Chapter-12 Oil in Refrigerant Circuits

႔ Chapter-12 Oil in Refrigerant Circuits Chapter-12 Oil in Refrigerant Circuits ၁၂.၁ (oil) compressor ၏ compressor (lubricate sealing Compress...
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Chapter-12 Oil in Refrigerant Circuits

Chapter-12 Oil in Refrigerant Circuits ၁၂.၁ (oil)

compressor



compressor

(lubricate

sealing

Compressor

(manufacturers)

(၁၂-၁)

refrigerant

(oil)

၁၂-၁ Refrigerant

(viscosity)

(lubricant types)

(grade)

-

12-1

Chillers and Chilled Water Systems

polyolester



hydrocarbon

refrigerant

၁၂.၁.၁ Oil in Refrigeration System (၁)

compressor ၏

(moving parts)

(lubricate

႔(sealing

(၂)

refrigerant

(၃)

refrigerant







(၄) (

) Mineral oil (paraffin based)

( ) Synthetic oil (e.g. Polyol Esters or POE)



၁၂.၁.၂ General Classification of Oils

(

) Mineral oil (paraffin based)

( ) Synthetic oil (e.g. Polyol Esters or POE) (ဂ) Semi-synthetic oils. Compressor



refrigerant oil recovery rate Synthetic oil

refrigeration

(၁)

(extending oil change period)

(၂) (၃)

(reduce oil consumption)

(၄)

(lower operating oil temperature)

(၅) (၆)

(higher film strength)

(၇)

compressor

(reduce compressor wear and longer

compressor operating life) (၈)

(non-foaming character.)

(၉)

(low toxicity)

(၁၀)

(good for wide operating temperature range) Synthetic oil



Refrigeration system

seal material (water content)

(alkalinity)

(acidic level)

(viscosity) (chemical

element content) 12-2



Chapter-12 Oil in Refrigerant Circuits

၁၂.၂ Requirements and Characteristics ၏ဂ

(oil properties) (၁)

(viscosity)

(၂) Refrigerant

(miscibility and solubility with the refrigerant)

(၃) Pour point (၄) Floc point (၅) Flash or fire point Evaporator



condenser

(heat transfer)

compressor compressor



(oil)၏ (oil return)

system

compressor

(pressure)

(solubility characteristics)

Refrigeration machine CFC

HCFC

ammonia

refrigerant refrigerant

(mineral oil)

(mineral oil)၏ ဂ ၏

(viscosity)

(lubricity)

႔ HFC refrigerant mineral oil

synthetic oil



(availability) acids)



POE oils

(alcohols)

(properties) POE oil



(ester)



(cost) (organic



(ester)

original acid structure Refrigerant circuit

(lubricating oil)

(lubricating oil)၏ ၏



refrigerant (ammonia)

(solubility)

Refrigerant Evaporator

(solubility) ၏

(bearing)

(viscosity) (solubility)



12-3

Chillers and Chilled Water Systems



၁၂-၂ Typical low side sump refrigerant content and mixture viscosity Low-side

(pressure)

evaporator

(concentration) Halocarbon refrigerant



(viscosity)

(behavior)

(၁၂-၂)

- low pressure 1 bar



refrigerant 6 bar

(temperature)



evaporator tem

evaporation pressure

refrigerant ၁၀% (viscosity)

(bearing)

(bearing load carrying capacity) (viscosity)

(temperature)

(pressure)



Temperature/ P

Viscosity/ (၁၂-၃)

refrigerant R134a

POE oil

diagram

႔၏ characteristic

ASHRAE refrigeration

handbook (lubricants) (miscible)

refrigerant

“oil-rich solution”

“refrigerant-rich solution” -

(solution) Refrigerant

-

Refrigerant-rich solution compressor ႔(oil pump)

refrigerant-rich mixture

Crankcase

(shutdown) (viscosity)

heater

႔ Ammonia

(lubricants) evaporator ၏

(lubricant)၏



Lubricant

၏ဂ (၁)

(lubricant)၏ ဂ (bearing)

lubrication 12-4



Chapter-12 Oil in Refrigerant Circuits

(၂) Compressor

(discharge) (chemical

reactions)



(decomposition) (၃)



(၄)

system

flexible

seals

material

(compatible (၅)

(copper)

(ammonia)



compressor

႔ (၆) Mineral oil

(waxes) (solids)

