In winter (lower ambient temperature), the condensing pressure of the condenser is often low, so that the pressure drop across the expansion valve is reduced, and the refrigerant obtained by the evaporator is too small, resulting in a failure of the refrigeration system.
1. The condensing pressure is too low
In a refrigeration system, if the condenser is installed outdoors, the system's exhaust pressure (condensation pressure) tends to be low in winter (or low temperature), which is often more common in the north, for air conditioning, for This is also the case with other equipment (cold storage, etc.);
If the condensing pressure is too low, the expansion valve will not be able to obtain sufficient pressure drop at both ends, and it is difficult to provide the appropriate refrigerant to the evaporator. On the one hand, the cooling capacity of the system will not meet the requirements, and the system will also cause frequent low-pressure alarms. malfunction;
2. Several methods for increasing condensing pressure at low temperatures
Through the above introduction, we know that in the low temperature environment in winter, the refrigeration system is prone to faults with low condensation pressure. So, is there any way to avoid the condensation pressure in the low temperature environment is too low?
The answer is yes:
1. Use the exhaust pressure controller to control the intermittent operation of the fan;
2. Control the fan speed;
3. Control the air flow by using the damper or the intermittent operation of the fan;
4. Use a condenser overflow device.
3. Method of exhaust pressure controller
The intermittent operation of the fan is simple and easy to use, and the technology is mature. The controller used is a pressure controller, which can control the intermittent start and stop of the fan;
When the pressure is too low, turn off the fan; when the pressure is too high, turn on the fan;
Generally, on a small-capacity unit, two or more fans are used, one of which is normally open, and the other fans are controlled by a pressure controller, and the start or stop of the fan is controlled by the level of the condensing pressure.
4, fan speed control method
The method of fan speed control is also a mature method for many years. The main electrical components used are inverter (three-phase) or governor (single-phase).
The main working principle is to input the inverter (speed governor) through the feedback model of the exhaust pressure (condensing temperature) (1~5V or 4-20ma signal), and the inverter outputs to the fan according to the set output (0~50HZ). Realize the variable speed operation of the fan.
5. Method of air volume control device
The main component is the louvered air volume control unit. The principle is a piston-type damper driven by a high-pressure refrigerant. This control device can operate as a stable exhaust pressure as the fan speed controller; the most important thing is that the inlet pressure of the expansion valve does not cause a larger operation like the intermittent operation of the fan. Fluctuation.
The louver device can be disposed at the air inlet or at the air outlet;
6. Method of condenser overflow device
The condenser overflow device works by using excess refrigerant to increase the condensing pressure of the system.
The condenser overflow device is used for warming or low temperature environment, and the large flow refrigerant is sent from the liquid storage device to the condenser, and the excess refrigerant is used to increase the condensation pressure of the system, thereby avoiding the low condensation pressure at low temperature. malfunction.
advantage:
1. Obtain stable condensing pressure with less fluctuation;
2. The condenser is almost filled with liquid refrigerant, so that the inlet temperature of the expansion valve is lower than the condensation temperature to achieve supercooling, thereby increasing the refrigeration capacity of the refrigeration system.