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Plants and Equipment
Published in Carl Bozzuto, Boiler Operator's Handbook, 2021
Packing seals the space along the shaft, where it penetrates the casing, to limit leakage. Some leakage through the packing is essential to lubricate the packing to shaft joint. If the packing is tightened enough to stop or reduce the leakagetoo much, then the packing and shaft rub with deterioration of each. Manufacturers started making rotating pumps with shaft sleeves to help with that problem. The sleeve was like a pipe, or tube, that slipped over the shaft. It was either clamped with other parts or threaded onto a matching thread on the shaft to make it removable. That way, if the pump was run with the packing dry, and the shaft sleeve was torn up, all that was needed was to replace the sleeve, not the entire shaft.Ifthe annual replacement of shafts and shaft sleeves is common, it is because the operators consistently tightened the packing too much. If the proper amount of leakage is unknown, try measuring the temperature of what leaks out and compare it with the temperature of the liquid inside the pump. It should not rise more than 5 degrees. That does not work for boiler feed pumps. The liquid in the boiler feed pump would flash. Usually, look for a tiny stream flowing out of the packing as a rule. A tiny stream means something no larger than a pencil lead. Over time, a relationship between the tightness of the packing and the right amount of leakage will be learned. The pump will usually indicate when it is too tight, as it will wear the sleeve or shaft until it gets enough flow. In that case, pay attention what the pump needs and allow that leakage.
Materials
Published in Sumit Sharma, Composite Materials, 2021
Stone wool is a furnace product of molten rock at a temperature of about 1600°C, through which a stream of air or steam is blown. More advanced production techniques are based on spinning molten rock in high-speed spinning heads somewhat like the process used to produce cotton candy. The final product is a mass of fine, intertwined fibers with a typical diameter of 2–6 µm. Mineral wool may contain a binder, often a Ter-polymer, and an oil to reduce dusting. Though not immune to the effects of a sufficiently hot fire, the fire resistance of fiberglass, stone wool, and ceramic fibers makes them common building materials when passive fire protection is required, being used as spray fireproofing, in stud cavities in drywall assemblies, and as packing materials in fire-stops. Other uses are in resin-bonded panels, as filler in compounds for gaskets, in brake pads, in plastics in the automotive industry, as a filtering medium, and as a growth medium in hydroponics.
Lattice Boltzmann Method for Modeling Convective Heat Transfer in Porous Media
Published in Yasser Mahmoudi, Kamel Hooman, Kambiz Vafai, Convective Heat Transfer in Porous Media, 2019
Gholamreza Imani, Kamel Hooman
Liu and Wu (2016) employed the LBGK model to study the pore-scale forced convection in a 3D reconstructed porous medium with applying the constant temperature boundary condition at the solid–fluid interface instead of the conjugate heat transfer conditions. Chiappini (2018) employed a hybrid lattice Boltzmann method (i.e., an D2Q9 LBGK for the hydrodynamic and FV method for thermal simulations) to study natural convection in open-cell metal foams. The metal foam geometry was reconstructed via packing the elementary Kelvin unit cell. As shown in Figure 10.9, Chiappini (2018) compared the results of the Nusselt number from his simulation with those available from the experimental data.
Elastic properties evaluation of composite metal foams
Published in Mechanics Based Design of Structures and Machines, 2023
In this section, first, a convergence study is carried out and then variation in the results due to the size of RVE is investigated. The comparative study is presented for the cases available in the literature to show the efficiency and accuracy of the current approach. In the end, some parametric studies are carried out to investigate the effects of different geometrical and material parameters, such as the size of the spherical particles, material of the matrix, packing factor and microporosities. Unless otherwise mentioned, it is assumed that the spherical particles are made of stainless steel with 10% microporosity in their walls. Similarly, the matrix is made of aluminum with 30% microporosity. Furthermore, it is assumed that the packing factor for the composite metal foam is ranging from 45% to 60%. For RVE analyses in Abaqus, quadratic tetrahedral elements with ten nodes (C3D10) are used.
Experimental and numerical investigations on the local wall heat transfer coefficient in a narrow packed bed with spheres
Published in International Journal of Ambient Energy, 2022
Surfarazhussain S. Halkarni, Arunkumar Sridharan, S.V. Prabhu
To determine the wall heat transfer coefficients (hw) in a packed bed, Dekhthyar et al. (2002) have conducted experiments. These researchers have done work on annular packed bed with a single layer 8.9 mm glass spheres packing. Multilayer packing in the annulus with different sphere sizes is also attempted in their work. A sliding hermetically sealed glass tube with air was kept at the center of the test section. For a single tube with 52 mm, inner diameter copper pipe was packed with 0.9, 3.2 and 8.9 mm glass spheres and experiments were conducted using 47% aqueous glycerine solution while on the outer wall of packed bed constant heat flux boundary condition is maintained. Using copper-constantan thermocouples, the temperatures on the packed bed outer wall were measured. Near the exit region at (x/Di) = 9.03, the radial temperature profiles were also measured using thermocouples. The bulk fluid inlet temperature, bulk fluid exit and surrounding air temperatures are measured using calibrated thermocouples. Based on the measurements of above-mentioned parameters Equation (2) is used to calculate the wall heat transfer coefficient (hw):
Performance evaluation of poly-urethane foam packed-bed chemical scrubber for the oxidative absorption of NH3 and H2S gases
Published in Journal of Environmental Science and Health, Part A, 2018
Grace M. Nisola, Kris Niño G. Valdehuesa, Alex V. Anonas, Kristine Rose M. Ramos, Won-Keun Lee, Wook-Jin Chung
In this study, the potential of PU foam as a packing material in wet chemical scrubber is presented. An open-pore PU foam was characterized and packed in four chemical scrubbers for separate treatments of NH3 (Columns 1–2) and H2S (Columns 3–4). Effects of scrubbing liquid re-circulation rate (QL) and pH/oxidant levels were evaluated and correlated to the performance of the wet chemical scrubbers. The scrubbers were assessed in terms of gas removal efficiency (% RE) and outlet gas concentrations (Cout). Parameters such as total dissolved solids (TDS) and conductivity were measured to monitor the quality of the scrubbing solutions during operation. Finally, continuous operation was conducted to determine the elimination capacity (EC) of the scrubbers. The gas loading rates were gradually increased through step-wise increase of the inlet gas concentrations (Cin). After operation, the pressure drops along the columns were measured to observe the stability of PU as packing materials.