The regenerator plays an important role in the refrigeration cycle: 1 further reducing the temperature of the gas cooler outlet working, so that more heat can be obtained; 2 reducing the throttling loss to a greater extent, while obtaining more cooling capacity; The machine absorbs the dryness of the working fluid to avoid liquid accidents. 4 regenerators can also reduce compressor power consumption, which in turn improves system performance. In the CO 2 transcritical cycle, the throttling loss is relatively large, and the equivalent condensing temperature is high, so that a regenerator is provided in the cycle, which can meet the performance requirements and achieve high efficiency, which is in the CO 2 air source heat pump system. Particularly important. Based on the above analysis, the author conducted theoretical analysis and experimental performance tests on the CO 2 transcritical single-stage cycle with regenerator and without regenerator, providing research data for further optimization of single-stage cycle performance and promotion of CO 2 air-conditioning products. . 1 CO 2 transcritical single-stage circulation system with regenerator and without regenerator 1.1 CO 2 transcritical single-stage circulation without regenerator Typical CO 2 transcritical single-stage circulation mainly consists of compressor and gas It consists of a cooler, a throttle valve and an evaporator. The principle of CO 2 transcritical single-stage circulation is given respectively. The low-pressure gaseous refrigerant is compressed into a high-pressure gas refrigerant through a compressor (process 1D2), subjected to a constant pressure and heat release through a gas cooler (process 2D 3), and then throttle-depressurized through a throttle valve (process 3D4), low pressure The liquid refrigerant is subjected to constant pressure absorption in the evaporator (process 4D1) and finally returned to the compressor to complete a cycle. 1.2 Adding a regenerator in the CO 2 transcritical single-stage circulating refrigeration cycle with regenerator can reduce the throttling loss and increase the cooling capacity, thus improving the system performance. The theoretical analysis of CO 2 transcritical single-stage cycle with 2-band regenerator and without regenerator is given 2.1 The COP calculation of CO 2 transcritical single-stage cycle COP is as follows. (2)2.2 Two cycle performance comparison analysis gives the change of two cyclic COPs with evaporation temperature. With the increase of evaporation temperature, the COP of both cycles increased. The higher the evaporation temperature, the better the system performance. The average performance of the regenerator cycle was higher than that without the regenerator cycle. About 4.55%; for an ideal compressor cycle, the system performance is higher than the actual cycle performance by more than 33.3%, but this ideal cycle does not exist. The variation of the two cycle COPs with the gas cooler outlet temperature is given. As the outlet temperature of the gas cooler increases, the COP of both cycles decreases. The higher the temperature, the worse the system performance. The average performance of the regenerator cycle is lower than that of the gas cooler. The heat cycle is increased by about 5.23%. The two cycle COPs vary with the compressor discharge temperature. See Figure 7. In the range of exhaust gas temperature changes, the COP with regenerator CO 2 transcritical single-stage circulation system is higher than without regenerative heat under the same contrast conditions. The cycle is reversed and the temperature of the single-stage cycle with the regenerator is slightly higher. Regardless of whether there is a regenerator or a regenerator cycle, as the efficiency of the compressor increases, the COP of the system becomes larger, and the exhaust temperature of the compressor is reduced, and the cycle without the regenerator is greatly reduced. It can also be seen that there is an optimal exhaust gas temperature in both single-stage cycles, so that the system COP is maximum at this temperature, and the optimal exhaust gas temperature corresponding to the regenerator cycle is higher than that without the regenerator cycle. Exhaust gas temperature. 