_Toefl Skill 15_

Skill 15:

 Previous problem/Skill: Problem/skill with Parallel Structure with coordinate connector (Skill 14)

The paired conjunctions both …… and, either …… or; neither …… nor; and not only ….. but also require parallel structures.

The lecture was both informative and enjoyable

Either the history exam or the physics exam is on Tuesday.

The missing papers are neither on his desk nor in the file

He visited not only his cousin but also his grandmother.

The following is not parallel and must be corrected:

They want either to play tennis or golf*.

It is not correct because to play tennis is not parallel to golf It can be corrected in different ways.

They want either to play tennis or to play golf

They want to play either tennis or golf.

When you are using these paired conjunctions, be sure that the correct parts are used together. The following are incorrect:

He lent me both some paper or a pencil

Either breakfast nor* lunch is included in the price.

These sentences are incorrect because the wrong parts of the paired conjunctions are used together. In the first example, and should be used with both. In the second example, or should be used with either.

EXERCISE 15: Each of the following sentences contains words or groups of words that should be parallel.Circle the word or words that indicate that the sentence should have parallel parts. Underline the parts that should be parallel. Then indicate if the sentences are correct (C) or incorrect (I).

1. He either lied or telling an unbelievable story. (I)

    Analysis:

§  either ......or..... (correct), but

§  before and after OR  should have the same structure: telling should be told.

2. The music at the concert was neither well played nor well liked. (C)

     Analysis:

§  neither ......nor...(correct). well played and well liked have same struture, too. So it is correct.

3. He regularly studies both in the morning or in the evening. (I)

    Analysis:

§  both......or ......(incorrect). it should be both.....and.....

4. The play that we saw last night was not only rather delightful but also quite meaningful. (I)

    Analysis:

§  not only .............but also.....(correct)

5. He married her neither for her ability to cook nor her ability to clean house. (C)

    Analysis:

§  neither .............nor....(Correct)

6. The discussion was both exciting and interest. (I)

    Analysis:

§  both ............and.......(Correct), but 

§  before  and after and should have same structure. Exciting is adjective, but interest is noun.  Interestshould be interesting.

7. He withdrew all the money not only from the checking account but also from the savings account. (C)

    Analysis:

§  ..not only ...but also...(correct)

8. Neither the teacher or the students are ready to leave the classroom. (I)

    Analysis:

§  Neither.....or...(Incorrect). It should be Neither .....nor.

9. You can meet with me either in the next few minutes or at 4:00. (C)

     Analysis:

§  either.....or...(correct)

10. John is an adventurous person who enjoys not only skydiving but also goes parasailing. (C)

      Analysis:

§  ...not only....but also...(correct)

Next: Do TOEFL Exercise ( Skill 14 and  Skill 15 ), and

Keterampilan 15:

 Sebelumnya masalah / Keterampilan: Masalah / keterampilan dengan Struktur Paralel dengan koordinat konektor (Keterampilan 14)

Kata sambung dipasangkan baik dan, ...... salah satu atau ......, tidak ...... atau, dan tidak hanya ..... tetapi juga membutuhkan struktur paralel.

Kuliah adalah kedua informatif dan menyenangkan

Entah ujian sejarah atau ujian fisika pada hari Selasa.

Koran-koran yang tidak hilang di mejanya atau di file

Dia tidak hanya mengunjungi sepupunya tetapi juga neneknya.

Berikut ini tidak sejajar dan harus dikoreksi:

Mereka ingin baik untuk bermain tenis atau golf *.

Hal ini tidak benar karena untuk bermain tenis tidak sejajar dengan golf Hal ini dapat diperbaiki dengan cara yang berbeda.

Mereka ingin baik untuk bermain tenis atau bermain golf

Mereka ingin bermain baik tenis atau golf.

Bila Anda menggunakan konjungsi berpasangan, pastikan bahwa bagian yang benar digunakan bersama-sama. Berikut ini adalah salah:

Dia meminjami saya baik beberapa kertas atau pensil

Entah sarapan makan siang atau * sudah termasuk dalam harga.

