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Put the verbs given in brackets in the form of Participle I or II.
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1). The capacity (to gain) (Perf. Act.) 2). The energy (to release) (Indef. Pas.) 3). Experiments (to conduct) (Indef. Pas.) 4). The moving parts (to eliminate) (Perf. Pas.) 5). The refrigeration (to generate)) (Indef. Pas.) 6). The friction (to produce) (Perf. Pas.) 7). The velocity (to exceed) (Perf. Pas.) 8). The heat (to reject) (Indef.Pas.) 9). The heat capacities (to achieve) (Perf. Pas.) 10). The features (to specify) (Indef.Pas.).
10. Translate sentences paying attention to Participle II + Infinitive.
1). The heat exchanges expected to be vital elements of all cryocoolers are used in counter-flow or in parallel-flow operation.2). The phenomena supposed to be investigated will be spoken about at the meeting. 3). Much higher pressure ratios estimated to be achieved in a centrifugal compressor at comparable speed are required for such a type of a rotodynamic machine. 4). A single-stage compressor expected to be built and tested will incorporate aerodynamically shaped blades on a 218 mm diameter impeller to achieve high efficiency. 5). Cooling to the motors and bearings thought to be taken place in the compressor is provided by a closed loop refrigeration system. 6). The flow assumed to be one –dimensional and incompressible is considered to be the most important characteristics of the behavior of the machine. 7). The overall performance of the compressor expected to be estimated in this paper is expressed in curves relating pressure ratio, flow rate, speed and efficiency.
11. Translate sentences paying attention to “With + noun +Participle I “ construction.
1). With industrialization going on at its present rate the world’s fuel reserves will be exhausted within the near future. 2). With the regenerative exchanger being installed in the cryocooler, it should be provided with valves to regulate the flow of the working fluid. 3).The temperature of an object being raised, the velocity of electrons increases. 4). The interconversion of heat and work having been demonstrated, it is possible to define a new function called “the internal energy E”. 5). A cylinder of a gasoline engine is like a gun, with the piston taking place of a bullet. 6). The nucleus of an ordinary hydrogen atom consists of one proton, with one electron moving round it. 7). With the thermal energy being used at high temperatures to generate cyclic pressure fluctuations in the closed engine, these fluctuations can produce refrigeration at low temperatures. 8). With an operating life of the device being short it would possible to obtain the low speed, low refrigeration output characteristics of such a type of engines.
Read and translate the Text 3B.
Text 3B. HEAT EXCHANGERS.
Heat exchangers are vital elements of all cryocoolers. Two principal types of heat exchanger are used: (i) recuperative and (ii) regenerative. A recuperative
heat exchanger is a device where separate flow passages are provided for the hot and cold fluids. The fluids are separated by a solid wall and heat is transferred by conduction across the wall. The fluids may flow continuously or periodically.
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A regenerative heat exchanger has a single set of flow passages through which the hot and cold fluids flow alternatively and periodically. The regenerative matrix, often a porous finely divided mass (of metal wire or spheres), may be thought of as a thermodynamic sponge alternatively accepting or rejecting heat as the hot or cold fluid flows through it.
Both types of exchange may be used in counterflow or in parallel-flow operation. In counterflow operation the hot and cold fluids flow in opposite direction. In parallel flow operation the fluids flow in the same direction. Counterflow operation is much more effective than parallel flow operation and should always be used except in special circumstances.
The type of heat exchanger used, either regenerative or recuperative, is a key feature in identifying the particular family of machine. Within this family various machines may be further separated and classified by the thermodynamic cycle on which they operate or by some other feature.
Cryocoolers with regenerative heat exchangers include Solvay and Gifford-McMahon, Stirling, Ericsson, and Vuilleumier engines. Cryocoolers with recuperative heat exchangers include Linde, Hampson, Claude, Collins, and Joule-Thomson engines.
If the specimen cryocooler does include a regenerative exchanger it should be provided with valves to regulate the flow of the working fluid.
Another key feature is the manner in which the flow of working fluid is controlled, namely, by valves or by volume variations. All recuperative engines have valves. Therefore, classification by means of flow regulation is specific to regenerative engines. Here are arbitrary distinction is adopted:
1. Stirling engines where the flow is controlled by volume changes;
2. Ericsson engines where the flow is controlled by valves.
The use of valves for flow regulation has the advantages of increased flexibility in flow control and timing with the possibility of virtually unrestricted pressure ratios (pmax/ pmin). Valves add to the mechanical complexity of the system and provide sources of noise and additional points of wear so the prospect for long life with low maintenance is reduced.
The distinction between engines with and without valves is important and has a profound impact on the design and operation of regenerative machinery.
If the unit does include valves as well as a regenerator it will be an Ericsson, Solvay, Postle and Gifford-McMahon type of engines. The distinction between Solvay unit includes a work-producting low temperature expansion machine. The Postle unit operates with a displacer only.
If the specimen cryocooler contains a regenerative heat exchanger but no valves the next step in classification is the type of device used to achieve a pressure variation.
Stirling engines incorporate a mechanical compressor so the total enclosed volume of the working space varies cyclically as a result of the motion of a piston in cylinder.
In Vuilleumier engines there is no piston but simply a displacer moving working fluid from a hot spacer and vice versa. The machine is said to have a thermal compressor and is sometimes called a thermocompressor. The variation in temperature at constant volume causes a change in pressure, (high when the fluid is in the hot space, low when it is in the cold one.) The change in pressure is utilized in a separate but connected cylinder also containing a displacer to achieve refrigeration. The machine was devised by Rudolph Vuilleumier in 1918.
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Multiple applications for cryogenic cooling system have resulted in the development of many different cryocoolers with different characteristics and attributes.
13. Answer the following questions:
1). What principal types of heat exchangers are used? Give the definition to each of them. 2). Where may these types of exchangers be used? 3). What is the key feature in identifying the particular family of the machine? 4).What kind of engines do cryocoolers of both types include? Name them. 5) What has a profound impact on the design and operation of regenerative machinery?
14. Translate the following words into Russian:
flow passages, volume variation, counterflow, to be provided with, to be specific to, arbitrary distinction, to be controlled by, unrestricted pressure ratios, the prospect for long life, to cause, maintenance, to have a profound impact on, low-temperature expansion, to result in.
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