Thermal Design Analysis Research Articles

Spectral Heat Transfer Coefficient (SHTC) for Thermal Design Analysis - Part 2: Leveraging Diabatic Wall Conditioning for Nonlinear Regime

Abstract There are two main issues of interest in the context of Newton's law of cooling as applied to turbine aerothermal designs. First, in a linear aerothermal regime, how do we deal with a non-isothermal wall where the wall surface temperature is non-uniform? Secondly, what can we do if an aerothermal system becomes nonlinear, manifested by qualitatively large changes of the flow field affected by heat transfer? In Part 1, a new spectral heat transfer coefficient (SHTC) method has been introduced for blade thermal analysis subject to non-isothermal walls in a linear aerothermal regime. Part 2 is devoted to address the issue of nonlinearity when the temperature field actively interacts with the velocity field as in many practical aerothermal problems. It is noted that the conventional approach rests heavily on an adiabatic state, so much so that its working range becomes overly restrictive. To move away from the adiabatic state, we take advantage of smooth (‘differentiable’) heat flux-wall temperature relation afforded by strong solid diffusion. A local linearization can be utilized by decomposing a full thermal variable into a nonlinear base as the reference and a locally linear perturbation. This split enables us to directly compute a nonlinear base as well as to carry out a linearized scaling with the SHTC (HTC) on top of the selected nonlinear aerothermal base state. The results of several computational case studies clearly and consistently support the validity and effectiveness of the present approach and method implementation.

Thermal design of focal plane assembly of wavefront camera for exoplanet imaging corona module

The focal plane assembly of wavefront camera is the key imaging device of wavefront detection camera and the key load of the exoplanet imaging coronagraph module. In order to ensure the imaging quality and reduce the dark current and thermal noise, it is necessary to effectively dissipate the heat of the focal plane CCD and other high-power electronic devices to ensure the working performance and reliability of the focal plane assembly. Based on the limited space and cooling resources, this paper adopts the flexible graphene heat conducting cable and grooved heat pipes, and carries out detailed thermal design and thermal analysis of its cooling path. The finite element model is established by thermal analysis software and thermal simulation is carried out. in that steady state, the work temperature range of the CCD chip is -12.8∼-10.9°C, which meets the temperature control index, and the work temperatures of other components are also within the design requirements, which indicate that the thermal design scheme is reasonable and feasible, and meets the task requirements.

Concepts of heat dissipation of a disposal canister and its computational analysis

The stability of engineered barriers in high-level radioactive waste disposal systems can be influenced by the decay heat generated by the waste. This study focuses on the thermal analysis of various canister designs to effectively lower the maximum temperature of the engineered barrier. A numerical model was developed and employed to investigate the heat dissipation potential of copper rings placed across the buffer. Various canister designs incorporating copper rings were presented, and numerical analysis was performed to identify the design with the most significant temperature reduction effect. The results confirmed that the temperature of the buffer material was effectively lowered with an increase in the number of copper rings penetrating the buffer. Parametric studies were also conducted to analyze the impact of technical gaps, copper thickness, and collar height on the temperature reduction. The numerical model revealed that the presence of gaps between the components of the engineered barrier significantly increased the buffer temperature. Furthermore, the reduction in buffer temperature varied depending on the location of the gap and collar. The methods proposed in this study for reducing the buffer temperature hold promise for contributing to cost reduction in radioactive waste disposal.

Thermal performance and design analysis of U-tube based vacuum tube solar collectors with and without phase change material for constant hot water generation

