Interior Temperature Distribution Research Articles

Impact of a novel emergency cooling system on data center environment under long-term power failure

Nuclear power plant data centers (NPPDCs) are in charge of regulating nuclear reactors. For nuclear safety, the cooling system should provide a stable operating environment for the NPPDC. A novel emergency cooling system with ultralow-temperature heat exchangers could enhance interior radiant cooling. Liquid nitrogen (LN2) flows into the indoor finned tube heat exchangers (FTHEs) under the pressure of the storage tank. In this paper, the impacts of the FTHE layout and connection and the LN2 flow rate on server cooling and interior temperature distribution were explored through experiments. The results indicated that the position and quantity of the LN2 inflow section had a major impact on the cooling effect of the cabinet. Changing the LN2 flow rate can adjust the cooling. A massive flow of LN2 was suitable for rapid emergency cooling while degrading the temperature stratification. In parallel, the FHTEs provided the best cooling effect and temperature uniformity. The Parallel 1 scheme cooled the interior of the cabinet 20% faster than the Parallel 2 scheme, and it had 11.3% less temperature stratification near the cabinet (Line 2).

Ultrasonic measurement of temperature distributions in extreme environments: Electrical power plants testing in utility-scale steam generators

Thermal heterogeneities within energy conversion and storage, material processing, nuclear processes, aerospace, and military applications are often inaccessible to characterization by insertion sensors. When sensor deployment is possible, conventional pointwise temperature probes quickly degrade when inserted into harsh environments typical of such processes. We developed spatially-resolved ultrasonic thermometry to noninvasively measure the spatial distributions of thermal properties in such applications, even when sizable thermal gradients are present. Our method divides the path of ultrasonic propagation into segments bound by echogenic features, which create echoes in pulse-echo mode, encoding the information about interior temperature distributions. We use the acquired ultrasonic responses to estimate the internal temperature distributions by solving an inverse problem or concatenating segmental estimates. This work describes the implementation and industrial testing of the developed method at a coal-fired electrical power generation plant. We inserted an echogenically segmented Inconel 625 waveguide into the combustion zone of the utility-scale boiler and continuously acquired ultrasonic data while keeping sensitive components away from the damaging combustion environment. The accuracy of the time-dependent temperature distributions reconstructed from the ultrasonic measurements was comparable to that of thermocouples. The resiliency of ultrasonic thermometry to harsh combustion conditions was far superior to conventional insertion sensors. The measurements obtained during plant operation captured daily steam generation cycles in response to changing customer demand and intermittent contributions of renewable power sources to the power grid. These measurements have revealed new insights into the relationship between the dynamic power generation load and the conditions inside the steam generator. The successful industrial testing of spatially-resolved ultrasonic thermometry in solids indicates that the developed technology has matured to become an attractive alternative to conventional sensing in solving challenging problems of long-term thermal characterizations in extreme environments.

A reconstructed approach for online prediction of transient heat flux and interior temperature distribution in thermal protect system

Thermal protect system (TPS) is a crucial part of spacecraft to shield them from the aerodynamic heating during the atmospheric entry/re-entry. In this paper, the aerodynamic heating on the surface of a reusable launch vehicle is predicted to achieve rational design of the TPS. The conduction-radiation heat transfer in the TPS that was regard as a kind of index graded medium, was computed using finite volume method and discrete ordinate method. The extended Kalman filtering coupled with Rauch-Tung-Striebel smoother is introduced for calculating the inverse problem to obtain the time-variant heat flux and interior temperature fields in TPS. The impact of the structure parameters and future measurement temperature information on the lag and stability of retrieval results is investigated. The actual heat flux generated at NASA Langley Research Center for the Reusable Launch Vehicle is employed for examining the effectiveness and dependability of the proposed approach. The numerical results demonstrate the present approach can realize precise and on-line prediction of the time-variant heat flux and interior temperature fields in TPS.

