Hi, please Look this photo. It is evident that the cold is concentrated in the element resting on the pipe. Unless the tube has another tube inside...how does that work? Carnot cycle needs two pipes, one for high and one for low pressure.

 

It's freezing water in the pipe by each device to create an ice plug its vicinity so the pipe section in the middle can be cut out for repair.

 

I know what is doing this machine. I'm asking about the rubber black hose. This machine is working with r134 or similar gas. It's a fridge. Inside the black hose is there an other hose?

 

I see what you are asking: where is the Freon return hose?

Good question. Most likely, as you mentioned, it is a coaxial hose.