Thermochromic Liquid Crystal Research Articles

Full Surface Heat Transfer Characteristics of Stator Ventilation Duct of a Turbine Generator

Turbine generators operate with complex cooling systems due to the challenge in controlling the peak temperature of the stator bar caused by Ohm loss, which is unavoidable. Therefore, it is important to characterize and quantify the thermal performance of the cooling system. The focus of the present research is to investigate the heat transfer and pressure loss characteristics of a typical cooling system, the so-called stator ventilation duct. A real scale model was built at its operating conditions for the present study. The direction of cooling air was varied to consider its operation condition, so that there are: (1) outward flow; and (2) inward flow cases. In addition, the effect of (3) cross flow (inward with cross flow case) was also studied. The transient heat transfer method using thermochromic liquid crystals is implemented to measure full surface heat transfer distribution. A series of computational fluid dynamics (CFD) analyses were also conducted to support the observation from the experiment. For the outward flow case, the results suggest that the average Nusselt numbers of the 2nd and 3rd ducts are at maximum 100% and 30% higher, respectively, than the inward flow case. The trend was similar with the effect of cross flow. The CFD results were in good agreement with the experimental data.

Experimental investigation of two-side heat transfer in spacer-filled channels

In Membrane Distillation (MD), spacers support the membranes and promote mixing, thus reducing temperature polarization. Their efficient design requires a knowledge of the distribution of the local heat transfer coefficient h and of its dependence on Reynolds number, spacer geometry and flow-spacer relative orientation. In previous work, we applied Thermochromic Liquid Crystals (TLC) and digital image processing to the measurement of h distributions for different spacer configurations; data were used to validate CFD simulations and select turbulence models. For constructive reasons, the test section allowed only one-side heat transfer, while in most MD configurations (e.g. spiral-wound modules) heat transfer occurs from both sides of the feed water channels. Analytical and numerical solutions show that changing from one-side to two-side heat transfer deeply affects h values. This motivated the design and construction of an improved test section in which a hot channel is sandwiched between two cold channels, and twin cameras and lighting equipment allow the simultaneous acquisition of TLC images on both walls. This paper describes this new test section and the experimental technique, discusses measurement uncertainty, and presents preliminary results.

Revisiting melting heat transfer of nano-enhanced phase change materials (NePCM) in differentially-heated rectangular cavities using thermochromic liquid crystal (TLC) thermography

The melting of nano-enhanced phase change materials (NePCM) in differentially-heated rectangular cavities was revisited by employing a novel indirect visualization method, i.e., the thermochromic liquid crystal (TLC) technique, to track the invisible phase interfaces. Detailed natural convective flow and heat transfer during melting were also predicted by numerical simulations based on the enthalpy-porosity method, which were validated by comparing with the TLC observations. Two height-to-width aspect ratios of the cavity, i.e., 0.8 and 1.25, were studied. Based on the observed evolutions of the phase interface, it was shown that natural convection originating from the upper corner nearby the phase interface causes the difference in melting patterns between the upper and lower parts of the cavity. The decelerated melting in the presence of NePCM samples with higher loadings (and hence much greater viscosity) was confirmed intuitively by the more vertical and flatten phase interfaces captured by TLC, indicating that heat conduction becomes the dominant mode of heat transfer during melting as a result of the significantly deteriorated natural convection effect. Moreover, when the cavity becoming more slender, the advantage of increased thermal conductivity could be more sufficiently taken because the shorter characteristic length inherently lowers the contribution of natural convection.

Thermochromic luminescence in dual-dye-doped liquid crystal mixture induced by varying the energy transfer rate

Chromism in luminescent materials have attracted increasing interest for their unique feature of controllable luminescent colours and their applicability in various fields. Here we report a novel thermochromic luminescent liquid crystals (LC) system containing two luminescent dyes which do not have chromic properties themselves. The luminescent colours of the dual dye-LC mixture can be reversibly and continuously controlled between orange and blue by applying thermal stimuli; the relative intensity ratio between the two luminescent peaks is continuously controlled. This unprecedented phenomenon originates mainly from varying efficiency of the Förster energy transfer rates between two dye dopants depending on the phases of host LCs. The energy transfer rate is the highest in the crystal phase, giving rise to orange emission, and it is lowest in the isotropic state, producing blue emission. In the middle phases (nematic and smectic), mixed colours of these two colours are obtained. The proposed methodology, which takes advantage of controllable energy transfer rates, can greatly broaden the range of affordable dye materials for chromic luminescence systems because common fluorescent dyes can be used instead of special chromic compounds.

