Astrain Ulibarrena, David

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Astrain Ulibarrena

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David

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Ingeniería

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ISC. Institute of Smart Cities

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Now showing 1 - 7 of 7
  • PublicationOpen Access
    Experimental evaluation of a transcritical CO2 refrigeration facility working with an internal heat exchanger and a thermoelectric subcooler: performance assessment and comparative
    (Elsevier, 2022) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Sánchez, Daniel; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    The use of carbon dioxide in transcritical state has become one of the most used solutions to comply with the F-Gas directive and reduce greenhouse gases emissions from refrigeration systems at high ambient temperatures. For low-medium power units, the commonly used solutions to improve the efficiency such as the ejector, multiple compressor arrangements, mechanical subcooler, etc., add complexity and increase the cost of the refrigeration facility, which is not ideal for small units. In this low-medium power range, two technologies stand out to increase the performance of a carbon dioxide transcritical cycle: the internal heat exchanger and the thermoelectric subcooler. This study brings a complete research in which both solutions have been tested in the same experimental transcritical carbon dioxide refrigeration facility under the same working conditions. It focuses on the real performance of both systems and discusses the strengths and weaknesses of using an internal heat exchanger or a thermoelectric subcooler. The results show that the thermoelectric subcooler outperforms the internal heat exchanger in both the coefficient of performance and the cooling capacity while also being a more controllable and flexible solution.
  • PublicationOpen Access
    Performance assessment of an experimental CO2 transcritical refrigeration plant working with a thermoelectric subcooler in combination with an internal heat exchanger
    (Elsevier, 2022) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Sánchez, Daniel; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería; Gobierno de Navarra / Nafarroako Gobernua; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    Regulations in the refrigeration sector are forcing the transition to low global warming potential fluids such as carbon dioxide in order to decrease direct greenhouse gases emissions. Several technologies have arisen over the past years to compensate the low performance of the transcritical carbon dioxide vapour compression cycle at high ambient temperatures. For low-medium power units, the inclusion of a thermoelectric subcooler or an internal heat exchanger have been proven as effective solutions for enhancing the coefficient of performance. However, the combination of a thermoelectric subcooler and an internal heat exchanger working simultaneously is yet to be explored theoretically or experimentally. This work presents, for the first time, an experimental transcritical carbon dioxide refrigeration facility that works simultaneously with a thermoelectric subcooler and with an internal heat exchanger in order to boost the cooling capacity and coefficient of performance of the refrigeration system. The experimental tests report improvements at optimum working conditions of 22.4 % in the coefficient of performance and an enhancement in the cooling capacity of 22.5 %. The 22.4 % increase in coefficient of performance would result in a decrease of energy consumption along a reduction of the greenhouse gases emissions. The proposed combination of a thermoelectric subcooler and an internal heat exchanger outperforms each of the technologies on their own and presents itself as a great controllable solution to boost the performance and reduce the greenhouse gasses emissions of transcritical carbon dioxide refrigeration cycles.
  • PublicationOpen Access
    Experimental assessment of a thermoelectric subcooler included in a transcritical CO2 refrigeration plant
    (Elsevier, 2021-05-25) Aranguren Garacochea, Patricia; Sánchez, Daniel; Casi Satrústegui, Álvaro; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC
    This study brings an experimental research that has tested a real transcritical CO2 vapor compression cycle that includes a thermoelectric subcooler at the exit of the gas-cooler of the refrigeration plant. The aforementioned technology hybridization increases the COP of refrigeration systems as long as the subcooling system is properly designed and operated. The experimental facility studied has been tested under constant ambient conditions (30 °C and relative humidity of 55%) and maintaining the evaporating temperature at -10 °C; while the voltage supplied to the thermoelectric modules and the thermal resistances of the heat exchangers located at the thermoelectric subcooler have been experimentally modified. The voltage supplied to the fans located at these heat exchangers was modified implying thermal performance deviation of the heat exchangers and a variation on the power consumption of the cooling facility. The results show an experimental increase on the COP of 11.3% while the cooling capacity increases a 15.3% when the thermoelectric modules are supplied with 2 V and the fans with 9 V. Moreover, the importance of optimizing the voltage supplied to the thermoelectric modules and to the auxiliary consumption of the thermoelectric subcooler is addressed along this research.
  • PublicationOpen Access
    Experimental enhancement of a CO2 transcritical refrigerating plant including thermoelectric subcooling
    (Elsevier, 2020) Sánchez, Daniel; Aranguren Garacochea, Patricia; Casi Satrústegui, Álvaro; Llopis, R.; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza
    CO2 is an excellent natural refrigerant that can be used in almost any commercial cooling application thanks to its useful range of evaporative temperatures and excellent environmental properties. However, due to its low critical temperature, CO2 has an important issue related to the low performance of the simplest transcritical refrigeration cycle. To overcome it, the subcooling technique is a well-known method to improve the energy performance of any refrigeration cycle especially the CO2 transcritical one. The IHX is a widely used example of this method that is implemented in almost all standalone systems that use CO2 as a refrigerant. As an alternative of this element, in this work, a thermoelectric subcooling system is presented and tested in a CO2 transcritical refrigerating plant. The experimental tests have been performed at two ambient temperatures: 25 and 30 degrees C, maintaining a constant evaporating level at-10 degrees C and varying the voltage supply to thermoelectric modules and the heat rejection pressure. The results from these experimental tests revealed that the COP and the cooling capacity of the refrigerating plant can be enhanced up to 9.9% and 16.0%, respectively, operating at the optimum operating conditions. Moreover, the experimental tests corroborate the existence of an optimum voltage which maximizes the COP, and the almost linear capacity regulation easily adjustable by varying the voltage supply.
