Showing papers on "Pressure drop published in 2014"
TL;DR: In this paper, the concentration overpotential is modelled as a function of flow rate in an effort to determine an appropriate variable flow rate that can yield high system efficiency, along with the analysis of pressure losses and total pumping energy.
302 citations
TL;DR: Typical structure models of high-efficiency particulate (HEPA) air filters based on CNTs are introduced and CNT air filters with a gradient nanostructure are shown to give a much better filTration performance in dynamic filtration.
Abstract: Air filtration in the free molecular flow (FMF) regime is important and challenging because a higher filtration efficiency and lower pressure drop are obtained when the fiber diameter is smaller than the gas mean free path in the FMF regime. In previous studies, FMF conditions have been obtained by increasing the gas mean free path through reducing the pressure and increasing the temperature. In the case of carbon nanotubes (CNTs) with nanoscale diameters, it is possible to filtrate in the FMF regime under normal conditions. This paper reviews recent progress in theoretical and experimental studies of air filtration in the FMF regime. Typical structure models of high-efficiency particulate (HEPA) air filters based on CNTs are introduced. The pressure drop in air filters operated in the FMF regime is less than that predicted by the conventional air filtration theory. The thinnest HEPA filters fabricated from single-walled CNT films have an extremely low pressure drop. CNT air filters with a gradient nanostructure are shown to give a much better filtration performance in dynamic filtration. CNT air filters with a hierarchical structure and an agglomerated CNT fluidized bed air filter are also introduced. Finally, the challenges and opportunities for the application of CNTs in air filtration are discussed.
242 citations
TL;DR: In this article, the authors present results of experiments on thermal conductivity, viscosity and Turbulent heat transfer behavior of Magnesium Oxide-water nanofluid in a circular pipe, where the volume fraction of nanoparticles in the base fluid is less than 1% (low concentration).
230 citations
TL;DR: In this paper, an experimental study is carried out to study the turbulent flow of COOH-functionalized multi-walled carbon nanotubes/water nanofluid flowing through a double tube heat exchanger.
203 citations
TL;DR: A comprehensive review of available studies regarding single and two-phase microchannels is presented and analyzed in this article, where different methodologies and correlations used to predict the heat transfer and pressure drop characteristics of micro-channels along the channel geometries and flow regimes.
179 citations
TL;DR: In this article, an experimental study is performed to assess the heat transfer characteristics and pressure drop of low concentrations of a new class of nanotubes, i.e., COOH-functionalized double-walled carbon nanotube (DWCNTs) suspended in water under turbulent flow in a double tube heat exchanger.
163 citations
TL;DR: In this paper, the authors evaluated the performance of low global warming potential refrigerants R1234ze(E) and R12 34ze(Z) for high-temperature heat pump systems in industrial applications.
Abstract: Low global warming potential refrigerants R1234ze(E) and R1234ze(Z) are anticipated to be the refrigerants of choice for high-temperature heat pump systems in industrial applications. Their thermodynamic attributes are thermodynamically, experimentally, and numerically assessed in this study. The thermodynamic assessment indicates that the theoretical coefficients of performances (COP) are maximized at a condensation temperature approximately 20 K below the critical temperatures for each refrigerant. However, when the volumetric capacity is inadequate, the actual COP differs from the theoretical COP because of the large pressure drop. The breakdown of irreversible losses, which are experimentally quantified at a condensation temperature of 75 °C, results in the largest portion of the total pressure drop. The simulation results obtained at condensation temperatures of 105 and 125 °C indicate higher COPs than that at 75 °C for R1234ze(Z). The major factor is the reduction in the irreversible loss caused by the pressure drop. The above assessments demonstrate that R1234ze(Z) is suitable for high-temperature applications rather than in typical air conditioners.
161 citations
TL;DR: In this article, the authors theoretically analyzed entropy generation, heat transfer enhancement capabilities and pressure drop for a flat-plate solar collector operated with single wall carbon nanotubes (SWCNTs) based nanofluids as an absorbing medium.
152 citations
TL;DR: A thermal, mechanical and hydrodynamic analysis of these receivers has been developed in this article, assuming constant heat flux in each axial discretized section of the tube wall, but considering circumferential temperature variations in the perimeter of the tubes caused by the difference between the heat flux received by the front part of tubes and by the rear part.
143 citations
TL;DR: In this paper, a combined experimental and numerical study on finned metal foam (FMF) and metal foam heat sinks under impinging air jet cooling was conducted on aluminum foams of 96.3% porosity and 8 PPI (pores per inch).
