The paper presents two methods that are aimed at detecting fouling in cross-flow heat exchangers under normal operating conditions, using measurements that can easily be obtained, i.e. inlet and outlet temperatures and the mass flows of the hot and cold fluids. The methods are a) a physical method that is based on number of transfer units (NTU) relations and b) a black box model that is estimat...

Two-dimensional numerical study of flow and temperature fields for laminar natural convection and radiation in the inclined cavity is performed in the present work. The walls of the square cavity are assumed kept at constant temperatures. An absorbing, emitting, and scattering gray medium is enclosed by the opaque and diffusely emitting walls. The set of governing equations, including conservat...

We show in this paper that the common method of specifying ∆Tmin in design of heat exchanger systems may lead to wrong decisions and should be used with care. Although specifying ∆Tmin is reasonable for heat exchanger networks synthesis with given stream data, it should not generally be used for obtaining optimal design data and especially not stream data (temperatures). An alternative simple T...

A method for deriving reduced dynamic models of one-dimensional distributed systems is presented. It inherits the concepts of the aggregated modeling method of Lévine and Rouchon originally derived for simple staged distillation models and can be applied to both spatially discrete and continuous systems. The method is based on partitioning the system into intervals of steady-state systems, whic...

In this work, we demonstrate the validity of the simplified spherical harmonics equations to approximate the more complicated equation of radiative transfer for modeling light propagation in biological tissue. We derive the simplified spherical harmonics equations up to order N = 7 for anisotropic scattering and partially reflective boundary conditions. We compare numerical results with diffusi...

In the presented research, heat transfer of a mobile electrolyte alkaline fuel cell (AFC) (which the electrolyte has cooling role of system) has been considered. Proper control volumes of system with specific qualification have been chosen. Consequently, heat and mass transfer in control volumes have been assessed. Considerations on them and contributed models lead to approve a double tube heat...

Transient phase change through a horizontal channel that subjected to discrete heat flux and filled with porous media of high-conductivity material, copper, is numerically investigated with n-pentane as the working fluid. The thermal non-equilibrium model is used in conjugate with the multiphase mixture model to analyze the transient behavior of fluid and solid phases. Three cases are studied r...

Transient phase change through a horizontal channel that subjected to discrete heat flux and filled with porous media of high-conductivity material, copper, is numerically investigated with n-pentane as the working fluid. The thermal non-equilibrium model is used in conjugate with the multiphase mixture model to analyze the transient behavior of fluid and solid phases. Three cases are studied r...

heat exchangers are one of the most important devices of mechanical systems in modernsociety. most industrial processes involve the transfer of heat and more often they requirethe heat transfer process to be controlled. a heat exchanger is the heat exchanged betweentwo media, one being cold and the other being hot. there are different types of heatexchanger, but the type which is widely used in...