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现行 ASTM E905-87(2021)
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Standard Test Method for Determining Thermal Performance of Tracking Concentrating Solar Collectors 用于确定跟踪集中太阳能集热器的热性能的标准测试方法
发布日期: 2021-01-01
1.1 本试验方法包括测定用于加热热系统中流体的跟踪聚光太阳能集热器的热性能。 1.2 本试验方法适用于单轴或双轴跟踪反射浓缩收集器,其中流体通过单个入口进入收集器,并通过单个出口离开收集器,以及可以有效提供单个入口和出口的收集器,例如进入多个收集器模块的平行入口和出口。 1.3 本试验方法适用于设计为漫辐照度对性能的影响可以忽略不计,并且其性能可以用直接辐照度来表征的集热器。 注1: 为了澄清起见,该方法应适用于几何浓度比为7或更大的收集器。 1.4 集热器可以作为热收集子系统进行测试,其中跟踪误差的影响已从热性能中基本消除,或者作为具有制造商提供的跟踪机制的系统进行测试。 1.4.1 测试如下: 部分 线性单轴跟踪收集器测试为 热收集子系统 11–13 线性单轴跟踪采集器的系统测试 14–16 线性双轴跟踪和点焦点收集器 作为热收集子系统进行测试 17–19 点焦点和线性双轴的系统测试 跟踪收集器 20–22 1.5 本试验方法不适用于且可能不适用于相变或热虹吸管收集器、在发生相变的操作条件下的任何收集器、固定镜像跟踪接收器收集器或中央接收器。 1.6 本试验方法仅适用于晴空准稳态条件下的室外试验。 1.7 采集器的选择和准备(采样方法、预处理、安装、校准等)、效率的计算以及通过使用本标准进行评级而产生的数据的处理超出了本试验方法的范围,预计将在其他地方涵盖。 1.8 本试验方法不提供确定任何收集器或组件的耐久性或可靠性的方法。 1.9 以国际单位制表示的数值应视为标准值。国际单位制后括号中给出的值仅供参考,不被视为标准值。 1.10 本标准并非旨在解决与其使用相关的所有安全问题(如有)。 本标准的用户有责任在使用前制定适当的安全、健康和环境实践,并确定监管限制的适用性。 1.11 本国际标准是根据世界贸易组织技术性贸易壁垒(TBT)委员会发布的《关于制定国际标准、指南和建议的原则的决定》中确立的国际公认标准化原则制定的。 ====意义和用途====== 5.1 本测试方法旨在提供预测特定位置特定系统应用中收集器热性能所需的测试数据。除采集器测试数据外,此类预测还需要验证采集器和系统性能仿真模型,而该测试方法未提供这些模型。 因此,本试验方法的结果本身并不构成受试收集器的额定值。此外,本试验方法的目的不是为了进行比较而确定收集器效率,因为应为特定应用确定效率。 5.2 本试验方法将集热器热性能与直接太阳辐照度联系起来,如使用角视场在5到6°之间的太阳热量计测量的那样。现有太阳辐射数据的优势是通过这种类型的仪器收集的,因此直接适用于预测收集器和系统性能。 5.3 本试验方法提供了实验程序和计算程序,以确定太阳能集热器的以下晴空准稳态值: 5.3. 1. 响应时间, 5.3.2 入射角修改器, 5.3.3 近正入射角范围,以及 5.3.4 近垂直入射角下的热增益率。 注4: 并非所有这些值都是为所有收集器确定的。 表1 概述了每种收集器类型和跟踪布置所需的测试。 × = 必修的。 ⊗ = 由于接收器支撑结构上的高水平太阳辐照度可能会对设备造成潜在损坏,并随后对人员造成损害,因此必须遵守安全预防措施和技术预防措施,但这种方法可能不适用于点聚焦收集器。 ** = 可选测试,可提供有关制造商跟踪设备精度对热性能影响的有用信息。 5.4 该试验方法可用于评估任何一种材料的热性能( 1. )完整系统,包括跟踪子系统和热收集子系统,或( 2. )热收集子系统。 5.4.1 当使用该测试方法评估整个系统时,应使用制造商的跟踪器和相关控制装置进行测试,因此跟踪误差对热性能的影响将包含在结果中。线性单轴跟踪系统可以补充测试实验室的跟踪设备,以实现双轴跟踪安排。 5.4.2 在评估热收集子系统时,应根据 10.3 . 5.5 该试验方法应在一个适当的流速下完成。对于设计为在可变流量下运行以实现受控出口温度的收集器,收集器性能应通过在多个流量下重复本试验方法来表征。 这些流量应为收集器实际操作条件的典型值。 5.6 确定响应时间是为了确定在每次热性能测试之前存在准稳态条件所需的时间,以确保有效的测试数据,并确定平均准稳态性能的时间长度。响应时间由瞬态温度数据计算得出,瞬态温度数据由给定流速下拦截太阳辐照度的阶跃变化产生。建立初始准稳态条件,然后突然增加或减少辐照度水平,并建立最终准稳态条件。对于本试验方法涵盖的大多数收集器,两个程序中每一个程序确定的响应时间的差异在实际时间方面将很小。 人们认识到,对于一些收集器,特别是那些具有长流体停留时间的收集器,两个响应时间值的差异可能很大。然而,未发现差异会影响试验方法的其余部分。 5.7 测量线性单轴跟踪采集器的入射角修饰符,以便根据本试验方法中要求的在近垂直入射下测量的热性能,可以预测任意入射角下的热性能。这是必要的,因为在实际的日常操作中,线性单轴跟踪采集器通常只垂直于太阳一次或两次。 5.7.1 在非零入射角下,线性单轴跟踪收集器的热性能可能会因以下几个原因而改变: 5.7.1.1 集中器和接收器表面的反射率、透射率和吸收率增加或减少,或 5.7.1.2 接收器对反射或折射太阳能的拦截增加或减少。 5.7.1.3 由于吸收器末端收集的能量损失而导致的拦截减少部分可以从收集器几何形状作为末端效应因子进行分析计算(见 附录X1 ). 5.7.2 确定入射角调节剂的首选程序通过要求工作传热流体与试验方法其余部分中使用的相同,并将其保持在近似等于环境温度的入口温度,将接收器的热损失降至最低。然而,人们意识到,由于一些导热油在接近环境温度时变得太粘稠,无法通过流体测试回路泵送,或者流体测试回路无法实际地充分冷却工作流体,以接近通常在寒冷气候下冬季出现的环境温度,因此,按照规定执行该程序可能不实际。 在这些情况下,制造商或供应商可自行决定使用替代程序A或B。替代程序A使用水作为工作流体,入口温度约等于环境温度,以尽量减少热损失,但该程序需要仔细清洁收集器流体通道,可能需要使用单独的流体测试回路,如果收集器流体通道与水不兼容,则可能会导致腐蚀。替代程序B使用与试验方法其余部分相同的传热流体,但温度升高,尽可能接近环境温度。替代程序B涉及接收器更高的热损失,必须对此进行计算和校正。在替代程序B中,通过确定相同流体入口温度下的未辐照热损失,获得了这些热损失的近似修正。 5.8 需要确定近正入射的角度范围,以确定测试条件,在该条件下,测量的热性能将充分代表真实正入射下的热性能。 注5: 近正入射角范围的测量还提供了可用于评估跟踪精度热性能灵敏度的数据。 5.9 太阳能集热器的热性能是在晴空条件下和接近正常入射的情况下确定的,因为这些条件是可重复的,并导致相对稳定的性能。
1.1 This test method covers the determination of thermal performance of tracking concentrating solar collectors that heat fluids for use in thermal systems. 1.2 This test method applies to one- or two-axis tracking reflecting concentrating collectors in which the fluid enters the collector through a single inlet and leaves the collector through a single outlet, and to those collectors where a single inlet and outlet can be effectively provided, such as into parallel inlets and outlets of multiple collector modules. 1.3 This test method is intended for those collectors whose design is such that the effects of diffuse irradiance on performance is negligible and whose performance can be characterized in terms of direct irradiance. Note 1: For purposes of clarification, this method shall apply to collectors with a geometric concentration ratio of seven or greater. 1.4 The collector may be tested either as a thermal collection subsystem where the effects of tracking errors have been essentially removed from the thermal performance, or as a system with the manufacturer-supplied tracking mechanism. 