A 3D discrete FEM iterative algorithm for solving the water pipe cooling problems of massive concrete structures

Abstract

Water pipe cooling has been widely used for the temperature control and crack prevention of massive concrete structures such as high dams. Because both under-cooling and over-cooling may reduce the efficiency of crack prevention, or even lead to great harm to structures, we need an accurate and robust numerical tool for the prediction of cooling effect. Here, a 3D discrete FEM Iterative Algorithm is introduced, which can simulate the concrete temperature gradient near the pipes, as well as the water temperature rising along the pipes. On the basis of the heat balance between water and concrete, the whole temperature field of the problem can be computed exactly within a few iteration steps. Providing the pipe meshing tool for building the FE model, this algorithm can take account of the water pipe distribution, the variation of water flow, water temperature, and other factors, while the traditional equivalent algorithm based on semi-theoretical solutions can only solve problems with constant water flow and water temperature. The validation and convergence are proved by comparing the simulated results and analytical solutions of two standard second-stage cooling problems. Then, a practical concrete block with different cooling schemes is analyzed and the influences of cooling factors are investigated. In the end, detailed guidance for pipe system optimization is provided. temperature controlling, and block surface protection [3]. Among them, the water pipe cooling proves to be the most efficient and economic.Dating from the 1930s, the water pipe cooling technique was first used by the Bureau of Reclamation in Hoover Dam, of which the thin-walled metal pipes were embedded in the concrete block during construction period [1]. Since then, it spread over the world from common concrete to roller-compacted concrete (RCC), and from dams to sluices and other structures [4][5][6]. In the 1970s, a high-density polyethylene (HDPE) pipe with high thermal conductivity arose and soon took over metal pipe in hydraulic projects, such as Sayano-Shushenskaya Dam and Ertan Dam, because of its great flexibility for shaping [6]. Figure 1(a) shows the configuration of Jinping-I Arch Dam with 26 sections divided by temporary transverse joints. Each dam section was placed layer by layer at a vertical interval of 3 m. The cooling pipes were usually embedded in horizontal section planes like an S curve shown in Figure 1(b), with both vertical and horizontal pipe spacing of about 1.2-3.0 m. To keep the effectiveness, the pipe length should better not exceed 250 m. For those huge concrete structures like arch dams, which are first built by several parts and then joined together to meet their uneven deformations, the cooling process generally includes two stages. The firststage cooling begins several hours after the concrete placement, aiming to suppress the maximum concrete temperature rising. Before the joint grouting between neighboring parts, a second-stage cooling is carried out to make the inner temperature decrease till it gets near its...

Effect of pipe-cooling system on thermal-mechanical behaviour of PC box bridge girders at hydration age

“…At present, some scholars have proposed a three-stage pipe-cooling method for mass concrete (Chen et al 2011;Cheng et al 2016). The purpose of the first stage is to reduce the peak temperature of concrete, the second stage aims to disperse temperature difference and reduce the consequent stress, and the last stage is to stabilize the temperature of concrete.…”

“…Many methods have been proposed, such as pseudo three-dimensional finite element methods (Myers et al 2009), thermal-fluid coupling method (Liu et al 2013), p-version finite element method (Zuo et al 2015) and composite-element method (Chen et al 2011) to obtain more accurate calculation method for pipe-cooling system. In the thermal-fluid coupling method, the position and size of pipe are accurately modelled according to the design, which can accurately simulate the convection heat transfer between cooling water and concrete, and temperature rise of cooling water along pipe due to heat generated by cement hydration (Cheng et al 2016;Liu et al 2013;Liu et al 2015). In addition, the cooling effect is closely related to the cooling parameters when pipe-cooling is used in concrete structure.…”

“…In addition, the cooling effect is closely related to the cooling parameters when pipe-cooling is used in concrete structure. The determination of cooling parameters, namely cooling water temperature, cooling water flow rate, cooling time and cooling period is critical for temperature control of PC box bridge girders on the pier top (Cheng et al 2016).…”

Optimization Analysis of the Position of Thermometers Buried in Concrete Pouring Block Embedded with Cooling Pipes

“…Because the temperature and stress fields of concrete are so complicated during the water-pipe-cooling process, the US Bureau of Reclamation 2 Mathematical Problems in Engineering first provided a method to calculate the temperature field of a single steel cooling pipe without a heat source. Since then, numerical simulations of water-pipe cooling have always been an important research topic [7][8][9][10][11][12][13][14].…”

A monitoring-mining-modeling system and its application to the temperature status of the Xiluodu arch dam

“…Externally, the dam is under various loads, such as the water contact, air convection, and foundation interface (Hu et al, 2013;Mirzabozorg et al, 2014). Internally, cooling pipes act as a heat sink, the effect of which is related to many factors (Cheng et al, 2015;Liu et al, 2015;Qiang et al, 2015). To account for these complexities, we want to link the in situ monitoring and numerical modeling to make them a closed-loop system.…”