Calculation Method of the Refrigeration Capacity of Precision Air Conditioners

2025-04-16

The load of precision air conditioners generally needs to be accurately calculated according to the actual residual heat, residual temperature and state changes of the process room. However, it can also be calculated when conditions do not allow. The following is an introduction.

Calculation Method of the Refrigeration Capacity of Precision Air Conditioners1744810862429

Simple Calculation Methods for Refrigeration Capacity:
Method 1: Power and Area Method
Qt = Q1 + Q2
Qt is the total refrigeration capacity (kw)
Q1 is the indoor equipment load (= equipment power X 0.8)
Q2 is the environmental heat load (= 0.18KW/m2 X the area of the computer room)
Method 2: Area Method (when only the area is known)
Qt = S x p
Qt is the total refrigeration capacity (kw)
S is the area of the computer room (m2)
P is the estimated index of cooling capacity. Estimated indexes of cold load for precision air conditioner places:
Telecom switches, mobile base stations (350 - 450W/m2)
Financial computer rooms (500 - 600W/m2)
Data centers (600 - 800W/m2)
Computer rooms, billing centers, control centers, training centers (350 - 450W/m2)
Workshops for electronic products and instruments, precision machining workshops (300 - 350W/m2)
Standard testing rooms, calibration centers (250 - 300W/m2)
Ups and battery rooms, power machine rooms (300 - 500W/m2)
Hospitals and testing rooms, living culture rooms, clean rooms, laboratories (200 - 250W/m2)
Warehouses (museums, libraries, archives, tobacco, food) (150 - 200W/m2)

Calculation of Air Conditioner Options for UPS Rooms
1-1. BTU/hour = KCal×3.96
1-2. KCal = KVA×860
1-3. BUT/hour = KVA (UPS capacity)×860×3.96×(1 - UPS efficiency)
= KVA (UPS capacity)×3400(1 - UPS efficiency)
Example: For a 10KVA UPS with an overall efficiency of 85%, its heat dissipation is calculated as follows:
10KVA×3400×(1 - 0.85) = 5100 BTU/hour
1 British thermal unit per hour (Btu/h) = 0.293071 watt (W)

Calculation Formula for Air Conditioner Options in IDC Rooms
Q = W×0.8×(0.7---0.95)+｛(80---200)×S｝/1000. Q is the refrigeration capacity, in units of KW;
W is the power consumption of the equipment, in units of KW; tentatively set as 110KW according to user requirements;
0.8 is the power factor;
0.7 - 0.95 is the heat generation coefficient, that is, how much electrical energy is converted into heat energy; take 0.7
80 - 200 is the environmental heat generation per square meter, in units of W;
S is the area of the computer room, in units of m2.

Determine the Refrigeration Capacity According to Different Situations
Situation 1 (Without Investigating the Computer Room Equipment, etc.)
Estimation of the Data Room: In a small financial computer room, the area of the data equipment room is usually less than 50 square meters. Before the heat of the data equipment and the building of the computer room is determined, the refrigeration capacity of the computer room air conditioner can be estimated according to the general estimation method for financial computer rooms: 500w～600w/m2, and some high-capacity computer rooms reach 800w/m2.
For example, if the area of the data room is 50 m2, the required refrigeration capacity is approximately: 25kw. Select 3 DataMate air conditioners with a single-unit refrigeration capacity of 8.6kw, plus one redundant unit, a total of 4 units.

Calculation Method of the Refrigeration Capacity of Precision Air Conditioners1744810862240

When the equipment and maintenance structure of the data computer room are determined, calculate the heat generation of the equipment and the heat of the maintenance area, and adjust the configuration of the air conditioner.
Estimation of the Power Room: The main heat generation in the power room comes from equipment such as UPS and power supplies, and its heat capacity is relatively low. Two air conditioners with a single-unit refrigeration capacity of 8.6kw can be selected and arranged redundantly. In a medium-sized financial computer room, the area of the data equipment room is usually less than 200 square meters. Before the heat of the data equipment and the building of the computer room is determined, the refrigeration capacity of the computer room air conditioner can be estimated according to the general estimation method for financial computer rooms: 500w～600w/m2, and some high-capacity computer rooms reach 800w/m2.
For example, if the area of the data room is 200m2, the required refrigeration capacity is approximately: 100kw. Select 2 PEX2060 air conditioners with a single-unit refrigeration capacity of 58.