Solar water heaters are the most promising technology, and they can be effectively used for hot water generation in cold climatic conditions. The moto of this research is the design and development of two compact vacuum tube solar collectors (VTSCs): (i) modified copper finned U-tube based VTSC filled with PEG6000 as a phase change material (PCM). However, it integrates heat transmission and storage capabilities into a unit (ii) conventional U-tube inserted VTSC without PCM. The developed VTSC with PCM was operated under dual (simultaneous and mid-day charging) modes, and their performance was compared with the conventional system at various flow rates. This study explored the design analysis, working principle, and the outcome of fixed mass flow rates on the system's thermal output. The results display that the daily energy output of the developed collector with PCM is 81.54–89.74 % for simultaneous mode and 78.21–86.52 % for mid-day charging mode. Whereas the daily energy output of conventional solar collector without PCM was 69.31–75.54 % for set mass flow rates. The highest thermal efficiency was around 89.74 % for U-tube inserted VTSC with PCM (simultaneous mode) at a high flow rate (30 LPH). The global heat transfer coefficient (UL) was maximum at a low mass flow rate (10 LPH) for conventional system without PCM, followed by mid-day charging and simultaneously operated VTSC with PCM. After comparing both systems, it is found that using PCM in VTSC improves the daily energy efficiency and increases the operating time for 3–4 more hours than conventional system. This analysis revealed that the developed U-tube inserted VTSC with PCM can substantially supply the hot water demand for domestic applications constantly at night/off sunshine hours.

Study of pyrolitic graphite sheet potential as thermal passive element in CubeSats

CubeSats have become in the last decade ideal platforms to demonstrate new technology or to facilitate access to space due to the reduction in development time and costs. However, one of the main problems is the short lifetime of their missions. In many cases, it is due to the lack of correct thermal design and thermal analysis or even no thermal analysis at all. Specifically, the solar panel thermal design affects the global satellite behavior as the electric power supplied by the solar cells depends on their temperature. Typically, the solar panel thermal design is reduced to use its backside as a radiator (if they are deployable). This paper presents a new thermal solar panel assembly using an intermediate layer of PGS (Pyrolitic Graphite Sheet), which at room temperature has a thermal conductivity 3.8 times greater than pure copper, between the solar cells and the solar panel support, in order to homogenize the solar cells temperature. The new design is compared to the standard design developing the GMM (Geometrical Mathematical Model) and TMM (Thermal Mathematical Model) of a CubeSat 6U located in LEO using ESATAN-TMS. The proposed design gets a reduction of up to 5 °C in the temperature variation of the solar cells.

Thermal design analysis for SuperTruck II lithium-titanate battery pack

This paper presents a systematic thermal management analysis for a new lithium-titanate-oxide battery pack to be installed in a SuperTruck II, Class 8 hybrid truck. The authors investigate the feasibility of mounting the battery pack inside the vehicle and air-cooling it with fans supplying conditioned air from the cabin. Moreover, the cells within each module are to be immersed in a heat-transfer fluid to improve temperature homogeneity. A multi-stage thermal analysis is performed to ensure adequate thermal regulation of the battery under the proposed design, considering installation and operational constraints. The authors perform thermal and electrical characterization tests on a single cell. Results inform the development of computational fluid dynamics models of the cells, modules, and pack. Module-level analysis shows that the cell temperatures can be maintained below their upper operational limit of 55 °C with module wall-to-air heat transfer coefficients between 10 and 20 Wm−2K−1. Pack-level analysis of distinct configurations determines effective airflow paths for adequate heat transfer and delivers a final battery pack design that achieves sufficient cooling and temperature uniformity. A reduced-order electrothermal model is developed to rapidly predict the transient battery performance and to develop a temperature control strategy.

Improved Radiation Heat Transfer Model in RELAP5 for Compact Fuel Rod Bundles by the Absorption Factor Modification