Ini kalimat yang tidak benar karena bagian-bagian yang salah dari konjungsi dipasangkan digunakan bersama-sama. Pada contoh pertama, dan harus digunakan dengan baik. Pada contoh kedua, atau harus digunakan dengan baik.

LATIHAN 15: Setiap kalimat berikut mengandung kata-kata atau kelompok kata yang harus parallel.Circle kata atau kata-kata yang menunjukkan bahwa kalimat harus memiliki bagian-bagian paralel. Garis bawahi bagian-bagian yang harus sejajar. Kemudian menunjukkan jika kalimat yang benar (C) atau salah (I).

1. Dia baik berbohong atau mengatakan sebuah cerita yang luar biasa. (I)

    Analisis:

 baik ...... atau ..... (Benar), namun

 sebelum dan sesudah ATAU harus memiliki struktur yang sama: mengatakan harus diberitahu.

2. Musik di konser itu tidak baik bermain atau disukai. (C)

     Analisis:

 tidak ...... atau ... (yang benar). juga dimainkan dan disukai memiliki struture yang sama, juga. Jadi sudah benar.

3. Dia secara teratur mempelajari baik di pagi hari atau di malam hari. (I)

    Analisis:

 baik ...... atau ...... (salah). itu harus baik ..... dan .....

4. Drama yang kita lihat tadi malam itu tidak hanya lebih menyenangkan tapi juga cukup bermakna. (I)

    Analisis:

 tidak hanya ............. tetapi juga ..... (yang benar)

5. Dia menikahinya tidak karena kemampuannya untuk memasak atau kemampuannya untuk membersihkan rumah. (C)

    Analisis:

 tidak ............. atau .... (Benar)

6. Diskusi adalah baik menarik dan bunga. (I)

    Analisis:

 baik ............ dan (benar), namun .......

 sebelum dan sesudah dan harus memiliki struktur yang sama. Menarik adalah kata sifat, tapi bunga adalah kata benda. Interestshould menjadi menarik.

7. Dia menarik semua uang tidak hanya dari rekening giro tetapi juga dari rekening tabungan. (C)

    Analisis:

 .. tidak hanya ... tetapi juga ... (yang benar)

8. Baik guru atau siswa siap untuk meninggalkan kelas. (I)

    Analisis:

 Baik ..... atau ... (salah). Harus Baik ..... atau.

9. Anda dapat bertemu dengan saya baik dalam beberapa menit berikutnya atau pada 4:00. (C)

     Analisis:

 baik ..... atau ... (yang benar)

10. John adalah orang petualang yang menikmati skydiving tidak hanya tetapi juga pergi parasailing. (C)

      Analisis:

 ... tidak hanya .... tetapi juga ... (yang benar)

Next: Do TOEFL Latihan (14 Keterampilan dan Skill 15), dan

_Packaged units_

Packaged units

13.1 INTRODUCTION

                Factory-built selt-contained systems are very familiar in the form of domestic  appliance, and retail units such as vending machines, drinking water chillers and display cabinets and counters. Although larger systems may need to be finally assembled in situ, groups of components can be conveniently delivered as pre-assamled units, and it is the exeption for a system to be costum built from individual components, exept in the case of large industrial installation.

                The main benefit of packaging is reduction in cost because a high proportion of the total cost of a refrigerationor air-conditioning system is made up of work which can be carried more quicly, efficiently and under better control within a factory  rather  than on the installation site. There are other advantages as well including.

1.      Correct selection and balance of components

2.      Factory control of system cleanliness , leak tightness, and in some cases, charging

3.      Inspection and testing of the complete unit before it leaves the factory

4.      Delivery to the site complete and in working order , so avoiding site dilays for materials

Simplified site installation, with a minimum of disruption,  inconvenience and cost.

    A possible disadventage is that the size range of available packages may be limited, but bespoke packaged are frequently possible. There is a risk of misapplication , and care should be taken understand the funtionality of the packaged and it is limitations. Comprehensive application data is normally available for or marketed packaged unit to allow designer or sales engineers to make the correct selection for their purposes. Error in application stem mainly from a lack of understending of the requirement and a tedency to purchase at the lowest price without the protection of a clear sfecification. Once the application is fully understood , assessed , and sfecified the possibility of error is reduced.