On the application of neural networks for temperature field measurements using thermochromic liquid crystals

This study presents an investigation regarding the applicability of neural networks for temperature measurements using thermochromic liquid crystals (TLCs) and discusses advantages as well as disadvantages of common calibration approaches. For the characterization of the measurement technique, the dependency of the color of the TLCs on the temperature as well as on the observation angle and, therefore, on the position within the field of view of a color camera is analyzed in detail. In order to consider the influence of the position within the field of view on the color, neural networks are applied for the calibration of the temperature measurements. In particular, the focus of this study is on analysis of the error of temperature measurement for different network configurations as well as training methods, yielding a mean absolute deviation and a mean standard deviation in the range of 0.1 K for instantaneous measurements. On the basis of a comparison of this standard deviation to that of two further calibration approaches, it is shown that neural networks are suited for temperature measurements via the color of TLCs. Finally, the applicability of this measurement technique is illustrated at an exemplary temperature measurement in a horizontal plane of a Rayleigh–Bénard cell with large aspect ratio, which clearly shows the emergence of convective flow patterns by means of the temperature field.Graphic abstract

Simultaneous optical measurement of temperature and velocity fields in solidifying liquids

We introduce a complex image processing scheme for the simultaneous application of liquid crystal thermometry (LCT), in addition to the previously established method in Anders et al. (Exp Fluids 60(4):68, 2019. https://doi.org/10.1007/s00348-019-2703-8) for particle tracking velocimetry and particle image velocimetry. This scheme was developed for an experimental study on the double-diffusive convection in an aqueous ammonium chloride solution NH4Cl(aq) during crystallization. The use of thermochromic liquid crystals (TLC) enables to visualize the flow and temperature field simultaneously. We present a color interpolation method that enhances the accuracy of the LCT by yielding RGB images only representative of the TLC’s coloration. An artificial neural network (ANN) which processes RGB triplets and spatial color dependencies transforms these images into temperature fields. The combination of the ANN system and a corresponding calibration procedure enhances the accuracy and measurable temperature range of the LCT compared to state-of-the-art procedures. By using the here established measurement scheme, quantitative global studies of the mutual influence between solidification and convection are enabled and exemplary results are presented.Graphic abstract

A Vision-Based Soft Somatosensory System for Distributed Pressure and Temperature Sensing

Emulating a human-like somatosensory system in instruments such as robotic hands and surgical grippers has the potential to revolutionize these domains. Using a combination of different sensing modalities is problematic due to the limited space and incompatibility of these sensing principles. Therefore, in contrast to the natural world, it is currently difficult to concurrently measure the force, geometry, and temperature of contact in conventional tactile sensing. To this end, here we present a soft multifunctional tactile sensing principle. The temperature is estimated using a thermochromic liquid crystal ink layer which exhibits colour variation under temperature change. The shape and force of contact is estimated through the 3D reconstruction of a deformed soft silicone surface. Our experiments have demonstrated high accuracy in all three modalities, which can be measured at the same time. The resolution of the distributed force and temperature sensing was found to be 0.7N and 0.4 °C respectively.

A novel method to detect hot spots and estimate strengths of discrete heat sources using liquid crystal thermography

This paper reports the results of an investigation to solve the inverse problem of estimating the strengths of different strip heat sources embedded in a flat plate under laminar steady-state forced convection and by way of this propose a novel method to detect hot spots from remote measurements. A Bayesian framework is adopted to infer the strength of the heat sources from thermochromic liquid crystal (TLC) temperature measurements. This framework consists of the forward model, the measured data, and the inverse model. The forward model simulates the conjugate three-dimensional heat transfer problem with the specified thermophysical properties, and the boundary conditions. The input data for the forward model is a combination of different heat source strengths, and the output is temperature data obtained at the bottom surface of the cork. The input-output data of the numerical simulations are used to build a proxy or surrogate (artificial neural network, ANN) that acts as a replacement for the actual forward model to increase the computational speed and decrease the computational time while solving the inverse problem. Calibrated thermochromic liquid crystal sheets are attached at the bottom surface of the cork for mapping the temperature data, so that the top surface where the convection takes place is undisturbed. In the inverse model, Bayesian statistics, along with the Gibbs sampling algorithm is adopted for analyzing the posterior distribution to estimate the mean, the maximum a posteriori and the standard deviation of the heat source strengths. Validation and robustness of the inverse methodology have been examined. The estimated heat source values are input to the forward model to determine the hot spot temperatures on the flat plate. This is a key spin-off from the present study, wherein based on temperature measurements at a convenient place, the hot spot in a geometry can be remotely ‘estimated.’ A comparison of the simulated and the measured values of the hot spot temperatures is reported for different flow Reynolds numbers.

