Replacing ozone-depleting refrigerants

The scientific magazine "Nature" reported that the ozone layer over the Antarctic – an area equivalent to the size of the United States – had been reduced by 50 to 60 per cent during the winter. This discovery led to a unique international drive against ozone layer depletion. The first step was the signing of the Montreal Protocol with the aim of reducing CFC production by 50 per cent and then stopping production completely by 2010. However, depletion of the ozone layer was faster than foreseen.

Chlorine-free alternatives

What are the alternatives? It is obvious that CFC replacements based on HCFC compounds are only temporary solutions, likely in exist for a 10 year period. Instead, refrigerants with no influence on the ozone layer at all will be the long-term solution. Their chemical composition must thus be absolutely free from chlorine. The American Society of Heating, Refrigera­tion and Air Conditioning Engineers (ASHRAСE) recently classified the refrigerant R134a in the category chlorine-free refrigerants: HFCs. Like R12 and R22, R134a is rated in the lowest risk class regarding toxicity and flammability. R134a is primarily a substitute for R12 and R500, and is now an established alternative. Its coefficient of performance is close to – or the same as – that of a circuit process with R12. Sub-cooling is favourable with R134a and plants using, for instance, screw compressors with economizer operation can be converted advantageously from R12 to R134a.

STAL participates in project

The HFC group also includes R32, R125, R143a and R132a. Because of their flammability, most of these substances are not placed in the lowest risk class. Since they are odourless and denser than air, their usage as pure media is also limited but in mixtures (together with R134a, for example) it is possible to achieve suitable alternatives to HCFC. An extensive programme initiated by the Air Conditioning and Refrigeration Institute in the USA, STAL Refrigeration, is being conducted with these mixtures to evaluate possible alternatives to R22 and is participating actively in the European part of that programme.

More mixtures in the future

Mixtures will be much more common than before. This is true also for non-azeotropic mixtures, although it is then necessary to limit the temperature glide in order to avoid changes in the compound, should a leak occur. The use of these mixtures will also re­quire higher technical skill – for example, the HFC media operating with the new lubricating oils are more hygroscopic, which means that it is more difficult to keep moisture out of the systems. Another disadvantage of carbon based refrigerants is that they contribute to global warming when discharged. No limitations for usage have been introduced, but in this respect both users and pro­ducers feel uncertain about the future.

Ammonia for more than 100 years

Ammonia is a traditional refrigerant which has been in use for over 100 years and which does not affect the ozone layer or add to global warming. Ammonia is poi­sonous and – under certain circumstances – explosive. Even so, ammonia has kept its position as the foremost refrigerant in industrial applications thanks to continuous developments of the related safety regulations. Consequently, ammonia plants can today be used without any limits.

Exercise 4. Find the Russian equivalents for the following:

a circuit process, the lowest risk class, toxicity and flammability, lubricating oils, depletion of the ozone layer, to keep moisture, users and pro­ducers, under certain circumstances, the foremost refrigerant, safety regulations, industrial applications, in this respect, sub-cooling.

Exercise 5. Find the English equivalents for the following:

не иметь ограничений, недостаток, высокие технические навыки, оценивать возможные альтернативы, постоянное усовершенствование, чувствовать неопределенность, избегать изменений, вносить вклад, глобальное потепление, благоприятный, преимущественно.

Exercise 6. Complete the sentences using information from the text:

1. Instead,…

2. Even so,…

3. Because of their flammability,…

4. The first step was…

5. This discovery led to…

6. However,…

7. Since they are…

Exercise 7. Fill in the blanks with prepositions about, of, for, out, to, in:

1. Ammonia is a traditional refrigerant which has been … use … over 100 years.

2. This is true also … non-azeotropic mixtures.

3. No limitations … usage have been introduced, but … this respect both users and producers feel uncertain … the future.

4. It is more difficult to keep moisture … … the systems.

5. They contribute … global warming when discharged.

Exercise 8. Say if the sentences are true or false:

1. The use of these mixtures does not re­quire higher technical skill.

2. CFC replacements based on HCFC compounds are only temporary solutions.

3. Ammonia is not poi­sonous and explosive.

4. Mixtures won't be more common than before.

5. Another advantage of car­bon based refrigerants is that they do not contribute to global warming when discharged.

Exercise 9. Find in the text and write down the sentences with Passive Voice, analyze the tense in each sentence.

