The p. roposed test method is similar to the way according to ISO 9806-1 (1994), and basically, the main difference is that except the steady-state measurement there are some integral tests included to determine the overall thermal performance. It is a strict test condition to satisfy all of parameters for steady-state measurement, when solar irradiance would be influenced by cloud. So the whole process for measurement would be a long period and expensive. In the case of the actual utilization, the surrounding condition always is exposed in a dynamic mode. In order to simplify this in this proposal and broaden the test scope, during the day test continuous measurements should be operated whatever the fluctuation of solar radiance and a more widened range for temperature and flow rate. Through this kind of measurement a set of comprehensive data that would access to actual needs to some extents could be provided successfully.

The test determines steady-state efficiency of all-glass evacuated tube solar collectors in order to evaluate the thermal performance and consequently comparison with other kinds of solar collectors. The average global thermal efficiency, the relationship between the increments of outlet temperature and total solar energy on the collector plane, and the relationship between the increments of instantaneous efficiency and total energy on the collector plane are also determined. Moreover, manufacturers can optimize their products or design solar water heating system depending on the actual test results.

1.1. Scope

This test is a systematic and comparatively comprehensive test for determining the thermal performance of water heating solar collectors. The thermal behaviour is characterized by means of
whole collector tests using a “black box” approach. In the whole test process it contains that the experiment of determining the steady-state thermal performance of solar collectors, the experiment of determining the instantaneous efficiency of solar collectors, and the experiment of determining the thermal performance during the whole day operation.