EN
Efficient cooling is the pulse of a marine propulsion system and auxiliary systems. Heat has to be rejected from main engine jacket water, charge air cooler, lubricating oil cooler, freshwater generator, and the shipboard cooling loops to the sea without jeopardizing essential setpoint temperatures under changing load conditions. Plate heat exchangers (PHE) are favored in such applications because of their space saving designs, performance characteristics and their ease of configuration.
Proper Sizing and Thermal Design Margins
When designing and installing a new ship the plate heat exchanger should not only consider the engine maker’s published data; but should always take in to consideration any additional marine margin that you know your service will produce over time. On any new build or renewal it will be recommended that a minimum of 10%-15% marine fouling margin be allocated to the plate heat exchanger that ensures design outlet temperatures are achieved from the new state throughout cleaning intervals when fouling develops. Approach Temperature; consider using a smaller approach that the higher performance requires but be mindful of the additional pump energy required. SME’s thermal engineers will model your total operating range from slow steaming at -5C sea temp up to full load at 35 deg C on the freshwater; to ensure the proposed PHE has been correctly dimensioned.
Optimizing Flow Distribution and Pressure Drop Management
It is crucial for the flow rates in both seawater and freshwater streams to be split equally across the entire complement of plates within a particular array of PHE plates in order to ensure that not every section of the PHE performs under ideal circumstances. The designer must also focus on establishing a flow regime that provides – on the seawater side of the arrangement – minimise pressure drop by ensuring an adequate design across number of passes and plates, while on the freshwater side a balance between promoting the performance of the heat transfer and ensuring a good approach temperature is needed. Monitoring the pressure drops on both sides of the PHE has become a method for proactive intervention of the cooling loops. SME’s teams regularly install permanently mounted, monitored pressure differential transmitters, enabling timely cleaning interventions.
Intelligent Control Strategies and Temperature Regulation
While control via a three-way by-pass valve works, it does often waste of valuable pumped energy. Variable flow control via the main pump with VSDs can enhance heat transfer on the PHE by maintaining sea flow speed throughout varying loads. This gives more effective heat transfer through all the plates as opposed to having to circulate all the cooled water through the bay of the cooling pump. Temperature sensors should be installed at the inlets and outlets for both fluids to provide accurate feedback loops in the vessel control system. SME are specialists in replacing outdated cooling control panels to more intelligent and automated solutions in conjunction with your VCU / Automation provider.
Maintenance Regimes and Fouling Mitigation
Without regular cleaning of a PHE, a marine-related cooling system will naturally reduce in performance and efficiency. The growth of the sea-side water within the PHE and the resultant foul will start insulating the heat transfer surface. Based upon actual monitoring results; an optimised maintenance cycle is planned rather than on a rigid calendar basis. Typically when the sea water side pressure drop rises to 20% above the clean value, or when the freshwater outlet temperature climbs by more than 2 °C at full load it's time to clean. If calcium scale has built up, a chemical in situ clean will typically remove this easily and efficiently, if some foreign matter has become trapped within the plates or if bio-fouling is persistent then high-pressure jet cleaning while disassembled will be required in a shipyard.
For ships experiencing repeated biofouling the installation of a MGPS could be a helpful solution. With cost-effective, safely, quickly and on-site worldwide at any yard time even while in operation (on-voyage), we make sure your ships keep running. Optimal cooling performance within your cooling loops for PHE is based on a balanced integrated approach – optimum system design, controlled processes, regular monitoring, solid maintenance concepts and deep knowledge of your vessels' operating characteristics. SEM Group's marine industry expertise dating back two decades and its global clientele-tens of thousands of ships and ships owners – are your partner to achieve more out of your cooling performance. Our staff is comprised of a team of 100+ specialist engineers, technician experts, supported by a 5,000 m workshop (Nantong, China), ISO 9001/14001/45001 certification (ANAB / IAF / UKAS) as well as our global network. Whenever highly efficient and cost-optimized marine solutions play a role, choose SME expertise!