Number Of Funnels Research Articles

Free convection heat transfer with surface radiation from infrared suppression system and estimation of cooling time

• The thermo-fluid characteristics of the full-scale infrared suppression (IRS) system used in the marine gas turbine as an exhaust system are numerically investigated here. • The combined impact of conduction, convection, and radiation on the cooling of the IRS system is intended to be explored. • Various relevant parameters are taken for the analysis, viz., Rayleigh number (Ra), number of funnels, funnel wall temperature, diameter ratio (DR), funnel overlapping (OL), and emissivity of the surface (ε). • A generalized correlation for Nusselt number is developed, considering surface emissivity and the number of funnels as an independent parameter that can be used for academic and industrial applications. • The novelty of the work lies in finding the heat transfer rate and cooling time of the IRS device with varying numbers of funnels (3 to 6 funnels) subjected to the combined effect of free convection and surface radiation. A numerical study is performed on Infrared Suppression (IRS) system having finite wall thickness to observe the combined effect of free convection and surface radiation. The main focus of this work is to obtain thermo-fluid characteristics of natural convection phenomena from the IRS system due to conjugate heat transfer and surface radiation. In addition, the time required to cool down the hot IRS system to atmospheric temperature is also estimated. For the numerical analysis, different governing equations (Navier-Stokes equation, energy equation, and radiation equation) are solved using the finite volume method (FVM) based solver of ANSYS Fluent v 15. Several pertinent parameters, viz., the number of funnels, Rayleigh number, inner surface temperature, geometric ratio, funnel overlapping, and surface emissivity, are varied to elucidate the heat transfer behavior. It is evident from the research that surface radiation has a significant influent on total heat transfer and should not be ignored. In addition, the total heat transfer rate rises with the number of funnels. Both non-dimensional induced mass flow rate and total heat transfer rate have maximum value for zero overlapping cases. At constant temperature contribution of radiative heat transfer varies from 10 to 38% with the rise in emissivity. The inclusion of radiation with convection lowers the cooling time significantly compared to convection alone.

Conjugate Free Convection Heat Transfer and Thermodynamic Analysis of Infrared Suppression Device With Cylindrical Funnels

AbstractA convection system can be designed as an energy-efficient one by making a considerable reduction in exergy losses. In this context, entropy generation analysis is performed on the infrared suppression system numerically. In addition, results due to heat transfer are also shown. The numerical solution of the Navier–stokes equation, energy equation, and turbulence equation is executed using ansysfluent 15.0. To perform the numerical analysis, different parameters such as the number of funnels, Rayleigh number (Ra), inner surface temperature, and geometric ratio are varied in the practical range. Results are shown in terms of heat transfer, entropy generation, irreversibility (due to heat transfer and fluid friction), and Bejan number with some relevant parameters. Streamlines and temperature contours are also provided for better visualization of temperature and flow field around the device. Results show that heat transfer and mass flow rate increase with the increase in the number of funnels. Entropy generation and the irreversibility rise with an increase in the number of funnels and geometric ratio. Also, the Bejan number decreases with an increase in Ra and the number of funnels. A cooling time is also obtained using the lumped capacitance method.

Entropy Generation Study of Turbine Exhaust Gas Through an Infrared Suppression Device

The present study involves analyzing entropy generation on an infrared suppression system for ocean liners. The governing differential equations (Navier–Stokes equation, energy equation) and the turbulence equations are solved using ANSYS Fluent 15.0. The relevant parameters, viz., Reynolds number at nozzle inlet ( to ), the temperature of nozzle inlet fluid (423 to 723 K), and the number of funnels (3 to 5), are varied. The effect of nozzle exhaust fluid temperature and funnel numbers is mainly studied in various quantities like heat transfer, entropy generation, and irreversibility caused by heat transfer and fluid friction. It is found that high-temperature exhaust fluid gives a higher value of entropy production. Moreover, entropy production because of heat transfer has the main contribution in total entropy production rather than that caused by fluid friction. Also, results indicate that the increase in the number of funnels (from 4 to 5 funnels) has a negligible effect on total irreversibility.

New Correlations for Flow and Conjugate Heat Transfer With Surface Radiation Characteristics of a Real-Scale Infrared Suppression System With Conical Funnels

AbstractThe consistent and accurate prediction of fluid flow and heat transfer characteristics in an infrared suppression (IRS) device is challenging due to the complex nature of the flow features. The cool ambient air intake and subsequent mixing of hot exhaust gas from the engine in the cargo/naval ships are done inside the IRS system. The objective is to propose correlations for mass entrainment and outlet temperature for the IRS device with conical funnels. The mass intake rate and funnel exit temperature are determined by a set of relevant operating and geometric parameters, such as Reynolds number, nozzle exhaust temperature, the number of funnels, and funnel overlap. In this study, the funnel walls are conducting with finite wall thickness, and the surface radiation is taken into consideration. Numerical simulations are performed for the real-scale IRS unit by solving the mass, momentum, energy, and radiation equations in the computational domain surrounding the system. Nonlinear regression analysis of the data is carried out using the Levenberg and Marquest (L–M) method to achieve an empirical correlation of mass intake ratio and outlet temperature ratio. The proposed correlation for mass intake ratio is valid within ±6%, and that of outlet temperature is valid within ±5% of the numerical data. The valid ranges for correlations are 6×105≤ nozzle Reynolds number ≤3×106; 2 ≤ number of funnel ≤ 5; −0.325 ≤ funnel-overlapping height ≤ 0.25; and 1.33 ≤ nozzle exit temperature ≤ 2.

