Engineering materials humidity

Variation of composition and stracture have made it possible to engineer materials with specific properties, and this has led to the development of many perovskite ceramic sensors for example, BaHOs has a large positive temperature coefficient and is used as a current limiter or as a temperature measuring device BaTiOs + BaSnOs, known as BTS, has been developed into fast, stable, and sensitive detector systems for temperature change, relative humidity meters, and the detection of small amounts of organic gases as the decrease in resistance of the system is monitored. The effectiveness of BTS sensors depends upon development of three types of pore system within the material micropores < 2 nm, mesopores 2-5 nm. 

FIGURE 4.3 Creep rupture of PVC at 20°C, 50% relative humidity. (From Engineering Materials Handbook, Volume 2, Engineering Plastics, ASM International, 1988, Figure 25, p. 671. Reprinted with permission of ASM International.)... 

Low-carbon and chromium-nickel steels, certain copper, nickel and aluminium alloys (which are all widely used in marine and offshore engineering) are liable to exhibit stress-corrosion cracking whilst in service in specific environments, where combinations of perhaps relatively modest stress levels in material exposed to environments which are wet, damp or humid, and in the presence of certain gases or ions such as oxygen, chlorides, nitrates, hydroxides, chromates, nitrates, sulphides, sulphates, etc. 

Polyphenyldiethylsiloxane varnishes are solutions of phenyldiethylsi-loxane polymer in petrol, toluene or a mixture of petrol and turpentine. They are liquids ranging in colour from yellow to brown. The varnishes are heat-resistant they are used to produce insulating materials for temperatures up to 180 °C and high humidity. Heat-resistant insulation of polyphenyldiethylsiloxane varnishes is widely used in electric engines, in rotors of turbogenerators, etc. 

Desiccant dehumidifiers reduce humidity in the air by using solid desiccant materials or liquid desiccant materials to attract and hold moisture. They can operate independent of chillers and can also be operated in series or parallel with chillers. Recoverable heat from the exhaust gases of turbines and engines for power generation or engine-driven chillers is used for regenerating desiccant material in these dehumidifiers. 

At the production lines for rubber profile extrusion as installed at the industrial partners site, most process values were already available from automatic control. Yet, these values were only available for direct display, but not recorded in any way. This is partially due to the fact that production lines in this domain usually run without major changes for several decades. Some important process values, e.g., the power consumption of the extruder engines, were not measured at all. Thus, a first important step of the project was the integration and recording of these values. Appropriate hard- and software had to be installed. Additionally, environmental conditions with possible influence on the properties of the raw materials and thus the process behavior had to be recorded, e.g., temperature, humidity and pressure. 

The final engineering tests with the civilian mask offered some interesting problems which had not been encountered before. Prior to this test no item of like materials and like construction had been subjected to such severe environmental conditions at Dugway Proving Ground. The tests consisted of storing the masks for 9 weeks in chambers at —65°F. (arctic), +165°F. (desert), and -fll3°F. and maximum humidity (tropic). In addition, masks were stored for 3 weeks under each of these climatic conditions in succession (cyclic). Upon completion of this surveillance, the masks were compared with controls as to physical condition, gas life, and aerosol penetration. 

ANL has constructed a tribology test rig that operates at the speed and interface pressure of the TIVM compressor/expander vanes at full power. This test rig is depicted in Figure 2. Initial dry friction and wear tests with stainless steel and low friction engineered polymer samples provided by Mechanology have indicated an acceptable friction coefficient at the TIVM operating conditions and wear rate consistent with the lifetime requirement. Additional tests are being conducted with high humidity and different material combinations. 

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