Investigation of the effects of three different type conical buıildings on pipe inlet flow by numerical method

The effective parameters on pipe flow are the mouth structure at the pipe inlet, the surface roughness of the pipe wall, the heating or cooling process that begins immediately at the pipe inlet, and the Reynolds number. In the fluid entering to the pipe, the mouth of the pipe has a significant effect on the pipe inlet flow. In applications, it is seen that there are three different arrangements of pipe inlet: conical, protruding and sharp edges. Protruding and sharp-edged pipe inlets cause to a turbulent and a distorted profile at the pipe entrance. Conical pipe inlet type, which has a structure like a bellmouth, cause to a turbulent and smooth velocity profile at the pipe inlet flow. These pipe inlet types are used for purposes such as increasing the heat transfer rate in heat transfer applications that begin at the pipe entrance, reducing local pressure losses in the pipe entrance. In this study, the effects of conical type, available in three different types named as elliptical, airfoil and simple radius, on pipe flow were comparatively investigated by numerical method. The effects of these three conical types inlets on pipe flow, differ from each other in terms of manufacturing process and cost, have been investigated for air pipe flows being steady and isothermal in the the Reynolds number range of 600≤Re≤200000. Time-averaged flow equations were used for numerical simulation of pipe flows and SST k-omega turbulence model was used to solve the turbulence existed in the flow. The pressure loss of the entry pipe flow and the velocity profile at the pipe entrance were investigated comparatively by all three inlet types without changing the pipe radius, fluid viscosity and temperature. As a result, the pressure losses found for each flow were converted to the pressure loss coefficient 〖(C〗_P) and its change with the Reynolds number was observed. As the Reynolds number increases, C_P values decreases for all three input types. Result has shown that the inlet type with the highest pressure loss is the simple radius and with the least pressure loss is the elliptical profile inlet. The mean absolute deviation of velocity profiles produced by those three inlet types at the pipe inlet values from the pipe cross-sectional mean velocity profile were measured at each Reynolds number. According to the analysis, the simple radius velocity profile creates a smoother velocity profile at low Reynolds number flows (laminar flow) and cause to a very distorted velocity profile at higher Reynolds numbers compared to the other inlet types. As a result, although the velocity profiles produced by the elliptical profiled inlet type and the airfoil profiled inlet type are very close to each other in all Reynolds numbers, the elliptical inlet type seem to have a smoother velcity profile at pipe inlet. The degree of proximity of the velocity profile generated by inlet type to the pipe crossectional mean velocity profile has a performance-enhancing effect for the starting downstream.