    Tranport application use specialized systems, and these are covered in chapter 17, as are refrigerated display cabinets. Heat pump units are in chapter 27.

13.2 CONDENCING UNITS

A condencing unit is single package comprising the compressor, the condencerreither air-or water-cooled) mounted on the a base plate or frame. And all connecting piping. Together with the becessary wiring and control to make the set fungtional (figure 13.1) condencing units generally  include a liquid receiver and are ready for site connection to an evaporator. Accsessories such as pressure cut-out switches, liquid line drier, sight glass and fan speed control may be included, and the specification should be cerefully checked. They are built in sizes from less than a kilowatt to more then 100 kw cooling capacity and may incorporate more than one compressor. Air-cooled types may have two or more fans. Sometimes

Figure 13.1 air-cooled condensing unit, 2-cyl semi-hermatic compressor, suitable for several refrigerants (bitzer)

Figure 13.2 outdoor air-cooled condencing unit, scroll compressor, suitable for several refrogerants(emerson climate technologies)

The condenser is separate in which case the packaged part is termed a compressor unit. Units intended for outdoor application have weatherproof housing may be suitable for either wall or floor mounting (figure13.2) .

                The condensor is matched to the compressor, and cooling capacity data refer to air or water temperature onto the condenser  as detailed in chapter 6. Since compressor and condensing unit do not include and evaporator, they are not complete system and are not charged with refrigerant, but have holding charge of dry nitrogen , or a little of the refrigerant gas to maintain a slight positive pressure for transit. Suction and liquid interconnecting  lines and electrical connection is installed on site. Ratings for condencing  unit refer to entering temperature of the condencing medium –air or water ; traditionally presented  as curves (figure 13.3)

Figure 13.3  typical condencing unit rating curves .

And now most commonlly found from manufacture ‘ computer selection programmes. The standatrd condition for rating condencing unit are given in european standard EN 13215, 2000. An estimate of condencing unit capacity at an ambient condition different to the one provided can be made graphically as indicated in cahapter 10.

                Some manufacturers of air-cooled condencing unit offter a range of condenser size for each compressor,  and thes eshould be closely compared in terms  of higher duty and lower running cost. A small condenser will result in a higher condencing temperature and therefore a drop in the refrigerating effect , since the liquid enters the expansion valve hotter, and decrease in volume pumped due to the lower volumetric efficiency. There will also be an increase in the drive motor power. 

13.3 Compressor packs

This term is used to describe an assembly of several compressor mounted on a frame . complete with liquid receiver ,suction and discarge headers, oil separation and oil oil return piping and controls (figures 13.4 and 13.5). they are widely used in centralized supermarket system and the compressor serving the low – temperature evaporators and those serving the chill loads may be mounted on the same frame and piped accordingly. Compressor packs provide an efficient means of dealing with a wide span of refrigeration load. There can be up to 10 small compressor ,either scroll or  semi – hermetic , and this offers a large number of capacity steps by switching compressors . alternatively a smaller number of uneven compressor may be used. Compressor packs are usually custom built to individual supermarket requirements  although manufacturers will probably use standardized  design and contruction methods.

The concept has been extended to factory – built rooftop units where the compressor pack instralled within the overall condenser housing (figure 13.6)

Figure 13.4 : semi – hermetic compressor pack

Figure 13.5 scroll compressor pack( hubbard)

Figure 13.6 scroll compressor pack within rooftop condenser (hubbard)

13.4Chillers and air cooling packages(artic circle)

Chillers and air cooling packages

These are true packaged units in the sense that all the parts of the refrigeration system and its control are factory assembled and tested in the complete state. There are four configurations:

Air cooling,air –cooled

Air cooling,water – cooled

Liquid cooling,air – cooled

Liquid cooling, water – cooled

—  Air cooling packages are limited by the volume of cooled air that needs to be in close proximity to the machinery. Example of fully packaged air coolers are room air conditioners of the integral ‘through the wall’ type(chapter 25) and refrigerated vehicle units (chapter 17).

