The Influence Of The Temperature Of Condensation On The Performance Of The Compressor
In General, the refrigeration compressor's capacity decreases as the increase of the temperature of condensation. Increase the temperature of condensation reduces the theoretical and actual cooling capacity compressor. Recall that the theoretical compressor has a working volume equal to its working volume and density suction pair does not depend on the temperature of condensation. Therefore, the theoretical mass of the refrigerant displaced by the compressor remains constant at all condensing temperature and theoretical refrigerating capacity is only a function of the cooling effect per unit mass of the refrigerant circulates. Based on these assumptions, the difference in theoretical refrigerating capacity of the compressor on two condensing temperature results from the difference in the refrigerating effect per unit mass.
The decline in the actual cooling capacity can be attributed to reductions in volumetric efficiency and effect of the cooling system. Increase die condensing temperature, while the suction temperature remains constant increases the compression ratio, the reduction of the volumetric efficiency of the compressor.
Therefore, the actual volume of consumption of steam displaced by the compressor is reduced. Therefore, even though the density of the vapor coming from the compressor is the same on all of the condensing temperature, the actual mass flow of refrigerant released compressor decreases as the volumetric efficiency decreases.
High discharge temperatures are undesirable and avoided whenever possible. Higher discharge temperatures increase the temperature of the walls of the cylinder and the suction superheat steam, which have a negative impact on the efficiency of the compressor. High discharge temperatures also increase the speed carbon and acid formation in the system. Increasing the temperature of the condensing also increases the isentropic supply temperature, increasing the amount of work that must be done with the help of the compressor. Consider two systems with the same compressor displacements. One unit operates with a temperature of condensation 100 F (37.8C), and the other works with condensing temperature 120 F (48.9C). Although the piston compressors of the same, increasing the isentropic discharge temperature 1F (0.56C) occurs on the operating system on 120F (48.9C).
Although the piston compressors of the same, increasing the isentropic discharge temperature 1F (0.56C) occurs on the operating system on 120 F (48.9C). The system operates at a discharge temperature 121F (49.4C). The increase is a consequence of the large amount of work is required, the higher the temperature of condensation and the associated increase in the degree of compression. Was condensing temperature increased in such a way that the compression ratio does not change, changing of discharge temperature would be the same as what happens in the temperature of condensation. This answer can be done if the temperature of the suction were proportionally increased from 20F (11.1C) condensing temperature, thereby supporting compression.
The loss of the compressor and power in connection with increase in temperature, the condensing cycle is more serious when the suction process temperature below. Increase condensing temperature from 100 to 120F (37.8 to 48.9C) when the cycle of works on 40F (4.4C) saturation temperature reduces the theoretical compressor capacity by 13% and the actual performance of the compressor by 20%. However, losses in the theoretical capacity of the compressor to 10F cycle is 14%, and losses in productivity of the compressor is 21%. Decrease in volumetric efficiency is responsible for most of the decrease in the actual capacity of the compressor when the higher the temperature of condensation...
|
Industrial