K Darkwa

Heat transfer in neuron composite laminated phase-change drywall

Abstract Inadequate heat transfer and overall reduction in thermal conductivities during energy recovery are identified as the main barriers affecting the performance of a phase-change material (PCM) wallboard system. Two integrated PCM drywall systems have been evaluated numerically, and the results showed a great advantage of the laminated PCM wallboard system over the randomly mixed PCM type in terms of enhanced thermal performance and rapid heat transfer rates under a narrow temperature swing. For instance, the maximum instantaneous enhancement in heat flux obtained was between 20 and 50 per cent higher during the phase change process, with up to about 18 per cent more heat storage and release capacity. However, experimental evaluation is required for validation and development.

Thermochemical energy storage in inorganic oxides: An experimental evaluation

A thermochemical energy store using CaO (an inorganic oxide) as the storage material has been evaluated. Analysis of the experimental data showed an average deviation of about 17% and accounted for about 8% uncertainties in the primary data. Given the configuration of the rig and the experimental conditions and errors, the experiment has proved that it is feasible to utilise a fixed-bed thermochemical energy store for preheating an engine coolant during cold starting. However, for practical application purposes, it may be desirable to redesign the reaction bed in order to achieve an optimum mass and heat transfer.

Evaluation of regenerative phase change drywalls: low-energy buildings application

An integrated phase change drywall system has been analytically evaluated for low-energy building applications. The mathematical model indicates that it is possible to attain higher levels of thermal performance and efficiency with lower values of transfer units (NTU). Even though the model does not take into account the variable nature of the thermophysical properties of phase change materials (PCMs), reasonable thermal performance is achievable. Experimental validation is therefore recommended. Copyright

Thermal Analysis of Composite Phase Change Drywall Systems

The main barriers affecting the performance of phase change materials (PCM) wallboard system during energy recovery mode are identified as inadequate heat transfer and overall reduction in thermal conductivities. In order to assess the extent of these barriers, two integrated PCM drywall systems (i.e., randomly mixed and laminated PCM systems) have been evaluated numerically. The results showed a great advantage of the laminated PCM-wallboard system over the randomly mixed PCM type in terms of enhanced thermal performance and rapid heat transfer rates under narrow temperature swing. For instance, the maximum instantaneous enhancement in heat flux obtained was between 20% and 50% higher during the phase change process and up to about 18% more heat storage and release capacity. Experimental evaluation is, however, required towards validation and development of the laminated system.

Green transport technology (GTT): analytical studies of a thermochemical store for minimising energy consumption and air pollution from automobile engines

An analytical evaluation of a thermochemical store using inorganic oxides as the storage material has been carried out. The possibility of using this device as a thermal store for minimising energy consumption and pollutants simultaneously from automobile engines during cold starting exists. Sources of heat from the exhaust and the cooling circuit are identified as potential energy input for regenerating the store. However, the viability of this device depends on addressing issues such as the life cycle of the storage material and the bed configuration of the store. Experimental validation is therefore needed.

Mathematical modelling of a thermochemical energy store: Automobile application

Abstract An analytical evaluation of a thermochemical store for minimizing energy consumption and pollutants simultaneously from automobile engines has been carried out. The analysis of the model indicates a possibility of achieving a working temperature of a typical 2 litre petrol engine within 4 minutes. However, the viability of the model depends on addressing issues such as the life cycle of the storage material and the bed configuration of the store. Experimental validation is therefore recommended.

THERMAL ASSESSMENT OF INTEGRATED PHASE CHANGE DRYWALL SYSTEMS

Experimental evaluations of manufactured samples of laminated and randomly-mixed phase change material (PCM) drywalls have been carried out and compared with numerical results. The analysis showed that the laminated PCM drywall performed thermally better. Even though there was a maximum 3% deviation of the average experimental result from the numerical values, the laminated PCM board achieved about 55% of the phase change process as against 48% for the randomly distributed drywall sample. The laminated board sample also released about 31 % more latent heat than the randomly distributed type within the optimised time thus validating previous simulation study. Given the experimental conditions and assumptions the experiment has proved that it is feasible to develop the laminated PCM technique for enhancing and minimising multi-dimensional heat transfers in drywall systems. Further practical developments are however encouraged to improve the overall level of heat transfer.