Compressor Lab

Topics: Pressure, Fluid dynamics, Orifice plate Pages: 6 (1188 words) Published: April 7, 2011
University of Trinidad & Tobago
S.F.T.I Campus

Lab: Chemical Kinetics

Christopher Boodram
Aketta Wylie
Simeon Mohammed#110004795
Salomon Samaroo #111006223

Program: Chemical Engineering Technology

* Cohort: 11
* Course: Physical Chemistry and Thermodynamics
* Course Code: PCTH210D
* Instructor:

Title : Centrifugal Compressor

The equipment comprises of a 7-stage centrifugal compressor driven by an electric motor mounted on a support plinth. Clear acrylic inlet and outlet ducts are installed on the compressor to allow the air passing through the unit to be monitored. Appropriate sensors are incorporated on the unit to facilitate analysis of the compressor performance when connected to a suitable microcomputer via an IFD Interface Console. In addition to the tappings required by the pressure sensors, additional tappings are included in the ducts to allow appropriate calibration instruments to be connected. The flow of air through the compressor is regulated by a throttle control device installed at the exit of the discharge duct. Rotation of the collar opens and closes a variable aperture which allows the head/flow produced by the compressor to be varied.

Symbol| Term| Units|
dpo| Pressure drop across the orifice plate| N/m2 (Newtons per square meter) displayed as Pa (Pascals) (1Pa = 1N/m2)| Dps| Pressure drop across the compressor| N/m2 (Newtons per square meter) displayed as Pa (Pascals)| N| Rotational speed of the compressor| Hz (Hertz)|

Ta| Air temperature at compressor inlet| º C (Celsius)| Pe| Input power to the motor| W (Watts)|

Symbol| Term| Units|
Pa| Ambient barometric pressure| Pa (Pascals)|
Pi| Physical constant| Dimensionless number|
d| Orifice plate diameter| m (meter)|
Cd| Orifice discharge coefficient| Dimensionless number| g| Gravitational acceleration| m/s2 (meters per second per second)| A1| Cross sectional area of the fan inlet| m2 (square meters)| A2| Cross sectional area of the fan outlet| m2 (square meters)|

Calculated variables
Symbol| Term| Units|
Rho| Density of air| kgm3 (kilograms per cubic meter)|
Qv| Volume flow rate| m3/s (cubic meters per second)|
V1| Velocity in the duct at fan inlet | m/s (meters per second)| V2| Velocity in the duct at fan outlet | m/s (meters per second)| ptF| Fan total pressure produced| Pa (Pascals)|
Pu| Fan power output| W (Watts)|
Egr| Overall efficiency| Percentage|

Formulae Used







To ensure users fully understand the conversion of measured units of quantity to those of the variables necessary to calculate compressor performance.

Theoretical Background:
The basic terms used to define, and therefore measure, compressor performance include (i) Discharge,
(ii) Compressor pressure,
(iii) Power input and efficiencies.

Each of those is considered in turns.

(i) Discharge Qv

The discharge, or flow rate or capacity, of a compressor is the volume of fluid pumped per unit time. In SI units, this is expressed in cubic meters per second, m3/s. The Armfield FM 12 unit employs an orifice plate in the compressor inlet duct to measure Qv, according to the conventional relationship between the measured pressure drop dpo across the orifice and the flow rate:-

Qv=Cd×Pi×d2×2×Rho×dPo4×Rho ………..(4)

Where Cd is the orifice discharge coefficient

The appropriate constants needed to use this equation for deducing discharge Qv from dPo are given in the software. Similarly is the calibration of the orifice necessary to confirm these values of parameters from the software.

(ii) Compressor Pressure
The term ‘compressor pressure’ refers to the sum of the...
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