Carol_23_compressors

A medium-temperature R-134a system that has a suction pressure of 22 psig and a discharge pressure of 185 psig would have a compression ratio of _________.

5.44 to 1

Which of the following is true of HVACR compressors?

A compressor cannot compress a liquid. A compressor is a device that is used to increase the pressure of vapor or gas. It increases the pressure of the working fluid at the expense of kinetic energy.

What can the service technician do to keep the refrigeration system operating at peak efficiency?

Clean the evaporator and condenser coils to keep pressures within design parameters. Dirty evaporator reduces the suction pressure of compressor. Dirty condenser cause compression ratio to rise. So, dirty evaporator and condenser leads to reduction in efficiency.

Because a scroll compressor's has fewer moving parts, it operates much quieter than other compressor designs and technologies.

Due to the small number of moving parts, scroll compressors have a quieter operation than other types of compressors. These compressors are usually 5 to 15 dBA quieter than other types of compressors. These compressors generate very low vibrations.

Rotary compressors have no "clearance volume." TRUE OR FALSE

TRUE Since the clearance volume for a rotary compressor is negligible, its volumetric efficiency is high compared to the reciprocating compressor.

List the three main advantages of having digital capacity control on a scroll compressor.

This makes the system more efficient. • Helps in maintaining correct humidity and temperature levels. • Increasing the life of compressor.

A __________ compressor is usually considered to be a low-side device because the suction gas is vented to the inside of the shell, including the crankcase.

hermetic Hermetic compressor is the compressor contained in the housing and is fully welded. It is considered to be low side.

he screw-type compressor is used primarily in ____

large industrial refrigeration and air-conditioning systems

Which compressor type uses pistons to compress the gas?

In reciprocating compressors, piston and cylinder components are used to compress the refrigerant gas. reciprocating

Top Dead Center

When the piston reaches the top of its compression stroke, it is called

Scroll compressor operation is relatively simple. Two spiral-shaped scrolls fit inside one another, One of the spiral-shaped parts stays stationary while the other one does What?

orbits around the stationary member. ALSO REFERRED TO AS RADIAL MOVEMENT

A direct-drive compressor typically runs at _______ rpm.

1750 or 3450 Direct drive compressor rotates at the same speed of motor. Its speed is ranges between 1750 rpm and 3450 rpm.

Rotary compressors have pistons that rotate inside the cylinders.

A rotary compressor includes a compression mechanism in which a piston is disposed inside a cylinder chamber of a cylinder. The cylinder and the piston eccentrically rotate relative to each other

The scroll compressor is one type of reciprocating compressor. TRUE OR FALSE

FALSE THEY ARE ENTIRELY DIFFERENT COMPRESSORS

Which is not a pressure or force acting on a TXV diaphragm?

Head pressure The pressures acting on the TXV diaphragm are evaporator pressure, spring pressure and bulb pressure. Head pressure will not be acting on TXV diaphragm.

List the main advantage that a discus compressor's valve plate design has over a conventional piston-type compressor.

If the clearance volume of the compressor cylinder is decreased, then the efficiency of the compressor will increase. Discus valve is designed in such a way that it permits close tolerance at the top dead center of the cylinder. This close tolerance helps in reducing the cylinders clearance volume thereby increasing the compressors efficiency. The discus valve also is designed with a large bore which helps in clearing compressed refrigerant in less time.

List four main advantages a scroll compressor has over a conventional piston-type compressor

In Scroll compressors, the compression process is continuous and quieter. • Since the scroll compressor do not valves, they even do not have any valve losses. • Scroll compressor has better volumetric efficiency over reciprocating compressor as there is no re-expansion of gas. • Radial movement of Scroll compressor allows the correct amount of contact force thereby eliminating high-stress situations between mating scrolls. Such action allows the compressor to handle small amount of liquid.

Which compressor type uses tapered, machined gear components to trap the gas for compression?

In screw compressors the refrigerant gas is compressed by squeezing the gas that is trapped in-between the two screw type gears.

What would be done to increase the compressor speed on a belt-driven compressor?

Increase drive pulley size Generally, compressors are driven by motors. Pulleys are mounted to the shafts of motor and compressor. Power transmission is done by a belt drive from motor to compressor. Speed of the compressor can be varied by changing the size of the drive pulley. To increase the speed of the compressor the size of the drive pulley size needs to be increased.

What effect does a slight amount of liquid refrigerant have on a compressor over a long period of time?