Simulations of radiation heat transfer in fuel rod bundles are necessary for the thermal hydraulic design and safety analysis of open lattice gas-cooled reactors, which always operate at high temperatures. To save the computational costs, existing radiation models in system codes such as RELAP5 commonly assume each fuel rod to own the uniform radiosity over the rod surface. Previous research studies have indicated that the uniform radiosity assumption could overestimate the heat transfer flux and under-predict the maximum fuel rod temperature, and the anisotropic correction was tried by dealing with non-uniform reflected radiation. To better model the non-uniform radiosity effect, the Gehart’s method based on the non-uniform absorbed radiation is introduced in this study. By dividing the surface of each rod into six segments, the one-sixth rod view factors are derived in specific rod and near wall sections to generate the segment-to-segment absorption factors. By summarizing those segment-to-segment absorption factors, the rod-to-rod and rod-to-wall absorption factors are modified and implemented into RELAP5 to improve the radiation heat transfer model. The two-dimension radiation heat transfer problem in the nuclear fuel rod bundle is simulated in FLUENT as the benchmark and in RELAP5 for comparison. Fuel rod bundles in hexagonal arrays were investigated with various surface emissivity and pitch-to-diameter ratios (p/d). The simulations indicated that the method of rod segment division and absorption factor modification could reflect the non-uniform radiosity, and the results were related to the values of p/d and surface emissivity. The modified radiation heat transfer model in RELAP5 validated that the deviations of the maximum temperature were reduced from around 20% to 1%,3%,8% for p/d = 1.1, 1.2, and 1.3, respectively. Rod bundles with larger p/d required more radiative rods in the analyses of absorption factor modifications. The present radiation heat transfer model should be studied and tested in three-dimension cases to further prove that it is appropriate for the nuclear rod bundles.

Prediction of thermohydraulics in shell side of CAP1400 steam generator by two-fluid porous media model

Three-dimensional thermohydraulics in the shell side of the u-tube steam generator are essential for the thermal design and tube flow-induced vibration analysis, which are crucial for the equipment economy and integrity. In this work, the Eulerian two-fluid framework along with porous media model was employed to predict the thermal-hydraulic parameters in the shell side of the CAP1400 steam generator. The two-phase flow in the shell side was treated as flow in porous media with additional momentum and energy source terms for each phase to consider the effects of structure resistance and primary-to-shell heat transfer. The primary side was simplified by the multi-channel model with 16 equivalent tubes. The distributions of thermal-hydraulic parameters for each phase and the mixture phase were obtained. High non-uniformity can be observed for the flow and heat transfer parameters. The ratio between heat released in the hot side and cold side was as large as 2.7. The crossflow energy related to the flow-induced vibration was also derived to find the possible location of tube damage. The most probable location for a potential tube rupture locates at approximate 0.4 rad in the hot side.

Energy-efficient design of dual circulating fluidized bed system for CCUS by multi-tube configuration with junctions

Via temperature swing adsorption, a dual circulating fluidized bed reactor can capture CO2 through a continuous process, but controlling the temperature of the reactor at a large scale is difficult due to the non-linearity hydrodynamics and heat transfer in the scaled-up two-phase flow. In the present study, an energy-efficient design of a circulating fluidized bed reactor was investigated. A preliminary design based on numerical simulation was associated with poor heat transfer of single- and multi-tube reactors. To enhance the heat transfer performance, an innovative multi-tube reactor with junctions was proposed. The junctions improved mixing among the tubes and resolved the heat transfer imbalance between the tubes. The heat transfer coefficient of the multi-tube reactor with junctions was about 12 times larger than that of the multi-tube reactor without junctions. An experimental facility was constructed, and the reactor design was verified. Finally, thermal design analysis is performed to evaluate the design effectiveness in terms of the thermal performance of the reactor capable of continuous CO2 capture. The results showed that the multi-tube reactor with junctions has a large thermal margin and is thus a robust and flexible design applicable to thermochemical process.

Analysis and Solution to Abnormity of DNBR Indicated by ICIS of a WWER Unit

To analyze the reason of difference between the departure from nucleate boling ratio (DNBR) indicated by the upper-level software and lower-level software of the in-core instrumentation system (ICIS) at a certain water-cooled water-moderated power reactor (WWER) unit under its first thermal test during raising power, an investigation was made on the critical heat flux (CHF) correlations adopted in the reactor thermal and hydraulic design and accident analysis of WWER unit. On the above basis, the reason behind the difference was found to be the use of different CHF correlations by the upper-level software and the lower-level software of ICIS through the simulation of thermal tests under 50%, 75% and 90% power level using WWER accident analysis code DINAMIKA-97, calculation of DNBRs and comparison with the ones measured in thermal-hydraulic tests. DNBR under 100% power level was predicted, which coincided with the measured DNBR very well and proved the correctness of the guess further. It is suggested that the CHF correlations adopted by the upper-level software and the lower-level software shall be modified to the same conservative CHF correlation to get a conservative DNBR.

