Performance Of Heat Storage Unit Research Articles

Numerical study and parametric analysis on performance enhancement of a latent heat storage unit with fractal fins

Adding fractal fins is an approach to improve the heat storage performance. In this paper, a new type of fractal fins is established, and a new evaluation index is putting forward in order to analyze the performance of the heat storage unit from the view of temperature uniformity. The advantages of fractal fins and the optimal number of fins are discussed by temperature uniformity factor. Finally, the influence of angle ratio, length ratio and phase change material (PCM) parameters on heat storage units are discussed by dimensionless criterion number. The results show that the application of fractal fins can improve the performance of heat storage unit and the temperature uniformity factor can be reduced by 131.5 % at most. The heat storage unit with six fractal fins has the smallest temperature uniformity factor. The optimal angle ratio and length ratio are 2/3 and 0.5 respectively. The change of PCM parameters has different effects on different melting periods. This research has a further guiding role for the development of fractal finned latent heat storage units.

Applying branch-shaped fins for improvement of performance of heat storage unit

The irreversibility of storage unit furnished with branch shaped fins was evaluated in this paper. The various arrangements of fins contain three levels for number of curved fins and all branches connected to inner cold wall. The conduction mechanism has been boosted with dispersing nanoparticles (TiO2) in to paraffin (n-eicosane). The simulations for two dimensional geometries with considering laminar flow for liquid paraffin have been presented via FVM. The validation with solidification data of previous article proves the good accommodation. The required time for freezing of PCM for case with N = 2, 4 and 8 are 1.034, 1.027 and 1.020 times greater than that of NEPCM. As distance of curved fins from each other increases from 12.5 to 25 and 50 mm, the period declines around 23.34 % and 28.41 %, respectively. The minimum need time can be obtained when N = 8 and ϕ = 0.03 which takes 9965 s to reach full freezing.

Heat transfer analysis of a PCM in shell-and-tube thermal energy storage unit with different V-shaped fin structures

This study provides an alternative solution to enhance melting performance of phase change material by designing a novel V-shaped fin. Nineteen cases with different V-shaped fins is designed, the effects of angle, length, number and arrangement of fins on heat transfer performance of heat storage unit were studied. The response surface method was used to optimize the structure. Assessments on the melting fraction, temperature field, velocity distribution, and uniformity for melting are made. Results demonstrate that due to the effect of natural convection, the upper part melting speed is accelerated, resulting in a significant difference in the heat storage efficiency between the upper and lower half regions. The melting time of the lower half of the heat storage unit without fins accounting for 62.5 % of the whole melting time. Based on the above analysis, more and longer fins should be considered to be arranged at the bottom of the heat storage unit to improve the heat storage performance of the system. As noticed, the structure parameters change of fins has a significant effect on reducing the melting time of the whole phase change material. It can be found that there are optimal values for the structure parameters. The optimal fin structure parameters (fin angle α = 55°, fin length L1 = 9 mm, fin number N = 5, branch angle β = 55°, and branch length L3 = 3) obtained. The heat storage efficiency of the optimal fin structure was 2.57 times that without fins, and the heat storage time was shortened by 61.05 %. To be conclusive, adding fins to a heat exchanger is more beneficial than no fins, saving more energy storage time.

Effect of helical diameter on the performance of shell and helical tube heat exchanger: An experimental approach

In the present paper, shell and tube heat storage unit (HSU) with spiral tube is filled with phase change material (PCM) is experimentally investigated. Paraffin RT-35 is used to fill the HSU and water is chosen as HTF (heat transfer fluid). Performance of HSU is examined for Stefan numbers of 0.43, 0.48 and 0.53. Volume flow rate of HTF is 500ml/min. In order to evaluate the effect of helical diameter on performance of HSU three diameters 5, 7 and 9 cm are utilized. Results show that by increasing of Stefan number melting process accelerates and total melting time decreases. Results also indicate that increasing coil diameter causes a decrease in total melting time and also an increment in final average temperature of PCM. Absorbed energy by PCM is increased by increasing helical diameter of HTF tube.

Comparison of measured and predicted performance of heat storage unit packed with spheres of a local material

The present paper presents a comparison between the measured and predicted performance of a sensible heat storage unit. The storage unit is packed with spheres manufactured from a powder of certain type of Egyptiain clay (trade name “tafla”) produced at Abu-Siebera, Aswan. A special experimental set up was designed to predict the performance of the storage unit. The temperature distribution of the solid spheres was measured at different mass flow rates and at different time intervals. A comparison was made between these measured values and the corresponding values obtained using a numerical model based on finite difference techniques. The results showed a reasonable agreement between the measured and predicted temperature distribution. Finally, the pressure drop through the storage unit was measured and compared with the corresponding pressure drop calculated using two different empirical formulae.