It dilutes the oil and causes wear on any moving parts. Compressor is made for compression of vapor or gas. Liquids are incompressible. If small amount of refrigerant liquid enters in compressor, they dilute the oil and causes wear of any part.

What lubricates the refrigeration compressor?

Oil Refrigerant is working fluid in refrigeration and air conditioning. If moisture present in refrigeration and air conditioning system, it hampers the performance of expansion valve. Desiccant is a hygroscopic substance used as a drying agent, used to remove moisture from refrigeration and air conditioning system.

Which style of compressor uses belts to turn the compressor?

Open belt drives are used to transmit power in compressors.

What would be considered a higher-than-normal temperature for a discharge gas line on a reciprocating compressor?

Overheating of reciprocating compressor is the common reason for its early failure. A temperature of 225°F and above can be considered as the temperature, higher than the normal temperature at the discharge gas line of a reciprocating compressor. 225*F

The sight glass on a semi-hermetic compressor is used to allow light to enter the crankcase to keep the oil warm.

SIGHT GLASSES ON SEMI HERMETIC COMPRESSORS. are to visually Inspect media or fluids for changes in color or consistency Observe the liquid levels in a tank

Briefly describe how the scroll compressor compresses refrigerant gas.

Scroll compressor consists of two involute, spiral shaped mating parts called scrolls. One of the scrolls is stationary, over which another scroll moves in orbital motion. This orbital motion compresses pockets of gas and discharges it out of a port in the stationary scroll.

Briefly describe how the digital capacity control for a scroll compressor works.

Similarly, when the solenoid valve is de-energized, the two scrolls will be axially joined, and the compressor achieves 100% capacity. So, by energizing/ de-energizing the solenoid from time-to-time different compressing capacities are achieved

Scroll compressors are becoming popular because they can handle liquid flood back without compressor damage. TRUE OR FALSE

TRUE When liquid refrigerant, oil, or small solid particles enter between the two scrolls, the mating scroll parts can actually move apart in a sideways direction. This is referred to as "radial" movement.

Which best describes the function of a compressor?

The compressor increases the pressure in the system from the low-side pressure to the high-side pressure. Compressor is considered as heart of refrigeration system. Compressor function is to increase pressure of the refrigerant.

Which of the following design factors can affect the efficiency of a reciprocating compressor?

The valve plate design and clearance volume. Compressor efficiency determined by its valve plate design. Re- expansion of refrigerant from clearance volume decreases compressor design

A bolted together motor-compressor assembly is sometimes referred to as a semi-hermetic type.

True

Open-drive compressors are manufactured with the motor external to the compressor shell. The crankcase shaft seal must be able to hold refrigerant inside the compressor. Which of the following is a suitable material for this seal?

ceramic

Which terminal combinations would show an open circuit if the internal overload device in a hermetic compressor should open due to excessive heat?

common to start start to run

if the suction valve in a reciprocating compressor is leaking slightly what can happen?

cooling capacity will be reduced compressor can overheat

Which of the following parts of a reciprocating compressor transmits the circular motion of the motor and changes this motion to back and forth (reciprocating) for the pistons?

crankshaft As the motor shaft rotates, the crankshaft also performs a rotary motion which gives the piston the ability to carry out its reciprocating motion inside the cylinder.

Rotary compressors are used primarily in ____.

domestic refrigerators Small rotary compressors such as rolling piston type and rotating vane type are used in domestic refrigerators and freezers.

What are two main reasons why a compressor should have modulating capacity control?

he main reasons for modulating compressors are • To reduce consumption of power • To properly control dehumidification

A piston, connecting rod, crankshaft, valves, valve plate, head, shaft seal, internal motor overload device, pilot duty motor overload device, and coupling are parts that may be found in a ___________ compressor.

reciprocating A reciprocating compressor houses a vast array of moving parts. Major components of reciprocating compressor are crankshaft, connecting rod, piston, valve, valve plate, head, motor, motor overload device and coupling.

Five types of compressors are _____________.

reciprocating, rotary, scroll, screw, and centrifugal In refrigeration and air conditioning system, types of compressors used are reciprocating, screw, rotary, scroll and centrifugal.

The needle and seat of a TXV are normally made of ________.

stainless steel The needle and seat will be controlling the flow of refrigerant via valve. They will be used as metering device which will maintain the flow control of refrigerator. It will be made-up of extremely hard material with corrosion resistance. Stainless-steel will be utilized to manufacture of needle.

The temperature of the compressed gas leaving the compressor is usually referred to as

very warm or super heated