Table of Contents
What are three reasons why ice melts in an icebox?
The first reason behind the melting of ice in an icebox is absorption of heat from the food by the ice and results in melting. The second reason is heat leakage due to entering of warmer air inside the ice box leads to the melting of an icebox.
What are three types of temperature ranges of refrigeration?
They are also categorized by temperature ranges: low temperature (32°F and below), medium temperature (32°F to 40°F), and high temperature (40°F to 50°F).
What are the approximate temperature ranges for medium temperature refrigeration applications?
Most of the commercial refrigeration application operates in range of 35° F to 40°F for medium-temperature units and 0° F to -10°F for low-temperature units.
What changes of state occur in the refrigerant of a refrigerator quizlet?
The hot gas from the compressor is desuperheated. The refrigerant is condensed from a vapor to a liquid.
What is a subcooled liquid?
Subcooling is defined as the difference between the measured liquid temperature and the liquid saturation temperature at a given pressure. Total liquid subcooling occurs from the start of the 100% saturated liquid point in the condenser to the metering device.
Where does flash gas occur?
In an evaporator, flash gas occurs from the pressure drop between the high side and low side of the system. This pressure drop allows flash gas to absorb heat, which helps to cool the rest of the liquid refrigerant.
What happens when room temperature soda is poured into a glass of ice?
What happens when room temperature soda is poured into a glass of ice? The ice melts because it is absorbing heat from the soda.
What should the superheat be?
Superheat for most systems should be approximately 10F measured at the evaporator; 20°F to 25°F near the compressor. If the suction pressure is 45 psi, (which converts to 22°F) and the suction temp is 32°F, the system still has 10°F of superheat.
What component Cannot be flushed?
Accumulators, receiver driers, lines and hoses with filters and mufflers CANNOT be flushed and must be replaced. Most modern flat-tube multi-pass and flat-tube serpentine condensers have tiny internal passageways and CANNOT be flushed.
What causes flash gas in the evaporator?
If the pipes are too thin and long, loss of pressure and friction tend to occur. If the evaporator is too high above the receiver, the rising pipes produce a small amount of vacuum at the topmost portion, making the fluid to undergo ebullition and produce flash-gas.
What is the difference between the oxygen we breathe?
Terms in this set (30) What is the difference between the oxygen we breathe and the ozone located in the earth’s atmosphere ? The ozone molecules we breathe contain 2 atoms of oxygen, written O2 ; ozone molecules contain 3 atoms of oxygen .
What is the heat called that changes a refrigerant from a liquid to a vapor?
Vaporization. As the refrigerant boils, it changes state from liquid to vapor. As mentioned in the review, this process is also called vaporization, as the refrigerant is changing from liquid to vapor.
Why does refrigerant need to change states?
Coolant gases have the capacity to draw in heat from the surrounding environment. When used in a mechanical refrigeration system, a source of energy, usually electricity, is used to force the gas to change state. This change in state affects the air surrounding the gas.
What are the three refrigeration processes that happen in the condenser?
The function of the condenser in a refrigeration system is to transfer heat from the refrigerant to another medium, such as air and/or water. By rejecting heat, the gaseous refrigerant condenses to liquid inside the condenser. The major types of condensers used are (1) water-cooled, (2) air-cooled, and (3) evaporative.
What are the 4 major components of the refrigeration cycle?
The 4 Main Refrigeration Cycle Components The compressor. The condenser. The expansion device. The evaporator.
What is subcooling in Vcrs?
Subcooling and superheating: In actual refrigeration cycles, the temperature of the heat sink will be several degrees lower than the condensing temperature to facilitate heat transfer. In such a case, the exit condition of the condenser will be in the subcooled liquid region. Hence this process is known as subcooling.
How do you do subcooling?
Calculate the subcooling as follows: subcooling = CT – T. For a refrigerant blend use the saturated liquid (bubble) temperature as the condensing temperature. Subcooling will not usually occur in the condenser unless liquid backs up in the condenser.
Can water be superheated?
Superheated water is liquid water under pressure at temperatures between the usual boiling point, 100 °C (212 °F) and the critical temperature, 374 °C (705 °F). Over the superheated temperature range the hydrogen bonds break, changing the properties more than usually expected by increasing temperature alone.
What is superheat?
Superheat is a measurement of the temperature a vapour is above its saturation or boiling point. Superheat can be measured in any vapour such as steam or refrigerant. There are two important superheat readings that can be taken on a system.
What is temp Glide?
The total temperature glide of a refrigerant blend is defined as the temperature difference between the saturated vapor temperature and the saturated liquid temperature at a constant pressure. In the condenser, the refrigerant changes phase (condenses) from a vapor to a liquid.
What is refrigeration effect?
Refrigeration effect is an important term in refrigeration that defines the amount of cooling produced by a system. This cooling is obtained at the expense of some form of energy.
When the refrigerant leaves the metering device it is not 100% liquid Why?
When the refrigerant leaves the metering device, it is not 100% liquid. Why? Because flash gas occurs and causes the 100% liquid to turn into 25% vapor and 75% liquid. Rejects both sensible and latent heat from the refrigeration system.
When water at 212 boils it is only absorbing latent heat?
When water at 212 degrees Fahrenheit is boiling, it is only absorbing sensible heat. Water boils at 212 degrees Fahrenheit under standard conditions. The Fahrenheit scale is used in the English measurement system by the United States. The laws of thermodynamics can help us to understand what heat is all about.
How much is a ton of refrigeration?
A ton of refrigeration is a rate of heat transfer, not an amount of heat. One ton is equal to the heat absorbed in melting 2,000 pounds (1 ton) of ice at 32°F in 24 hours (1 day). This equates to 12,000 Btu/hr or 12,000 Btuh.
