Kinds Of Insulation Systems Research Articles

Improvement of polyurethane thermal insulation materials by using corn stalk

The heat loss during the heating of buildings constitutes about 40% of the greenhouse gas emission that causes global warming. Thus, in order to decrease the energy for heating buildings, various kinds of insulation systems and materials have been used. In this study, by using corn stalks, a polyurethane insulation material was produced. The unit weight, ultrasonic pulse velocity and thermal conductivity coefficients of the produced material were determined. The thermal conductivity coefficient of this composite material was found to be 0.042. The insulation values obtained were in an acceptable range, i.e. they satisfy the Turkish Standard TS 805 EN 60155. Thus, with the zero-waste objective, this study presents an alternative construction material containing a certain type of waste material, also avoiding the environmental problems it causes.

Analysis of the coupled effect of steel studs and surface emissivity on internal insulation systems performance

Many kinds of insulation systems have been developed and applied over the years to all the constructive elements of the building, but the two most used strategies remain the external and internal insulation of vertical walls. However, about the latter often a significant issue is neglected: the overestimation of the thermal performance by disregarding the contribution of construction elements. Usually a uniform stratigraphy of the wall is considered and the evaluation of the performance of a non-uniform one leads to erroneous results about the overall behavior of the system. In this paper, we developed a different approach considering the presence of the steel studs used to attach this package to the existing wall and their influence on the thermal behavior of the structure. Through both experimental and numerical analysis, the possible application of low-e sheets inside the air cavity in various configurations and with different thicknesses of insulation is also taken into account. Results showed that neglecting the presence of the steel studs leads to an erroneous evaluation of the conductance of the refurbished wall with errors reaching up to 28.0% in low-e high-insulated cases. This work highlights how careful the designers have to be when using standard formulas to compute the thermal resistance of internal insulation wall systems.

Space charge characteristics of LDPE nanocomposite/LDPE insulation system

Two kinds of insulation systems with nanocomposite have been fabricated by co-pressing low-density polyethylene (LDPE) and nano-titania doped LDPE (TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -LDPE) films. The three-layer systems considered are TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -LDPE/LDPE/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -LDPE (namely, NLN) and LDPE/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -LDPE/LDPE (namely, LNL). Space charge distributions under different applied electric fields were measured by the pulsed electro acoustic (PEA) method. The charge transport characteristics and the interface space charge formation as well as the effect of nano-TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> concentration have been systematically discussed. The results show that heterocharges and homocharges are formed at the LDPE/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> -LDPE polymer interfaces in the system NLN and LNL, respectively. The nature of the interfacial charge has been explained in term of the interfacial polarization theory combined with conductivity and permittivity of the materials. Additionally, the recombination between charges influences the amount of the interface space charge. However, the NLN system always stores more charges than LNL, which was explained by the change of the effective electric field caused by the formation of the interface space charges. The results obtained would provide experimental support for optimizing high voltage direct current power cables.

Mechanical Degradation of High Voltage Rotating Machine Insulation

Several kinds of insulation systems, which were developed for high voltage coil insulation for motors and generators, are examined for insulation damage caused by mechanical stresses. Tests have been carried out on electrical properties under bending stress, i. e. the critical deformation characteristics which are defined as the maximum deformations able to withstand a fixed proof voltage, the fatigue characteristics under repeated bending stresses, and the voltage life characteristics under bending stress. Breakdown voltage, BDV, decreases with an increase of bending stress. Moreover, a remarkable increase of the base tan6 value, tan6o, and tan6 tip-up can be seen due to the delamination of mica-splittings, especially in the case of the insulation using mica splitting. An insulation system in which a flexible binder is used has a far greater critical deformation. The decrease of residual breakdown voltage RBDV, and the increase of tan6o and tan6 tip-up are seen at less repeated bending stress in the insulation system with mica-splitting tapes than in the insulation system with only mica-paper, because of the weakness of mica-splittings under repeated bending stress. Effects of the temperature on the repeated bending fatigue characteristics from -55 to 1550C are greatly influenced by the binder of the mica tape and/or the impregnating resin. Moreover, voltage life under a static bending stress becomes extremely short beyond a certain stress. Lastly, experimental equations are proposed for estimating the relationship between RBDV and the numbers of repeated bending cycles, and the voltage life under a static bending stress.