quiz 4-10

Which of the following is true regarding cap. tubes?

"With an increase of evaporator load, the evaporator will initially starve of refrigerant"

Which of the following is ture regarding the operation of the TX valve?

"With an increase of evaporator load, the pressure in the bottom of the powerhead will be less than the top causing the valve to move down increasing refrigerant flow."

"Complete the sentence: The penalty for refilling and transporting a nonrefillable cylinder is a

$500,000 fine and/or 5 years imprisonment

The cooling water flow requirement for a water cooled condenser is about _________.

1-1.5 gpm

What is the approximate split (in dF) between the water leaving and the refrigerant in an evaporative type condenser? Give a numeric number only.

10 df

"If the suction line is 7/8"" or smaller, the sensing bulb should be located at ____ o'clock. (enter a number only)"

12

Crankcase heaters are used to reduce entrained refrigerant in the lube oil by heating the oil to ______ dF. (enter a number only)

130

The maximum allowable amount of moisture allowed in a system is _______ ppm (enter a number only).

15

Safety valves on refrigerant bottles are set for what safety factor

150%

According to ASHRAE regulations, a mechanical space with an A1 refrigerant would require an alarm system if the oxygen level drops below _____ %

19.5

Complete the following sentence with numerical answers separated with a""-"" and no spacing: Water flow requirement for an evaporative condenser is __-__ gallons per minute."

3-4

"If the suction line is larger than 7/8"", the sensing bulb should be located at ____ or ____ o'clock. (enter only numbers with a comma in between)"

4 8

A Class I chemical has an ODP that is

>0.2

Which of the following statements are TRUE?

A capillary tube based refrigeration system is a critically charged system A capillary tube based refrigeration system does not use a receiver "In capillary tube based systems, pressure equalization takes place when compressor is off "

Which of the following statements are TRUE?

A float valve maintains a constant level of liquid in the float chamber

Which of the following are used as dessicants in filter-driers?

Activated alumna Silica gel Anhydrous calcium sulfate

The best time to check the oil level in the compressor is

After the system has been running for a long time and has been stopped.

The general principal of evaporative condensers (in the general term) is/are:

Air flow sprayed water In addition to air flow and sprayed water the evaporative condenser relies on lower humidity so that the sprayed water can vaporize. Although a lower ambient temperature is ideal, it is not relied upon for proper operation.

Which of the following is not indicated by bubbles in the sight glass indicator?

Air in the system

Choose the heat exchanger types that are used for refrigeration system condensers

Coaxial shell & coil shell & tube plate type bare tube

Which of the following refrigerant component tends to be the most expensive

Compressor

Which refrigeration system major component has the greatest capacity for heat transfer

Condenser

NRV valves are used on what type of bottle(s)

DOT 39

Which of the follow is true regarding distibutors?

Distributors should only be mounted up or down. They are used to prevent sections of the evaporator in the early and midstages from being vapor bound They are commonly used with TX valves and orifices

Which of the following are variable opening type of flow control:

Electronic expansion valve Low side float Hand expansion valve High side float Automatic Expansion Valve

"If Brine is used as a secondary refrigerant, its flash point must be below 150 dF."

False

"If the sight glass indicator shows moisture (yellow), a quick way to remove the moisture is to heat the filter-drier with a heat gun."

False

"With fin and tube evaporators, increasing the number of fins always increases the heat transfer capability of the evaporator."

False

A lower GWP is always better

False

Fin and tube evaporators are used only in air exchange systems.

False

Refrigerant soleniod valves can provide variable flow of refrigerant.

False

The marking T.W. on a DOT cylinder indicates the ""Target Weight"" (the maximum fill weight with the cylinder)"

False

The primary purpose for all flow controls (metering devices) is to control the superheat of the refrigerant leaving the evaporator.

False

Using a TXV with an evaporator with a large pressure drop without an external equalizer will result in a higher COP and higher compressor Volumetric Efficiency.

False

A very high pressure refrigeration system

Has a refrigerant with a boiling point less than -50 dC

Which of the following are advantages of a cap. tube?