Visualization of heat transfer characteristics using thermochromic liquid crystal temperature measurements in channels with inclined and transverse twisted-baffles

Channels with ribs/baffles are widely applied in thermal engineering applications such as heat exchangers, solar water/air heaters and gas turbine cooling. In the present work, inclined and transverse twisted-baffles (I-TBs/T-TBs) are developed for heat transfer enhancement in a channel. The effects of Reynolds number (Re = 4000, 8000, 12,000, 16,000 and 20,000) roughness pitch ratios (p/w = 4.0, 6.0, 8.0, 10.0 and 12.0) and baffle twist ratios (y/w = 2.0, 3.0, 4.0 and 5.0 corresponding to twisted-baffle loop numbers (N) of 5, 7, 8 and 9) were investigated using air (Prandtl number, Pr = 0.7) as a working fluid. Heat transfer behavior was examined using thermochromic liquid crystal temperature measurements. Typical transverse and inclined baffles were also tested for comparison. Heat transfer, flow friction and thermal performance are reported in terms of Nusselt numbers (Nu), Nusselt number ratios (Nu/Nus), friction factors (f), friction factor ratios (f/fs) and thermal performance indices (η). Experimental results reveal that under most conditions examined, I-TBs show better heat transfer, lower frictional losses and higher thermal performance than TBs, IBs and T-TBs. For I-TBs, maximum heat transfer and thermal performance are obtained at a moderate pitch ratio (p/w = 6.0). However, in cases of T-TBs, heat transfer and thermal performance monotonically increase with a decreasing pitch ratio. Friction losses caused by both I-TBs and T-TBs decrease considerably with increasing pitch ratio. For I-TBs, heat transfer and thermal performance monotonically increase with increasing twist ratios. However, for T-TBs, maximum heat transfer and thermal performance are obtained at y/w = 3.0. Over the present studied range, a channel with I-TBs having optimal geometry (p/w = 6.0 and y/w = 5.0) yields maximum thermal performance indices, as high as 1.98, which is greater than the maximum values yielded by channels with T-TBs, TBs, IBs, and smooth channels, by around 74.1%, 98%, 52.5% and 98.3%.

A Novel Indirect Visualization Method for Studying the Melting Heat Transfer of Nano-Enhanced Phase Change Materials Using Thermochromic Liquid Crystal Thermography

Abstract In order to give more sights into the melting (and solidification) heat transfer processes of nano-enhanced phase change material (NePCM) with invisible phase interfaces, a novel indirect method for tracking the phase interface by thermochromic liquid crystal (TLC) thermography is proposed. As an example case to demonstrate the applicability of the proposed method, the classical problem of melting heat transfer in a differentially heated rectangular cavity was revisited in the presence of NePCM of various loadings. A narrowband TLC was selected and calibrated carefully to build the hue–temperature relationship prior to being applied in the melting experiments. For validation purpose, the case of an unloaded NePCM, with a clear visible phase interface, was tested via combined direct and indirect observations. It was shown that this TLC method can easily and accurately capture the dynamic motions of the phase interface during melting. Based on the shape evolutions of the phase interface, it was concluded that for the NePCM sample with a higher loading (and hence a much greater viscosity), heat conduction becomes the dominant mode of heat transfer during melting as a result of the significantly deteriorated natural convection effect. This gives an intuitive confirmation of the hypothesis made in previous studies that were conducted using volume-average-based indirect methods.

Detailed investigation of staggered jet impingement array cooling performance with cubic micro pin fin roughened target plate

This paper studies in detail the heat transfer performance of a staggered arranged jet array impinging on a cubic micro pin fin roughened target plate in a generic system, on the purpose of extending the knowledge of heat transfer enhancement in a staggered impingement array. This subject has only rarely been studied in literature. Experiments are conducted with the transient thermochromic liquid crystal (TLC) method. Pressure taps placed along the test facility are used for pressure loss evaluation. The rib behavior for different jet Reynolds numbers (Re = 15,000–35,000), different cross-flow schemes (maximum, medium and minimum cross-flow) and different separation distances (H/D = 3–5) is studied in detail, to determine a configuration with the best thermal performance. A steady state Reynolds-Averaged Navier-Stokes (RANS) method using the Shear Stress Transport (SST) turbulence model is used for a numerical simulation, to help to understand the experimental phenomena. The rib performance is compared to a previously studied inline impinging case, to learn the effect of jet arrangement. The work can be a basis for the optimization of jet arrangements for impingement cooling in turbomachinery applications.

