The corresponding Changes to the saturation Temperature
The first column in table sizes are listed pipe size (OD)which will be acceptable pressure drop in cooling capacity on the list. Differential pressure regularly latedby choice of pipes of the big diameter. As tlie spacer tube diameter increases the speed die refrigerant flow decreases, reducing the die differential pressure that forms through the pipe. Pressure drop in cooling sizes of tables listed in units of temperature, not units of pressure. They are designed so that " diat", the diameter of the pipe does not create a differential pressure, which leads to a reduction of more than 1 or 2F (0.55 1.1C) in the saturated suction temperature of the refrigerant.
In other words, in determining the suction line pressure drop should not make more than 2F (1.1C) change to die saturated refrigerant temperature. Similarly, in determining the discharge or liquid line, pressure drop must not make more than 1F (0.55C) change the saturation temperature of the refrigerant. Linking diese change the saturation temperature, with the subsequent changes of pressure shows diat 2F (1.1C) changes in the saturated suction temperature, R-22 operating system 40 F (4.4C) corresponds to the pressure drop in 2.91 psi (20 kPa).
Similarly, tlie spacer suction line in R-134a operating system with the saturated suction temperature 40 F (4.4C) is designed so that the full-load pressure difference between the outlet and inlet of the compressor is not more than 1.93 psi (13 kPa). R-502 system is designed in such a way that the suction line pressure drop is less than 3.2 psi (22 kPa) at full load. When the refrigeration piping pressure drop exceeds these design standards, system performance and efficiency, reduced below a sustainable level.
Differential pressure listed in units of temperature, to simplify the development and use of calibration tables. The maximum recommended pressure difference refrigeration piping decreases as the saturation temperature decreases. This is because the die density or refrigerant vapor decreases as its saturation temperature decreases. Therefore, at lower temperatures, saturation, it takes less than a change in pressure to produce a unit change in temperature of saturation. Therefore, instead of trying to list all die allowable pressure falls, corresponding to the different refrigerant types at different temperatures saturation corresponding temperature change is used as a basis for determining the size of refrigeration piping.
In the following five columns diameter pipes correspond to different suction line temperature of saturation. The temperature in the list at the top of each column vary between different refrigerant tables in order to correlate with a typical application temperatures. Note that the capacity of the channel increases as the saturated suction temperature rises. This is because the specific volume of the refrigerant decreases as the temperature increases, thereby increasing the mass flow rate of refrigerant compressor. The following two columns suction line sizes of the columns correspond to tlie spacer discharge line size. Note that the pressure throughout the discharge line is limited to the equivalent of 1F (0.55C) temperature change.
The remaining columns in the table are used to determine the size of the liquid line between the condenser and receiver and liquid line between the receiver outlet and the metering device. These columns are based on the maximum velocity of the fluid 100 m/min for liquid line between the condenser and receiver or 1F (0.55C) change the saturation temperature refrigerant fluid flowing lines in systems that do not use the receiver...
|
Industrial