# Thermodynamics - evaporator condenser

• James MEng
In summary, the conversation discusses a question regarding a multiple effect evaporator with condenser. The question is about how increasing the flow of cooling water to the condenser will affect the pressure in the condenser and the entire evaporator. The understanding is that the overall heat transfer coefficient will increase, the cooling water temperature will decrease, and the mass flow rate of condensate will remain the same. The question is then raised about how this will lead to a reduction in evaporator pressure. The person is looking for a basic explanation of the physical process rather than just formulas.
James MEng
Hello - fundamental thermo question which is puzzling me...

It concerns a multiple effect evaporator with condenser. Hot vapour is water, cooling medium is water.

My question stems from the following:
When the flow of cooling water to the condenser is increased, the pressure in the condenser (and thus the pressure profile of the entire evaporator) is reduced.

Here's how I understand it...

• Heat transfer area of condenser remains constant
• Overall heat transfer coefficient is increased slightly; given that the Reynolds number on cold side is increased
• Cooling water temperature out is reduced (assuming heat load is constant and inlet temperature is the same)

How does this in turn lead to a reduction in evaporator pressure, please explain in basic terms (what's actually physically happening rather than just formulae! :thumbs:).

Thanks in advance for any replies

Edit: Also the mass flow rate of condensate will be the same for a given flow "in" of water and steam. Some thermodynamic activity is occurring here I just cannot work out what!

Last edited:
I'm wondering where it said that the outlet pressure from the condenser would be decreased. This doesn't seem reasonable to me.

## What is an evaporator?

An evaporator is a component in a refrigeration system that absorbs heat from the surrounding environment, causing a refrigerant liquid to evaporate and turn into a vapor.

## What is a condenser?

A condenser is a component in a refrigeration system that removes heat from the refrigerant vapor and turns it back into a liquid form.

## How do evaporators and condensers work together?

Evaporators and condensers work together to transfer heat and change the state of the refrigerant in a refrigeration system. The evaporator absorbs heat from the environment, causing the refrigerant to evaporate. The vapor then travels to the condenser, where it is cooled and turned back into a liquid. This process repeats to maintain a consistent temperature in the refrigeration system.

## What types of refrigerants can be used in evaporators and condensers?

There are various types of refrigerants that can be used in evaporators and condensers, including ammonia, carbon dioxide, and hydrofluorocarbons (HFCs). The type of refrigerant used depends on the specific application and environmental considerations.

## What factors affect the efficiency of evaporators and condensers?

The efficiency of evaporators and condensers is affected by factors such as the design and size of the components, the type of refrigerant used, and the temperature and pressure conditions in the system. Proper maintenance and regular cleaning can also impact the efficiency of these components.

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