RSW System

On a working vessel, heat can build up quickly. Refrigeration systems, machinery, onboard processing equipment and freshly caught fish all have different cooling requirements. At sea, where space is limited and the environment is exposed to salt, humidity and vibration, maintaining reliable cooling requires more than installing a standard industrial chiller.   A marine chiller is designed to remove heat under shipboard operating conditions. Depending on the application, it may supply chilled water to equipment or cool circulating seawater in a refrigerated seawater (RSW) system used to preserve fish after catching. Understanding how these systems work helps shipbuilders and vessel operators choose suitable equipment.   Table of Contents Quick Answer Key Takeaways How Does a Marine Chiller Work? What Does a Marine Chiller Cool? Why Marine Chillers Need Specialized Design How to Select the Right Marine Chiller Real Customer Experience: A Fishing Vessel Project in the Maldives FAQ Conclusion   Quick Answer A marine chiller keeps shipboard equipment cool by absorbing heat from a circulating cooling medium and transferring that heat through the refrigeration system to a condenser. Depending on its design, the condenser may reject heat through seawater or another suitable cooling arrangement.   For fishing vessels, a marine chiller can also cool recirculating seawater in an RSW system. The chilled water circulates through fish storage tanks, helping remove heat from the catch and maintain suitable storage conditions during the voyage.   Key Takeaways Marine chillers remove heat from equipment or process fluids through a refrigeration cycle. RSW systems circulate chilled seawater through fish storage tanks to help preserve the catch. Saltwater corrosion, humidity, vibration, limited installation space and onboard power conditions affect equipment selection. Cooling capacity should be calculated using the real heat load and operating conditions, not horsepower alone. Regular inspection of heat exchangers, electrical connections, piping and cooling performance helps improve reliability at sea.   How Does a Marine Chiller Work? The basic refrigeration cycle of a marine chiller is similar to that of an industrial chiller. The compressor raises the pressure and temperature of the refrigerant vapor. The condenser then releases heat, allowing the refrigerant to condense into liquid. After passing through an expansion device, the refrigerant enters the evaporator, where it absorbs heat from the water or other cooling medium.   The cooled medium is then circulated to the equipment or storage system that needs cooling. As it absorbs heat, it returns to the chiller to be cooled again.   In an RSW system, seawater is circulated through the chiller and then distributed through the fish tank. The water absorbs heat from the catch and returns to the refrigeration system. This continuous circulation helps cool the fish more evenly than simply placing the catch in an uncooled storage space.   Hengde Insight：A marine chiller should be evaluated as part of the complete cooling system, not as an isolated machine. Even a correctly sized chiller may struggle if the circulation pump, tank layout, piping or heat exchanger is unsuitable for the vessel's actual operating conditions.   What Does a Marine Chiller Cool? The application determines how the marine chiller should be configured. On fishing vessels, one important use is maintaining the temperature of the water surrounding the catch. Rapidly removing heat helps preserve fish quality during storage and transportation, although the final result also depends on loading practices, fish quantity, tank design and operating procedures.   Marine chillers may also serve cooling duties for compatible onboard machinery or processing equipment. For these applications, engineers must confirm the required fluid temperature, heat load, circulation flow and acceptable temperature variation.   It is important to distinguish between an RSW chiller and a general-purpose marine equipment-cooling system. They may use similar refrigeration principles, but their flow arrangements, heat exchangers, control settings and operating requirements can be different.   Why Marine Chillers Need Specialized Design？ A vessel presents operating conditions that are different from those of a typical factory. Seawater can accelerate corrosion when unsuitable materials are used. High humidity can affect electrical components, while vibration and vessel movement place additional demands on mounting arrangements and piping connections.   Space and weight also matter. Equipment must fit within the vessel's layout without obstructing maintenance access or interfering with other onboard systems.   When evaluating a marine chiller, shipbuilders should consider: Corrosion resistance: Heat-exchanger materials and protective measures must suit the seawater exposure and operating environment. Compact construction: Dimensions and service clearances should match the available installation space. Electrical compatibility: Voltage, frequency, starting current and protection requirements must match the vessel's power supply. Stable control: Temperature sensors and control functions should suit the cooling load and operating cycle. Maintainability: Filters, pumps, electrical components and heat exchangers should be accessible for inspection and servicing.   