3 CO 2 transcritical single-stage cycle experiment with or without regenerator 3.1 Experimental table consisting of two CO 2 transcritical single-stage cycles using a single-stage two-cylinder piston compressor produced by Italian company Dorin, theoretical volume The emission is 3.5, m 3 /h, the rated input power is 4.0, kW; the gas cooler is a newly designed casing structure, and the three intertwined copper tubes form the inner tube of the heat exchanger, and the internal pipe pressure is the highest. Up to 12, MPa, the outer tube is water channel; the evaporator is stainless steel shell tube type, its design, manufacture and acceptance are in accordance with GB151D89 "steel shell and tube heat exchanger" and GB150D89 "steel pressure vessel" The pressure vessel is carried out. The evaporator is a double-tube single-shell process, the refrigerant flows in the tube, the inlet and outlet are in different sides, and the chilled water flows on the shell side. 3.2 Experimental results Analysis The parameters in the experiment are: cooling water inlet temperature (20.5 ± 0.5) ° C, cooling water flow rate (1.25 ± 0.01) m 3 / h, chilled water inlet temperature (10.5 ± 0.5) ° C, chilled water flow ( 1.55±0.01) m 3 /h, system high pressure (7.8±0.05), MPa. Variable parameters in the experiment: cooling water inlet temperature 15 ~ 25, ° C, cooling water flow 0.6 ~ 1.6, m 3 / h, chilled water inlet temperature 7 ~ 17, ° C, chilled water flow 0.4 ~ 1.6, m 3 / h , system high pressure 6 ~ 9.5 MPa. 3.2.1 The CO 2 transcritical single-stage cycle without regenerator gives the effect of compressor high pressure on system cooling capacity Q c and heating capacity Q h . It can be seen that as the high pressure of the system increases, both the cooling capacity and the heating capacity increase. At a certain pressure, the cooling capacity and the heating capacity are extremely extreme. After that, as the pressure increases, the cooling capacity and the heating capacity gradually decrease. The influence of compressor high pressure on refrigeration COP c and heating COP h is given. The overall trend of COP c and COP h is that it rises with increasing pressure, reaches a maximum at a certain pressure, and then decreases with increasing pressure. The change of cooling COP c and heating COP h with chilled water inlet temperature is given. As can be seen from the figure, as the chilled water inlet temperature increases, both COP c and COP h increase. It can be seen that as the chilled water inlet temperature increases, the evaporator outlet water temperature and the refrigerant temperature increase, so that the cooling capacity and the heating capacity increase accordingly, and COP c and COP h also increase. The effect of chilled water flow on system cooling capacity Q c and heating heat Q h 3. With the increase of chilled water flow, both cooling capacity Q c and heating heat Q h showed a slight upward trend. It can be seen from 4 that as the flow rate of chilled water increases, both the refrigeration COP c and the heating COP h increase slightly. The analysis shows that with the increase of chilled water flow, the water side disturbance of the heat exchanger is strengthened and the turbulence is intensified, which makes the heat exchange inside the heat exchanger more sufficient. The cooling capacity Q c and the cooling COP c, the heating amount Q h and the heating COP h increases. The influence of the cooling water inlet temperature on the cooling capacity Q c and the heating capacity Q h is given. As the inlet temperature of the cooling water increases, both the cooling capacity Q c and the heating capacity Q h decrease. The higher the cooling water inlet temperature, the smaller the cooling capacity Q c and the heating amount Q h , which is mainly due to the cooling water inlet temperature. The increase leads to an increase in the temperature of the CO 2 refrigerant at the gas cooler outlet, which reduces the system cooling capacity and heating capacity. It can be seen that as the temperature of the cooling water inlet increases, both the cooling COP c and the heating COP h decrease. The higher the cooling water inlet temperature, the smaller the cooling COP c and the heating COP h. The effect of cooling water flow on the cooling capacity Q c and the heating capacity Q h . As the cooling water flow increases, both the cooling capacity Q c and the heating capacity Q h increase, and the larger the flow rate, the larger the cooling capacity Q c and the heating amount Q h . The effect of cooling water flow on refrigeration COP c and heating COP h is given. The overall trend of COP c and COP h is increasing with the increase of cooling water flow. The smaller the flow rate, the smaller the cooling COP c and the heating COP h. The flow rate of cooling water increases, the water side disturbance of the heat exchanger is strengthened, the turbulence is intensified, and the heat exchange effect is strengthened, which plays a positive role in further reducing the outlet temperature of the gas cooler. As the CO 2 temperature at the gas cooler outlet decreases, the cooling capacity Q c and the cooling COP c , the heating amount Q h , and the heating COP h increase. 