What is a circulating water cooling system?

With the development of urban construction, the circulating water cooling system has become an indispensable part. The system corresponds to refrigeration equipment and includes a cooling tower located on the roof of the podium, circulating water pumps on the second basement level, manual and electric butterfly valves, filters, electronic descalers, and more. The main refrigeration unit is located on the first basement level, sharing common supply and return water mains for cooling water. The system has drain and discharge valves set at low points. Considering that sometimes the municipal water pressure on the podium roof is insufficient, a water supply pump system has been added, controlled by the water level in the cooling tower's collection basin to start and stop the pump. Expansion joints are added at pipeline deformation joints. Rigid waterproof sleeves are installed at wall panels in the crossover room. Pressure gauges are installed on the pipelines before and after the pumps and chillers. To protect the refrigeration unit, a water flow indicator interlocked with the main unit is installed on its inlet pipe.

System Principle

In the system, the cooling tower, refrigeration unit, cooling pump, and refrigeration pump should be started correspondingly one by one. Electric valves should be used to control water flow, preventing water from flowing through pipelines of stopped units, which would affect processing efficiency. The startup sequence is: electric valve, cooling tower, cooling water pump, refrigeration unit, refrigeration water pump; the shutdown sequence is the reverse, with the refrigeration unit shutting down half an hour earlier. Cooling water pumps above 30kW should use soft starters, multiple pumps in parallel, controlled by variable frequency drives, adjusting pump power according to external environmental conditions for better energy savings. Cooling tower fans use dual-speed motors and appropriately adjust fan blade angles, which significantly improves energy saving and noise reduction.

Different forms of circulating water cooling systems arise depending on whether a water tank is set and its location. Calculating the head of the circulating water pump is very important, only needing to consider friction loss, outlet head, and the water level difference at the cooling tower inlet and outlet, generally about 25m, which is not greatly related to the height of the cooling tower. The head H of the cooling water pump is calculated by the formula: H = k(hf + hd + hm + hs + ho)

k is the safety factor, taken as 1.1 to 1.2; hs and hd are the frictional resistance and local resistance of the cooling water pipeline; hf is the resistance of the condenser inside the refrigeration unit; hm is the water level difference at the cooling tower inlet and outlet; ho is the outlet head at the nozzle.

Cold

Make-up Water Quantity of the Cooling Tower
Qc is the heat discharged by the cooling tower; for compression refrigeration machines, it is 1.3 times the load; for absorption refrigeration machines, it is twice the load; C is the specific heat of water;

t is the temperature difference between the cooling tower inlet and outlet water. The make-up water quantity Q of the cooling tower is calculated by the formula: Q = N * k * Δt / (N - 1)

Where N is the concentration ratio; for chemical dosing methods, it should not exceed 5; for electronic descalers, it should not exceed 10; K = 0.001 + 0.00002T, where T is the air temperature.

The cooling tower serves the refrigeration unit and should be placed as close as possible to the service object to shorten the cooling water pipeline. The cooling tower should be set in a well-ventilated area downwind of the building's prevailing wind direction, facilitating operation, management, and installation, while minimizing environmental impact.

Noise of the Cooling Tower

The noise of the cooling tower mainly comes from the motor, fan, water spray, and tower vibration. Rubber flexible joints connecting the tower pipelines and foundation vibration isolation should be considered.

Use of the Cooling Tower

The use of fanless cooling towers, besides requiring a slightly larger footprint and higher outlet water head, has many advantages: energy saving, water saving, noise reduction, reduced maintenance and failure rates, and no vibration, thus eliminating flexible joints in pipelines. Represented by Guangzhou Liangji Cooling Equipment Company, the fanless cooling tower creatively replaces the fan with a high-efficiency fluid kinetic energy conversion device as the aerodynamic device. Using the pressure from the circulating cooling water pump, special nozzles spray the circulating cooling water to form a water curtain. The high-speed water curtain drives adjacent air to move together, converting kinetic energy between water and air during movement. The mixed unsaturated air enters the diffuser for further pressurization. At the top of the tower, a high-efficiency water separator separates steam and water, discharging hot air outside the tower. The cooled water falls to the packing layer for secondary heat exchange with the incoming air, achieving excellent cooling of the circulating cooling water.