Hameed B. Mahood

Bio: Hameed B. Mahood is an academic researcher from University of Surrey. The author has contributed to research in topics: Heat transfer & Phase-change material. The author has an hindex of 16, co-authored 53 publications receiving 646 citations. Previous affiliations of Hameed B. Mahood include University of Misan.

Numerical study and experimental validation of the effects of orientation and configuration on melting in a latent heat thermal storage unit

Abstract: Enhancing the effectiveness of solar power, including daytime storage for overnight use, is essential to reduce fossil fuel usage. This work explores the melting behaviour of paraffin wax in shell and tube latent heat thermal storage unit (LHSU) in different configurations and orientations. Numerical simulation were carried out and compared with experimental measurements for non-finned and finned configurations arranged vertically during the melting (charging) process. A commercial paraffin wax was used as a phase change material (PCM). The temperature and liquid fraction of the PCM during the course of the melting process in both configurations were used for model validation. When considering the liquid fraction, the numerical results showed excellent qualitative agreement with the experimental images for all the cases being studied. Specifically, the shape and progress of the melting front showed good agreement between the experiments and numerical results. Furthermore, the model predicted well the experimentally measured temperature in the melting PCM, with a maximum average discrepancy of 3.6%. The validated model was then used to investigate different process configurations. The results indicated that the addition of fins enhanced the melting process by an average of 50%. The non-finned tubes had a superior melting rate in the horizontal orientation over the vertical orientation, while orientation was found to have only a minor impact on the melting process with finned tubes.

Numerical investigation on the effect of fin design on the melting of phase change material in a horizontal shell and tube thermal energy storage

Abstract: It has previously been proven that fins can significantly enhance the thermal performance of latent heat thermal energy storage (LHTS) units. Nevertheless, the magnitude of improvement, especially in a horizontal LHTS, is still less than that required to address some of the existing challenges in solar energy applications. The tendency of the phase change material (PCM) at the bottom of the horizontal storage to remain solid because of the absence of convection currents to promote heat transfer must be tackled practically for this technology to be viable in different thermal applications. Thus, the fin configuration around the circumference of the horizontal storage must be optimised to enhance the melting rate and therefore improving efficiency. In the present paper, the thermal performance during the melting process for PCM (RT-50) in a horizontal LHTS unit was studied numerically with a view to optimizing the fin configuration. The baseline case of bare heat transfer fluid (HTF) tubes was compared with finned surfaces with four different fin angles ( θ = 72 o , 60 o , 45 o and 30 o ) with four different heights (0.2, 0.4, 0.6 and 0.8 of the hydraulic radius of the annulus (Rh)). The average temperature of the PCM, its liquid fraction, and velocity distribution during the melting process were investigated. The numerical results showed that increasing fin height (using a fixed fin configuration: θ = 72 o ) significantly improved the thermal performance of the horizontal LHTS. When the fin height was varied from 0 (bare HTF tube) to 0.8 of Rh, a shortening of the total melting time by approximately 50% was observed. For this fin height 0.8 Rh, it was shown that having a smaller angle between the fins, with all of them mounted below the horizontal axis of the LHTS unit, led to significant enhancement in the thermal performance of the storage. This is because the enhanced heat transfer surfaces are targeted to the regions of the LHTS unit where heat transfer is poorest in the bare tube configuration, as mentioned above. Thus, the total PCM melting time was reduced by 6.7%, 14.3%, 16.7% and 10.0% when the fin angle was changed respectively from 72o to 60o, from 60o to 45o, from 45o to 30o, and finally from 30o to 15o.

Experimental investigation of the thermal performance of a helical coil latent heat thermal energy storage for solar energy applications

Abstract: Thermal performance of a Latent Heat helical coil Thermal Energy Storage (LHTS) was investigated experimentally for both phases; melting and solidification processes. Paraffin wax (type P56-58) and tap water were used as a Phase Change Material (PCM), and a Heat Transfer Fluid (HTF), respectively. The paraffin wax (PCM) thermos-physical properties were determined experimentally. To simulate the solar energy conditions, three different initial temperatures (70 °C, 75 °C and 80 °C) and flow rates (1 L/min, 3 L/min and 5 L/min) of the HTF were tested throughout the PCM melting experiments, while the temperature of HTF was only 30 °C with the same flow rates for solidification process. The storage was completely insulated to reduce the heat losses. The PCM temperature during the melting and solidification processes was measured with time using 16 K-type calibrated thermocouples distributed along the PCM axially and radially. The experimental results showed that contrary to the solidification process, the melting was a superior in the helical coil LHTS under different operational conditions. Axial and radial melting fronts were noticed during the PCM melting process which considerably shortened the melting time under the effect of convection and a shape like a pyramid is formed at the core of the storage. Initial temperature of heat transfer fluid (HTF) was significantly affected the melting process and the increased of it from 70 °C to 75 °C and from 75 °C to 80 °C resulted in shortening the total melting time by about 34.5% and 27.2% respectively. An optimum HTF flow rate was observed during the melting process and it was found to be 3 L/min under the operational conditions of the present experiments. Contrary, the flow rate of HTF was insignificant during the solidification process. The initial temperature of HTF was slightly affected the effectiveness of the melting process. In spite of the efficiency of the melting process, enhancement of the solidification in the coiled LHTS is necessary in order to use the process in the thermal applications of solar energy.