Rewet Temperature Correlations for Liquid Nitrogen Boiling Pipe Flows Across Varying Flow Conditions and Orientations

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
S. R. Darr ◽  
J. Dong ◽  
N. Glikin ◽  
J. W. Hartwig ◽  
J. N. Chung
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Liquid Nitrogen ◽  
Heat Transfer Process ◽  
Transport Processes ◽  
Liquid Oxygen ◽  
Cryogenic Fluids ◽  
Wide Range ◽  
Leidenfrost Temperature ◽  
Phase Change Heat Transfer

In many convective liquid–vapor phase-change heat transfer engineering applications, cryogenic fluids are widely used in industrial processes, spacecraft and cryosurgery systems, and so on. For example, cryogens are usually used as liquid fuels such as liquid hydrogen, liquid methane, and liquid oxygen in the rocket industry, liquid nitrogen and helium are frequently used to cool superconducting magnetic device for medical applications. In these systems, proper transport, handling, and storage of cryogenic fluids are of extreme importance. Among all the cryogenic transport processes performed in room temperatures, quenching, also termed chilldown, is an unavoidable initial, transient phase-change heat transfer process that brings the system down to the cryogenic condition. The Leidenfrost temperature or rewet temperature that signals the end of film boiling is practically considered the completion point of a quenching process. Therefore, rewet temperature has been considered the most important parameter for the engineering design of cryogenic thermal management systems. As most of the previous correlations for predicting the Leidenfrost temperature and the rewet temperature have been developed for water, they are shown to disagree with recent liquid nitrogen pipe chilldown experiments in upward and downward flow directions over a wide range of flow rates, pressures, and degrees of inlet subcooling. In addition to a complete review of the literature, two modified correlations are presented, one based on bubble growth and another based on the theoretical maximum limit of superheat. Each correlation performs well over the entire dataset.

scholarly journals Thermal Analysis of Solid/Liquid Phase Change in a Cavity with One Wall at Periodic Temperature

Energies ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5957
Author(s):  
Shogo Tomita ◽  
Hasan Celik ◽  
Moghtada Mobedi
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Thermal Storage ◽  
Heat Transfer Process ◽  
Freezing Process ◽  
Dimensionless Frequency ◽  
Governing Equations ◽  
Stefan Number ◽  
Wide Range ◽  
Almost All

In this study, heat transfer in a square cavity filled with a Phase Change Material (PCM) under a sinusoidal wall temperature during solidification and melting is analyzed. All surfaces of the cavity are insulated except one surface, which is under the sinusoidal temperature change. The governing equations and boundary conditions are made dimensionless to reduce the number of governing parameters into two as dimensionless frequency and Stefan number. The governing equations were solved numerically by using Finite Volume Method for a wide range of Stefan number (0.1 < Ste < 1.0) and dimensionless frequency (0.23 < < 2.04). Based on the obtained results, a chart in terms of Stefan number and dimensionless frequency is obtained to divide the heat transfer process in the cavity into three regions as uncompleted, completed, and overheated phase-change processes. For the uncompleted process, some parts of the cavity are inactive, and no phase change occurs in those parts of the cavity during the melting and freezing process. For the overheated phase change, the temperature of the cavity highly increases (or decreases), causing the sensible heat storage to compete with latent thermal storage. In the completed process, almost all thermal storage is done by the utilization of latent heat. The suggested graph helps thermal designers to avoid wrong designs and predict the type of thermal storage (sensible or latent) in the cavity without doing any computations.

