Evaluation of closed-loop U-Tube deep borehole heat exchanger in the Basal Cambrian Sandstone formation, Alberta, Canada
闭环深井筒换热器（DBHE）系统具有将热量从地热源传输至流体回路中的优势。本研究首次对加拿大阿尔伯塔省中部一个2330米深的地热储层中U型闭环DBHE进行了评估，以评估每单位能源投入所产生的能量。通过建立精细的从地表到地热源的数值模拟模型，我们可以了解该过程的效率。
结果表明，在U形回路的上升段，流体流动达到最高温度，而不是底部段，这意味着工质的绝热应从U形回路的上升段开始。结果显示，闭环系统的能量产出和能量投入比可以达到7 GJ/GJ。尽管这种效率令人鼓舞，但是通过换热面积的限制，回路在地热储层中采集到的热能的绝对量受到了限制。
Abstract
Closed-loop deep borehole heat exchanger (DBHE) systems for producing heat from geothermal sources have the advantage that the heat transfer fluid is contained within the loop. In this study, for the first time, a U-configuration closed-loop DBHE was examined to evaluate the energy produced per unit energy invested from a 2330-m-deep geothermal reservoir in central Alberta, Canada. A detailed earth model where the system is modeled from the surface to the geothermal source is used in a numerical simulation model to understand the efficiency of the process. The results reveal that the fluid flow reaches its highest temperature in the ascending section of the U-loop rather than the bottom section which implies that the insulation on the working fluid should start in the ascending section of the U-loop. The results demonstrate that the closed-loop system can achieve ratios of the energy produced and energy invested of 7 GJ/GJ. Although this efficiency is promising, the absolute amount of heat energy harvested is limited by the loop’s heat transfer area in the geothermal reservoir.
