Cooling

In 1913, Escher Wyss first used monochloromethane as a working substance in a refrigeration unit. In the 1920s, serial production of household refrigerators with monochloromethane or sulfur dioxide as a working substance began. The freons in 1945 became the most important working substance in refrigeration, and they retain that meaning to this day. Constant cooling in technical cooling is achieved by circulating the working substance in a closed system in which the working substance evaporates (the working substance has a low evaporation temperature) and then condenses again in continuous cycles. If no leakage occurs, the working substance retains its properties throughout the life of the refrigeration unit and does not need to be replaced. All that is required to maintain the cooling effect is the constant supply of energy or power to the system, and the ability to remove heat from the system. Circular processes in refrigeration are left-handed processes with the consumption of compensatory energy, which is brought to the process most often as mechanical work. We distinguish three types of such processes. When the process transfers heat from lower to higher ambient temperature, the process is called a cooling process. When heat is transferred from the environment to a higher temperature by a circular process, such a process is called a heating process or a heat pump. The third type of left-hand circular processes consists of processes in which heat is transferred from low to high heating temperature, tkz, with the expense of mechanical work. heating and cooling processes. The two basic types of refrigeration systems are compression refrigeration and absorption refrigeration.
Each compression system is made up of four basic elements, namely: A compressor that operates the substance from evaporation pressure to condensation pressure in order to raise its temperature above ambient temperature. This increases the temperature and pressure of the working substance. When the temperature rises to the required amount, the heat exchange with the environment is enabled. The compressors are divided into airtight, semi-airtight and open air compressors. The condenser hot steam of the working substance from the compressor is first cooled, condensed, and cooled before leaving the condenser. According to the cooling method, the condensers are divided into water-cooled, air-cooled, and combined, water and air-cooled condensers. The damping valve doses and dampens the working substance from the condensing pressure to the evaporation pressure. The liquid substance passes through the throttle valve from the high pressure area to the lower pressure area. As a result, the working substance expands and evaporates at the same time. Most often it is a thermoexpansion valve (TEV) or a low pressure float valve (VPNT). Evaporator As the workpiece evaporates, it absorbs heat and cools the substance and / or space we wish to cool. In the evaporator, the workpiece is housed in tightly arranged tubes to obtain as much surface area as possible for heat exchange. According to the mode of operation, the evaporators are submerged and dry.
The compressor sucks the dry-state steam of state 1 at evaporation pressure (isobar) and isentropically compresses it to state 2. With state 2, the steam enters the condenser in which, by transferring the heat to the cooling tank, it completely condenses to state 4, with which that liquid (Saturated Liquid) enters the Expanzion in which it is extinguished to the point 5 which lies at the evaporation pressure. By bringing heat out of the cooler, the saturated vapor of state 5 in the evaporator at evaporating pressure enters the state of dry saturated vapor 1, thus closing the cycle.
The absorption cooling process differs from the compression process only in that the mechanical compressor is replaced by a thermal compressor (or “heat compressor”). This means that the compensating energy no longer serves as mechanical work (which is brought to the compression system in the form of electricity), but rather the thermal energy brought into the system at a temperature higher than the ambient temperature. The advantage is that the offset energy is usually some cheap waste heat. For a thermal compressor to work, it is necessary for the working substance to be a mixture of two substances. One substance is a refrigerant working substance that condenses in a condenser and evaporates in an evaporator, and the other substance must have the ability to absorb (dissolve) the first substance to circulate as a mixture in a thermocompressor circuit. Most industrial absorption devices and small household appliances work with a mixture of ammonia and water (NH3 / H2O).

1230/5000A working substance circulating inside the device has the function of an energy transporter, taking over the heat energy in one part of the refrigeration unit and transferring it to another part where the heat is transferred to the environment. The properties of the working substances must be such that the heat from the lower to the higher temperature can be transferred under the conditions prevailing within the refrigeration unit. The working substances must meet the specific thermodynamic, safety and physico-chemical requirements. Due to the relatively large range of substances that can be used as working substances in refrigeration systems, universal international labeling has been introduced. For each refrigerant product, the code begins with the capital letter R (refrigerant), followed by two or three digits (eg methane, CH4, labeled R 50). Commonly used household refrigerants, halogenated methane and ethane derivatives, R 11, R 12 and R 22, otherwise remarkably chemically stable, pose a major environmental hazard if the product leaks out of the system. These compounds are known to destroy the ozone layer. The Montreal Protocol prohibits the production of refrigerants with these working substances, and to date the ban should be fully implemented.