A Proposal on Heat Engines, a topic in Chemical Engineering Thermodynamics. This work aim at studying the process involved in the conversion of heat energy to mechanical work and in effect the principles which engine operate. Heat engines are systems that convert heat or thermal energy to mechanical energy which can then be used to do mechanical work. This is done basically by bringing a working substance from a higher state temperature to a lower state temperature. The working substance is brought to a high temperature by a heat source which generates thermal energy. This energy is converted to work by exploiting the proportion of the working substance during which the heat is transferred to the colder destination until it reaches a lower temperature state. The conversion of this heat to mechanical work follow certain routes which ends at the start point and hence are called cycles. This work will in essence focus on these cycles. Otto cycle, Atkinson cycle and brayton cycle are some of the cycle that represent models for heat engine operations. The condition to which the working fluid is subjected in the process, is what distinguishes one cycle from the other.

1. GROUP 4 ’S PROPOSAL
NAME MATRICULATION NUMBER
BRIGHT CYRIL OMOREGIE ENG1002112
CHIAJUYA ANTHONY CHUKWUKA ENG1002113
EBIKADE EBAKOLE MICHEAL ENG1002115
EBIRERI OGHENERUKEVWE GLORY ENG1002116
EDAFE COLLINS EFEJIRO ENG1002118
EFEROBOR EBENEZER ENG1002119
EKHATOR PROSPER ENG1002121
CHUKWUDI EMEKA DESTINY ENG1004285
CONTENT
 EXECUTIVE SUMMARY
 INTRODUCTION
 AIM AND OBJECTIVES
 JUSTIFICATION
 METHODOLOGY
 CONCLUSION
 REFERENCES

2. EXECUTIVE SUMMARY
This work aim at studying the process involved in the conversion of heat energy to
mechanical work and in effect the principles which engine operate.
Heat engines are systems that convert heat or thermal energy to mechanical energy
which can then be used to do mechanical work. This is done basically by bringing a
working substance from a higher state temperature to a lower state temperature. The
working substance is brought to a high temperature by a heat source which generates
thermal energy. This energy is converted to work by exploiting the proportion of the
working substance during which the heat is transferred to the colder destination until it
reaches a lower temperature state.
The conversion of this heat to mechanical work follow certain routes which ends at the
start point and hence are called cycles. This work will in essence focus on these cycles.
Otto cycle, Atkinson cycle and brayton cycle are some of the cycle that represent
models for heat engine operations. The condition to which the working fluid is subjected
in the process, is what distinguishes one cycle from the other.
INTRODUCTION
Heat is a form of energy that is transferred from one body to another as a result of a
difference in the temperatures of the bodies. The effect of the transfer of energy is
usually (but not always) an increase in the temperature of the colder body and a
decrease in the temperature of the hotter body (the exception being during phase
change).
An engine is a machine designed to convert energy into useful mechanical motion. The
energy is obtained usually from the burning or consumption of fuel and the work is
performed by exerting a torque or linear force to drive machinery that generates
electricity, pumps water or compress gas.
In thermodynamics, a heat engine is a system that performs the conversion of heat or
thermal energy to mechanical energy which can then be used to do mechanical work. It
does this by bringing a working substance from a higher state temperature to a lower
state temperature. A heat “source” generates thermal energy that brings the working
substance to the high temperature state. The working substance generates work in the
“working body” of the engines while transferring heat to the colder destination until it
reaches a low temperature state. During this process, some of the thermal energy is

3. converted into work by exploiting the properties of the working substance. The working
substance is usually a gas or liquid
Heat engines distinguish themselves from other types of engines (e.g. electric motor,
physically powered motor, etc.) by the fact that their efficiency is fundamentally limited
by Carnot’s theorem, which specifies the limits on the maximum efficiency any heat
engine can obtain which solely depends on the difference between the hot and cold
temperature reservoir. Thermodynamics is basically the study of the relationships
between heat and work. The first and second laws of thermodynamics constrain the
operation of a heat engine. The first law is the application of conservation of energy to
the system, and the second sets limits on the possible efficiency of the machine and
determines the direction of energy flow.
Heat engines such as automobile engines operate in a cyclic manner, adding energy in
the form of heat in one part of the cycle and using that energy to do useful work in
another part of the cycle.
Fig. 1
Heat engines in thermodynamics are often modelled using standard engineering models
which are referred to as the “heat engine cycles” such as the Otto cycle, Atkinson cycle,
Brayton cycle, etc. In reality, very few actual implementations of heat engines exactly
match their underlying thermodynamic cycle and as a result one could say that a
thermodynamic cycle is an ideal case of a mechanical engine. In any case, fully
understanding an engine and its efficiency requires gaining a good understanding of the
(possibly simplified or idealized) theoretical model, the practical nuances of an actual
mechanical engine, and the discrepancies between the two.

