Operating Principle Of High And Low Temperature Of Dry Cooler

1, Core Basic Principles (General)
The essence of a dry cooler is an air liquid wall heat exchanger, with no evaporation or water spray throughout the entire process (pure dry cooling), relying solely on forced convection heat transfer:
Refrigerant circulation: High temperature refrigerant (absorbing equipment/process heat) enters the finned coil of the dry cooler.
Forced convection of air: The fan drives the outdoor air to sweep horizontally/vertically through the finned tubes, and the air temperature is lower than that of the refrigerant.
Sensible heat transfer: Heat flows from the refrigerant → tube wall → fins → air, and is discharged after the refrigerant cools and the air heats up.
Closed loop cycle: The cooled refrigerant returns to the system to absorb heat and continues to circulate.
Key constraint: Cooling limit ≈ outdoor dry bulb temperature+approximate temperature (usually 3-8 ℃), cannot be lower than the ambient dry bulb temperature.

2, Operating principle under low temperature conditions (winter/spring/autumn, energy-saving mode)
1. Applicable scenarios
The outdoor dry bulb temperature is significantly lower than the system return water temperature (such as ≤ 15 ℃), which can completely/partially replace the compressor and achieve free cooling.

2. Operation logic (taking ethylene glycol/water system as an example)
Mode 1: Fully natural cooling (temperature difference ≥ 14 ℃)
Turn off the compressor refrigeration system.
The refrigerant pump is running at full load, and the high-temperature return water enters the dry cooler.
Fan frequency conversion speed regulation (on-demand air volume), air takes away heat, and the refrigerant is cooled to near outdoor temperature.
Low temperature refrigerant is directly sent to the machine room/process end, meeting all cooling capacity requirements with extremely low energy consumption.
Mode 2: Partial natural cooling (temperature difference 7-14 ℃)
The dry cooler first assumes the basic cooling capacity.
Insufficient cooling capacity is assisted by a compressor for cooling, and mixed before being supplied for cooling.
The linkage regulation between the fan and compressor balances energy conservation and stability.
3. Low temperature protection
The refrigerant used is ethylene glycol aqueous solution (antifreeze, non freezing at -20 ℃).
Fan start stop/speed control to avoid frosting/cracking of the coil; If necessary, bypass the hot fluid to increase the inlet temperature.

3, Operating principle under high temperature conditions (summer/high load, normal mode)
1. Applicable scenarios
The outdoor dry bulb temperature is close to/higher than the system demand temperature (such as ≥ 25 ℃), and the natural cooling capacity is insufficient, requiring the joint operation of compressor and dry cooler.
2. Running Logic
Full load of dry cooler: The fan runs at full speed, maximizing the use of air heat dissipation and reducing the condensing temperature of the compressor.
Compressor refrigeration main force:
The refrigerant absorbs system heat (refrigeration) in the evaporator.
The high-temperature and high-pressure refrigerant enters the dry cooler (condenser), is cooled by air, and condenses into liquid.
After throttling, the circulation is carried out, and the dry cooler is responsible for condensation and heat dissipation, improving the efficiency of the compressor.
Extreme strengthening (optional)
Activate adiabatic pre cooling (wet film/spray) during high temperature and high humidity: spray water mist onto the inlet air to evaporate and cool down, making the dry cooler approach the wet bulb temperature, increasing heat transfer by about 50-60%, but consuming very little water.

4.applied value
Low temperature season: Replace compressors, save 60-90% energy, and extend compressor life.
High temperature season: As an efficient condenser, it reduces compressor energy consumption and saves 100% water (pure dry cooling).
Throughout the year: closed-loop operation, stable water quality, no corrosion, and simple maintenance.