How is fan power calculated? Points will be added to those who answer correctly

Fan power calculation formula: Power (kW) = Flow rate (m3/s) * Pressure (Pa) / Efficiency / 10

In addition to air volume, factors that determine the capacity of a fan motor include air pressure and fan efficiency. The formula for calculating the power required by the fan, P (KW), is P=1.1×Qp/3600×1020η. In the formula, 1020 is the conversion coefficient ； Q—Air volume, m3/h ； P—Total wind pressure of the fan, Pa ； η—efficiency of the fan, %

The formula for calculating the power required by the fan, P (KW), is P = Q * p / (3600 * 1000 * η0 * η1), where Q represents the air volume in m3/h； p—total wind pressure of the fan, Pa ； η0—is the internal efficiency of the fan; it generally ranges from 0.75 to 0.85, with lower values for smaller fans and higher values for larger fans. η1—is the mechanical efficiency; it is set to 1 when the fan is directly connected to the motor ； 2. The coupling connection value is set at 0.95~0.98 ； 3. Use a V-belt for connection; the value should be 0.9~0.95 ； 4. For transmission using a flat belt, a value of 0.85 is used. Based on the parameters mentioned above, the power required by the fan is approximately 30 KW. Here, η0 is taken as 0.75 and η1 as 0.95. Of course, a safety factor also needs to be considered for the motor’s power; this is usually set at 1.15. If the motor efficiency is taken into account at 0.9, then the power becomes 30*1.15/0.9 = 38 KW. Therefore, a motor with a capacity of 37 KW will suffice. Doesn’t the poster have the fan’s manual? Everything is described in detail there.

In the case of direct motor connection, for forward-blade fans, the power can be calculated as follows: Power = 1.25 * (25715 * 30000) / (1000 * 0.7 * 3600) = 383 Kw. However, an exact calculation is required depending on the specific conditions, as the connection method and blade design are unknown; the calculation method remains roughly the same in such cases

I. Operating parameters of fans The main parameters that indicate the performance of a fan are wind pressure H, air volume Q, shaft power N, efficiency h, and rotational speed n, among others. (1) Fan (actual) flow rate Q: The actual flow rate of a fan generally refers to the volume of air that passes through the fan’s inlet within a given time period; it is also known as volumetric flow rate (and, unless otherwise specified, this refers to conditions at standard temperature and pressure). The unit for this value is m³/s. (II) Actual total pressure Hf and static pressure Hs of the fan: The total pressure Ht of a fan represents the energy expended by the fan in doing work on the air, per unit volume of air (N·m/m3 or Pa). This value is equal to the difference between the total pressure of the airflow at the fan’s outlet and that at the inlet. When natural wind pressure is ignored, Ht is used to overcome the resistance in the ventilation ductwork, denoted as hR, as well as the kinetic energy loss at the fan outlet, denoted as hv; thus, Ht = hR + hV. The wind pressure required to overcome the resistance in the ductwork is called the static pressure of the fan, HS, in Pa. Since HS = hR = RQ2, it follows that Ht = HS + hV. (III) Power of the fan: The output power of a fan (also known as air power) is referred to as total pressure power, Nt, when calculated based on the total pressure. It is calculated using the following formula: Nt = HtQ × 10^-3. When the output power is calculated based on the fan’s static pressure, it is called static pressure power, NS; that is, NS = HSQ × 10^-3. Therefore, the shaft power of the fan, which represents the input power of the fan, is denoted as N (in kW). In these formulas, ht and HS represent the fan’s total pressure efficiency and static pressure efficiency, respectively. When the efficiency of the motor is hm and the transmission efficiency is htr, with the input power to the motor being Nm, then the dimensionless coefficients, , and η for fans of the same type at similar operating conditions are equal. Their pressure H, flow rate Q, and power N are in a proportional relationship with their rotational speed n, size D, and air density ρ; this proportional relationship is known as the law of proportionality.

The calculation results you mentioned are all incorrect

This problem lacks static pressure, so it is impossible to calculate the total pressure power and the static pressure power; in fact, no calculation can be done at all. Therefore, the original poster is correct – all the calculations above are incorrect, as it is easy to see that results cannot be obtained without one of the necessary conditions. Additionally, the pressure difference between inlet and outlet represents the energy consumption of the fan itself, while the static pressure is the force required by the fan to overcome the pipeline resistance; without this value, it is impossible to calculate the fan’s shaft power.

Is the static pressure the inlet pressure? How do you calculate it once you know the static pressure?

How can one calculate anything without density, knowing only the volumetric flow rate?