A, the actual volume (referred to as the volume)
In a certain condition, the suction end of the gas delivered to the exhaust end of the gas mass per unit of time is known as the compressor under the work of the compressor quality of the volume of gas delivery, the unit is. If the suction state of the volume calculation, the volume of gas transmission, the unit is. So
(4-1)
Two, volumetric efficiency
Compressor's volumetric efficiency is the actual volume of gas with the theoretical volume of the ratio
(4-2)
It is used to measure the effective use of volumetric compressor cylinder working volume.
Three, refrigeration capacity
Refrigeration compressor is an important part of the refrigeration machine and other parts of the system, such as heat exchangers, throttling devices to work with the effect of refrigeration. Therefore, it is necessary to work with the ability to visualize the unit of time produced by the amount of cold - cooling capacity to express the unit, it is one of the important performance indicators of the refrigeration compressor.
(4-3)
Equation - refrigerant in the given refrigeration working conditions of the unit mass of the refrigerating capacity, the unit is;
-Refrigerant in the given refrigeration working conditions of the refrigerating capacity of the unit volume, the unit is.
In order to facilitate the comparison and selection, it is necessary to provide a unified working condition according to the conditions of its use to indicate the compressor's refrigeration capacity, Table 4-1 lists China's relevant national standards for different forms of single-stage small reciprocating refrigeration compressor nominal working condition and its operating temperature. According to the standard, the heat absorbed by the suction mass superheat should also be included in the compressor's refrigeration capacity.
Four, heat rejection
Heat rejection is the compressor's refrigeration capacity and part of the compressor input power equivalent to the sum of the heat, it is discharged through the condenser in the system. This parameter for the compressor in the heat pump system is a very important performance indicators; in the design of the condenser refrigeration system is also necessary to know.
Figure 4-1 actual refrigeration cycle
From the actual refrigeration cycle shown in Figure 4-1a or heat pump cycle diagram can be seen, the compressor in a certain condition of the heat rejection:
(4-4)
From the compressor in Figure 4-1b of the It is not difficult to find out that
(4-5)
In the above two equations
- specific enthalpy of work at the inlet of the compressor;
- specific enthalpy of work at the outlet of the compressor;
- input power of the compressor;
- specific enthalpy of work at the outlet of the compressor;
- input power of the compressor;
- input power of the compressor to the compressor;
-The heat dissipation of the compressor to the environment.
Table 2-2 lists the nominal operating conditions for compressors used in heat pumps as defined by the American Refrigeration Society's ARI520-85 standard.
V. Indicated Power and Indicated Efficiency
The indicated power consumed by the actual cycle per unit of time is the indicated power of the compressor Pi, in kw, which is equal to
(4-6)
Wi -- the actual cycle of the indicated power of each cylinder or working volume.
The indicated efficiency of refrigeration compressor hi is the ratio of the theoretical isentropic cycle work required to compress 1kg of work mass to the actual cycle indicated work. It is used to evaluate the compressor cylinder or working volume inside the perfect degree of completion of the thermal process.
Six shaft power, shaft efficiency and mechanical efficiency
Transferred by the prime mover to the compressor spindle power known as the shaft power Pe, unit kW, part of it, that is, the power of the indication Pi directly for the completion of the compressor cycle, the other part, that is, the friction power Pm, unit kW, used to overcome the frictional resistance of the moving parts of the compressor and drive the ancillary equipment, such as hydraulic pumps for lubrication, etc.. Such as lubrication with hydraulic pumps.
Seven electric power and electric efficiency
Input motor power is the compressor consumes electric power Pel, unit kW. electric efficiency * isentropic compression of theoretical power and electric power ratio, it is used to assess the use of motor input power of the perfect degree.
Eight coefficient of performance
In order to ultimately measure the power economy of the refrigeration compressor, the use of coefficient of performance COP (Cofficient of performance), which is the refrigeration compressor in a certain condition of refrigeration capacity and the ratio of power consumption.