Experimental Investigation On Characteristics Of Multistage Centrifugal Pump Transporting The Refrigerant

Conventional refrigeration systems use the compressor to provide cycle power, and in the organic rankine cycle, industrial refrigeration, ejector refrigeration cycle and other systems require pump to provide cycle power. As one of the key devices in the ejector refrigeration system, refrigerant pump plays an important role for safe and stable operation of the system. In the experiments of the ejector refrigeration system, domestic and foreign scholars have used centrifugal pumps, magnetic pumps, shielding pumps, gear pumps, sliding vane pumps, diaphragm pumps, oil pumps and others to act as refrigerant pumps, but the very specialized research on the refrigerant pump reports less. Based on the requirements of the operating parameters’ range of the refrigerant pump in the solar ejection refrigeration system, select multistage centrifugal pump as the research object, grasp its basic principles, design and build a test bed, primarily for experimental investigation on characteristics of multistage centrifugal pump transporting R142 b, provide guidance basis for the design optimization of refrigerant pump and system. To sum up, the main research work is as follows:(1) On the basis of the closed loop of the performance test of the conventional rotary power pump, to design and improve the refrigerant pumping. The test system mainly consists of two parts that the refrigerant and the water cycles. 1) The refrigerant cycle is mainly composed of the refrigerant pump, the sleeve tube type heat exchanger, the liquid storage device and the conical cut-off valve. 2) The water cycle is mainly composed of constant temperature water tank, heat exchanger, water pump and ball valve. By debugging and running, the expected test requirements can be achieved.(2) In this paper, by using the test bed to research the inlet pressure(i.e. correspond- ing to the condensing pressure of the ejector refrigeration system), differential pressure, flow rate, speed, efficiency, power consumption and other parameters of the multistage centrifugal pump, and varying operating conditions when the pump efficiency is in the best interval.Experimental results show that: 1) when the pump inlet parameters is corresponding to the condensing parameters, the differential pressure range of the refrigerant pump of the solar ejector refrigeration system with R142 b is 0.725~1.375 MPa. The characteristics of variable-frequency(25/37.5/50Hz) multistage centrifugal pump transporting the refrigerant are studied, When the pump inlet pressure is corresponding to the condensing pressure(pc=0.454 MPa, means the condensation temperature tc=35 corresponding saturation pressure) for test, when the frequency of pump is at ℃25Hz, flow is at the range of 0.1~1.2m3/h, the differential pressure of the pump is among 0.25~0.53 MPa, the total efficiency of the pump is among 4.6%~27.1%, lower than the requirements of the system operating conditions; as the frequency is 37.5Hz, flow is at the range of 0.1~1.6m3/h, the differential pressure of the pump is among 0.76~1.20 MPa, the total efficiency of the pump is among 4.3%~29.7%, can meet the requirements of system operating conditions, and the flow beyonds this flow range is lower than the system requirements; as the frequency is 50 Hz, flow is at the range of 2.14~2.66m3/h, the differential pressure of the pump is among 0.77~1.35 MPa, the total efficiency of the pump is among 22.0%~30.1%, can meet the requirements of the system operating conditions,and below this flow is above the system requirements. Thus, when the frequency of the multistage pump is at 37.5Hz, the flow rate and the differential pressure are provided to meet the operating conditions R142 b system.2) When the inlet pressure is between 0.338~0.523 MPa(condensation temperature tc=25~40 ℃corresponding saturation pressure), the differential pressure of the pump, the overall efficiency, power consumption increases as the inlet pressure increases, and a small change, and relative deviation of each parameter were between-5.4%~6.2%, 2.8%~4.5% and-3.7%~3.0%(compared to the pump inlet pressure is at 0.454MPa).3) When refrigerant pump’s flow rate is at 1m3/h and inlet pressure is corresponding to the condensing pressure(pc=0.454MPa), the outlet pressure, differential pressure and power consumption of the pump increases with the frequency increases; while the total pump efficiency shows a decline after the first rise, the maximum value is about 27.7% between 25~35Hz.4) Pump’s temperature difference between inlet and outlet rapidly decreases at first as flow increases, then decreases gradually, there is a cut-off point during the luffing from steep drop to slow down; and further increases as the frequency increases.