Refrigeration Systems & Components Flashcards

Which type of condenser is most commonly used in large commercial and industrial refrigeration systems where water conservation is important and ambient air temperature is high?

Answer: Evaporative condenser

Evaporative condensers use a combination of sensible heat transfer and evaporative cooling of water sprayed over the coil, achieving lower condensing temperatures than air-cooled units in high-ambient conditions while using less water than shell-and-tube condensers.

What is the effect of non-condensable gases (such as air or nitrogen) in the refrigerant circuit on system performance?

Answer: They raise condensing pressure and temperature without adding to refrigeration effect

Non-condensable gases accumulate in the condenser, occupying volume and raising head pressure without condensing, which increases compressor work and discharge temperature while reducing capacity.

A flooded evaporator differs from a direct-expansion (DX) evaporator primarily because:

Answer: The tube bundle is immersed in liquid refrigerant with refrigerant boiling on the outside of the tubes

In a flooded evaporator, the refrigerant pool surrounds the heat transfer tubes, and the process fluid flows inside the tubes, allowing high nucleate boiling heat transfer coefficients without the need for superheat control.

Frost accumulation on a refrigeration evaporator coil primarily causes:

Answer: Reduced airflow and heat transfer, decreasing system capacity

Ice acts as an insulating barrier between the air and the refrigerant, restricting airflow through the coil and reducing heat transfer, causing the coil temperature to drop further while system capacity falls.

In a shell-and-tube condenser used with a water-cooled refrigeration system, scale buildup on the water-side tubes will result in:

Answer: Higher condensing pressure, increased compressor work, and higher discharge temperature

Scale acts as an insulator on tube walls, reducing the overall heat transfer coefficient and forcing condensing pressure to rise so the refrigerant can still reject heat to the condenser water.

What is the purpose of a liquid-suction heat exchanger (LSHX) in a refrigeration system?

Answer: To subcool liquid refrigerant while superheating suction gas, improving system efficiency

An LSHX transfers heat from warm liquid refrigerant (subcooling it to prevent flash gas) to cold suction vapor (superheating it to protect the compressor), simultaneously improving both capacity and compressor protection.

A plate-and-frame heat exchanger used as an evaporator in a glycol secondary loop system offers which primary advantage over a shell-and-tube design?

Answer: Higher heat transfer coefficients in a more compact design with easily cleanable plates

Plate-and-frame heat exchangers provide very high surface area per unit volume and turbulent flow conditions that yield superior heat transfer coefficients, making them compact and efficient for glycol chilling applications.