Final answer:
CO2 would be on top in an evaporator due to volatility, with water vapor in the middle and oil at the bottom. In a recovery cylinder, oil would float on top of water due to being less dense, while liquid CO2, if present, would be at the bottom due to higher density.
Step-by-step explanation:
When considering the arrangement of CO2, water, and oil in different scenarios such as an evaporator or a recovery cylinder, their positions are determined by differences in their densities and states of matter.
In an evaporator, the most volatile substance with the lowest boiling point would be on top. In this case, CO2 (in its gaseous form) would be at the top, water vapor in the middle, and oil, which has a higher boiling point, would be at the bottom assuming all substances are in the vapor phase. However, generally in an evaporator setting, it is the water that is being evaporated, meaning the water would be in vapor at the top while oil and CO2 would remain below.
In a recovery cylinder, which is a container used to hold recovered refrigerant gases, the substances would be layered based on their densities in their condensed forms: oil, being less dense than water, would float on top of the water, while CO2, generally a gas at room temperature and pressure, would not be present unless it's under pressure in a liquid or supercritical state. If liquid CO2 is present, its density is higher than oil and water, and therefore, it would sink below both substances and be at the bottom of the cylinder.