Solar Hot Water Heating Systems

Today, solar thermal systems are well established worldwide with an enormous potential for energy production and for high contribution to the future green energy system. Solar domestic hot water systems with natural circulation are most favorable in areas with a mean annual sum of global radiation on a horizontal surface above 1800 kWh− 2 year− 1 and with collector areas up to 10 m2. Forced circulation systems for flat-type solar collectors could be useful in colder climates and for large systems. The application of more complex solar collector technologies depends on the possible demands for higher temperature levels. Several examples concern some industrial applications, whose heat demands could now be met through solar energy. In all the cases, the next challenge is to swiftly make cost-effective all such devices and technologies

Eddy Current Detection of the Martensitic Transformation in AISI304 Induced upon Cryogenic Cutting

The combination of a hard subsurface layer and a ductile component core is advantageous for many applications. Steels are often heat treated to create such a hardened subsurface, which is both time- and energy-consuming. It is of great advantage to create a hardened subsurface directly within the machining process, as the production line of most components includes such a process to produce the desired geometric dimensions and surface quality. To achieve a martensitic subsurface layer within the machining process, cryogenic, external turning using a metastable AISI304 austenitic steel is used herein. Herein eddy current testing and the analysis of higher harmonics are used for the detection of the ferromagnetic, martensitic phase in the parent austenite. A good correlation is found between the martensite content and the amplitude of the signals measured. Therefore, eddy current testing is considered as a suitable real-time, nondestructive testing method, which forms the basis for the generation of a tailored, deformation-induced martensitic subsurface layer during external turning