2022 ASHRAE Handbook—Refrigeration (SI Edition) - Practice Flashcards

Comprehensive practice flashcards covering the fundamentals of halocarbon, ammonia, and carbon dioxide refrigeration systems, including design principles and safety standards.

Refrigeration is defined as the process of moving __________ from one location to another by use of a refrigerant in a closed cycle.

heat

Halocarbon refrigerants are categorized into four groups: chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), __________, and hydrofluoroolefins (HFOs).

hydrofluorocarbons (HFCs)

The __________ Agreement, revised in $2016$, marks a commitment to regulate HFC refrigerants as controlled substances due to their global warming potential (GWP).

Kigali

Because halocarbon refrigerants are heavier than air, leak detection sensors should typically be placed __________ from the floor.

$$300\,mm$$

The recommended design velocity for a suction line is between __________.

$4.5$ to $20\,m/s$

Liquid drain lines from condensers to receivers should be sized for a velocity of __________ or less to ensure positive gravity flow.

$$0.5\,m/s$$

When sizing refrigerant lines, the system is typically sized for pressure losses of __________ or less for each segment of the discharge, suction, and liquid lines.

$$1\,K$$

The primary measure for determining pressure drops in refrigeration piping is a given change in __________.

saturation temperature

A __________ is used in the suction line to return oil at minimum loads without causing excessive pressure drop at full load.

double suction riser

In ammonia systems, the intermediate vessel between the high and low stages used to cool discharge gas and subcool high-pressure liquid is called a(n) __________.

intercooler

Ammonia has a specific acute toxicity exposure limit (ATEL) of __________ according to ANSI/ASHRAE Standard $34$-$2019$.

$$320\,mg/kg$$

The phenomenon in two-phase ammonia systems where gas is compressed until it condenses and allows a liquid slug to impact an end cap is called __________.

condensation-induced hydraulic shock (CIHS)

The temperature at which $CO_2$ (R-$744$) reaches its critical point is __________.

$$31°C$$

The equilibrium point where solid, liquid, and vapor states of $CO_2$ coexist is known as the __________.

triple point

In a __________ cycle, the compressor raises the operating pressure above the critical pressure and heat is rejected by cooling the gas without condensation.

transcritical

The reaction between ammonia and carbon dioxide resulting from internal leakage in a cascade heat exchanger typically forms a white crystalline salt called __________.

ammonium carbamate

In a liquid overfeed system, the mass ratio of liquid delivered to the evaporator to the amount of liquid vaporized is called the __________.

circulating rate

A(n) __________ receiver allows liquid to flow to the expansion valve without exposure to refrigeration in the receiver, keeping it subcooled.

surge-type

The behavior of zeotropic blended refrigerants where phase change occurs over a range of temperatures is known as __________.

temperature glide

When calculating superheating at the evaporator exit for a zeotropic refrigerant, the __________ temperature represents the saturation point.

dew-point