Hengde Insight：Marine reliability is not determined by the compressor alone. The components most exposed to seawater, moisture and vibration deserve equal attention during equipment selection. A design that is easy to inspect and maintain can be especially valuable when a vessel is operating far from shore.   How to Select the Right Marine Chiller？ Before requesting a quotation, shipbuilders or vessel operators should provide the supplier with enough information to assess the real cooling requirement. Application: fish preservation, onboard processing or equipment cooling Required cooling capacity and target water temperature Water flow rate and inlet temperature Seawater conditions and expected operating environment Available installation dimensions and maintenance space Vessel power supply, voltage and frequency Expected operating hours and ambient conditions   For an RSW system, the amount of fish loaded, initial catch temperature, tank volume, loading rate and desired cooling time are particularly important. A supplier can use these details to estimate the required cooling capacity and circulation arrangement.   Do not select a unit based on horsepower alone. Cooling capacity can change with operating temperatures and design conditions, so the performance data should be checked at the conditions relevant to the project.   Real Customer Experience: A Fishing Vessel Project in the Maldives Several years ago, a marine shipyard in the Maldives contacted Hengde after receiving feedback from its customers about a practical problem: their fishing vessels lacked suitable refrigeration equipment, and fish caught during voyages were suffering from inadequate temperature management.   The shipyard wanted a solution that could help maintain appropriate water temperatures after the catch was brought onboard. Hengde supplied marine seawater chillers for the application. Following installation, the customer reported that the system helped maintain the water temperature and preserve the freshness of the catch.   The cooperation did not end with the initial order. Satisfied with the equipment's performance, the customer developed a long-term relationship with Hengde and has continued ordering marine chillers year after year. The customer is now developing a new shipbuilding facility and plans to equip subsequent vessels with Hengde marine chillers.   This experience highlights an important point for shipbuilders: cooling equipment should be selected around the vessel's actual operating needs. Suitable heat-exchanger materials, reliable circulation and appropriate temperature control all contribute to a practical onboard solution.   For reference, Hengde's HY-15W marine seawater chiller is a 15 HP model designed for marine applications. Its published product information describes corrosion-resistant heat-exchanger options and centralized control functions. The final configuration should always be confirmed against the vessel's cooling requirements and seawater conditions.   FAQ 1. Can a marine chiller use seawater to reject heat? Yes. Some marine chillers use seawater-side condensers designed with suitable corrosion-resistant materials. The material selection and system configuration should match the seawater conditions and the manufacturer's specifications. 2. How does an RSW chiller keep fish fresh? An RSW system cools circulating seawater and distributes it through the fish storage tank. The chilled water removes heat from the catch, helping maintain suitable storage conditions during the voyage. 3. Can an ordinary industrial chiller be installed on a fishing vessel? Not every industrial chiller is suitable for marine service. Corrosion exposure, vibration, humidity, space, electrical supply and applicable vessel requirements should be reviewed before selecting equipment. 4. How often should a marine chiller be maintained? Maintenance frequency depends on operating hours, seawater quality and vessel conditions. Operators should follow the manufacturer's instructions and regularly inspect heat exchangers, piping, electrical connections, protective devices and cooling performance.   Conclusion A marine chiller keeps shipboard equipment or stored catch cool by transferring heat through a refrigeration cycle. However, dependable marine cooling requires more than sufficient nominal capacity. Corrosion resistance, circulation design, temperature control, installation space and maintenance access all influence performance over the vessel's service life.   Hengde is an industrial temperature-control equipment manufacturer established in 2010, with a 15,000 m² facility and more than 150 employees. Its product range includes marine chillers and seawater cooling solutions for fishing vessels. Through application-based equipment selection and ongoing cooperation with repeat customers, Hengde helps shipbuilders evaluate cooling solutions suited to their vessel layouts and operating requirements. If you are planning a new fishing vessel or upgrading an existing boat, share your cooling capacity, target temperature, water flow and onboard power details with Hengde to discuss a suitable marine chiller configuration.   ↑ Back to Top