Transient Heat Transfer Experiments in Complex Passages

2005 ◽  
Author(s):  
Rico Poser ◽  
Jens von Wolfersdorf ◽  
Klaus Semmler
Keyword(s):  
Heat Transfer ◽  
Internal Heat ◽  
Direct Consequence ◽  
Data Evaluation ◽  
Transient Heat Transfer ◽  
Inlet Temperature ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients ◽  
Blade Cooling

Transient heat transfer experiments were performed in a model of a multi-pass gas turbine blade cooling circuit. The inner surface of the Plexiglas model was coated with thermochromic liquid crystals in order to determine the internal heat transfer coefficients. A change in inlet temperature is applied using a pre-cooled heat exchanger. As for simple geometries the analytical solution of Fourier’s equation can often be directly used for data evaluation, one ought to pay attention to complex passages. The reason has to be seen that the flow in complex passages has to be characterized by local and time dependent fluid temperatures. As a direct consequence data evaluation might be limited to small evaluation areas especially far downstream. Otherwise the uncertainties in the heat transfer results will increase substantially. In the present study the sensitivity of the transient method for complex passages has been analyzed theoretically and applied experimentally.

A Two-Dimensional Analytical Method for Turbine Blade Cooling Design

2017 ◽  
Author(s):  
Chen Li ◽  
Jian-jun Liu ◽  
Bai-tao An ◽  
Zhi-qiang Yu
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Analytical Method ◽  
Internal Heat ◽  
Transfer Coefficients ◽  
Simple Method ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients ◽  
Blade Cooling ◽  
Cooling Design

Turbine blade cooling design involves many complex fluid-thermal coupling issues. Using complete 3D CFD and FEA method would increase the cost of computing; on the other hand, the simplified 1D analytical method would lose too much important blade geometric information when employed in preliminary cooling design. In order to shorten design period and improve the design efficiency, the current 2D analytical method has been developed from a conceptual design that stacking a series of 2D radial sections to shape a quasi-3D blade model attached with the internal fluid flow network. Each of those 2D radial sections could maximally retain the actual blade profile, thus making it more authentic for accomplishing the numerical calculations of turbine cascade flow and heat transfer. For the gas side, methods for calculating external heat transfer coefficients have been investigated, and a simple method for considering the effect of thermal barrier coating on 2D conduction model is proposed. For internal cooling channels, a general calculation method of compressible pipe flow under rotating condition has been derived for fast solving coolant mass flow rates and internal heat transfer coefficients supported by empirical correlations of Darcy resistance coefficient and Nusselt number. Those work are significant to achieve the parametric cooling design by means of modifying and controlling geometric parameters and boundary conditions. Consequently, a real turbine blade case by applying the current 2D analytical method to obtain a quasi-3D blade temperature distribution is presented, demonstrating that this 2D analytical method is effective for turbine cooling design.

scholarly journals Comparison of Blade Cooling Performance Using Alternative Fluids

2002 ◽  
Author(s):  
Carlo Carcasci ◽  
Stefano Zecchi ◽  
Gianpaolo Oteri
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Gas Turbine ◽  
Film Cooling ◽  
Cooling System ◽  
Internal Heat ◽  
Transfer Coefficients ◽  
Cooling Systems ◽  
Heat Transfer Coefficients ◽  
Blade Cooling

CO2 emissions reduction has become an important topic, especially after Kyoto protocol. There are several ways to reduce the overall amount of CO2 discharged into the atmosphere, for example using alternative fluids such as steam or CO2. It is therefore interesting to analyze the consequences of their usage on overall performances of gas turbine and blade cooling systems. The presence of steam can be associated with combined or STIG cycle, whereas pure carbon dioxide or air-carbon dioxide mixtures are present in innovative cycles, where the exhaust gas is recirculated partially or even totally. In this paper we will analyze a commercial gas turbine, comparing different fluids used as working and cooling fluids. The different nature of the fluids involved determines different external heat transfer coefficients (external blade surface), different internal heat transfer coefficients (cooling cavities) and affects film cooling effectiveness, resulting in a change of the blade temperature distribution. Results show that the presence of steam and CO2 could determine a non negligible effect on blade temperature. This means that cooling systems need a deep investigation. A redesign of the cooling system could be required. In particular, results show that steam is well suited for internal cooling, whereas CO2 is better used in film cooling systems.

scholarly journals Heat Transfer in Rotating Serpentine Passages With Trips Normal to the Flow

