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Term 1: 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

Term 1: Evap, Cond, MD, Receivers (15 decks)

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