Experimental investigation on the effects of hole pitch and blowing ratio on the leading edge region film cooling of a rotating twist turbine blade

An experimental investigation has been performed to study the effects of the hole pitch and the blowing ratio on the leading edge region film cooling performance of a twist turbine blade with three rows of film holes under rotating conditions. The experiments were accomplished in a test facility with one-stage turbine using the thermochromic liquid crystal (TLC) technique. All tests were made at a rotating speed of 574 r/min with the average blowing ratio ranging from 0.5 to 2.0. The Reynolds number based on the mainstream velocity of the turbine outlet and the rotor blade chord length was fixed at 6.4 × 104.CO2 was used to obtain the coolant-to-mainstream density ratio of 1.56. The hole pitches tested were p=2.5d,p=3.75d and p=5d, respectively. The results show that both the hole pitch and the blowing ratio play an integral role in determining the film cooling effectiveness distributions on the leading edge. Regardless of the hole pitch, the spanwise average film cooling effectiveness increases monotonously with the increase of blowing ratio on the leading edge region. For all blowing ratio cases, the spanwise average effectiveness has a decreasing trend as the hole pitch increases. When the bowing ratio is constant, the difference between the spanwise average film cooling effectiveness value obtained in the region of −4.3<x/d<0 and the region of 0 < x/d < 3.75 has a decreasing trend as the hole pitch increases. For all hole pitch cases, the area average film cooling effectiveness increases monotonously as the blowing ratio increases. For all blowing ratio cases, the area average film cooling effectiveness decreases monotonously as the hole pitch increases. However, the reduction is not always linear to the hole pitch change. When the coolant jet mass flow rate is constant, the p=2.5d case provides a higher level of the area average film cooling effectiveness than the p=3.75d and 5d cases.

Influence of obstacles on the wall heat transfer for 2D and 3D helically ribbed pipes

Obstacles placed on the inner walls of pipes lead to flow separation and subsequent reattachment with an overall beneficial effect on the local heat transfer. In this work, the effects of both a continuous and a discontinuous helicoidal turbulator on the local heat transfer are investigated and compared for Reynolds numbers in the range from 20,000 to 80,000. Both turbulators are cylindrical helixes with constant angle and fixed direction. The continuous geometry has a pitch-to-diameter-ratio (p/D) equal to 11, an inclination angle of 80° and a uniform obstacle height-to-diameter-ratio (e/D) equal to 3.6%. The discontinuous geometry is equivalent to the continuous one except that it has a varying obstacle height throughout the helix. Steady-state heat transfer measurements are carried out by means of Liquid Crystals Thermography (LCT). A recently developed calibration method for the narrow-band Thermochromic Liquid Crystals (TLCs) is successfully modified to lower the angular effects on the measurement uncertainty. The local wall heat transfer rates and the temperature distributions are strongly influenced by the flow reattachment and thus by the geometry of the investigated turbulators. Compared to a smooth pipe at the same Reynolds number, the continuous and the discontinuous turbulator increase the average Nusselt number by factors of approximately 1.8 and 1.5 respectively. These heat transfer measurements with respective uncertainties are meant to be a valuable dataset for the validation of Large Eddy Simulations (LES) of turbulent flows in pipes equipped with turbulators.

Effect of pin inclination angle on flow and heat transfer characteristics for a row of pins in a flow channel