Co-designing cryogenic system with pulse tube cryocooler and loop heat pipe for infrared energy management

• The first co-designing cryogenic system in the world considering cryogenic acquisition and thermal transport is presented. • Redundancy consideration of two cryocoolers and cryogenic loop heat pipes for engineering application was set in the system. • Several thermal insulation measures were adopted to increasing the conversion efficiency for infrared energy management. Cryogenic system is important for the infrared detectors, which can increase the ratio of signal-to-noise at low temperature. Long lifetime, high efficiency mechanical cryocoolers and two-phase heat pipes can reduce the energy consumption of the spacecraft and ensure a low weight. A co-designing cryogenic system consisting of two pulse tube cryocoolers (PTCs) and two neon cryogenic loop heat pipes (CLHPs) operating at temperature around 35 K is designed, manufactured, and tested in the present work. A novel integrated multifunctional heat exchanger is proposed to couple the heat exchange between the cold head of PTC and the condenser of CLHP. To our best knowledge, it is the first time to couple these two technologies directly for space application. The thermal design and efficiency analysis of this cryogenic system are presented, which optimize both the structural layout and insulation to reduce the heat load from surroundings. The thermal performance of the PTCs is ground tested and the co-designing cryogenic system is integrated in a vacuum chamber. The no-load temperatures of the PTCs are 25.3 K and 25.7 K, respectively, while both of the cooling capacities are over 2 W@35 K with the input power of 250 W AC. Meanwhile, the thermal performance of supercritical startup and steady-state operation are tested, and the results are discussed and analyzed.

HEAT EXCHANGER DESIGN OPTIMISATION

In this paper, an optimized model of Shell and Tube Parallel Flow Heat Exchanger of water and oil type is proposed using C++ programming language. Shell and tube heat exchangers are of special importance in boilers, oil coolers, condensers, pre-heaters etc. They are also used in high pressure operations, refrigeration and air conditioning industry and process applications. In this paper, a number of practical cases of shell and tube heat exchangers are taken and the analysis of thermal and constructional design of every case is done. The optimised design is obtained by minimising the pressure drop by maximising the heat exchanger area to reduce pumping and running cost. Also considering that large sizes lead to increased capital cost, heat exchanger area is also optimised to overcome this problem. Effect of design parameters on pressure drop and heat exchanger area is also explained.

Thermal Radiation and Noise Safety Assessment of an Offshore Platform Vent Pipe

The purpose of the offshore platform vent pipe is to release the excess associated gas produced by the oilfield production process in a safe place. Based on the characteristics of the vent pipe of offshore oil platform and the potential hazards of the vent pipe to some working points on the platform caused by sudden emergency discharge, this paper focuses on the analysis of the thermal radiation and noise of each working point on the offshore platform, the thermal radiation and noise of the calculation point were simulated by Flaresim 6.0. The evaluation method is based on the guidelines for pressure relief and decompression systems recommended by the American Petroleum Institute (API RP 521). The simulation results of Flaresim software show that the thermal radiation and noise values of the main working points on the offshore platform meet the requirements of the limits. However, in order to avoid high temperature phenomenon on the surface of the equipment in the working area, low absorptivity coating or protective layer should be used on the surface of the equipment. When vent pipe is empty, the staff should return to the room as far as possible or must wear sound insulation earplug for protection to meet the noise safety assessment. Through the detailed analysis of thermal radiation and noise safety design of offshore platform vent pipe, this study provides an effective reference for similar vent pipe or flare system design projects in the future.

