Inhalation properties of a pump involve the ability to create suction vacuum and meet the Net Positive Suction Head (NPSH) requirements. The boiling point of water at standard atmospheric pressure is 100°C. When water reaches this temperature, it begins to vaporize, forming numerous bubbles and turning into steam. At high altitudes, where atmospheric pressure is lower, water can boil at temperatures below 100°C. This shows that water vaporization depends not only on temperature but also on the atmospheric pressure above the liquid surface. If the pressure is reduced sufficiently, water can even vaporize at room temperature.
From the working principle of a centrifugal pump, we understand that its ability to draw liquid from a lower source is due to the centrifugal force created by the rotating impeller, which generates a relative vacuum at the pump inlet. This vacuum allows the atmospheric pressure on the surface of the liquid reservoir to push the liquid up through the suction pipe toward the impeller center. Normally, atmospheric pressure is equivalent to about 10.3 meters of water column (assuming sea level with zero elevation). If the impeller center were a perfect vacuum and there were no head losses in the suction piping, the atmospheric pressure could only lift water up to 10.3 meters. Therefore, the maximum suction height of a pump is limited.
As the pump’s installation height increases, the required suction vacuum at the inlet becomes greater, meaning the pressure at the impeller inlet must be lower to draw in the liquid. However, when the pressure at the pump inlet drops to the vapor pressure of the liquid at its current temperature, the liquid starts to vaporize, forming bubbles within the flow. These bubbles, filled with vapor and gases that have separated from the liquid, are carried into the impeller along with the fluid.
As the liquid moves through the impeller, the pressure increases due to centrifugal force, causing the vapor inside the bubbles to condense rapidly. The bubbles collapse almost instantly, and the surrounding liquid rushes in to fill the void. This rapid collapse creates a strong hydraulic shock, known as cavitation. The resulting pressure spikes can reach up to 10 to 30 MPa locally. Over time, if these air bubbles remain attached to the impeller blades, they can cause severe damage under repeated water hammer impacts.
In practice, cavitation often leads to honeycomb-like pitting on the backside of the impeller blade near the inlet. Because of this, pumps should never operate under cavitation conditions, as it significantly reduces efficiency and can lead to mechanical failure.
Aluminum doors are doors with aluminum alloy as the frame and inlaid glass. The following is its relevant introduction:
1. Structural composition
Aluminum alloy frame
The aluminum alloy frame provides a stable support structure for aluminum doors. Aluminum alloy has the advantages of high strength, light weight, and corrosion resistance. Its profiles can be made into various shapes and sizes according to different design requirements, such as common squares, rectangles, etc., and can be anodized, powder sprayed and other surface treatments to achieve beautiful and durable effects.
Glass part
Glass is an important part of aluminum doors, with functions such as lighting and transparent vision. According to different needs, ordinary transparent glass, frosted glass, tempered glass, hollow glass, etc. can be selected.
Ordinary transparent glass has good light transmittance, but its safety and heat insulation and sound insulation performance are relatively poor. Frosted glass can protect privacy to a certain extent and is suitable for places with certain privacy requirements, such as bathrooms. Tempered glass has high strength, blunt-angle particles after breaking, good safety, and is often used in public places or places with high safety requirements. Hollow glass has better heat insulation and sound insulation performance, and is suitable for places where the indoor environment needs to be kept comfortable.
2. Types
Sliding aluminum door
This type of door uses tracks and pulleys to push and pull the door leaf left and right. Its advantages are space saving and easy operation. It is suitable for places with small space or not suitable for swing door opening, such as partitions between balconies and indoor areas, entrances and exits of small shops, etc. However, the sealing performance of sliding aluminum doors is relatively weak, and it may not be as good as swing doors in terms of sound insulation, heat insulation and preventing dust from entering.
Swing aluminum door
Swing aluminum doors are connected by hinges and can be opened inward or outward. It has good sealing performance and can effectively block dust, rain, noise, etc. from the outside. The safety of swing doors is also high, and they are suitable as entrance doors for residential buildings or partition doors between indoor rooms. However, swing aluminum doors need to occupy a certain space when opened, and have certain requirements for the surrounding space.
3.Advantages
Aesthetics: The transparency of the glass of the aluminum glass door can make the space appear more open and bright, and has a high decorative value.
Strong and durable: The aluminum alloy material has high strength and is not easy to deform, which can ensure the long-term use of the door.
Good sealing: The aluminum glass door can effectively block the dust, noise and temperature changes from the outside.
Corrosion resistance: The aluminum glass door can adapt to different environmental conditions and is not easy to rust.
In commercial places such as shopping malls and office buildings, aluminum glass doors are often used in storefronts, office partitions, etc.; in homes, they are also commonly seen in areas such as balcony doors and kitchen doors.
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