The author refers to the importance of the cooling system within the structure or energy matrix of any installation.
by René Ruano Domínguez*
Refrigeration systems are classified as those with the greatest presence in any economic sector, standing out in the residential where they occupy the first place among energy consumers.
Therefore, the chain of operations on these energy systems (from the design stage to their exploitation) and the subsequent consequences of how to do it, fully impacts our planet and the climate change that is experienced, being an important consumer of electricity. It coincides that the generation of electricity is the process of energy transformation that emits the largest amount of GHG worldwide, standing out among them the CO2 gas.
Hence, the dissemination of energy knowledge about these systems and in which components to act, facilitates and promotes good actions on their efficiency with a global reach.
The cooling system is defined as a closed system, in which the process of absorption and release of heat is carried out by means of a refrigerant that flows in a vapor compression cycle. To perform the compression work that the cooling system does, it requires energy consumption and the most common is to find that the compressor is driven by an electric motor.
Cooling assemblies that are powered by internal combustion engines are less frequent than those driven by electricity. The same goes for cooling assemblies powered by absorption generators that employ fuel burners, or solar collectors.
These energy systems are closely linked to our daily lives. Refrigeration is present in all sectors of the economy and society. In the residential sector, domestic refrigeration systems are common in most homes and reach even the largest industrial facilities and large buildings.
At the pace with the development of the standard of living of humanity, every day that passes the use of residential refrigeration increases, highlighting in the growth the individual, sectorized and centralized air conditioning, and in the diversification of domestic refrigerated furniture, adding energy consumption to the individual electricity bill, both to freeze and preserve food, how to condition the interior environment of the premises in the winter season and in the summer season.
In the commercial sector, refrigeration ensures the preservation and freezing of food. These systems are part of the process of exhibition and sale in large, medium and small shopping centers. We know the furniture, counters, freezers, bottle racks and refrigerated consoles.
In the transportation and distribution of food, both land, sea and air, refrigeration guarantees freezing and preservation during the crossing.
The storage of food is carried out in refrigerated chambers, both for freezing and for the preservation of the same. Isolated chambers are also used where the ice produced in a cooling system is placed, in its different forms, such as blocks of ice of different dimensions. Ice in cube or tube form is used for the cooling of bottled beverages, or if it meets the established sanitary conditions, for the cooling of direct liquids. Flake ice is mainly used in the fishing industry, as its structure in the form of chips and scales facilitates greater surface contact of the stowage or loads of the fish when deposited in the boxes. The conservation of catches in fisheries requires guarantees that the fish arrives fresh in a safe port.
In the high-tech industry, such as biotechnology, pharmaceuticals, genetics, electronics, computer science (hard and software), drug manufacturing, refrigeration is very typical of the process and air conditioning ensures the quality of the indoor environment of the premises. In the health sector, hospitals, clinics and laboratories would not function without air conditioning. Without it, it is not appropriate to perform operations in the operating rooms, the intensive care rooms and the clinical diagnostic departments would not work.
In the tourism sector it is essential to guarantee the quality of the hotel service. In administration and office buildings, etc.
Higher energy consumption
In short, we are in the presence of the energy system of greater use in the daily life of all of us due to its wide diffusion, so we can conclude that it is a globalized system. Therefore, the operation of this energy system and its subsequent consequences, fully impacts our planet.
For good, it is a system that is available to the vast majority due to its wide use in our daily lives. This form or particularity makes it easier for many of us to act positively, if we know how to do it. And that is the main objective of this article, to highlight that these systems are energy intensive and to promote around them the practical solutions for an efficient operation.
The electricity consumption of refrigeration systems and the efficiency of their use will depend on many factors, all very close to our decisions. There are factors that classify as specific to the process that is carried out, others are associated with the way of operation of the system, also influences the efficiency of the factors linked to the technical state of the equipment.
The indicators or intensity of consumption per refrigeration unit vary depending on the operating temperature of the refrigeration system. Thus, systems that operate at low evaporation temperatures have a higher indicator than those of medium and high evaporation temperature.
