Flow in the cavity with heat generating body finds wide domestic and industrial applications. The heat transfer characteristics and the irreversibility generated in the cavity depend on mainly the cavity size, aspect ratio of the heat generating body, and inlet/exit port locations. In the present study, effect of exit port locations on the heat transfer characteristics and irreversibility generation in a square cavity with heat generating body is investigated. A numerical simulation is carried out to predict the velocity and temperature fields in the cavity. To examine the effect of solid body aspect ratio on the heat transfer characteristics two extreme aspect ratios (0.25 and 4.0) are considered in the analysis. Fifteen different locations of exit port are introduced while air is used as an environment in the cavity. It is found that non-uniform cooling of the solid body occurs for exit port location numbers of 13 and beyond. In this case, heat transfer reduces while irreversibility increases in the cavity. These findings are valid for both aspect ratios of the solid body. Nomenclature A = cross-sectional area of solid body (m 2 ) a = aspect ratio b = length of protruding body (m) c = height of protruding body (m) h = heat transfer coefficient (W/m 2 K) I = irreversibility (W/m 3 ) k = thermal conductivity (W/mK) l = hydraulic radius of the solid body (m) Nu = Nuselt number P = pressure (Pa) P T = wetted perimeter of solid body (m) Ra = Rayleigh number HHH = volumetric entropy generation (W/ m 3 K) T = temperature (K) u = velocity in x-axis (m) v = velocity in y-axis (m) x = distance in x-axis (m) y = distance in y-axis (m) Greek symbols = thermal diffusivity (m 2 /s) = expansion coefficient (K ±1 ) " = viscosity (N.s/m 3 ) ) = kinematic viscosity (m 2 /s) & = density (kg/m 3 ) Subscripts F = fluid s = solid w = wall o = reference
IntroductionMixed convection in a cavity receives considerable attention due to its importance in many engineering applications. Some of these include energy transfer in rooms and units, and cooling of industrial machines and electronic
SUMMARYIn the present study, the simulation of mixed convection in a square cavity with protruding body having different aspect ratios is carried out. The governing flow and energy equations are solved numerically using a control volume approach. Air is used as fluid in the cavity while steel is considered as protruding body. To investigate the heat transfer characteristics due to different aspect ratios of the protruding body, Stanton number (St) variation with the aspect ratio is considered. The entropy analysis is carried out to determine the irreversibility generated in the cavity for different aspect ratios. The heat transfer to irreversibility ratio is determined for each aspect ratio. It is found that the aspect ratio influences the heat transfer characteristics and the irreversibility generated in the cavity, in which case, the heat transfer increases at high aspect ratio while the irreversibility reduces. Moreover, heat transfer to irreversibility ratio improves considerably at an aspect ratio of 3.
A numerical investigation aimed at understanding the flow and heat transfer characteristics of pulsating turbulent flow in an abrupt pipe expansion was carried out. The flow patterns are classified by four parameters; the Reynolds number, the Prandtl number, the abrupt expansion ratio and the pulsation frequency. The influence of these parameters on the flow was studied in the range 104<Re<5×104, 0.7<Pr<7.0, 0.2<d/D<0.6 and 5<f<35. It was found that the influence of pulsation on the mean time‐averaged Nusselt number is insignificant (around 10 per cent increase) for fluids having a Prandtl number less than unity. This effect is appreciable (around 30 per cent increase) for fluids having Prandtl number greater than unity. For all pulsation frequencies, the variation in the mean time‐averaged Nusselt number, maximum Nusselt number and its location with Reynolds number and diameter ratio exhibit similar characteristics to steady flows.
One way to determine the energy processing planning policy for energy optimization is achieved by energy analysis. In this study, the analysis was done by the calculated energy value used in each stage in a system as a whole to get a picture of how much the energy usage. This study contains the description of the extent to which the use of electrical energy to run the production process in the palm oil mill with a capacity of 45 tons by calculating the consumption of electrical energy in each station. The result of this research showed that the total electricity usage for production process at palm oil mill with the capacity of 45 Ton is 502,4 kW, with an efficiency level of electrical energy usage in production process equal to 73,05%.
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