Pressure drop in pipes can be calculated by using Darcy-Weisbach formula. In order to use this formula, Darcy friction factor should be known. The best approximation to Darcy friction factor for turbulent flow is given by Colebrook-White equation. This equation can only be solved by numerical root finding methods. There are several other approximate equations to Darcy friction factor with some relative error compared to Colebrook-White equation. In some of these equations the percentage error is so small that they can be used directly in place of Colebrook equation. In this study relative error of several equations are re-evaluated.
Fouling of heat exchangers causes the thermal-hydrolic performance of heat-transfer equipment to decrease with time. When the thermal hydrolic performance decreases to a minimum acceptable level, the heat exchanger has to be cleaned. The decision regarding periodic cleaning of the heat exchangers is generally based on thermoeconomic performance of the process. In this paper, coolant and seawater temperatures through seawater cooled shell and tube during 2500 operating hours have been measured and total fouling resistances have been founded. The dimensionless cost model and variation with the dimensionless time is examined by considering the various cost elements for the seawater cooled shell and tube heat exchanger.
Acoustic waves hold oscillations of pressure, displacement and temperature. The interaction of these effects in gas close to a solid surface generates thermoacoustic oscillations. Some prototypes of coolers are being constructed using the principles of thermoacoustics nowadays. Even though the coefficient of performance of thermoacoustic systems is lower than the conventional coolers, the concern on the thermoacoustic systems has been increased since these systems are cheap, simple and do not use harmful gases for the atmosphere and do not have any moving parts compared to the conventional coolers. Thermoacoustic coolers are one of the potential cooling technologies of the future.
The penetration of wind energy in power systems increasing and has began to influence overall power system behavior. This situation has to be investigated in order to sustain reliable power system operation. However, adequate models of power system components and wind energy conversion systems are needed to use in grid investigation studies and simulations. In this study, a review is given of the modeling issues about grid with wind power.
Today
Yesterday
This week
This month
All days
Number of views: 420