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# Capillary tube

## Capillary tube

(OP)
Hi,

can you please ellaborate on topic of ordinary capillary tube

In particular, I am interested in bubble entering the tube

lukezo

### RE: Capillary tube

Get a copy of a thermodynamics textbook and look up the subject of refrigeration and air conditioning which will detail the function of capillary tubes and the analysis performed on capillary tubes.

### RE: Capillary tube

I suspect that your interest is in refrigeration and air conditioning equipment in which capillary tubes play an important function. Bubbles entering a capillary tube will be under high pressure and as the bubbles travel inside and exit the capillary tube, they will increase in size due to the pressure reduction and also the bubble temperature will get colder. When you study the relevant chapters in a thermodynamics text book you will come across terms such as enthalpy, entropy, quality, specific volume, saturated liquid and vapor lines, saturated and superheated region, and much more so be familiar with those terms. It is also important to study the Mollier diagram of the fluid in which the bubble appears and pay attention where on the Mollier diagram the attributes of the fluid travelling through the capillary tube are located.

### RE: Capillary tube

Just think about the difference between trying to drink milk vs. whipped cream through a straw.

### RE: Capillary tube

(OP)
What requires bigger pressure difference in your opinion?

I prefer tea

### RE: Capillary tube

The pressure drop determines the bubbliness.
The bubbliness determines the density.
The density determines the mass flow.
The mass flow determines the evaporator and condenser load.
Repeat.

### RE: Capillary tube

(OP)
I'm asking solely from capillary tube point of view as an element of cooling cycle

### RE: Capillary tube

(OP)
What requires bigger entry pressure? REfrigerant with bubble or with no bubble at all?

### RE: Capillary tube

What requires bigger entry pressure? REfrigerant with bubble or with no bubble at all?

It depends on the exit pressure.

Capillary tubes are all about pressure difference.

The refrigerant cycle is..... a cycle.

You need to think about it as a cycle. If you think about individual points in isolation you will fail to understand how it works.

### RE: Capillary tube

(OP)
The question refers to the change of condenser load. So if evaporator pressure and inlet and outlet stay same, how does subcool / bubble presence before capillary tube influence pressure of condenser? Obviously the pressure will change...

### RE: Capillary tube

It is impossible for some things to "stay same" while other things change within the refrigerant cycle.

Everything is connected. If one thing changes everything else must also change to maintain the overall system balance.

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