mdh.sePublications
Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
EVALUATING THE ORGANIC RANKINE CYCLE (ORC) FOR HEAT TO POWER: Feasibility and parameter identification of the ORC cycle at different working fluid with district waste heat as a main source.
Mälardalen University, School of Business, Society and Engineering, Future Energy Center.
2017 (English)Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
Abstract [en]

New technologies to converting heat into usable energy are constantly being developed for renewable use. This means that more interactions between different energy grid will be applied, such as utilizing low thermal waste heat to convert its energy to electricity. With high electricity price, such technology is quite attractive at applications that develop low waste heat. In the case of excess heat in district heating (DH) grid and the electricity price are high, the waste heat can be converted to electricity, which can bring a huge profit for DH companies. Candidate technologies are many and the focus in this degree rapport is on the so-called Organic Rankine Cycle (ORC) that belongs to the steam Rankine cycle. Instead of using water as a working fluid, organic working fluid is being used because of its ability to boil at lower temperature.

Because this technique is available, it also needs to be optimized, developed, etc. to achieve the highest appropriate efficiency. This can be done, for example, by modeling different layouts, analyzing functionality, performance and / or do a simulation of various suitable working fluids.  This is the purpose of this degree project and the research parts are to select working fluids suitable at low temperatures (70-120) °C, the difference analysis between the selected fluids and identification of the parameters that most affect the performance.

There are many suitable methods to apply to achieve desired results. The method used in this rapport degree is commercial software such as Mini REFPROP, CoolPack, Excel but the most important part is simulation with AspenPlus.

The selected and suitable working fluids between the chosen temperature interval are R236ea, R600, R245fa and n-hexane. Three common layouts were investigated, and they are The Basic ORC, ORC with an internal heat exchanger (IHE) and regenerative ORC. The results show that in comparison between 120°C and 70°C as a temperature source and without an internal heat exchanger (IHE), R600 at 70°C, has the highest efficiency about 13.55%. At 110°C n-hexane has the highest efficiency about 18.10%. R236ea has the lowest efficiency 13.16% at 70°C and 16.29% at 110°C. R236ea kept its low efficiency through all results. Without an IHE and a source range from 70 °C up to almost 90 °C, R600 has the highest efficiency and at 90°C n-hexane has the highest efficiency. With an IHE and between (70-90) °C R245fa still has the highest efficiency. With or without IHE and a heat source of 110 °C n-hexane has the highest efficiency 18.10% and 18.40%. R236ea gets the greatest increase 5.2% in efficiency but remains with the lowest efficiency. With Regenerative ORC, n-hexane had an optimal middle pressure about 0.76 bar. The optimal pressure corresponds to a thermal efficiency of 17.52%. The most important identified parameters are the fluid characteristics such as higher critical temperature, temperature source, heat sink, application placement and component performance.

 

 

 

 

The current simulations have been run at some fixed data input such as isentropic efficiencies, no pressure drops, adiabatic conditions etc. It was therefore expected that the same efficiency curve would repeat itself. This efficiency pattern would differ with less or higher values depending on the layout performance. However, this pattern was up to 90 degrees Celsius and gets a very noticeable change by the change of the efficiency for n-hexane. Therefore n-hexane is chosen with Regenerative ORC because it had the highest efficiency at the highest temperature source tested. This is due definitive to the fluid properties like its high critical temperature compared to the other selected fluids. R236ea remains the worst and that’s also related to the fluid properties. It is also important to note that these efficiencies are only from a thermodynamic perspective and may differ when combining both thermal and economic perspectives as well as application placement. These high efficiencies will certainly be lower at more advanced or real processes due to various factors that affect performance. Factors such as component´s efficiency and selection, pipe type and size, etc. To maintain a constant temperature when it’s not, flow regulation is then necessary and that’s also affects the performance.

 

The conclusion is that the basic ORC which does not have an IHE and from 70 up to 90 degrees Celsius, R600 has the highest efficiency. Higher temperature gives n-hexane the highest efficiency. With an IHE and between (70-90) °C R254fa has the highest efficiency. At higher temperature source n-hexane has the highest efficiency. ORC with an IHE has the best performance. The R236ea has the worst performance through all results. With regenerative ORC, an optimal meddle-pressure for n-hexane is 0.76 bar. Important parameters are The properties of the fluid, temperature source, heatsink, Application placement and component performance. 

Place, publisher, year, edition, pages
2017. , p. 61
Keywords [en]
Organic Rankine cycle, Recuporator, regenerative, heat-to power, working fluids, low temperature heat, power generation
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:mdh:diva-38573OAI: oai:DiVA.org:mdh-38573DiVA, id: diva2:1181644
Subject / course
Energy Engineering
Supervisors
Examiners
Projects
NejAvailable from: 2018-04-12 Created: 2018-02-09 Last updated: 2018-04-12Bibliographically approved

Open Access in DiVA

fulltext(17 kB)0 downloads
File information
File name FULLTEXT01.pngFile size 17 kBChecksum SHA-512
0c7978ce57bacbbdbf73a46d24b2b7d478d6bd1e72b8ce15e31ec1a0c54e3ec0a7216f11857a28ab3a82b7ff541b163b5dfe9d1bd8fe349630cdd1b9bafa42e5
Type fulltextMimetype image/png
fulltext(18 kB)0 downloads
File information
File name FULLTEXT02.pngFile size 18 kBChecksum SHA-512
7c0fdaca031600b84e8ea19dfc550a0ec940de72c1f64a784c4b49089cacd09c62d8b7ab05b7fa20a905cd77a814982474176783f225c20b5e874baffb677ee8
Type fulltextMimetype image/png
fulltext(18 kB)0 downloads
File information
File name FULLTEXT03.pngFile size 18 kBChecksum SHA-512
3c635464f77d42a450a889e86864baa4a4ca77115cf5de84d050823b915086a3279e9e2c6d06000d4bad190fa6bc1b6f3f55e0ae744ce68469d691f6d20be8a2
Type fulltextMimetype image/png
EVALUATING THE ORGANIC RANKINE CYCLE (ORC) FOR HEAT TO POWER(1781 kB)161 downloads
File information
File name DATASET01.pdfFile size 1781 kBChecksum SHA-512
621c4036ce689b48de5605f32f6a83589856cf2cd4a047646a4d605ed4de3efeed3aef1bff7228e1ce84d2aad2bc5babf5ee262757bdfab53d101f1a15781e7b
Type datasetMimetype application/pdf

By organisation
Future Energy Center
Engineering and Technology

Search outside of DiVA

GoogleGoogle Scholar
Total: 0 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

urn-nbn

Altmetric score

urn-nbn
Total: 50 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf