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More Ideas in Light and Energy - The Blog

Power Fluids – Possible Fluids for Minto Wheels, Rankine Cycles …

All kind of Rankine or steam engines need a suitable  fluid, that reacts to heating with an increase in pressure. The increased pressure of the fluid will be used to drive a piston, a turbine blade, lift a mass … and generate power. In this sense the fluid can be called “power fluid”. The following charts show graphs of the vapor pressure (bar) versus the temperatures (°C) for several fluids. The second chart uses a logarithmic vertical axis. The fluids are:

1. Propan – C3H8
2. Refrigerant R134a
3. N-Butan – C4H10
4. Refgrigerant R254fa
5. Dichlormethan (Methylenchlorid) – CH2Cl2
6. Aceton – C3H6O
7. Methanol – CH4O

The solid red curve shows the pressure rise of normal air resulting from isochoric (constant volume) heating. Note: this is only a limited collection and not all of those fluid have been tested for a steam engine application.




Filed under: cogeneration,minto wheel,rankine engine,thermodyna,Uncategorized — exergia posted 27/08/2012 at 12:18 pm

Energy stored in a pressurized Fluid – The Expansion process

How much mechanical energy, i.e. exergy could one extract from a gaseous, pressurized  fluid at a pressure P1 and temperature T1 when it expands in an adequate engine? We assume the equilibrium the surrounding condition to be P0, T0.

The first question we have to answer is how an ideal gas behaves when it is expanded. The thermodynamic theory of an ideal process without heat input (adiabatic) and without friction (isentropic) yields to a set of the following equations:

P2/P1 = (V1/V2) ^ n
V1/V2 = (P2/P1) ^ (1/n)


V1/V2 = (T2/T1) ^ 1/(n-1)
T2/T1  = V1/V2^ (n-1)


T1/T2 = (P1/P2) ^ ((n-1)/n)
P1/P2 = (T1/T2) ^ (n/(n-1))


The equations relate the initial state 1 characterized by temperature T1, pressure P1 and volume V1 to the final state 2 (T2, P2, V2).  n is characterising the gas and depending related on the heat capacities at constant pressure Cp and at constant volume Cv:

n = Cp/Cv

This ratio is called the isentropic exponent. Here some characteristic values:

  • Mono atomic gas -  Argon: n= 1.67
  • Diatomic gas – nitrogen, Hydrogen , “normal air”: n = 1.4
  • “Multi-atomic” gas – organic fluid – refrigerant R11: n =1.13
  • “Multi-atomic” gas – organic fluid – Butane: n =1.09

The above equations only hold for a situation, where energy is reversible transferred from the gas to a macroscopic body, i.e. a piston.  So the gas is cooled and decreases its temperature. In a situation where an ideal gas freely expands without energy transfer, the temperature will remain constant. In contrast to the isentropic expansion this is a irreversible process.

Using the above equations with  c_exp = V/V1, the expansion ratio, yields to

P(V) = P1  (V1/V) ^ n = P1  c_exp^(-n) = P(c_exp)

The following plot shows the pressure decrease depending on the expansion ration during an expansion process for the four typical fluids Argon,  Hydrogen, refrigerant R11 and Butane. Initial pressure is 10 bar. Note: In technical applications, e.g. characterizing air motors, people normally talk about pressure differences to atmospheric pressure. So a  pressure of 1 bar in a data sheet of an air motor means actually an absolute pressure of 2 bar.

Analogous there is a temperature decrease. The following diagram shows to typical expansion processes: Air is expanded via an air motor starting at low temperature T1 = 25°C , a temperature you  have in a compressed air tank. The second process starts at 100°C a situation that may arise in an Organic Rankine cycle.

T(V) = T1  (V1/V) ^(n-1) = T1  c_exp^(1-n) = T(c_exp)


To calculate the maximal energy we can extract from the pressurized fluid we have to use a total isentropic  process. Isentropic means, that every step of the process has to be reversible and finally the fluid ends with atmospheric conditions (T0,P0). Let’s further assume we are using  an ideal  positive displacement engine, for example a “massive” piston sliding frictionless in a cylinder. The whole process can be divided in 4 steps:

1.) Input process, filling the piston to volume V1

2.) Expansion of  the fluid from V1 -> V2, choose V2 so that the pressure becomes equal to the surrounding atmospheric pressure: P2 = P0

3.) In most of the cases after the expansion the gas temperature T2 is not equal to the surrounding air temperature. So there is  a potential source to extract further exergy via a heat engine: T2 ->  T0

4.) Output exhaust process, emptying the piston in pushing the fluid to the surrounding

The total pressure P-P0 acting on the piston

1.) During the filling process of the empty piston to a volume V1 a total constant pressure of P1-P0 acts on the piston. So we get

