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An exhaustive review was undertaken to assemble all available correlations for supercritical CO2 in straight, round tubes of any orientation with special attention paid to how the wildly varying fluid properties near the critical point are handled. The assemblage of correlations, and subsequent discussion, is presented from a historical perspective, starting from pioneering work on the topic in the 1950s to the modern day. Despite the growing sophistication of sCO2 heat transfer correlations, modern correlations are still only generally applicable over a relatively small range of operating conditions, and there has not been a substantial increase in predictive capabilities. Recently, researchers have turned to machine learning as a tool for next-generation heat transfer prediction. An overview of the state-of-the-art of predicting sCO2 heat transfer using machine learning methods, such as artificial neural networks, is also presented.

Shape-memory alloys (SMAs) have been used in many engineering applications because of their shape-memory effect and pseudoelasticity. SMA behavior is well understood under steady and constant temperature and loading conditions, whereas transient and non-ideal conditions effects should be further investigated. In this research, SMA torque tubes are studied for use in thermal management applications as self-regulated actuators responding to a process fluid with changes in temperature, with the goal of improved system efficiency by keeping components at an optimal temperature. When utilized in a thermal management configuration, it is likely that the SMA’s thermal environment will be different than that to which it was trained for, leading to challenges from a modeling standpoint. Process fluid transients lead to temperature fluctuations in the SMA, which may not be negligible in a self-regulated system. Similarly, without perfect insulation of the SMA, a temperature gradient (potentially both along the length and along the thickness) will occur when the SMA is subject to a different boundary condition than what they were trained for (steady isothermal). Empirical efforts have shown that this leads to deviations from expected behavior, challenging the modeling of an open-loop system. This study looks at Nitinol (Nickel-Titanium alloy) rotational actuator tubes, with the goal further understanding the non-ideal conditions for a future model system. The SMA tube was subjected to both insulated and natural convection boundary conditions, with low and high mass flow rates for both heating and cooling cases. The one-dimensional model was compared to experiments as well as a modified thermal model to help improve modeling efforts. Experimental efforts show that a convection boundary leads to temperature gradients, especially at high temperatures and low flow rates. Thermal modeling showed no significant variation along the thickness, mostly due to the small thickness of the

Conventional cylindrical/elliptical pins are one of the most widely used geometries in convection cooling systems and are used in the internal cooling of gas turbine blades and other applications, as they promote better heat transfer at the expense of large pressure losses and unsteadiness in the flow. The need to reduce pressure drop and maintain the heat transfer rates are a pressing requirement for a variety of industries to improve their cooling efficiency. One such prominent field of research is conducted in optimizing the design of pin geometries. In this study, a harbor seal whisker inspired geometry is being studied for their unsteady behavior in an internal cooling channel. The seal whisker geometry consists of streamwise and spanwise undulations which reduce the size of the wake and coherent structures shed from the body as a result of an added component of stream-wise vorticity along the pin surface. Also, the vortex shedding frequency becomes less pronounced, leading to significantly reduced lateral loading on the modified cylinder. Previous computational studies have shown that the bio-mimicked pin geometries break down the wake structure and there is a reduction in development of turbulent intensity downstream of the channel leading to a lower pressure loss. In this experimental study the thermal performance of the bio pins is compared against a conventional elliptical pin for a range of Reynolds numbers. From the results it is found that the bio pins in comparison to the elliptical pin performs on average 13% better in pressure drop at the cost of 4.5% in heat transfer. These findings are important to the gas turbine community as reduced penalties associated with cooling flows directly translate to improved efficiencies.

This project focuses on the reduction of noise and wall heat transfer of afterburners. For this project, the JetCat P250-PRO micro jet turbine was chosen due to its low cost and professional performance characteristics. First, the design for an afterburner to fit the mentioned turbine will be made with various interchangeable low bypass cooling shrouds to test the shrouds effectiveness in noise reduction and heat flow properties. Noise reduction was chosen as the primary research focus because of noise levels of aircraft, especially during takeoff with afterburners, is a serious problem. The secondary focus of heat flow was chosen due to the limiting factor of a lifetime for afterburners is heat. Reducing the heat signature is also a valuable topic, especially for military jet aircraft. Once designs for an afterburner have been chosen, the JetCat P250-PRO will be purchased, and the afterburner sent for manufacturing. Static bench testing will be performed to simulate take-off conditions to evaluate noise reduction and heat flow of each low bypass cooling shroud design

The Temperature Sensitive Paint (TSP) is a widely used method in measuring and visualizing flow separation and heat transfer. Compared to the cost and time consumption needed for methods such as pitot tubes, temperature sensitive paint is a cheaper alternative. Due to high usage in College of Engineering research projects, it was determined that in house fabrication of temperature sensitive paint would reduce time and cost limitations. For initial stages, literature research was performed to determine the recipe of intensity based TSP with luminophore and polymer binder that operated optimum at temperatures from 0-100°C. Europium III thenoyltrifluoroacetonate was determined to be an effective luminophore to create a solvent for turbine cooling and heat transfer research. Standard operating procedure was also created such that it met the environmental and safety risk factors associated with fabrication of paint. Using acrylic glass test piece with existing experimental setup, intensity data were obtained. Experiments resulted in intensity change magnitude and Arrhenius curve similar to commercially available TSP. In addition, in-house TSP was significantly cheaper and less time-consuming. Further research would involve calibration curve and developing a Pressure Sensitive Paint.

The efficiency and power output of the gas turbine is impacted directly by the maximum gas temperature. Cooling technology has therefore played a major role in increasing engine performance. The implementation of this technology allows first stage turbines to produce inlet temperatures that are several hundred Kelvin beyond the melting point of the materials used within them. Effective cooling ensures the safety and the high efficiency of the gas turbine. The turbine blades are commonly cooled using internal cooling, which uses rib turbulators to enhance the rate of heat transfer. In the current study, a model consisting of a rectangular channel with a single parameterized rib geometry was optimized and investigated computationally. The resulting turbulator shapes were significantly different than what is typically found in the literature. Heat transfer enhancement rates of up to 53.6 were observed as compared to the baseline (47.3), with up to 3.3 Pa reduction in pressure drop. The best performing designs were selected on the basis of enhancement in heat transfer and lower pressure drop. These selected designs were 3-D printed and their performance experimentally validated. The tests validate the accuracy of the computational models as well as the feasibility for real world applications.