Numerical investigation of flow and heat transfer characteristics of a full-scale infrared suppression device with cylindrical funnels

Numerical investigation of fluid flow and heat transfer characteristics of a full-scale Infrared suppression (IRS) device for ocean liners is carried out in the present study. The main objective of the work is to reduce the temperature of the turbine exhaust by incorporating the IRS device, which can be effectively used in stealth technology for naval ships. In this study, the IRS device having multiple cylindrical funnels are used for conducting the computational experiment. The numerical solution of the Navier-Stokes equation along with the turbulence as well as the energy equation is solved using the algebraic multigrid solver of ANSYS Fluent 15.0. Many pertinent input parameters, like the inlet Reynolds number, fluid temperature, the number of funnels, and their sizes with overlapping or without it, have been varied in a practical range to study the mass suction into the IRS device. It is observed that the mass entrainment increases with an increase in the nozzle fluid temperature as well as its velocity. Visualization of temperature plume and flow field over the IRS device with multiple funnels has been picturized in this analysis. Furthermore, correlations for the prediction of mass entrainment rate as a function of pertinent input parameters have been developed, which can be used for academic and industrial purposes.

Length of Multiple-Funnel Traps Affects Catches of Some Bark and Wood Boring Beetles in a Slash Pine Stand in Northern Florida

The multiple-funnel trap has gained broad acceptance for catching bark and ambrosia beetles since the trap was developed more than 25 years ago (Coleoptera: Scolytidae) (Lindgren 1983). The trap consists of black plastic funnels aligned vertically over each other, allowing for intercepted beetles to fall through the funnels into a wet or dry collection cup located on the bottom funnel. Currently, there are 2 national programs in the USA that use baited multiple-funnel traps for detecting exotic species: the Cooperative Agricultural Pest Survey (CAPS) and the Early Detection and Rapid Response program (EDRR) (USDA APHIS 2007; Rabaglia et al. 2008). Multiple-funnel traps are available in several sizes or lengths, expressed by the number of funnels (4-, 8-, 12or 16-unit) (Contech Inc., Delta, BC; Synergy Semiochemicals Corp., Burnaby, BC). The general expectation is that longer multiple-funnel traps catch more beetles. In support of that position, Hoover et al. (2000) found that catches of the striped ambrosia beetle, Trypodendron lineatum (Olivier) (Coleoptera: Scolytidae), in traps baited with the pheromone lineatin, increased as the length of traps were increased from 4 to 16 units. Haack & Lawrence (1997) found that catches of Tomicus piniperda (L.) were higher in 12and 16unit traps than in 8-unit ones. The objective of our study was to verify that long multiple-funnel traps (16-unit) catch more bark and wood boring beetles than short traps (8unit) in a slash pine (Pinus elliottii Engelm.) stand in northern Florida. We focused our study on common southern species attracted to the binary combination of ethanol and (–)-α-pinene used in the national programs (Miller 2006; Miller & Rabaglia 2009). We conducted 1 trapping experiment in a mature slash pine stand on the Osceola National Forest near Olustee, FL for 9 weeks in 2001 (29 Aug-8 Nov). PheroTech Inc. (now Contech) supplied separate lures for releasing ethanol and (–)-α-pinene at rates of approximately 0.6 and 2 g/d, respectively, as well as 8unit and 16-unit multiple-funnel traps. Traps were set in 6 blocks of 2 traps per block with all traps set 10-15 m apart. There were 2 treatments: (1) 8-unit; and (2) 16-unit multiple-funnel traps. One trap of each treatment type was randomly assigned to a position within each block. All traps were baited with ethanol and (–)-α-pinene. Each trap was suspended between trees by rope such that the bottom of each was 0.2-0.5 m above ground level. No trap was within 2 m of any tree. Collection cups contained approximately 150 mL of pink propylene glycol solution (Peak RV and Marine Antifreeze, Old World Industries Inc., Northbrook, IL). Using SYSTAT ver. 11.00.01 (SYSTAT Inc., Point Richmond, CA), we conducted two-sided t tests on data transformed by ln(y + 1) to remove heteroscedasticity (Pepper et al. 1997). Catches of Arhopalus rusticus nubilus (LeConte) (Cerambycidae) in 16-unit traps were 143% greater than those in 8-unit traps (Table 1).