Organic Rankine cycles represent today one of the most studied technologies aimed to boost electric efficiency of prime movers and to exploit renewable sources like biomass, solar and geothermal. Several ORC plants are already available on the market, especially in the medium range of power (0.1 – 5 MWe), normally equipped with a centrifugal feed pump. Smaller cycles (e.g. for residential applications, with a rated power of few kWe) are not so diffused, since several problems have to be overcome to reach technical effectiveness and economical feasibility. One of the most critical components, other than the expander, is the pump: in fact, since refrigerants like R245fa seem to be among the best suitable fluids for domestic applications, the feed pump has to work with a very low viscosity liquid, able to leak across the seals on the shaft. Several prototypes today are equipped with diaphragm pumps, which ensure a perfect insulation towards ambient, but, on the other side, are quite expensive and are affected by a relatively low efficiency. The aim of this work is the experimental study of a gear pump originally designed to handle light oils, in order to evaluate its suitability for an ORC system. A test bench has been designed and built, and the pump has been equipped with a magnetic coupling to its motor, to avoid the liquid leakage. The main performances of the pump working with R245fa have been investigated and compared with the ones of the same pump operating with light oil. Finally, some considerations on the suitability of the gear pump for a small scale organic Rankine cycle have been carried out, focusing on the main advantages and drawbacks of its utilization.
Experimental tests on a gear pump for organic Rankine cycle applications
CLEMENTE, STEFANO;MICHELI, DIEGO;RADU, ROBERT;
2013-01-01
Abstract
Organic Rankine cycles represent today one of the most studied technologies aimed to boost electric efficiency of prime movers and to exploit renewable sources like biomass, solar and geothermal. Several ORC plants are already available on the market, especially in the medium range of power (0.1 – 5 MWe), normally equipped with a centrifugal feed pump. Smaller cycles (e.g. for residential applications, with a rated power of few kWe) are not so diffused, since several problems have to be overcome to reach technical effectiveness and economical feasibility. One of the most critical components, other than the expander, is the pump: in fact, since refrigerants like R245fa seem to be among the best suitable fluids for domestic applications, the feed pump has to work with a very low viscosity liquid, able to leak across the seals on the shaft. Several prototypes today are equipped with diaphragm pumps, which ensure a perfect insulation towards ambient, but, on the other side, are quite expensive and are affected by a relatively low efficiency. The aim of this work is the experimental study of a gear pump originally designed to handle light oils, in order to evaluate its suitability for an ORC system. A test bench has been designed and built, and the pump has been equipped with a magnetic coupling to its motor, to avoid the liquid leakage. The main performances of the pump working with R245fa have been investigated and compared with the ones of the same pump operating with light oil. Finally, some considerations on the suitability of the gear pump for a small scale organic Rankine cycle have been carried out, focusing on the main advantages and drawbacks of its utilization.Pubblicazioni consigliate
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