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Published in J. Russell Boulding, Epa Environmental Engineering Sourcebook, 2019
The construction of slurry walls involves the excavation of a vertical trench using a bentonite-water slurry to hydraulically shore up the trench during construction and seal the pores in the trench walls via formation of a “filter cake” [3, pp. 2–17]. Slurry walls are generally 20 to 80 feet deep, with widths 2 to 3 feet. These dimensions may vary from site to site. There are specially designed “long stick” backhoes that dig to 90 foot depths. Generally, there will be a substantial cost increase for walls deeper than 90 feet. Clamshell excavators can reach depths of more than 150 feet. Slurry walls constructed at water dam projects have extended to 400 feet using specialized milling cutters. Depending on the site conditions and contaminants, the trench can be either excavated to a level below the water table to capture chemical “floaters” (this is termed a “hanging wall”) or extended (“keyed”) into a lower confining layer (aquitard) [3, p. 3–1]. Similarly, on the horizontal plane the slurry wall can be constructed around the entire perimeter of the waste material/site or portions thereof (e.g., upgradient, downgradient). Figure 1-1 diagrams a waste area encircled by a slurry wall with extraction and monitoring wells inside and outside of the waste area, respectively, along with a cross-section view of a slurry wall being used with the landfill cover technology [4, p. 1].
Characterization of the flow field around the primary heat exchanger of a residential gas furnace via particle image velocimetry
Published in Science and Technology for the Built Environment, 2022
Puyuan Wu, Weixiao Shang, Jun Chen, Asad Sardar, Ross Mielke, David Russell
The experiment setup, as shown in Figure 1, has two systems: a modified gas furnace and an air circulation system. The gas furnace model (Figure 2, the control electronics not shown) is composed of a blower, a secondary heat exchanger (SHE in Figure 2), four primary heat exchangers (clamshell type, labeled as Cells #1–#4), and two side baffles (SBL and SBR) from the inlet to the outlet. Each primary heat exchanger contains three portions (Figure 3). The upper and the middle portions have an oval- shaped cross-section while the upper portion has a larger size. The lower portion has an irregular cross-section.