Experimental rankine cycle engine designed for heat recovery from exhaust gases of industrial plants. Final report

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COMMISSION OF THE EUROPEAN COMMUNITIES
energy
Experimental rankine cycle engine designed
for heat recovery from exhaust gases of
industrial plants
Blow-up from microfiche original
EUR 7159 EN COMMISSION OF THE EUROPEAN COMMUNITIES
energy
Experimental rankine cycle engine designed
for heat recovery from exhaust gases of
industrial plants
G. CIPOLLA
Fiat Research Centre
Strada Torino, 50
-10043 Orbassano (Turin-Italy)
Contract No 383-78-4 EEC
FINAL REPORT
Directorate-General for Research, Science and Education
1981 EUR 7159 EN Published by the
COMMISSION OF THE EUROPEAN COMMUNITIES
Directorate-General
Information Market and Innovation
Bâtiment Jean Monnet
LUXEMBOURG
LEGAL NOTICE
Neither the Commission of the European Communities nor any person acting
on behalf of then is responsible for the use which might be made of
the following information
'ECSC-EEC-EAEC, Brussels · Luxembourg, 1981
Printed in Luxembourg
Catalogue number: CD-ND-81-029-EN-C Centro Ricerche Fiat sPn
SUMMARY
This report describes the ^development of, and the results obtained from, an
Organic Rankine Cycle (ORC) engine in order to assess its feasibility; the
subject research program is the extention of the activities carried out in
the frame of the previous EC Contract n° 196-76-EEI.
In particular the following activities have been carried out:
. engine and test rig design and set up
. working fluid and thermodynamic cycle choice
. engine performance and mechanical behaviour evaluation
. laboratory investigation on chemical compatibility and thermal stability
of the candidate working fluids.
Engine performance has been evaluated using two different fluids: Freon 11
and perfluorohexane.
The main results of the experimental investigation performed are :
. engine performance in good agreement with the calculated values
. mechanical behaviour of main components almost satisfactory
. working fluid problems: Freon 11 in fact has proved not to be completely
reliable in the higher temperatures range, but Very interesting from the
performance point of view. Perfluorohexane, on the other hand, has shown
very good stability up to 250°C, but it isn't fit for a simple non-regene
rative cycle engine and very expansive.
From the foregoing it appears that ORC engine feasibility has been demon­
strated and tests carried out have shown the reliability of the analytical
evaluation methods developed in order to design an ORC engine. Further de­
velopment work is strongly needed in the area of the working fluid.
EUR 7159 EN
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CONTENTS
1. INTRODUCTION Pag. 1
Pag. 2. ENGINE AND TEST PLANT DESCRIPTION 1
Pag. 3. WORKING FLUID AND THERMODYNAMIC CYCLE CHOICE 2
Pag. 4. ACTIVITY CARRIED OUT AND RESULTS 2
Pag. 4.1 Engine performance evaluation 2
Pag. 3 4.2 Mechanical behaviour
Pag. 3 4.3 Laboratory tests of working fluid compatibility
Pag. 4 4.4 Development of the control system
Pag. 5 5. ECONOMIC ASSESSMENT
Pag. 6. CONCLUSIONS 5
7. LIST OF REFERENCES Pag. 6
Pag. 7 8. ANNEXES
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­ 1 ­
INTRODUCTION
In many situations flows of gases at high temperatures are ventilated to
the enviroment. This situation is met in the process industries as well
as in the conversion of energy to electricity in the form of the exhaust
gases of heat engines. These hot gases have the potential to produce me­
chanical energy and one of the means to realize this is the Organic Rankine
Cycle engine (ORC engine).
The aim of this project is to develop a range of units suitable for ap­
plication in different areas. The proDosed work is a continuation of the
previous one, executed in the frame of the E.C. Energy Conservation Pro­
gramme under contract n° 19­6­76­EEI (1), which gave the following re­
sults (see ref. [ l] + [5] ):
. the experimentally obtained value for the efficiency of the ORC engi­
ne using Freon 11 was 14.1% at an expander inlet temperature of 238°C.
This was very close to the theoretically calculated value (~15%);
. the high pressure fluid pump and the rotating sealing of the turbine
did not work satisfactorily, but a solution to these problems has been
found out;'
. the fluid (Freon 11) was not chemically stable somewhere above 200°C.
This caused the formation of HC 1 and serious corrosion in different com
ponents of the engine.
Aim of the research program in regard to the new contract n° 383­78­4EEI,
has been to extend and complete the activities carried out in conjunc­
tion with the development of the subject Rankine cycle by enlarging the
investigation on the working fluids suitable for these applications.
2. ENGINE AND TEST PLANT DESCRIPTION
Engine and test equipment were the same as those used in the previous te
sts with Freon 11 under the former EEC Contract (see ref. [ 5 J ).
However, few variations were introduced in order to optimize working
fluid piping lay­out and to introduce some modified components (i.e. new
condenser and boost pump). The detailed description of the test plant and
engine variations and the characteristics of the available facility are
given in annex Β , together with the measuring set­up adopted.
(1) The activity of CRF in the Organic Rankine cycle engines, in the frame
of the E.C. Energy Conservation programme, has covered a period of "^3.5
years; i.e.: the Contract n° 196­76­EEI for the period 1.7.76­31.3.73; and
the Contract n° 383­78­4 EEI for the period 1.4.78­31.12.79.
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- 2 -
3. WORKING FLUID AND THERMODYNAMIC CYCLE CHOICE
Owing to stability problems encountered with Freon 11, an alternative
fluid (perfluorohexane or CgF^4) was adopted for the following reasons:
. very good stability at high temperature (up to 350°C) has been demon
strated from the laboratory tests carried out (see § 4.3);
. specific work is low, which means that expansion can take place in a
single turbine stage at low peripheral speed;
. the cycle can be hypercritical; as a consequence, during the vaporiza­
tion phase heat is absorbed by the working fluid at increasing tempera
tures, so that optimum matching is accomplished between the Rankine cv_
cle heat absorption line and the gases heat transfer line and the ga­
ses may be cooled down to lower temperatures.
Unlike the Freon 11 cycle, the perfluorohexane conditions at turbine e-
xit are very far from the saturated vapour curve; as a consequence, high
overall efficiencies can be obtained only by means of thermal regenera -
tion, according to the scheme of fig. 1.
In the hypothesis of maintaining the same engine main components as with
Freon 11, a new cycle was defined using perfluorohexane as working fluid,
as described in Annex A .
The relevant cycle is reported in fig. 2 one thermodyna­
mic map, together with the engine characteristics; fig. 3 reports the per
formance and operating conditions at partial loads (2).
4. ACTIVITY CARRIED OUT AND RESULTS
The following activities have been carried out:
a. Engine performance and main components mechanical behaviour evalua­
tion;
b. Laboratory investigation on the thermal stability and chemical compa­
tibility of the working fluid under simulated operational conditions;
c. Developments of the control system.
4.1 Engine performance evaluation (with perfluorohexane)
Engine tests were carried out using the non-regenerative cycle compo­
nents adopted for the former tests with Freon 11 (fig. 4). Owing to this
fact, regeneration heat was introduced in the boiler by hot gases and e
liminated in the condenser: at engine full-load, heat supply of the non
- regenerative cycle increases from 64.5 kcal/s to 102 kcal/s (fig. 2).
(2) Partial load is defined as the ratio between the "actual" and the "de
sign point" heat supply (64.5 kcal/s = 270 kJ/s for the perfluorohexane re-
generalive cycle).
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