Here's my reading of it as a non-expert. The tubing isn't pinched shut, it's just pinched to restrict the flow. I believe it's to create a bottleneck where pre

Here's my reading of it as a non-expert. The tubing isn't pinched shut, it's just pinched to restrict the flow. I believe it's to create a bottleneck where pressure can build up between the "hot side" and the "cold side" of the refrigerator. Before the pinch the compressor is driving gas into the pipe, where it meets resistance at the pinch point and compresses to liquid, shedding heat. Then after that point a narrow jet of compressed refrigerant squirts into a lower pressure part of the pipe and starts to evaporate, expanding and taking in thermal energy again. Of course, the refrigerator already has some valve to do this, but the author mentions that it may not be designed for the pressure differential needed for propane, so you can make your own with a pinched tube.