How do you calculate polytropic head?
Units of Polytropic Head – The polytropic head can be expressed in ‘metres’ or ‘kJ/kg’ or ‘N.m/kg’. The conversion is 1 kJ/kg = 102.04 m. Therefore in this case the compressor head which was calculated as 173.7 kJ/kg is 17,720 m.
What is the polytropic head?
The Polytropic Head is an expression used for dynamic compressors to denote the foot-pounds of work required per pound of gas.
What is the polytropic efficiency?
The polytropic efficiency—also called “small-stage efficiency”—is defined as the isentropic efficiency of an elemental (or differential) stage in the process such that it is constant throughout the whole process.
How do you calculate suction and discharge pressure of a compressor?
Compression process. Compression ratio (R) – is the pressure ratio at discharge to suction pressure: R = Pd/Ps (where Pd and Ps are absolute). One stage compressor has only one R value.
What is Polytropic process and derive equation of work done in Polytropic process?
The specific heats will be discussed later. Notice that the results we obtained for an ideal gas undergoing a polytropic process when n = 1, is identical to that for an ideal gas undergoing the isothermal process….The Polytropic Process:
| Process | Exponent n |
|---|---|
| Isothermal & ideal gas | 1 |
| Adiabatic & ideal gas | k = CP/CV |
Is polytropic isothermal?
Isothermal process are a subset of the polytropic. Polytropic encompass all other common processes and more. standard notation implying C is a constant, P the pressure and V the volume.
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).
What is polytropic process and derive equation of work done in polytropic process?
How do you calculate the 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.
What is polytropic factor?
A polytropic process is a thermodynamic process that obeys the relation: where p is the pressure, V is volume, n is the polytropic index, and C is a constant. The polytropic process equation can describe multiple expansion and compression processes which include heat transfer.
How is the isentropic head and polytropic head calculated?
The isentropic head is calculated by equation 3A: Similarly, the polytropic head is calculated by equation 3B: The actual discharge temperature based on the isentropic path is calculated by equation 4A. The actual discharge temperature based on the polytropic is calculated by equation 4B.
How to calculate the discharge temperature of a polytropic head?
Polytropic Head. However, in short to calculate the discharge temperature T2=T1*r^ ( (n-1)/n) where r is the pressure ratio As you have the mass flow calculate the density at suction conditions from P1/ (Z1*R*T1) where R is the Gas Constant. Volumetric flow at suction conditions is then mass flow divided by suction density.
How is volumetric flow determined in a polytropic head?
Polytropic Head. Volumetric flow at suction conditions is then mass flow divided by suction density. Be careful with your units as you are quoting imperial (English/US) units in your first post, then SI in your second.