Problems in the planning, design and operation and maintenance of air conditioning and refrigeration systems

Problems in the planning, design and operation and maintenance of air conditioning and refrigeration systems

Usually, people look at the air conditioning and refrigeration system of a data center as simple, thinking that it is enough to create a temperature environment that meets the requirements and standards as long as the IT equipment runs. In fact, it is not. The design, planning and operation and maintenance effects of the data center air conditioning and refrigeration system will directly affect the construction scale and sustainable development of the data center. So what are the problems in the planning, design, operation and maintenance of the air conditioning system?

　　 1. Air short circuit circulation is the primary factor for low efficiency of refrigeration system

　　The short-circuit circulation of airflow causes a lower air conditioner backflow, which may cause the remaining air conditioner components to work at a lower performance, thereby failing to meet the cooling performance requirements.

　　The remaining system cannot provide the higher air supply rate required to overcome the circulation effect, resulting in increased circulation and excessive equipment temperature.

　　 2. The cooling scheme does not support continuous operation of high power density racks

　　In the traditional computer room refrigeration system, the inlet air temperature of high-density racks increases rapidly with time after the mains power failure. The shortest time for the refrigeration system to stop running after the mains power failure is: the generator start conversion time 15S + the air conditioning refrigeration equipment delay start time 3~3.25 minutes. Therefore, traditional air conditioning and refrigeration solutions cannot meet the requirements.

　　 Therefore, it can only reduce the number of racks in the computer room, and the country reduces the power density of the racks. The final result is a low-density data center. This results in waste of investment costs and low efficiency. The PUE value remains high throughout the entire life cycle.

　　 Three, the temperature and humidity settings of the air conditioner

　　 If there is no short-circuit circulation of the airflow in the rack, the temperature of the output air of the air conditioner will be the same as the inlet air required by the IT equipment at 18~21℃. but. In practice, the outlet air temperature of the air conditioner is usually lower than the IT inlet temperature. If you can solve some of the problems mentioned above, you can increase the CRAC outlet temperature set point.

　　 Air conditioning and temperature setting points are determined by the air distribution system, while humidity can be adjusted to any optimal value. If the humidity value is higher than the requirement, the pit can cause moisture condensation in the air conditioner and reduce the air humidity. The humidification requirements will also significantly reduce the air lift and the air cooling performance of the equipment. To make matters worse, humidification requires water. In a typical data center, this situation would waste thousands of gallons of water each year.

　　 Fourth, rack distribution and equipment distribution issues

　　 The reasonable layout of the rack space is also very important to ensure that the rack has the proper temperature and flow of air. The purpose of improving the rack layout is also to control the air circulation, that is, to prevent the air from the air conditioner from mixing with the hot exhaust gas before it reaches the air inlet of the equipment. The specific design principles are basically the same, as far as possible to isolate the hot exhaust gas from the cold gas at the air inlet of the equipment.

　　 5. The influence of altitude on cooling effect

　　 In order to reduce energy consumption, we hope to build data centers in cold regions. However, in areas with high altitudes, data centers cannot actually save energy due to the low atmospheric pressure

. 　　 Six, air conditioning equipment installation problems

Another decisive factor for the cooling efficiency of air conditioners is the amount of heat dissipation of the outdoor unit of the air conditioner, including the installation location, layout and installation platform size, but architectural planning often ignores it; the layout of the indoor and outdoor units of the air conditioner does not meet the expansion of the data center , Renewal requirements.

　　In the heat load statistics of the data center, when calculating the nominal cooling capacity of the water chiller, the fan power of the air-conditioning city unit is not calculated.

　　 Seven, improper selection of air conditioning equipment performance parameters will also affect the operating effect

In the bidding document for air-conditioning equipment, the designer did not specify the technical indicators of the outdoor body of the air-conditioner: or the user conducted a unified bidding for air-conditioners with uniform technical specifications for data centers across the country: and most air-conditioning suppliers quoted according to the standard configuration, and finally won the bid at a low price , Resulting in low efficiency of the air conditioner.

　　 The above seven reasons are the main reasons for the low cooling effect of air conditioning. Only by solving these problems can the data center give full play to its effectiveness and role.