Analysis of a laboratory scale thermal energy accumulator using two-phases heterogeneous paraffin wax-water mixtures

Standardised methods for the determination of key performance indicators for thermal energy storage heat exchangers

“…Often, the local PCM temperatures are used to validate numerical results with experimental measurements (e.g., [65,98,104,122,129,130]). In contrast, experimental studies are limited to discrete sensor locations (e.g., [63,64,69,72,83,[87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][104][108][109][110][111][112][113][114][115][116][117][118]) or global liquid fraction techniques (e.g., [87,101]).…”

“…In numerical studies reporting internal energy as a function of time is commonly done although most studies report latent stored internal energy (e.g., [71,99,104,130]) or total liquid fraction (e.g., [65, 66, 68, 70, 71, 75, 77, 93, 99, 102, 104, 106, 109, 111, 113, 115, 120-122, 124-128, 130-132, 134, 136]) instead of total stored energy (e.g., [75,111,115,134,137,138]). In experimental studies, the total liquid fraction is sometimes reported (e.g., [67,87,101]) however local temperature measurements are far more commonly reported (e.g., [63,64,69,72,76,83,[87][88][89][90][91][92][93][94][95][96][97][98][99][100][101][102][103][105][106][107][108][109][110][111][112][113]…”

“…The mass flow rate, in-, and outlet temperature of the HTF are some of the most accessible measurements for LTES heat exchangers and are therefore often reported in experimental studies (e.g., [62, 63, 65, 66, 89, 91, 92, 95-97, 106, 123, 124, 141, 152]). Most authors calculate the efflux of energy (e.g., [62,72,76,77,83,90,92,96,97,106,108,110,117,118,124,126,152]), and some the integrated efflux of energy (e.g., [83,87,92,95,97,100,101,103,117,126,152]).…”

“…Several authors compare the integrated efflux of energy at the end of charging to the internal energy change of the heat exchanger between two temperatures (e.g., [8,92,103,152]). In the case of negligible losses, both values should be equal which allows to link the efflux of energy to the total internal energy change through the conservation of energy (see Equation 3) (e.g., [8,118,152]).…”

Division of paraffin melting zone based on multiscale experiments

“…Mahdi et al [12] took industrial paraffin as phase change material and studied the melting behavior of paraffin in different tubular and shell latent heat accumulators through visualization experiments. Reyes et al [13] conducted visualization experiments with emulsions with different volume fractions of paraffin to study the feasibility of replacing part of paraffin with water as phase change materials.…”