3.2.2 CO 2 transcritical single-stage circulation with regenerator The effects of compressor discharge pressure on cooling capacity Q c and heating heat Q h , cooling COP c and heating COP h are given respectively. As the exhaust pressure increases, both the cooling capacity Q c and the heating capacity Q h increase. At a certain high pressure, the cooling capacity Q c and the heating amount Q h appear to be extreme, and then, as the high pressure increases, the two gradually decline. The trend of cooling COP c and heating COP h is basically the same as that without regenerator cycle. The cooling capacity Q c , the heating capacity Q h , and the change of the cooling COP c and the heating COP h with the chilled water inlet temperature 1 and 2. As can be seen from the figure, as the chilled water inlet temperature increases, the evaporator outlet water temperature and the refrigerant temperature are both Increase, so that the cooling capacity and heating capacity will increase accordingly, and COP c and COP h will also increase. It can be seen that as the flow rate of chilled water increases, the water side disturbance in the heat exchanger is strengthened and the turbulence is intensified, so that the heat exchange inside the heat exchanger is more sufficient, the cooling capacity Q c and the cooling COP c, the heating amount Q h and the heating COP h Both increase. The effects of cooling water inlet temperature on cooling capacity Q c and heating heat Q h , cooling COP c and heating COP h are given respectively. The same as the trend of the regenerator cycle, the cooling water inlet temperature increases, the cooling capacity Q c and the heating capacity Q h as well as the cooling COP c and the heating COP h decrease, and the cooling water inlet temperature is higher, 4 The smaller the performance parameters. This is mainly due to the increase of the temperature of the cooling water inlet, which causes the temperature of the CO 2 refrigerant at the outlet of the gas cooler to rise, so the cooling capacity and heating capacity of the system are reduced. Correspondingly, the cooling COP c and the heating COP h are also Reduce the trend. The effect of cooling water flow on the cooling capacity Q c and heating capacity Q h is shown in Figure 27. The cooling water flow increases, the cooling capacity Q c and the heating capacity Q h both increase, the larger the flow rate, the cooling capacity Q c and the heating capacity Q The bigger h is. The trend of cooling COP c and heating COP h is the same. The CO 2 transcritical cycle test data with and without regenerators were compared and analyzed. The results show that the regenerator circulation system has higher performance under the same test conditions. Among them, the heating capacity Q h and the cooling capacity Q c are about 3.33% and 5.35% higher than the single-stage circulation without regenerator, respectively, and the heating COP h and the cooling COP c are increased by about 11.36% and 14.29%, respectively. The increase will vary depending on the selected calculation conditions and experimental parameters, but the regenerator is undoubtedly improving the performance of the refrigeration cycle system. 4 Conclusions (1) Within the range of evaporating temperature variation, the average performance of the regenerator cycle is about 4.55% higher than that without the regenerator cycle; in the range of gas cooler outlet temperature variation, the average performance of the regenerator cycle is Compared with no regenerator cycle, the increase is about 5.23%; under the same contrast conditions, the COP of the CO 2 transcritical single-stage circulation system with regenerator is higher than that without the regenerator cycle, and the single-stage circulation with regenerator is optimal. The exhaust temperature is slightly higher. (2) The heating capacity Q h, the cooling capacity Q c , the heating COP h and the cooling COP c of the two single-stage cycles all have extreme values ​​with increasing compressor discharge pressure; with cooling water flow, chilled water flow and chilled water The inlet temperature increases and increases, and decreases as the cooling water inlet temperature increases. (3) With the same test conditions, the regenerator circulation system has higher performance. Among them, the heating heat Q h and the cooling capacity Q c are respectively higher than the single-stage circulation without regenerator by about 3.33,% and 5.35,%, the heating COP h and the cooling COP c are increased by about 11.36,% and 14.29, respectively. %. Colored Tape Hot Printer,Hot Print,Hot Press Printing,Hot Transfer Printing WENZHOU BROTHER MACHINERY CO., LTD. , https://www.chinabrother.net
Exploration and experiment of compression and heat recovery device