能源地下综合管廊热力响应特性现场试验

Field tests of the thermal response of an energy utility tunnel

能源管廊是基于土壤源热泵系统地埋管换热器和地下综合管廊提出的一种新型能源地下结构。该文依托焦作市龙源路地下综合管廊工程,在管廊底板中铺设换热管形成能源管廊底板,实测进/出口水温及管廊底板温度、应变等变化规律,探讨不同运行模式条件下能源管廊底板换热性能与热力响应特性。现场试验结果表明,换热过程中管廊底板不同位置的温度基本一致,但是温度应力存在差异;横向温度应力大于纵向温度应力,且横向温度应力由北至南逐渐变小;纵向温度应力中部位置大,两侧小;夏季散热工况受到最大热致压应力为1.35 MPa,冬季取热工况受到最大热致拉应力为0.89 MPa,均未超过管廊底板混凝土的强度值,换热过程不会影响管廊底板的结构安全;能源管廊底板的单位管长换热功率随进水温度的升高而增大;600 L/h流量条件下换热功率最高,间歇运行相比连续运行可以提升换热功率;不同的初始温度将导致换热功率出现巨大差异,冬季取热工况换热功率低于夏季排热工况换热功率。

[Objective]Energy utility tunnel is a new type of energy underground structure based on a soil-source heat pump system buried-pipe heat exchanger and underground utility tunnel.Currently,the thermal response mechanism of an energy utility tunnel is unclear,specifically the heat transfer efficiency and thermal stress of the energy pipe corridor floor.Based on the comprehensive pipe corridor project of Longyuan Road located in Jiaozuo City,a thermal response test was conducted under various test conditions to discuss heat transfer and mechanical properties of the energy pipe corridor.Heat exchange tubes were laid at the bottom of the pipe corridor to form an energy pipe corridor.The inlet and outlet water temperatures and the temperature and strain of the pipe corridor floor were measured.Subsequently,heat exchange performance and mechanical properties of the pipe corridor floor were discussed.The average initial temperature of the energy pipe gallery floor at a depth of 7 m was approximately 21.4℃in summer and 12.4℃in winter.Moreover,the initial average temperature of the soil layer under the bottom floor was approximately 20.2℃in summer and 13℃in winter.The maximum thermal compressive stress under the heat removal condition in summer is 1.35MPa,and the maximum thermal tensile stress under the heat extraction condition in winter is 0.89 MPa,both did not exceed the strength value of concrete in the pipe corridor bottom plate.Inlet water temperature increased from 30℃to 35℃,and heat transfer power increased from 22 W/m to 28.7 W/m,resulting in a heat transfer power increase of approximately 30%.Moreover,when the flow rates were 300 L/h,600 L/h,and 900 L/h,heat transfer power were 14.6 W/m,29.3 W/m,and 28.7 W/m,respectively.Compared with a continuous operation,an intermittent operation increased the heat transfer power from 30.9 W/m to 36.9 W/m on the second day and from 30.6 W/m to 35.4 W/m on the third day.When the initial average temperatures were 21.3℃and 12.5℃,the heat transfer power were 23.9 W/m and 51.6 W/m,respectively.The heat transfer power of winter heating conditions was 14.3 W/m,and that of summer heat removal conditions was 22 W/m.Field test results show that the temperature at various locations of the base plate of the corridor is the same in the process of heat transfer;however,temperature stress is different.The transverse temperature stress is greater than the longitudinal temperature stress,and the transverse temperature stress gradually decreases on moving from north to south.Furthermore,the longitudinal temperature stress is greater in the center and lesser on both sides.The heat transfer power decreases with the test time extension and gradually stabilizes,and the heat transfer power fluctuates greatly in the first two days;therefore,the test duration should be more than 48 h.The heat transfer power increases with the increase in water inlet temperature.Increasing the flow rate can improve the heat transfer power;however,a large flow rate can make the heat transfer insufficient,resulting in a decrease in the heat transfer power.Thus,an intermittent operation can ensure higher heat transfer power compared with that during a continuous operation.However,even when the operation time was extended,heat transfer power continued to decline compared with that on previous day.Therefore,the energy pipe gallery floor is more suitable for summer cooling.