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References |
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References |
Sunoba Renewable Energy Systems |
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The first part
relates to scientific articles (unpublished, Journal, Conference), then
follows a list of Technical Reports. |
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[1] N.G. Barton, “A Heat
Engine and Heat Pump based on the Bernoulli Effect”, 18 pp, Sunoba Pty Ltd
(2006). Abstract: This paper
investigates a device based on the Bernoulli effect for a compressible gas,
which can be configured either as a heat engine or heat pump. The Bernoulli effect shows there is a drop
in pressure, temperature and density when gas accelerates isentropically
in a narrowing section of a duct. If
heat is removed from the gas in the high--speed section before the flow is
transferred isentropically to the outlet, there
will be surplus pressure to drive a turbine once the gas has been slowed.
That is, the device can act as a heat engine.
Conversely when heat is transferred to the high-speed section, the
device can act as a heat pump. Presented
herein is a one-dimensional thermodynamic model to predict the performance of
the proposed heat engine and heat pump.
Also presented are budgets for enthalpy and entropy increments, which
confirm that the engine is in agreement with the second law of thermodynamics. The devices operate with Carnot efficiency
and Carnot coefficient of performance provided the amount of heat transferred
is small. |
Available
on request. |
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Abstract: The
Bernoulli effect for a compressible gas shows there will be a drop in
pressure, temperature and density when the gas accelerates in a narrowing
section of a duct. If the inlet air is
hot and dry, spray evaporation of water in the high-speed section leads to
increased pressure and density and decreased temperature and air speed. If the air is then slowed isentropically without flow separation, the outlet
pressure will be greater than the inlet pressure, thus enabling power
off-take through a turbine. That is
the principle of the Bernoulli evaporation turbine. If the
inlet air is cool and moist, the Bernoulli effect leads to rapid condensation
of microscopic water droplets in the high-speed section and release of latent
heat. This causes decreased pressure
and density and increased temperature and flow speed. If the droplets are collected and thereby
prevented from re-evaporation as the flow is isentropically
slowed without flow separation, the outlet temperature will be greater than
the inlet temperature. It is necessary
also to provide power to extract the air from the flow device. That is the principle of the Bernoulli
condensation heat pump. This paper
presents a thermodynamic model for the proposed engine/heat pump. Illustrative results are also
presented. Although the engine
operates with low efficiency, it theoretically would provide energy in a
sustainable way from inputs that are cheap and readily available. |
Comment:
This unpublished note is an extension of [1] for the case where evaporation
or condensation provides heat transfer in the low-pressure zone. Can these Bernoulli devices be
constructed? Opinions differ. Our view is that the devices are probably
impossible, but not certainly so, and with a clear-cut answer requiring
brilliant and painstaking CFD design work.
If the Bernoulli devices do in fact work, the implication is that
expansion and re-compression take place without mechanical intervention -- a
striking result. Moreover, the
Bernoulli devices would involve continuous flow, not a batch process as in
reciprocating engines. The results
underestimate the theoretically possible performance of the devices, since
evaporation during re-compression is neglected for the heat engine as is
condensation during expansion for the heat pump. Available
on request. |
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Abstract: This paper investigates a heat engine designed to produce power and a
cool moist exhaust from evaporative cooling of hot dry air at reduced
pressure. Theoretically, the
thermodynamic cycle underpinning the engine is a low-pressure Brayton cycle,
which can be manifested in various ways.
Of these alternatives, the simplest from an engineering standpoint is
a two-stroke reciprocating piston arrangement. A thermodynamic model for the engine is presented
and applied to the case where the inlet air is pre-heated. Under suitable weather conditions, and
assuming evaporation to saturation at constant volume in the low-pressure
section and no further evaporation, the theoretical result is that the engine
converts approximately 4-5% of energy collected at 30-40oC above
ambient into electrical or mechanical power.
Whilst this efficiency is not high, the inputs will be inexpensive
since the requisite pre-heating can be accomplished by passive solar methods,
and hot air is both the heat transfer medium and the working gas. The engine does not require heat exchangers
or condensers as with Rankine cycle engines. An estimate is also made for the nett power produced with pre-heating by the engine per
hectare per year under typical conditions in inland Australia. Assuming pre-heating by 30oC,
the estimate is 417 MWhr/(Ha.yr). |
Comment:
This unrefereed conference paper contains early
theoretical results on the BEE.
