The JW range of Heat Recovery Evaporators have been specifically designed to utilise the waste heat available in the cooling water systems of a ship’s main propulsion or auxiliary diesel engines, for the conversion of seawater into fresh water. The production of fresh water on-board reduces the required fresh water storage capacity and increases the fuel or cargo capacity of ocean-going vessels. JW Evaporators are available in a standard range of single effect units with fresh water capacity ranging from 1 m3/day up to 70 m3/day. For higher capacities units are specifically designed, with double and triple effect designs as an option for the utilisation of limited waste heat.

Features of JW Evaporators

• Low Installation Costs - Factory assembled unit on single baseframe for simple low cost installation.
• Reduced Space Requirements - Internal design and construction provides compact arrangement.
• Low Operating Costs - Electrical power only for pump motors.
• Reliability - High quality materials of construction for long-term reliability and availability.
• Ease Of Operation - Simple manual start-up to full output operation, with automatic control of fresh water salinity.
• Fresh Water Quality - High quality fresh water production, suitable for all on-board domestic and technical uses.
• Low Maintenance Costs - Low evaporating temperature and low brine concentration for extended scale free operation.
• Ease Of Maintenance - Both condenser and heater tube bundles can be removed from the front of the unit.

Stand-by Heating - Suitable for operation with steam as an alternative heating medium when engine waste heat is not available. When seawater is boiled in a vacuum chamber, vapour can be produced at temperatures as low as 40°C, and it is this principle of low temperature evaporation which is applied for the production of fresh water from seawater, utilising a source of low grade heat to promote the boiling action. In the JW Evaporator, cooling seawater is circulated through the tubes of the condenser bundle and then returned to the ship’s main or discharged overboard. A controlled quantity of the pre-heated seawater from the condenser outlet is continuously diverted into the bottom of the evaporator shell as feed water. Approximately one third of this feed water is evaporated, the remainder being continuously discharged in order to control the brine density. The feed water level and discharge rate is maintained constant by a fixed brine weir. The low grade heating medium is the waste heat in the fresh water cooling system of the ship’s engines. The hot engine jacket water is circulated through the tubes of the submerged heater/evaporator bundle, reducing in temperature by 5 to 10°C, before returning to the engine system. This heat boils the seawater in the evaporator shell, and pure water vapour is produced. This vapour rises through a demister, which removes any entrained droplets of seawater, and then passes into the condensing section. The vapour condenses on the outside surface of the tubes, and collects in a tray, from where it is extracted and pumped to storage. The vacuum in the evaporator shell is produced and maintained by a seawater-operated air ejector, and excess seawater is extracted and discharged by a seawater-operated brine ejector. The motive seawater for the ejectors is provided by a centrifugal pump, which takes its supply from the condenser outlet or from a separate source. The JW Evaporator is supplied as a package unit on a single baseframe, and the scope of supply includes the ejectors and seawater supply pumpset, distillate pumpset, instrumentation, automatic dump system for impure distillate, control panel, piping and valves. Total Service We provide a complete in-house engineering service, from preliminary design studies, followed by comprehensive specification and quotations, technical and commercial consultation, through to fully detailed design, manufacture and testing. After-sales service includes technical assistance for supervision of installation, start-up and commissioning during harbour and sea trials, and operator training. Multi Effect The higher efficiency double and triple effect evaporators are available for applications where the quantity of waste heat is limited, particularly for higher fresh water capacities, up to 300 m3/day. Heat consumption of the double effect JW evaporator is approximately 16 kW per m3/24 hours fresh water output. Heat consumption of the triple effect JW evaporator is approximately 11 kW per m3/24 hours fresh water output. The higher efficiency of the multi-effect evaporators is achieved by utilising the pure water vapour produced in one effect as the heating medium for the next effect. The vapour condenses into fresh water inside the heater tubes, transferring its latent heat to the seawater in the evaporator shell. Testing Every JW Evaporator is subjected to full hydrostatic tests during manufacture, to ensure the integrity of shell, tubes, waterboxes and pipework. On request, or if required by the specification, we can conduct equipment function tests and fully simulated evaporator performance tests in our modern and fully equipped factory test facility. These tests can be witnessed by the client and representatives of the appropriate Classification Society, e.g. LRS, DNV, ABS, RINA, etc.

info.power@glv.com