scholarly journals Establishment and Verification of a Thermal Calculation Model Considering Internal Heat Transfer of Accumulated Water in Permafrost Regions

2021 ◽  
Vol 9 ◽  
Author(s):  
Erxing Peng ◽  
Xiaoying Hu ◽  
Yu Sheng ◽  
Fansheng Zhou ◽  
Jichun Wu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Impact Analysis ◽  
Internal Heat ◽  
Heat Transfer Process ◽  
Thermal Calculation ◽  
Thermal Impact ◽  
Actual Temperature ◽  
Buoyancy Convection ◽  
Permafrost Regions ◽  
Calculation Models

Water accumulation in permafrost regions causes a heavy thermal impact on the frozen layer, thereby leading to its degeneration. First, based on the real heat transfer process, this study proposes relevant hypotheses and governing equations for heat calculation models involving completely melted water, ice-bearing water, water–soil interface, and soil under water. The models consider the water surface as a thermal boundary on account of the natural buoyancy convection mechanism in water and the phase transition process. Second, this study verifies the accuracy of the calculation models regarding the measured water and permafrost temperatures. The four seasonal vertical temperature changes in the water according to this model are found to be consistent with the actual temperature-change trend, and the permafrost temperature under water is also consistent with the actual temperature field. This study thus provides theoretical support for the thermal impact analysis of water in permafrost regions.

scholarly journals A Computational Study on the Role of Parameters for Identification of Thyroid Nodules by Infrared Images (and Comparison with Real Data)

Sensors ◽  
2021 ◽  
Vol 21 (13) ◽  
pp. 4459
Author(s):  
José R. González ◽  
Charbel Damião ◽  
Maira Moran ◽  
Cristina A. Pantaleão ◽  
Rubens A. Cruz ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Thyroid Nodules ◽  
Numerical Study ◽  
Computational Study ◽  
Internal Heat ◽  
Heat Transfer Process ◽  
The Body ◽  
Physical Parameters ◽  
Infrared Sensors ◽  
Wide Range

According to experts and medical literature, healthy thyroids and thyroids containing benign nodules tend to be less inflamed and less active than those with malignant nodules. It seems to be a consensus that malignant nodules have more blood veins and more blood circulation. This may be related to the maintenance of the nodule’s heat at a higher level compared with neighboring tissues. If the internal heat modifies the skin radiation, then it could be detected by infrared sensors. The goal of this work is the investigation of the factors that allow this detection, and the possible relation with any pattern referent to nodule malignancy. We aim to consider a wide range of factors, so a great number of numerical simulations of the heat transfer in the region under analysis, based on the Finite Element method, are performed to study the influence of each nodule and patient characteristics on the infrared sensor acquisition. To do so, the protocol for infrared thyroid examination used in our university’s hospital is simulated in the numerical study. This protocol presents two phases. In the first one, the body under observation is in steady state. In the second one, it is submitted to thermal stress (transient state). Both are simulated in order to verify if it is possible (by infrared sensors) to identify different behavior referent to malignant nodules. Moreover, when the simulation indicates possible important aspects, patients with and without similar characteristics are examined to confirm such influences. The results show that the tissues between skin and thyroid, as well as the nodule size, have an influence on superficial temperatures. Other thermal parameters of thyroid nodules show little influence on surface infrared emissions, for instance, those related to the vascularization of the nodule. All details of the physical parameters used in the simulations, characteristics of the real nodules and thermal examinations are publicly available, allowing these simulations to be compared with other types of heat transfer solutions and infrared examination protocols. Among the main contributions of this work, we highlight the simulation of the possible range of parameters, and definition of the simulation approach for mapping the used infrared protocol, promoting the investigation of a possible relation between the heat transfer process and the data obtained by infrared acquisitions.

Numerical Analysis of Heat Transfer in a Leading Edge Geometry With Racetrack Holes and Film Cooling Extraction

2013 ◽  
Author(s):  
Luca Andrei ◽  
Antonio Andreini ◽  
Riccardo Da Soghe ◽  
Bruno Facchini ◽  
Stefano Zecchi
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Numerical Study ◽  
Internal Heat ◽  
Leading Edge ◽  
Jet Impingement ◽  
Internal Surface ◽  
Heat Transfer Process ◽  
University Of Florence ◽  
The Impact

A numerical study of a state of the art leading edge cooling scheme was performed to analyze the heat transfer process within the leading edge cavity of a high pressure turbine airfoil. The investigated geometries account a trapezoidal supply channel with a large racetrack impingement holes. The coolant jets, confined among two consequent large fins, impact the leading edge internal surface and it is extracted from the leading edge cavity through both showerhead holes and film cooling holes. The CFD setup has been validated by means of the experimental measurements performed on a dedicated test rig developed and operated at University of Florence. The aim of this study is to investigate the combined effects of jet impingement, mass flow extraction and fins presence on the internal heat transfer of the leading edge cavity. More in details, the paper analyses the impact, in terms of blade metal temperature, of large fins presence and positioning. Jet’s Reynolds number is varied in order to cover the typical engine conditions of these cooling systems (Rej = 20000 – 40000).

