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

A 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 ANSYS Fluent 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 Ra. 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.

PERPINDAHAN PANAS HYBRID PHOTOVOLTAIC DAN THERMOELEKTRIC GENERATOR DENGAN HOT MIRROR

Heat transfer is the transfer of energy from one area to another due to the temperature difference between these areas. Wasted heat energy can be converted into electricity using (TEG) between the hot and cold sides. If the temperature difference is more significant, the efficiency may increase along with the operating temperature of the TEG-type material. So in this study, the author will calculate the heat transfer that occurs in Photovoltaic (PV), Thermoelectric Generator (TEG), and Hot Mirrors by utilizing thermal energy light produced from Muxindo LED bulbs with 10 Watt, 15 Watt, and 20 Watt power. The results of this study indicate that by using 10, 15, and 20 Watt LED bulbs for free convection heat transfer, the power generated from each point increases because it passes through several obstacles from objects that experience a decrease in temperature to PV and TEG, with the characteristics of the displacement. The movement of molecules from the medium importance follows convection heat at every point of transfer in the intermediate substance. The most significant power generated from radiant heat transfer is about 0.1873 Watt. It occurs on the surface of the fresnel lens using a 20 Watt LED bulb with the characteristic that the radiation propagates in a straight line and does not require an intermediate medium to transfer heat from one substance to another. The most significant conduction heat transfer power, 0.2453 Watt, occurs in Fresnel Lens using a 20 Watt LED bulb with heat transfer characteristics in solid objects.

Simultaneous optimization of inclination angle and fin characteristics on heat transfer in a rectangular enclosure

This paper examines the prospect of increasing or decreasing the heat transfer through a rectangular enclosure with an aspect ratio of 2 in two Rayleigh numbers 105 and 106 by optimizing its inclination angle and the parameters of a highly conductive thin fin attached to its hot surface. The enclosure is heated from below, and the dominant heat transfer mechanism within the enclosure is the free convection. Optimization is performed by particle swarm optimization algorithm. The equations of energy, continuity, and momentum for free convection heat transfer in the enclosure are discretized by the finite volume method and are numerically solved. The optimization objective is to adjust the enclosure inclination angle and the fin parameters (position and height), so that heat transfer into the cold wall becomes minimized or maximized. The attained results reveal that the heat transfer through such an enclosure can be increased significantly up to 23% by its inclination angle 20.6° and the addition of a thin fin at the optimal location 0.72 and optimal height 0.2 in Rayleigh 106. Also, the obtained results show that heat transfer can be decreased up to 32% by the slight adjustment of its inclination angle 1.7° and addition of a thin fin at the optimal location 1.41 and optimal height 0.2 in Rayleigh number 105.

Temperature regime of painted parts in awning-type drying chambers at low ambient temperatures

The paper considers the problem of colouring large-sized objects, such as modules of sea and river vessels at low ambient temperatures. The temperature distribution depends on the thermal resistance of the walls of the drying chamber, the main characteristics of the heater fan, the dimensions of the chamber and the painted module, the gaps between the walls. The calculation should take into account the aerodynamic resistance of the drying chamber with the part placed in it, the influence of free convection, heat loss and the peculiarities of air distribution inside the shelter. The paper presents the results of a study of the influence of the size of the drying chamber, the size of the painted module, ambient temperatures and air coming from the heater, fan parameters, methods of placing the fan and exhaust ventilation on the range of air temperature changes in the tent. The methods of numerical modelling and experimental studies were used in the study. Based on the results obtained, a calculation method is proposed that allows determining the decrease in temperature inside the chamber relative to the temperature of the air coming from the heater. To automate the calculations, a program has been developed to determine the parameters of the air after heating with a fan heater.

Lattice Boltzmann Simulation for Flow Inside Porous Open-Ended Medium with Partially Thermally Active Walls

Free convection heat transfer and flow characteristics in an open-ended enclosure occupied with fluid saturated porous media is highlighted in the present paper. All numerical investigations are achieved using the mesoscopic approach Thermal Lattice Boltzmann Method (TLBM) by using the Darcy- Forchheiman model. The bottom and the top sides of the porous enclosure are thermally isolated with complete or partially heated vertical wall facing the opening sidewall. The partial slice of left wall of the enclosure with a fixed heating length as (H /3), is isothermally heated at the middle, top and bottom locations. However, right side is open to the ambient physical conditions. The influences of partial heating location on free convection characteristics, namely isotherms, streamlines, centerline variations of horizontal and vertical, average and local Nusselt numbers are explored for Darcy number of 0.01, porosity of 0.4, Rayleigh number of =106 and unity Prandtl number.

A technique to measure turbulent free convective heat transfer in a vertical tall cavity

A time-average technique was developed to measure the unsteady and turbulent free convection heat transfer in tall vertical enclosure using a Mach-Zehnder interferometer. The method used a digital high speed camera to obtain the time-averaged heat transfer rates. Optical heat transfer measurements were made in a differentially heated vertical cavity with isothermal walls. The cavity widths (distance between the plates) were L = 12.7, 32.3, 40, and 56.2 mm. The corresponding Rayleigh numbers were about 3X10[superscript] 3, 5 X 10⁴, 1 X 10⁵, 2.7. X 10⁵, respectively and the enclosure aspect ratio ranged from A=18 to 76. The test fluid was air and the temperature differential was about 15 K for all the measurements. Finite fringe interferograms were taken with a high speed camera. Interferograms of the fluctuating temperature field were captured for ten seconds at a frequency of 100Hz. These images were enhanced and processed using MATLAB to measure the local time-averaged heat transfer rate. This time-averaged heat flux was measured at many locations along the vertical cavity walls in order to obtain the spatial average. To validate the proposed technique, the average Nusselt number was compared to measured values and correlations from the literature. In both laminar and turbulent flow conditions, the current measurements compared well with the ElSherbiny correlation.

A technique to measure turbulent free convective heat transfer in a vertical tall cavity

A time-average technique was developed to measure the unsteady and turbulent free convection heat transfer in tall vertical enclosure using a Mach-Zehnder interferometer. The method used a digital high speed camera to obtain the time-averaged heat transfer rates. Optical heat transfer measurements were made in a differentially heated vertical cavity with isothermal walls. The cavity widths (distance between the plates) were L = 12.7, 32.3, 40, and 56.2 mm. The corresponding Rayleigh numbers were about 3X10[superscript] 3, 5 X 10⁴, 1 X 10⁵, 2.7. X 10⁵, respectively and the enclosure aspect ratio ranged from A=18 to 76. The test fluid was air and the temperature differential was about 15 K for all the measurements. Finite fringe interferograms were taken with a high speed camera. Interferograms of the fluctuating temperature field were captured for ten seconds at a frequency of 100Hz. These images were enhanced and processed using MATLAB to measure the local time-averaged heat transfer rate. This time-averaged heat flux was measured at many locations along the vertical cavity walls in order to obtain the spatial average. To validate the proposed technique, the average Nusselt number was compared to measured values and correlations from the literature. In both laminar and turbulent flow conditions, the current measurements compared well with the ElSherbiny correlation.