Double-cold-source air conditioning system with double refrigerating systems

Abstract

The invention discloses a double-cold-source air conditioning system of a double-refrigerating system, which is characterized in that on the premise that the condensing temperature is not changed, a water chilling unit adopts a double-evaporator series connection mode to obtain two different chilled water outlet temperatures, namely a low-temperature cold source and a high-temperature cold source; the two cold sources are connected in series through a chilled water pipeline and bear indoor heat and humidity loads together, so that the comprehensive evaporation temperature of the air conditioning system is increased, and the COP value is increased. Under the condition of the same cooling capacity, the comprehensive evaporation temperature is increased, the operation efficiency of a unit is improved, the energy consumption of a conveying system is reduced, the energy consumption of a host of an air conditioning system is reduced, and the energy consumption of the whole air conditioning system is reduced.

Description

Technical Field

[0001] The present invention relates to air conditioning technology, in particular to a dual-cooling-source air conditioning system with a dual refrigeration system. Background Art

[0002] HVAC energy consumption accounts for a high proportion of building energy consumption, among which the energy consumption and usage cost of chillers (cold source) account for more than half of the entire air-conditioning system. Therefore, improving the energy efficiency of chillers is of great significance to building energy conservation and consumption reduction.

[0003] Currently, the supply and return water temperatures for air conditioning cooling sources are generally 7°C / 12°C, and the temperature difference between the supply and return chilled water is 5°C. The coefficient of performance (COP) of air conditioning cooling sources is generally only 3.8 to 5.6 (Note: The COP of an electric compression chiller is defined as the ratio of the chiller's cooling capacity to its input power; the COP of an absorption chiller is defined as the ratio of the cooling capacity obtained to the heat consumed). Therefore, many studies have sought to improve chiller energy efficiency by utilizing large temperature gradients in chilled water. However, studies of such large temperature gradient chillers have found that using large temperature gradients in chilled water, such as 8°C or 10°C, increases the evaporation temperature. While the condensing temperature remains constant, the unit's COP increases, while the unit's heat exchange area and pump shaft power decrease, resulting in some energy savings. However, the use of a large temperature gradient in chilled water reduces the cooling and dehumidification capacity of the terminal. Furthermore, in actual projects, it is difficult for large temperature gradient systems to achieve the theoretical values. This merely reduces transmission energy consumption through large temperature gradients to improve transmission efficiency, without achieving true energy savings for the main unit.

[0004] Chillers operate according to the reverse Carnot cycle, with their COP being proportional to the evaporation temperature and inversely proportional to the condensing temperature. Generally, a 1°C increase in evaporation temperature increases the COP by approximately 3%, while a 1°C decrease in condensing temperature increases the COP by approximately 3%. However, the condensing pressure of the condenser imposes a low-temperature limit on the condensing temperature. Excessively low condensing temperatures can lead to refrigerant contamination and solution crystallization in lithium bromide absorption chillers, compressor "liquid hammer" in centrifugal chillers, and compressor "oil loss" in screw chillers. Furthermore, lowering the condensing temperature increases the energy consumption of the cooling tower fan and water pump, making the method of lowering the condensing temperature to improve the COP less feasible.

[0005] The sensible heat load of an air conditioning system typically accounts for over 50% of the total load. If only indoor temperature control is employed, high-temperature chilled water at 12-19°C can be used to remove this sensible heat load. However, traditional air conditioning systems generally employ a coupled temperature and humidity control approach. To achieve dehumidification, low-temperature chilled water, typically at 5-7°C, is used, resulting in a waste of energy quality. However, for single-cooling-source systems, increasing the evaporation temperature results in a decrease in the system's dehumidification capacity, making it impossible to meet indoor temperature and humidity control requirements.

