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Evap, Cond, MD, Receivers > RACT Unit 22 > Flashcards

RACT Unit 22 Flashcards

1
Q

The condenser is a heat exchange device that _______ heat from the system

A

rejects

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2
Q

What are the 3 main functions of a compressor in order of occurrence?

A
  1. De-superheating the vapour
  2. Condensing vapours to liquid
  3. sub cooling the liquid
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3
Q

What main function has the greatest amount of heat absorbed in the system?

A

When the refrigeration is changing state (vapour to liquid)

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4
Q

The condenser operates at _______ pressures and temperatures than the evaporator and is often located _______

A

higher, outside

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5
Q

Water cooled condensers can operate at much _____ condensing temps

A

lower

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6
Q

Because water has a _____ specific heat and density than air, water cooled condensers are more _______ than air cooled

A

higher, efficient

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7
Q

The condenser also rejects heat picked up in the ______ line, _______ and heat of ______ compression

A

suction line, compressor, and heat of compression

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8
Q

Three types of water cooled condensers are:

  1. Tube within a _____ condenser (double tube)
  2. Shell and ______ condenser
  3. Shell and ____ condenser
A
  1. tube within a tube condenser (double tube)
  2. shell and coil condenser
  3. shell and tube condenser
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9
Q

Tube-within-a-tube Condensers:

  1. Two styles: the ____ type and the _______ type with flanged ends
  2. Heat exchange takes place between the fluids in the ______ and _______ tube
  3. Refrigerant flows in the ______ tube
  4. Refrigerant and water flow in _______ directions to maximize the _______ rate
A
  1. coil type and cleanable type
  2. Inner and outer
  3. outer tube
  4. opposite, transfer rate
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10
Q

A tube within a tube condenser is constructed by sliding one tube through another tube. The tubes are _______ in such a manner that the inside tube is ________ from the outside tube

A

sealed, separated

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11
Q

Mineral deposits:

  1. Heat from the ________ gas causes minerals to come out of solution

1A) Form scale that adheres to the _____
1A) i) Scale acts as an _______, reducing heat transfer

1B) Water is chemically treated to reduce ______ formation on the interior pipe surfaces

1C) Dirty condensers lead to ____ ______ pressures

1D) Tube within a tube condenser can not be cleaned mechanically with ______

A
  1. discharge gas

1A) pipes
1A) i) insulator

1B) scale

1C) high head pressures

1D) brushes

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12
Q

Scale deposits are normally found on the inner ______ tube

A

water

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13
Q

Cleanable tube-within-a-tube condensers:

  1. Have end _______, which are removed to access the _______ circuit
  2. The _________ circuit remains sealed while the ________ circuit is open
  3. Straight tubes are more expensive, but more easily ________
  4. ________ pump and chemicals are used to ______ the water tube circuit
A
  1. flanges, water circuit
  2. refrigerant , water
  3. serviced
  4. circulator pump, descale
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14
Q

Cleanable Tube-within-a-tube Condensers: Cleaning brush

Parts;

  1. Rotating _____
  2. water _____
  3. flexible _____
  4. Nylon _______
A
  1. rotating brush
  2. water flush
  3. flexible shaft
  4. nylon casing
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15
Q

Shell and Coil Condensers:

  1. Coil of tubing enclosed in a ________ shell
  2. Water flows through the _______
  3. Refrigerant from the comp is discharged into the ______

3A) Shell also acts as a ________ storage tank

  1. When ref comes in contact with the cool coil, it _________ and falls to the bottom
  2. This condenser must be cleaned __________
A
  1. welded
  2. coil
  3. shell

3A) receiver

  1. condenses
  2. chemically
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16
Q

Shell and coil condensers:

The hot refrigerant gas is piped into the _______ and the water is contained inside the _______

A

shell , tubes

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17
Q

Shell and Tube Condensers:

  1. Most _________ type or condenser
  2. normally used in _______ installations
  3. Can be cleaned ____________ with _______

3A) Comp discharge gas is piped into the ______
3A) i) Water flows through the _____ in the cond.
3A) ii) The ends of the shell are removed for _______
3A) iii) The shell acts as a _______ storage tank

A
  1. Expensive
  2. Larger
  3. Mechanically, brushes

3A) piped
3A) i) tubes
3A) ii) cleaning
3A) iii) Receiver

18
Q

Four-Pass Shell-and-tube Condenser:

  1. Water can be circulated back and forth through the condenser by using the ____ _____ to give the water proper direction
  2. The number of _____ passes will vary with the ____ plate design
A
  1. end caps

2. water, end plate design

19
Q

Wastewater Systems:

  1. Water used once and then ______ down the drain

1A) Economical of water is _____ or system is _____

1B) Drawback: Water ______ can vary greatly

1C) Amount of water needed depends on the temp difference between the water ____ and _____ of the __________

A
  1. wasted

1A) free, small

1B) temperature

1C) in, out, condenser

20
Q

Wastewater systems: Plentiful water;

Waste water systems are used when water is _______ and at a low _____ such as from a well or lake

A

plentiful, low cost

21
Q

Refrigerant-to-water Temperature Relationship for Wastewater Systems:

  1. Water flow can be varied using a _____- ________ valve with a ________ tap
  2. Constant _______ pressure maintained by letting more or less water into the condenser as the head pressure changes
  3. Water ____ temperatures often vary with the ______

3A) Faster inlet when water is ______
3B) Slower inlet when water is _______

A
  1. water-regulating valve, pressure tap
  2. head
  3. inlet , season

3A) warmer

3B) colder

22
Q

Re-circulating water systems:

  1. The water flowing through condenser pumped to a _______ location, ______ , and _______

1A) Design water temp is ___F

1B) A water flow rate of ___ gpm per ton of refrigeration is required to absorb heat

1C) There is a ___F split across the ______ circuit

A
  1. remote location, cooled, and reused

1A) 85F

1B) 3.0gpm

1C) 10F, water circuit

23
Q

Recirculating Water Systems Described:

  1. The water cooled condenser absorbs _____ from the refrigerant, ______ the water to a cooling tower at a ______ location
  2. Condenser is located _____ to the compressor and tower is on the ____ outside the structure
A
  1. heat, pumps, remote

2. close, roof

24
Q

Cooling Towers:

  1. Device that passes outside ____ over ______ to remove system _____
  2. Capacity limited by the amount of ________ that occurs at any given time

2A) Towers can cool the water to a temp within ___F of the ____ - _____ temp of the air surrounding the tower

  1. Types; (3)
A
  1. air, water, heat
  2. evaporation

2A) 7F, wet-bulb

  1. Natural Air, forced draft, evaporative
25
Q

Forced-Draft Cooling Tower:

  1. The relationship of a forced-draft cooling tower to the _______ air.
  2. A) Cooling tower performance depends on the ___-____ temp of the air

1B) This relates to the ______ and the ability of the air to absorb _______

A
  1. ambient

1A) wet-bulb

1B) humidity , moisture

26
Q

Natural-Draft Towers:

  1. Often made of ___wood, fibreglass or ________ sheet metal
  2. No ______ to move air through
    2A) natural ______ move air through the tower
  3. Water enters the tower from the ____ and is cooled as it falls to the ______
    3A) Some _________ in the process, helping to cool the remaining ______ in the tower
  4. Additional water added through a ______ valve
A
  1. redwood, fibreglass , or galvanized sheet metal
  2. No blowers
    2A) natural breezes
  3. top, bottom
    3A) evaporates, remaining water
  4. float valve
27
Q

Forced - or Induced-Draft Towers:

  1. Uses ____ or _______ to move air through
    1A) As ______ falls through the tower, air is moved across to air in _______
  2. Can be located almost ________
  3. The fan cycled ___ and ____ to maintain the desired ________ temperature
    3A) Forced draft: air is _____ through tower
    3B) Induced draft: air is _______ through the tower
A
  1. fan or blower
    1A) water, aid in cooling
  2. anywhere
  3. on and off, water
    3A) pushed through
    3B) pulled through
28
Q

Evaporative Condensers:

  1. Located ______ cooling tower
  2. Uses the ______water over and over by means of a ______ located at the tower
  3. _______ system replaces evaporated water
  4. Both ___ and ______ used to desuperheat, condense, and subcool refrigerant
  5. Water allowed to escape on a regular bases to prevent ______ ________
    5A) Water escaping is called ____down
A
  1. Inside
  2. same, pump
  3. Makeup
  4. air and water
  5. prevent mineral deposits
    5A) blowdown
29
Q

Air-Cooled Condensers:

  1. ____ absorbs heat rejected by the system in locations where water is difficult to use
  2. Horizontal, ______ or _____ intake and top discharge
  3. Hot gas enters the condenser from the ____
  4. For standard efficiency systems, the refrigerant will condense at a temp about ___F higher than the outside _______ temperature
A
  1. Air
  2. horizontal, vertical, or side intake and top discharge
  3. from the top
  4. 30F higher then outside ambient air temp
30
Q

Air-Cooled Condensers: Function of Fins;

  1. Fins are designed to give the coil more _______ ____
A
  1. surface area
31
Q

High-Efficiency Condensers:

