How Do Marine Refrigeration Systems Work?

Properly functioning refrigeration equipment is a necessity in any environment that may be inhabited for an extended period of time. Through access to adequate cooling measures, food spoilage may be delayed by slowing the growth of pathogenic bacteria. While most land-based facilities contain large refrigeration units, it is generally more challenging to set up and maintain the same in aircraft and ships. Due to the reduction in space and lack of access to power grids, aircraft and marine-based refrigeration units must be explicitly designed with these variables in mind. In this blog, we will discuss everything you need to know about marine refrigeration, including its various components and their nuances.

Marine refrigeration systems contain many of the same elements found in a standard refrigerator, including a compressor, condenser, and refrigerant. The compressor acts as a pump for the refrigerant and carries the critical responsibility of modulating the pressure and temperature of the refrigerant as it makes its way through the refrigeration cycle. A marine compressor has two sides that perform inverse functions. The discharge side provides the condenser with refrigerant under high pressure, while the suction side receives refrigerant from the evaporator in order to return it to the compressor.

Refrigerant is sold and installed as a gas, and it exists in this form until it enters the condenser. Before condensing, the compressor increases the pressure of the refrigerant to pressures of around 100-150 pounds per square inch (psi). Since pressure and temperature share a linear relationship, the refrigerant's temperature will also increase during this phase of the cycle. After entering the condenser, the refrigerant is cooled by air or water and converted into a liquid. During this transition, the liquid maintains its high pressure, which is necessary when entering the evaporator.

When entering the evaporator, the high-pressure refrigerant maintains a very low boiling temperature. Freon, which is the most commonly employed refrigerant among all refrigeration systems, has a boiling point of -21.64 degrees Fahrenheit. As the refrigerant boils and returns to a gaseous state, the refrigeration box is rapidly and significantly cooled. This step in the refrigeration cycle is the cooling source for the contained items. Marine refrigeration systems can get as cold, if not colder, than household refrigerators. The temperature of the system is controlled by a thermostat, which may be found either externally or inside the unit. Some systems also feature the ability to produce ice from the evaporator unit.

As an alternative to evaporators, some marine refrigerators may also use holding plates to cool refrigeration boxes. These plates are more power-efficient on average, only needing to be recharged once or twice per day. This may either come from the ship's battery, generator, or shore power line. Unlike evaporators, which rely on the low boiling point of the refrigerant, holding plates contain a liquid that freezes under 23 degrees Fahrenheit. The plates freeze as refrigerant passes through and is then thawed using the heat pulled from the refrigeration box. At this time, the compressor is turned off in order to save energy and money.

Out of the various refrigeration system components, none require more energy than the compressor. When considering different power delivery options, it is essential to take into consideration what type of energy source is most commonly relied upon. For example, if one typically relies upon generator energy to power their onboard appliances, then it is wise to install an AC-compatible refrigeration system. Conversely, those dependent on shore or engine power may consider a DC system instead. However, it is important to remember that DC systems take much longer to recharge, particularly on shore power.

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1. mitchel stark
2. Posted on May 5, 2022
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