Refrigerant pump liquid pipe boosting system

This technical method uses a small liquid pump to pressurize the liquid refrigerant entering the liquid pipe, as shown in Figure 26.26 (B). For ease of comparison, the system diagram of the conventional system is also listed in Figure 26.26 (A). For systems without liquid storage, the increased pressure value is equal to the pressure loss between the condenser outlet and the inlet of the thermal expansion valve; For thermal expansion valves and systems with a reservoir, it is equal to the pressure loss between the reservoir and the inlet of the thermal expansion valve. Boosting the pressure of liquid refrigerant can increase the saturation temperature when it is inconvenient to maintain the actual temperature of the liquid refrigerant. In this way, even if the liquid refrigerant is in the liquid pipe and there is a pressure drop during the flow into the metering device, it can only gradually become undercooled and cannot flash. The specifications of the refrigerant pump can be determined based on the relevant parameters of the system.

By using this method of supercooling, the liquid refrigerant in the condenser can have more internal volume to condense the refrigerant, as the condenser in this system no longer needs to use its bottom channel as the subcooling loop, thus achieving such results. It can reduce the temperature and pressure of condensation, thereby reducing the compression ratio and improving the boosting efficiency of the compressor. In fact, due to the action of the centrifugal pump, the liquid refrigerant is supercooled, so the exhaust pressure should be allowed to fluctuate with changes in outdoor ambient temperature. The fluctuation of exhaust pressure is a specialized term that refers to the use of lower ambient temperatures as a condensing medium to achieve the lowest possible exhaust pressure. This system can achieve very low condensation pressure, so the manufacturer of the thermal expansion valve has launched a thermal expansion valve on the market that can control the pressure at both ends within 30 psi. Moreover, if it can provide 100% liquid refrigerant, it can still be ideal for the evaporator to provide the required refrigerant. The four advantages of a liquid pipe turbocharging system are:

1. By pressurizing the liquid pipe to compensate for the pressure loss in the pipeline, the flashing phenomenon of the liquid pipe is eliminated.
2. Due to the efficiency of using a refrigerant pump to pump liquid refrigerant being 40 times higher than using the exhaust pressure from the compressor to pump liquid refrigerant, energy costs can be saved.
3. It can increase the evaporator capacity and cooling capacity.
4. Reduce the compression ratio and various stresses acting on the compressor.

The method of injecting liquid refrigerant into the exhaust pipe or condenser inlet of the compressor can also be used for liquid pipe pressurization systems. When this liquid refrigerant flashes into vapor, it can cool the discharged hot vapor close to its condensation temperature. This reduces the surface area required to eliminate overheating, thereby increasing the efficiency of the condenser and improving the overall performance of the system. The liquid refrigerant injected into the exhaust pipe comes from the same refrigerant pump, which simultaneously sends the pressurized liquid refrigerant to the metering device, as shown in Figure 26.26 (C). Although this system can improve efficiency even in low ambient temperatures, it can achieve maximum efficiency in high ambient temperatures.

——Refrigeration and Air Conditioning Technology "(Fifth Edition) by William C. Whitman, translated by Shou Mingdao (P461-462)