L_input = (P1-P0)  V1

2.) The generated mechanical energy is calculated via integrating this pressure over the expansion volume

= Integral(P(V)-P0, V1, V2)
= Integral(P(V), V1, V2) – P0 (V2 – V1)
= 1/(1-n)  P1 V1  ((V2/V1)^(1-n) – 1) – P0 (V2 – V1)

Import point here is, that for an ideal expansion the final volume has to be chosen in a way, that the end pressure after expansion equals the surrounding’s pressure. So:

(V2/V1)^(1-n) = P2 V2/(P1*V1)

and finally

L_expansion = 1/(1-n) (P2 V2 -  P1 V1) – P0 (V2 – V1)
= Cv (T2 – T1) -
P0 (V2 – V1)

3.)  We neglect for the moment

L_heatengine = ?

4.) During the output process after opening the exhaust no force is acting on the piston. So

L_output = 0

The following diagram shows input cycle and expansion work as corresponding areas in the pressure volume chart:


A more intuitive formulation is to transfer to the analogous equations for power instead of energy and normalize by dividing by the input volume flow Vflow1:

Lp_spec_input =  Lp_input/Vflow1 = (P1-P0)


Lp_spec_expansion =  Lp_expansion/Vflow1
= 1/(1-n) (P2 Vflow2/Vflow1 -  P1) – P0 (Vflow2/Vflow1 – 1)

Using the relations for  optimal expansion

c_exp_opti = Vflow2/Vflow1 = (P1/P2)^(1/n)


P0 = P2

yields to

Lp_spec_expansion = 1/(1-n) (P2  c_exp_opti -  P1) – P2 (c_exp_opti – 1)

The following plot shows the two parts of the specific expansion power of air resulting from the input cycle (red)  and isentropic expansion (blue). The blue line shows the sum of both. Let’s see an example: To generate 1000 Watt of mechanical power with an ideal engine you need an air input stream of 1 l/sec at approx. 7 bar. In this case it splits into 600 Watt resulting from the input cycle and  400 Watt from the expansion. For real machines the inlet air consumption may be 3 to 15 times higher.




Filed under: air engine,airmotor,rankine engine,thermodyna — exergia posted 26/04/2012 at 7:14 pm

Thermodynamo – Small sized Organic Rankine Cycle Heat Motor – Notebook


1. Expander

Schlechten Wirkungsgrade der Druckluftmotorn sind bekannt.
“Wirkunggrade” werden gemessen in Kombination Kompressor-Motor
Eingangs-Leisung Kompressor -> Ausgangsleistung Motor
Typisch 8-10 kW -> 1 kW

Realistische Kanditaten für Expander, alle Typen um 1 kW

1.1 Turbine


ITMini Kit ca. 1500 USD
Öl frei, kaum Verschleiß, hohe Drehzahl, schlechter Wirkungsgrad

Deprag Green Energy

Frau Dübbelde Tel. 09621 371 343, 5 – 20 kW Turbine mit Generator, hermetisch!!!

1.2 Lamellen Motor, Rotor Vane

!!! Bei diesem Typ kommt es zu Abrieb, der im  geschlossenen Kreis wieder in den Motor gelangen kann, Filter?
Edelstahl Varianten machen wahrscheinlich nur Sinn bei korrosiven Medien!!!

Schiebermodifikation: Kohlenstoff Lamellen RedOrbit -> Gottschald

Helwig Carbon – Carbon Graphite Vanes


Herr Vogel, Tel. 0640 6832949


Gast NL42, Edelstahl ca. 560 EUR
Öl frei möglich , 2500-4000 Std, 500 -2500 rpm, bis max. 5,6 Bar, bis 120° Umgebungstemperatur

Gast via gopro


TonsonV4, ca. 250 EUR
Öl wird benötigt, begrenzte Lebensdauer, bis max. 6,6 Bar, bis 120° Umgebungstemperatur

Mannesmann via maku

Herr Born bei Maku c.born@maku-industrie.de
MRD 120 1.300 EUR
MU300 1.500 EUR’
Bei10 Stck. ca. 35% Rabatt

Herr Culossa: Verkäufer bei Mannesmann-demag m.culossa@mannesmann-demag.com
Tel. +49 (0) 711 88 718 – 505

MRD 120-9300

Leistung 1,2 kW
Lastdrehzahl  9300 Umdr/min
Lastdrehmoment 1.2 Nm


MU 300-2800

Leistung 2,2 kW
Lastdrehzahl  1/0.6 * 2800 Umdr/min = 4600 Umdr/min (reine Motoreinheit ohne Getriebe)
Lastdrehmoment  0.6 * 7.5 Nm = 4.5 Nm (reine Motoreinheit ohne Getriebe)




Germany – Karrst
Tel: +49 21 31 – 40 16 9263 Herr Ralf Auwelaers
Email: scg.productsupport.zylinder@parker.com