Flow and heat transfer studies of multijet impingement cooling for different configurations: A review

AbstractIncreasing the gas turbine engine's turbine intake temperature has long been a potential strategy for increasing the specific work output of the engine. However, the melting temperature of the turbine blades and vane material limits the maximum intake temperature. As a result, internal and external cooling techniques are commonly used to maintain the vane material in a safe condition. This study provided an overview of internal impingement cooling to highlight the significance of geometrical variations, such as flat plate, curve plate, and actual vanes. It was observed that flat and curved plate impingement heat transfer studies were reported extensively, whereas limited studies were found on the conjugate effects on airfoil surfaces. The importance of conjugate heat transfer studies and their impact has recently been described in the literature. In most of the literature, a wide range of instruments, such as Laser Doppler Velocimeter, Particle Image Velocimeter, liquid crystal sheets, and so forth, were used for experimental investigations. According to most studies, the local value of internal surface temperature and heat transfer coefficient are vital factors of local flow behavior. Jet‐to‐jet spacing, jet‐to‐plate spacing, jet hole diameter, and jet Reynolds numbers played a crucial role in both numerical and experimental analyses. Different geometric variations strongly influence flow behavior. Therefore, the usual method for determining interior temperature distributions and heat transfer coefficients by considering generalized geometries like the flat and curved plate may not produce accurate conjugate solutions. Most of the computational studies on the flat and curved plate indicate the usage of κ−ω shear stress transport and κ–ε realizable model to predict the heat transfer coefficient.

Numerical investigation of heat transfer and fluid motion in air inflatable textiles: Effect of thickness, surface emissivity and ambient temperature

Air inflatable textile has attracted increasing attention due to the advantage of light, cheap, environmentally friendly and low thermal conductivity. While its thermal insulation is still not yet well understood since the complex interior heat and mass transfer under various thickness and ambient conditions. In this work, a three-dimensional model was developed to investigate the fluid motion and heat transfer in both air inflatable and fiber-filled textiles. The coupled conduction, convection and radiation were modelled by CFD approach. The experimental and numerical results were compared to verify the proposed model. Good agreements were found with the average difference in surface temperature and heat flux less than 2.54% and 9.95%, respectively. Then the effect of various parameters including thickness, surface emissivity and ambient temperature on heat flux, thermal resistance and fluid flow behavior was further analyzed. The simulated interior velocity and temperature distribution suggested that the higher thickness (≥10 mm) was not favorable for better thermal insulation when the air was adopted as thermal insulation layer. Because more available space for air movement would accelerate thermal convection and result in the deteriorated thermal insulation. In addition, inner surface layer with lower emissivity could effectively suppress the thermal radiation in air inflatable textiles and was beneficial to increase the thermal insulation. Besides, the thermal insulation of fiber-filled textile was nearly unaffected when lower ambient temperature was applied, while that of air inflatable textiles significantly decreased due to the aggravated convective heat and flow transfer under large temperature difference.

Improving Heat Exchange Performance of Massive Concrete Using Annular Finned Cooling Pipes

Cracks will be generated due to high internal temperature of the massive concrete. Postcooling method is widely employed as a standard cooling technique to decrease the temperature of the poured mass concrete. In this paper, an annular finned cooling pipe which can increase the heat transfer area between the flowing water and its surrounding concrete is proposed to enhance the cooling effect of the postcooling method. Analysis of the interior temperature variation and distribution of the concrete block cooled by the annular finned cooling pipe system and the traditional cooling pipe system was conducted through the finite element models. It is found that, for the concrete block using the proposed annular finned cooling pipe system, the peak value of the interior temperature can be further lowered. Compared with the traditional cooling pipe, the highest temperature of concrete with an annular finned cooling pipe appears earlier than that with the traditional cooling pipe.

Temperature non-uniformity in the radiative cooler and its effect on performance under various humidity conditions

Sub-ambient diurnal radiative cooling is an effective, environment-friendly and energy-saving passive cooling approach as it cools a surface without anthropogenic energy input. The cooling power of a radiative cooler is strongly influenced by the meteorological conditions, in particular humidity, on which quite a few investigations have been conducted so far. However, the cooling power evaluation of a radiative cooler usually considers the radiative cooler to be isothermal, which ignores the interior temperature difference resulted from the low thermal conductivity of the prevalent radiative materials, leading to an overestimation of the cooling power. Therefore, this work focuses on the theoretical evaluation of the radiative cooling power along with the interior temperature distribution under varying humidity conditions through incorporating coupled heat and radiation transfer approach. The results show that higher relative humidity leads to less cooling power and minor interior temperature difference in the radiative cooler. In addition, the position of the lowest temperature inside the radiative cooler, which is usually taken at the bottom of the radiative cooler, gradually approaches the surface facing outer space with the increase in humidity during the diurnal time. Our work provides a unique viewpoint for predicting the cooling power by taking interior temperature non-uniformity resulted from the low thermal conductivity into account, which elaborates a vivid picture of the evolution of radiative cooling power as well as the internal temperature distribution with the variation of humidity. Such an approach is beneficial for the further design, efficiency enhancement and on-site deployment of radiative coolers.

