How do you calculate work done by a compressor? For compressors work is calculated by dividing the enthalpy difference (Δht), from (8), by a mechanical efficiency ( η m c = 97 % ) . Polytropic head (Δhp) is calculated using the difference in entropy (ΔS) and temperature (ΔT), as shown in (9).
How do you calculate the power of a compressor?
Power Calculations. The theoretical power requirements are independent of compressor type; the actual power requirements vary with the compressor efficiency. In general the power is calculated by: where mass flow rate and h is specific enthalpy.
How to calculate the ideal work requirement of a compressor?
Determination of the ideal or isentropic (reversible and adiabatic) enthalpy change of the compression process. The ideal work requirement is obtained by multiplying mass rate by the isentropic enthalpy change. Adjustment of the ideal work requirement for compressor efficiency. The step-by-step calculation based an EOS is outlined below.
How do you calculate work done by a polytropic compressor?
For compressors work is calculated by dividing the enthalpy difference (Δht), from (8), by a mechanical efficiency ( η m c = 97 % ) . Polytropic head (Δhp) is calculated using the difference in entropy (ΔS) and temperature (ΔT), as shown in (9). Click to see full answer.
How do you find the equation for gas compression?
If n=γ=C P /C V, the compression is adiabatic compression (no heat exchange with the surrounding). Most gas compressions generally follow the adiabatic curve. Hence compressor equations are also based on adiabatic curve with n=γ,
What is the work of a compressor?
Air compressors work by forcing air into a container and pressurizing it. Then, the air is forced through an opening in the tank, where pressure builds up. Think of it like an open balloon: the compressed air can be used as energy as it's released.
How do you calculate specific work done?
The specific work can be calculated with (1):w = (p2 - p1) / ρ = ((10 105 N/m2) - (105 N/m2)) / (1000 kg/m3) ... hwater = (900 Nm/kg) / (9.81 kg/s2) = 91.74 (m) water column.w = κ / (κ -1) R T1 [( p2 / p1)((κ-1)/κ) - 1] ... hair = (274200 N m/kg) / (9.81 kg/s2)
What is the mechanical efficiency of a compressor?
The mechanical efficiency varies with compressor size and type, but 95% is a useful planning number. When calculating the compressor head and discharge temperature the efficiency used will be isentropic or polytropic (isentropic efficiency is sometimes called adiabatic efficiency).
Is work done by a compressor positive or negative?
and related questions (2 students) The turbine extracts work from the gas (our system). So the system does work when passing through a turbine (positive work). The opposite is true of a compressor. The system has work done on it (negative work).
How do you calculate work when pressure changes?
0:194:42Work Done by a Gas During Pressure and Volume Change - YouTubeYouTubeStart of suggested clipEnd of suggested clipWork is by multiplying the force times the displacement.MoreWork is by multiplying the force times the displacement.
How do you calculate the work done by a piston?
The amount of work done is equal to the product of the force exerted on the piston times the distance the piston is moved. The pressure (P) the gas exerts on the piston is equal to the force (F) with which it pushes up on the piston divided by the surface area (A) of the piston.
How do you calculate mechanical efficiency of a compressor?
Simple Energy Formula: Motor Efficiency = Cost per KW X . 746 (Power Factor) X Hours of operation X Brake horsepower *Note: No electric motor is 100% efficient, most will average 92-95% efficient.
How do I calculate air compressor cfm?
How Do You Calculate CFM for an Air Compressor?Next, convert to standard pressure (ATM). ... Tank Pump-up Time = 1 min 8.4 seconds (1.14 minutes)The three primary factors are: ... CFM = Tank Volume in Cubic Feet x Standard Pressure (ATM) During a Cycle x Cranks per Minute.More items...
How is compressor power measured?
The efficiency of the compressor is known and is 0.72.Step 1 : calculate the mass flow rate.STEP 2 : calculate the discharge temperature.STEP 3 : calculate the isentropic power requirement.STEP 4 : calculate the actual power requirement.
Is work done in compression?
The work done by the mixture during the compression is W=∫V2V1pdV. With the adiabatic condition of Equation 3.7. 1, we may write p as K/Vγ, where K=p1Vγ1=p2Vγ2.
Why is compressor work negative?
Work of compressions is negative for the surroundings, but work of compression is positive for the system, because the system isn't applying any force. Instead, the surroundings are creating the pressure through compressions, making work negative.
Is work done negative during compression?
Positive work is done on the gas when the gas is compressed; negative work is done on the gas when the gas expands.
1. Formula : compressor power calculation
For 1 compressor stage of a perfect gas, the isentropic compression is the following :
3. Example of calculation of the compression power
A compressor has to deliver 2000 Nm3/h of air at 6 bar g, from air at atmospheric pressure and 20°c. The efficiency of the compressor is known and is 0.72.
4. Free Excel calculation tool
You can access a free Excel calculation tool to make the compressor power calculation explained above : Compressor Power Calculator
Important equations for compressor calculations
Gas compression can be expressed in terms of pressure and temperature variation as, PV n = constant
Considering the mechanical efficiency of a compressor
These equations will provide us with theoretical values of the power requirement and the thermodynamic efficiencies of the compression process. But then we also need to account for the mechanical efficiencies and loss of power in driving the compressor equipment as well as the electrical motor.