[0006] The comparative patent publication number is CN115638485A, an air-conditioning system based on a dual-evaporation temperature absorption chiller. In this solution, the absorption refrigeration cycle module includes a high-pressure generator, a first low-pressure generator, a second low-pressure generator, a high-pressure absorber, a low-pressure absorber, a high-temperature evaporator, a low-temperature evaporator, a condenser, etc., and the preparation of high and low-temperature chilled water is through the refrigerant passing through different throttle valves to form independent high-temperature evaporators and low-temperature evaporators. The refrigerant in this system is connected in parallel after the condenser, while the high and low-temperature chilled water is still independent. A series surface cooler is required at the end to cool the air-conditioning air, thereby completing the operation of the air-conditioning system. Since its refrigerant is no longer connected in series at the end, the high and low-temperature chilled water provided has higher application requirements for the terminal air-conditioning unit, thereby increasing the project cost. Summary of the Invention

[0007] The purpose of the present invention is to resolve the contradiction between increasing the evaporation temperature and controlling the indoor temperature and humidity, as well as the problem of preparing high-temperature chilled water, and to provide a dual-refrigeration system and dual-cold source air-conditioning system. By connecting two evaporators in series and preparing high-temperature chilled water and low-temperature chilled water in series, the comprehensive evaporation temperature of the refrigeration system and the refrigeration performance coefficient COP value of the cold source of the overall air-conditioning system are improved, thereby achieving the purpose of energy saving.

[0008] The above technical problems of the present invention are mainly solved by the following technical solutions: a dual-cold source air-conditioning system with a dual refrigeration system, characterized in that: under the premise that the condensing temperature remains unchanged, the chiller adopts a dual evaporator series connection method to obtain two different chilled water outlet temperatures, namely a low-temperature cold source and a high-temperature cold source; the two cold sources are prepared in series through a chilled water pipeline to jointly bear the indoor heat and humidity load, so as to increase the comprehensive evaporation temperature of the air-conditioning system and increase the refrigeration performance coefficient COP value.

[0009] In the aforementioned dual-cold source air-conditioning system with a dual refrigeration system, preferably, in the air-conditioning system, the cold source refrigerant side is composed of two independent dual refrigeration systems of high temperature and low temperature; wherein the high-temperature refrigeration system is composed of a high-temperature compressor, a high-temperature condenser, a high-temperature throttling device and a high-temperature evaporator to form a circuit; the low-temperature refrigeration system is composed of a low-temperature compressor, a low-temperature condenser, a low-temperature throttling device and a low-temperature evaporator to form a circuit.

[0010] In the aforementioned dual-cooling system with dual cold sources, preferably, the preparation and application process of chilled water is: the high-temperature chilled water in the high-temperature evaporator is directly transported to the low-temperature evaporator for low-temperature heat exchange, and the low-temperature chilled water is supplied to the end.

[0011] In the aforementioned dual-cooling system with dual cooling sources, preferably, the high-temperature chilled water in the high-temperature evaporator can be directly supplied to the terminal through a separate chilled water bypass line via an electric valve.

[0012] In the aforementioned dual-cooling system with dual cold sources, preferably, the high-temperature cold source prepares high-temperature chilled water with a water temperature of 10 to 17°C by a high-temperature evaporator; the low-temperature cold source prepares low-temperature chilled water with a water temperature of 4 to 13°C by a low-temperature evaporator.

[0013] In the aforementioned dual-cooling-source air-conditioning system with a dual refrigeration system, preferably, the refrigeration system where the dual evaporators are located performs heat exchange through a high-temperature condenser and a low-temperature condenser respectively.

[0014] In the aforementioned dual-cooling system with dual cold sources, preferably, according to the change of the terminal load of the system, the pressure difference signal of the pressure sensor between the supply and return pipes is fed back to control the opening of the unit's electric valve, and at the same time, the operating conditions of each unit are optimized according to the inlet water temperature of the main unit and the inlet and outlet water temperature difference. When the terminal load demand is different, the unit operates through the large temperature difference cooling condition and the transition season cooling condition.

[0015] In the aforementioned dual-cooling system and dual-cold source air-conditioning system, as an optimal choice, a large temperature difference cooling condition control strategy is adopted: when the terminal demands low-temperature chilled water, the chilled water return water that has been treated by the terminal load is transported to the high-temperature evaporator through the water collector for heat exchange to obtain high-temperature chilled water. The high-temperature chilled water is directly transported to the low-temperature evaporator for heat exchange again to produce low-temperature chilled water, which is sent to the air-conditioning terminal through the water distributor. The chilled water return water after heat exchange at the air-conditioning terminal enters the water collector to complete the cycle.

[0016] In the aforementioned dual-cooling system and dual-cold source air-conditioning system, as an optimal choice, the transition season cooling condition control strategy is: the air-conditioning cooling load is greatly reduced, and the chilled water return water treated by the terminal load is transported to the high-temperature evaporator through the water collector for heat exchange to form high-temperature chilled water. The high-temperature chilled water is directly transported to the water distributor through the bypass pipe to cool the air-conditioning terminal. The chilled water return water after heat exchange at the air-conditioning terminal enters the water collector to complete the cycle.