1.4.1 The tests appear as follows: Section Linear Single-Axis Tracking Collectors Tested as Thermal Collection Subsystems 11–13 System Testing of Linear Single-Axis Tracking Collectors 14–16 Linear Two-Axis Tracking and Point Focus Collectors Tested as Thermal Collection Subsystems 17–19 System Testing of Point Focus and Linear Two-Axis Tracking Collectors 20–22 1.5 This test method is not intended for and may not be applicable to phase-change or thermosyphon collectors, to any collector under operating conditions where phase-change occurs, to fixed mirror-tracking receiver collectors, or to central receivers. 1.6 This test method is for outdoor testing only, under clear sky, quasi-steady state conditions. 1.7 Selection and preparation of the collector (sampling method, preconditioning, mounting, alignment, etc.), calculation of efficiency, and manipulation of the data generated through use of this standard for rating purposes are beyond the scope of this test method, and are expected to be covered elsewhere. 1.8 This test method does not provide a means of determining the durability or the reliability of any collector or component. 1.9 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard. 1.10 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. 1.11 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee. ====== Significance And Use ====== 5.1 This test method is intended to provide test data essential to the prediction of the thermal performance of a collector in a specific system application in a specific location. In addition to the collector test data, such prediction requires validated collector and system performance simulation models that are not provided by this test method. The results of this test method therefore do not by themselves constitute a rating of the collector under test. Furthermore, it is not the intent of this test method to determine collector efficiency for comparison purposes since efficiency should be determined for particular applications. 5.2 This test method relates collector thermal performance to the direct solar irradiance as measured with a pyrheliometer with an angular field of view between 5 and 6°. The preponderance of existing solar radiation data was collected with instruments of this type, and therefore is directly applicable to prediction of collector and system performance. 5.3 This test method provides experimental procedures and calculation procedures to determine the following clear sky, quasi-steady state values for the solar collector: 5.3.1 Response time, 5.3.2 Incident angle modifiers, 5.3.3 Near-normal incidence angular range, and 5.3.4 Rate of heat gain at near-normal incidence angles. Note 4: Not all of these values are determined for all collectors. Table 1 outlines the tests required for each collector type and tracking arrangement. × = Required. ⊗ = Required but method may not be practicable for point focus collectors—Safety precautions and technical precautions must be followed because of potential damage to equipment and subsequent damage to personnel due to high levels of solar irradiance on the receiver support structure. ** = Optional test that may provide useful information on the effect of the accuracy of the manufacturer's tracking equipment on thermal performance. 5.4 This test method may be used to evaluate the thermal performance of either ( 1 ) a complete system, including the tracking subsystems and the thermal collection subsystem, or ( 2 ) the thermal collection subsystem. 5.4.1 When this test method is used to evaluate the complete system, the test shall be performed with the manufacturer's tracker and associated controls, and thus the effects of tracking error on thermal performance will be included in the results. Linear single-axis tracking systems may be supplemented with the test laboratory's tracking equipment to effect a two-axis tracking arrangement. 5.4.2 When evaluating a thermal collection subsystem, the accuracy of the tracking equipment shall be maintained according to the restrictions in 10.3 . 5.5 This test method is to be completed at a single appropriate flowrate. For collectors designed to operate at variable flowrates to achieve controlled outlet temperatures, the collector performance shall be characterized by repeating this test method in its entirety for more than one flowrate. These flowrates should be typical of the actual operating conditions of the collectors. 