Question 59 3AE02 - Third Assistant Engineer (Alt)

The Correct Answer is C ### Explanation of Why Option C is Correct Liquid cargo-hold dehumidification systems (often using a chemical absorbent, like a desiccant rotor/wheel) operate by continuously drying the air circulating through the cargo hold and then regenerating the chemical desiccant material using outside air. 1. **Cargo-Hold Air Processing (Dehumidification):** The air drawn from the cargo hold needs to be dried. In a typical desiccant system (which is what this question implies by mentioning regeneration and humidification/dehumidification chambers), the air is usually cooled *before* passing through the desiccant wheel (or sometimes cooled after) to improve efficiency or control temperature. The chamber/section where the cargo-hold air is processed to remove moisture and condition it for return is correctly termed the **dehumidification chamber** (or drying sector). It contains a **cooling coil** to manage the thermal load and/or pre-treat the air before drying. 2. **Outside Air Processing (Regeneration):** The desiccant material (e.g., the rotor) absorbs moisture from the cargo-hold air and must be dried (regenerated) so it can absorb moisture again. This is achieved by passing hot air through the regeneration section of the rotor. This hot air is typically heated outside air. Therefore, the chamber that processes the outside air contains the **heating coil** and is correctly known as the **regeneration chamber**. Thus, Option C accurately describes the functions and components of the two main process streams: * Cargo-hold air $\rightarrow$ Cooling coil $\rightarrow$ Dehumidification chamber. * Outside air $\rightarrow$ Heating coil $\rightarrow$ Regeneration chamber. ### Explanation of Why Other Options are Incorrect **A) Incorrect:** This option incorrectly assigns the names and components. It claims the cargo-hold air chamber is the "regeneration chamber" (it should be the dehumidification chamber) and contains the cooling coil (which is plausible but misnamed). Crucially, it claims the outside air chamber is the "dehumidification chamber" (it should be the regeneration chamber) and contains the heating coil (which is plausible but misnamed). **B) Incorrect:** This option reverses the coils and the names. It states the cargo-hold air chamber (dehumidification) contains the heating coil (it typically contains the cooling coil, or occasionally a post-heating coil). It states the outside air chamber (regeneration) contains the cooling coil (it must contain the heating coil for regeneration). **D) Incorrect:** This option assigns the cooling function to the outside air chamber and the heating function to the cargo-hold air chamber, which is functionally opposite to how a typical liquid cargo-hold dehumidifier regenerates the desiccant. The outside air must be heated for regeneration, and the cargo-hold air is processed for dehumidification (usually involving cooling). Furthermore, it incorrectly names the outside air chamber the "dehumidification chamber" and the cargo-hold air chamber the "regeneration chamber."