Taynara G.S. Lago

Bio: Taynara G.S. Lago is an academic researcher from State University of Campinas. The author has contributed to research in topics: Gas compressor & Refrigeration. The author has an hindex of 3, co-authored 10 publications receiving 31 citations. Previous affiliations of Taynara G.S. Lago include Federal University of Paraíba.

Parametric investigation of the enhancing effects of finned tubes on the solidification of PCM

Abstract: This paper presents the results of a study on the enhancement of solidification around finned tubes and the development of correlations to predict their thermal performance. The effects of the geometrical and operational parameters on the solidification process and thermal performance are investigated. A numerical code to predict the solidification around radial finned tubes based on pure conduction and the enthalpy method is developed and validated against experimental results showing good agreement. Results of additional experiments were also used to develop correlations for the interface position, interface velocity and the time for complete solidification. The fin diameter, and low tube wall temperature enhance the interface position and velocity, and reduce the time for complete solidification. Experiments showed that there is an optimum fin diameter for which the solidified phase change material (PCM) and stored energy are the highest. The proposed correlations for the interface position, interface velocity and the time for complete phase change seem to agree well with experimental results within maximum deviation of 4%, 7% and 1.03%, respectively. Hence, the correlations can be used for overall and quick estimates of solidification of PCM around radial finned tubes.

Ventilated double glass window with reflective film: Modeling and assessment of performance

Abstract: In the present study, the thermal behavior of a ventilated double glass window with a solar reflective film is numerically investigated and validated against results available in the literature. The objectives of the study are to develop a validated robust thermal model for the ventilated double glass window, make it versatile so that it can incorporate different inserts (such as reflective and absorptive films, etc.), different glass sheets and different fluids and can be integrated with other available design tools. The proposed ventilated double window is composed of two glass sheets separated by a gap forming a channel having a solar reflective film on the internal surface of outer glass sheet. The model is based on the equations of mass, momentum and the energy conservation equations in steady state. Boussinesq approximation is used to evaluate buoyancy term. The discretization of conservative equations is done using the finite volume method. A numerical code is developed and validated against available experimental and numerical results. Thermal performance of the ventilated double glass window is assessed under different conditions and the results show that in order to reduce the heat gain in the internal ambient, the optimum spacing between the glass sheets should be at least 2.5 cm. The solar reflective film in a ventilated double glass window can reduce the penetrating solar energy by about 64.7% in comparison with a traditional double glass window.

Experimental correlations for the solidification and fusion times of PCM encapsulated in spherical shells

Abstract: This paper reports the results of a study to investigate and develop correlations for the parameters affecting the time for complete solidification and fusion in spherical shells. For this study, f...

Natural Airflow in a Reversible Double-Glass Window with Reflective Film for Building Applications

Abstract: This investigation is focused on assessing the thermal performance of a ventilated double-glass reversible window with reflective film for building applications. The window is composed of t...

Experimental study of fusion and solidification of phase change material (pcm) in spherical geometry

Abstract: The objective of this work is to investigate the parameters affecting the time for complete solidification and fusion in spherical capsules and develop correlations between this time and the investigated parameters. These correlations will be used in the numerical simulations of latent heat storage systems of the fixed bed type having the phase change material, PCM encapsulated in spherical containers. Four spherical shells of 35, 76, 106 and 131 mm diameter were used at temperatures ranging from -20°C to -5°C for solidification process and temperature of 10°C, 18°C, 25°C for the melting process. Water and mixtures of water and polyethylene glycol in percentages ranging from 7.5% to 50% were used as PCM. Based on the experimental results correlations of the time for complete solidification and complete fusion were developed and compared with the experimental measurements showing good agreement and confirming the suitability of using these correlations to predict the complete phase change times. These correlations are applicable in the ranges: 0.076 m ≤ Diameter of spherical capsule ≤ 0.131m, 0.1% ≤ concentration of polyethylene glycol ≤ 0.5%, -20°C ≤ Initial temperature of PCM ≤ -5°C, 10°C ≤ Thermal bath temperature≤ 25°C. The differences between the values predicted by the correlation and the experimental measurements are below 10%.

