CHP3 2012.2013 Exam Paper
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Transcript of CHP3 2012.2013 Exam Paper
ATHLONE INSTITUTE OF TECHNOLOGY
SCHOOL OF ENGINEERING
SEMESTER 2 EXAMINATIONS 2013
Summer Session
BACHELOR OF ENGINEERING in MECHANICAL ENGINEERING and
RENEWABLE ENERGY
AWARD YEAR
COMBINED HEAT AND POWER 3
External Examiner(s): Mr. Andrew O’Connell
Dr. Fergal Boyle
Internal Examiner(s): Dr. Niall Burke
Instructions to candidates:
Read all questions carefully.
All questions carry equal marks.
Answer Three out of Four questions.
Time Allowed: 2 hours
No. of pages including cover sheet: 12
Q.1 (a) In evaluating the economic viability of Combined Heat and Power Systems,
what is meant by the term “Spark Spread”?
(4 marks)
(b) What are the four strokes of an Otto cycle?
(4 marks)
(c) What are the conversion steps in transforming bio-energy into electrical
energy?
(4 marks)
(d) What are the typical CO2 emissions for a natural gas CHP system and how
does this compare with the CO2 emissions from national grid generated
electricity.
(4 marks)
(e) What is the difference between a heat engine and a heat pump?
(4 marks)
[20/60 marks]
Q.2 (a) Explain how a Combined Heat and Power (CHP) system operates and what
applications are CHP systems best suited.
(4 marks)
(b) What are the key contributors to the economic success of a CHP system?
(6 marks)
(c) Explain in detail, with the aid of a diagram, the components of a gas micro-
turbine, and evaluate the applications for this system.
(10 marks)
[20/60 marks]
Q.3 (a) Under what conditions may a gas turbine CHP system be an appropriate
choice for a site?
(6 marks)
(b) In the Brayton Cycle shown in the figure, calculate the maximum efficiency
that can theoretically be achieved using the temperatures provided.
(4 marks)
(c) Air enters the compressor of a gas turbine at 100kPa and 25°C. For a pressure
ratio of 5 and a maximum temperature of 850°C determine the back work ratio
and thermal efficiency using the Brayton cycle.
(10 marks)
[20/60 marks]
Fuel in
AC Power 33% Generator
1100°C
500°C
Exhaust Gases 67%
~20°C
Q.4 (a) Explain where heat is recovered on a reciprocating engine CHP system.
(4 marks)
(b) Detail some of the design characteristics/features that have made reciprocating
engines a leading prime mover for CHP systems.
(6 marks)
(c) A simple steam power plant operates on 30 kg/s of steam, as shown in Figure
1.
Neglecting losses in the various components, calculate:
(i) The boiler power input, ��� (2 marks)
(ii) The turbine power output, �� � (2 marks)
(iii) The condenser output, ��� (2 marks)
(iv) The pump power requirement, �� � (2 marks)
(v) The thermal efficiency and Carnot efficiency of the cycle. (2 marks)
[20/60 marks]
Figure 1
10 MPa
10 MPa 10 kPa
10 kPa
40 °C
40 °C
600 °C
TABLE 1.1
Supporting information extracted from “Steam – its generation and use”, 40th edition, edited by S.C. Stultz and J.B. Kitto
TABLE 1.2
Supporting information extracted from “Steam – its generation and use”, 40th edition, edited by S.C. Stultz and J.B. Kitto
TABLE 1.3
Supporting information extracted from “Steam – its generation and use”, 40th edition, edited by S.C. Stultz and J.B. Kitto
TABLE 2
Supporting information extracted from “Steam – its generation and use”, 40th edition, edited by S.C. Stultz and J.B. Kitto
TABLE 3
Supporting information extracted from “Thermodynamics for Engineers” by M.C. Potter and C.W. Somerton.
TABLE 4
Properties of Water (saturated Liquid)
Supporting information extracted from “Heat Transfer”, 9th edition by J.P. Holman
TABLE 5
Properties of Air at Atmospheric Pressure
Supporting information extracted from “Heat Transfer”, 9th edition by J.P. Holman