17 research outputs found
Study of cyclic thermal aging of tube type receivers as a function of the duration of the cycle
No full textPublisher Copyright: © 2017 Author(s).The tube type receivers are exposed to variable duration cyclic operating conditions, which can jeopardize its reliability, and make it hard to estimate its long term performance. The designers have to deal with this problem and estimate the receiver long term performance based on the poor available litterature and the data sheets of the material. In order to help the designer better estimate the performance of the receivers, in this paper the cyclic thermal aging is analyzed as a function of the cycle duration. For this purpose, coated and uncoated Inconel alloy 625 tubular samples, similar to those used in the commercial receivers, are cyclically aged with different thermal cycle duration. The aging of these samples has been analyzed by means of oxidation kinetics, microstructure examination and mechanical and optical properties. The effect of the thermal cycle duration is studied and discussed by comparison of the results.Peer reviewe
Solar aging of receivers made of nickel super alloys
No full textPublisher Copyright: © 2018 Author(s).Long term aging of solar receivers is studied by means of its microstructure stability and mechanical properties evolution. The results show that solar aging modify the microstructure and mechanical behaviour of used materials.Peer reviewe
Analysis of a failure mechanism in parabolic troughs receivers due to bellows cap overirradiation
No full textPublisher Copyright: © 2020 Elsevier LtdDuring the last years the number of broken tube receivers in parabolic-trough solar collectors was higher than expected in several commercial solar power plants and the failure events increased specially in winter. An exhaustive on field inspection of the broken glass envelopes and expansion bellows of the receivers (heat collecting elements) suggests that this unusual number of damaged receiver tubes is somewhere related with the over-irradiation of the bellows caps in some operation conditions. In this work the failure mechanism and the operation conditions that make it possible are analyzed. The analysis of this failure mechanism have allowed to identify the seasonality of the phenomenon and to design an appropriate strategy to reduce or even to prevent the failure due to the over irradiation of the bellows caps of solar receiver tubes.Peer reviewe
Methodology for partial vacuum pressure and heat losses analysis of parabolic troughs receivers by infrared radiometry
No full textPublisher Copyright: © 2019 Elsevier B.V.Loss of vacuum due to incoming gases (hydrogen or air) in evacuated receiver tubes of parabolic-through solar collectors (PTC) is one of the most common failures in large solar power plants and it has a significant impact on the thermal performance of the solar field. The loss of vacuum is translated in increasing heat losses and at certain point, damaged receivers must be replaced, but first they must be identified among all receiver pipes installed in a large solar field, which counts thousands units. Several efforts have been done to develop a methodology to locate receivers which loss completely the vacuum. These methodologies are based on the glass envelope temperature, the so called surface temperature method. In this work, the surface temperature method has been extended to determine partial vacuum pressure of receiver tubes not completely damaged and to determine its influence in their thermal performance. Results obtained using air as the incoming gas demonstrate that the methodology presented allows distinguishing partial vacuum pressure among 10−4, 10−2, 100, 102, 103 mbar in the receiver cover annulus but it does require accurate measurements that must be carefully addressed as described in this work. Further tests with this methodology may be also applied to determine the partial vacuum pressure of hydrogen in the annulus of this type of solar receivers.The research leading to these results received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under Grant Agreement no. 609837 (Scientific and Technological Alliance for Guaranteeing the European Excellence in Concentrating Solar Thermal Energy, STAGE-STE) and from the European Union H2020 Programme under Grant Agreement no. 823802 (Solar Facilities for the European Research Area – Third Phase, SFERA-III).Peer reviewe
Spatial distribution of microstructure of solar receivers exposed to high solar fluxes
No full textPublisher Copyright: © 2018 Author(s).The tube type receivers of point focus systems are exposed to complex radiation and temperature distributions. In these conditions, long term aging can modify the material microstructure and also its spatial distribution around and along the tube as a consequence of the temperature gradients. In this work the microstructure spatial distribution of a receiver tube that has been in operation for more than 1000 hours is studied. The bulk microstructure examination along the tube and in the circumferential direction has revealed a complex precipitates distribution. These precipitates can modify the mechanical properties of the alloy. Therefore, it can seriously affect to the receivers reliability, and must be consider during the design phase. Moreover radiation seems to enhance the oxidation rate which can seriously affect the durability of the receiver.Peer reviewe
Forty Shades of Black: a Benchmark of High Temperature Sprayable Black Coatings Applied on Haynes 230
No full textThe solar receiver coating opto-thermal efficiency has a significant impact on a central receiver system thermal
final system efficiency. The development of durable high solar absorptance coatings with simple application process and minimal thermal treatment can directly improve the receiver efficiency, thus reducing the levelized cost of electricity. During the past years, innovative receiver coatings for solar thermal tower plants have been developed on various substrates and tested under isothermal load at different temperature levels. In this paper, eight commercial black coating formulations are sprayed on Haynes 230 metal coupons. Solar absorptance and thermal emittance are monitored before and after isothermal exposure. Mass deviations are also measured to pinpoint any oxidation or coating outgassing. Isothermal testing is performed in laboratory muffle furnace for 1000 hours, covering the operating temperature range
