竖进平出型地埋管群设计及换热特性研究

Design and Heat Transfer Characteristics of the Buried Pipe Group With Vertical Inlet and Flat Outlet

融合水平和竖直埋管换热器结构优点,设计了一种竖进平出型地埋管群增强换热系统,以成都某实验室为例建立浅层地热利用系统模型,研究负荷工况下其换热性能,探究了管间距、流量、土壤性质、环境温度、运行模式、地下水渗流对系统换热性能的影响。结果表明:相较于传统埋管结构,竖进平出埋地管群换热性能可提升65%以上;增大土壤利用率和减小热影响是影响强化换热的关键因素;间歇运行有利于提升系统换热量;浅层热泵系统受环境影响较大,夏季环境温度增加5◦C系统换热量下降约20%;当回填材料导热系数从1.2 W·m^(−1)·K^(−1)增至2.4 W·m^(−1)·K^(−1)时,系统换热量提高32%;系统换热量随渗流速度增大而增大,横向渗流方向换热量小于纵向,且相较于无渗流情况换热量分别提高14.8%和22.4%。

A enhanced heat exchange system with vertical-in and flat-out underground pipe group was designed by combining the structural advantages of horizontal and vertical buried pipes.Taking a laboratory in Chengdu as an example,a shallow geothermal utilization system model is established.The heat transfer performance under load condition is studied,and effects of pipe spacing,flow rate,soil properties,ambient temperature,operating mode and groundwater seepage on the system’s heat transfer performance were explored.The results show that the heat transfer performance of vertical in and horizontal out pipes can be improved by more than 65%compared with the traditional buried pipe.Increasing the soil utilization rate and reducing the heat impact are the key factors for enhancing heat transfer.Intermittent operation is beneficial to improve the system’s heat exchange efficiency.The shallow heat pump system is greatly affected by environment and the operating environment temperature in summer increases by 5℃,and the heat exchange efficiency decreases by 20%.When the thermal conductivity of backfill material increases from 1.2 W·m^(−1)·K^(−1)to 2.4 W·m^(−1)·K^(−1),the heat transfer efficiency is increased by 32%.The heat transfer efficiency increases with the increasing of seepage velocity.The heat transfer in the transverse seepage direction is less than that in the longitudinal seepage direction.The heat transfer in the transverse and longitudinal seepage directions increased by 14.8%and 22.4%respectively compared with no seepage.