Improvements have been made and will continue to be made in insulation, compressor efficiency, evaporator and condenser heat transfer, fans and other refrigerator components.
Refrigerators produce a cooling effect because they contain an evaporating liquid within them. Refrigerators continually cause this liquid to evaporate, and the evaporation draws heat from the inside of the refrigerator. This causes the interior to cool.
Other cooling methods include air circulation machines used in aircraft; vortex tubes for local cooling in the presence of compressed air; and thermoacoustic refrigeration, which uses sound waves in compressed gas to control heat transfer and heat transfer; vapor jet refrigeration, Air conditioning in large buildings popular in the early 1930s; thermoelastic cooling using smart metal alloys that stretch and relax.
For example, air-cooled gas coolers use air to cool the CO2 refrigerant gas in a closed system. In the gas cycle, the cooling effect is equal to the product of the specific heat of the gas and the temperature rise of the gas on the low temperature side.
The Mechanism of a Refrigerator’s Action
The work done by the compressor on the gas (causing an exothermic phase change in the gas) is then converted into heat and released into the indoor air outside the refrigerator. Freon’s job is done by the compressor, Freon gives off heat to the air outside the refrigerator (as it undergoes exothermic condensation from gas to liquid).
This endothermic process causes freons to absorb heat from the air inside the refrigerator, thereby cooling the refrigerator. When heat is transferred from a warmer area to a cooler area, the heat is absorbed by the liquid freon (from inside the refrigerator), causing the temperature inside the refrigerator to drop.
This heat loss causes the gas to condense into a high pressure liquid which can be fed to the metering device. The refrigerant then enters the condenser, which turns the vapor into a liquid and absorbs some of the heat. The refrigerant then enters the expansion valve, where it expands, losing pressure and heat. The expansion valve helps reduce the pressure and temperature of the refrigerant.
The heat from the refrigerator flows to the coolant ([math]Q_C[/math]), lowering the temperature inside. As soon as the refrigerator cools down below the set temperature, the compressor will turn off. The refrigerator switches heat from cold to hot, doing work that cools the space inside the refrigerator.
Heat Transfer from Refrigerators
Basically, this is how refrigerators transfer heat from their refrigerator cabinet to the room outside. They turn a liquid into a gas inside the refrigerator (to collect heat from stored food), pump it out of the cabinet and turn it back into a liquid (to transfer heat to the outside).
Inside the refrigerator (1), we turn the liquid into a gas to collect the heat inside the refrigerator (2), pump it out of the car, and then turn it back into a liquid to give up our heat there (3). As we have just seen, the refrigerator works by “sucking” the heat from the coolant cabinet and then pumping the liquid out of the cabinet where it releases its heat.
Refrigerators utilize the principles of pressure, condensation, and liquid evaporation in a closed loop to remove heat and lower the temperature inside the refrigerator. The condenser then cools the refrigerant, turning it into a liquid state.
Air-cooled condensers include fans to move air through pipes and fins to remove heat from the refrigerant. The condenser is the high pressure component of the refrigeration circuit that allows the high temperature and high-pressure refrigerant gas to dissipate the latent heat of condensation to the environment.
The cool air produced in the refrigerator’s condenser area is circulated throughout the refrigerator to aid in cooling. Natural convection condensers use natural airflow to cool the refrigerant, while forced convection condensers use fans to draw in cool air.
How Waste Heat Is Managed
To utilize the waste heat of a gas engine, a combined ejector/heat pump compressor-refrigeration system is used. In the heat exchangers (EX1 – 14% and EX2 – 14%), the waste heat from the exhaust gases is transferred to the recirculated water and then to the coolant in the generator sections G1 and G4.
The exhaust gas is cooled down to below 70°C to allow the water vapor contained in the exhaust gas to condense and use a higher heating value than natural gas. Evaporation of the refrigerant in the generator occurs at 85°C and 110°C.
The compressor can be operated in a positive suction pressure system or under vacuum, depending on the refrigerant used and the desired operating temperature of the evaporator. Screw compressors are commonly and effectively used in systems with a cooling capacity of more than 20 tons.
Typically, in trigeneration systems, waste heat is used to produce chilled water using an absorption chiller system. In Europe and especially in Germany, simple hydrocarbon compounds are used in small quantities for household refrigerators.
The Need for Refrigerators
Refrigerators are a necessary aspect of modern life, but most are based on a refrigeration mechanism called vapor compression, and the vapors used tend to be potent greenhouse gases that can contribute to global warming when released into the atmosphere.
The refrigeration industry has explored ways to reduce its environmental impact, such as testing cleaner gases, but there has not been a major shift to radical new refrigeration systems.
The Fluid Movements in Refrigerators
These improvements increase the subcooling of the refrigerant, increase the heat transfer rate and reduce the oval size of the condenser. In absorption systems, the compressor is replaced by an absorber that dissolves the refrigerant in a suitable liquid, a pressurized liquid pump, and a generator that removes refrigerant vapor from the high-pressure liquid by heating.
The cold mixture of liquid and vapor then passes through the evaporator coils or tubes and is fully evaporated by cooling the hot air (from the refrigerated space) that is blown through the evaporator coils or tubes by a fan. The liquid is now at low pressure (due to expansion) and a lower (cold) temperature than the air inside the refrigerator. When the hot air in the coil meets the cooler air temperature in the kitchen, it turns into a liquid. When the gas cools the cargo, it absorbs the heat, converting it into a gas.
The gas is then forced back into the compressor where it can restart the cycle. It enters the evaporator in a liquid state, where heat exchange takes place, thus cooling the cargo inside the refrigerator. It acts as a heat exchange medium from the stored products (load) to the refrigerant. The coolant must pass through all these components and is modified in each of them to reach the required temperatures.
And suppose you filled a tube with a carefully chosen chemical (with a low boiling point) that easily switches between a liquid and a gas known as a refrigerant or refrigerant. Inside the refrigerator, we can suddenly expand the pipe so that the refrigerant expands into a gas and cools the refrigerator compartment as it passes through it. Outside of the refrigerator, we might have something like a bicycle pump that compresses a gas, releases its heat, and turns it back into a liquid.