Abstract Proper selection of pumps has been an important issue for energy efficiency in geothermal energy. In a research conducted among machines that consume electricity, pumps come first with 25 %. Accurate estimation of pressure losses is a key point in order to select pump systems. Hot water from the geothermal area is carried by pipeline systems. In this study, extensive experimental study is conducted at Izmir Katip Celebi University Flow Loop using pure water for fluid temperature from 25 °C to 60 °C, for four various relative roughness values, and for Reynolds Number ranges from 6.2 × 104 to 7.8 × 105. This study has mainly two objectives: First is to identify if the absolute pipe roughness values of commercially available pipes vary according to the pipe diameter. The second objective is to investigate fluid temperature effects on frictional pressure losses in rough pipes and to present a new friction factor correlation for using in geothermal pipelines, considering the fluid temperature effects. Experimental study shows that absolute pipe roughness varies substantially for pipe diameters. The proposed friction factor has a good agreement with explicit formulas of Blasius (1913) and Taler (2016) equations for smooth pipes and Colebrook (1939) equation for rough pipes, as well as experimental data at various temperature values. Additionally, frictional pressure losses are accurately estimated using new friction factor equation. Results show that both relative roughness and temperature have a significant influence on the friction factor for turbulent flow through rough pipes. For this reason, pipe roughness should be determined correctly and the effects of fluid temperature on pressure losses should be considered. This may influence frictional head losses per unit length and, consequently, the predicted pumping requirements in geothermal pipelines.

中文翻译：

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单相液体流过地热管道的新摩擦系数公式

摘要 泵的正确选择一直是地热能能源效率的一个重要问题。在对消耗电力的机器进行的一项研究中，泵以 25% 的比例排在第一位。准确估计压力损失是选择泵系统的关键。来自地热区的热水由管道系统输送。在这项研究中，在 Izmir Katip Celebi 大学 Flow Loop 进行了广泛的实验研究，使用纯水进行流体温度从 25 °C 到 60 °C、四种不同的相对粗糙度值以及雷诺数范围从 6.2 × 104 到 7.8 × 105. 这项研究主要有两个目的：首先是确定市售管道的绝对管道粗糙度值是否随管道直径而变化。第二个目标是研究流体温度对粗糙管道摩擦压力损失的影响，并在考虑流体温度影响的情况下，提出用于地热管道的新摩擦系数相关性。实验研究表明，绝对管道粗糙度随管道直径而显着变化。提出的摩擦系数与用于光滑管道的 Blasius (1913) 和 Taler (2016) 方程和用于粗糙管道的 Colebrook (1939) 方程的显式公式以及不同温度值下的实验数据具有很好的一致性。此外，使用新的摩擦系数方程可以准确估计摩擦压力损失。结果表明，相对粗糙度和温度对通过粗糙管道的湍流摩擦系数有显着影响。为此原因，应正确确定管道粗糙度，并应考虑流体温度对压力损失的影响。这可能会影响每单位长度的摩擦水头损失，从而影响地热管道中预测的泵送要求。