313A Evaporators and Condensers

Question 1

What is the temperature difference (TD) across an evaporator and what does it indicate?

Accepted Answer

The difference between the air temperature entering the evaporator and the refrigerant saturation temperature; it indicates proper coil sizing and airflow

Answer

The difference between refrigerant discharge and suction temperatures

Answer

The difference between indoor and outdoor temperatures

Answer

The temperature change of the refrigerant through the compressor

Question 2

What is the difference between a fin-and-tube evaporator and a plate evaporator?

Accepted Answer

A fin-and-tube uses tubes with attached fins for air-cooled applications; a plate evaporator uses stacked plates for liquid-cooled or direct-contact applications

Answer

They use different refrigerants

Answer

A fin-and-tube is for heating only; a plate is for cooling only

Answer

There is no significant difference

Question 3

What causes frost buildup on an evaporator coil and what problems does it create?

Accepted Answer

Operating below the dewpoint of the air combined with coil temperatures below 0°C; it insulates the coil, blocks airflow, and reduces capacity

Answer

High ambient temperature; it improves cooling

Answer

Excess oil in the system; it causes noise

Answer

High refrigerant charge; it causes high efficiency

Question 4

What is the approach temperature on a water-cooled condenser?

Accepted Answer

The difference between the refrigerant condensing temperature and the leaving water temperature; indicates condenser efficiency

Answer

The temperature of the water entering the cooling tower

Answer

The outdoor air temperature approaching the unit

Answer

The temperature drop across the water pump

Question 5

What are the three types of condensers used in HVAC systems?

Accepted Answer

Air-cooled, water-cooled, and evaporative condensers

Answer

Plate, shell, and tube

Answer

Horizontal, vertical, and diagonal

Answer

Primary, secondary, and tertiary

Question 6

Why is it important to keep condenser coils clean?

Accepted Answer

Dirty coils increase head pressure, reduce system capacity, increase energy consumption, and can cause compressor overheating and failure

Answer

Clean coils look more professional

Answer

Clean coils only affect noise levels

Answer

Dirty coils have no significant impact on performance