Search

A compound enhancement method was proposed to improve the latent heat storage (LHS) performance of a shell-and-tube LHS unit, which is consisted of internal enhanced tube (ET) and multiple phase change material (PCM). Numerical validations on the presented method were performed based on comparisons of four different LHS cases: case 1 (basic case); case 2 (simple enhancement case); case 3 and 4 (compound enhancement cases). The results show that the simple enhancement case can only enhance PCM melting rate at the first half of the LHS tube; the compound enhancement case can obtain the synergy enhancement effect for the whole LHS tube. Compared with case 2, the PCM melting time is reduced by 37.3% and 17.4%, the total charging time is reduced by 25.6% and 16.9% for case 3 and case 4 respectively. For case 3, although the PCM melting time and charging time are the shortest, the total thermal energy storage (TES) capacity is reduced by 26.9% due to the lower PCM melting enthalpy. For case 4, not only the melting time and charging time can be obviously reduced, but also the total TES capacity is augmented by 6.6%.

The solar energy flux distribution on the outer wall of the inner absorber tube of a parabolic solar collector receiver is calculated successfully by adopting the Monte Carlo Ray-Trace Method (MCRT Method). It is revealed that the non-uniformity of the solar energy flux distribution is very large. Three-dimensional numerical simulation of coupled heat transfer characteristics in the receiver tube is calculated and analyzed by combining the MCRT Method and the FLUENT software, in which the heat transfer fluid and physical model are Syltherm 800 liquid oil and LS2 parabolic solar collector from the testing experiment of Dudley et al., respectively. Temperature-dependent properties of the oil and thermal radiation between the inner absorber tube and the outer glass cover tube are also taken into account. Comparing with test results from three typical testing conditions, the average difference is within 2%. And then the mechanism of the coupled heat transfer in the receiver tube is further studied.