Refrigerants

III. Put in the correct forms of the Infinitive. Translate sentences into Ukrainian.

1. The storage temperature ought (keep) as constant as possible; it is therefore necessary (adjust) this temperature precisely and reliably.

2. Each object in nature has a particular temperature which can (compare) with the tempera ture of other objects.

3. Sun has started (use) also (heat) dwellings.

4. Heat is a form of energy and may (measure) in the units in which energy is measured.

5. Valves are used (regulate) the flow of fluids in piping systems and machinery.

6. (avoid) leakage, the motor and compressor are often enclosed in the same housing.

7. Refrigeration is sometimes used (freeze) soil (facilitate) excavations.

8. The first generation computers were slow compared to modern machines and, owing to their bulk, they required data (bring) to them.

9. The ancient mathematical tables was difficult (read).

10.The teacher wanted the program (write) in Basic.

11.He seems (learn) all the rules.

12.New method of investigation must (introduce) in the laboratories.

Read and translate the text:

Generally speaking, a refrigerant is any body or substance which acts as a cooling agent by absorbing heat from another body оr substance. With regard to the vapor-compression cycle, the refrigerant is the working fluid of the cycle which alternately vaporizes and condenses as it absorbs and gives off heat, respectively. To be suitable for use as a refrigerant in the vapor-compression cycle, a fluid should possess certain chemical, physical, and thermo-dynamic properties that make it both safe and economical to use.

It should be recognized at the onset that there is no "ideal" refrigerant and that, because of the wide differences in the conditions and requirements of the various applications, there is no one refrigerant that is universally suitable for all applications. Hence, a refrigerant approaches the "ideal" only to the extent that its properties meet the conditions and requirements of the application for which it is to be used.

Ordinarily, the safe properties of the refrigerant are the prime consideration in the selection of a refrigerant. It is for this reason that some fluids which otherwise are highly desirable as refrigerants, find only limited use as such. The more prominent of these are ammonia and some of the straight hydrocarbons.

To be suitable for use as a refrigerant, a fluid should be chemically inert to the extent that it is nonflammable, nonexplosive, and nontoxic both in the pure state and when mixed in any proportion with air. Too, the fluid should not react unfavorably with the lubricating oil or with any material normally used in the construction of refrigerating equipment. Nor should it react unfavorably with moisture which despite stringent precautions is usually present at least to some degree in all refrigerating systems. Futhermore, it is desirable that the fluid be of such a nature that it will not contaminate in any way foodstuff or other stored products in the event that a leak develops in the system.

I. Answer the questions:

1. What is a refrigerant?

2. What properties should a fluid possess to be used as a refrigerant?

3. Is there a universally suitable refrigerant?

4. What are the requirements to safe refrigerants?

5. Can you name the comparatively safe refrigerants?

Дата добавления: 2014-12-29