中深层同轴套管式地埋管换热器取热特性

中深层地热资源丰富,具有清洁环保、稳定可靠等特点,利用中深层地热向地面建筑物供热越来越受到人们重视.文中在考虑岩土层分层的前提下,建立中深层套管式地埋管换热器传热模型,基于有限差分法将其离散求解,并将求解的结果与某实际项目的实测数据进行比对,在此基础上对中深层套管式地埋管换热器的传热特性做了进一步模拟研究.研究结果表明:特定工况下,在系统连续运行整个采暖季后对钻井周围岩土层温度场的影响半径为7.7 m;系统取热量随着套管式换热器外径的增大而增加;当工质循环流量由35 m^(3)/h增加到42 m^(3)/h,管道底部温度仅变化2.2%;延米换热功率不宜大于150 W;当回填材料导热系数由2 W/(m·K)增加到2.5 W/(m·K)时,管底温度上升比例仅为1.9%,即回填材料导热系数达到一定值时再增大导热系数对进出水温度影响不大.

Zoning strategy of zonal modeling for thermally stratified large spaces

Large space buildings play a significant role in modern society because of their environmental advantages and market value.While the zonal model is promising for the efficient and rapid evaluation of the stratified thermal environment,there is a lack of a reasonable and convenient zoning strategy with the advent of modern computing.This paper presents a universal and practical zonal model,in which a simplified momentum equation is applied to consider air momentum preservation,transformation,and dissipation.Hence,the zoning structure is generalized and flexible.Moreover,limiting the dimensionless temperature constraint between adjacent zones establishes the connection between thermal nonuniformity and zoning results automatically.Simultaneously,the dimension and number of zones should be restricted within reasonable ranges to satisfy the characteristics of zonal simulation and reach the criteria of convergence.To further explore and validate the zonal model,a reduced-scale experimental model was constructed to replicate the thermal stratification in a mechanically ventilated large space by considering many crucial realistic factors.A particle image velocimetry(PIV)measurement was then conducted to visualize the airflow pattern and support the partition of zones.The results showed that the zonal simulation with adaptive zoning method can realize a similar accuracy with fewer zones and exhibit a better tolerance for zoning results compared to the conventional empirical zoning method.Furthermore,a case study of an atrium was performed to demonstrate the practicality and efficiency of the method for long-term dynamic simulations of complex thermal environments and building energy use.

Impact of residential building heating on natural gas consumption in the south of China:Taking Wuhan city as example

With the development of social economy,heating in the south of China has been concerned widely.As one of the energy sources of decentralized heating,natural gas(NG)has been used more and more popularly.This paper aimed to study the impact of residential building heating on NG consumption,and took Wuhan city,the representative city needing heating in winter of the south of China due to its location and climate,as an example.Firstly,a typical residential building model was established through DeST software.The heating load was simulated,and the corresponding NG consumption index was calculated.Secondly,appropriate methods were used to forecast the basic data of Wuhan city in 2020,including households and per capita gross national product(GDP),etc.Thirdly,the NG consumption of residential buildings with and without heating were predicted.Finally,the impact of residential building heating on NG consumption was analyzed.The results showed that the average annual household heating consumption of residential building in Wuhan city in 2020 was 2100 kWh/household,and the NG consumption using for residential building heating was 295 Nm 3/household.In addition,the NG consumption of residential building generated by space heating with 100%heating rate was 2.82 times the NG consumption generated by the stove and water heater,showing that residential building heating had a large impact on NG consumption.This study can contribute to choosing appropriate heating method in the southern cities of China,and further planning the gas pipe network in these cities.

Technical pathways of dual carbon control in China’s buildings sector

Reducing carbon emissions in the buildings sector is of great significance to the realization of China’s carbon peak and neutrality goals.By analyzing factors influencing buildings carbon emissions at the operational stage,this paper applies the China Building Carbon Emission Model(CBCEM)to make medium and long-term forecasts of China’s building operation carbon emissions,discussing the goals and realization paths of China’s dual carbon goals in the buildings sector.The results show that building operation carbon emissions,according to the current development model in the buildings sector,will peak in 2038-2040 with a peak carbon emission of about 3.15 billion tons of CO_(2);however,by 2060,carbon emissions will still be 2.72 billion tons of CO_(2),falling short of China’s dual carbon goals.The carbon saving effects of three scenarios,namely clean grid priority,building photovoltaic priority and energy efficiency enhancement priority,were measured and shown to be significant in all three scenarios,but the building photovoltaic priority and energy efficiency enhancement priority scenarios were superior in comparison.

Indoor environment of nearly zero energy residential buildings with conventional air conditioning in hot-summer and cold-winter zone

According to the few researches on Nearly zero energy residential buildings(NZERB)in hot-summer and cold-winter zone,although it could reduce the cooling load of buildings due to its high thermal insulation and air tightness,it still needed for certain cooling in summer.This paper studied indoor environment of NZERB un-der three kinds of air-conditioners(split-type air-conditioner,multi-line air-conditioner and ceiling radiant air-conditioner).Firstly,a simulation model of NZERB was established based on Nanjing,a typical city in hot-summer and cold-winter zone.Secondly,variation of indoor air temperature and building load characteristics with outdoor air temperature were studied.Thirdly,indoor environment and energy consumption under three selected con-ventional air-conditioners in summer were simulated.Finally,the discussion was given,and an air-conditioner combining with convective and radiant cooling were proposed.The results indicated that the air-conditioner needed to be turned on in NZERB in hot-summer and cold-winter zone due to the room air temperature in off-air condition ranged from 32℃to 36℃,which was higher than designed indoor environment temperature in sum-mer,but the indoor environment of NZERB under three selected conventional air-conditioners could not meet the requirements of energy saving and comfort at the same time,and a proposed convective-radiant air-conditioner could be fast,stable,and energy saving.The findings can provide a reference for conducting active technology in NZERB.