Determining the cooling water demand of the cooling tower requires comprehensive consideration of multiple factors. The following is a detailed introduction:

1. Calculate based on the heat dissipation of the equipment

For heat exchange equipment in industrial production:

For example, reactors and condensers in chemical production, these equipment will release a large amount of heat to the surrounding environment during operation. First, the heat exchange power of the equipment must be obtained. Usually, the rated heat load (usually in kilowatts, kW) will be indicated in the manual or technical data of the equipment. This heat load is the heat dissipated by the equipment per hour. According to the principle of heat conservation, the heat that the cooling tower needs to take away is basically equivalent to the heat dissipated by the equipment (considering a certain heat loss coefficient, generally about 1.1 - 1.3). Then use the relationship between heat and water specific heat capacity to calculate the cooling water volume. The specific heat capacity of water is about 4.2kJ/(kg・℃). Assuming that the heat dissipation of the equipment is Q (kJ/h), and the temperature difference between the inlet and outlet water is Δt (℃), the calculation formula for the cooling water volume m (kg/h) is roughly: m = Q / (4.2×Δt). Then convert the mass flow rate to the volume flow rate (the mass of 1m³ water is about 1000kg), and you can get the cooling water volume required per hour (m³/h).

For building air conditioning systems:

Chiller: The chiller is the core equipment for generating cold in the air conditioning system. At the same time, it also generates heat during operation that needs to be dissipated through the cooling tower. Generally, the manufacturer of the chiller will provide the cooling capacity (also in kW) and the corresponding condenser heat load parameters. According to the same law of heat conservation, after considering a certain margin (such as 1.1-1.2 times), the cooling water demand is determined according to the above water specific heat capacity calculation formula. For example, for a chiller with a cooling capacity of 1000kW, its condenser heat load is 1200kW (assuming the margin coefficient is 1.2), and the inlet and outlet water temperature difference is set to 5℃, then the cooling water volume is calculated as: m = 1200×1000 / (4.2×5) ≈ 57143kg/h, which is converted into a volume flow of about 57.143m³/h.

Estimation of the cooling load of the entire building: If there are no detailed chiller parameters, the cooling water demand can also be estimated from the perspective of the overall cooling load of the building. First, calculate the cooling capacity required by the building through professional building load calculation methods (such as hourly cooling load coefficient method, etc.). Usually, the cooling load corresponding to each square meter of building area is 100-200W (different functional buildings have differences, such as office buildings are generally estimated at 100-150W/m², and shopping malls may be estimated at 150-200W/m²). Then, according to the energy efficiency ratio and other parameters of the air-conditioning system, the condenser heat load is reversed to determine the cooling water volume. However, this method is relatively rough and the error may be around 10%-20%.

2. Consider the system operating conditions

Ambient temperature influence: The higher the ambient temperature, the smaller the temperature difference between the cooling tower and the outside air, the smaller the driving force of heat exchange, and the worse the cooling effect. Therefore, in hot areas or during high temperatures in summer, in order to ensure the same cooling effect, it is often necessary to appropriately increase the cooling water volume to compensate for the adverse effects caused by the reduced temperature difference. For example, in areas with an average summer temperature of 30℃ in the north and 35℃ in the south, for equipment with the same heat load, the amount of cooling water used in the cooling tower in the south may be about 10% - 20% more than that in the north.

Impact of air humidity: When the air humidity is high, it is more difficult to evaporate water, and the cooling tower often relies on the absorption of heat by evaporation of water to achieve cooling. Therefore, in a high humidity environment, the cooling efficiency will be reduced, and the amount of cooling water needs to be increased accordingly. For example, in coastal humid areas and inland dry areas, under the same conditions, the cooling water demand for cooling towers in coastal areas may be higher. The specific increase depends on factors such as actual humidity differences, which may be around 5% - 15%.

System operation time and stability requirements: If the equipment needs to run continuously for a long time, or the stability requirements for the cooling effect are extremely high (such as some high-precision industrial production processes, the temperature fluctuation cannot exceed ±1℃), then in order to cope with various adverse conditions that may occur and ensure that the cooling system is always in good condition, the amount of cooling water will generally be appropriately increased based on the calculation, usually 10% - 15% as a margin.

3. Combined with factors such as future expansion

Expected expansion of enterprise production scale: For industrial enterprises, if there are plans to increase production lines and expand production scale in the next few years, the heat load of the corresponding heat exchange equipment will increase. When initially selecting a cooling tower, sufficient cooling water volume should be reserved. Generally, the selection of cooling towers can be determined according to the expected maximum heat load in the next 5-10 years, and 20%-50% (determined according to the specific expansion plan and industry characteristics) of cooling water volume margin should be reserved to avoid the need to replace cooling towers due to insufficient cooling capacity in the future, which will increase costs and affect production.

Changes in building functions or upgrades to air-conditioning systems: In terms of buildings, if there is a possibility of changing the use function in the future (such as converting office buildings into hotels) or upgrading the air-conditioning system (such as replacing higher-power chillers), the impact of these factors on the demand for cooling water should also be considered in advance, and appropriate margins should be reserved to ensure that the cooling tower can continue to meet demand.

In summary, determining the cooling water demand of the cooling tower requires accurate understanding of the equipment's heat load, full consideration of operating conditions and prediction of future changes, and comprehensive determination of the appropriate cooling water volume through rigorous calculations combined with practical experience.