The aim of this research was to study flow and heat transfer characteristics with a row of inclined pins in a rectangular channel. The cylindrical pins of diameter D = 10 mm were mounted on the heat transfer surface in spanwise direction of the channel. The pin-to-pin distance was fixed at S = 2D. Two of pin heights H were studied, namely short pins or long pins with H = 2D or H = 3.2D, respectively. The effects of pin inclination angle were investigated for θ=30o, 45o, 60o, 90o, 120o, 135o, and 150o in the range of Reynolds number from 14,000 to 32,860. The local temperature on endwall surface was measured using a thermochromic liquid crystal sheet coupled with image processing. Numerical simulations were used to obtain three-dimensional flow fields and heat transfer rates on pin surfaces and endwall surface. Results for the case H/D = 2 show that pins inclined by θ=30o, 45o and 60o can enhance heat transfer downstream of the pin row, from the baseline case of pins with θ=90o. The heat transfer was improved by a pair of counter-rotating vortices near the heat transfer surface. These vortices induced the main flow to attach on the heat transfer surface. The pin inclinations θ=120o and 135o somewhat improved heat transfer behind the pins. However, the inclination θ=150o gave the lowest heat transfer rate on the endwall surface. The heat transfer on endwall surface with H/D = 3.2 was poorer than with H/D = 2 because the counter-rotating vortices did not reach the heat transfer surface. The inclination θ=30o with H/D = 2 gave the best thermal performance. The local Nusselt number on the rear side of pin surfaces with H/D = 3.2 and inclinations θ=30o, 120o, 135o and 150o tended to increase from the case H/D = 2, due to a jet-like flow attachment on the pin surfaces. However, the local Nusselt number on pin surfaces with H/D = 3.2 and inclinations θ=45o and 60o tended to be lesser than with H/D = 2, due flow separation downstream far from the pins.

An experimental heat transfer investigation of an impingement jet array with turbulators on both target plate and impingement plate

Impingement cooling has been widely used for high heat transfer demanded applications, and numerous attempts have been made to improve its thermal efficiency. This study presents experimental heat transfer results of an innovative rib configuration combined by V-ribs on the impingement plate and detached ribs on the target plate for an inline impingement system. The combined ribs are expected to redirect the spent air in the impingement channel, modify the cross-flow field and thus, improve the heat transfer performance. The transient thermochromic liquid crystal (TLC) method is employed for detailed heat transfer measurements. Pressure taps set along the test rig are used to evaluate the pressure loss. In addition, the thickness and roughness effect of the sprayed coating layers (TLC and black paint) is experimentally studied. The detached rib configuration is determined based on a geometrical parameter study on the rib position. The effect of the combined ribs is investigated for different jet Reynolds numbers and different separation distances. The results show that the combined ribs induce a Nusselt number increase for all cases in the studied range, with a negligible extra pressure loss. A relatively thin and smooth sprayed coating is employed, to ensure the measurement accuracy.

A large thermal turbulent Taylor-Couette (THETACO) facility for investigation of turbulence induced by simultaneous action of rotation and radial temperature gradient.

A thermal turbulent Taylor-Couette facility has been designed to investigate turbulent flows generated by differential rotation and radial temperature gradient. It consists of a cylindrical annulus with a rotating inner cylinder and a fixed outer cylinder. The electric heating system is installed inside the inner cylinder, and the annulus is immersed in a large cylindrical container filled with cooling fluid. Temperature regulators independently control the temperature of the inner surface of the inner cylinder and that of the cooling fluid. The facility allows us to reach values of the Reynolds number (Re ∼ 5 × 105) and of the Rayleigh number (Ra ∼ 3 × 106) for water as the working fluid. The facility provides torque measurements, a full optical access at the side and from the bottom for velocity measurements using particle image velocimetry (2D, stereoscopic, and tomographic). Temperature measurements in the flow can be performed by thermochromic liquid crystals or laser induced fluorescence.

Flow and heat transfer characters in the integral internal cooling channel of a turbine blade

A scaled model of the integral internal cooling channel of a turbine blade was established for the experimental investigation. The model was made by Perspex for its transparency so that the thermochromic liquid crystal measurement could be used easily. The cooling channel is composed of 3 legs of ribbed channels. Rib with angle 45° was settled in both pressure side and suction side, which forms a cross-rib structure. Three legs were connected by two 180° turns. The main inlet and two addition inlets were arranged in the root of the model channel. Two discharge outlets were located in the tip. A row of outlet holes was distributed along the trailing edge. The channel area gradually decreases along the blade height direction, while bending and torsion occur because of the blade airfoil shape. The aspect shapes and connection methods of the channel were kept in accordance with the real blade. The inlet Reynolds number is from 10000 to 32000. Five outlet discharge ratios were alternated in this investigation. The detailed heat transfer distributions, both in the pressure side and suction side, were measured by transient liquid crystal technic. The characters of heat transfer distribution and pressure drop along the channel were displayed. The effects of flow discharge ratio on heat transfer and pressure coefficient were also described.