  1. Have _______ surface areas than standard condensers

1A) Allow systems to operate at ______ pressure

1B) allow systems to operate more _________

1C) Can operate with ______ pressure as low as ___F higher than the outside ambient air temp

A
  1. large

1A) lower pressure

1B) more efficiently

1C) head pressure as low as 10F

32
Q

The Condenser and Low Ambient Conditions:

  1. Condensing temperatures drop when the outside ambient temperature ____

1A) Reduces the ________ pressure on the ____ pressure side of the system

1B) A _______ evap coil may result

A
  1. drops

1A) reduces operating pressure on the high-pressure side

1B) starved evaporator coil

33
Q

Head Pressure Controls: Practical Methods;

Methods to maintain correct head pressure:

  1. Fan-_____ controls
  2. Variable-_______ drive (VFD) condenser fan motor controls
  3. Da_____
  4. _______ flooding
  5. Condenser _______
A
  1. Fan-cycling control
  2. Variable-frequency drive
  3. dampers
  4. condenser flooding
  5. condenser splitting
34
Q

Head Pressure Controls: Fan Cycling Devices;

  1. Used on _____- cooled condensers
  2. As head pressure drops, fan cycles ____
  3. As head pressure rises, fan cycles _____
  4. Can be added without much ______
  5. Causes _____ pressure to swing up and down
  6. Some condensers may have _____ then one fan
    6A) May remain on at all times or _____ on/off
    6B) Head and ______ pressures will decrease
A
  1. air cooled condensers
  2. cycles off
  3. cycles on
  4. without much expense
  5. head pressure to swing up and down
  6. more than one fan
    6A) cycle on/off
    6B) Receiver
35
Q

Head Pressure Controls: VFD Condenser Fan Motors;

  1. Vary speed gradually according to _____ pressure or outside ambient temperature _____
  2. Motor speed changes as the incoming ______ frequency changes
  3. Keeps a more _______ head pressure
    3A) prevents erratic head press changes seen in ____ motor _____ cycling
A
  1. head pressure, ambient temp changes
  2. voltage
  3. consistent
    3A) seen in fan motor cycling
36
Q

Head Pressure Controls: Air Shutters or Dampers:

  1. Located at the _____ or the _______
  2. Operated by pressure-controlled ______
  3. Provide ____ head pressure control
A
  1. Inlet or outlet
  2. piston
  3. even
37
Q

Head Pressure Controls: Air Shutters or Dampers:

With a single fan:
1. Shutter installed over the ____ or over the _____ to the fan

With Multiple fans:
2. Shutter-covered fan operated ___ the _____
2A) Others _____ by pressure or temp

A
  1. over the inlet or outlet
  2. All the time
    2A) cycled by press or temp
38
Q

Head Pressure Controls: Condenser Flooding;

  1. Causes head pressure to ____
  2. Accomplished by having enough refrigerant in the system to flood the condenser in the ____ and ____ weather

2A) Requires a _____ ref charge and an _______ liquid receiver

2B) Also required a valve ________ that allows the refrigerant liquid to fill the condenser during mild and cold weather

A
  1. rise
  2. mild and cold

2A) large refrigerant charge and oversized liquid receiver

2B) valve arrangement that allows ref to fill cond during mild and cold weather

39
Q

Head Pressure Controls: Condenser Splitting;

  1. Reduces extra refrigerant charge needed for ________ flooding
  2. ____ the condenser in two separate identical condenser ______
    2A) ______/______ condenser, _______ condenser
  3. _______ valve control energized/de-energized by controller sensing outside _____ temperature, an outdoor thermostats or a high-side pressure control
A
  1. condenser
  2. Splits, circuits

2A) Summer/Winter condenser, Summer Condenser

  1. Solenoid valve control, sensing outdoor ambient temp
40
Q

Using the Condenser Superheat:

  1. ___-cooled condensers have ____ discharge temperatures
  2. Can be captured and redistributed as _____ for the structure in the ______ or to heat ______
A
  1. air cooled condensers have high discharge temps

2. captured and redistributed as heat for the structure in water or to heat water

41
Q

Floating Head Pressures:

  1. Term used for attaining the _______ possible ________ temperature
  2. Allows the head pressure to follow the ______ temp without using head pressure _______

2A) TXV and some newer expansion devices can operate with pressure differences as low as ____psig

2B) Systems become ______ efficient since they operate at ______ pressure

A
  1. lowest possible condensing temperature
  2. follow the ambient temp without using head pressure controls

2A) as low as 30 psig

2B) more efficient since they operate at lower pressures

Evap, Cond, MD, Receivers (16 decks)

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