Final answer:
The device in a refrigeration system that converts a low pressure vapor into a high pressure vapor is the compressor, which raises the gas temperature and pressure before it condenses back to liquid.
Step-by-step explanation:
In a refrigeration system, the device that changes a low pressure vapor into a high pressure vapor is the compressor. The electrically driven compressor inputs work (W), thereby increasing both the temperature and pressure of the refrigerant gas. This process forces the gas into the condenser coils, which are located inside the heated space. As the gas temperature is higher than the room's temperature, there is a heat transfer from the gas to the room. Consequently, the gas condenses and turns into a liquid. After this phase change, the liquid refrigerant travels through a pressure-reducing valve back to the outdoor evaporator coils. Here it undergoes cooling through expansion, thus restarting the cycle.
It's important to understand that in the cooling cycle, the evaporator and condenser coils switch roles, and the fluid flows in the reverse direction. The work done by the compressor, which we pay for in our electricity bill, is an essential aspect of the refrigeration cycle because it moves the coolant through the coils.