In the same application, if you selected a ⦠re FAN EFFICIENCY FORMULA DERIVATION. 5. Fig 2shows the pressures through a fan, each of which is described below: Inlet Pressure; is the static pressure on the inlet side of the fan. H2O): New Horsepower (HP): FAN APPLICATION FORMULAS Fan Brake Horsepower: Flowrate (CFM): Static Pressure at Discharge (in. 6.1 . Fans use approximately 40% of all electricity in HVAC systems. 1 cfm = 1.7m³/h. As explained by Ted ,I am only showing you an example for calculation in both the units and I hope you doubt will be clear. Static Efficiency - Fan efficiency based on static pressure and fan brake horsepower at the same density. Note that the flow and pressure constants in the FEP formula (250 cfm and 0.4-in. Fan BHP = (cfm x static press "w.c.) / (6356 x fan efficiency) Fam Motor HP = fan bhp / motor efficiency Following are values from a propeller fan manufacturer's catalog for a particular fan: Static press. Notice that the 72-inch fan has the highest static efficiency which is the proper metric for nonducted applications. FLOW RATE 1 m3/s 1 m3/hr x 2118.9 x 0.58858 2118.9 CFM 0.5884 CFM VELOCITY 1 m/s x 32.8083 x 196.85 32.8083 ft / s 196.85 FPM PRESSURE 1 N/m2 x 0.00402264 x 0.00029530 ⦠I TRIED A LOT BUT HOW 102 IS COMING IN DENOMINATOR ? Static efficiency is a ratio of the fan power output to the power supplied to the fan. This is the useful work required from the fan. Static efficiency is calculated using only static pressure. so 102 value comes in numerator instead of denomenator. A conversion constant is a number used to normalize equations containing varied units of measurement, in this case, CFM and in. At this point the ratio of the output power of the fan (Volume flow (m 3 /s) x Static Pressure development (Pa) and the electrical power input (W) is at its greatest and the sound pressure being produced by the fan will be at its quietest. But, if the pressure is measured in mmWC instead of Pascals and Power is expressed in kW, the formula can be derived as follows;- 1 mmWC = 9.81Pa. When calculating this, you will be able to determine the power that a fan requires theoretically, but you must be aware that the actual power that the fan requires (called brake horsepower) will always be greater than what you calculated simply because no fan can achieve perfect efficiency. CalQlata has tried to keep the operation of this calculation option as simple as possible, given that it is recommended for general purpose calculations only and not for actual purchase specifications (see Fan Calculator â Technical Helpbelow). Fan total pressure is the total pressure (static pressure plus velocity pressure) at the fan outlet minus the total pressure at the fan inlet. wg Pt = Total pressure, in. efficiency of the fan or the static efficiency of the fan. The peak total efficiency occurs at the top of the âbellâ shaped efficiency curve. efficiency = m3/s X 0.102 mmwc *100/( motor kw x motoe eff.) An axial fan is a type of fan that causes gas to flow through it in an axial direction, parallel to the shaft about which the blades rotate. Let us assume a fan having a flow of volume 16m3/sec and devlops a total pressure of 500 mmH2O. where . Using the formula given in books using mmH2O as pressure, Kw = (m3/sec x Pressure mmH2O) /102 = 16 x 500 /102 = 78.4 Kw, 2. Fan total efficiency is calculated using total pressure. Hello Sidhant, Your example;- 1mmwc = 9.8 Pa. so put 1Pa = 0.102 mmwc. (Velocity pressure excluded). The higher the volume relative to static pressure, the more likely it is that you can select a high-efficiency fan. W.G). Static efficiency uses static pressure, which does not include the kinetic energy, to calculate the effi- ciency. Static efficiency is the product of the volume and pressure you need in your application divided by the product of the conversion constant and horsepower, as follows: You can use the maximum static efficiency to determine the horsepower you need in your application. In both the cases the power is same , I dont think there is any confusions now. Know the answer to this question? ie. But what constitutes good efficiency? Technical; Useful Formulas; Useful Formulas. Diagram of a pitot-static tube in a duct with air flow..... 18 Figure 9. 6.8 13.4 6.87 . The factor of 102 is used to convert mmWC into pascals because the formula for the static fan efficiency in SI units is;-Static Fan Efficiency = Volume (m3/s) * Pressure gain (Pa) / Power input (W) * 100. Some advanced engines have additional spools for sections of the compressor which provides for even higher compressor efficiency. use the fan static efficiency calculation to determine what type of industrial fan is optimal for your application, connect with one of our application engineers, Industrial Fan Types and the Fan Static Efficiency Calculation, Choosing the Right Motor Speed for Your Industrial Fan. 1. Fan static and total efficiency (Figure 1) can be plotted along with the fan pressure curves. The curves are based on a specific set of conditions which typically include speed, volume, efficiency, static pressure and power required to drive the fan at the given set of conditions. Brake Horse Power - BHP. Fan efficiency metrics tend to be defined in terms of total pressure. The fan efficiency is the ratio between power transferred to airflow and the power used by the fan. It is a measure of the total mechanical energy added to the air by the fan. The fan efficiency is in general independent of the air density and can be expressed as: μ f = dp q / P (2) where. q = air flow (cfm) SG = Specific Gravity Air (= 1.0) dp inWG = total pressure (in. The fan is designed to produce a pressure difference, and hence force, to cause a flow through the fan.Factors which determine the performance of the fan include the number and shape of the blades. Radial fans are industrial workhorses because of their high static ⦠It indicates how much energy the motor will provide and how much energy the fan will consume given application-specific factors. Both the formulas are used in SI units and in general the work done theory the amount of air handle by a fan against a pressure is called work done and dividing workdone
60â 49â 54â 54â 54â Impeller Dia . Brake horse power - the actual power a fan requires ⦠Second, as communicated earlier, the FEG value is based on the peak efficiency of the fan. The conversion constant for static efficiency is 6343. CAN ANYBODY SHARE THE HOW TO DERIVE FAN EFFICIENCY FORMULA. Why Fan Static Efficiency Matters. 1m³/s = 3600m³/h. This should also include the velocity pressure on the inlet side (if known) that is constant and in-line with the fan. is incorrect, because you need to divide a value expressed in mmwc by 0.102, to convert to Pascals, not multiply ! 1litre/s = 3.6m³/h. FEG . Assuming 100% efficiency AHP is the power required to move a given air volume against a given pressure. Static pressure indicates how much resistance the airflow needs to move through as measured in inches of water gauge (in. Only a minor share of the fans had ⦠The fan shaft passes through the core shaft for mechanical reasons. Existing Static Pressure (in. It can be found by multiplying the Mechanical efficiency by the ratio of the fan static pres-sure to the fan total pressure. They are most useful for determining the impact of extrapolating from a known fan performance to a desired performance. 7.11 BHP 90 . Optimum fan efficiency 21 Witt&Sohn AG Oct-14 c. Use of diffusers Case study, fan selection for static pressure C: fan with diffuser Large distance to STALL Fan is operated at optimum efficiency Recommended selection 22 Witt&Sohn AG Oct-14 Optimum fan efficiency. 4.4 . Using the formula given by Ted as Watt = m3/sec x pressure (pa). psF = fan static pressure, Pa pdF = fan dynamic/velocity pressure, Pa pd = system dynamic/velocity pressure, Pa V = velocity of air, m/sec PWL = sound power level Formulae 1 to 4 can be applied to any fan provided the diameter does not change. Positive static pressure is created as a fan moves air through a system. Multiple-Fan Arrangements 11. 3.8 . Fig 1: FEG Formula . 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