scholarly journals Determination of the electrical power increase at the generator terminals of a nuclear power plant unit at different condenser states

2021 ◽  
Vol 3 (8(111)) ◽  
pp. 60-67
Author(s):  
Kateryna Bratkovska ◽  
Yuliya Liush
Keyword(s):  
Heat Transfer ◽  
Electricity Generation ◽  
Capital Investment ◽  
Nuclear Power ◽  
Modular Design ◽  
Cooling Water ◽  
Steam Pressure ◽  
Heat Transfer Process ◽  
Thermal Calculation ◽  
Steam Turbines

It is shown that the technical condition of condensing devices of steam turbines largely determines the amount of electricity losses, reliable and economical operation of NPP units. Analysis of the heat transfer process in the condenser showed that the main causes of load reduction are determined by rising cooling water temperature and deviation of steam pressure from normal value. It is shown that among diagnostic parameters except leakage volumes there must be an assessment of contamination of the heat transfer surface which significantly affects the reduction of electricity generation. The modernization main points of the condenser of the Zaporizhzhya NPP power unit No. 3 on the principle of "block-modular" design developed by PJSC "Turboatom" and the characteristics of the condenser provided by the new design are considered. To reflect the real mode of operation of the condensing unit, it is proposed to model the contamination of the heat exchange surface and the presence of leakages in the condenser space using the method of thermal calculation of the condenser by iterative methods. It was found that reducing the increase in electricity generation as a result of the effects of the study factors can partially or even completely absorb the effect of upgrading the condenser plant. It will provide a significant increase in electricity generation with relatively low capital investment compared to construction of new NPP power units and improve the accuracy of power generation forecasts.

scholarly journals The Effects of Internal Heat Generation or Absorption on Mixed Convection in a Lid-Driven Rectangular Cavity using Finite Volume Method

CFD letters ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 38-54
Author(s):  
Norhaliza Abu Bakar ◽  
Rozaini Roslan ◽  
Mohd Kamalrulzaman Md Akhir
Keyword(s):  
Heat Transfer ◽  
Heat Generation ◽  
Heat Exchangers ◽  
Internal Heat ◽  
Heat Transfer Process ◽  
Internal Heat Generation ◽  
Flow And Heat Transfer ◽  
Horizontal Cavity ◽  
Heat Generation Or Absorption ◽  
Volume Method

Mixed convection heat transfer in cavities is a significant phenomenon in numerous engineering fields, such as nuclear reactors, solar energy storage, and heat exchangers. Despite acknowledging that a square is a basic shape found in these systems, not all the figures are geometrical. Less attention was given to the rectangle cavity even though it could be found in these systems. Various internal reactions could occur inside the systems, especially in geothermal heat exchangers. Therefore, this research aims to analyze the effect of internal heat generation or absorption in a two-dimensional (2D) horizontal cavity to the fluid flow and heat transfer process numerically. The vertical walls are well insulated. Meanwhile, the top and bottom walls are kept at and , respectively, where . The top wall moves at a constant speed from left to right. The finite volume method (FEM) and SIMPLE algorithm are employed to discretize the governing equations. Next, the algebraic equations are solved iteratively using the tri-diagonal matrix algorithm (TDMA). The influences of heat generation or absorption parameters are investigated in terms of the flow, heat transfer, and Nusselt number. The numerical results are plotted in the form of streamlines and isotherms. It is found that the presence of heat generation or absorption has a significant effect on the fluid flow and heat transfer process in the horizontal cavity. Overall, for internal heat generation, the heat transfer rate decreases, while the opposite pattern can be observed for the case of internal heat absorption. However, for Ri = 10.0, as the heat generation's value increases from 2 to 4, the heat transfer rate is the same.

Study on Coupled Conduction and Convection Heat Transfer Based on Internal Heat Source

2011 ◽  
Vol 90-93 ◽  
pp. 3001-3004
Author(s):  
Yong An Li ◽  
Ya Nan Gao ◽  
Ming Wang ◽  
Xue Lai Liu
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Source ◽  
Solid Wall ◽  
Convection Heat Transfer ◽  
Internal Heat ◽  
Internal Heat Source ◽  
Heat Transfer Process ◽  
Horizontal Distance ◽  
Computational Fluid Dynamics Cfd

A computational fluid dynamics (CFD) model is proposed to simulate numerically conjugated heat transfer process of fluid washing out solid with evenly internal heat source in the pipe. Temperature field and velocity field inside the pipe and outside solid are gained by calculation. Based on numerical simulation, the varying regularity of Nusselt number between fluid and solid wall surface is obtained and analyzed. The results show that there are two symmetrical vortexes in the back of solid. The Nusselt number and heat exchange rate dramatically decrease with increasing horizontal distance of top and bottom of solid.

Sign in / Sign up

Export Citation Format

Share Document