The data center is an important infrastructure for the information industry. Nowadays the energy consumption of data center is getting higher along with the high density, high power servers in use.
About 40% of data center energy consumption is from the cooling system. While meeting the cooling requirements of the equipment room, to reduce the energy consumption of the cooling system, natural cooling technology is currently widely recognized as a technology with a better energy-saving effect in improving energy efficiency.

Natural cooling is the use of natural cold air or cold water to cool the data room. This technology does not require mechanical refrigeration to be turned on. It is a model that uses a plate heat exchanger, a cooling tower, etc., to provide a cooling source for the data room.

Natural cooling is mainly divided into two categories: wind side natural cooling and water side natural cooling.

Wind side natural cooling

Direct type: direct outdoor cold air into the room, direct evaporative cooling

Indirect type: indirect outdoor cold air into the room, through heat exchanger (dry/wet), heat pipe, and recycle refrigerant

Water side natural cooling

Direct type: Direct use of outdoor low temperature water (sea water, lake water, river water) for cooling

Indirect type: Cooling tower cooling water direct cooling, cooling tower + plate heat exchanger, closed cooling tower, dry cooler

Natural cooling technology refers to by using of natural cold sources to stop or in low capacity the operation of chillers or other mechanical refrigeration systems, thereby reduce energy consumption.
Water-water plate heat exchangers and some pipelines and equipment are added to the conventional air-conditioning water system. The chilled water uses a circulation system consisting of a cooling tower + a cooling water pump + a plate heat exchanger to exchange heat and reduce the temperature of the machine room. The plate heat exchanger is connected in parallel with the chiller, and the two are equipped with independent cooling water pumps and chilled water pumps. After the cooling water and the chilled water are exchanged in the plate heat exchanger, if the chilled water supply temperature can meet the requirements, the chiller is turned off, switch on the plate heat exchanger as a replacement, and natural cooling is achieved. If the temperature of the cooling water cannot lower the temperature of the chilled water back to the required water supply temperature, the plate heat exchanger is switched off and the chiller is turned on direct cooling supply mode.

Cooling tower type natural cooling refers to the technology of using a lower outdoor air temperature to obtain low-temperature cold water through a cooling tower. It’s a technology replacing mechanical cooling to achieve data center cooling and one of the most used natural cooling technologies in the data center.

Cooling tower natural cooling includes:

1. open cooling tower direct natural cooling. The cold water obtained by the cooling tower is directly used in the precision air conditioner of the machine room.
2. open cooling tower indirect natural cooling. The cold water prepared by the cooling tower exchanges heats with the high-temperature backwater of the precision air conditioner in the machine room through the plate heat exchanger to realize the cooling to the machine room.
3. closed cooling tower natural cooling. Low-temperature water is prepared by a closed cooling tower or low-temperature ethylene glycol solution to directly cooling use for precision air conditioning in the machine room.
4. dry cooler natural cooling. The dry cooler is a tubular heat exchanger placed in the tower, and the circulating water or ethylene glycol solution from the precision air conditioner of the machine room is cooled by the low-temperature cold air circulating through the outside.

The open cooling tower indirect natural cooling method is a widely applied form of natural cold source utilization in the data center, which realizes high cooling efficiency with indirect heat exchange through the water-water plate heat exchanger. However in cold regions, the antifreeze problem of open cooling towers is critical and should be taken seriously.

The computer machine room runs all year round under constant temperature and humidity conditions. The equipment room maintains a temperature of 18-24 degrees throughout the year. The plate heat exchangers cool the cooling water of the equipment room with water or  water containing ethylene glycol.
Considering the plate heat exchanger efficiency, the temperature difference between the two sides of the heat exchanger is 1-1.5 °C. For example, the one side supply/ return water temperature is 13.513.5/18.5°C, the other side water is 21/15°C. The pressure drop is≤50kPa.