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Compressed Air Systems
Published in Stephen A. Roosa, Steve Doty, Wayne C. Turner, Energy Management Handbook, 2020
Thus, the pressure drop for a given compressed-air application would decrease by approximately 87% if pipe diameter were increased by 50%, and would decrease by approximately 97% if pipe diameter were doubled [9]. The standard pressure-loss value tables in the Compressed Air and Gas Handbook [10] are consistent with the relationship in Equation 22-9. Figure 22-9 graphically shows the relationship between the compressed air flow rate and the pressure drop for 100 psig compressed air flowing through smooth pipe (of zero relative roughness) with various nominal diameters. Table 22-1 shows the data used to generate the Figure 22-9 graph. Note that pressure drop is greater in pipes with higher relative roughness factors. Fluid pipes’ relative roughness increases with age.
Mass Flowmeters—Coriolis
Published in Béla G. Lipták, Flow Measurement, 2020
Pressure drop varies significantly from one Coriolis flowmeter design to another. The highest drop designs approach a 100 psig drop, at the maximum rated flow of the meter, with water as the flowing media. The pressure drop becomes significantly greater with viscous products. Some designs have high pressure drop because they require high mass flow rates or fluid velocities (sometimes as great as 100 ft/s at maximum rated flow) in order to achieve measurable time or phase difference between the detectors mounted on the flow tubes. It is a common misconception that the high pressure drop in Coriolis flowmeters results predominantly from the bends in the flow tubes. The pressure drop depends upon both the effective length of the tube, which accounts for the tube bends, and the tube inner diameter. Straight-tube flowmeter designs typically have high pressure drop even though there are no tube bends, because they tend to use smaller diameter tubes than the equivalent bent tube designs. Better understanding of the relationship between tube geometry and the time or phase difference produced by the flow detectors has resulted in a variety of low pressure drop designs. Designs are currently being produced that have pressure drops of 10 psig or less, with water, at the rated full scale flow. The manufacturer’s literature gives the pressure drop for specific applications.
Fluid Mechanics
Published in Jiro Nagatomi, Eno Essien Ebong, Mechanobiology Handbook, 2018
Tiffany Camp, Richard Figliola
From this relationship we can surmise a few things. First, it is clear that the flow rate is proportional to the pressure drop. If there is no pressure difference (and no gravity), then there will be no flow. Flow is also inversely proportional to the viscosity and pipe length. Most notable is the fact that the flow rate is very much dependent on the pipe size. It is directly proportional to the pipe radius (or diameter) to the fourth power. This equation is valid for steady, laminar, fully developed flow in a horizontal pipe. If the pipe is not horizontal, gravitational effects are introduced and must be taken into consideration.
Comparative studies on convective heat transfer behaviour of nanofluids under turbulent flow with inserts
Published in International Journal of Ambient Energy, 2023
S. Anbu, J. Arunprasad, P. Kalidoss, C. Sivakumar
Nanofluids must be developed to improve heat transfer while minimising pressure drop in order to be effective in practical applications. As a result, the friction factor of Al2O3, CuO, and TiO2 nanofluids with and without spiralled rod inserts is evaluated experimentally in turbulent flow under isothermal circumstances. Fgures 12, 13 and 14 show the relationship between friction factor and Reynolds number. The nanoparticles in the base fluid cause a partial rise in friction factor as well as a tolerable pumping power penalty. The increase in pressure drop and friction factor is due to the fact that suspending solid nanoparticles in a fluid typically increases the viscosity relative to the base fluid. Because viscosity is proportional to pressure drop, a higher level of viscosity results in a greater amount of pressure drop. Another element that may be responsible for the rising friction factor of nanofluids is the chaotic motion and migration of nanoparticles in the base fluids. For 0.25 and 0.5% VC of Al2O3 nanofluids, respectively, the friction factor rises by 5.8 and 7.9%. For the same conditions, the rise is 7.2 and 8.1% for CuO nanofluids and 5.4 and 7.46% for TiO2 nanofluids. Once inserts are used, the friction factor is much higher. The friction factor rises with 0.25, and 0.5% VC of Al2O3 nanofluids are 12.05 and 15.49% for SRI 1 and 13.8, and 17.29% for SRI 2. The rise in friction factor for CuO nanofluids with the above VC is 12.12 and 15.66% for SRI 1 and 13.2 and 17.59% for SRI 2.
Optimization of heat transfer in shell-and-tube heat exchangers using MOGA algorithm: adding nanofluid and changing the tube arrangement
Published in Chemical Engineering Communications, 2023
Yacine Khetib, Hala M. Abo-Dief, Abdullah K. Alanazi, S. Mohammad Sajadi, Suvanjan Bhattacharyya, Mohsen Sharifpur
In Figure 8, the streamlines exhibit temperature changes in the nanofluid. By comparing the geometries with NB = 6, 8, and 10, it is clear that the baffles are a decisive factor in enhancing the HTR. An increment in HTR for triangular tube arrangement is reported to be slightly greater than that for rectangular tube arrangement. For example, when Re = 20,000, φ = 4%, and NB = 10, Nu for triangular tube arrangement is 2.2% higher than that for rectangular ones. Therefore, in addition to the effect of NB, the impact of tube arrangement can be taken into account as a feature that enhances the HTR. Nanoparticles are another parameter that can intensify the HTR. Although the nanofluid is the same for both arrangements, the nanoparticles receive a higher amount of heat due to the proximity of the tube to each other in the triangular tube arrangement. For instance, when Re = 15,000, NB = 10, and φ = 2%, the value of Nu for triangular tube arrangement is about 1.5% higher than that for rectangular one. When φ = 4%, this increase is 2%. The results shown in Figure 9 reveal that an increment in NB enhances the HTR and the pressure drop simultaneously. It is possible to deduce that an enhancement in the fluid viscosity increases the pressure drop. Therefore, as φ is enhanced, the pressure drop is intensified.
Exergy and energy analysis of low GWP refrigerants in the perspective of replacement of HFC-134a in a home refrigerator
Published in International Journal of Ambient Energy, 2022
Mohammad Hasheer Shaik, Srinivas Kolla, Bala Prasad Katuru
The pressure drop is created by the friction of the fluid and depends largely on the velocity of the fluid. In a condenser, the velocity of the refrigerant is reduced as the refrigerant condenses, since the liquid phase has a specific volume much lower than the gas phase. Therefore, most of the condenser pressure drop is induced in the desuperheating operation, when the refrigerant is still a gas. By reducing the pressure, the saturation temperature decreases, that is, the level of overheating increases. Decreasing the pressure difference from the low pressure side (evaporator) to the high pressure side (condenser) reduces the energy consumption in the compressor. The high evaporator pressure will also increase the density of the refrigerant gas. For each cycle, the compressor will transport more refrigerant through the system. Lower electricity consumption and greater cooling capacity will increase the total system performance i.e. COP.