It is no less important to know that they also influence the efficiency of energy consumption, the factors that we can classify as external to the cooling system, such as environmental conditions, the orientation and location of the system components in the installation area, the parameters with which the equipment has been selected and has been acquired, in the latter group mainly the parameters relating to the load/capacity regime.
In any scheme of consumption - distribution and use of electricity, refrigeration and air conditioning systems can represent between 30 and 50% in the structure of consumption. We know that large consumers of electricity are also large emitters of CO2 into the atmosphere, a closely linked issue, hence we are facing one of the cooling systems where our personal and collective action can influence improvements in the bill, the economy and environmental decontamination.
In short, the cooling system is a closed system, where a compression process of a refrigerant gas is carried out cyclically, which can be driven by an electric motor, or by an internal combustion engine, or by a heat generator. We have known that these systems are great consumers of energy during their operation and therefore, powerful emitters of CO2 into the atmosphere. We also learned that because of its wide dissemination in all sectors of the economy and society, the vast majority of us can act positively on its efficiency, if we know how to do it.
There are several components involved in a cooling system and their operating behaviors directly influence the energy efficiency of the whole. They all carry out an energetic, transformational, transport or exchange process. That is why it is important to know their strengths and weaknesses, how to treat them and make them work correctly and harmoniously. In its simplest form, a cooling system consists of five mechanical components: Compressor, Condenser, Evaporator, Expansion Device and Pipes.
Two components that are part of the system and that cannot be overlooked are the energy carrier that exchanges heat or refrigerant gas and man, who designs, projects, selects, operates, maintains and controls this type of energy system, which as we have known before, are high energy consumers.
Finally, according to the type and complexity of the cooling system, we find different auxiliary means integrated into the system, which in turn intervene in an efficient operation. Among them we have measuring and control instruments, such as pressure gauges and thermometers, indicators and recorders, ammeters and voltmeters to measure the parameters of electric current and flow meters.
Other auxiliary means are filters, coolant storage tank, liquid visors, oil level visors, overpressure valves, etc. Also, for systems that use cooling water in condensation, or cool water, the Chemical Water Treatment (TQA) system is present. The TQA system is integrated into the cooling system, merging so to speak, since its behavior and technical state will directly influence the energy efficiency of the cooling system.
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Components of a cooling system
- Compressor: It is the heart of the system as it moves the flow of refrigerant. Its function is to receive refrigerant steam at low pressure (and temperature) from the evaporator and compress it at high pressure (and temperature). The high-pressure vapor is converted to liquid phase in the condenser.
- Capacitor: The condenser absorbs the heat brought by the refrigerant vapor at high pressure and transfers it to the forced air it receives from the fans, or to the cooling water, depending on whether it is air or water cooling. The refrigerant vapor condenses inside this exchanger, passing into the liquid phase.
- Expansion Device: In the liquid phase the refrigerant is usually stored and then reaches the expansion valve. The liquid, which remains at high pressure before the valve, is strangled as it passes through this device and expanded, transforming into a gaseous liquid mixture at low pressure. This device separates the high zone from the low pressure.
- Evaporator: It is the equipment where the evaporation of the liquid refrigerant - gas mixture concludes, absorbing heat from the medium that is being cooled. All refrigerant must pass into the steam state. Leaving the evaporator, already in the form of steam, with a low pressure and temperature, the refrigerant returns to the suction of the compressor to be compressed and reheated. Of course, the communication of the equipment for the transport of refrigerant is carried out through pipe ducts, which require in some areas of the system, thermal insulation. Since the expansion device regulates the flow of refrigerant to the evaporator, its selection is of particular importance for the subsequent operation of the cooling system.
* He has more than 35 years of experience in actions in energy systems and equipment, both in those that use fossil energy and renewable sources. He started as an operator, later a technologist and technical manager in the fuel conversion and refining industry. He has been founder and technical manager of several energy engineering teams aimed at the project, assembly and technical services in heat and cold systems. He has carried out multiple actions in projects, execution and services of general energy engineering. He is the founder and Principal Engineer of General Energy Engineering. ([email protected] - www.energianow.com).
