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Evaluation and parametric modeling of 50 kW organic rankine cycle for waste heat recovery from rural Alaska diesel generator power plants.

机译：50 kW有机朗肯循环用于阿拉斯加农村柴油发电机组废热回收的评估和参数建模。

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摘要

In rural Alaska, there are about 180 villages that run independent electrical power systems using diesel generator sets. A diesel engine generator loses fuel energy in the form of waste heat through the charge air cooler (after cooler), the jacket water cooler, friction, and exhaust. Diesel engine jacket water and exhaust account for about 20% and 30% of the total fuel energy, respectively. In previous studies it has been demonstrated that about 80% of the heat present in jacket water and 50% of the heat from exhaust gases can be recovered for useful purposes such as heating, power generation, refrigeration, and desalination. In this study, the diesel engine waste heat application selected was power generation using an organic Rankine cycle (ORC) heat engine.;The basic principle of an ORC system is similar to that of the traditional steam Rankine cycle; the only difference is the working fluid. The working fluids generally used in an ORC are refrigerants, such as R11, R113, R123, R134a, R245fa, and HFE-7000. The working fluid in the ORC system under study is R245fa. A typical ORC consists of a pump, preheater, evaporator, expansion machine (expander), and condenser. The working fluid is pressurized through the pump and supplied to the preheater and evaporator, where it is heated by the heat source. The working fluid exits the evaporator as vapor or liquid/vapor. It expands in the expander, generating power. The low-pressure working fluid exiting the expansion machine is liquefied in the condenser by a cooling source, returned to the pump, and the cycle repeats.;At the University of Alaska Fairbanks (UAF) power plant, a lab experimental setup was designed: a hot water loop (heat source) and cold water loop (heat sink) for testing the 50 kW ORC power unit. Different diesel engine waste heat recovery conditions were simulated to study the unit's reliability and performance. After lab testing, the ORC system was installed permanently on a 2 MW Caterpillar diesel engine for jacket water heat recovery in Tok, Alaska, and tested further. These two tests provide for the goals of the present dissertation which are: (i) testing of a 50 kW ORC system for different heat source and heat sink supply conditions, (ii) develop guidelines on applying the present 50 kW ORC system for individual rural Alaska diesel gen-sets, (iii) develop empirical models for the screw expander, (iv) develop heat transfer correlations for single-phase and two-phase evaporation, and two-phase condensation for refrigerant R245fa in the preheater, evaporator and condenser, respectively, and (v) parametric modeling and validation of the present ORC system using the empirical correlations developed for a screw expander and R245fa in heat exchangers to predict the performance of the ORC system for individual diesel generator sets.;The lab experimental data were used to plot performance maps for the power unit. These maps were plotted with respect to hot water supply temperature for different ORC parameters, such as heat input to power unit in evaporator and preheater, heat rejection by power unit in condenser, operating power output, payback period, and emissions. An example of how performance maps can be used is included in this dissertation.;As detailed in this dissertation, the resulting lab experimental data were used to develop guidelines for independent diesel power plant personnel installing this ORC power unit. The factors influencing selection of a waste heat recovery application (heating or power) are also discussed. A procedure to find a match between the ORC system and any rural diesel generator set is presented. Based on annual electrical load information published in Power Cost Equalization data for individual villages, a list of villages where this ORC system could potentially be