High and low side pressures equalize during off cycle reducing start-up load of the compressor No moving parts Inexpensive

Which of the following method is used for a centrifugal compressor capacity control?

Hot gas by-pass VFD (vary speed) variable inlet vanes controlled condenser water flow

Which of the following statements are TRUE?

In a capillary tube pressure drop takes place due to fluid friction and acceleration .

Which of the following statements are TRUE?

In an automatic expansion valve, the mass flow rate of refrigerant decreases as the refrigeration load increases " An automatic expansion valve maintains a constant pressure in the evaporator Automatic expansion valve based systems are critically charged

Screwing in the adjuster for the BPR will (increase / decrease) the evaporator pressure.

Increase

Which of the follow are true regarding secondary refrigerants?

It can be propylene glycol it can be water it can be ethylene glycol They are cooled by the primary refrigerant

Which is true regarding the accumulator?

It is not considered a major system component Is often used in systems using economizers It is often used in systems using AXV flow controls

Which of the following valves would be closed during a running high side charge?

King Valve

"List the sequence of heat transfer within the refrigerant as it flows into, through and out of the evaporator. Use only the terms: Sensible Heat and Latent Heat. Separate each term with only a comma."

Latent Heat, Sensible heat

Bare pipe evaporators are typically used in which type of system?

Low temp refrigeration

Off cycle defrosting is only used for:

Medium Temperature Refrigeration

Which of the following refrigerants can fractionate?

Near Azeotrope Zeotrope

Which of the following are a type of flow control:

Orifice Electronic expansion valve Hand expansion valve High side float Low side float Automatic Expansion Valve Capillary tube

Which of the following is NOT a type of refrigerant oil?

PolyAlkylMineral

A Green colored refrigerant bottle would indicate which refrigerant

R-22

Which of the following refrigerant should only be charged as a liquid?

R-404A

Which of the following type compressors can have variable capacity?

Reciprocating Scroll Screw Centrifugal

"List the sequence of the state of the refrigerant as it flows into, through and out of the evaporator. Use only the terms: Saturated, Subcooled, Superheated.

Saturated, Superheated

List the sequence of heat transfer within the refrigerant as it flows into, through and out of the condenser. Use only the terms: Sensible Heat and Latent Heat.

Sensible Heat, Latent Heat, Sensible heat

"List the sequence of the state of the refrigerant as it flows into, through and out of the condenser. Use only the terms: Saturated, Subcooled, Superheated.

Superheated, Saturated, Subcooled

The back (evaporator) pressure regulator (BPR or EPR) would be used with what type of flow control?

TXV EEV

The receiver would be used with which type of flow control?

TXV EEV

The temperature of the refrigerant in the evaporator is mostly dependant by the:

The pressure in the evap

Which of the following are true regarding zeotropes?

The will fractionate they will have temperature glide the are composed of 2 or 3 refrigerants

Subcooled refrigerant leaving the condenser has the potential of increasing the system's efficiency by 5%.

There is a gain of about .5% efficiency per degree of subcooling added to the refrigerant entering the flow control. With 10 dF subcooling at the condenser, you potentially can have a 5% gain although this could increase or decrease at the flow control

"If refrigerant velocity is not sufficient in an evaporator, oil may increase in viscosity and ""log up"" in the evaporator."

True

"If using a system with a cap. tube and is not critically charged, a drop in evaporator load could result in liquid slugging the compressor"

True

"The Automatic Expansion Valve (AEV) tends to operate opposite regarding evaporator load. When the evaporator load decreases, the AEV will open feeding more refrigerant."

True

"When refrigerant travels through the evaporator, the liquid and vapor have different velocities"

True

An Automatic Expansion Valve (AEV) maintains constant pressure (hence temperature) in the evaporator.

True

During off cycle defrosting the compressor is stopped but the evaporator fan continues to operate.

