II. Read, translate and retell the text “Solar Water Heater”

Examination Question – Paper № 17

II. Read, translate and retell the text “Earthquake Friction Dampers”.

Examination Question – Paper № 16

Traditional earthquake resistant buildings have relied on ductility to dissipate kinetic energy through large, inelastic deformations such as twisting, cracking and bending. The repair costs for the structure may be as significant as the costs of collapse of the structure and valuable contents, such as instrumentation or electronic records, housed by the building may be lost as a result of the earthquake damage.

Earthquake friction dampers reduce the problems created by dependence on structural ductility by dissipating most of the seismic energy mechanically, independent of the primary structure. This makes the design of damage-free structures economically possible. Unlike traditional concrete shear walls, earthquake friction dampers do not have to be located continuously one on top of the other which allows for greater space-planning flexibility.

Earthquake friction dampers specially treated to develop a reliable level of friction consist of a series of steel plates or sections with slotted holes.They are clamped together with high-strength bolts and allowed to slip at pre-determined loads. Because friction can dissipate a greater amount of energy than yielding steel plates or the use of viscoelastic materials, fewer dampering devices are required to provide the necessary amount of energy dissipation.

Earthquake friction dampers are not susceptible to temperature, velocity, stiffness or degradation due to aging, do not require maintenance and do not have to be replaced after an earthquake. They do not slip during wind storms or moderate earthquakes. When they do slip, the strain energy of the structure brings them back to nearly their original configuration.

Earthquake friction dampers are fabricated from recycled steel, instead of concrete, which reduces the amount of waste generated during the construction process. When they are no longer in use, they can be dismantled and recycled again.

Зав. кафедри ТіППГіРМ М.М. Барков

Water heating accounts for about 20% of residential energy use and 7% of commercial energy use. A solar water heating system can significantly reduce the fossil fuel or electricity required to heat this water.

A solar water heater typically uses glazed collectors that are roof-mounted and connected to a preheat storage tank. Fluid is pumped to the collectors where it is warmed by the sun and returned to a heat exchanger where heat from the fluid is used to heats the water in a preheat storage tank. A backup water heater is installed in series with the preheat tank to maintain the desired water temperature during extended cloudy periods. Most manufacturers offer packaged "residential" systems of two to three solar collectors and associated controls and hardware for small loads. Systems are custom designed for larger commercial and industrial loads. A typical system will provide 50 to 75% of the water heating load. The benefits of this system are obvious: it provides a large proportion of a building's water heating needs at minimal operating cost and it reduces considerably the use of electricity or fossil fuels.

Solar water heaters are best suited to buildings with high hot water loads. Applications include houses with at least four occupants, apartment buildings, industrial processes, restaurants, car washes, laundries and fitness centers. Systems can be easily retrofit to existing buildings although flat roof buildings will require a support rack to angle the collectors towards the sun. Ideally collectors are mounted facing south and sloped at an angle equal to the location latitude. However, orientations of up to 20 degrees off this optimum have little impact on performance..

Solar water heating systems have been used on a wide variety of commercial buildings in Canada. In most cases the systems have performed reliably. Some systems however, have gone out of service or been removed because they were not properly maintained.

Зав. кафедри ТіППГіРМ М.М. Барков

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