TRANSIENT TEST METHODS FOR FLAT-PLATE COLLECTORS - REVIEW AND EXPERIMENTAL EVALUATION

This communication presents a review of the literature on the test met hods of flat-plate solar collectors under varying environmental condit ions. The methods are classified into different groups based on their common features. The methods are examined critically from the point of view of their: (a) experimental procedures, (b) techniques of paramet er identification and (c) output results. Four test procedures have be en evaluated experimentally in detail. The results from different test s are compared with each other and with the steady state Values based on the ASHRAE 93-86 standard. The review reveals that test procedures based on multi-node models may not be implemented accurately in experi mentation. They require impractical measurements or lead to complicate d equations for estimation of parameters. A few one-node models includ e inconvenient test runs or confusing data reduction techniques. The r esults of the experimental investigation indicate that Saunier's metho d yields parameters close to those obtained on the basis of the ASHRAE standard. However, the results are greatly affected by measurement er rors and propagation of error in various test stages. Exell's method e liminates the inconvenient tests of Saunier's method, but includes a l ong chain of experiments and does not provide a good estimate of colle ctor characteristics. Rogers' method yields a good estimate of optical efficiency, but underpredicts the heat loss term; it also involves a large amount of computation. The filter method leads to a good estimat e of the heat loss term, but it overpredicts the optical efficiency. I n addition, precise control of the flow rate and inlet temperature is essential in the last two methods. (C) 1997 Elsevier Science Ltd.