1992 ◽  
Vol 114 (4) ◽  
pp. 847-857 ◽  
Author(s):  
J. H. Wagner ◽  
B. V. Johnson ◽  
R. A. Graziani ◽  
F. C. Yeh
Keyword(s):  
Heat Transfer ◽  
Turbine Blade ◽  
Large Scale ◽  
Flow Direction ◽  
Operating Conditions ◽  
Transfer Model ◽  
Transfer Coefficients ◽  
Flow Equations ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients

Experiments were conducted to determine the effects of buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. The experiments were conducted with a large-scale, multipass, heat transfer model with both radially inward and outward flow. Trip strips on the leading and trailing surfaces of the radial coolant passages were used to produce the rough walls. An analysis of the governing flow equations showed that four parameters influence the heat transfer in rotating passages: coolant-to-wall temperature ratio, Rossby number, Reynolds number, and radius-to-passage hydraulic diameter ratio. The first three of these four parameters were varied over ranges that are typical of advanced gas turbine engine operating conditions. Results were correlated and compared to previous results from stationary and rotating similar models with trip strips. The heat transfer coefficients on surfaces, where the heat transfer increased with rotation and buoyancy, varied by as much as a factor of four. Maximum values of the heat transfer coefficients with high rotation were only slightly above the highest levels obtained with the smooth wall model. The heat transfer coefficients on surfaces where the heat transfer decreased with rotation, varied by as much as a factor of three due to rotation and buoyancy. It was concluded that both Coriolis and buoyancy effects must be considered in turbine blade cooling designs with trip strips and that the effects of rotation were markedly different depending upon the flow direction.

Heat Transfer and Pressure Drop Correlations for Square Channels With 45 Deg Ribs at High Reynolds Numbers

2009 ◽  
Vol 131 (7) ◽  
Author(s):  
Akhilesh P. Rallabandi ◽  
Huitao Yang ◽  
Je-Chin Han
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Reynolds Numbers ◽  
Local Heat ◽  
Transfer Coefficients ◽  
Turbine Blade Cooling ◽  
Square Channel ◽  
Heat Transfer Coefficients ◽  
High Reynolds ◽  
Cooling Passage

Systematic experiments are conducted to measure heat transfer enhancement and pressure loss characteristics on a square channel (simulating a gas turbine blade cooling passage) with two opposite surfaces roughened by 45 deg parallel ribs. Copper plates fitted with a silicone heater and instrumented with thermocouples are used to measure regionally averaged local heat transfer coefficients. Reynolds numbers studied in the channel range from 30,000 to 400,000. The rib height (e) to hydraulic diameter (D) ratio ranges from 0.1 to 0.18. The rib spacing (p) to height ratio (p/e) ranges from 5 to 10. Results show higher heat transfer coefficients at smaller values of p/e and larger values of e/D, though at the cost of higher friction losses. Results also indicate that the thermal performance of the ribbed channel falls with increasing Reynolds numbers. Correlations predicting Nusselt number (Nu) and friction factor (f¯) as a function of p/e, e/D, and Re are developed. Also developed are correlations for R and G (friction and heat transfer roughness functions, respectively) as a function of the roughness Reynolds number (e+), p/e, and e/D.

The Measurement of Full-Surface Internal Heat Transfer Coefficients for Turbine Airfoils Using a Non-Destructive Thermal Inertia Technique

2002 ◽  
Author(s):  
Nirm V. Nirmalan ◽  
Ronald S. Bunker ◽  
Carl R. Hedlung
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
External Surface ◽  
Internal Heat ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Turbine Airfoils ◽  
Non Destructive ◽  
Internal Heat Transfer

A new method has been developed and demonstrated for the non-destructive, quantitative assessment of internal heat transfer coefficient distributions of cooled metallic turbine airfoils. The technique employs the acquisition of full-surface external surface temperature data in response to a thermal transient induced by internal heating/cooling, in conjunction with knowledge of the part wall thickness and geometry, material properties, and internal fluid temperatures. An imaging Infrared camera system is used to record the complete time history of the external surface temperature response during a transient initiated by the introduction of a convecting fluid through the cooling circuit of the part. The transient data obtained is combined with the cooling fluid network model to provide the boundary conditions for a finite element model representing the complete part geometry. A simple 1D lumped thermal capacitance model for each local wall position is used to provide a first estimate of the internal surface heat transfer coefficient distribution. A 3D inverse transient conduction model of the part is then executed with updated internal heat transfer coefficients until convergence is reached with the experimentally measured external wall temperatures as a function of time. This new technique makes possible the accurate quantification of full-surface internal heat transfer coefficient distributions for prototype and production metallic airfoils in a totally non-destructive and non-intrusive manner. The technique is equally applicable to other material types and other cooled/heated components.

