Read text A. Pay attention to the words in bold type

Translate the sentences. Pay attention to the words in italics.

Efficient p. getter p. property condensate

Dust force p. prevent vapor

Dissolve fluid dynamics positive valve

Diffusion p. fan portable technique

Cryopump exhaust piston pump transfer p.

Cost-effective exert outlet stall

Contract evacuate momentum seal

Container equalize jet saturate

Absorb entrapment inlet rotary p.

Admission enclose ion pump regenerate

Words to be remembered.

1.Pumps differ in details like pressure, tolerance to dust, admission or no admission of oils vapor.

2.Metal contracts as it becomes cool.

3.They discovered that it was more cost-effective to import the pumps from Russia than to manufacture them in Belarus.

4.Sugar dissolves in water.

5.The car raised a cloud of dust as it went down the dirt road.

6.A cryo-pump is a vacuum pump that traps gases and vapors by condensing them on a cold surface.

7.She couldn’t open the door, even by exerting all her strength.

8. The garden is enclosed by a high wall.

9.The firemen directed jets of water at the burning building.

10.As the rock rolled down the mountainside, it gathered momentum.

11. Unless we get more funding we’ll be prevented from finishing our experimental program.

12. This creature’s tail will regenerate if it is cut off.

13.We were caught in the rain and came home saturated.

14.An inexperienced pilot can easily stall his plane.

15.The valves of the heart and blood vessels allow the blood to pass in one direction only.

A. What is a Vacuum Pump?

Vacuum pump is a device for reducing the pressure of a gas in a vessel by removing the gas. The German scientist Otto von Guericke was the first to demonstrate the properties of vacuums in a practical way by his well-known “Magdeburg Experiment” in 1654. The scientist joined two small copper hemispheres (i.e., 20 inches [51 cm] in diameter) in an enclosed space. Then he pumped the air out of that enclosure and rigged a team of eight horses together to attempt to separate the hemispheres. The horses could not pull them apart. Once air was allowed back into the container the spheres were easily moved apart. Thus the power of the vacuum was realized. The scientist’s first pumps were inverted pumps (for fire fighting) and could evacuate larger volumes of air than could be done using static methods.

In 1643 Torricelli demonstrated the mercury barometer based on the water manometer of Berti (~1640). In 1662 Boyle formulated Boyle’s Law, Law of Partial Pressures.

Piston-type Vacuum pumps came into widespread use, but vacuum experiments had to be continued – the seals available at that time were poor.

The vacuum pump was originally invented to help chemists to study the properties of gases and the newly discovered phenomenon called electricity. The history of progress in the study of vacuum is the history of vacuum-pump design. Before 1900, vacuum pumps were produced by crude, hand-operated pumps. In the 20th century the rotary oil pump, the molecular pump, the vapor condensation pump, and the oil diffusion pump were developed. These pumps made a high vacuum possible. With modern techniques all but one of every million molecules in a container can be removed. Pressure can be reduced to 0.00000000001 millimeter of mercury as compared to normal atmospheric pressure of 760 millimeters. Thus, efficient pumps can reduce the pressure of the gas to between 100 and 0.1 pascal

The air of our atmosphere exerts great pressure to enter an enclosed space, which is under high vacuum. It attempts to equalize pressure inside and outside. Dissolved gas molecules diffuse through solids and enter the evacuated space. Slow evaporation of solid materials, such as the container walls, also takes place. When molecules evaporate into a container as fast as other molecules are removed from it, a practical limit is reached, preventing a perfect vacuum.A pump is the device that expends energy to raise, transport, or compress fluids-liquids and gases.

Perhaps the best-known pump is the human heart. Blood enters the heart through a set of one-way inlet valves. As the fluid container – the heart contracts, pressure is increased and the blood is forced into the arteries through one-way outlet valves. In machines, only the fluid is compressed, rather than contracting the whole container. A vacuum pump removes air from a container to create a vacuum. Force pumps of many types are used for vacuum pumps including rotary pumps and piston pumps. In the 21^st century the vacuum pump has become a major necessity for the progressive lifestyle.

Comprehension Check – 1

Дата добавления: 2014-12-26