from 700 to 800 °C. After 1000 hours exposure at 800 °C, Pyromark 2500 leads the benchmark, while many black
coatings degrade optically. Uncoated samples oxidize significantly and appear darker than some aged black coatings
Experimental system for long term aging of highly irradiated tube type receivers
No full textTube type receivers are being designed with codes that underestimate the thermo-mechanical fatigue and do not consider the effect of ultraviolet radiation. The effect of those phenomena in the receiver durability must be estimated from long-term aging tests, which are best carried out in a solar concentration facility. For this purpose, a solar dish, which was initially coupled to a Stirling engine, has been transformed into a test laboratory capable of reproducing the severe solar radiation concentration and temperature conditions typical of solar central tower receivers. In this facility, the temperature and the solar radiation density are controlled as independent variables. On one hand, the solar radiation density can be adapted to the test required level moving the sample along the dish optical axis. On the other hand, the temperature is controlled by an air flow, which is used as the heat transfer fluid. A test bed, including all the required elements for controlling the temperature and the solar radiation density, has been built up to satisfy certain solar irradiance and temperature ranges. So far, the solar dish has shown to be a very versatile facility for testing materials aging under high solar radiation densities.Peer reviewe
Adaptive and Interactive Architecture
No full textabstract: I devote my thesis to the practice of adaptive architecture and parametric design. The interactive and adaptive design would be my interest and my research thesis will be the process of exploring the architectural potentials of computer-programmed architectural design which interact with human beings. Start with the adaptive architectural theory of Neil Leach and Sou Fujimoto's architectural theory of architecture type, I explore and test the possibilities with current tools. I did reseach on the current study and practice of adaptive and interactive architecture in 20 century. After a series of study and experiment, I decided to make the "mirror" as a portal of inside and outside a building indicating a vague spacial relationship instead of just a normal mechanic mirror. The "mirror" will able to translate the information captured from motion to another "language" presented by movable materials to surrounding people, which provides people space to reflect and interact with each other. And the device would be the prototype of my thesis. The exploration of technology in the field of architecture really attracts me. I enjoy the design process and the final product. I will pay attention to new technologies in the future and try to combine technology, art and architecture together to create new experience
Design and experimental characterization of a propane-based reversible dual source/sink heat pump
No full textPublisher Copyright: © 2024 The Author(s)The current paper presents the design and energy performance analysis of a propane-based reversible Dual Source/Sink Heat Pump (DSHP). DSHPs offer an alternative to conventional water to water and air to water heat pumps, leveraging the strengths of both technologies in an efficient manner. The developed prototype incorporates an innovative Dual Source/Sink Heat eXchanger (DSHX), enabling the unit operating in various modes, including space heating, space cooling, and domestic hot water production using brine, air or both simultaneously as a source/sink. The DSHX serves as as both a condenser or an evaporator, directly rejecting or absorbing heat from air and/or brine. By eliminating secondary loops and defrost cycles, the DSHX minimizes energy losses. The main novelty of this work lies in the DSHX that integrates external units typically duplicated in DSHPs into a single component, eliminating the need for split refrigerant flow rates, thus avoiding maldistribution, refrigerant charge increase and draining valves. A steady state experimental campaign was conducted in a climatic chamber to characterize the DSHP prototype and validate the DSHX performance models. Heating capacity up to 11.2 kW and COP values up to 4.7 were achieved at nominal compressor speed by supplying hot water at 35 °C with an ambient temperature of 7 °C. Similarly, when producing cold water at 7 °C, cooling capacity and EER reached 9.8 kW and 3.6, respectively, at nominal compressor speed using air as heat sink at 35 °C. The effects of various operating parameters on the overall coefficient of performance and heat duty in both heating and cooling modes, considering air or brine as heat source/sink are analyzed in detail. Results demonstrate enhancements of approximately 15 % in capacity and efficiency compared to earlier work. Moreover, four deterministic models were created in order to predict the behaviour of the DSHX and validated against experimental results, reaching deviation values below 15 %.Peer reviewe
Forty shades of black: A benchmark of high temperature sprayable black coatings applied on Haynes 230
No full textThe solar receiver coating opto-thermal efficiency has a significant impact on a central receiver system thermal final system efficiency. The development of durable high solar absorptance coatings with simple application process and minimal thermal treatment can directly improve the receiver efficiency, thus reducing the levelized cost of electricity. During the past years, innovative receiver coatings for solar thermal tower plants have been developed on various substrates and tested under isothermal load at different temperature levels. In this paper, eight commercial black coating formulations are sprayed on Haynes 230 metal coupons. Solar absorptance and thermal emittance are monitored before and after isothermal exposure. Mass deviations are also measured to pinpoint any oxidation or coating outgassing. Isothermal testing is performed at 700, 750 and 800 °C in a muffle furnace for 1000 hours. After 1000 hours isothermal exposure, Coterill 750 leads the benchmark in front of Pyromark 2500, while other black coatings degrade optically. Uncoated samples oxidize significantly and appear darker than some aged black coatings
