Principles of refrigeration systems

For low-pressure steam to turn into a low-pressure, low-temperature liquid, heat must be released; a refrigerant is also required in this process. However, the cost of using a refrigerant is too high. The process you described above can use water as a coolant. This is just my personal guess – it’s mainly because it’s more economical and saves money

Can’t water be used as a coolant in the process I described? What is the temperature of the low-pressure steam?

Refrigerant → Low-pressure vapor (at the inlet of the refrigerant compressor) → High-temperature, high-pressure vapor (at the outlet of the refrigerant compressor; the gas is compressed and its temperature rises) → High-pressure, low-temperature liquid (the compressed gas passes through a cooler and turns into a liquid) → Low-pressure, low-temperature liquid (the high-pressure, low-temperature liquid from the previous step passes through a throttle valve, where it expands and vaporizes to do work; since no external energy is supplied, its own energy decreases, resulting in a drop in temperature. This process is the core element in refrigeration technology!) )

Thank you for your answer. I understand this process clearly. What puzzles me is why not simply use cold water to cool the low-pressure steam? Won’t that omit so many intermediate steps? Is it impossible to reach the heat exchange temperature? What is the temperature of this low-pressure steam?

Throttling effect occurs only when there is a transition from high pressure to low pressure; the temperature is around thirty to forty degrees

Cold water is used to directly cool the low-pressure steam; what is the temperature of the cold water? What is the cooling temperature you need? Suppose the temperature you need after cooling is -10 degrees, and the temperature of your cold water must be at least -15 degrees; this represents a significant temperature difference that ensures good heat exchange. The question is: where does this cold water come from?

Refrigerant → Low-pressure vapor → High-temperature, high-pressure vapor → High-pressure, low-temperature liquid → Low-pressure, low-temperature liquid. You are confusing the “low pressure” of the low-pressure vapor with that of the low-pressure, low-temperature liquid; this shows that you don’t really understand the principle of refrigerators at all… The refrigerant absorbs heat and evaporates (its vapor pressure is low compared to the pressure after compression by the compressor). The refrigerant vapor, after being compressed, absorbs the heat generated by the compressor and turns into a high-temperature, high-pressure gas. This high-temperature, high-pressure gas loses the heat generated by compression as well as the heat associated with phase change through outdoor water-cooling or air-cooling systems. As a result of this heat loss, it transforms into a high-pressure, low-temperature liquid. When this liquid passes through a throttle valve, it is slowly released, turning into a low-pressure liquid – at this point it absorbs heat from the surroundings and transforms back into a gas； What you’re referring to – changing directly from low-pressure steam cooled state to a low-pressure, low-temperature liquid state – requires you to understand phase transitions further!

Uh, thank you! I’ll study it more carefully