A dynamic model based on the piston flow concept for the thermal characterization of solar collectors

Analysis of thermal states of a flat-solar collector using state variables

“…The standard only specifies the methodology for determining the equivalent time constant, omitting the gain factor and the delay time [2]. The dynamic properties of a collector may be determined using numerous methods based on the energy balance of the collector and enabling the analysis of its thermal conditions [3][4][5][6]. However, due to the variable working point and thermal load, the dynamic properties of the collector under operating conditions may differ from those determined during normative tests or those determined in simulation tests [7].…”

Validation of a simple dynamic thermal performance characterization model based on the piston flow concept for flat-plate solar collectors

“…But it might not be the case for some specific flat-plate solar collectors, which will be discussed later in the present study. In addition, Amrizal et al (2012) defined the heat transport time…”

“…It should be considered in the simple model in order to determine the collector characteristic parameters. The simple collector dynamic model was constructed by Amrizal et al (2012) considering the first-order difference of the time and spatial segments for the ordinary differential equation 1, which is an approximation of the quick dynamic test model of solar collectors (Muschaweck and Spirkl, 1993). In the model the solar collector was evenly divided into N segments as shown in Figure 2 and each segment should fulfil Equation 1.…”

“…is not wise to directly set the coefficient 3 c = 1 as argued by Amrizal et al (2012), which will be discussed in section 4.3.…”

“…Noting that it N T is the data sequence of the collector outlet temperature ( it fo T ) and it T 0 denotes the collector inlet temperature ( it fi T ) according to the collector segment division illustrated in Figure 2, the collector outlet temperature it N T can be expressed as Equation 8using Equation 6or (7). Equation 8is different from the multilinear relationship described by Amrizal et al (2012) since 3 c can not be hastily set as 1.…”