Efficient thermoelectric materials have been extensively investigated for energy harvest and portable refrigeration elements. Their thermal properties are of importance to improve the performance of thermoelectric devices. In the present work, the electrothermal technique is developed to simultaneously measure the specific heat and thermal conductivity of individual thin samples suspended across two heat sinks, resorting to the pulsed direct currents with or without a dc offset. The temperature evolution due to Joule self-heating is recorded and compared with the numerical solutions of transient heat conduction equations using the finite volume method. The thermal conductivity is determined by the steady temperature level and the specific heat by the transient temperature rise or relaxation. This technique is tested by a 10 μm thick platinum wire and the thermal conductivity and specific heat are in good agreement with the literature values. In addition, the influences of thermal radiation and thermal boundary resistance between the sample and heat sinks on the experimental results are discussed. This approach could also be extended to individual nano-sized samples as nanofllms and nanowires.
In this chapter, the general flow equation for compressible flow in a pipeline will be derived from basic principles. Having obtained the general flow equation, the way in which flow efficiency is affected by varying different gas and pipeline parameters will be examined. Different flow regimes in gas transmission systems (i.e., partially turbulent and fully turbulent flow) will be presented. Some of the widely used transmission equations and their applications, advantages, and limitations will be outlined. This will be followed by a discussion of pipes in series, pipeline looping, gas velocity, line packing, pipeline maximum operating pressure, and some pipeline codes. The impact of gas temperature on the flow efficiency and gas temperature profile (i.e., heat transfer from a buried pipeline and Joule-Thompson effects) will be discussed. Finally, some major economic aspects and considerations in the design of gas pipeline systems will be presented.