(၇)

(enclosed

(၈)

(foaming characteristics)

(၉)

(precipitation)

(precipitate) motor)

(electrical

resistance)

(availability)

၁၂-၃ Viscosity/temperature/pressure diagram: shows percentage refrigerant in solution and corresponding viscosity. ႔



lubrication characteristic

refrigerant

(air)

႔ ႔(moisture)

(air)



႔(moisture) refrigerant

(contaminant)

(chemical stability) 12-5

Chillers and Chilled Water Systems



Compressor

crankcase

pressure

crankcase pressure (normal running)

၁၂.၃



(Moisture and Air Contamination)

System



formation)

(moisture)

(ice



(corrosion)

Refrigeration system

contaminant

(lubricants)

Compressor

႔ physical

(motor windings)

System

chemical



႔ ၏

system ၏

(cleanliness)





(tightly sealed)

Ammonia system ႔ Hermetic



semi-hermetic



႔ compressor

(electrical fault

(acid)



motor

(overheating)

contaminant

halogen

(Halogen acid)

(eye goggles)

(rubber gloves) ႔



POE lubricant ဂ

system



(organic acid)

(organic acid)



(halogen acid)

(acid test kit) ႔ lubricant

POE lubricant system

POE ႔(moisture)

POE lubricant

50 ppm

႔(moisture)

႔ ႔(moisture) filter–drier

၁၂-၄ Typical moisture ingress and subsequent removal by the action of the drier in a POE system 12-6



Chapter-12 Oil in Refrigerant Circuits

(၁၂-၄)

(installing)



(expected moisture content) Compressor

POE oil

35-95 ppm drier





50 ppm ႔



o

(chemical reaction)

႔ CFCs



HCFCs

system (Original Equipment

Manufacturers [OEM]) ၏



၁၂.၄ Oil Separators Reciprocating machine

compression stroke

refrigerant gas discharge gas



compressor ႔

over” compressor

discharge gas ၏

discharge gas ၏

“oil carry-

System ႔ (foaming) ႔

system discharge line

oil separator

(၁၂-၅)

oil

separator

12-7

Chillers and Chilled Water Systems



hot gas spiral



႔ ႔

၏ crankcase return line

95%





Oil

float valve

control

98%





compressor

႔ (tight

off)

shut-

solenoid valve (discharge

pressure

separator compressor

oil sump ႔(shutdown)

separator

high-pressure gas ႔

oil

(dilute) diluted oil

oil pump heater

၁၂-၅ Oil separator (Henry) (oil-injected) screw compressor separator

D

Separator ႔

oil

bearing

O

separator

႔ injection port

-

two-stage oil

99.7%



oil carry-over



oil separator



Oil Separator for Reciprocating Compressors Discharge oil separator ႔

reciprocating compressor

demister type

separator ၏ efficiency

wire mesh wire mesh

99.99%



demister oil

Oil carryover

Oil Separator for Screw Compressors Screw compressor separator

Oil

screw compressor

compressor ၏

oil separator Mists

droplet

screw ႔

Oil Still and Oil Recovery refrigerant

compressor

႔ refrigerant

refrigerant compressor



Discharge Oil Separator Oil Still and Oil Return 12-8



Chapter-12 Oil in Refrigerant Circuits

Compressor

discharge oil separator

refrigeration system

Oil mist

၏ discharge line

droplet

oil separator

Centrifugal compressor discharge centrifugal system

discharge oil separator

Reciprocating compressor

discharge oil separator compressor

Discharge oil separator



၁၂.၅ Oil Circulation Compressor

discharge line







refrigerant Condenser

compressor ၏

compressor

velocity (flowing back)

non-return valve

Horizontal line Condenser



႔ ႔

႔ ႔

refrigerant

expansion valve Evaporator

refrigerant evaporator



refrigerant





low-pressure vapor

suction gas

Evaporator ႔

evaporator

႔ refrigerant Suction line compressor



refrigerant

gas velocity

3.5 m/s

Evaporator

compressor ၏

droplets) velocity



compressor



refrigerant gas

(oil compressor



gas

7 m/s

Evaporator

compressor



Compressor

refrigerant

compressor ႔ compressor Compressor Compressor ၏





suction accumulator refrigerant “ q

“ q





capacity control velocity

velocity compressor



12-9

Chillers and Chilled Water Systems



Compressor compressor





၁၂.၆ Lubricating Oils and Their Effects Compressor ၏ crankcase

(lubricating oil)

refrigerant

vapor pressure



refrigerant





ဂ -



refrigerant ၏ thermodynamic property

၏ refrigerant

refrigerant

(chemical properties)

