F.L. Tan

Thermal Management of Mobile Phone using Phase Change Material

The power of the handheld electronics devices continues to increase because packaging advances reduce their size even as more features are added and enhanced. The computational fluid dynamics (CFD) numerical simulation is performed on thermal management of the mobile phone using a heat storage unit (HSU) filled with the phase change material (PCM). The chips and HSU are embedded in an epoxy polymer casing. The PCM absorbs the heat dissipation from the chips and stores as latent heat to maintain the chip temperature below the allowable service temperature. Eight cases of simulations are carried out with or without PCM at several power dissipations. The use of PCM in mobile phone has shown to be effective in keeping the chip temperature down to acceptable level for certain duration.

A numerical study of solidification of n-hexadecane based on the enthalpy formulation

A numerical study is described in this paper on the investigation of the solidification of a pure n-hexadecane inside a rectangular enclosure based on an enthalpy formulation of the energy equation. A vertical wall of the enclosure is maintained at a constant temperature below the melting temperature of the n-hexadecane while all other sides are adiabatic. The effects of the cold wall temperature, initial liquid superheat and aspect ratio of the enclosure are studied in terms of the solid fraction and the shape of the solid–liquid phase front. It has been found that a lower wall temperature and a smaller initial liquid superheat result in a larger solid fraction. The solidification process is more affected by the natural convection at the early stage of the solidification than at the later stage. This is inferred by the reduction in the phase front’s slope with time as the temperature in the liquid becomes more uniform. At the early stage of the solidification where natural convection is more dominant in the liquid, a lower wall temperature and a larger liquid superheat result in a larger slope on the phase front, indicating strong natural convection in the liquid. The aspect ratio of the enclosure has some effect on the shape of the phase front, but has only a weak effect on the solid fraction.

Numerical investigation of phase change material-based heat storage unit on cooling of mobile phone

This article presents the cooling of mobile phones using phase change material stored in a heat storage unit (HSU). In this study, the cooling performances of three HSU models at different power levels are examined using numerical simulation. Results show that for the same magnitude of heat source power, the melting start time and charging times can be extended if the heat sources and HSUs are distributed. Dimensional analysis shows that the melt fraction can be plotted against the product of Fourier and Stefan numbers to produce some generalized results for cases with low heat source power. At higher power, the Rayleigh number has to be included to take into account the effect of convection. The article also compares the heat source temperatures between plastic and aluminum enclosures.

Development of a computer‐aided educational tool incorporating MATLAB for engineering measurements

This paper presents the development of a multimedia package to help students in the learning of engineering measurements. The stimulus for developing the computer‐aided educational tool derives from the continuing need for engineers to understand and apply mathematical models in the design of measurement systems. Besides providing fundamental background in the theory of engineering measurements, the main features of the computer‐aided tool include the integration of multimedia with Matlab and Microsoft Excel to allow students to conceptualize the relationship between abstract mathematical models to practical situations. The integration not only provides interactively facilities to engage students in the exploration of signals and measurement system behaviors, but also offers random dynamic quizzes that could automatically change the question parameter and generate the correct answer. The considerations and discussions in this paper may be useful for the advancement of computer‐aided instructional tools in other subject areas.

An educational computer-aided tool for heat exchanger design

This paper presents the development of an educational computer‐aided design tool for the shell and tube heat exchanger. The software integrates the thermo‐hydraulics analysis based on Kern method with the mechanical design based on Tubular Exchanger Manufacturing Association (TEMA) Class “C” standard. The software allows the user to experiment with different design specifications and visualize the solutions in the form of performance data and engineering drawings. Technical drawings on the parts of the heat exchanger, like the shell, tube, front and rear header, tube sheet and baffle plate, are produced by the software to assist the user in appreciating issues relating to practical fabrication and costing. Through the correlation of the thermo‐hydraulic performance, configurations and dimensions with respect to the technical specifications, it is hoped that the user could better appreciate the fundamentals of heat exchanger design.

Engineering courseware on refrigeration cycle simulation

Refrigeration cycles are widely used in the application of diverse type of cooling, including air‐conditioning and refrigeration. In a university engineering curriculum, the study of refrigeration cycles is often an important part of the syllabus in a thermodynamics course. A design engineer in the industry also sometimes needs to simulate the refrigeration cycle to optimize the design of a refrigeration system. With these objectives in mind, a refrigeration simulation software package, REFAID, has been developed for the purpose of teaching and design. The refrigeration simulation software is used as a teaching‐cum‐design aid.

EXPERIMENTAL INVESTIGATIONS ON THE COOLING OF A MOTORCYCLE HELMET WITH PHASE CHANGE MATERIAL

The thermal comfort of motorcycle helmet during hot weather is important as it can affect the physiological and psychological condition of the rider. This paper examines the use of phase change material (PCM) to cool a motorcycle helmet and presents the experimental investigations on the influences of the simulated solar radiation, wind speed, and heat generation rate on the cooling system. The result shows that the PCM-cooled helmet is able to prolong the thermal comfort period compared to a normal helmet. The findings also indicate that the heat generation from the head is the predominant factor that will affect the PCM melting time. Simulated solar radiation and ram-air due to vehicle motion under adiabatic condition can have very little influences on the PCM melting time. The results suggested that the helmet usage time would be influenced by the amount of heat generated from the head. Some major design considerations based on these findings have been included. Although this investigation focuses on the cooling of a motorcyclist helmet, the findings would also be useful for the development of PCM-cooling systems in other applications.

Experimental Testing and Evaluation of Parameters on the Extraction of Water from Air Using Thermoelectric Coolers

An experimental prototype is built to study the application of using the thermoelectric cooler (TEC) to extract water from air for daily consumption. This paper presents the experimental evaluation of parameters that influence the amount of water, which can be collected from condensation of water vapour in the air on the cooled surface. The investigation examines the power supply to the TEC and the air flow over the cold surface on the amount of condensate collected. Over a 3-h period with an average relative humidity of 77 %, the largest amount of water extracted from the air is about 50 mL for a cold surface area of 579.6 cm2. With an average power consumption of 89 W, the prototype produces condensation at 5340 kWh/kL. Although the prototype is currently not cost effective, the usage of TEC is promising as there is ample room for prototype improvement.

Thermal performance of PCM-cooled mobile phone

This paper presents the experimental study of using phase change material (PCM) in the cooling of the mobile phone. It investigates the thermal performance of transient charging and discharging of mobile phone in three different situations; making phone calls frequently, making long duration calls and making occasional calls. The results show that mobile phones are heated up fastest during the long duration usage. Experiments are also conducted to determine the effect of fins and effect of orientation of the mobile phone on its thermal performance.

Experimental study of freezing in a rectangular enclosure

Abstract An experimental investigation into the freezing of n -paraffin solutions in a rectangular enclosure is reported. One vertical side of the enclosure was isothermal while the other walls were adiabatic. Using n -hexadecane and a binary mixture of 50% n -hexadecane and 50% n -octadecane, the effects of aspects ratio and wall temperature on the shape and advancement of the solid-liquid interface and the rate of freezing were investigated. For both the pure material and the binary mixture, heat transfer during freezing for the early stages was conduction-dominated. The effect of natural convection is evident for longer times, with convection currents being confined mainly to the top of the enclosure. However, for enclosures of small aspect ratio, this effect may extend to the bottom of the enclosure. It was also found that the aspect ratio has no effect on the solidification rate. Frozen-mass fractions were found to be greater for the binary mixture as compared to the pure material. For both materials, the freezing rate was greater for lower wall temperatures.