—  Liquid cooling packages . frequently termed  ‘ chiler ‘ .are self – contained system and may be either air –cooled or water –cooled.(figure 13.7 and 13.8). because chilled water  is a highly flexible and and efficient means of distributing cooling in many  types of building ,the range of chillers available on the market is very large. They can be found with compressors of all types: reciprocating, scroll,screw and centrifugal together whit heat exchangers of the shell and tube type or plate heat exchangers. Two refrigerant circuits are commonly used because this gives more capacity flexibillity and offers some redundancy.

—  Air conditioning is the main application, but they are also used for process cooling towers and this improves the chillers’ overall thermodinamic effectiveness as compared to air-cooled chillers because heat rejection is at or near the ambient air’s wet-bulb temperature rather than the higher, sometimes much higher, dry-bulb temperature. Many chillers are designed to work in reversed mode to provide heating when required.

Figure 13.7 :air – cooled water chiller ,nominal 600 kw capacity with two r134a refrigerant  circuits,single shell and tube evaporator , and capacity controlled semi – hermetic screw compressor (airedale)

Figure 13.8 :water – cooled water chiller ,nominal 250 kw capacity with two r407c refrigerant circuits,brazed plate heat exchangers (1 evaporator,2 condensors), and multiple scroll compressors(airedale)

—   Chillerratings, in accordance whit EN14511, refer to the entering and leaving chilled fluid temperatures and  either the ambient air-condition(air-cooled) or the cooling water entering and leaving temperatures(water-cooled).

13.5

To avoid the constraint of having all parts  in one package,the evaporator be split from tyhr condensor and the compressor going with either.

                The units is designed as a complate system but  the two parts are located separately and connected on site.On some small units,flexsible refrigrant piping may be provided.largersplit packages must be piped on site by normal methods,and then processed and charged as an open plant.the height of a split unit evaporator above the condensor may be limited and the supplier’s instructions should be folowed.see also multi-splits .

                Evaporator sets,as supplied as part of a split package or for apllication with a condensing unit,are of three main types:

1.Air-conditioning,having the air-colling coil with drip tray under,expansion valve,fan and motor,air filters,inlet and outlet grilles.They may also include dampers and duct connections for return and fresh air,heaters,humidifiers and various controls.

2.cold store evaporators ,having the coil with drip tray under,fans,aand possibly the expansion valve.

3.cold store evaporators for use blow + below 2˚C with defrost elements.

13.6 TESTING OF PACKAGED UNITS

Manufactures test procedures for packged units may include some of the following:

1.      Safety pressure tests and leak tests should always be include(see also section 11.3)

2.       rating test,from a representative unit which forms the basis for thepublished capacity and application leaflets.

3.      Type test, which verify the product as designed will function properlywhen applied within the required operating envelope , and fail safe when subjected to certain abnormal operating modes.

4.      Rating check test on a proportion of production units , to verify that standards are being maintained.

5.      Function test on all production units , to verify correct operation of components .

6.      A short – running test at normal conditions to check for reliability of operation plus ,possibly, an approximate capacity check.

7.      Run at maximum operating conditions.

Factory test procedures can be costly, but are much more efficient than performing the work in the field. Records will be kept of all such test  and , in the case of larger units, manufacturers will, if asked , provide a certified copy of the test on the equipment supplied .

                13.7 other packages

A very large variety of smaller self – contained refrigeration and air – conditioning packeges are made, mainly for the cunumer durable market and small domestic application . they include:

·         Domestic refrigerators and freezers .

·         Retail display cold and freezer cabinets and counters .

·         Cooling trays for bottles ( beer, soft drinks, wines)

·         Instantaneous draught beer coolers . these usually comprise a tank of constantly chilled water , through which the beverage flows in stainless stel piping.

·         Ice makers – cubes and flakes.

·         Cooled vending machines.

·         Soft ice – cream freezers.

·         Dehumidifiers, in which air is passed first over the evaporator to remove moisture and then over the condenser to re – heat and lower the humidity  ( see figure 26.1)

·         Drinking water chillers. hgf