Difference Between Air Conditioning and Refrigeration

Ans. Refrigerators are made up of a condenser, compressors, and evaporators all in one. AC, on the other hand, is made up of a compressor and a condenser that are separate from the evaporator.

In an air conditioner, the compressor and condenser are independent of the evaporator. However, in a refrigerator, the compressor and condenser are combined with an evaporator to form a single unit.

Ans. To function, mechanical refrigeration necessitates the use of a man-made heat exchange system. This exchange system aids in the removal of heat from a specific location. However, for operations, this exchange system may function differently. It can be either cyclic or non-cyclic, magnetic or thermoelectric.

It is entirely dependent on how you intend to use the refrigeration. When the refrigerant enters the cooling coil, it continuously converts to a vapour state and absorbs heat. CRAC (computer room air conditioner) is an example of mechanical refrigeration in action.

Ans. The process of lowering the temperature of an object is known as cooling. The refrigeration process, on the other hand, lowers the temperature of the object to that of its surroundings. As a result, it maintains this temperature throughout.

Refrigeration involves cooling down a space/substance/system to lower and/or maintain its temperature below the ambient one. In simpler terms, refrigeration is artificial (human-made) cooling. Cooling refers to the process of removal of heat that results in a lower temperature and/or phase change.

Ans. In the case of refrigeration, thermal energy is transferred from one region to another with a higher temperature. The case of an air conditioner, on the other hand, is entirely different because thermal energy is used to cool the air. However, thermal energy transfers from a high-temperature location to a low-temperature location in the natural flow of thermal energy.

As the name implies, an air conditioner is a device that cools down the air by removing heat from a specific location. Refrigeration, on the other hand, refers to the process of releasing hot air.

Ans. A refrigerator is made up of four major components that work together to keep it running. Evaporator, Compressor, Condenser, and Expansion Valve are the four components.

An evaporator (generally coil-shaped) is the part of a refrigerator that cools. The evaporator absorbs heat from the area where we want to keep the temperature stable and transfers it to the refrigerant.

After receiving heat from the evaporator, the refrigerant travels to the compressor, where it is compressed and its temperature rises as a result of the compression.

A condenser is similar to an evaporator in appearance. The temperature of the refrigeration fluid reaches the condenser (which may be either water-cooled or air-cooled). Its temperature is reduced to the ambient temperature in this location (heat which is sucked from the room or closed space is given away to the atmosphere at condenser)

After the condenser refrigerant arrives at the expansion valve (which is basically a throttling device). The pressure of the refrigerant is reduced here, lowering the temperature of the refrigerant below the atmospheric temperature. This cooled refrigerant is then supplied to the evaporator, and the cycle continues indefinitely.

Ans. There are mainly four stages of refrigeration which are:

• Stage 1: It involves the evaporator coil.
• Stage 2: It involves a compressor.
• Stage 3: It involves a condenser coil.
• Stage 4: It involves an expansion chamber.

Ans. The uses/application of air conditioning and refrigeration are as follows:

• Air Conditioning: Air Conditioning deals with maintaining the temperature of certain air capacity in surroundings and also helps to maintain humidity and purity.
• Refrigeration: Refrigeration deals with regulating the air temperature, it is used in freezing or cooling products.

Ans. \({\rm{COP\;of\;Carnot\;Heat\;pump}} = \frac{{{T_1}}}{{{T_1} - {T_2}}}\)

Calculation:

Given:

T₁ = 327° C = 600 K, T₂ = 27° C = 300 K

\(\therefore COP = \frac{{{T_1}}}{{{T_1} - {T_2}}}\)

\(\therefore COP = \frac{{600}}{{600 - 300}} = \frac{{600}}{{300}} = 2\)

<>∴ COP of Carnot heat pump = 2

Ans. Relative humidity is given by

\(ϕ = \frac{{{P_v}}}{{{P_{vs}}}}\)

where P _v is pressure of water vapour and P_vs is pressure of water vapour at saturation point.

For isothermal process:

PV = constant

Calculation:

Given:

ϕ₁ = 50%, P_v1

Since volume is reduced to half so the pressure has become twice.

P_v2 = 2P_v1

\(\frac{{{ϕ _2}}}{{{ϕ _1}}} = \frac{{{P_{{v_2}}}}}{{{P_{v1\;}}}}\)

\(\frac{{{ϕ _2}}}{{{ϕ _1}}} = 2\)

ϕ₂ = 2ϕ₁

ϕ₂ = 2 × 50 ⇒ 100%.

Ans. The characteristics of a good refrigerant should have the following properties

1. Low boiling point
2. High latent heat value
3. Low freezing point
4. Non-flammable and non-toxic
5. High di-electric strength
6. Not affected by moisture
7. Non-corrosive to metals
8. Mixes well with compressor oil

Ans. Wet bulb temperature: Temperature obtained by an accurate thermometer having a wick moistened with distilled water

Dew point temperature: Temperature at which the liquid droplets just appear when the moist air is cooled continuously.

Relative humidity along saturation line is 100%.

Basic Processes in Conditioning of Air:

Sensible heating: Moisture content of air remains constant so specific humidity is constant, temperature increases as it flows over a heating coil

Sensible cooling: Moisture content of air remains constant so specific humidity is constant, but its temperature decreases as it flows over a cooling coil

Cooling and dehumidification: When moist air is cooled below its dew-point by bringing it in contact with a cold surface, some of the water vapour in the air condenses and leaves the air stream as a liquid, as a result, both the temperature and humidity ratio of air decreases.

Heating and Humidification: During winter it is essential to heat and humidify the room air for comfort. It is done by first sensibly heating the air and then adding water vapour to the air stream through steam nozzles, as a result, both the temperature and humidity ratio of air increases.

Cooling & humidification: Air temperature drops and its humidity increases.

Heating and de-humidification: This process can be achieved by using a hygroscopic material, which absorbs the water vapour from the moisture. If this process is thermally isolated, then the enthalpy of air remains constant, as a result, the temperature of air increases.

Inlet (State 1): 35°C and 100% RH

Outlet (State 2): 25°C and 100% RH

Relative humidity is same but as the temperature is decreasing and specific humidity is also decreasing. So the process 1-2 is cooling and dehumidification process.

The name of the device is dehumidifier.