Latent heat thermal storage systems (LHTS) utilize their latent heat capacity to dissipate high heat fluxes while maintaining quasi-isothermal conditions. Phase change materials (PCMs) absorb a large amount of energy during their phase transformation from solid to liquid, maintaining quasi-isothermal conditions. However, they are often beset with low thermal conductivities which necessitate the use of a thermal conductivity enhancer (TCE) as it is impossible to design a device that can completely avoid sensible heat in the premelting or postmelting phase. In this study, the heat transfer performance of LHTS with cross plate fins as a TCE is numerically investigated for different values of fin thicknesses and fin numbers along the length and breadth. A hybrid artificial neural network coupled genetic algorithm (ANN-GA) is then used to obtain the optimized dimensions for the composite heat sink with cross plate fins as TCE for a fixed volume and a specific heat flux input. The numerically optimized configuration is finally validated with in-house experiments. © 2015 by ASME.

C. Balaji

Department of Mechanical Engineering

Rajesh Alayil

Data storage equipment

Fins (heat exchange)

Genetic algorithms

Heat convection

Heat flux

Heat sinks

Heat storage

Heat transfer

heating

Isotherms

Latent heat

Neural Networks

Phase change materials

Specific heat

Storage (materials)

Temperature control

COMPOSITE HEAT SINKS

Conjugate heat transfer

CROSS-PLATES

Heat transfer performance

HYBRID ARTIFICIAL NEURAL NETWORK

Latent heat thermal storage

Low thermal conductivity

OPTIMIZED CONFIGURATION

Thermal conductivity

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Conjugate Heat Transfer in Latent Heat Thermal Storage System With Cross Plate Fins

Journal of Heat Transfer

This paper reports the results of an experimental study to quantify the effect of heat transfer performance of a phase change material (PCM) based plate fin heat sink matrix under constant and intermittent heat loads. n-Eicosane with a melting temperature of 36.5 C is used as the phase change material. Such heat sinks, in general require heat transfer enhancement techniques, because of the low thermal conductivity associated with PCMs. A plate fin matrix made of aluminum is used in the present study to augment the heat transfer. The performance of the heat sink matrix with and without PCM is compared. Additionally, a heat sink filled with PCM, but without any fin is used for baseline comparisons. A series of experiments was conducted at a constant power level of 5-10 W (corresponding to a flux of 2-4 kW/m2) in steps of 1 W. Extensive experimental investigations were carried out at varying power levels by applying the heat flux intermittently by keeping the input heat constant. A step heat input is also applied for a fixed duration at various usage modes usually encountered in the thermal management of portable electronic devices. Parametric studies have been conducted by changing the PCM volume fraction, which is defined as the ratio of the volume of the PCM to the difference between the total empty volume of the heat sink and the volume occupied by the fins and the effect of these on the thermal performance of the plate fin heat sink matrix for both melting and solidification are elucidated in this study. © 2014 Elsevier Masson SAS. All rights reserved.

International Journal of Thermal Sciences

Thermal performance of a PCM heat sink under different heat loads: An experimental study

This paper reports the results of an experimental investigation carried out to characterize the thermal performance of different configurations of phase change material (PCM) based pin fin heat sinks. Paraffin wax and n-eicosane are used as the PCMs. Aluminium is used to make the heat sinks and the volume fraction is varied by changing the number of pin fins. Baseline comparisons are done with a heat sink filled with PCM, without any fin. The effect of PCM volume fraction on the heat transfer performance is also studied. The results showed that there exists sufficient scope to optimize the thermal design of the heat sink. An Artificial Neural Network-Genetic Algorithm hybrid algorithm is then developed to determine the optimum configuration of the pin fin heat sink that maximizes the operating time for the n-eicosane based heat sink. The resulting optima was found to be valid even for the paraffin wax based PCM. © 2013 Elsevier Ltd. All rights reserved.

Applied Thermal Engineering

Thermal optimization of PCM based pin fin heat sinks: An experimental study

Thermal performance in terms of enhancement ratios and the effect of orientation of a copper porous matrix filled phase change material (PCM) based heat sink are experimentally studied in this paper. N-eicosane is used as the phase change material. A copper open cell metal foam, press fitted into an aluminium casing is the thermal conductivity enhancer. In PCM based heat sinks, low thermal conductivity associated with PCMs makes the use of enhancement techniques inevitable for better thermal performance. A plate heater with an overall dimension of 60×42mm2 with 2mm thickness is used to mimic the heat generation in electronic chips. The effect of orientation of the heat sink on thermal performance is studied by developing a tracking system, capable of placing the heat sink at any specified orientation. © 2013 Elsevier Ltd.

International Communications in Heat and Mass Transfer

Experimental investigations on thermal performance enhancement and effect of orientation on porous matrix filled PCM based heat sink

This paper reports the results of an experimental investigation of the performance of finned heat sinks filled with phase change materials for thermal management of portable electronic devices. The phase change material (PCM) used in this study is n-eicosane and is placed inside a heat sink made of aluminium. Aluminium acts as thermal conductivity enhancer (TCE), as the thermal conductivity of the PCM is very low. The heat sink acts as an energy storage and a heat-spreading module. Studies are conducted for heat sinks on which a uniform heat load is applied for the unfinned and finned cases. The test section considered in all cases in the present work is a 80 × 62 mm 2 base with TCE height of 25 mm. A 60 × 42 mm 2 plate heater with 2 mm thickness is used to mimic the heat generation in electronic chips. Heat sinks with pin fin and plate fin geometries having the same volume fraction of the TCE are used. The effect of different types of fins for different power level (ranging from 2 to 7 W) in enhancing the operating time for different set point temperatures and on the duration of latent heating phase were explored in this study. The results indicate that the operational performance of portable electronic device can be significantly improved by the use of fins in heat sinks filled with PCM. © 2011 Elsevier Ltd. All rights reserved.

International Journal of Heat and Mass Transfer

Experimental investigations on phase change material based finned heat sinks for electronic equipment cooling

Using an approach that couples genetic algorithm (GA) with conventional numerical simulations, optimization of the geometric configuration of a phase-change material based heat sink (PBHS) is performed in this paper. The optimization is done to maximize the sink operational time (SOT), which is the time for the top surface temperature of the PBHS to reach the critical electronics temperature (CET). An optimal solution for this complex multiparameter problem is sought using GA, with the standard numerical simulation seeking the SOT forming a crucial step in the algorithm. For constant heat dissipation from the electronics (constant heat flux) and for three typical PBHS depths (A), predictive empirical relations are deduced from the GA based simulation results. These correlations relate the SOT to the amount of phase change material to be used in the PBHS (φ), the PBHS depth (A), and the heat-spreader thickness (s), a hitherto unconsidered variable in such designs, to the best of the authors' knowledge. The results show that for all of the typical PBHS depths considered the optimal heat-spreader thickness is 2.5% of the PBHS depth. The developed correlations predict the simulated results within 4.6% for SOT and 0.32% for φ and empowers one to design a PBHS configuration with maximum SOTfor a given space restriction or the most compact PBHS design for a given SOT. Copyright © 2008 by ASME.

Genetic algorithm based optimization of PCM based heat sinks and effect of heat sink parameters on operational time

Conjugate heat transfer in latent heat thermal storage system with cross plate fins

Journal	Journal of Heat Transfer
Publisher	American Society of Mechanical Engineers (ASME)
ISSN	00221481
Open Access	No