Etiket Arşivleri: steady-state

Heat Exchanger Design

Considering the heat exchanger given in the figure the continuous, steady-state heat duty is given by,

Q=m (Hout-Hin)

where

Q is the heat duty (rate of heat transfer)

m is the flow rate of the stream (mass or molar)

Hin is the enthalpy of the stream entering (per unit mass or mole)

Hout is the enthalpy of the stream leaving (per unit mass or mole)

●Heat is transferred to or from process streams using other process streams or “heat transfer media”. In a heat exchanger design, every effort is made to exchange heat between process streams and thereby minimize the use of heat transfer media (referred to as utilities).

●Heat transfer media are classified as “coolants (heat sinks)” when heat is transferred to them from process streams, and as “heat sources” when heat is transferred from them to process

Laboratory‎ > ‎Chemical Kinetics

The detailed explanation at the molecular level how a reaction proceeds is called reaction mechanism. The explanation is given in some elementary steps. Devising reaction mechanisms requires a broad understanding of properties of reactants and products, and this is a skill for matured chemists. However, first year chemistry students are often given a mechanism, and be asked to derive the rate law from the proposed mechanism. The steady-state approximations is a technique for deriving a rate law from the proposed mechanism.

Chapter-6: Block Diagrams and Linearization

Example:

Consider the stirred tank blending process.

Control objective: regulate the tank composition x, by adjusting w2.

Disturbance variable: inlet composition x1

Assumptions:

w1 is constant

System is initially at steady-state

Both feed and output compositions are dilute

Feed flow rate is constant

Stream 2 is pure material