Unit 36: Refrigeration Applied to Air-Conditioning

Radial sealing on a scroll compressor is typically accomplished with

a. oil.

Which of the following is true regarding the rotary compressor?

c. There is no clearance volume on these compressors.

Each degree of condenser subcooling will increase system efficiency by approximately how much?

a. 1%

The maximum desired discharge line temperature for an R-410A compressor is

a. 175°F.

At or near design conditions the supply and return temperatures for an air-conditioning system are closest to

a. 55°F supply air, 75°F return air.

Multicircuit evaporators are equipped with which of the following components?

a. A refrigerant distributor located at the outlet of the metering device.

What feature on a thermostatic expansion valve allows the system pressures to equalize during the off-cycle?

a. Bleed port

Heat leaks into a structure by which three methods?

a. Conduction, infiltration, and radiation

When sizing and selecting air-conditioning equipment, which of the following must be taken into account?

a. Moisture content

Which of the following best describes the scrolls in a scroll compressor?

a. One scroll is stationary and one scroll orbits.

What refrigerant lines are field installed on the typical package-type air-conditioning unit?

a. Package-type equipment has no field-installed refrigerant lines.

Package-type air-conditioning units are intended to be located

a. either on the roof of a structure or at ground level.

The suction line is insulated to

c. prevent the vapor refrigerant in the line from absorbing additional, unwanted heat.

The refrigerant that both enters and leaves a properly operating compressor can best be described as

c. superheated vapor.

Which of the following is a possible condenser saturation temperature for an R-410A air-conditioning system that is operating with an outside ambient temperature of 90°F?

d. 120°F

Which of the following best describes the air that enters the structure after being treated by an evaporative cooler?

d. Cool and humid

Which of the following best describes the refrigerant at the outlet of the condenser?

d. High-pressure liquid

What refrigerant lines are field installed on the typical split-type air-conditioning system?

d. Liquid line and suction line

Air-conditioning is often referred to as

d. comfort cooling.

The condensing unit of a split-type air-conditioning system is made up of the

d. condenser coil and compressor.

Thermostatic expansion valves are designed to maintain constant

d. evaporator superheat.

A typical multihead, ductless split system is configured with

d. multiple indoor units and one outdoor unit.

The two types of heat transfer that are facilitated by the evaporator are

d. sensible heat and latent heat.

Three common evaporator coil configurations found on air-conditioning systems are

d. slant, A, and H.

The compressor type that relies on pistons moving up and down within cylinders is the

a. reciprocating compressor.

As refrigerant undergoes the compression process

a. the pressure and temperature of the refrigerant increase.

All of the following are true regarding the scroll compressor except

a. there is a clearance volume that traps some refrigerant.

Reciprocating compressors used in residential applications are most likely to be

b. fully hermetic, suction-gas-cooled pumps.

Discharge gas temperature is affected most by

b. the temperature of the suction gas.

If a duct system is uninsulated and runs through the conditioned space

b. there will be no net duct losses while the system is operating in either the cooling or heating mode.

Referring to Figure 36.18, the 1% design wet-bulb and dry-bulb temperatures for Napa, California in the summer are

c. 100°F dry-bulb, 71°F wet-bulb.

Air-conditioning is classified as which type of refrigeration?

c. High temperature

Evaporative cooling systems are best-suited for which type of climate?

c. Hot, dry climate

On average, each ton of system capacity has the ability to remove approximately how much moisture from the air?

c. One quart

The temperature of the evaporator coil is affected

c. by both the temperature and amount of air passing through the coil

Rotary compressors are built with

c. only discharge valves.