scholarly journals Methods for the Determination of the Heat Transfer Coefficient in Air Cooled Condenser Used at Biomass Power Plants

2021 ◽  
Vol 39 (5) ◽  
pp. 1443-1450
Author(s):  
Yanán Camaraza-Medina
Keyword(s):  
Heat Transfer ◽  
Power Plants ◽  
Analytical Study ◽  
Empirical Correlations ◽  
Functional Relationships ◽  
Average Coefficient ◽  
Access To Water ◽  
Biomass Power Plants ◽  
The Heat Transfer Coefficient

In the present work, its show a summary of functional relationships developed for the application of dry condensation systems to Biomass Power Plants that present difficulties with access to water for condensation. The bibliographic review reveals the limitations of the analyzed works, in terms of the development of mathematical models and empirical correlations that allow evaluating the simultaneous effects of the surrounding meteorological variables on the average coefficient of heat transfer and the effect on the environment of the use of dry condensation. The analytical study is based on the weak solutions and their correlation with experimental quantities available in research already established in the area of action, a procedure is developed for the calculation of the average coefficients of heat transfer that includes the influence of local climatologically variables, the effect of the spatial distribution of the tubes package on the refrigerant and the confined confinement in inclined components, which increase the reliability of the thermo-hydraulic analysis and suppresses the need for the use of excess areas required by current methods. The proposed models and correlations allow the preparation of a procedure, by means of which all the possible operative variants are evaluated.

Convective Heat Transfer at Minimum Fluidization Velocity for Gas-Solid Fluidized Beds

1999 ◽  
Author(s):  
Kal R. Sharma
Keyword(s):  
Heat Transfer ◽  
Fluidized Beds ◽  
Empirical Correlations ◽  
Transfer Coefficients ◽  
Minimum Fluidization Velocity ◽  
Heat Transfer Coefficients ◽  
Fluidization Velocity ◽  
Minimum Fluidization ◽  
Semi Empirical ◽  
The Heat Transfer Coefficient

Abstract Experimentally measured values for the minimum fluidization velocities and time averaged local surface heat transfer coefficients are provided for 16 different cases of fluidizing conditions for gas-solid dense fluidized beds. Semi-empirical Correlations for the minimum fluidization velocity and the heat transfer coefficient at minimum fluidization velocities are provided. The implications of the Peclet number dependence in terms of diffusion and convection is discussed.

Determination of the heat transfer coefficient of PV panels

Energy ◽  
2019 ◽  
Vol 175 ◽  
pp. 978-985 ◽  
Author(s):  
İlhan Ceylan ◽  
Sezayi Yilmaz ◽  
Özgür İnanç ◽  
Alper Ergün ◽  
Ali Etem Gürel ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
The Heat Transfer Coefficient

scholarly journals Online Determining Heat Transfer Coefficient for Monitoring Transient Thermal Stresses

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 704
Author(s):  
Magdalena Jaremkiewicz ◽  
Jan Taler
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Thermal Stresses ◽  
Thermal Power ◽  
Computer Calculation ◽  
Transient Temperature ◽  
Unsteady Temperature ◽  
The Heat Transfer Coefficient

This paper proposes an effective method for determining thermal stresses in structural elements with a three-dimensional transient temperature field. This is the situation in the case of pressure elements of complex shapes. When the thermal stresses are determined by the finite element method (FEM), the temperature of the fluid and the heat transfer coefficient on the internal surface must be known. Both values are very difficult to determine under industrial conditions. In this paper, an inverse space marching method was proposed for the determination of the heat transfer coefficient on the active surface of the thick-walled plate. The temperature and heat flux on the exposed surface were obtained by measuring the unsteady temperature in a small region on the insulated external surface of a pressure component that is easily accessible. Three different procedures for the determination of the heat transfer coefficient on the water-spray surface were presented, with the division of the plate into three or four finite volumes in the normal direction to the plate surface. Calculation and experimental tests were carried out in order to validate the method. The results of the measurements and calculations agreed very well. The computer calculation time is short, so the technique can be used for online stress determination. The proposed method can be applied to monitor thermal stresses in the components of the power unit in thermal power plants, both conventional and nuclear.