Enhancement of Forced Convection Heat Transfer Using Twisted Heater With Exponential Heat Inputs

2013 ◽  
Author(s):  
Makoto Shibahara ◽  
Qiusheng Liu ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Forced Convection ◽  
Heat Generation ◽  
Swirling Flow ◽  
Generation Rate ◽  
Transient Heat Transfer ◽  
Heat Generation Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Plate Heater

Forced convection transient heat transfer coefficients have been measured for nitrogen gas flowing over a twisted heater due to exponentially increasing heat inputs (Q0exp(t/τ)). And then, the effect of heater configuration on transient heat transfer by a twisted heater has been investigated comparing to that of the plate heater. In the experiment, the platinum ribbon with a thickness of 0.1 mm and a width of 4.0 mm was used as a test heater. For heat transfer enhancements in single-phase flow, it was twisted at the central part of the heater with an angle of 90 degrees with respect to the upper part of the heater. The heat generation rate was exponentially increased with a function of Q0exp(t/τ). The gas flow velocity ranged from 1 to 4 m/s for the gas temperatures of 313K. The periods of heat generation rate ranged from 46 ms to 17 s. The surface temperature difference and heat flux increased exponentially as the heat generation rate increased with the exponential function. The heat transfer coefficients for twisted heater have been compared to those of the plate heater. They were 24 % higher than those of the plate one. The geometric effect (twisted effect) of heater in this study showed an enhancement on the heat transfer coefficient. It was considered that the heat transfer coefficients are affected by the change in the flow due to swirling flow on the twisted heater. Finally, the empirical correlations for quasi-steady-state heat transfer and transient one have been obtained based on the experimental data.

Effect of Heater Configurations on Transient Heat Transfer for Various Gases Flowing Over a Twisted Heater

2009 ◽  
Author(s):  
Makoto Shibahara ◽  
Qiusheng Liu ◽  
Katsuya Fukuda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Generation ◽  
Gas Flow ◽  
Generation Rate ◽  
Transient Heat Transfer ◽  
Heat Generation Rate ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

Forced convection transient heat transfer coefficients were measured for helium gas and carbon dioxide gas flowing over a twisted heater due to exponentially increasing heat input (Q0exp(t/τ)). The twisted platinum plate with a thickness of 0.1 mm was used as test heater and heated by electric current. The heat generation rate was exponentially increased with a function of Q0exp(t/τ). The gas flow velocities ranged from 1 to 10 m/s, the gas temperatures ranged from 313 to 353 K, and the periods of heat generation rate ranged from 46 ms to 17 s. The surface temperature difference and heat flux increase exponentially as the heat generation rate increases with the exponential function. Transient heat transfer coefficients increase with increasing gas flow velocity. The geometric effect of twisted heater in this study shows an enhancement on the heat transfer coefficient. Empirical correlation for quasi-steady-state heat transfer was obtained based on the experimental data. The data for heat transfer coefficient were compared with those reported in authors’ previous paper.

Detailed Heat Transfer Coefficient Measurements and Thermal Analysis at Engine Conditions of a Pedestal With Fillet Radii

1993 ◽  
Author(s):  
Zuolan Wang ◽  
Peter T. Ireland ◽  
Terry V. Jones
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Element Discretization ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients ◽  
Coefficient Distribution ◽  
Exact Boundary ◽  
Transfer Method

The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modelled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution is compared to that calculated using an area averaged heat transfer coefficient. Metal temperature differences of 90K are predicted across the blade wall.

Detailed Heat Transfer Coefficient Measurements and Thermal Analysis at Engine Conditions of a Pedestal With Fillet Radii

1995 ◽  
Vol 117 (2) ◽  
pp. 290-297 ◽  
Author(s):  
Z. Wang ◽  
P. T. Ireland ◽  
T. V. Jones
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Transfer Coefficients ◽  
Element Discretization ◽  
Turbine Blade Cooling ◽  
Heat Transfer Coefficients ◽  
Coefficient Distribution ◽  
Exact Boundary ◽  
Transfer Method

The heat transfer coefficient over the surface of a pedestal with fillet radii has been measured using thermochromic liquid crystals and the transient heat transfer method. The tests were performed at engine representative Reynolds numbers for a geometry typical of those used in turbine blade cooling systems. The heat conduction process that occurs in the engine was subsequently modeled numerically with a finite element discretization of the solid pedestal. The measured heat transfer coefficients were used to derive the exact boundary conditions applicable to the engine. The temperature field within the pedestal, calculated using the correct heat transfer coefficient distribution, is compared to that calculated using an area-averaged heat transfer coefficient. Metal temperature differences of 90 K are predicted across the blade wall.

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