Numerical analysis of thermal radiation of spacecraft on orbit based on SINDA/FLUINT

Thermal stability is an important indicator to measure the reliability of aerospace equipment, and the space thermal environment is complex, and the commonly used thermal analysis software for ground equipment can no longer meet the needs. For this reason, based on the thermal design analysis software SINDA/FLUINT, taking a spacecraft as the research object, the thermal balance equation is first established. Then, use the thermal desktop software to establish a numerical model, and use the SINDA/FLUINT software to solve the heat transfer process. Finally, the thermal desktop is used to post-process the calculation results and analyse the thermal radiation of the spacecraft.

Thermal analysis of loop mediated isothermal DNA amplification (LAMP) based point-of-care diagnostic device

Loop-Mediated Isothermal Amplification reaction or LAMP has been identified as a feasible DNA amplification process. Paper-based LAMP diagnostic devices offer several advantages for point-of-care (POC) applications. LAMP occurs at a constant temperature of higher limits, which remains a major challenge on-site. This calls for an efficient thermal design which is beneficial in maintaining a constant high temperature at POC locations. The present study reports thermal design and energy consumption analysis of a paper-based LAMP POC device for the first time using CFD analysis. The POC design consists of a rectangular porous membrane embedded on a rectangular solid material, heated from the side walls. Isothermal and discrete heating with different horizontal and vertical clearance configurations are used as a design parameter. CFD analysis of different thermal configurations is carried out in COMSOL Multiphysics platform to solve the energy and convection–diffusion-reaction equation in porous media. The thermal analysis demonstrated that two discrete heating configurations with high horizontal clearance are effective in reducing energy consumption. It was inferred that two portable AA batteries are sufficient for the POC device operation. Overall, the current work successfully demonstrates the energy optimization and speed of operation of the POC medical device by detailed thermal analysis.

Cyclone-Bed Furnaces: Experimental Studies and Thermal Design

Furnace processes occurring in laboratory setups, pilot commercial facilities, and small-capacity boilers of various sized equipped with cyclone-bed furnaces containing fixed and fluidized beds burning solid biofuels (wood pellets, straw pellets, sunflower husk pellets, peat pellets, wood waste, wood chips, milled peat, and crushed peat bricks) are investigated. The distribution features of temperature and gas concentrations (CO, CO2, H2, O2, CH4) in the combustion and secondary combustion chambers have been established in the course of experiments. With this information available, it becomes possible to determine the zones in which fuel actively reacts with the oxidant under the conditions of two-stage vortex combustion. Dependences of the carbon monoxide (CO) and nitrogen oxide (NOх) concentrations in the flue gases on the excess air ratio, bottom blast share (primary air), furnace power, and the combustion chamber’s outlet hole diameter are obtained. The furnace processes in cyclone-bed furnaces are numerically simulated using the standard k–e turbulence model and the Magnussen combustion model, and satisfactory agreement between the calculation and experimental results is shown. A semiempirical method for designing cyclone-bed furnaces has been developed, according to which their main geometrical and operating parameters are determined in two stages: a preliminary thermal design analysis is first carried out, after which the furnace process is numerically simulated. Based on extensive generalization of experimental data on the burning of solid biofuels in cyclone-bed furnaces having different diameters, the parameter М = 0.52, which appears in the well-known Gurvich formula for the thermal design of furnace chambers, has been determined. This parameter takes into account the temperature field structure and the heat transfer pattern over the furnace height, thus making it possible to use the standard method in carrying out thermal design computations of furnaces.

