Internal Flow Heat Transfer Research Articles

Heat Dissipation Analysis and Optimization of Gas Turbine Box Based on Field Synergy Principle

Abstract To improve the heat dissipation and cooling effect of the box and ensure the safe and stable operation of the gas turbine, research on the control and optimization of heat dissipation within the main box of the gas turbine has been carried out. Considering solar radiation, four evaluation indexes, namely, the percentage of the high-temperature zone, the percentage of the high-speed zone, the average field synergy angle, and the temperature inhomogeneity, are proposed to study the internal flow heat transfer characteristics of the gas turbine box, and an optimization scheme for the internal structure of the box-loaded body is proposed by using the orthogonal test method to improve the ventilation and heat dissipation performance. The results show that the percentage of high-temperature zone in the box body is 2.3%, which is mainly distributed near the junction of gas turbine and inlet worm gear; the average field synergy angle in this region is as high as 79.49 deg, and the temperature inhomogeneity reaches 0.98, which makes the heat dissipation and cooling effect poorer and is easy to form a localized high temperature; based on the above research to carry out the optimization of the box body structure, the percentage of high-temperature zone is reduced by 95.7% after optimization, and the average field synergy angle and temperature inhomogeneity are reduced to 72.88 deg and 0.57, respectively, so that the heat dissipation effect has been significantly improved.

Thermal–Solid Interaction Study of Serpentine Nozzle and Analysis on Structural Response Law

The serpentine nozzle effectively suppresses infrared radiation and radar signals from advanced aero-engine exhaust system. However, the extreme operating environment of thermal–solid interaction complicates the heat transfer of the flow inside the serpentine nozzle and the structural response of the nozzle itself. In this study, the internal flow heat transfer and the structural response of the serpentine nozzle were investigated numerically. Further, the parameter influence law of wall thickness was explored. The results show that the mechanism of the thermal-solid interaction is formed through the data transfer of the heat flux and the temperature at the interface between the flow field and structure field. The heat flux distribution of the nozzle under the bending configuration is non-uniform. The upper wall surface at the first bend and the lower wall surface at the second bend exhibit the highest heat flux. In the structural response, the temperature extremes appear on the upper wall at the first bend and the lower wall at the second bend. Subsequently, they shift to the inlet. The stress in the nozzle with a thickness of 3 mm first increases and then decreases, with a maximum stress of 139.43 MPa at t = 51.20 s. For nozzles of different thicknesses, the positions of the maximum stresses all appear at the outlet and the moments concentrate in approximately 50 s. However, with the increase in thickness, the maximum stress of nozzle increases continuously, and the maximum increases by 93% compared with the minimum.

Experimental and numerical evaluation of heat transfer enhancement by internal flow excitation

Many researchers have studied active and passive methods to improve thermal performance and increase heat transfer in internal flows. Various geometries and configurations of turbulators have been proposed to achieve optimal performance in heat exchangers, and these analyses are ongoing. However, limited studies have been conducted on turbulators with equal obstruction inside the tube and turbulator with aerodynamic geometry. In this study, the effect of stimulating the boundary layer of the internal flow is investigated experimentally and numerically on the heat transfer and flow characteristics. For this purpose, a pipe with ring-shaped turbulators and an equal blocking area is used. Air in a range of Reynolds numbers from 6000 to 26,000 is used as the working fluid for the evaluations. According to the results of the study, the ring insert has the most influence in stimulating the flow inside the tube. The highest increase of Nu with the ring, disk, and o-ring is 2.92, 1.8, and 2.19, respectively. The overall performance increases as much as 16.2% at Re = 24,000 by flow excitation.

Internal Flow Heat Transfer Rate for Parallel Heat Exchanger Pipes One Pass of Rice Husk to Air

The research was conducted to analyze the heat transfer rate of heat exchangers from black steel pipes with rice husk as an energy source. This can be used as a recommendation to replace solar energy in the post-harvest drying process, especially for small farmers in rural areas. Research by converting rice husk biomass into heat energy using a heat exchanger of black steel pipes arranged parallel to one air fluid flow. Heat exchanger pipes are placed inside the furnace with dimensions of 50 cm x 50 cm x 80 cm. Forced convection is applied through a fan placed in the drying chamber with a constant speed of 2 m/s. It was found that the ambient temperature increased by an average of 11.70% without adding rice husk mass during the test. The average ambient temperature (Ti) is 305.10 K and ranges from 300.60 to 307.40 K which can be increased to (To) 340.80 K with a range of 317.25 to 366.30 K. This temperature is the out the heat exchanger pipes that can be used for the drying process. The value of the heat transfer rate reached an average of 39.19 W with a range of 18.62-63.19 W. The pattern of distribution of heat transfer rates follows the trend of temperature distribution. It was found that when rice husk turns into charcoal it causes a high heat transfer rate. High heat transfer rates are needed in the drying process of a product so that the required time is shorter and optimal. In addition, rice husk biomass can be used as alternative energy because it is easy to obtain, especially in agricultural areas that grow rice.

