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Implementation and evaluation of a low temperature waste heat recovery power cycle using NH 3 in an Organic Rankine Cycle
KTH, Skolan för industriell teknik och management (ITM), Energiteknik.
2012 (Engelska)Ingår i: Energy, ISSN 0360-5442, E-ISSN 1873-6785, Vol. 48, nr 1, s. 227-232Artikel i tidskrift (Refereegranskat) Published
Abstract [en]

With increasing cost for power generation opportunities for small scale power generation from waste heat have increased. The awareness of untapped resources such as local waste heat streams as well as the available range of technology and products to harvest such streams is increasing steadily though field data is scarce for applications below 100 °C entry temperature. ORC applications have a large number of open parameters and therefore require field data for correlation of models.This paper presents field data and analysis of an ORC power generation plant operating with NH 3. The unit operates on waste heat from a Swedish pulp mill at an available temperature of 75 to 85 °C. Performance at varying heat source conditions and capacity is reported as well as an analysis of the particular investment case.The data was generated during a 15 day period and show a thermal efficiency of 8-9% at capacities from 50 to 100%. The results indicate a flat thermal efficiency from 20 to 100% capacity.Investment case analysis is based on a purchase model while the chosen economic model is a supplier own-and-operate arrangement supplying the mill with power at a predefined cost during an extended period of time.

Ort, förlag, år, upplaga, sidor
2012. Vol. 48, nr 1, s. 227-232
Nyckelord [en]
FoC, Fraction of Carnot, Integrated local carnot efficiency, NH 3, ORC, Waste heat
Nationell ämneskategori
Energiteknik
Identifikatorer
URN: urn:nbn:se:kth:diva-110181DOI: 10.1016/j.energy.2012.02.074ISI: 000313461800027Scopus ID: 2-s2.0-84869881779OAI: oai:DiVA.org:kth-110181DiVA, id: diva2:586307
Anmärkning

QC 20130111

Tillgänglig från: 2013-01-11 Skapad: 2013-01-10 Senast uppdaterad: 2017-12-06Bibliografiskt granskad
Ingår i avhandling
1. Low temperature difference power systems and implications of multi-phase screw expanders in Organic Rankine Cycles
Öppna denna publikation i ny flik eller fönster >>Low temperature difference power systems and implications of multi-phase screw expanders in Organic Rankine Cycles
2016 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

New and old data on screw expanders operating with 2-phase mixtures in the admission line has been combined to enable the first public correlation of adiabatic expansion efficiency as a function of entry vapour fraction. Although not yet perfected, these findings have enabled an entirely new approach to the design and optimisation of Organic Rankine Cycles, ORCs. By allowing a continuous variation of vapour fraction at expander entry optima for thermal efficiency, second law efficiency and cost efficiency can be found. Consequently one can also find maxima for power output in the same dimension.

This research describes a means of adapting cycle characteristics to various heat sources by varying expander inlet conditions from pure liquid expansion, through mixed fluid and saturated gas expansion, to superheated gas. Thermodynamic analysis and comparison of the above optimisations were a challenge. As most terms of merit for power cycles have been developed for high temperature applications they are often simplified by assuming infinite heat sinks. In many cases they also require specific assumptions on e.g. pinch temperatures, saturation conditions, critical temperatures etc, making accurate systematic comparison between cycles difficult. As low temperature power cycles are more sensitive to the ‘finiteness’ of source and sink than those operating with high temperatures, a substantial need arises for an investigation on which term of merit to use.

Along with an investigation on terms of merit, the definition of high level reversible reference also needed revision. Second law efficiency, in the form of exergy efficiency, turned out to be impractical and of little use. A numerical approach, based on a combination of first and second law, was developed. A theory and method for the above is described. Eventually low temperature power cycle test data was compiled systematically. Despite differences in fluid, cycle, temperature levels and power levels the data correlated well enough to allow for a generalised, rough correlation on which thermal efficiency to expect as a function of utilization of source and sink availability. The correlation on thermal efficiency was used to create a graphical method to pre-estimate key economic factors for low temperature site potential in a very simple manner. A major consequence from the findings of this thesis is the reduced dependency on unique choices of process fluid to match heat source characteristics. This development significantly simplifies industrial standardisation, and thereby potentially improves cost efficiency of commercial ORC power generators.

Ort, förlag, år, upplaga, sidor
Stockholm: KTH Royal Institute of Technology, 2016. s. viii, 98
Serie
TRITA-REFR, ISSN 1102-0245 ; 15/02
Nationell ämneskategori
Energiteknik
Forskningsämne
Energiteknik
Identifikatorer
urn:nbn:se:kth:diva-188015 (URN)978-91-7595-872-9 (ISBN)
Disputation
2016-09-02, Hörsal M3, Brinellvägen 64, KTH Campus, Stockholm, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2016-06-09 Skapad: 2016-06-03 Senast uppdaterad: 2017-04-25Bibliografiskt granskad

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