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Advances in Gas Turbine Technology Part 8

Tham khảo tài liệu 'advances in gas turbine technology part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 200 Advances in Gas Turbine Technology 4.4 Jet reynolds number calculations The average velocity used to calculate the jet Reynolds number is calculated using the following equation V- 13 4d- 4 1 The data reduction equation for the jet Reynolds number is taken as Re p Vavg d p d y p p 13 X n d2 4 2 4.5 Uncertainty in jet reynolds number Taking into consideration only the measured values which have significant uncertainty the jet Reynolds number is a function of orifice jet diameter and volume flow rate and is expressed mathematically as follows Re f y d 3 Density and dynamic viscosity of air is not included in the measured variables since it has negligible error in the computation of the uncertainty in jet Reynolds number. The uncertainty in Reynolds number has been found to be about 2.2 . 4.6 Nusselt number calculations The total power input to all the copper plates was computed using the voltage and current the former being measured across the heater using the following equation V2 Qtotal V- VI 4 R The heat flux supplied to each copper plate was calculated using q Q 5 A total The heater gives the constant heat flux for each copper plate. The heat supplied to each copper plate from the heater is calculated using the following procedure Qcp i q X Acp i 6 Where i is the index number for each copper plate. The heat lost by conduction through the wood and to the surrounding by radiation is depicted in Figure 5 and has been estimated using the following equations for each plate. Th- T Qcond i kwoodAcp s i t 7 Jet Impingement Cooling in Gas Turbines for Improving Thermal Efficiency and Power Density 201 Qrad i sơAcp i Ơ4 - O 8 The actual heat supplied to each copper plate has been determined by deducting the losses from the total heat supplied to the heater. Qactual.i Qcp.i Qcond i Qrad i 9 The local convective heat transfer coefficient for each of the copper plate has been calculated using Qactual.i hi i A T -T cp iv s i in 10 The average temperature of the heated .