experimental study and calculated methods guide the engineering.Firstly, the technical improvements on traditional heating systems, constructed by cooperation with craftsmen, have been tested and analyzed. As the same time, more than10different forms of rural traditional heating dwellings located in Shenyang, Dalian and Fuxin of Liaoning Province have been measured more than two years. The Indoor thermal and humidity environment, air quality, human radiant heat gain, exergy efficiency have been measured. Thus, the average indoor temperature in the heated room by burning cave was maintained at18℃while the average temperature outside the room was-15℃, and temperature difference between day and night was reduced to4℃. The heating environment has been improved, and sustainable heating with once filling could be carried out. However, the surface temperature of the heating floor could reach up to40℃, unreasonable heat distribution and serious heat waste must to be solved.Secondly, taking rural heating dwellings with burning cave as research objects, and researching on the heat source characteristics and heat transfer regulations of the burning cave could be the basic condition for optimizing heat transfer approach of traditional heating methods. The temperature distributions within the burning cave and heat transfer process has been measured during the smoldering combustion by the high-temperature multi-point automatic temperature sensor circuit detection system. Meanwhile, filling for one time could maintain long-term sustainable heating. But some influencing factors including ignition position, constructions, combustion status on radiant heat transfer between the smoldering layers and cover plate could be discussed. Analysis formula between radiant heat intensity from burning cave, material thermal properties and surface temperatures of the radiant floor could be derived by establish the unsteady-state heat transfer model. These results indicated that while heat intensity was not changed, as the thermal resistance of the heating floor was increased by0.5(m2-K)/W, the heat flux of the radiant heating floor could be reduced to0.67times more than original heat flux.Thirdly, based on the heat resource characteristics and heat transfer regulations, hot water heating system coupled with burning cave and radiant elevated-floor heating system integrated with burning cave have been designed and presented. The performance of the heat transfer process has been predicted by a theory analysis method, and the higher temperature on the heating floor has been solved. By analyzing the heat transfer and distribution proportion of the hot water heating system coupled with burning cave, the time response of the water temperature changed with heat intensity has been taken out. By analyzing of the radiant elevated-floor heating system integrated with burning cave, the heat transfer model of the air in it has been established, the temperature distribution and velocity distribution has been calculated for providing theoretical basis and design parameters for experimental platform establishment.Fourthly, according to the theory calculation analysis, the experimental platform of water heating system coupled with burning cave and demonstration house integrated with radiant floor heating system based on one burning cave has been constructed. On the one hand, the heat distribution of total quantity from burning cave was calculated as follows:the linearity relevant coefficient between the plate on the burning cave and hot water heating system respectively gained from the total heat was0.29. Meanwhile, by quantitative analysis, different diameter, tube spacing, flow velocities impact on the heating process heating has been discussed. On the other hand, heat transmission variation of elevated floor heating system has been carried out. The hot air buoyancy, the rate of temperature drop, methods for heat transfer enhancement, and heat change characteristics of the the elevated floor heating system influncing on the heat transfer process has been analyzed. The thermal efficiency of each system was respectively increased to39.3%,56.7%.Finally, based on the theoretical analysis and experiment study, as the same time, in considering of energy-saving design on rural dwellings, some design parameters has been identified, including the annual heat consumption under different climatic condition, the proportion between the area of burning cave and the heated room or a house. The simplified calculation method for the two heating systems design has been taken out. Furthermore, the purpose of low cost, comfortable living environment, resource recycling house could be achieved and provided the foundation for engineering design.Therefore, in the background of new countryside construction, study on the optimized heat transfer methods for traditional heating systems is significant for inheritancing and developing the living culture. Meanwhile, the theory of "Unity of heaven and man" was achieved and the circular economy chain of resources and energy saving was realized. There are more in-depth study and exploration need to be done. The wisdom of life should be excavated and the traditional cultures from thousand years ago should be inherited.