радмир140
12.03.2023 15:25

HEAT DISTRIBUTION SYSTEMS Heat is distributed through a variety of ways. Steam heating is one of the oldest heating technologies, but the process of boiling and condensing water is less efficient than modern systems and suffers from lag times be- tween the boiler turning on and the heat arriving in the radiators. The first central heating systems used steam distribution because steam moves itself through piping without the use of pumps. Non insulated steam pipes often de- liver unwanted heat. Fiberglass pipe insulation that can withstand the high temperatures of these delivery pipes is very effective. Regular maintenance for steam radiators depends on whether the radiator is a one-pipe system (the pipe that supplies steam also returns condensate) or a two-pipe system (a sep- arate pipe returns condensate). One pipe systems use automatic air vents on each radiator, which bleed air as steam fills the system and then shut auto- matically when steam reaches the vent. A clogged air vent will keep a steam radiator from heating up. Air vents can be cleaned by boiling them in a water and vinegar solution, but usually need to be replaced.
Steam radiators can also warp the floor and their thermal expansion and contraction over time can dig ruts into the floor. These effects can cause the radiator to tilt, preventing water from properly draining from the radiator when it cools and cause banging noises when the radiator is heating up. Shims should be inserted under radiators to pitch them toward the pipe or the steam trap in a two-pipe system. Older steam traps often stick in either the open or closed position, throwing off the balance in the system. The best approach is to replace steam traps in the system. Steam radiators located on ex- terior walls can cause heat loss by radiating heat through the wall to the out- doors. To prevent such heat loss, foil-covered cardboard reflectors should be installed behind these radiators. The foil should face away from the wall, and the reflector should be slightly larger than the radiator. Hot-water radiators are one of the most common heat distribution systems in newer homes. They may be a baseboard-type radiator or of an upright design. The most common problem in hot-water systems is unwanted air in the system. At the start of each heating season it is necessary to go from radiator to radiator and open each bleed valve slightly, then close it when water starts to escape through the valve. To save energy in hot-water systems it is necessary to provide sep- arate zone control for different areas of the building. Automatic valves on the hot water radiators, controlled by programmable thermostats in each zone of the house will allow to heat and cool off portions of the house automatically.

5. Answer the questions.
1. What are the most common heat distribution systems?
2. What are the main disadvantages of steam heating?
3. What does regular maintenance for steam radiators depend on?
4. What can cause heat loss?
5. What is the main problem with hot-water radiators?
6. What are the ways of saving energy in hot-water systems?
7. Which of these systems is more effective from your point of view?

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Damirok21
03.04.2021 10:45

English is a West Germanic language first spoken in early medieval England which eventually became the leading language of international discourse in today's world.[4][5][6] It is named after the Angles, one of the ancient Germanic peoples that migrated to the area of Great Britain that later took their name, England. Both names derive from Anglia, a peninsula on the Baltic Sea. English is most closely related to Frisian and Low Saxon, while its vocabulary has been significantly influenced by other Germanic languages, particularly Old Norse (a North Germanic language), as well as Latin and French.[7][8][9]

English has developed over the course of more than 1,400 years. The earliest forms of English, a group of West Germanic (Ingvaeonic) dialects brought to Great Britain by Anglo-Saxon settlers in the 5th century, are collectively called Old English. Middle English began in the late 11th century with the Norman conquest of England; this was a period in which English was influenced by Old French, in particular through its Old Norman dialect.[10][11] Early Modern English began in the late 15th century with the introduction of the printing press to London, the printing of the King James Bible and the start of the Great Vowel Shift.[12]

Modern English has been spreading around the world since the 17th century by the worldwide influence of the British Empire and the United States. Through all types of printed and electronic media of these countries, English has become the leading language of international discourse and the lingua franca in many regions and professional contexts such as science, navigation and law.[4] Modern English grammar is the result of a gradual change from a typical Indo-European dependent marking pattern, with a rich inflectional morphology and relatively free word order, to a mostly analytic pattern with little inflection, a fairly fixed subject–verb–object word order and a complex syntax.[13] Modern English relies more on auxiliary verbs and word order for the expression of complex tenses, aspect and mood, as well as passive constructions, interrogatives and some negation.

English is the largest language by number of speakers,[14] and the third most-spoken native language in the world, after Standard Chinese and Spanish.[15] It is the most widely learned second language and is either the official language or one of the official languages in almost 60 sovereign states. There are more people who have learned it as a second language than there are native speakers. As of 2005, it was estimated that there were over 2 billion speakers of English.[16] English is the majority native language in the United States, the United Kingdom, Canada, Australia, New Zealand and Ireland, and it is widely spoken in some areas of the Caribbean, Africa and South Asia.[17] It is a co-official language of the United Nations, the European Union and many other world and regional international organisations. It is the most widely spoken Germanic language, accounting for at least 70% of speakers of this Indo-European branch. English speakers are called "Anglophones". Variability among the accents and dialects of English used in different countries and regions—in terms of phonetics and phonology, and sometimes also vocabulary, idioms, grammar, and spelling—does not typically prevent understanding by speakers of other dialects, although mutual unintelligibility can occur at extreme ends of the dialect continuum.

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Wertwer123
25.10.2020 07:57

I hope you are doing well. I was trying to call you yesterday but you didn't answer. Is your phone broken, or have you lost it again? Anyway, I wanted to ask if you could come to my birthday party next Saturday. My birthday was actually two weeks ago, but I couldn't have party then because lots of people were on holiday.

I've invited a few people from our swimming club, as well as my friends from school. Do you think your brother is free that day? Please invite him to come too. The party's at my house and starts at 8 p.m.

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