Evaporation during compression, which is a significant source of
available work, is not included.
Results based on evaporation during re-compression were however shown
in the actual conference presentation.
Available
on request. |
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[4] N.G. Barton, “An Evaporation
Heat Engine and Condensation Heat Pump”, The
ANZIAM J, Vol 49 (2008), 503-524. Abstract: This paper presents a thermodynamic model for a
heat engine based on evaporative cooling of unsaturated air at reduced
pressure. Also analysed is a related
heat pump based on condensation of water vapour in moist air at reduced
pressure. These devices operate as
two-stroke reciprocating engines, which are their simplest possible
embodiments. The mathematical models for the two devices are
based on conservation of mass for both air and water vapour, ideal gas laws,
constant specific heats, and, as appropriate, either constant entropy
processes or cooling/heating by evaporation/condensation. Both models take the form of coupled algebraic
systems in six variables, which require numerical solution for certain stages
of the cycle. The specific work output of the heat engine
increases as the inlet air becomes hotter and as the expansion ratio of the
engine increases. The engine provides
evaporative cooling of air from inlet to outlet. The heat pump has a good coefficient of
performance, which decreases as the expansion ratio increases. The heat pump also has the effect of drying
the air from inlet to outlet, producing distilled water as a by-product. |
Comment:
This refereed journal paper contains full thermodynamic models for the BEE
and BDE devices based on two-stroke reciprocating engines. Evaporation during re-compression is
included in the BEE model, as is condensation during expansion in the BDE
model. According
to copyright agreement, a PDF copy of the paper can be provided to researchers for their personal use,
provided that they do not make the file available to anyone else. For
further information, please visit the publisher’s website. |
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[5] N.G. Barton,
“Experimental Results for a Heat Engine Powered by Evaporative Cooling of Hot
Air at Reduced Pressure”, in Proc Australian and New Zealand Solar
Energy Society Conference, Sydney, 26-28 November 2008. Abstract: This paper describes the design, construction and
first trials for an experimental heat engine based on a novel thermodynamic
cycle. Design work on the engine
started in mid 2007 and construction was completed in April 2008. After various modifications, successful
trials first occurred in August 2008. The thermodynamic cycle is thought to be completely
new and was developed during an investigation into power generation based on
passive solar heat collection. The
cycle involves intake of hot unsaturated air, expansion, evaporative cooling
at constant volume, re-compression with further evaporation, and exhaust of
cool saturated air. In the
experimental engine, this cycle is realised with a piston-in-cylinder
mechanism. Successful trials of the engine have occurred for
inlet air temperatures as low as 70°C, thereby offering support to the
overall concept and the thermodynamic analysis. Weaknesses in the design concept have been
identified and recommendations made for improved performance. Immediate future plans involve development
of a combined-cycle engine in which the new evaporation cycle is integrated
with the Brayton gas power cycle. The
target market for this development is the provision of Combined Heat and
Power for medium-sized buildings. The
original goal of power generation directly from hot air remains under
consideration for commercial development. |
Comment:
This refereed conference paper contains details of the experimental BEE and
its first successful trials. Available
on request. |
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Technical Reports If
you make it this far into the web site, you really must be interested in my work. What follows is a list of Technical Reports
I’ve written on this project. If you
want to know more, then please e-mail
me. The Technical Reports can be made
available to potential investors or approved collaborators under
Non-Disclosure Agreement. |
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2007-1 Droplet evaporation tests
at constant volume 2007-2 Leakage/friction tests for
the experimental BEE 2008-1 The experimental BEE –
design, construction and first trials 2008-2 The experimental BEE –
further trials 2008-3 The experimental BEE –
successful trials 2009-1 Simulation of the BEE with
Scotch Yoke 2009-2 Numerical simulation of
droplet evaporation 2009-3 BEE and BDE technology
overview 2009-4 Conceptual design for a 6
kg clothes dryer that incorporates the BDE 2009-5 Simulation of the BEE with
crosshead 2009-6 Prototype BEE –
requirements and concept 2010-1 Simulation of incomplete
evaporation for BEE re-compression; Tinlet = 200°C |
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© Sunoba Pty Ltd 12 March 2010 |
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