Außendienst: Herr Oland Tel. 07157 3892 od. 0175 5756291

Parker P1v-S1200, Edelstahl, 1,2 kW, ca.
schmierfreie Lamelle, 2100 EUR Listenpreis
“normale” Lamelle -> Öl, 1900 EUR Listenpreis
Lebensdauer ca. 1000 Std. +,  bis 100°,

Parker P1V-A, Stahl, 1,6 kW, ca. 1300 EUR Listenpreis
schmierfreie Lamelle, 1300 EUR Listenpreis
“normale” Lamelle -> Öl, 970 EUR Listenpreis
Lebensdauer ca. 1000 Std. +,  bis 100°

1.3 Drehkolben

pneumatikmotor.de – Krisch Dienst – Armak

Mr. Krisch – Tel. +49 71 54 82 400

Armak, GGP04, ca. 3000 EUR
Öl frei, 5000-8000 Stcd., 15 bar, 150°

GGP von Armak ist lieferbar und wird im ORC Prozeß funktionieren.
Kosten 3.000 EUR, gehe zu hohen Drücken (20 bar) um die Leistungdichte
zu erhöhen und damit die Kosten pro KW zu senken.
Dichtungsproblem  ist wohl noch nicht gelöst. Magnetkopplung oder
Motor-Generator-Einheit in hermetisches Gehäuse.

1.4 Scroll

Air Squared

Air Squared E15H22N4.25, 3000 USD inklusive Magnetkopplung
Öl frei, 13,8 Bar, 175°

2. Working Fluid

!!! Fluid Properties – vapor pressure – engineeringtoolbox.com !!!

Review Kältemittel
R134a (Infinity turbine < 90° Celsius)
R245fa (Infinity turbine > 90° Celsius) – genetron

Dichlormethan – methylene chloride

3. Generator


ME1016: 1000 W, 1000 rpm, 12 VAC | 3000 W, 3000 rpm, 36 VAC
ME1112 PM: 1000-4000 W, 1400-2500 rpm, 160-280 VAC
efficiency about 85%

dvetech PMG für kleine Windräder 0,2 – 20 KW, 200 bis 1200 rpm


GL-PMG-500A: 700 W, 500 rpm, 50V
GL-PMG-1000: 1400 W, 500 rpm, 300 V
efficiency ??

ebay: permanentmagnet+generator

Permanet magnet alternator

smart drive like the on from Ecoinnovation



Ebay Suche nach Windgenerator+Generator

4. Components


Frau Sabrina Trautmann
Tel 07144 206 21 51
Fax 07144 206 38 55

Material für Fluor-Kohlenwasserstoffe V3819-75, Elastomer

Dichtungstechnik Bensheim
Marcus Schofer
Tel. 06251-8415-0


Magnetic coupling

DST Liste
Herr Matwich Tel. 0239461676
Metallischer Spalttopf Verluste bei 1500 Umdr/min 90% bei 3000 Umdr/min 80%, Druck 25 bar
Glasspalttopf Verlustfrei, Druck bis 16 bar
PTFE Dichtungsring

Temperatur abhängig von Magneten: Neodymium bis 150 ° Celsius, Nickel Cobalt bis 350° Celsius
Preis metallisch 2 Nm 190 EUR
Glas 4Nm 287 EUR

Möglicher Kunststoff für Spalttopf PEEK, bedingt PTFE

oder flache Kupplung mit Keramikdeckel z.B. Rescor 914 od. Rescor 915?
Preis Rescor 6mm x 150mm x 150mm ca. 800,- EUR !!!!



Heat exchanger – airec Sweden
– Turkey



Feed Pumps

Sero PumpSystems
Pumpe alcohol-injection

Idea: injection via Venturi effect

Refrigerant, Different Components


Pneumatic Cylinders for Expansion

RS-Online or Ebay
ISO cylinder – Norgren Datasheet
ISO cylinder – Parker Datasheet

5. Forum and Help

Innovationslabor – Hilfe bei Förderanträgen Dr. Pablo Berger – innolabor.de



help – Kaeltetechnik Forum www.kaelte-treffpunkt.de
user R8 aus Freiburg?
extremecooling (***) Praxis Tips, Löten, Befüllen …

yahoo group – organic_rankine_cycle
yahoo group – solar_concentrators

the old solar-concentrator from chichlid

Test und Pruefinstitut Karlsruhe

6. Rankine Systeme

7.1 Rankine Cycle


davinci-mode / Wankel engine


infinityturbine system
Build your own Brand 5-10 KW ORC
matteranenergy – new feedpump idea
MIT solar stginternational
klima-becker – Hinweis von Herrn Klemenz IHK-Freiburg