Reduction of interior temperature of massive concrete using an enhanced heat transfer pipe array with spiral fins

The interior temperature of the massive concrete should be controlled to avoid cracks caused by the trapped hydration heat. In this paper, an enhanced heat transfer pipe array with spiral fins (PSF) is proposed to reduce the interior temperature of concrete blocks. Numerical simulations of massive concrete blocks embedded with traditional cooling water pipe (TCWP) and newly proposed PSF were conducted to investigate the interior temperature distribution of massive concrete. Meanwhile, validity of the finite element model was verified by both theoretical results and available experimental data. Based on the calculated temperature distribution of the points located in the interior area of the massive concrete, it is shown that when the TCWP was replaced by the PSF, the interior temperature can be significantly reduced. Therefore, compared to the TCWP, the proposed PSF has excellent heat transfer performance for cooling the interior temperature of massive concrete.

Heat Transfer Evaluation on Microwave Sterilization: Case Study of Oil Palm Fruit

Microwave energy can be used for oil palm fruit bunch sterilization. It penetrates onto the core of oil palm fruit bunches and generates heat inside out. This sterilization aims to inactivate lipase that influences palm oil quality. This study evaluates effect of dielectric properties power developed per unit volume and interior temperature distribution on heating rate during heating process. The experiment carried out at various combinations of microwave power and the oil palm bunches portion in microwave oven. This study observed that distribution of interior temperature in a single oil palm fruit was influenced by power density and fruit’s diameter. Greater power density provides high microwave energy per kg sample to attain greater temperature of microwave heating and vice versa. Distribution of interior temperature in the fruit with the thickness (r) of 6 mm and above indicated non-uniformity heating. Furthermore, interior temperature of fruitlet with r = 4.5 mm indicated distribution of temperature from endocarp to exocarp, meanwhile simulation temperature on smaller fruit diameter (r = 3 mm) indicated thermal runway effect after 5 min heating duration.

Tidally induced lateral variations of Io's interior

Satellite and recent Earth-based observations of Io's surface reveal a specific spatial pattern of persisting hotspots and sudden high-intensity events. Io's major heat producing mechanism is tidal dissipation, which is thought to be non-uniformly distributed within Io's mantle and asthenosphere. The question arises to what extent Io's non-homogeneous heat production can cause long-wavelength variations in the interior and volcanic activity at the surface. We investigate dissipation patterns resulting from two different initially spherical symmetric visco-elastic rheological structures, which are consistent with geodetic observations. The spatial distributions of the time-averaged tidal heat production are computed by a finite element model. Whereas for the first rheological structure heat is produced only in the upper viscous layer (asthenosphere-heating model), the second rheological structure results in a more evenly distributed dissipation pattern (mixed-heating model) with tidal heating occurring in the deep mantle and the asthenosphere. To relate the heat production to the interior temperature and melt distribution, we use steady-state scaling laws of mantle convection and a simple melt migration model. The resulting long-wavelength thermal heterogeneities strongly depend on the initial tidal dissipation pattern, the thickness of the convective layer, the mantle viscosity, and the ratio between magmatic and convective heat transport. While for the asthenosphere-heating model a strong lateral temperature signal with up to 190 K peak-to-peak difference can remain, convection within a thick convective layer, as for the mixed-heating model, can reduce the lateral temperature variation to <1 K, if the mantle viscosity is sufficiently low. Models with a dominating magma heat transport preserve the long-wavelength pattern of tidal dissipation much better and are favoured, because they are better to explain Io's thick crust. The approach presented here can also be applied to investigate the effect of an arbitrary interior heating pattern on Io's volcanic activity pattern.

Numerical Simulation and Optimization of the Melting Process of Phase Change Material inside Horizontal Annulus

Latent heat storage (LHS) technologies adopting phase change materials (PCMs) are increasingly being used to bridge the spatiotemporal mismatch between energy production and demand, especially in industries like solar power, where strong cyclic fluctuations exist. The shell-and-tube configuration is among the most prevalent ones in LHS and thus draws special attention from researchers. This paper presents numerical investigations on the melting of PCM, a paraffin blend RT27, inside a horizontal annulus. The volume of fluid model was adopted to permit density changes with the solidification/melting model wherein natural convection was taken into account. The eccentricity and diameter of the inner tube, sub-cooling degree of the PCM, and the heating-surface temperature were considered as variables for study. Through the evaluation of the melting time and exergy efficiency, the optimal parameters of the horizontal annulus were obtained. The results showed that the higher the heating boundary temperature, the earlier the convection appeared and the shorter the melting time. Also, the different eccentricity and diameters of the inner tube influenced the annulus tube interior temperature distribution, which in turn determined the strength and distribution of the resulting natural convection, resulting in varying melting rates.

