Features of the tubular type of heat exchanger were examined experimentally in the current study. A rig is fitted with a novel insert as a negative heat transfer increase technique. The core fluid used is air under steady heat flux and a turbulent discharge state (6000 ≤ Re ≤ 19,500) conditions. Two heat transfer augmentation inserts are employed; one is the basket turbulators utilized as a turbulator and placed inside the heat exchanger with a constant pitch ratio (PR = 150 mm), and the other is the basket turbulators together with twisted tape that are installed at the core of the basket turbulators. The measurements illustrated that the Nusselt number (Nu) was found to be higher by about 131.8%, 169.5%, 187.7%, and 206.5% in comparison with the plain heat exchanger for basket turbulators and the combined basket–twisted tape inserts with y/w = 6, 3, and 2, respectively. The highest thermal efficiency factor of the increased tubular heat exchanger is 1.63 times more elevated than that of the simple heat exchanger on average, due to a binary basket-quirky strip for a twisting percentage y/w equal to 2 under steady pumping energy. Further, practical correlations for the Nusselt number, as well as friction characteristics, were established and presented.
In this paper, the ability of three types of drag reduction agents (DRAs) has been investigated to assess the impact of adding a small amount part per million (ppm) of polymer and surfactant, as well as nanoparticle substances, as drag improvers of internal flow via a pipeline network. The selected DRAs have been tested in the rotating disk apparatus (RDA) at various concentrations in the range of (50-1200) ppm and various rotating disk velocities in the range of (50-3000) rpm. Multiple trials have been done to figure out the best substance for enhancing drag force reduction. Impacts of the shear rate on viscosity (μ) at various concentrations of polymer and surfactant solutions have been analyzed with rheologic tests. The results detect that all selected substances have proved to be effective drag improvers in internal flow. Torque values were decreased with increased DRA concentrations, which caused a significant increase in drag reduction percentage (%DR). The drag reduction percentage of complex solutions at the highest concentration of 1200 ppm, results in around (44-47) % DR. In contrast, the results of the individual solutions at the same concentration results in around (32-38) % DR.
The validated dynamic model of a parabolic trough power plant (PTPP) is improved by the combination of a new feedwater circuit (feedwater/HTF circuit) and a reference feedwater circuit (feedwater/steam circuit) as well as the development of the steam turbine model. Such design represents the first effort of research to utilize a dual feedwater circuit inside the PTPP to increase the power output in the daylight from 50 to 68 MWel and raise night operating hours at a lower cost. The purpose of increasing the operating night hours at a power (48 MWel) as in the reference PTPP is to get rid of the fossil fuel backup system and rely only on the absorbed solar energy and the stored energy in the molten salt. During daylight hours, the feedwater circuit is operated using Feedwater/HTF. In the transient period, the feedwater/HTF circuit will gradually be closed due to a decrease in solar radiation. Furthermore, the rest of the nominal feedwater mass flow rate (49 kg/s) is gradually replenished from the feedwater/steam circuit. After sunset, the entirety of the feedwater is heated based on the steam extracted from the turbine. The purpose of this improvement is to raise the number of nightly operational hours by reducing the nominal load from 61.93 to 48 MWel as a result of low energy demand during the evening hours. Therefore, a comparison study between the reference model and this optimization (optimization 2) is conducted for clear days (26th–27th/June and 13th–14th/July 2010) in order to understand the influence of dual feedwater circuit. The comparison indicates that the operational hours of the power block (PB) will be obviously increased. Moreover, this improvement reduces based on the fossil fuel system at night. As the last step, an economic analysis was performed on the costs of the referenced and the optimized PTPP as a function of the levelized energy cost (LEC). The results illustrate that the specific energy cost of a PTPP with 7.5 h of storage capacity is lowered by about 14.5% by increasing the output of the PTPP from 50 to 68 MWel.
Drag reduction in turbulent flow may be significantly reduced by adding tiny quantities of fiber, polymer, and surfactant particles to the liquid. Different drag-reduction agents have proven to be effective in enhancing the flowability of the liquid when added. This study investigated the potential of decreasing the drag, turbulent flow, and pressure drop in horizontal pipe flow by using a mixture of modified xanthan gums (XGs). Xanthan gums are an environmentally friendly natural polymer complex. They can be extracted from xanthan gum plants and utilized to formulate different concentrations of complexes. The flowability of the xanthan gum was experimentally investigated in a 1-m-long pipe by using addition concentrations of 300 to 950 ppm, an inner diameter of 0.254 inches, and four different flow rates. The results revealed that the pressure drop was reduced considerably with an increase in the concentration of the additives. The mixture (xanthan gums plus water) resulted a favorable reduction in the pressure, which reached 65% at a concentration of 950 ppm. The results of the computational fluid dynamic simulation using the COMSOL simulator showed a change in the fluid velocity profiles, which became more parabolic. This occurred because of an increase in the mean fluid velocity due to the addition of the drag-reducing polymers.
In the pipeline networks field, GAL surfactant can reduce drag forces relatively using a small quantity part per million (ppm). Accordingly, the drag reduction (DR) enhancement is highly recommended in many industrial applications specifically the crude oil transportation aspect. GAL solution was experimentally investigated at various concentrations. The experiments were performed at low concentrations range from 50 to 300 ppm, and high concentrations range from 1000 to 2000 ppm. The rotating disk apparatus (RDA) was used at various speeds range from 50 to 3000 rpm in all experiments. Torque values of the GAL solutions were compared with water alone. The results clearly show that the different concentrations of the Glycolic Acid Ethoxylate Lauryl Ether (GAL) are good drag reduction agents (DRAs), with clear and high torque reading differences. Further, GAL solutions have the same tendency at all concentrations. The torque finding was enhanced with increasing concentration.
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