5.6 The response time is determined to establish the time required for quasi-steady state conditions to exist before each thermal performance test to assure valid test data, and to determine the length of time over which the quasi-steady state performance is averaged. The response time is calculated from transient temperature data resulting from step changes in intercepted solar irradiance with a given flow rate. Initial quasi-steady state conditions are established, the irradiance level is then increased or decreased suddenly, and the final quasi-steady state conditions are established. For most collectors covered by this test method, the difference in the response time determined by each of the two procedures will be small in terms of actual time. It is recognized that for some collectors, particularly those with long fluid residence times, the difference in the two values of response time may be large. However, the difference has not been found to influence the remainder of the test method. 5.7 The incident angle modifier is measured for linear single-axis tracking collectors so that the thermal performance at arbitrary angles of incidence can be predicted from the thermal performance measured at near-normal incidence as required in this test method. This is necessary because, during actual daily operation, linear single-axis tracking collectors will usually be normal to the sun only once or twice. 5.7.1 At non-zero angles of incidence, the thermal performance of a linear single-axis tracking collector may change for several reasons: 5.7.1.1 Increased or decreased reflectance, transmittance, and absorptance at the concentrator and receiver surfaces, or 5.7.1.2 Increased or decreased interception of the reflected or refracted solar radiant energy by the receiver. 5.7.1.3 That part of the decreased interception that is due to loss of collected energy at the ends of the absorber can be calculated analytically from the collector geometry as an end effects factor (see Appendix X1 ). 5.7.2 The preferred procedure for determining the incident angle modifier minimizes heat loss from the receiver by requiring that the working heat transfer fluid be the same as is used in the rest of the test method, and that it be maintained at an inlet temperature approximately equal to ambient temperature. It is realized, however, that this procedure may not be practical to perform as specified, since some heat transfer oils become too viscous near ambient temperatures to be pumped through the fluid test loop, or the fluid test loop cannot practicably cool the working fluid sufficiently to approximate the ambient temperatures that typically occur in the winter in cold climates. In these cases, either Alternative Procedure A or B may be used at the discretion of the manufacturer or supplier. Alternative Procedure A uses water as the working fluid at an inlet temperature approximately equal to ambient to minimize heat losses, but the procedure requires careful cleaning of the collector fluid passages, possibly use of a separate fluid test loop, and may cause corrosion if the collector fluid passages are incompatible with water. Alternative Procedure B uses the same heat transfer fluid as is used in the rest of the test method, but at an elevated temperature which is as close as practicable to ambient. Alternative Procedure B involves higher heat losses from the receiver which must be calculated and corrected for. An approximate correction for these heat losses is obtained in Alternative Procedure B by determining the nonirradiated heat loss for the same fluid inlet temperature. 5.8 Determination of the angular range of near-normal incidence is required to establish the test conditions under which the measured thermal performance will adequately represent the thermal performance at true normal incidence. Note 5: Measurement of angular range of the near-normal incidence also provides data that can be used to evaluate the sensitivity of the thermal performance of the tracking accuracy. 5.9 The thermal performance of the solar collector is determined under clear sky conditions and at near-normal incidence because these conditions are reproducible and lead to relatively stable performance.
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