Авіаційно-космічна техніка та технологія (Dec 2018)
APPROACH TO ANALYZING THE EFFICIENCY OF COOLING CAPACITY CONTROL OF AMBIENT AIR CONDITIONING SYSTEMS
Abstract
It is determined that the operation of ambient air conditioning systems (AACS) has significant fluctuations in the heat load in accordance with current climatic conditions. This makes very problematic the application of refrigeration compressors with frequency converters, which are very effective for controlling the refrigeration capacity in closed air conditioning systems, in which the temperature control range and, accordingly, fluctuations in thermal load are insignificant in comparison with the ambient air cooling. For the purpose of analyzing the efficiency of controlling the refrigeration capacity of the AACS by changing the electric motor speed of the piston compressor in current climatic conditions, the entire range of changing current thermal loads is divided into two parts according to controlling the refrigeration capacity by appling a frequency converter: the part of effective cooling capacity adjustment without energy losses (without reducing the coefficient of performance) from nominal to its threshold value and the part of reduced refrigeration capacity without its controlling by a frequency converter. It is revealed that for the warmest summer month, the proportion of refrigeration capacity spent for cooling ambient air to the temperature of 10 °C with 50 % frequency controlling the refrigeration capacity is about 10 % of the total amount of that could be produced at nominal refrigeration capacity. At higher temperatures of cooled air is even less. This shows the low efficiency of controlling the refrigeration capacity of the AACS by changing the speed of rotation of the piston compressor electric motor and the need to use other methods of controlling the refrigeration capacity. The proposed approach to analyzing the efficiency of controlling the refrigeration capacity of AACS in current climatic conditions allows not only to estimate the efficiency of refrigeration capacity controlling method but also to reveal the reserves for increasing the efficiency of applying the available refrigeration capacity
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