Papers by Keyword: PTC

Abstract: The paper presents a study of a thermal assessment of an Organic Rankine Cycle (ORC) energized by heat absorbed from a parabolic trough collector (PTC) located in Derna, Libya. Both the ORC and PTC are modeled using the IPSEpro software. The simulation results are used to evaluate the system performance using energy and exergy analysis. The study showed the PTC collector was the main contributor of the energy and exergy losses within the PTC system and the evaporator within in the ORC. At this specific weather conditions, the ORC was able to produce about 3 MW electrical powers from the powered PTC heat. Moreover, exergy efficiency of the PTC was 47.7 %, the heat engine was 23.3 % and for the overall system (PTC and ORC) was 11.1 %.

Abstract: This article explains a technique in which equations are developed to produce the irradiance profile around the receiver of LS2 collector using a vigorouslyverified MCRT model. A large range of test conditions including daily normal insolation, selective coatings and glass envelop conditions were chosen from the published data by Dudley et al. [1] for the job. The R² value is excellent that varies between 0.9857 and 0.9999. Therefore, these equations can be used confidently to produce boundary heat flux profile of the collector at normal incident for conjugate heat transfer analyses of the receiver.

Abstract: The microstructure, especially porosity, of PTC (positive temperature coefficient) thermistor based on BaTiO₃ was controlled with a forming pressure. The relationship between theirPTCR properties and microstructureswas investigated with an optical and SEM (Scanning Electron Microscope) images and digital multimeter. Disk samples were fabricated by pressinguniaxially at various pressures of 100~15000kg/cm² and sintering at 1265°C in reducing atmosphere and finally re-oxidizing at 700°C in air. The porosity of the samples decreased rapidly from 45% to 8% with increasing the forming pressure from 100 to 1000kg/cm²andbecame 4% at 15000kg/cm²with slowdecreasing of porosity in the pressure range of 1000~15000kg/cm².With increasing the forming pressure, the resistivity jump of samplesdecreased rapidlyfrom 0.5 to 2.9 at about1000kg/cm²that corresponds tothe porosity of 15% and was saturated above this pressure. It is considered that there is a critical amount of porosity for having PTCR effect, which was about 15% in our samples. In addition, the porosity of the sample has a greater influence on the resistivity jump than on theresistivity at room temperature, which is due to the oxidation of grain boundary through a favorable channel of oxygen such as a pore.

Abstract: This paper gives a way which utilizes the PTC (positive temperature coefficient) materials to preheat diesel in the injector in order to improve the cold start performance and emissions of engine. Combining high performance data acquisition system based on MSP430F149, a dynamic temperature testing system was developed to test fuel temperature heated by PTC in injector. The software and hardware electrocircuit were expounded in detail. The temperature varying law of diesel fuel heated with PTC ceramics was measured under different voltage. A conclusion can be draw that diesel fuel may be heated to self-defined temperature around Curie point when diesel fuel was heated with PTC material.

Abstract: Polymeric Positive Temperature Coefficient (PTC) materials or Conducive Polymer Composites (CPC) display a certain characteristic of change in conductivity with temperature, which is unique to this kind of materials and is not found in any other electrical conductor. This paper recognizes the problem of formation of hotpots in low voltage switchboards and an economical and effective method to prevent this undesirable situation by the use of CPC’s. The tests done on samples and the obtained results bolster the proposition of using these materials as suitable temperature detection devices. A conceptual design of such a device was developed using Pro/E and is described in this paper. Current and future progress regarding the industrial potential of this device is also mentioned.

Abstract: This research focus on two PTC designs, one in Runzhen-school, China (latitude 36.5°N, longitude110°E and 386m altitude) and the second PTC with tracking system. The study showed that, using one tube concentrate in the focal point with fixed PTC gives lower efficiency compared with using two vacuum tubes, as the variation of solar altitude angle is large. So using two focal points results a better heating. The new system uses PTC with sun tracking system to maximize solar radiation absorptions, that leading to increase the hot water temperature and has higher system efficiency. In addition, this system supplies two batteries by electricity coming from two solar-cells and it’s produced for the tracking system working during hours of sunlight. The photovoltaic electricity provided is stored in batteries and then used for tracking motion. The tracing motion receives orders from a control unit, which works at different voltage in two solar cells.

Abstract: Composite particles with ultra-high molecular polyethylene (UHMWPE) core and carbon nanotube (CNT) shell were produced by an impact coating process, and molded into conductive polymer composites. Morphology of these composite particles was observed and the electrical behavior of these molded composites was measured. UHMWPE particles were very well coated by CNT, and conductive networks of CNT were formed after molding. These conductive polymer composites with low loadings of conductive filler exhibit lower room-temperature resistivity, and volume resistivity decreases with temperature on the whole. This is because of the CNT distribution is uniform in a macroscopic view but is oriented in a mesoscopic view. Thermionic emission of CNT is strong in polymer composites produced by this process. A related mechanism is discussed.

Abstract: As a lead-free positive temperature coefficient of resistivity (PTCR) material, [Ba_0.95-x (K_0.5Bi_0.5)_0.05Ca_x]_1-yNb_yO₃ system was prepared by the conventional solid-state reaction method. All samples sintered in air at 1300°C possess PTC characteristics as well as semi-conductivity characteristics, especially they show high Tc(130°C~160°C) value and the jump of the resistivity (maximum resistivity ρ_max / minimum resistivity ρ_min ) is four orders of magnitude. Samples with the composition of 0.3mol% Nb₅₊ have low room-temperature resistivity (ρ25°C) of ~10³Ω.cm.

Abstract: Computer Supported Collaborative Design(CSCD) is the applicarion of Computer Supported Collaborative Work(CSCW) in the product design field. Based on the analyse of the key technologies and problems of CSCD, a CSCD design frame faced to product design is established. Then a CSCD system faced to radar key components is founded with Pro/INTRALINK software and re-exploiting technology. Some key processes are designed too, such as database management, workflow programming, information communication, file release, conflict identification and safety management. These will provide a reference for constructing a cooperative design environment.

Abstract: A multi-components multi-layer co-fired ceramic varactor with superior performance is here presented. The concept combines a tunable capacitor with optimized properties in a restricted temperature range with PTCR layers to control the overall device temperature. Different prototypes are produced as demonstrator units; one of them is described in detail. The device may be tuned by a primary bias voltage applied to the capacitor and by a secondary voltage applied to the PTCR to set the working temperature. By proper choice of materials, bias voltage and working temperature, the varactor is optimized to the requested figure of merit for a specific application. The prototype here described has shown a tunability >83% @ 2.75 V//m (Patent Pending)