Numerical Heat Transfer And Fluid Flow

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Melting and solidification of PCMs inside a spherical capsule: A critical review

Abstract: To date, numerous phase change materials (PCM) have been developed for application in latent heat storage systems. There are many issues in the process from the development of PCM to using them in storage systems, which should be resolved. The problem of heat transfer in PCMs during the phase change process is the most important one. Latent heat storage containers usually have simple geometrical forms such as a sphere, cylinder, cylindrical annulus, rectangular enclosure, etc. A large number of papers were published on melting and solidification processes in PCMs. Therefore, there is a pressing necessity for generalizing the art of the state in this field and establish how accumulated knowledge meets practical requirements. The present review considers the current state in investigations of heat transfer in a spherical shell. Heat transfer in PCMs during constrained melting (solid PCM fixed inside the vessel), unconstrained (unfixed) melting and solidification, and phase change in finned shells are analyzed. It is shown that currently, there is no satisfactory description of the constrained melting process. For unconstrained melting and solidification, some correlations are suggested, describing these processes. The applicability range of the proposed correlations, as well as their accuracy were investigated and established. To intensify the process of phase change inside the spherical container, the use of orthogonal fins is appropriate option compared to the employ of circumferential fins.

A numerical study on the effects of nanoparticles and stair fins on performance improvement of phase change thermal energy storages

Abstract: Using nano-enhanced phase change materials is a widespread passive method to improve the melting performance, and also the storage capacity of the thermal energy storage units. In this study, the effects of CuO nanoparticles ( 0 ≤ φ ≤ 1.5 % ) and new proposed stair fins on the efficiency improvement of latent heat thermal energy storage units are investigated. The stair fins are arranged in both upward and downward directions from the heated walls and the stair ratio is in the range of 0.67 ≤ b / c ≤ 4.0 . One of the vertical walls of the PCM enclosure is subject to uniform temperature and the other three walls are insulted. The numerical results show that by adding nanoparticles with volume concentration of φ = 1.5 % for b/c = 0.67 to the flow, the energy storage capacity is enhanced by 9.1% compared to the pure PCM with downward fins. The maximum energy storage capacity of 474.1 kJ is achieved by using descending stair fins with b/c = 4.0 and φ = 1.5 % which is much higher compared to the cases without nano additives. Besides, the melting performance is significantly improved by adding the nanoparticles. In fact, nanoparticles improve the thermal conductivity of the fluid and also act as a heat sink to absorb the heat from the fins. The downward fins with larger stair ratios (b/c = 4.0) perform significantly better than the upwards ones which is because of the free convection effects and the recirculations flows on the upper face of these fins.

Effect of orientation on thermal performance of a latent heat storage system equipped with annular fins – An experimental and numerical investigation

Abstract: Because of high energy storage density, latent heat storage is preferred over other thermal energy storage methods. The most common configuration of latent heat storage unit is shell and tube configuration, the performance of which greatly depends on its orientation. The influence of orientation may get altered when fins are provided for heat transfer enhancement. Hence, the current work is intended to examine the performance of a shell and tube latent heat storage unit in which annular fins are attached to the tube. Both experimental and numerical investigations are carried out to get a thorough insight into the melting behavior. The experiments are conducted at 0°, 30°, 60° and 90° inclinations (0° corresponds to vertical configuration); both energy and exergy analyses are carried out. The findings revealed that the melting rate is nearly same at all the inclinations during the initial stages. Later with the progression of time, the melting rate is decreased and the decrement is more for horizontal configuration. 85.63% more time is required for complete melting at 90° inclination (horizontal) in comparison with the 0° inclination. This is because of the suppression of convective transport in the bottom half for the case of horizontal orientation. Higher energy efficiency is obtained for horizontal orientation, whereas vertical orientation exhibited higher exergy efficiency. Energy stored, average Nusselt number and effectiveness of the latent heat storage system are also higher for 0° inclination.

A review on container geometry and orientations of phase change materials for solar thermal systems

Abstract: Phase change materials (PCM) are employed to store thermal energy in solar collectors, heat pumps, heat recovery, hot and cold storage. PCMs are encapsulated primarily in shell-and-tube, cylindrical, triplex-tube, spherical, rectangular, and trapezoidal containers. This review focuses on PCM's melting and solidification in different container geometries and their orientations for heat storage in solar thermal systems. The thermal storage performance of PCM depends upon fins, nanoparticle addition, container geometry, and orientations. The operating parameters such as heat transfer fluid temperature, flow rate, and initial temperature of storage material play a dominant role in PCM melting. The use of fins and nanoparticles in the shell-and-tube containers increase the melting rate to 71 and 62.6%, whereas the change in container orientation improved the melting rate up to 47.5%. The addition of fins increases the melting rate significantly, followed by nanoparticles and the container's orientation. The variation of the container's geometry and its orientation improves PCM melting passively. Container materials are preferably stainless steel and aluminum for organic and inorganic PCMs to avoid corrosion. PCM container geometry and orientations are practical passive heat transfer enhancement techniques in the long-term compared to adding nanoparticles and attaching fins. This review focuses on significant aspects of PCM container designs for practical solar thermal storage.