Mechanik – Klaus Bengel Tel. 640 371

7. Theory

organicrankine – many links related to scroll systems

ORC – Thermodynamics Theory – Sylvain Quoilin
PhD Rankine Cycle – Sylvain Quoilin
Design and Analysis of 1 KW Rankine Cycle with Multi Vane Expander


8. Funding


9. Useful Relation

Celsius in Fahrenheit = (( TCelsius × 9 ) / 5 ) + 32

1 bar = 10^5 N/m^2 = 10^5  pascal = 10^5 W sec/ m^3 = 1 kg/cm^2 = 14.5037738 psi (pounds per square inch)
1 W = 1 N m / sec = 10^-5 bar m^3 / sec

R_Air = 287.2 W sec/(kg K)
Cp_Air = 1010 W sec /(kg K)

n = Cv/Cp
n_Air = 1.4
n_R245fa = 1.13

1 inch ( zoll) = 2,54 cm

1/4 ” =  0,683 cm
3/8 ” = 0.95 cm






Filed under: exergia's projects,rankine engine — exergia posted 16/04/2012 at 6:32 pm

Thermodyna – Small sized Organic Rankine Cycle Heat Motor – 2. Expander

Something new from the blog  …

Here the first post regarding an old idea lying in the drawer for several years: Small sized Organic Rankine Cycle Heat Motor. Project name is Thermodyna. Step by step we will publish the latest results regarding 1. cycle configuration, 3. working fluid, 4. generator, … Today we start with the logical number 2, the expander.

2. Expander / Expansionsmaschine

The most important part in a Rankine cycle system is the expander, tbe unit converting the energy stored in the pressurized fluid into mechanical i.e. rotational energy. Off the shelf industrial parts driven by pressurized air are airmotors. Many different types are available:

2.1. Radial Piston Engine / Radialkolbenmotor

Radial engine in a cut-away view



Section Drawing

Type P1V-P, Parker Hannifin Catalog


2.1.1 Huco Dynatork

Type Dynatork 7, Huco Catalog


- Maximal input pressure: ~7 bar
- Maximal temprature: < 70 deg.
- Oil required: yes
- Operation time: ?
- Power, air consumption, speed: see below


2.1.2 Globe Airmotors


Type RM110 – Datasheet – Globe. Globe Catalog


- Maximal input pressure: ~8 bar
- Maximal temperature: <80 deg.
- Oil required: yes
- Operation time: 5000 – 8000h
- Power, air consumption, speed: see below
- Inside the housing there has to be a pressure of ~1 bar

2.1.3 Parker

Germany – Karrst


Type P1V-P SERIES – Datasheet – Parker, Parker Hannifin Catalog


- Maximal input pressure: ~7 bar
- Maximal temperature: < 70
- Oil required: yes
- Operation time: ?
- Power, air consumption, speed: see below


2.1.4 Tonson

2.2 Rotor Vane Motor / Lamellenmotor

Section Drawing

Parker Hannifin Catalog


2.2.1 Gast

Type:  NL – Non-Lubricated Air Motor, www.gastmfg.com
No lubrication necessary for these corrosion resistant air-motors.

Type: AM (SS) Series – Lubricated / Stainless Steel Air Motor, www.gastmfg.com
Fully sealed and sanitary design, these corrosion resistant

Type: AM – Lubricated Air Motors, Datasheet – Gast


2.2.2 Parker

Type: P1V-A SERIES – Datasheet – Parker, Parker Hannifin Catalog



- Maximal input pressure:
- Maximal temperature:
- Oil required:
- Operation time:
- Power, air consumption, speed: see below

2.2.3 Ober Italy


2.3 Gas Pressure Motor / Drehkolbenmotor

2.3.1 Armak

Type GGP04 – Datasheet – Armak, www.armakmotor.com


- Maximal input pressure: ~15 bar
- Maximal temperature: < 150 deg.
- Oil required: no
- Operation time: ?
- Power, air consumption, speed: see below



Manfacturers characterize their engines with diagramms showing the mechanical energy versus rotational speed and air consumption versus speed for different air intake pressures. Information about the engine’s efficiency are hard to find. As a first attempt to compare different engine’s efficiencies we suggest to calculate the normalized value  of specific power, the quotient of power  devided by air consumption ( [ ] = W / (l/sec) ) and plot it versus intake pressure. The results are shown below. The data values have been taken from the abowe cited data sheets. The plot also includes the maximum power that could be achived from pressurized air. As comparative process we use an isentropic expansion. The red curve shows power generated by filling the engine’s volume and the green power generated by expansion. The mathematical model is published here. We are in an ongoing process to discuss those results with some manufacturers.

Normalized Power per Inlet Air Consumption

Normalized Power per Exhaust Air Consumption (Free Air)



Filed under: air engine,airmotor,cogeneration,exergia's projects,rankine engine,thermodyna — exergia posted 11/03/2012 at 9:13 am

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