Heat Transfer Enhancement of Single-Phase Internal Flows using Shape Optimization and Additively Manufactured Flow Structures

• We optimize the shape of internal fins using generative design. • The optimized fins are additively manufactured from alsi10 mg. • Rigorous measurements and simulations characterize heat transfer performance. • The optimized fins have 65–77% lower thermal resistance than conventional designs. This paper reports heat transfer enhancement of forced internal single-phase flow enabled by additively manufactured internally finned channels. We consider internal liquid coolant flow through a tube with constant heat flux applied to the exterior surface. A genetic algorithm was developed and used to optimize the fin geometry in order to minimize total thermal resistance for laminar flow or convection thermal resistance for turbulent flow. The genetic algorithm sampled more than 500 fin geometries, evaluated thermal resistance, and selected the optimum fin geometry. We selected three designs for experimental testing: a complex fin structure suggested by the genetic algorithm; a straight fin design; and a smooth circular channel as a reference. The devices were made from aluminum silica (AlSi10Mg) using direct metal laser sintering additive manufacturing. The devices were tested using a water ethylene glycol mixture (80:20) over the hydraulic diameter based Reynolds number range of 400 – 18,000, covering both laminar and turbulent flow regimes. Finite element simulations of heat transfer and pressure drop helped to understand and interpret the measurements. Compared to the smooth pipe reference design, the total thermal resistance of the genetically optimized fin design was 77% lower for laminar flow at Re h = 2,000 and 65% lower for turbulent flow at Re h = 10,000. Compared to the straight fin design that is commonly used for enhancing convection heat transfer in internal flows, the total thermal resistance of the genetically optimized fin design was 55% lower for laminar flow at Re h = 2,000 and 29% lower for turbulent flow at Re h = 10,000. We explore the potential design space for different types of heat exchangers by investigating how total heat transfer varies with exterior heat transfer coefficient and channel wall thermal conductivity. This research shows how shape optimization and additive manufacturing can result in devices with improved internal convection heat transfer.

Enhancing deteriorated heat transfer of supercritical nitrogen in a vertical tube with wire matrix insert

In this study, hiTRANTM wire matrix tube insert was used to improve the heat transfer deterioration of supercritical nitrogen (N2) in a heated tube caused by the effects of thermo-physical property variations and buoyancy force. Heat transfer experiments were carried out with N2 flowing upwardly in a vertical circular tube with and without the wire matrix insert under a sequence of experimental conditions including pressures of 35 and 40 bar, mass flow rate of 27.6 and 41.3 g/min and constant heat flux conditions at 6.8, 8.0 and 9.3 kW/m2, respectively. Experimental results show that N2 exhibits similar heat transfer behavior when transiting across the pseudo-critical point as other fluids such as water and CO2. Due to the addition of the wire matrix insert, that intensified the overall fluid mixing in the test tube, the heat transfer performance of N2 was enhanced by more than 42% and up to 2.35 times while the pressure drop increase was negligible compared to the system inlet pressure. Moreover, it has been demonstrated that there might exist an optimum combination of experimental conditions leading to the maximum performance of the wire matrix insert. Furthermore, as the results show, with the Dittus-Boelter correlation and correlations for water and CO2 falling short of fitting the heat transfer data of N2, a heat transfer correlation, exclusively for N2 going through the pseudo-critical point is needed. The findings in this study also reveal that both supercritical N2 internal flow heat transfer and the use of wire matrix insert to enhance the deteriorated heat transfer of supercritical fluids are promising topics and require more significant attentions in future studies.

An Expression for Internal Flow Heat Transfer for Polynomial Wall Temperature Distributions

An Expression for Internal Flow Heat Transfer for Polynomial Wall Temperature Distributions

1778. Temperature measurement and internal flow heat transfer analysis for partially ionized argon: F P Incropera, Rep SU-247-11, ( Stanford Univ, Nuclear Technology Lab, California)

1778. Temperature measurement and internal flow heat transfer analysis for partially ionized argon: F P Incropera, Rep SU-247-11, ( Stanford Univ, Nuclear Technology Lab, California)