A Procedure for Experimental and Numerical Investigations of Turbine Machinery Labyrinth Shroud Seals

Labyrinth seals installed in turbine machines serve for decreasing the working fluid leakage through the clearances between the rotating and stationary structural elements in order to increase its flowrate through the flow path. The operational efficiency and reliability of all types of turbine machines (steam, gas, and hydraulic turbines; compressors; fans; pumps; etc.) depend to an essential extent on the type of seals (labyrinth, groove, etc.), which determine the working fluid leakage and intensity of hydrodynamic forces acting on the rotor. Therefore, those who design turbine machines should use a close-to-reality model of the flow pattern in labyrinth seals. Such a model was developed in the 1970s by A.G. Kostyuk with his coworkers at the Moscow Power Engineering Institute and is quite widely used in analyzing the dynamics of turbine machines. However, the procedures for thermal and aerodynamic design analyses of turbine machines, as well as relevant standards and handbooks, do not contain a description of this model nor do they contain recommendations for using it. At present, such a state of things becomes especially dangerous in connection with wide application of numerical methods of 3D design and analysis, when the use of an inadequately selected flow model (in particular, in seals) may give rise to essential errors. The article presents a review and scrutiny of the used numerical and experimental models of shroud seals; their drawbacks are shown, and a model adequately representing a real flow is described.

Structural and Thermal Analysis for Design and Optimization of Disk Brake with Alternate Materials

In this present work the temperature fields and structural fields of the solid brake disc during short and emergency braking with four different materials have been analyzed. The distribution of the temperature depends on the various factors such as friction, mechanical properties of material, design of the brake disc, surface roughness and speed. We analyzed the different values of temperature, total deformation, the equivalent strain - stress and deformation for different designs and different materials using analysis software called Ansys with materials namely Stainless-Steel SS 420, SS 316 and Aluminium Al 6061, Al 7075. With the value at the hand the values are determined for best suitable material for the brake disc with higher life span. This work determines the shape and size optimized for disc brake along with chosen material for efficient disc with a better life span. Three different discs were designed with four different materials to produce a wide range of conclusions.

Application of metaheuristic algorithms in optimum thermal design analysis of a rectangular porous fin subjected to both insulated and convective tip conditions

In this novel optimization analysis, a rectangular porous fin subjected to convective tip conditions along with insulated end condition is studied. The aim is to optimize the important variables responsible for transferring heat from fin with insulated as well as convective tip to the surrounding in order to get a higher rate of heat transfer from the fin surface. Temperature-dependent solid and fluid thermal conductivities as well as variable internal heat generation is considered. To obtain heat dissipation rate through porous fin, the nonlinear governing equation is first solved analytically using Adomian decomposition method. Then the heat transfer rate, i.e., objective function of this problem is optimized with three powerful metaheuristic techniques, namely firefly algorithm, particle swarm optimization and gravitational search algorithm. A comparative analysis has revealed that fins with convective end show significantly higher heat transfer rate compared to their insulated end counterparts. Particle swarm optimization showed marginally higher heat transfer values compared to firefly algorithm but firefly algorithm took less computational effort to reach the optimum value.

Thermal design and CFD analysis of the radial inflow turbine for a CO 2 ‐based mixture transcritical Rankine cycle

Transcritical carbon dioxide (CO2) Rankine cycle has exhibited great potential in the field of low-temperature heat utilization. But its application is restricted by the condensing issue and the safety concern due to the relatively low critical temperature and high critical pressure of CO2. Blending CO2 with organic fluids for the transcritical Rankine cycle is regarded as an effective method to solve these problems. And the turbine performance has great influence on the performance of transcritical Rankine cycle. In this paper, the thermal design of the CO2-based mixture turbine is firstly carried out based on the parametric optimization of the system. Then the computational fluid dynamics (CFD) analysis is performed to examine the turbine performance and validate the reliability of thermal design. Furthermore, the effects of blade tip clearance and nozzle-to-rotor clearance on the turbine performance are investigated. Results show that the turbine is well designed with an isentropic efficiency of 84.54%, and the CFD simulation results basically agree with the thermal design results. The influence of leakage flow on mainstream grows significantly as the blade tip clearance increases. When the blade tip clearance is 2 mm, the relative loss of power output could achieve as large as 7.81%. Larger nozzle-to-rotor clearance leads to more uniform distributions of Mach number and pressure, but the flow losses also increase. The effect of trailing edge disturbance on the flow field at the nozzle outlet is almost negligible if the nozzle-to-rotor clearance is 6 mm or more.