scholarly journals Evaluation method of single blow experiment for the determination of heat transfer coefficient and dispersive Peclet number

2015 ◽  
Vol 36 (4) ◽  
pp. 3-24 ◽  
Author(s):  
Wilfried Roetzel ◽  
Chakkrit Na Ranong
Keyword(s):  
Heat Exchangers ◽  
Peclet Number ◽  
Numerical Evaluation ◽  
Evaluation Method ◽  
Dispersion Model ◽  
Tracer Experiment ◽  
Effective Number ◽  
Péclet Number ◽  
Modified Method

Abstract An evaluation method is developed for single blow experiments with liquids on heat exchangers. The method is based on the unity Mach number dispersion model. The evaluation of one experiment yields merely one equation for the two unknowns, the number of transfer units and the dispersive Peclet number. Calculations on an example confirm that one single blow test alone cannot provide reliable values of the unknowns. A second test with a liquid of differing heat capacity is required, or a tracer experiment for the measurement of the Peclet number. A modified method is developed for gases. One experiment yields the effective number of transfer units and approximate values of the two unknowns. The numerical evaluation of calculated experiments demonstrates the applicability of the evaluation methods.

scholarly journals Evaluation of resisdence time measurements on heat exchangers for the determination of dispersive Peclet numbers

2014 ◽  
Vol 35 (2) ◽  
pp. 103-115 ◽  
Author(s):  
Wilfried Roetzel ◽  
Chakkrit Na Ranong
Keyword(s):  
Heat Exchangers ◽  
Evaluation Method ◽  
Tube Bundle ◽  
Dispersion Model ◽  
Cascade Model ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Measured Input ◽  
Parabolic Dispersion

Abstract The recently developed special unity Mach number dispersion model prescribes the corrections to heat transfer coefficients which are simple functions of the dispersive Peclet numbers. They can be determined through the residence time measurements. An evaluation method is described in which the measured input and response concentration profiles are numerically Laplace transformed and evaluated in the frequency domain. A characteristic mean Peclet number is defined. The method is also applied to the parabolic dispersion model and the cascade model. A calculated example of a tube bundle with maldistribution and backflow demonstrates the suitability of the evaluation method.

Modelling of Flow of a Liquid in Apparatus with Mobile Packing: Dispersion Model

1993 ◽  
Vol 58 (9) ◽  
pp. 2047-2058
Author(s):  
Zdeněk Palatý
Keyword(s):  
Differential Equation ◽  
Numerical Integration ◽  
Residence Time ◽  
Mean Residence Time ◽  
Peclet Number ◽  
Dispersion Model ◽  
Tracer Concentration ◽  
Optimization Of Parameters ◽  
Determination Of Parameters

The paper deals with determination of parameters of a dispersion model used for describing the flow of liquid on a plate with mobile packing in the region of gas velocities up to 1.5 m s-1. The parameters of the model - the diffusion Peclet number and mean residence time of liquid - were determined from the nonideal input impulse of tracer concentration and its response by the method of numerical integration of differential equation with subsequent optimization of parameters. The results of measurements are presented graphically and in the form of criterion equations.

Hydrodynamic characterization in dissolved air flotation (DAF) contact zone

1998 ◽  
Vol 38 (6) ◽  
pp. 245-252 ◽  
Author(s):  
Ayman R. Shawwa ◽  
Daniel W. Smith
Keyword(s):  
Contact Zone ◽  
Peclet Number ◽  
Contact Time ◽  
Loading Rate ◽  
Dispersion Model ◽  
Dissolved Air Flotation ◽  
Péclet Number ◽  
Hydraulic Loading Rate ◽  
Hydraulic Loading ◽  
Recycle Ratio

The mechanism of bubble-floc interaction in a DAF contact zone is poorly understood and is usually described by conceptual models. This mechanism is highly dependent on the hydrodynamic conditions within the contact zone, i.e. contact time and degree of mixing. A pulse stimulus-response test was used to characterize the contact zone degree of mixing, in terms of dimensionless Peclet Number, and the contact time, in terms of residence time distribution. The tracer tests were performed at different hydraulic loading rates and recycle ratios. The experimental results confirmed that the axial dispersion model can be used to estimate the degree of mixing inside the contact zone. The results showed that the Peclet Number increased as the hydraulic loading rate increased, for all experiments performed under the same recycle ratio. In addition, the degree of mixing slightly increased as the recycle ratio increased, for all experiments performed under the same hydraulic loading rate.

scholarly journals Diffusion of single oxidation pond

2016 ◽  
Vol 20 (3) ◽  
pp. 849-853
Author(s):  
Ruo-Yuan Song ◽  
Yong-Fang Qian ◽  
Lai-Jiu Zheng ◽  
Yu-Ping Zhao ◽  
Xiao Wang ◽  
...  
Keyword(s):  
Empirical Formula ◽  
Peclet Number ◽  
Flow Reactor ◽  
Plug Flow ◽  
Tracer Experiment ◽  
Plug Flow Reactor ◽  
Hydraulic Characteristic ◽  
Longitudinal Diffusion ◽  
Oxidation Pond ◽  
Péclet Number

The hydraulic characteristic of an oxidation pond was studied by the tracer experiment, and an empirical formula of Peclet number was obtained, which can be well applied to the model of plug flow reactor with longitudinal diffusion.

Effect of Plate Characteristics on Axial Dispersion and Heat Transfer in Plate Heat Exchangers

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
K. Shaji ◽  
Sarit K. Das
Keyword(s):  
Heat Transfer ◽  
Nusselt Number ◽  
Heat Exchangers ◽  
Peclet Number ◽  
Axial Dispersion ◽  
Outlet Temperature ◽  
Plate Heat ◽  
Péclet Number ◽  
Back Mixing ◽  
Two Fluid

A new mathematical model of single-blow transient testing technique is proposed for the determination of heat transfer and dispersion coefficients in plate heat exchangers (PHEs) in which the flow maldisrtibution effects are separated from the fluid back-mixing. The fluid axial dispersion is used to characterize the back-mixing and other deviations from plug flow. Single-blow experiments are carried out with different number of plates for various flow rates with three different plate geometries of 30 deg, 60 deg, and mixed (30 deg/60 deg) chevron angles. The outlet temperature response to an exponential inlet temperature variation is solved numerically using finite difference method. In the present work, the whole curve matching technique is used to determine the values of Nusselt number and dispersive Peclet number. Since the maldistribution effects are separated, these data are independent of test conditions and hence using a regression analysis, general correlations are developed for Nusselt number and Peclet number of the present plate heat exchangers. The applicability of the single-blow test data is validated using a two-fluid experiment. Two-fluid experiments are conducted on the same plate heat exchanger with smaller and larger number of plates and the results have been compared with its simulation which used the Nusselt number and Peclet number correlations developed by the new model of single-blow test as the inputs.

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