Hamid El Qarnia

Numerical Study of a Shell-and-Tube Latent Thermal Energy Storage Unit Heated by Laminar Pulsed Fluid Flow

ABSTRACT The present study aims to investigate the effect of the pulsed fluid flow on the thermal performance of a latent heat storage unit (LHSU). The storage unit consists of a shell-and-tube in which phase change material (PCM) occupied the shell space and the heat transfer fluid (HTF) flows in the inner tube. The present study is motivated by the need to intensify heat transfer and accelerate melting process in LHSU. A mathematical model based on the conservation equations of energy in both HTF and PCM has been developed. The finite volume approach was used for the discretization of equations. The developed model has been validated by comparing the obtained numerical results with experimental, analytical, and numerical data found in literature. The effects of the pulsation frequency and amplitude, the Reynolds and Stefan numbers on the thermal performance and behavior of the LHSU were investigated. The parametric study showed that the pulsating parameters (frequency and amplitude) affect the thermal performance of the LHSU. The results reveal reduction in the melting time for low pulsating frequency (less than 0.052) and high pulsating amplitude. For pulsating amplitude of 6 and pulsating frequency of 0.01, a reduction up to 13% (at Reynolds number of 500 and Stefan number of 0.16) was obtained. The results also showed that the Reynolds and Stefan numbers strongly affect the heat transfer rate, and the low melting time is obtained for high Reynolds and Stefan numbers.

Passive Cooling of Protruding Electronic Components by Latent Heat of Fusion Storage

The aim of the present work is to study the thermal performance of a hybrid heat sink used for cooling management of protruding substrate-mounted electronic chips. The power generated in electronic chips is dissipated in phase change material (PCM) (n-eicosane with melting temperature T m = 36°C) that filled a rectangular enclosure. The advantage of using this cooling strategy is that the PCMs are able to absorb a high amount of heat generated by electronic component (EC) without acting the fan, during the charging process (melting of the PCM). A two-dimensional mathematical model was developed in order to analyze and optimize a heat sink. The governing equations for masse, momentum, and energy transport were developed and discretized by using the volume control approach. The resulting algebraic equations were next solved iteratively by using tri diagonal matrix algorithm. A series of numerical investigations were conducted in order to examine the effects of the heat generation based Rayleigh number, Ra, and the position of the bottom electronic component, L h , on the thermal behavior of the proposed cooling system. Results are obtained for velocity and temperature distributions, maximum temperature heat sources, percentage contribution of plate (substrate) heat conduction on the heat removal from electronic components, temperature profile within finite conductive plate and local heat flux density at the plate―modules/PCM interface. The effect of these two key parameters on the electronic component working time (time required by electronic components to reach a critical temperature, T cr ) was analyzed.

Thermal Control of Protruding Electronic Components with PCM: A Parametric Study

This work deals with the melting and natural convection in a rectangular enclosure heated from three discrete protruding electronic components (heat sources) mounted on a conducting vertical plate (substrate). The heat sources generate heat at a constant and uniform volumetric rate. A part of the power generated in the heat sources is dissipated to the phase change material (PCM, n-eicosane with a melting temperature T m = 36°C) that filled the enclosure. To investigate the thermal behavior of the proposed heat sink, a mathematical model, based on the mass, momentum, and energy conservation equations was developed. The model has been verified and then validated comparing the melting front with available experimental results. Numerical investigations have been conducted in order to examine the effects of the electronic components thickness and the plate thermal diffusivity on the maximum temperature of electronic components. The percentage contribution of plate heat conduction on the total removed heat and temperature profile in the plate have also been analyzed. Correlations for the nondimensional secured working time (time to reach the threshold temperature, T cr = 75°C) and its corresponding melt fraction were derived.

Modeling and Numerical Investigation of Latent Heat Storage Unit Using Paraffin Wax P116

The present work concerns the modeling and numerical simulation of the melting of a phase change material (PCM) in a latent heat storage unit. A mathematical model based on the conservation equations of mass, momentum, and energy has been developed. These equations are then discretized using the finite volume approach and the pressure correction method for the treatment of velocity-pressure coupling. The energy conservation equation of PCM was formulated using the enthalpy method. A series of simulations were carried out on a type of phase change material (Paraffin Wax P116) to study the impact of the mass flow rate and heat transfer fluid (HTF) inlet temperature on the performance of the storage unit. The flow structure and the temperature field are also investigated.

The effect of the lower fin position on the PCM solidification process in a finned rectangular enclosure

This study focuses on the heat transfer enhancement during solidification process of a phase change material (PCM) inside internally finned rectangular heat storage. Initially, the PCM (paraffin n-Octadecane) is in the liquid state at a temperature above the melting point. The solidification process occurs when the finned wall is abruptly cooled at a temperature below the melting point. To resolve the 2D transient problem heat transfer, the mass, momentum and energy conservation equations were integrated using the finite volume method. The enthalpy method was adopted to formulate the energy equation. To investigate the effect of fins on the thermal performance of the system during the discharging operational mode, a comparative study of finned and unfinned enclosures containing the same mass of PCM has been conducted. A parametric study was performed to evaluate how the storage performance is affected by the fins position. Numerical results show that the addition of fins in the PCM is an effective way to improve the heat transfer in the latent heat storage systems (LHSS).

Approximate Analytical Solution for One-Dimensional Solidification Problem of a Finite Superheating Phase Change Material Including the Effects of Wall and Thermal Contact Resistances

This work reports an analytical solution for the solidification of a superheating phase change material (PCM) contained in a rectangular enclosure with a finite height. The analytical solution has been obtained by solving nondimensional energy equations by using the perturbation method for a small perturbation parameter: the Stefan number, . This analytical solution, which takes into account the effects of the superheating of PCM, finite height of the enclosure, thickness of the wall, and wall-solid shell interfacial thermal resistances, was expressed in terms of nondimensional temperature distributions of the bottom wall of the enclosure and both PCM phases, and the dimensionless solid-liquid interface position and its dimensionless speed. The developed solution was firstly compared with that existing in the literature for the case of nonsuperheating PCM. The predicted results agreed well with those published in the literature. Next, a parametric study was carried out in order to study the impacts of the dimensionless control parameters on the dimensionless temperature distributions of the wall, the solid shell, and liquid phase of the PCM, as well as the solid-liquid interface position and its dimensionless speed.

Numerical Analysis of a Hybrid Heat Sink Using Phase Change Material: Application to Cooling of Electronic Components

The aim of the present work is to study the thermal performance of a hybrid heat sink used for cooling management of protruding substrate-mounted electronic chips. The power generated in electronic chips is dissipated in phase change material (PCM n-ecosane with melting temperature Tm = 36°C) that filled a rectangular enclosure. The advantage of using this cooling strategy is that the PCMs are able to absorb a high amount of heat generated by electronic component (EC) without acting the fan, during the charging process (melting of the PCM). A (2D) mathematical model was developed in order to analyze and optimize a heat sink. The governing equations for masse, momentum and energy transport were developed and discretised by using the volume control approach. The resulting algebraic equations were next solved iteratively by using TDMA algorithm. Numerical investigations were conducted in order to optimize the thermal performance of the heat sink. The optimization involves determination of the key parameters of the heat sink that maximize the time required by the base of the electronic component to reach a critical temperature.Copyright