Water Cooling Pumps Overview
Cooling is the process whereby water, seawater, glycol or brine is pumped through pipework to cool a piece of machinery such as engines, turbines, Winches, or to provide cooling through a chiller.
There are five methods of cooling which can be used in a process. These are open-loop, closed-loop, open tower, closed tower systems and adiabatic.
Open-loop systems
In open-loop cooling systems, water is pumped from an open bodied water source which can be a river, lake or sea to cool machinery. Once the water has passed through a circuit to cool the required machinery the water is pumped back into the open body. Freshwater is continually entering the system. This system is typically used when equipment is located next to an open body of water such as a ship using seawater for engine cooling. Cooling pumps on board marine vessels typically operate 24/7.
Closed loop systems
Water is recirculated within a system as part of a cooling ccircuit. Cold water or coolant enters the cooling circuit, where it heats up. To cool the fluid temperature it is passed through a heat exchanger which may also be cooled by a fan to lower temperatures further. An example of this type of system on board a vessel would be in lube oil cooling, jacket water system, fuel injection systems, and starting air systems. 
Open tower
Water is pumped through the system and then ejected via nozzles which fall through a tower causing cooling before being collected. This system is inefficient as a lot of water is lost to evaporation and as it falls through the tower the air friction causes heat. Often used in power stations and is the lowest cost compared to the closed tower system initial.
Closed tower
Water is pumped through the system as above by heat exchange separates the water and the water is kept within a coil rather than subject to fowling by mixing with air. Also, NPSH requirements are kept low.
Adiabatic
Closed-loop system whereby air is drawn over evaporating water droplets cooling incoming air. Saves water use from 1.5m gallons of water in cooling towers to 40k litres per year.