A Numerical Simulation of Pool Boiling Using CAS Model

2003 ◽  
Author(s):  
Jing Yang ◽  
Liejin Guo ◽  
Ximin Zhang
Keyword(s):  
Heat Transfer ◽  
Cellular Automata ◽  
Pool Boiling ◽  
Empirical Correlations ◽  
Dynamic Interactions ◽  
Macroscopic System ◽  
Simpler Algorithm ◽  
Boiling Process ◽  
Basic Features ◽  
The Heat Transfer Coefficient

This paper presents a new numerical model, called the CAS model, for boiling heat transfer. The CAS model is based on the cellular automata technique that is integrated into the popular—SIMPLER algorithm for CFD problems. In the model, the cellular automata technique deals with the microscopic non-linear dynamic interactions of bubbles while the traditional CFD algorithm is used to determine macroscopic system parameters such as pressure and temperature. The popular SIMPLER algorithm is employed for the CFD treatment. The model is then employed to simulate a pool boiling process. The computational results show that the CAS model can reproduce most of the basic features of boiling and capture the fundamental characteristics of boiling phenomena. The heat transfer coefficient predicted by the CAS model is in excellent agreement with the experimental data and existing empirical correlations.

The Formation of Banded Condensate Films in Weak Ammonia–Water Mixtures

2011 ◽  
Vol 133 (10) ◽  
Author(s):  
Joe Deans ◽  
Serhan Kucuka
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Fraction ◽  
Analytical Study ◽  
Horizontal Tube ◽  
Step Change ◽  
Force Balance ◽  
Tube Surface ◽  
The Heat Transfer Coefficient

This experimental and analytical study focuses on the formation of banded condensate films on a horizontal tube, when the ammonia mass fraction of the vapor is less than 0.0126. The experimental results show that there is a step change in the heat transfer coefficient when a banded film is formed. This change develops when the vapor mass fraction is approximately 0.004 and the heat transfer coefficient at the end of the change is 15% greater than the value expected for steam. The banded films are initiated at the base of the tube; midway between the regions where droplets detach. Photographs taken during the tests show that the development starts with the formation of a single band; when this band is complete, secondary bands are formed on either side and then further bands are added until the complete tube surface is covered with a banded film. The reason for the delay in the formation of the bands is examined using a simple two-dimensional force balance. The success of this examination provides an insight to the mechanisms employed in the formation of banded films.

Inverse analysis for the determination of heat transfer coefficient

2013 ◽  
Vol 91 (12) ◽  
pp. 1034-1043 ◽  
Author(s):  
Ali Fguiri ◽  
Naouel Daouas ◽  
M-Sassi Radhouani ◽  
Habib Ben Aissia
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Source Strength ◽  
Hot Wire ◽  
Source Power ◽  
Heating Source ◽  
The Heat Transfer Coefficient

The parallel hot wire technique is considered an effective and accurate means of experimental measurement of thermal conductivity. However, the assumptions of infinite medium and ideal infinitely thin and long heat source lead to some restrictions in the applicability of this technique. To make an effective experiment design, a numerical analysis should be carried out a priori, which requires a precise specification of the heating source strength and the heat transfer coefficient on the external surface. In this work, a more accurate physical and mathematical modeling of an experimental setup based on the parallel hot wire method is considered to estimate the two above-mentioned parameters from noisy temperature histories measured inside the material. Based on a sensitivity analysis, the heating source strength is estimated first using early time measurements. With such estimated value, determination of the heat transfer coefficient using temperatures measured at later times is then considered. The Levenberg–Marquardt (LM) method is successfully applied using a single experiment for the inverse solution of the two present parameter estimation problems. Estimates of this gradient-based deterministic method are validated with a stochastic method (Kalman filter). The effects of the measurement location, the heating duration, the measurement time step, and the LM parameter on the estimates and their associated confidence bounds are investigated. Used in the traditional fitting procedure of the parallel hot wire technique, the estimated heating source power provides a reasonable agreement between fitted and exact values of the thermal conductivity and the thermal diffusivity.

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