Transient Axial Free Jet Impinging Over a Flat Uniformly Heated Disk: Solid–Fluid Properties Effects

2000 ◽  
Author(s):  
Antonio J. Bula ◽  
Muhammad M. Rahman ◽  
John E. Leland
Keyword(s):  
Heat Transfer ◽  
Steady State ◽  
Transfer Process ◽  
Conjugate Heat Transfer ◽  
Finite Thickness ◽  
Heat Transfer Process ◽  
Transport Processes ◽  
Liquid Region ◽  
Free Jet ◽  
Wide Range

Abstract Transient conjugate heat transfer process during axial free jet impingement on a solid disk of finite thickness was considered. As the fluid reached steady state, power was turned on and a uniform heat flux was imposed on the disk at its opposite surface. The numerical model considered both solid and fluid regions. Equations for conservation of mass, momentum, and energy were solved in the liquid region taking into account the transport processes at the inlet and exit boundaries, as well as at the solid-liquid and liquid-gas interfaces. Inside the solid, only the heat conduction equation was solved. The shape and location of the free surface (liquid-gas interface) was determined iteratively as a part of the solution process by satisfying the kinematic condition as well as the balance of normal and shear forces at this interface. A non-uniform grid distribution, captured from a systematic grid-independence study, was used to adequately accommodate large variations near the solid-fluid interface. Computed results include the simulation of six different substrate materials namely, aluminum, constantan, copper, diamond, silicon, and silver, and three different impinging liquids, FC - 77, Mil - 7808, and water. The solids and fluids selected covered a wide range of possibilities of conjugate heat transfer phenomena. The analysis performed showed that the thermal storage capacity, defined as density times specific heat, is an important factor defining which material will attain steady state faster during conjugate heat transfer process, like the thermal diffusivity does it for pure conduction heat transfer.

An Appraisal of System Mean Void Fraction and Its Application for the Moving Boundary Simulation of Phase-Change Heat Exchangers

2015 ◽  
Vol 137 (12) ◽  
Author(s):  
S. P. Datta ◽  
R. K. Chandra ◽  
P. K. Das
Keyword(s):  
Heat Transfer ◽  
Phase Change ◽  
Void Fraction ◽  
Heat Exchangers ◽  
Moving Boundary ◽  
Transport Processes ◽  
Closed Form Expression ◽  
Two Phase ◽  
Slip Ratio ◽  
Wide Range

In gas–liquid two-phase flow, void fraction is the most unique parameter which influences all the transport processes. In the most general case, though the void fraction varies nonlinearly with the channel length, many practical simulations make use of the “system mean void fraction.” The present investigation makes a critical assessment of different system mean void fraction models for a wide range of slip velocity and density difference between the phases. To this end, different correlations for slip ratio have been considered and, for all the cases, closed form expression for the system mean void fraction has been presented. The local as well as the system mean void fractions have also been estimated numerically from a heat transfer based model. Predictions from the heat transfer based model and the slip ratio based model have been compared. As an application, the slip ratio based system mean void fraction is used in to build the moving boundary model for phase-change heat exchangers. The prediction of startup transients for both an evaporator and a condenser of an automotive air conditioning system (AACS) agrees well with the experimental results.

The Research for Uncertainty Heat Transfer Process of Phase Change Thermal Storage Based on Monte Carlo Method

2013 ◽  
Vol 291-294 ◽  
pp. 632-635
Author(s):  
Zhi Yong Li ◽  
Yu Qing Zhao ◽  
Xue Zou
Keyword(s):  
Heat Transfer ◽  
Monte Carlo ◽  
Monte Carlo Method ◽  
Phase Change ◽  
Transfer Process ◽  
Thermal Storage ◽  
Heat Transfer Process ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Phase Change Heat Transfer

Because of phase change materials (PCMs)’ composition, machining error, measuring error and other factors, the PCMs’ thermal physical properties, geometric properties, etc are usually uncertain. Phase change heat transfer process is an uncertainty heat transfer process. In this paper, it is considered factors’ uncertainty influencing phase change thermal storage heat transfer process. Heat transfer model of phase change thermal storage is established. And the uncertainty phase change heat transfer process is analysis based on Monte Carlo method. The experiment shows that the temperature of PCMs varied between the upper bound and lower bound of calculations. Comparison between simulation results of the model and experimental data implies that it is necessary to consider influencing factor’s uncertainty in phase change thermal storage heat transfer analysis.

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.

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