Field study of thermal comfort and occupant satisfaction in Canadian condominiums

ABSTRACTIn Canada and much of the world, high-rise residential buildings with large glazing areas are increasing in popularity. These buildings are associated with lower thermal resistance envelopes and higher solar gains than more traditional construction with smaller windows. This study explores the comfort implications and usability in condominiums by performing a field study of 20 units: 10 with large window areas (LW) and 10 with medium-sized window areas. Occupant comfort was assessed in summer and winter, through two open-ended surveys, infrared thermography, and recorded interior temperature and humidity. LW occupants more often report uneven interior temperature distributions and windows as a source of discomfort in winter. One quarter of condo units experience condensation on windows, indicating window and frame improvements may benefit both groups. This exploratory study identifies key issues and occupant preferences within condominiums to guide future research on this building type.

A strategy to simulate radio frequency heating under mixing conditions

A computer simulation model was developed using finite element-based commercial software, COMSOL, to simulate temperature distributions in wheat samples packed in a rectangular plastic container and treated in a 6kW, 27.12MHz RF system with and without mixing conditions. The developed model was then experimentally validated by temperature distributions of three layers without mixing condition, and surface and interior temperature distributions of wheat samples under one, two and three times mixing conditions. Both simulation and experiment showed similar heating patterns in RF treated wheat samples under both conditions, in which corners and edges were overheated and the temperatures were higher in the lower sections of the container. The uniformity index (UI) was used to evaluate effects of mixing on RF heating uniformity. Both experimental and simulated UI showed decreasing trend with the increasing mixing times. The developed model can help to understand the RF heating patterns and effects of mixing conditions on RF heating uniformity and provide valuable strategy for developing effective industrial-scale RF treatments with mixing processes.

The Effect of Pallet Component Geometry on Temperature Gradient During Cooling

Abstract The paper discusses the impact of the geometry of foundry pallet components on the value of temperature gradient on the wall crosssection during heat treatment. The gradient is one of the most important factors determining the distribution of thermal stresses in these items. Analysis of quantitative simulation was carried out to detect possible effect of the type of connection between pallet walls and thickness of these walls (ribs) on the interior temperature distribution during rapid cooling. The analysis was performed for five basic designs of wall connections used in pallets. Basing on the results obtained, the conclusions were drawn on the best connection between the ribs in foundry pallets.

A Discrete/Continuous Numerical Approach to Multi-physics

A variety of technical applications are not only the physics of a single domain, but include several physical phenomena, and therefore are referred to as multi-physics. As long as the phenomena being taken into account is either continuous or discrete i.e. Euler or Lagrangian a homogeneous solution concept can be employed. However, numerous challenges in engineering include continuous and discrete phase simultaneously, and therefore cannot be solved only by continuous or discrete approaches. Problems include both a continuous and a discrete phase are important in applications of the pharmaceutical Industry e.g. drug production, agriculture and food processing industry, mining, construction and Agricultural machinery, metal production, power generation and systems biology.The Extended Discrete Element Method (XDEM) is a novel technique, which provides a significant advance for the coupled discrete and continuous numerical simulation concepts. It expands the dynamics of particles as described by the classical discrete element method (DEM) by a thermodynamic state or stress/strain coupled as fluid flow or structures for each particle in a continuum phase. XDEM additionally estimates properties such as the interior temperature and/or species distribution. These predictive capabilities are extended to fluid flow through an interaction by heat, mass and momentum transfer important for process engineering.