4. In general terms, the larger the difference in temperature between the hot source and
cold sink, the larger the potential thermal efficiency. Also, the heat which cannot be
used to do work is exhausted.
Examples of heat engines are Refrigerator, Carnot cycle, dual pump, diesel engines.
Examples of everyday heat engines include the steam engine (for example in trains), the
diesel engine, and the gasoline (petrol) engine in an automobile.
Heat engine processes.
Cycle
Process 1-2
(Compression)
Process 2-
3
(Heat
Addition)
Process 3-4
(Expansion)
Process 4-
1
(Heat
Rejection)
Notes
Power cycles normally with external combustion - or heat pump cycles:
Bell
Coleman
adiabatic isobaric adiabatic isobaric A reversed Brayton cycle
Carnot isentropic isothermal isentropic isothermal Carnot heat engine
Ericsson isothermal isobaric isothermal isobaric
the second Ericsson
cycle from 1853
Rankine adiabatic isobaric adiabatic isobaric Steam engine
Hygroscopic adiabatic isobaric adiabatic isobaric Hygroscopic cycle
Scuderi adiabatic variable
pressure
adiabatic isochoric

5. and
volume
Stirling isothermal isochoric isothermal isochoric Stirling engine
Stoddard adiabatic isobaric adiabatic isobaric
Power cycles normally with internal combustion:
Brayton adiabatic isobaric adiabatic isobaric
Jet engines
the external combustion
version of this cycle is
known as first Ericsson
cycle from 1833
Diesel adiabatic isobaric adiabatic isochoric Diesel engine
Lenoir Isobaric isochoric adiabatic
Pulse jets
(Note: Process 1-2
accomplishes both the heat
rejection and the
compression)
Otto adiabatic isochoric adiabatic isochoric Gasoline / petrol engines
Each process is one of the following:
 isothermal (at constant temperature, maintained with heat added or removed from a heat source
or sink)
 isobaric (at constant pressure)
 isometric/isochoric (at constant volume), also referred to as iso-volumetric

6.  adiabatic (no heat is added or removed from the system during adiabatic process)
 isentropic (reversible adiabatic process, no heat is added or removed during isentropic process)
AIMS AND OBJECTIVES
The aim of this work is to study in details the different processes (cycles) involved in the
conversion of heat energy to mechanical work.
Objectives
 To review the concepts of heat and heat engines.
 To study heat engine cycles.
 To compare the different heat engine cycles as well as their applications.
JUSTIFICATION
Doing this work will give a knowledge of the sequence of steps involved in the
conversion of heat to mechanical work as well as the limitation of each step and how
they differ from one another.
Although the term heat engine, is a common one, this work seeks to explain the actual
operations that take place during the conversion of heat to mechanical work.
Also gives us a knowledge about how the wrong timing of the engine cycle (fuel being
blown up at an inappropriate time either early or late) which could be caused by the
piston slapping next to the side of the engine cylinder walls could lead to catastrophic
engine failure. Improved engine design and more precise ignition timing steadily
improves engine efficiency. The study of the idealistic cycle gives an analysis and a
picture of the specific process in order to get a particular output.

7. METHODOLOGY
In carrying out this work, a theoretical review of heat engine and heat engine cycles is to
be done.
In order to make the subject (processes involved in) clearer, motion pictures will be
employed to provide a vivid illustration of these operations.
If possible, we also hope to show live displays of some components in heat engine for
easier comprehension and assimilation.
CONCLUSION
Even with the aforementioned limitations. Heat engines have an advantage over other
types of engines in that most forms of energy can be easily converted to heat by
processes like exothermic reactions (e.g. combustion). Since the heat source that
supplies thermal energy to the engine can be powered by virtually any kind of energy,
heat energy are very versatile to have a wide range of applicability.
Heat engines are often confused with the cycles they attempt to mimic. Typically
engines refer to physical device.
REFERENCES
 J.M. Smith, H.C. Van Ness & M.M. Abbott 2011, “production of power from heat”, 6th
Edition,
McGraw Hill, New York.
 http://en.wikipedia.org/wiki/Thermal_energy
 http://en.wikipedia.org/wiki/Heat_engine
 Yunus A. Cengel, Michael A. Boles 2001, “Thermodynamics: An Engineering Approach",
Mcgraw-Hill College; 4th edition (June 2001)