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Q8 (16 Marks) Refrigeration & Air Conditioning 🔥 Repeated 6x in exams
MEKG • Written Exam

With Respect to Container Ship:

(a) Sketch a ship's indirect refrigeration system arranged for cooling containers stowed in stacks in the hold:

(b) Describe the refrigeration system sketched in (a)

(c) State the advantages of the system described in (a) compared with containers with their own refrigeration self-contained units.

Appeared In: Aug 2025Feb 2021Jan 2020Aug 2019Jan 2019Nov 2022

✓ Verified Model Answer (Text Solution)

Structured for DG Shipping MEO Class II examination scoring criteria.

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Part (a)

A ship's indirect refrigeration system for cooling stacked containers in the hold utilizes a network of air trunking (ducts) integrated into the ship's structure. These ducts, guided by built-in rails, allow for flexible connections to the ship's central refrigeration plant via flexible ducting. Each container's connection point allows for the circulation of cooled air. Cooling is achieved either through brine-cooled air handlers (AHUs) or direct expansion (DX) units within the central refrigeration plant. A single AHU can effectively maintain the temperature of an entire stack of containers. Crucially, the system incorporates temperature monitoring of the return air from each container, allowing for precise control and adjustments. The brine circuit, if used, cools and maintains the temperature of the AHU, which itself is refrigerated by the ship's main refrigeration system. Variable-speed fans within the system adapt the airflow based on the heat load, optimizing energy consumption.

Part (b)

Advantages of Indirect Refrigeration Systems over Self-Contained Container Units

  • Eliminating the need for individual refrigeration units within each container significantly increases the ship's cargo capacity.
  • A centralized system simplifies maintenance procedures. Instead of numerous individual units requiring servicing, the focus is on a single, larger plant, resulting in reduced maintenance costs and downtime.
  • Centralized systems, with their optimized design and variable speed components, are typically more energy-efficient than a large number of independent units operating simultaneously.
  • The centralized control and monitoring offer better overall temperature regulation, minimizing the risk of temperature fluctuations that can damage sensitive goods.
  • A centralized system uses less gas as compared to a multitude of individual units, resulting in a more environmentally friendly operation.
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