Temperature measurements of high-temperature semi-transparent infrared material using multi-wavelength pyrometry

Temperature measurements inside semi-transparent materials are important in many fields. This study investigates the measurements of interior temperature distributions in a one-dimensional semi-transparent material using multi-wavelength pyrometry based on the Levenberg–Marquardt method (LMM). The investigated material is semi-transparent Zinc Sulfide (ZnS), an infrared-transmitting optical material operating at long wavelengths. The radiation properties of the one-dimensional semi-transparent ZnS plate, including the effective spectral–directional radiation intensity and the proportion of emitted radiation, are numerically discussed at different wavelengths (8.0–14.0μm) and temperature distributions (400–800K) to provide the basic data for the temperature inversion problem. Multi-wavelength pyrometry was combined with the Levenberg–Marquardt method to resolve the temperature distribution along the radiative transfer direction based on the line-of-sight spectral radiation intensities at multiple wavelengths in the optimized spectral range of (11.0–14.0μm) for the semi-transparent ZnS plate. The analyses of the non-linear inverse problem show that with less than 5.0% noise, the inversion temperature results using the Levenberg–Marquardt method are satisfactory for linear or Gaussian temperature distributions in actual applications. The analysis provides valuable guidelines for applications using multi-wavelength pyrometry for temperature measurements of semi-transparent materials.

The Study of Infrared Heating on PET Bottles by Experiment and Adaptive Finite Volume Method

Stretch-Blow moulding (SBM) fabricate process is a well known method to produce PET bottles. During the construction procedure, PET surface temperature distribution controlled by infrared heating is the key factor about manufacture technique for the better quality of PET. This paper focuses on how to measure and estimate temperature distribution on the surface of semi-transparent polymers so that we can make sure the proper position and intensity of the infrared lamb. We use infrared camera to detect the real temperature distributions and C++ object-oriented programming to estimate the infrared radiation (IR) results by adaptive finite volume method (Adaptive FVM). The numerical results have been compared with experimental results and the consequence is satisfied. Multiple lambs’ cases and the interior temperature distribution in PET will be discussed in future.

Simulation on Steel Solidification and its Shrinkage in Mould of FTSC Slab

The solidification shrinkage of liquid steel has an important impact on thermal deformation behavior of high-temperature thin shell. Solidification shrinkage of liquid steel is an important basis for structure and shap optimization of the mould. In this paper, a direct coupled model was built on heat transfer in solidification and stress-strain by using the ANSYS software. And solidification shrinkage of liquid steel with the interior temperature and stress distribution were studied in the process of steel solidification, and it provided a theoretical basis for the further optimization of shape of the thin slab FTSC mould. This study was based on analysis of temperature and stress, deriving calculation of solidification shrinkage of steel’s phase change on macro-state by calculating the variation discipline of the distance between nodes.

Developing postharvest disinfestation treatments for legumes using radio frequency energy

There is an urgent need to develop technically effective and environmentally sound phytosanitary and quarantine treatments for the legume industry to replace chemical fumigation. The goal of this study was to develop practical non-chemical treatments for postharvest disinfestations of legumes using radio frequency (RF) energy. A pilot-scale 27 MHz, 6 kW RF unit was used to investigate RF heating and consequent quality attributes in treated chickpea, green pea, and lentil samples. Only 5–7 min were needed to raise the central temperature of 3 kg legume samples to 60 °C using RF energy, compared to more than 275 min when using forced hot air at 60 °C. RF heating uniformity in legume samples was improved by adding forced hot air, and back and forth movements on the conveyor at 0.56 m min−1. The final temperatures exceeded 55.8 °C in the interior of the sample container and 57.3 °C on the surface for all three legumes, resulting in low uniformity index values of 0.014–0.016 (ratio of standard deviation to the average temperature rise) for the interior temperature distributions and 0.061–0.078 for surface temperature distributions. RF treatments combined with forced hot air at 60 °C to maintain the target treatment temperature for 10 min followed by forced room air cooling through a 1 cm product layer provided good product quality. No significant differences in weight loss, moisture content, colour or germination were observed between RF treatments and unheated controls.

Calculating Transient Temperature Distribution of Single-coated Tool in High Speed Cutting

In order to research the influence of coating on tool temperature during cutting,so as to provide theoretical basis for the design of tool coating,the generation of cutting heat and the tool boundary condition in the high speed cutting process are analyzed,and the physical and mathematical models of single-coated tool heat conduction are built. The interior temperature distribution formula of single-coated tool in the orthogonal high speed cutting process is derived by using mathematical analysis method. Analytical calculations of the cutting temperature distributions of TiN,TiC,Al2O3 coated tools are carried out by using the derived temperature formula,and the result of analytical calculation is compared with that of numerical analysis. The comparison shows that they are in good agreement. The thermophysical properties of coating material and substrate material and the thickness of coating have important influence on temperature rise. With the increase of heat flow density,the influence of coating thickness on the interior temperature of tool is enhanced.