True

Electronic Expansion Valves work the same as TX valves but uses electricity via electronic controls to operate the power head of the valve

True

The back (evaporator) pressure regulator (BPR or EPR) would be located after the TXV sensing bulb.

True

The high side float has a float chamber under condenser pressure and maintains a constant level in the float chamber.

True

The low side float has the float chamber under evaporator pressure controlling liquid refrigerant level in the evaporator.

True

Choose the following types of flow control by general category:

Variable opening Fixed type

Select from this list fluids that could be used as a secondary refrigerant

Water Brine Ethylene Glycol Propylene Glycol

"Which classification under Refrigerant Toxicity/Flammability Group would represent the worst refrigerant (ex.: A1, A2, B1 .)

b3

Which of the following classification of refrigerants have been or are currently being phased out?

cfc hcfc

"If the power fluid (refrigerant) in the sensing bulb is different than in the system, the TXV is known as _____________ ______________."

cross charged

Which of the follow does not determine the capacity of an evaporator?

defrost system for the evaporator

the possible problem of overcharging a system with a condenser that also acts as the receiver is/are:

excessive hydraulic pressure the refrigerant covering the condenser tubes which effectively reduces the condenser surface area causing an increase in HIGH side pressure.

"When installing a sensing bulb, the bulb charging tail should be:"

facing up if the bulb is mounted vertical closest to the suction line if the bulb is mounted horizontal

In order to liquid slug a compressor, the system has to floodback.

false

nergy Efficiency Ratio (EER) can be found by multiplying the system's COP X PI

false EER = COP x 3.41 (not 3.14)

"The marking W.C. on a DOT cylinder indicates the ""Weight of the Cylinder""

fase

Which of the following are potential problem with evaporative condensers

ice up biological growth scale build up

A chillers economizer:

increases the density of the refrigerant between compressor stages The economizer in a chiller system will inject colder refrigerant vapor between the compression stages to cool the refrigerant there and increase its density. This increases compressor efficiency.

Which are true regarding hot gas defrost?

it is very complex and expensive it may also may be termed cool gas defrost the fan must be shut off during and after defrost is completed defrost gas comes from the hot gas line defrosting may use refrigerant coming from the receiver It is the overall best method

The largest heat transfer in the evaporator is done by the refrigerant as it goes through the ________ heat phase.

latent

"A ""safety head"" will:"

lift off the block when liquid slugged

Which of the following compressors would not commonly be available as a hermetically sealed unit? (select all that apply)

screw centrifugal

Which are true regarding electric defrost?

standard timed defrosts may last 45 60 minutes The heaters can use about 1 kW per foot of evaporator length the surface temperature of the heater itself can exceed 300°F

Which of the follow are true regarding scroll compressors.

the most efficient design Correct Are only hermetically sealed Correct Can operate at 10% of maximum capacity

Which of the follow are true regarding 500 series refrigerants?

they are azeotropes or near azeotropes they are a mixture of different refrigernts

Which of the following is true regarding screw compressors?

they require lube oil to lubricate AND seal the screws

"Regarding scroll compressors, the fixed scroll is on the top and the moving scroll mates under it."

true

A cooling tower is not really a condenser but a means for cooling water for the condenser.

true

A quick check for the proper operation of a water cooled condenser is to touch the refrigerant and water outlet pipes. They should both be warm. Neither should be hot nor cold.

true

Both the hermetically sealed ans semi-hermetically seal compressors are sealed from its ambient surroundings. The only difference is that the semi-hermetically seal compressor can be repaired by taking it apart. The hermetically seal ed compressor is seal welded together.

true

Most often the only method for cleaning coaxial and shell & coil condensers is by use of chemicals.

true

The springs are there to close the valves. The make the opening of the valves harder.

true

the profile of a rotarty compressor is round and tall.

true

"In order to get a liquid charge out of a R-134a bottle, you should"

turn the DOT39 bottle upside down

Crankcase pressure regulators

will close with an increase of compressor suction pressure shares the same acronym as the condenser pressure regulator helps reduce compressor start up load are installed in the suction line will open with a drop in compressor suction pressure