# Phase Capacitor - Facilities and Environmental Engineering - Past Exam Paper, Past Exams for Environmental Science

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Main points of this past exam are: Phase Capacitor, Poor Power Factor, Electricity Costs, Power Factor Measured, Motor Draws, Apparent Power, Reactive Power, Absorbed, Capacitor, Line Current
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Microsoft Word - EAMTE_8_Y4 Facilities & Environmental Engineering.doc

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CORK INSTITUTE OF TECHNOLOGY INSTITIÚID TEICNEOLAÍOCHTA CHORCAÍ

Semester 2 Examinations 2008/09

Facilities & Environmental Engineering

Module Code: MECH 8006

School: Mechanical & Process Engineering Programme Title: BSc Advanced Manufacturing Technology BSc Process Plant Technology Programme Code: EAMTE_8_Y4 EPPTE_8_Y4 External Examiner(s): Mr. Neil Kingston, Mr. Joe Phelan Internal Examiner(s): Mr. Michael P O’Mahony Instructions: Answer THREE QuestionsDuration: 2 hours Sitting: Summer 2009 Requirements for this examination:Note to Candidates: Please check the Programme Title and the Module Title to ensure that you have received the correct examination paper. If in doubt please contact an Invigilator.

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Q1. (a) Explain why a poor Power Factor can increase a company’s electricity costs. How is the

power factor measured? (8 Marks)

(b) A motor draws 75kW from a 3-phase line at 0.72 power factor lagging. Calculate the

Apparent power and Reactive power absorbed by the motor.

If a 20kVar 3-phase capacitor is connected in parallel with the motor, what is the new

power factor.

Calculate the percentage drop in line current after the capacitor is installed. (10 marks)

(c) The LUMEN METHOD is frequently used in lighting installation design, and is

expressed by:

lumens MFUF AE

Explain each of the terms used in the above equation (10 Marks)

(d) A store room of 12x15m is lit by fluorescent tubes, 125W, with efficacy of 70lm/W.

Assuming a MF of 0.7 and UF of 0.5, estimate the power consumption which will

provide an average illumination level of 200 lx (5 Marks)

Q2 (a) The compressed air demand from a facility usually varies significant through any given

day. Explain the how this can be accomadated by the compressed air system (8 Marks)

(b) A pneumatic ring main is supplies a plant with an average demand of 20m3/min FAD.

The minimum working pressure at the receiver is 5 bar gauge. The air compressor has a

rated delivery of 35 m3/min at a working pressure of 7 bar gauge. The controls switch the

compressor off load when the receiver pressure reaches 7 bar gauge and back on when it

drops to 5 bar gauge. If the max allowable compressor starts per hour is 20, determine a

suitable receiver capacity (10 Marks)

(c) It is believed that compressed air is cheap, and as a result waste and leaks are tolerated.

Discuss, explaining why compressed air is used and approaches to minimise leaks in the

system.

(15 marks)

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Q3 The central thrust of the Safety, Health and welfare at Work Act 2005 is encapsulated in

9 general Principles of Prevention. Discuss SIX of them. (12 Marks)

A safety statement is a requirement of the Act, what is it and what should be contained

within it? (21 Marks)

Q4 (a) List FOUR of the Water induced Problems that may be experienced by industry and

explain in detail how incoming water is treated to control TWO of these. (14 marks)

(b) In wastewater treatment, detail the factors upon which the efficiency of the primary

settlement tank is dependent. (10 Marks)

(c) Design a grit chamber to remove sand particles, density 2650 kg/m3 with a mean diameter

of 0.21 mm. Assume the sand is spherical and the wastewater has density and dynamic

viscosity of 998kg/m3 and 1x10-3 PaS respectively. The wastewater flow is 10,000

m3/day. A velocity of 0.3 m/s will be automatically maintained, and the depth must be

1.5 times the width at maximum flow

Stokes’ Law µ ρρ

18 )( 2dg

v ss

=

(9 Marks)

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