Mehaboob Basha

Entropy generation in a rotating channel

Abstract A computational study is performed on a three-dimensional turbulent flow and heat transfer in a rotating rectangular channel with an aspect ratio of 10:1, oriented 120° from the direction of rotations. Entropy generation due to heat transfer and fluid friction is computed and reported. To examine the influence of rotation number and density ratio on volumetric entropy generation rate, rotation number and density ratio are varied in the simulations. A numerical scheme employing a control volume approach is introduced to solve the governing equations of transport. A constant heat flux boundary condition at the leading and trailing edges of the channel is considered to resemble the blade heating. It is found that the rotation number and density ratio have a significant effect on the entropy generation rate in the channel. In this case, increasing the density ratio enhances the entropy generation rate, whereas increasing the rotation number modifies the trend of the entropy generation rate in the channel.

Flow and Heat Transfer Prediction in Rotating Rectangular Pin-Fin Channels (AR = 10:1)

Computations were performed to study the three-dimensional turbulent flow and heat transfer in a rotating narrow rectangular channel with staggered arrays of pin fins. The channel aspect ratio is 10:1, the pin length to diameter ratio is 1.0, and the pin spacing to hydraulic diameter ratio is 3.0 in both the streamwise (S L /D h ) and spanwise S T /D h ) directions. Various combinations of rotation numbers and coolant-to-wall density ratios were examined. A total of seven calculations have been performed with various rotation numbers and inlet coolant-to-wall density ratios. The rotation number and density ratio varied from 0.0 to 0.14 and from 0.1 to 0.40, respectively. The Reynolds number is fixed to 10,000. A finite volume code, FLUENT is used to predict the flow and heat transfer. The Reynolds stress model in conjunction with a two-layer model is used to compute the turbulent flow and heat transfer in the rotating channel. The computational results are in good agreement with experimental data.

Role of Cooling Techniques and Fuels in Enhancing Power and Efficiency of Gas Turbine Plants

Performance analysis of different gas turbine power plant configurations is presented in this paper. The work includes the effect of humidity, ambient inlet air temperature and types of fuels on gas turbine plant configurations with and without cooling technologies. Investigation also covers economic analysis. 20 MWe GE 5271RA and 40 MWe GE-6561B frames are selected for the present study. GT PRO software has been used for carrying out the simulations for a given location of Saudi Arabia. The relative humidity and temperature have been varied from 30 to 45 % and from 80 to 100° F, respectively. Fuels considered in the study are natural gas, diesel and heavy bunker oil. Results show that variation of humidity does not affect the gas turbine performance for all types of fuels. For GT only situation, for a decrease of ambient inlet air temperature by 10 °F, plant net output and efficiency have been found to increase by 4%, 1 % respectively, for all fuels. However, with addition of, fogger, plant net output and efficiency further increase by 3 %, 1% respectively. For all GT frames with fogger, the net plant output and efficiency are relatively higher as compared to GT only case for all fuels. The net plant output and efficiency for natural gas are higher as compare to other fuels for all GT scenarios. For 40 MWe frame with and without fogger, break even fuel price and electricity price have been found to vary from 2.03 to 2.22 USD/MMBTU and from 0.024 to 0.026 USD/kWh respectively.

Economic analysis of retrofitting existing gas turbine power plants with cogeneration facility

Cogeneration refers to the generation of combined heat and power (CHP), which is more efficient than a central power plant generating only electricity. The proportion of power generation using CHP is growing world-wide due to efficiency improvements and environmental benefits. Exhaust heat from GT power plants can be fed to boilers for producing steam. Steam is used for reservoir flooding, petrochemical industries, food processing etc. Operational gas turbine power generation plants can be retrofitted to co-generation power plant to produce steam in addition to electrical power. A computational preliminary economic feasibility study of retrofitting a given existing gas turbine power generation plant into a co-generation power plant is presented in this paper. A 80 MW GE-6111FA frame has been selected for the present study. The work includes the effect of relative humidity (RH), ambient air temperature, etc., on economics of the power plant. GTPRO/PEACE software has been used for carrying out the analysis. The RH and temperature have been varied from 30 to 45 % and from 80 to 100° F, respectively. For a decrease of inlet air temperature by 10 °F, net plant output and efficiency have been found to increase by 4.3 and 1.4 %, respectively for GT only situation. However, for GT with cogeneration scenario, for a decrease of inlet air temperature by 10 °F, net plant efficiency has been found to be increased from 33.3 % (GT only) to 63.4 % (cogeneration). For situations with and without cogeneration, break even fuel price has been found to vary from 2.6 to 3.0 USD/MMBTU respectively and break even electricity price have been found to vary from 0.018 to 0.022 USD/kWh respectively. For the simulation conducted, emission has been found to be 344352 ton/year.