141 citations
TL;DR: In this article, a three-dimensional numerical approach incorporating the radiation, solar load, and turbine models was proposed to investigate the effects of solar radiation, turbine pressure drop, and ambient temperature on system performance in detail.
TL;DR: In this paper, the heat transfer coefficients and friction factor of TiO2/water nanofluid up to 3.0% volume concentration at an average temperature of 30°C were investigated in the Reynolds number range of 8000-30,000 for flow in tubes and with tapes of different twist ratios.
TL;DR: In this paper, a modified two-component, four-equation, nonhomogeneous equilibrium model was employed for the alumina/water nanofluid, which fully accounted for the effect of the nanoparticle volume fraction distribution.
TL;DR: In this paper, the performance of a VRFB with flow fields is analyzed and compared with the performance without flow fields, and it is demonstrated that the battery with flow field has a higher discharge voltage at higher flow rates, but exhibits a larger pressure drop.
TL;DR: In this paper, the first and second law efficiencies for a stainless steel closed-tube open rectangular cavity solar receiver were determined for a small-scale solar thermal Brayton cycle using a micro-turbine with low compressor pressure ratios.
TL;DR: In this article, a perforated louvered twisted tape (LTT) was used to enhance the convection heat transfer coefficient of a solar parabolic trough concentrator with a new wraparound cover.
TL;DR: In this article, a single annular flow boiling with deionized water in silicon microchannels was shown to significantly enhance the heat transfer coefficient (HTC) and critical heat flux (CHF) in the self-stabilized and single flow boiling regime.
TL;DR: In this article, a three-dimensional solid-fluid conjugated model is coupled with a simplified conjugate-gradient method to optimize the flow and heat transfer in a water-cooled, silicon-based double-layer microchannel heat sink (MCHS).
TL;DR: In this paper, the influence of inclined vortex rings (VR) on heat transfer augmentation in a uniform heat-fluxed tube has been investigated experimentally, and the experimental results show a significant effect of the presence of the VRs on the heat transfer and pressure loss over the smooth tube.
TL;DR: In this article, the authors presented a study on heat transfer augmentation in a solar air heater channel fitted with multiple V-baffle vortex generators (BVGs) during the test air was passed through the test channel under a uniform wall heat-flux of the absorber plate.
TL;DR: In this paper, the authors examined numerically the heat transfer enhancement in a pipe partially filled with a porous medium under local thermal non-equilibrium (LTNE) condition, where the flow inside the porous material was modelled using the Darcy-Brinkman-Forchheimer model and the effect of different parameters such as, inertia (F), Darcy number (Da), conductivity ratio, porosity and particle diameter on the validity of local thermal equilibrium (LTE) were studied.
TL;DR: The present study addresses this limitation by discussing the development of two consolidated mini/micro-channel databases, used to assess the accuracy of previous models and correlations as well as to develop ‘universal’ correlations that are applicable to a large number of fluids and very broad ranges of operating conditions.
TL;DR: In this article, the influence of the CO2 injection rate, the induced fracture permeability near the wellbores, the injection/production well perforation placement, the working fluid, and the heat transfer between the well-bores and the surrounding reservoir was analyzed.
TL;DR: In this article, the heat transfer coefficient and friction factor of TiO2 and SiO2 water-based nanofluids flowing in a circular tube under turbulent flow are investigated experimentally under constant heat flux boundary condition.
TL;DR: In this article, the authors investigated the energy impacts and air quality consequences of high efficiency filters installed in commercial buildings and found that increased filter pressure drop decreased flow, cooling capacity, and power.
TL;DR: In this paper, the authors explored the effects of the double counter twisted tapes on heat transfer and fluid friction characteristics in a heat exchanger tube and demonstrated that the Nusselt number, friction factor and thermal enhancement efficiency were increased with decreasing twist ratio.
TL;DR: In this article, a volume-of-fluid method for a flow channel having a hydrophilic plate in the middle of the channel was used to investigate the process of water removal and transport in a proton exchange membrane (PEM) fuel cell.
TL;DR: In this paper, the forced convective and subcooled flow-boiling heat transfer of CuO/water nanofluid as well as fouling rate were experimentally quantified for different dilute concentrations of CUO nanoparticles in water over a range of mass flux.
TL;DR: In this paper, a 3D numerical model for engine exhaust-based thermoelectric generator (ETEG) system is developed, and the exhaust channel size needs to be moderate to balance the heat transfer to TEG modules and pressure drop along channel.
TL;DR: In this paper, the authors used an alumina and titania nano-coolant (NC) to enhance the heat dissipation performance of an air-cooled radiator.