Chillers

Question 1

What is condenser approach

Answer 1

The difference between the temperature of the liquid refrigerant at the liquid line and the temperature of the LEAVING condenser water

Question 2

What is evaporator approach

Answer 2

The difference between the temperature of the evaporating refrigerant in the evaporator and the temperature of the leaving chilled water

Question 3

What is the generator

Answer 3

The component in an absorber that provides the heat required to separate the refrigerant from the absorber

Question 4

Two types of centrifugal compressors

Answer 4

Open drive or refrigerant cooled

Question 5

Difference between centrifugal and centripetal

Answer 5

centrifugal directs the refrigerant outward away from the shaft whereas centripetal pulls towards the center.

Question 6

Centrifugal chillers are a ___ displacement device

Answer 6

non-positive

Question 7

In a flooded system (chiller) ___ flows on the outside of the chiller barrel tubes and ___ flows through the tubes

Answer 7

refrigerant flows on the outside and water flows inside the tubes

Question 8

in a Direct Expansion (chiller) system, _____ flows on the outside of the chiller barrrel tubes and ____ flows through the inside of the tubes

Answer 8

water flows on the outside and refrigerant flows on the inside

Question 9

6 metering devices used on a chiller system

Answer 9

high side float
low side float
hand expansion valve
orifice
thermostatic expansion valve
electronic expansion valve

Question 10

two types of condensors

Answer 10

air cooled and water cooled

Question 11

An unloaded compressor runs and capacity no lower than ___%

Answer 11

40%

Question 12

what must run before and after centrifugal chiller operation?

Answer 12

oil pump

Question 13

Define surge conditions

Answer 13

When a system is operating outside the design lift parameters

Question 14

Define High side surge?

Answer 14

high condensing pressure pushing the refrigerant back to the evaporator

Question 15

According to some guy (TQ), what is the most common surge type?

Answer 15

low side surge (but not really)

Question 16

Name 4 common compressors used in Chillers

Answer 16

• Centrifugal
• reciprocating
• screw
• scroll

Question 17

3 methods of capacity control on Centrifugal Compressors

Answer 17

*Inlet Guide Vanes
Variable Frequency Drives (VFD’S)
Hot Gas Bypass

Question 18

2 primary reasons for Counter Flow

Answer 18

Increase subcooling and reduce flashing

Question 19

A rule of thumb is that ___GPM/ton of refrigeration is required with ___ F ° drop in water temp

Answer 19

2.4GPM with 10F°

Question 20

What is the 10/10/10 Rule

Answer 20

10° drop in water Evap, 10° rise in condensor and 10Delta in psi

Question 21

Formula for Lift

Answer 21

in F° Saturated Condensing Temp - Saturated Suction Temp

Question 22

Formula for Cooling tower Approach

Answer 22

Leaving Water Temp - Entering air wet bulb (smaller approach means more efficiency)

Question 23

Formula to find BTU/H of a system

Answer 23

Qbtu/h=500xGPMusxΔT
500 for Us gallon
600 for imperial

Question 24

Formula to find tonnage on a cooling system

Answer 24

Qton=(gpmxΔT)/24 to find tonnage of cooling on a system (us gal)
Qton=(gpmxΔT)/20 to find tonnage of cooling on a system (imperial)

Question 25

Why do you never starve the inlet of a pump

Answer 25

this will cause it to Cavitate

Question 26

What temperature is the Oil Sump kept at even when not in operation and why

Answer 26

140°F, this reduces the amount of refrigerant that the oil can contain

Question 27

What is the difference between aBsorption and aDsorption

Answer 27

absorption is absorbent refrigerant in a liquid state.

adsorption is absorbent refrigerant in a solid state.

Question 28

Define affinity

Answer 28

a molecule’s attraction to another molecule. (once bonded heat is required to separate them

Question 29

Purpose of absorber

Answer 29

Remove heat with chilled water and allow refrigerant to bond

Question 30

Purpose of generator

Answer 30

Add Steam heat to separate refrigerant bond

Question 31

What 2 additives are used in a Lithium Bromine solution

Answer 31

Octyl Alcohol and Inhibitors

Question 32

What are the 2 main functions of Octyl Alcohol

Answer 32

To be used as a wetting agent and as a surface tension breaker (allows for better heat exchange)

Question 33

What are the main functions of an Inhibitor

Answer 33

Prevents rusting and corrosion of internal parts and piping

Question 34

What are the 2 types of pump loops in use today

Answer 34

Primary Secondary, and Direct Primary

Question 35

On a screw compressor, which rotor is the driving force?

Answer 35

Male Rotor (Take it bitch!)

Question 36

What test is conducted to check the chiller tube integrity?

Answer 36

Eddy Current Test

Question 37

TXV’s on most chillers will try to maintain what Super Heat

Answer 37

8-12°F

Question 38

list 4 factors for Zone Valve Sizing

Answer 38

Pipe size
Flow Rate in GPM
Density of Water or Glycol
Pressure drop through the fan coil

Question 39

list 4 types of valves used in a chiller system

Answer 39

hand isolation and feed valves
zone control valves
three way capacity control valves
check valves

Question 40

Is a centrifugal chiller good with high or low compression ratios?

Answer 40

Low

Question 41

Do compressors start fully loaded or unloaded?

Answer 41

unloaded

Question 42

What do target baffles do?

Answer 42

Discharges refrigerant equally onto condenser tubes, protects condenser tubes from erosion or corrosion