Impact of Gas Turbine Frame Size on Efficiency of Gas Turbine Power Plants

A computational study to assess the effect of gas turbine (GT) frame size on efficiency of gas turbine power plant configurations is presented in this paper. The work includes the effect of relative humidity (RH), ambient inlet air temperature and frame size on gas turbine plant configurations with and without fogger unit. Investigation also covers economic analysis. 20 MWe GE 5271RA, 40 MWe GE-6561B and 70 MWe GE-6101FA frames are selected for the present study. GT PRO software has been used for carrying out the analysis including; net plant output and net efficiency, break even electricity price (BEEP) and break even fuel LHV price (BEFP), etc. The relative humidity and temperature have been varied from 30 to 45 % and from 80 to 100° F, respectively. Fuels considered in the study are natural gas, diesel and crude oil. Results show that variation of humidity does not affect the gas turbine performance appreciably for all GT frame size regardless of type of fuel. For a decrease of inlet air temperature by 10 °F, net plant output and efficiency have been found to increase by 4 and 1.7 %, 4.2 and 1.3 %, 4.7 and 1.8 %, respectively for 20 MW,40MW and 70MW for crude oil and for GT only situation. However, for GT with Fogger scenario, for a decrease of inlet air temperature by 10 °F, net plant output and efficiency have been found to further increase by 3.1 and 1.3 %, 3 and 0.9 %, 3.2 and 1.1 %, respectively for 20 MW,40MW and 70MW. For situations with and without fogger for crude oil, BEFP have been found to vary from 1.3968 to 1.3916, 2.13 to 2.0948, 2.387 to 2.4642 USD/MMBTU respectively for 20 MW, 40MW and 70MW and BEEP have been found to vary from 0.03142 to 0.0313, 0.02488 to 0.02504, 0.0229 to 0.0233 USD/kWh respectively for 20 MW, 40MW and 70MW.

Effect of Viscosity on the Pressure Gradient in 4-Inch Pipe

The pressure drop of liquids of different viscosities in multiphase flow is still a subject of research. This paper presents pressure drop measurements of water and oil single phase flow in horizontal and inclined 4 inch diameter stainless steel pipe at different flow rates. Potable water and Exxol D80 oil were used in the study. Experiments were carried out for different inclination angles including; 0°, 15°, 30° (upward and downward flows). Inlet liquid velocities were varied from 0.4 to 1.2 m/s and reference pressure was set at 1 bar. Water and Oil viscosities are 0.798 Pa.s and 1.56 Pa.s at 30°C, respectively.Pressure drop has been found to increase with increase in liquid velocity. Pressure drop has been observed to increase asymptotically with pipe inclination. Upward flows are associated with high pressure drop as compared to downward flows. The pressure drop of water is greater than that of oil for all inclinations. This difference can be attributed to the difference in fluid viscosities and densities. Measured pressure drops were compared with existing empirical relations and good agreement was noticed.Copyright

EFFECT OF INCLINATION ON THE AIR-WATER FLOW IN 4-INCH PIPE

Air-water two-phase flow in a pipeline often occurs in petroleum industry. It is important to study behavior of such flows in order to characterize two-phase flow in upstream production pipelines. This paper presents pressure drop measurements of air-water two-phase flow in a horizontal and inclined 4 inch diameter stainless steel pipe at different flow conditions. Experiments were carried out for different inclination angles including; 0°, 15°, 30° (upward and downward flows) and for different water-to-air volume fractions. Inlet superficial water velocities were varied from 0.3 to 3 m/s and reference pressure was set at 1 and 2 bars. For a given superficial air velocity, pressure drop has been found to increase with increase in superficial water velocity. Pressure drop was also affected by the inclination of pipe. Upward flows were associated with high pressure drops as compared to downward flows. Measured pressure drops were compared with existing empirical relations and good agreement was found.Copyright

Fluid Flow and Heat Transfer Prediction of a Rotating Tapered Inclined Channel

Fluid flow and heat transfer prediction were conducted to study the three dimensional turbulent flow and heat transfer in rotating tapered inclined channel. Channel orientation is 135° from the rotation direction. Three rotation numbers Ro = 0, 0.1, 0.2 & 0.4 and two inlet coolant-to-wall density ratios 0.1 and 0.40 were investigated, respectively, while keeping Reynolds number constant at 10000. The normalized velocity and temperature fields are presented at two axial locations. The local normalized Nusselt number and spanwise averaged Nusselt number values were reported for three walls; leading, trailing, and top walls. The results show considerable span-wise local Nusselt number variation across the leading, trailing and top walls as the rotation number and density ratio increases.Copyright