Quasi-secondary compression multi-connected unit heating performance study in cold regions
DATE:2024-03-22
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Since 2017, its market size has reached more than 50% of the total value of centralized air conditioning, and maintains a continuous upward momentum. With the development of low-temperature heating technology, multi-connected units began to develop rapidly in cold regions and gradually expanded to severe cold regions. The end of the multi-connected mostly fan coiler, compared with heating circulating water air - water heat pump, due to the lower compression ratio and exhaust temperature, so it has a better low-temperature performance, but when the outdoor temperature is lowered to -20 ℃ or below, due to the weakening of the heat transfer capacity of the outdoor machine and suction pressure reduction, etc., resulting in multi-connected appear heat production and coefficient of performance (COP) of the rapid attenuation of the rapid rise in exhaust temperature and other issues.
In recent years, with the development of make-up air technology, quasi-secondary compression technology has been widely used in low-temperature air-source heat pumps and has achieved good energy-saving results. In order to improve the low-temperature performance of multi-connected units, quasi-secondary compression technology has gradually begun to be applied to multi-connected units. The quasi-secondary compression multi-connected machine reduces the temperature of the refrigerant by spraying part of the intermediate-pressure refrigerant into the compressor and mixing it with the suction air that has been compressed for a certain period of time to reduce the temperature of the refrigerant, thus reducing the compressor's discharge temperature; at the same time, the compressor's discharge mass flow rate increases due to the replenishment of the intermediate-pressure refrigerant, which leads to the increase in the flow rate of the refrigerant into the indoor unit and the enhancement of the unit's heating capacity; in addition, the replenishment can also Cho et al. measured the performance of a rechargeable multi-connected unit with R410A and R32 at different outdoor temperatures, and the heat capacity of the multi-connected unit was increased by 7.5%~13.3% and 7.8%~13.9%, respectively, while the COP was increased by 2.6%~7.0% and 1.1%~4.7% compared with that of the multi-connected unit without recharge, and the COP was increased by 2.6%~7.0% and 1.1%~4.7%, respectively.Kang et al. measured the performance of the rechargeable multi-connected unit using R410A and R32 at different outdoor temperatures. Kang et al. conducted an experimental study on a multiple unit with a dual make-up air scroll compressor at an outdoor temperature of -20~20 ℃, and compared with a single-stage make-up air unit, the heating capacity and COP of the multiple unit with two-stage make-up air increased by 8.9%~18.9% and 5.8%~9.8%, respectively.Min et al. simulated and investigated the heating performance of a make-up air multiple unit at an outdoor temperature of -17.7~16.7 ℃, and pointed out that due to the increase of exhaust mass flow rate and the increase of evaporator's COP, the heating performance of the make-up air multiple unit is not as good as that of the single-stage make-up air compressor. and heat recovery of the evaporator, the performance of the make-up air multiplexer was effectively improved. In addition to the improvement of heating performance, Liu et al. found through experimental research that the make-up air increased the cooling capacity of the CHP by 10%~15%.
Although scholars have studied the heating performance of the make-up air multi-connected unit, the lowest outdoor temperature in the literature is only -20 ℃, which is far from meeting the heating demand of the cold region; in addition, there are few reports on the application of make-up air multi-connected unit in the cold region. In order to promote the application of the multi-connected unit in severe cold areas, a quasi-secondary compression multi-connected unit experimental bench was constructed in Harbin, and its performance was studied with 91 days of continuous testing.
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In recent years, with the development of make-up air technology, quasi-secondary compression technology has been widely used in low-temperature air-source heat pumps and has achieved good energy-saving results. In order to improve the low-temperature performance of multi-connected units, quasi-secondary compression technology has gradually begun to be applied to multi-connected units. The quasi-secondary compression multi-connected machine reduces the temperature of the refrigerant by spraying part of the intermediate-pressure refrigerant into the compressor and mixing it with the suction air that has been compressed for a certain period of time to reduce the temperature of the refrigerant, thus reducing the compressor's discharge temperature; at the same time, the compressor's discharge mass flow rate increases due to the replenishment of the intermediate-pressure refrigerant, which leads to the increase in the flow rate of the refrigerant into the indoor unit and the enhancement of the unit's heating capacity; in addition, the replenishment can also Cho et al. measured the performance of a rechargeable multi-connected unit with R410A and R32 at different outdoor temperatures, and the heat capacity of the multi-connected unit was increased by 7.5%~13.3% and 7.8%~13.9%, respectively, while the COP was increased by 2.6%~7.0% and 1.1%~4.7% compared with that of the multi-connected unit without recharge, and the COP was increased by 2.6%~7.0% and 1.1%~4.7%, respectively.Kang et al. measured the performance of the rechargeable multi-connected unit using R410A and R32 at different outdoor temperatures. Kang et al. conducted an experimental study on a multiple unit with a dual make-up air scroll compressor at an outdoor temperature of -20~20 ℃, and compared with a single-stage make-up air unit, the heating capacity and COP of the multiple unit with two-stage make-up air increased by 8.9%~18.9% and 5.8%~9.8%, respectively.Min et al. simulated and investigated the heating performance of a make-up air multiple unit at an outdoor temperature of -17.7~16.7 ℃, and pointed out that due to the increase of exhaust mass flow rate and the increase of evaporator's COP, the heating performance of the make-up air multiple unit is not as good as that of the single-stage make-up air compressor. and heat recovery of the evaporator, the performance of the make-up air multiplexer was effectively improved. In addition to the improvement of heating performance, Liu et al. found through experimental research that the make-up air increased the cooling capacity of the CHP by 10%~15%.
Although scholars have studied the heating performance of the make-up air multi-connected unit, the lowest outdoor temperature in the literature is only -20 ℃, which is far from meeting the heating demand of the cold region; in addition, there are few reports on the application of make-up air multi-connected unit in the cold region. In order to promote the application of the multi-connected unit in severe cold areas, a quasi-secondary compression multi-connected unit experimental bench was constructed in Harbin, and its performance was studied with 91 days of continuous testing.