Exercise 10. Answer the following questions:

1. What did the scientific magazine "Nature" report?

2. What did this discovery lead to?

3. What was the first step to improve the situation?

4. What are the alternatives?

5. What must the refrigerants be absolutely free from?

6. What are disadvantages of the refrigerants of the HFC group?

7. Why will the use of the mixtures require higher technical skill?

8. What are the disadvantages of carbon based refrigerants?

9. What is a traditional refrigerant?

10. What are its disadvantages?

Exercise 11. Discuss with your groupmates the types of the refrigerant used at the modern processing plant.

TEXT 3

Exercise 1. Read and memorize the words from the text below:

avoid, v	избегать, остерегаться
stick, v	липнуть, прилипать
eliminate, v	устранять, исключать
mesh, n	ячейка сети; отверстие
utilize, v	использовать
adherence, n	прилипание; слипание; сцепление
stiff, adj	жёсткий, тугой, негибкий, неэластичный
retention, n	удерживание, сохранение
spray, v	брызгать, распылять; обрызгивать, опрыскивать
load, v	грузить, нагружать
valve, n	клапан; вентиль
mount, v	монтировать, устанавливать

Exercise 2. Read and translate the text.

New pre-freezing technology

By pre-freezing the bottom surface of wet and sticky food products efficiently before they enter the final freezer, the most common problems associated with today's freezing lines can be avoided.

According to AGA, the producing company, its new pre-freezer eliminates problems like belt mesh marks on the products, sticking and bending and, thereby financial losses. The new AGA freezer is reported to be well suited for food products such as fish fillets.

The freezer utilizes a super cold stainless steel belt, on which the fish products are loaded. Heat from the bottom surface is very quickly transferred to the belt and the un­derside freezes instantly. The food portions do not stick to the belt, because the rapid freezing process simultane­ously shrinks the surface. Losses due to adherence to the bell are thereby eliminated. The steel belt provides the food products with a smooth bottom surface free from mesh marks.

In the final spiral freezer, the stiff bottom surface prevents bending. The degree of freezing required for variable-sized food products is controlled by varying the retention time in the freezer.

The patented freezing technique demands a direct contact between the low tempera­ture metal surface and the product. The freezer uses a bath of liquid nitrogen through which the metal conveyor rotates, in addition, nitrogen is sprayed directly onto the bottom side of the con­veyor belt immediately before it reaches the load zone. The control system includes a tem­perature controller operating valve for the nitrogen supply.

According to the manufacturer AGA, special attention has been paid to easy use of the freezer. The side-mounted control panel features clearly defined, easy-to-use switches, an automatic gas-supply controller and a temperature indicator. There is no need for manual control by the operator during the production process. The freezer can easily be opened for cleaning.

Exercise 3. Complete the sentences using information from the text:

1. The new AGA freezer is reported to be…

2. According to the manufacturer…

3. The food portions do not stick to the belt, because…

4. The patented freezing tech­nique demands…

5. The freezer utilizes…

6. The freezer uses a bath of liquid nitrogen through which…

7. The degree of freez­ing required for variable-sized food products is control­led by…

Exercise 4. Say if the sentences are true or false:

1. There is no need for manual control by the operator during the production process.

2. The control system includes a load controller operating valve for the nitrogen supply.

3. The steel bed of rods provides the food products with a smooth bottom surface free from mesh marks.

4. Special attention has been paid to easy use of the freezer.

5. The freezer can hardly be opened for cleaning.

Exercise 5. Answer the following questions:

1. What are the most common problems associated with today's freezing lines?

2. How can they be avoided?

3. What problems does new pre-freezer eliminate?

4. What does this freezer utilize?

5. What does the patented freezing tech­nique demand?

6. What refrigerant does the freezer use?

7. What has special attention been paid to?

Exercise 6. a) Write down a short plan of the text.

b) Speak about a new freezer produced by the company-manufacturer.

TEXT 4

Exercise 1. Read and translate the text with the help of a dictionary.