Question 41 1AE01 - First Assistant Engineer

The Correct Answer is A. **Explanation of why Option A is correct:** 1. **Residence Time and Oil Level:** Residence time is the average time a fluid particle spends within a specific volume (the reservoir/sump). It is calculated as the volume of the reservoir divided by the flow rate (Volume/Flow Rate). If the flow rate required by the lubrication system is constant, increasing the oil level (which increases the total volume of oil in the reservoir) directly increases the residence time. A longer residence time means the oil spends more time in the reservoir. 2. **Cooling Effect:** The primary functions of a lube oil reservoir/sump, besides storage, include allowing time for contaminants (like air and water) to separate and, crucially, allowing the oil to dissipate heat. The reservoir walls and the surface area exposed to the surrounding environment act as a heat exchanger. When the residence time is longer, the oil has more time to transfer heat to the environment before being recirculated back into the system by the pump. Therefore, a longer residence time leads to cooler oil being delivered by the pump. **Explanation of why the other options are incorrect:** * **B) The higher the oil level, the shorter the residence time, and the cooler the oil will be as delivered by the pump.** This is incorrect because a higher oil level means a larger volume, which results in a **longer** residence time (assuming constant flow rate). While the second part (cooler oil) is correct, the first premise is false. * **C) The higher the oil level, the longer the residence time, and the hotter the oil will be as delivered by the pump.** This is incorrect because while the first premise (longer residence time) is true, the conclusion regarding temperature is false. Longer residence time allows for greater heat dissipation, resulting in **cooler**, not hotter, oil. * **D) The higher the oil level, the shorter the residence time, and the hotter the oil will be as delivered by the pump.** This is incorrect. Both premises are false: a higher oil level results in **longer** residence time, and longer residence time results in **cooler** oil.