The use of insulation materials is considered as one of the most effective means of conserving energy in various fields. Thermal insulation materials enable systems to achieve energy efficiency. Many different thermal insulation materials have been developed to reduce heat flow by limiting conduction, convection, and/or radiation while performing one or more functions. These functions may vary in the context of thermal design, numerical simulations, and a wide range of engineering problems, such as determining the heat loss, temperature field, isolation, and cooling conservation, and in a variety of other technologies. One of the most effective ways to identify and determine performance is effective thermal conductivity. The thermal measurement performance is usually evaluated in a temperature and signal gradient for single or combined homogeneous/heterogenous materials. The two main categories of thermal conductivity measurement techniques are steady-state methods and transient methods. The aim of this chapter is to present various measurement methods and to investigate their suitability for method purposes. This chapter presents new and accurate experimental techniques and methods for measuring the thermal conductivity of several most commonly used insulation materials. Some of these methods are commonly used in the field for measuring the thermal property of insulation materials. On the other hand, different insulation measurement practices are presented depending upon the overall structures. The analysis predicting the thermal conductivities of insulation materials is also discussed.
In this study, the potential use and effectiveness of paraffin wax in solar cooker during the daylight and/or late evening hours is experimentally investigated. For these experiments, a box-type solar cooker was constructed by filling paraffin wax with metal shavings. The side- and sub-surface temperatures of the paraffin wax in the cooker are continuously measured during June and July 2011. The effect of the reflector angle on the thermal efficiency of the cooker is tested with different isolation conditions on different days. In conclusion, the designed cooker can be effectively used at an angle of 30°. The thermal efficiency is increased to around 18.35% with the reflector. The maximum temperature of the paraffin achieved during the experiments is in the range of 75.1 °C to 80.5 °C. The reflected radiation makes a maximum contribution of 13.29% to the temperature of the paraffin wax. In addition, the heating time is decreased to approximately 1 h. So, the paraffin wax could be used as a phase change material integrated with the solar system. The rectangular solar cooker filled with the paraffin wax has a high thermal performance, which is indicated by high temperatures and decreased cooking times, for the given design conditions.
SUMMARYIn this study, a theoretical approach is proposed for the prediction of time and temperature during the heat charge and discharge in the latent heat storage of phase changed materials (PCM). By the use of the average values of the mean specific heat capacities for the phase-changed materials, analytical solutions are obtained and compared with the available experimental data in the literature. It is shown that decreasing the entry temperature of the working fluid from À4 to À158C has a very dominant and strong effect on the PCM solidification time. The effect of the working fluid flow rate and the material of PCM capsules on the time for complete solidification and total charging is also investigated. The agreement between the present theoretical model results and the experimental data related to the cooling using small spheres and the heat storage using rectangle containers is very good. The largest difference between the present results and the experimental data becomes about 10% when the fluid temperature approaches the phase change temperature at high temperatures.
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