Why is the multiple-effect evaporator more economical than single effect?

Multiple effect evaporators have higher economy but lower capacity than single effect. If the feed is cold (below boiling) some of the heat going into the evaporator must be used to raise the feed to boiling before evaporation can begin; this reduces the capacity.

What is economy of an evaporator can single effect evaporator have an economy more than 1.0 justify your answer?

For single effect evaporator, the steam economy is about 0.8 (<1). The capacity is about n-times that of a single effect evaporator and the economy is about 0.8n for a n-effect evaporators.

What is the advantage of multiple-effect evaporator?

Major Advantages of RDG Multi-effect systems: Reduced energy required to run full system. Reduced condensing load with additional effects (less cooling water needed) Liquor flow control. Convenient foul condensate collection and processing.

How can you increase the efficiency of a multiple-effect evaporator?

Diagnosis involves leakage detection in MEE by vacuum testing and hydro testing followed by high pressure cleaning along with chemical cleaning to remove the scaling in the evaporator which will improve the efficiency of the MEE.

What is the economy of multi effect evaporator?

Wrapping up. The primary means of increasing the steam economy of an evaporator is to reuse the latent heat of the water vapor. A multiple-effect evaporator uses the water vapor from one effect as the heating medium for the next effect, which operates at a lower boiling point.

What are the disadvantages of multiple effect evaporator?

Disadvantages are:

• high head-room requirements.
• higher pressure drop through the tubes than in a falling film evaporator.
• hydrostatic head at the bottom of the tubes may increase product temperature and cause temperature-sensitivity problems.

What is the economy of an evaporator?

Economy of evaporator Economy (or steam economy) is the number kilogram of water vaporized from all the effects per kilogram of steam used. • Economy is the number of kg of water vaporized per kg of steam fed to the unit.

What is the disadvantage of a multiple effect evaporator?

Disadvantages are: high head-room requirements. higher pressure drop through the tubes than in a falling film evaporator. hydrostatic head at the bottom of the tubes may increase product temperature and cause temperature-sensitivity problems.

Why do we use more than one evaporators in series?

Heat Transfer Operations Questions and Answers – Evaporators – Multiple Effect Evaporators. Because the boiling temperature of water decreases as pressure decreases, the setups are so made to allow us to use the superheat of one of the setup to heat the subsequent ones.

How many evaporators are attached in multiple effect evaporator?

It is suitable for large-scale and continuous operations. It is highly economical when compared with a single effect. About 5 evaporators can be attached.

In which multi effect evaporator arrangement feed is introduced in every effect and steam is introduced in first effect?

1. Forward feed : In this arrangement, the thin liquid feed flows in the same direction as the vapour flow. Fresh feed enters the first effect and steam is also fed to a steam chest of the first effect.

How does a multiple-effect evaporator work?

Much of this latent heat, however, can be recovered and reused by employing a multiple – effect evaporator, that is, vapor from one effect serves as the heating medium for the next. The economy of the system, measured by the kilograms of water vaporized per kilogram of steam condensed, increases with the number of effects.

The key factor in determining the economy of an evaporator is the number of effects. The economy of a single effect evaporator is always less than 1.0. Multiple effect evaporators have higher economy but lower capacity than single effect.

How does multiple effect evaporation affect the economy?

The increase in latent heat with decreasing pressure and additional radiation losses affect , the economy as the number of evaporators used is increased. This method of evaporation in series is called multiple-effect evaporation, and each stage is called an effect. The amount of steam consumption in multiple effect…

How do you increase the steam economy of an evaporator?

The primary means of increasing the steam economy of an evaporator is to reuse the latent heat of the water vapor. A multiple-effect evaporator uses the water vapor from one effect as the heating medium for the next effect, which operates at a lower boiling point.