beneficial is included.;During lab work at the UAF power plant, experimental data were also collected on the refrigerant side (R245fa) of the ORC system. Inlet and outlet pressures and temperatures of each component (evaporator, pump, and expander) of the ORC were measured. Two empirical models to predict screw expander power output were developed. The first model was based on polytropic work output, and the second was based on isentropic work output. Both models predicted screw expander power output within +/-10% error limits.;Experimental data pertaining to the preheater, evaporator, and condenser were used to develop R245fa heat transfer correlations for single-phase and two-phase evaporation and two-phase condensation in respective heat exchangers. For this study the preheater, evaporator, and condenser were brazed plate heat exchangers (BPHEs). For single-phase heat transfer in the preheater, a Dittus-Boelter type of correlation was developed for R245fa and hot water. For R245fa evaporation in the evaporator, two heat transfer correlations were proposed based on two-phase equation formats given in the literature. For condensation of R245fa in the condenser, one heat transfer correlation was proposed based on a format given in the literature. All the proposed heat transfer correlations were observed to have good agreement with experimental data.;Finally, an ORC parametric model for predicting power unit performance (such as power output, heat input, and heat rejection) was developed using the screw expander model and proposed heat transfer correlations for R245fa in heat exchangers. The inputs for the parametric model are heating fluid supply conditions (flow rate and temperature) and cooling fluid supply conditions, generally the only information available in rural Alaska power plant locations. The developed ORC parametric model was validated using both lab experimental data and field installation data. Validation has shown that the ORC computation model is acceptable for predicting ORC performance for different individual diesel gen-sets.
机译：在阿拉斯加农村，大约有180个村庄使用柴油发电机组运行独立的电力系统。柴油发动机发电机通过增压空气冷却器（冷却器后），夹套水冷却器，摩擦和排气以废热的形式损失燃料能量。柴油机缸套中的水和废气分别占总燃料能量的20％和30％。在以前的研究中，已经证明，可以回收夹套水中大约80％的热量和废气中50％的热量，以用于有用的目的，例如加热，发电，制冷和脱盐。在这项研究中，选择的柴油机余热应用是使用有机朗肯循环（ORC）热机发电。ORC系统的基本原理与传统的蒸汽朗肯循环相似。唯一的区别是工作液。 ORC中通常使用的工作流体是制冷剂，例如R11，R113，R123，R134a，R245fa和HFE-7000。研究中的ORC系统中的工作流体为R245fa。典型的ORC由泵，预热器，蒸发器，膨胀机（膨胀机）和冷凝器组成。工作流体通过泵加压，并供应到预热器和蒸发器，在此由热源加热。工作流体以蒸气或液体/蒸气的形式离开蒸发器。它在扩展器中扩展，从而产生能量。离开膨胀机的低压工作流体通过冷却源在冷凝器中液化，返回泵，然后重复循环。在阿拉斯加费尔班克斯大学（UAF）电厂，设计了实验室实验装置：一个热水回路（热源）和冷水回路（散热器）来测试50 kW ORC功率单元。模拟了不同的柴油机余热回收条件，以研究该机组的可靠性和性能。经过实验室测试，ORC系统永久安装在2 MW卡特彼勒柴油发动机上，用于阿拉斯加Tok的夹套水热回收，并进行了进一步测试。这两项测试提供了本论文的目标：（i）针对不同的热源和散热器供应条件测试50 kW ORC系统，（ii）制定针对个别农村地区应用当前50 kW ORC系统的准则阿拉斯加柴油发电机组，（iii）为螺杆膨胀机建立经验模型，（iv）为预热器，蒸发器和冷凝器中的制冷剂R245fa开发单相和两相蒸发的传热相关性，以及两相冷凝， （v）使用为螺杆膨胀机和热交换器中的R245fa开发的经验相关性对本ORC系统进行参数建模和验证，以预测各个柴油发电机组的ORC系统的性能。绘制功率单元的性能图。这些图是针对不同ORC参数的热水温度绘制的，例如蒸发器和预热器中功率单元的热量输入，冷凝器中功率单元的热量排放，工作功率输出，投资回收期和排放量。本论文包括一个如何使用性能图的例子。如本论文所详述，所得的实验室实验数据被用于为安装该ORC动力装置的独立柴油发电厂人员制定指南。还讨论了影响余热回收应用选择的因素（供暖或发电）。提出了在ORC系统和任何农村柴油发电机组之间找到匹配项的过程。根据发布在各个村庄的``电力成本均等''数据中的年度电力负荷信息，列出了该ORC系统可能有益的村庄清单。;在UAF电厂的实验室工作期间，还收集了制冷剂侧的实验数据（R245fa）的ORC系统。测量了ORC的每个组件（蒸发器，泵和膨胀器）的入口和出口压力以及温度。开发了两个经验模型来预测螺杆膨胀机的功率输出。第一个模型基于多方功输出，第二个模型基于等熵功输出。两种模型均预测螺杆膨胀机的功率输出误差在+/- 10％的误差范围内。;与预热器，蒸发器和冷凝器有关的实验数据被用于开发R245fa单相，两相蒸发和两相冷凝的传热相关性在各个热交换器中。在本研究中，预热器，蒸发器和冷凝器为钎焊板式换热器（BPHE）。对于预热器中的单相传热，针对R245fa和热水开发了Dittus-Boelter类型的关联式。对于R245fa在蒸发器中的蒸发，基于文献中给出的两相方程格式，提出了两种传热相关性。对于R245fa在冷凝器中的冷凝，基于文献中给出的格式提出了一种传热相关性。观察到的所有传热相关性均与实验数据具有良好的一致性。最后，使用螺杆膨胀机模型开发了预测功率单元性能（例如功率输出，热量输入和散热）的ORC参数模型，并提出了R245fa在热交换器中的传热相关性。参数模型的输入是加热流体的供应条件（流速和温度）和冷却流体的供应条件，通常是阿拉斯加农村发电厂所在地唯一可用的信息。使用实验室实验数据和现场安装数据对开发的ORC参数模型进行了验证。验证表明，ORC计算模型可用于预测不同柴油发电机组的ORC性能。

著录项

  • 作者

    Avadhanula, Vamshi Krishna.;

  • 作者单位

    University of Alaska Fairbanks.;

  • 授予单位 University of Alaska Fairbanks.;
  • 学科 Mechanical engineering.
  • 学位 Ph.D.
  • 年度 2015
  • 页码 224 p.
  • 总页数 224
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类
  • 关键词

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