ASTM E905-87(R2021) pdf free download

ASTM E905-87(R2021) pdf free download.Standard Test Method for Determining Thermal Performance of Tracking Concentrating Solar Collectors
1. Scope
1.1 This test method covers the determination of thermal performance oftracking 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 perfor- mance is negligible and whose performance can be character- ized in terms of direct irradiance. N OTE 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 collec- tion 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.1.5 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.), calcula- tion 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 determin- ing the durability or the reliability of any collector or compo- nent. 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 appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.11 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
3. Terminology
3.2.4 end effects, n—in linear single-axis tracking collectors, the loss of collected energy at the ends of the linear absorber when the direct solar rays incident on the collector make a non-zero angle with respect to a plane perpendicular to the axis of the collector. 3.2.5 fluid loop, n—assembly of piping, thermal control, pumping equipment and instrumentation used for conditioning the heat transfer fluid and circulating it through the collector during the thermal performance tests. 3.2.6 module, n—the smallest unit that would function as a solar energy collection device. 3.2.7 near-normal incidence, n—angular range from exact normal incidence within which the deviations in thermal performance measured at ambient temperature do not exceed 62 %, such that the errors caused by testing at angles other than exact normal incidence cannot be distinguished from errors caused by other inaccuracies (that is, instrumentation errors, etc.).3.2.9 response time, n—time required for ∆ t a to decline to 10 % ofits initial value after the collector is completely shaded from the sun’s rays; or the time required for ∆t a to increase to 90 % of its value under quasi-steady state conditions after the shaded collector at equilibrium is exposed to irradiation. 3.2.10 quasi-steady state, n—refers to that state of the collector when the flow rate and inlet fluid temperature are constant but the exit temperature changes “gradually” due to the normal change in solar irradiance that occurs with time for clear sky conditions. 3.2.10.1 Discussion—It is defined by a set of test conditions described in 10.1. 3.2.11 solar irradiance, direct, in the aperture plane, n—direct solar irradiance incident on a surface parallel to the collector aperture plane. 3.2.12 solar irradiance, total, n—total solar radiant energy incident upon a unit surface area (in this standard, the aperture of the collector) per unit time, including the direct solar irradiance, diffuse sky irradiance, and the solar radiant energy reflected from the foreground. 3.2.13 thermal performance, n—rate of heat flow into the absorber fluid relative to the incident solar power on the plane of the aperture for the specified test conditions.