🔍 Key Concepts

• Function of a double trunk piston in a refrigeration compressor • How refrigerant and lubricating oil behave together in a crankcase • Causes of oil foaming when a compressor starts or runs

💭 Think About

• Ask yourself: What specifically makes oil foam when refrigerant is dissolved in it, and what design change would reduce that interaction? • Consider whether higher pressure, higher efficiency, or reduced contact between fluids would directly affect foaming in the crankcase. • Think about what a shaft seal does—does removing it have any logical connection to foam formation in the crankcase?

✅ Before You Answer

• Which choice directly addresses refrigerant–oil contact in the crankcase rather than general compressor performance? • Eliminate any options that talk about efficiency or pressure but do not clearly relate to foaming behavior. • Confirm which option describes a design feature that would physically separate or limit mixing of refrigerant and oil.