  • PublicationOpen Access
    Effect of thermoelectric subcooling on COP and energy consumption of a propane heat pump
    (Elsevier, 2024-12-01) Aranguren Garacochea, Patricia; Sánchez, Daniel; Haida, Michal; Smolka, Jacek; Cabello, Ramón; Rodríguez García, Antonio; Astrain Ulibarrena, David; Ingeniería; Ingeniaritza; Institute of Smart Cities - ISC; Universidad Pública de Navarra / Nafarroako Unibertsitate Publikoa
    The building sector has an important impact on the environment, being responsible for 30 % of the total greenhouse gas emissions. Knowing that the energy consumption devoted to HVAC systems accounts for 50 % of the total energy consumption of buildings, it is paramount to develop environmentally friendly technologies able to provide green space heating to the building sector. To that purpose, this manuscript presents a computational study on propane vapor compression heat pumps which include thermoelectric subcooling to boost their operation. The combination of these technologies has been proven in the past to be very beneficial for refrigeration systems and this study concludes for the first time that propane heat pumps can highly benefit from thermoelectric subcooling. The widely conducted research includes the following parameters: ambient temperatures from -20 to 15 °C, voltage supplies to the thermoelectric modules from 0.5 to 10 VDC, number of thermoelectric subcooling blocks from 1 to 8 and two water inlet temperatures, 40 and 55 °C to study their influence on heating capacity, compressor and thermoelectric power consumptions, subcooling degree, propane mass flow, compressor capacity, COP, energy consumption and SCOP of the combined heat pump. The obtained results are very conclusive, COP enhancements up to 12.29 % are achieved when a thermoelectric subcooler with 16 modules is included in a propane heat pump already provided with an internal heat exchanger for an ambient temperature of -20 °C and a water inlet temperature of 55 °C. Additionally, improvements in Seasonal COP up to 9.98 % are achieved if the above-mentioned technologies integration between a vapor compression heat pump and a thermoelectric subcooler substitutes a conventional propane heat pump with an internal heat exchanger for space heating a single-story two-family house.
  • PublicationOpen Access
    Experimental validation and development of an advanced computational model of a transcritical carbon dioxide vapour compression cycle with a thermoelectric subcooling system
    (Elsevier, 2022) Casi Satrústegui, Álvaro; Aranguren Garacochea, Patricia; Sánchez, Daniel; Araiz Vega, Miguel; Cabello, Ramón; Astrain Ulibarrena, David; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
    The inclusion of a thermoelectric subcooler as an alternative to increment the performance of a vapour compression cycle has been proved promising when properly designed and operated for low-medium power units. In this work, a computational model that simulates the behaviour of a carbon dioxide transcritical vapour compression cycle in conjunction with a thermoelectric subcooler system is presented. The computational tool is coded in Matlab and uses Refprop V9.1 to calculate the properties of the refrigerant at each point of the refrigeration cycle. Working conditions, effect of the heat exchangers of the subcooling system, temperature dependent thermoelectric properties, thermal contact resistances and the four thermoelectric effects are taken into account to increment its accuracy. The model has been validated using experimental data to prove the reliability and accuracy of the results obtained and shows deviations between the ±7% for the most relevant outputs. Using the validated computational tool a 13.6 % COP improvement is predicted when optimizing the total number of thermoelectric modules of the subcooling system. The computational experimentally validated tool is properly fit to aid in the design and operation of thermoelectric subcooling systems, being able to predict the optimal configuration and operation settings for the whole refrigeration plant.
  • PublicationOpen Access
    Improvements in the cooling capacity and the COP of a transcritical CO 2 refrigeration plant operating with a thermoelectric subcooling system
    (Elsevier, 2019) Astrain Ulibarrena, David; Merino Vicente, Amaya; Catalán Ros, Leyre; Aranguren Garacochea, Patricia; Araiz Vega, Miguel; Sánchez, Daniel; Cabello, Ramón; Llopis, R.; Ingeniaritza; Institute of Smart Cities - ISC; Ingeniería
    Restrictive environmental regulations are driving the use of CO 2 as working fluid in commercial vapour compression plants due to its ultra-low global warming potential (GWP 100 = 1) and its natural condition. However, at high ambient temperatures transcritical operating conditions are commonly achieved causing low energy efficiencies in refrigeration facilities. To solve this issue, several improvements have been implemented, especially in large centralized plants where ejectors, parallel compressors or subcooler systems, among others, are frequently used. Despite their good results, these measures are not suitable for small-capacity systems due mainly to the cost and the complexity of the system. Accordingly, this work presents a new subcooling system equipped with thermoelectric modules (TESC), which thanks to its simplicity, low cost and easy control, results very suitable for medium and small capacity plants. The developed methodology finds the gas-cooler pressure and the electric voltage supplied to the TESC system that maximizes the overall COP of the plant taking into account the ambient temperature, the number of thermoelectric modules used and the thermal resistance of the heat exchangers included in the TESC. The obtained results reveal that, with 20 thermoelectric modules, an improvement of 20% in terms of COP and of 25.6% regarding the cooling capacity can be obtained compared to the base cycle of CO 2 of a small cooling plant refrigerated by air. Compared to a cycle that uses an internal heat exchanger IHX, the improvements reach 12.2% and 19.5% respectively.