Experimental investigation of the heat transfer characteristics and thermal performance inside a ribbed serpentine channel during rotational effects

The effect of the speed of rotation on heat transfer characteristics inside a ribbed serpentine channel was studied experimentally. In this study, ribs with square cross sections were located on the leading side (LS) and trailing side (TS) of the serpentine channel wall. The serpentine channel had an aspect ratio (AR) of 1.0 and a hydraulic diameter (Dh) of 50 mm. The rib pitch-to-height ratio (p/e), the rib height-to-hydraulic diameter ratio (e/Dh), the channel length-to-hydraulic diameter ratio (L/Dh), and radius ratio of the channel (r/Dh) were fixed at 10, 0.1, 8, and 5, respectively. There were four different types of geometries for the present study, viz. a smooth wall, a 90° ribbed wall, a 60° V-ribbed wall, and a 60° V-broken ribbed wall. The Reynolds number (Re) based on the hydraulic diameter of the channel was constant at 10,000, and the rotation numbers (Ro) were varied in the range from 0.0 to 0.30. The heat transfer coefficients in a serpentine channel were measured experimentally using the steady thermochromic liquid crystals (TLC) technique. In addition, the friction factor and the thermal-hydraulic performance were measured for each case. The results showed that the ribbed wall attained better regional heat transfer performances than the smooth wall for both stationary and rotating conditions at almost all locations. The heat transfer in the first pass was the highest on the TS wall, followed by the LS wall. A similar trend also occurred in the turn region. However, in the second pass, the heat transfer was the highest for the LS wall, followed by the TS wall. Due to the rotation, the Coriolis force acted on the TS wall in the first pass and on the LS wall in the second pass, while the direction of the centrifugal force was aligned with the radius of the rotation. As a result, the average heat transfer in the first pass was larger than it was in the second pass. The maximum average heat transfer and thermal performance inside a serpentine channel occurred in the case when there was a broken V-60° rib, i.e., it was increased up to about 2.1–2.4 in the range of Ro = 0.0–0.15. The thermal performance factor for the broken V-60° rib at Ro = 0.2–0.3 gained about 2.4–2.6, which was near the case of the V-60° ribs.

Effect of film hole geometry and blowing ratio on film cooling performance

In this paper, four kinds of film holes (cylindrical hole, fan-shaped hole, anti-vortex hole and sister hole) are experimentally and numerically studied to investigate the effect of hole geometry and blowing ratio on film cooling performance and flow structure. The blowing ratio ranges from 0.3 to 2.0, the density ratio is 1.065 and the mainstream Reynolds number is 38664. In the experiment, the steady-state Thermochromic Liquid Crystal (TLC) is applied to obtain the film cooling effectiveness. The numerical investigation is performed to analyze the flow structure and counter-rotating vortex pair (CRVP) intensity. Experimental results show that the sister hole demonstrates best cooling performance with blowing ratio from 0.3 to 1.5. The sister hole provides better cooling performance than anti-vortex hole. While the fan-shaped hole performs better at high blowing ratios and it achieves best at blowing ratio of 2.0. Numerical simulation indicates that for the anti-vortex hole and sister hole, the application of side holes can decrease the main hole CRVP intensity and weaken the mixing between the main hole CRVP and mainstream, which increases cooling performance. The coolant interaction between side holes and main hole of the sister hole is stronger than that of the anti-vortex hole.

Detailed Heat Transfer Coefficient Measurements on a Scaled Realistic Turbine Blade Internal Cooling System

AbstractA realistic internal cooling system of a turbine blade includes both ribs and pin-fins inside the passages to enhance the heat transfer. However, the majority studies in the open literature assessing the heat transfer characteristics on a simplified cooling model by examining ribbed-roughen passages and pin-finned passage separately. This work presents the high-resolution heat transfer coefficients of a scaled realistic turbine blade internal cooling design. The cooling system, using a 3D-printed plastic material, consists of an S-shaped inlet, four serpentine passages (three U-bends) of variable aspect ratio, and the trailing edge ejection. Angled ribs are implemented inside the passages and the elongated fins and pins are used near the trailing edge. Two dust holes are realized on the blade tip, the injections are individually controlled to reflect the realistic coolant flowrate variation inside the entire internal cooling system. The tests are conducted at two Reynolds number, 45,000 and 60,000 based on the hydraulic diameter of the inlet passage. Transient heat transfer technique using thermochromic liquid crystal is applied to obtain the detailed heat transfer characteristic inside the cooling channel. The local and averaged Nusselt numbers are also compared with the correlations in the open literature. This paper provides gas turbine designers the difference of local heat transfer distributions between the realistic and simplified internal cooling designs.