Volume 62

A Study on Thermal Performance of an Increasing-Pressure Endothermic Power Cycle with a Geothermal-well Downhole Heat Exchanger Zheng Wang, Tao Liu, Xinli Lu, Wei Zhang, Jiali Liu, Lei Chen

Abstract

In this study, thermal performance of anincreasing-pressure endothermic power cycle (IPEPC) has been numerically investigated. In the IPEPC, a downhole heat exchanger (DHE) is used to replace atraditional evaporatoron the ground. Matching relationships amongfour key parameters (DHEinlet pressure, DHElength, geothermal water temperature, and geothermal water mass flow rate) and the working fluid mass flow rateare quantitatively analyzed.The research results indicate that, when the DHE inlet pressure is 3.7MPa and the geothermal water temperature is 95°C, the optimal working fluid mass flow rate is 9kg/s, corresponding to amaximum net poweroutputof 45.11kW. When the geothermal water temperature is 130°C, the optimal working fluid mass flow rate is 9.5kg/s, withamaximum net power outputof111.7kW. As the geothermal water mass flow rate increases, the optimal working fluid mass flow rateincreases synchronously, and the net power output under this matched operating condition also shows an upward trend. Under the conditionthatthe working fluid mass flow rate is low (ranging from 3to 6kg/s), using a shorter DHE length results in a better thermal performance.When theworking fluid mass flow rateis high (ranging from 6to 12 kg/s), using a longer DHE is an effective way to increase the net power output.The findings of this study provide theoretical guidance for IPEPC system optimization and engineeringdesign.

Keywords increasing-pressure endothermic process geothermal power cycle, downhole heat exchanger, thermal performance analyses