Unit 3 part 2
R-410 A boils at
-61 degrees F
Refrigerants
1. 100% vapor 2. 100% liquid 3. Mixture of liquid and vapor
Refrigeration cycle
1. The evaporator absorbs heat into the system 2. The compressor pumps the heat-laden vapor 3. The condenser rejects heat from the system 4. The expansion device meters the flow of refrigerant
Three important things may happen to the refrigerant in the condenser
1. The hot gas from the compressor is desuperheated from the hot discharge temperature to the condensing temperature. Remember, the condensing temperature determines the head pressure. This is sensible heat transfer. 2. The refrigerant is condensed from a vapor to a liquid. This is latent heat transfer. 3. The liquid refrigerant temperature may then be lowered below the condensing temperature, or subcooled to between 10 degrees F and 20 degrees F below the condensing temperature but is system dependent. This is sensible heat transfer
When both liquid and vapor are present under two conditions
1. When a change of state (boiling or condensing) is occuring, and 2. When the refrigerant is at equilibrium (i.e, no heat is added or removed)
Three main functions of the evaporator
1. absorb heat from the medium being cooled 2. allow the heat to boil off the liquid refrigerant to a vapor in its tubing bundle 3. allow the heat to superheat the refrigerant vapor in its tubing bundle
The temperature of a condenser should be
125 degrees F
Saturation
212 degrees F - vapor and liquid presence
The temperature of an Evaporator should be
40 degrees F
Condensing unit
A compressor and condensing unit are incorporated into a single piece of equipment
Rotary Compressor
A compressor that uses rotary motion to pump fluids.it is a positive displacement pump
Screw compressor
A compressor that uses screw-type components to compress refrigerant. These are normally used in large systems. Popular in low temperature refrigeration applications
Medium-temperature
A refrigeration system that maintains a space at a temperature between 35 degrees F and 40 degrees F would be classified as what type of system?
Refrigerant
A substance that can be changed readily to a vapor from a liquid by boiling and to a liquid from a vapor by condensing
Subcooling
Any liquid below 212 degrees F/211 degrees F
Superheat
Any temperature of a gas above the boiling point for that liquid
R-401C color
Aqua
R-407A color
Bright green
R-407C color
Chocolate
R-401A color
Coral red
R-407B color
Cream
Pressure-enthalpy chart
Creates graphical representation system pressure scales on the vertical axis (psia)
R-114 color
Dark blue
sickness, injury, and death
Designed to protect people from
Pressure-enthalpy chart, heat content
Enthalpy is defined as __________
Pressure-enthalpy chart
Enthalpy scale along bottom of chart
R-22 color
Green
R-402B color
Green brown
Subcooling
Heat removed from a liquid below the saturation temperature
Pressure-enthalpy chart
Horseshoe curve represents saturation curve
R-134A color
Light blue
R-402A color
Light brown
R-123
Light gray blue
R-406A color
Light gray green
non toxic
Modern refrigerants are
Superheat
More than 212 degrees F/213 degrees F - any heat above saturation, All vapor
R-401B color
Mustard yellow
R-1234yf
Of the following refrigerants, which has the lowest global warming potential (GWP)?
has a significant temperature glide
One of the challenges of plotting an R-407C system on a pressure/enthalpy chart is that this refrigerant
R-11 color
Orange
R-404A color
Orange
R-502 color
Orchid
NRE =
Point D- Point B
THOR =
Point E - Point B
required
Proper ventilation is
R-113 color
Purple
Replacements for R-22 include
R-410a and R-407c
manufacturer's instructions
Recovery equipment must be used according to
CFC, HCFC, HFC
Refrigerant recovery, Recycling, and Reclaiming is intended to reduce the emissions of _____, _____, _____, refrigerants
safe
Refrigerants must be
Pressure-enthalpy chart
Refrigerants saturated on/under curve
Adiabatic Expansion
Results in temperature and pressure changes with no change in heat content
R-410A color
Rose
29 degrees F
Saturated R-410A at a pressure of 95 psig will change at a temperature of
R-717 color
Silver
Methods used for detecting refrigerant leaks
Soap bubble solution, Halide leak detector, Electronic leak detectors, Ultraviolent leak detectors, Ultrasonic leak detectors
Evaporator Superheat
Superheat that is only picked up in the evaporator
R-409A
Tan
boiling point
The ____________ of water can be changed and controlled by controlling the vapor pressure above the water
Green
The color-coding for an R-22 refrigerant cylinder is
Critical point
The critical temperature of a gas is the highest temperature the gas can have and still be condensable by the application of pressure above the critical temperature a gas cannot be saturated regardless of the amount of pressure applied
System Superheat
The total superheat that is picked up in the evaporator and the suction line
THOR means
Total Heat of Rejection
Reciprocating Compressor
Uses a piston in a cylinder to compress the refrigerant and valves make sure the refrigerant is flowing in the right direction, back and forth motion
Rotary Compressor
Uses a rotating drum-like piston that squeezes the refrigerant vapor out of the discharge line, Typically used for applications on smaller equipment like window air conditioners.
Scroll Compressor
Uses two nesting scrolls to facilitate the compression process. One scroll is stationary while the other is not, most commonly used in new manufacturing
40, 2445, 0.5
Water vapor at ________ degrees F takes up ________ ft cubed of space, where as R-410 A at ______ ft cubed of space
toxic corrosive gases
When burned, _____________________ are created
For compressors with similar capacities, rotary compressors are smaller than reciprocating compressors
Which of the following statements is true with regards to reciprocating and rotary compressors?
R-12 color
White
R-500 color
Yellow
External TXV has
a secondary connection
Heat naturally flows from
a warmer to cooler substance
Rotary compressors are used for
applications in the small equipment range, such as window air conditioners, household refrigerators, and some residential air-conditioning systems
Refrigerant cylinders
are color-coded to indicate the type of refrigerant they contain
R-500 and R-502
banned in 1996
Refrigerants cylinder/drums are
color-coded
Heat
contained in the warm air in the room flows into the cooler refrigerator through the insulated walls, and also when the refrigerator door is open
Refrigerants must be
detectable
Co2 can
exist in all three phases simultaneously in equilibrium at its triple point:-69.9 degrees F/75 PSIA
Compressor
for a system that uses water as the refrigerant would have to be massive to accomplish the same amount of work done by a 410 A system
Electronic leak detectors
general area leaks
Refrigerant recover is
mandatory during service and installation operations
Pressure/enthalpy diagrams
may be used to plot refrigeration cycles
Internal TXV has
one connection
Percentage of quality means
percentage of vapor
Soap bubble solution
pinpoints leaks
Ultraviolent leak detectors
pinpoints leaks
R-12
primarily for high/medium temp refrigeration applications (banned 1996)
R-22
primarily in air conditioning applications (production ended in 2020)
R-134a
replacement for R-12 with retrofit
Refrigerants
should be recovered or stored while a refrigeration system is being serviced, then recycled, if appropriate, or sent to a manufacturer to be reclamed
High temperature refrigeration systems
systems are most commonly used to keep an occupied space in the 68 degrees F - 80 degrees F, for comfort cooling
Low temperature refrigeration systems
systems often refer to systems that maintain products at temperatures below 0 degrees F, to freeze product
Medium temperature refrigeration systems
systems typically maintain products at temperatures between 35 degrees F - 45 degrees F, to keep food fresh
Refrigeration
the process of removing heat from a place where it is not wanted and transferring that heat to a place where it makes little or no difference
Halide leak detector
uses an open flame
Ultrasonic leak detectors
uses sound waves