(physical properties) ammonia

(stable

system





HC refrigerants



HC refrigerant ဂ



(operating condition) ႔



(high-quality oil) ႔

႔ (decomposition)

corrosive acids

sludge refrigerant

Oil miscibility

D ၏ characteristic

oil miscibility

refrigerant

Refrigerant



refrigerant

(oil miscibility)

refrigerant

(၁) Refrigerating system

refrigerant

(၂) Condensing section

evaporator section

refrigerant (၃) Refrigerating system

refrigerant



refrigerant Lubricating oil ၏

(viscosity)

thermophysical

(rubbing (protective film)

surfaces) ႔

(viscosity)

(viscosity) ႔

(viscosity) (penetration)

Refrigerant

12-10



Chapter-12 Oil in Refrigerant Circuits

compressor ၏ separator



(discharge line)

oil

oil trap

HFC refrigerants

HFC blend refrigerant

HFC refrigerant

mineral oil

system

(၁)

mineral oil

(lower lubricant cost)

(၂)

refrigerant

(direct refrigerant replacement)

(၃)

(lower refrigerant solubility)

(၄)

(improved working viscosity)

(၅)

refrigerant

(၆)

(reduced refrigerant charge)

refrigeration effect

(၇)

S

(faster refrigeration on start)

-

(reduced slugging and oil

carry-over on start) (၈)

Refrigerant blend

(၉)

Oil separator



(composition)

(distortion)



(reduced oil separator

flooding) (၁၀) H

(reduced hygroscopicity)

(၁၁)

(reduced chemical reactivity)

(၁၂)

(reduced electrical resistivity)

(၁၃)

(reduced dirt transfer) Mineral oil

(

HFC refrigerant

)

(non-sticking suction need)

( )

(better visual detection)

(ဂ) (ဃ)

polyolester lubricant

(water solubility) (foaming characteristics)

E bearing lubrication

၁၂.၇ Oil System for Compressor Compressor ၏ ၁၂.၇.၁ Reciprocating Compressors Reciprocating compressor ႔

(oil pressure system)

(splash system) lubricating system

12-11

Chillers and Chilled Water Systems

Splash system



crankshaft ၏ (bearing channels)



main bearing

Bearing Oil pressure system ႔

crankcase



႔(oil pump)

connecting rods main bearings lubrication

piston pin





Compressor lubrication circuit ႔

overload relief valve

(oil pressure)

(safe level)

႔(shut down)

compressor

safety switch

၁၂.၇.၂ Rotary Compressors Rotary compressor

cylinder, blades

oil)

roller

႔၏

rotary compressor

compressor

(film of

oil pump

rotary

sliding action

၁၂.၇.၃ Centrifugal Compressors Centrifugal compressor ဂ



(speed)

Oil control system

bearings during cast-down oil filter relief valve

oil control system pump oil separator reservoirs to lubricate

oil cooler



၁၂.၇.၄ Helical Screw Compressors rotor

seal



forced lubrication system lubrication

႔ positive displacement pump

oil sump (reservoir) bearing

Compressor



႔ injection port



(off-cycle)

(oil dilution)

refrigerant

oil sump (reservoir)

heater

၁၂.၇.၅ Scroll Compressors Scroll

(orbiting) centrifugal

(orbiting)



Industrial refrigeration system oil level regulator strainers

scroll ႔

oil reservoir

solenoid

isolating valve

control

oil separator

(device) (၃) ႔



oil

system

compressor ၏

(oil test)

၁၂.၈ Promoting Oil Return Direct expansion compressor



dry evaporator system Evaporator tube

refrigerant refrigerant (horizontal 12-12



lines)

Chapter-12 Oil in Refrigerant Circuits

(velocity) 700FPM( (velocity)

700 feet)

(vertical lines)

1500 feet (457m)

Compressor



compressor



refrigeration Suction line

၏ Refrigerant refrigerant

(pressure)

Low-temperature evaporator (temperature)

C

oil return (pressure)

suction gas ႔

(temperature)

low-temperature evaporator Flooded evaporator



oil return suction line velocity

compressor



oil return line -End-

12-13