Calculation Method of the Refrigeration Capacity of Precision Air Conditioners1744810862365

4kw, and the total refrigeration capacity is 116.8kw, which meets the requirements. To ensure the reliability of the equipment, add one redundant unit, a total of 3 units. When the equipment and maintenance structure of the computer room are determined, calculate the heat generation of the equipment and the heat of the maintenance area, and adjust the configuration of the air conditioner.
Estimation of the Power Room: The main heat generation in the power room comes from equipment such as UPS and power supplies, and its heat capacity is relatively low. 2 PEX1020 air conditioners with a single-unit refrigeration capacity of 19.1kw can be selected and arranged in a 1 + 1 redundant manner.
Situation 2 (After Investigating the Computer Room Equipment, etc.)
After arriving at the user's computer room site, understand the area of the computer room, the number of servers in the computer room, and various network products such as routers and switches. The cabinets in the computer room are concentrated, the equipment density is high, the heat generation is relatively concentrated and large. Central air conditioners and civil air conditioners, due to the limitations of air supply volume and wind speed, make the temperature of the entire computer room not uniform enough, and the control accuracy of temperature and humidity is not high. Precision air conditioner products can supplement the cooling capacity, accelerate the air circulation, and meet the requirements of better controlling the temperature, humidity and cleanliness of the computer room, providing a better operating environment for the computer room equipment.
According to the requirements of load calculation in air conditioner design, the method for determining the load of precision air conditioners is as follows:

Sources of Main Heat in the Computer Room
① Equipment load (heat load of computers and cabinets);
② Lighting load of the computer room;
③ Load of the building maintenance structure;
④ Supplementary fresh air load;
⑤ Heat dissipation load of personnel, etc.
⑥ Others
Heat Load Analysis:
(1) Heat Load of Computer Equipment: Q1 = 860xPxη1η2η3 Kcal/h
Q1: Heat load of computer equipment
P: Total power consumption of various equipment in the computer room
η1: Simultaneous use coefficient
η2: Utilization coefficient, η3: Load working uniformity coefficient
Generally, η1η2η3 is taken between 0.6 - 0.8. In this design, considering that the requirement for capacity change is small, the value is taken as 0.6.
(2) Heat Load of Lighting Equipment: Q2 = CxPKcal/h
P: Calibrated output power of lighting equipment
C: Heat release per 1W output Kcal/hw (0.86 for incandescent lamps, 1 for fluorescent lamps)
According to the requirements of the national standard "Technical Requirements for Computer Station Sites", the illuminance of the computer room should be greater than 2001x, and its power consumption is approximately 20W/M2. In subsequent calculations, the lighting power consumption will be calculated based on 20 W/M2.
(3) Human Body Heat Load Q3 = PxNKcal/h
N: Number of regular personnel in the computer room
P: Heat generation of the human body, the sum of sensible heat and latent heat of the heat load of light physical workers, which is 102Kcal when the room temperature is 21℃ and 24℃.
(4) Conductive Heat of the Enclosure Structure Q4 = KxFx(t1 - t2) Kcal/h
K: Thermal conductivity system of the enclosure structure, 1.4 - 1.5 for ordinary concrete
F: Area of the enclosure structure
t1: Temperature inside the computer room ℃
t2: Calculated temperature outside the computer room ℃
In subsequent calculations, t1 - t2 is set as 10℃ for calculation. The roof and floor are calculated according to the correction coefficient of 0.4.
(5) The calculation of the fresh air heat load is relatively complicated. In this solution, we balance it with the equipment margin of the air conditioner itself and do not calculate it separately.
(6) Other Heat Loads In addition to the above heat loads, equipment such as oscilloscopes, soldering irons, and vacuum cleaners used in work will also become heat loads. Since the power consumption of these equipment is small, it is only roughly calculated according to the product of their input power and the thermal work equivalent. Q5 = 860xP
Total Heat Load of the Computer Room Q = Q1 + Q2 + Q3 + Q4 + Q5
Calculation of Air Volume in the Computer Room According to the standard, when selecting the air volume of the computer room air conditioner, the air volume divided by the volume of the room is equal to the number of air supply cycles per hour. Generally, it is best to select the number of cycles as 30 - 40 times. This is the particularity of the large air volume and small enthalpy difference required for the computer room.
However, when selecting the number of cycles, pay attention to the fact that there are wire slots under the floor and other obstacles that will affect the air supply speed. Therefore, the actual number of cycles is smaller than the calculated value. A large number of cycles is not likely to cause local overheating and is beneficial to heat dissipation. In recent years, for the purpose of energy conservation, the requirements for computer rooms are higher. There are also cases where air ducts are used for air supply under the floor. Or if air ducts are not used, a closed component can be added, which can also achieve the effect of energy conservation!