[0017] In the aforementioned dual-cold-source air-conditioning system with a dual refrigeration system, preferably, electric valves V1 and V2 are respectively provided at both ends of the low-temperature condenser pipeline in the dual evaporators of the chiller, and an electric valve V3 is provided in the bypass pipeline; an electric valve V4 is provided on the pipeline where the chilled water returns to the low-temperature evaporator; and electric valves V5 and V6 are respectively provided on the cooling water pipeline for heat exchange with the condenser in the dual refrigeration system.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. Under the condition of the same cooling capacity, the chilled water exchanges heat through the high-temperature evaporator and the low-temperature evaporator, which increases the comprehensive evaporation temperature compared with the traditional air-conditioning system, greatly reduces the energy consumption of the entire air-conditioning system, and improves the operating efficiency of the unit.

[0020] 2. Under the condition of the same cooling capacity, the flow rate of the air-conditioning system is reduced due to the increase in the supply and return water temperature difference of the air-conditioning system, thereby reducing the energy consumption of the transportation system.

[0021] 3. In the transition season, when the terminal wet load decreases, the entire air-conditioning system can be completely cooled by the high-temperature evaporator, thereby greatly reducing the energy consumption of the air-conditioning system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a system diagram of the present invention.

[0023] Figure 2 This is a high-temperature refrigeration fault condition operation diagram of the present invention.

[0024] Figure 3 This is a condenser fault condition operation diagram of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention will be further specifically described below through embodiments and in conjunction with the accompanying drawings.

[0026] This embodiment describes a dual-cooling system with dual cooling sources. While maintaining a constant condensing temperature, the chiller utilizes two evaporators in series to achieve two different chilled water outlet temperatures: a low-temperature cooling source and a high-temperature cooling source. These two cooling sources are connected in series through chilled water pipelines, sharing the indoor heat and humidity loads. This increases the overall evaporation temperature of the air conditioning system, significantly improving the system's overall cost-effectiveness ratio (COP).

[0027] The system structure is as follows Figure 1 As shown in the figure (the thin solid line in the figure is the chilled water pipeline, the dotted line is the refrigeration circuit, and the dot-dash line is the cooling water pipeline, the same below), in the air-conditioning system of this embodiment, the cold source refrigerant side is composed of two independent dual refrigeration systems of high temperature and low temperature; the high-temperature refrigeration system is composed of a high-temperature compressor, a high-temperature condenser, a high-temperature throttling device and a high-temperature evaporator to form a circuit; the low-temperature refrigeration system is composed of a low-temperature compressor, a low-temperature condenser, a low-temperature throttling device and a low-temperature evaporator to form a circuit.

[0028] In addition, the high-temperature chilled water in the high-temperature evaporator can be directly supplied to the end through a separate chilled water bypass pipeline via an electric valve.

[0029] Electric valves V1 and V2 are installed at both ends of the low-temperature condenser pipeline in the dual evaporator of the chiller, and electric valve V3 is installed in the bypass pipeline; electric valve V4 is installed on the pipeline from the chilled water return to the low-temperature evaporator, see Figure 3 ; Electric valves V5 and V6 are respectively provided on the cooling water pipes for heat exchange with the condenser in the dual refrigeration system. Figure 3 shown.

[0030] In the two independent refrigeration systems, the high-temperature evaporator produces chilled water at a temperature of 10-17°C for the high-temperature cooling source, while the low-temperature evaporator produces chilled water at a temperature of 4-13°C for the low-temperature cooling source. The chilled water preparation and application process is as follows: the high-temperature chilled water in the high-temperature evaporator is directly transferred to the low-temperature evaporator for low-temperature heat exchange, resulting in low-temperature chilled water that is supplied to the terminal and then delivered to the air conditioner terminal.

[0031] The refrigeration system where the dual evaporator is located performs heat exchange through the high-temperature condenser and the low-temperature condenser respectively.

[0032] This embodiment controls the opening of the unit's electric valve based on the changes in the system's terminal load and the pressure difference signal feedback from the pressure sensor between the supply and return pipes. At the same time, it optimizes the operating conditions of each unit based on the main unit's inlet water temperature and the inlet and outlet water temperature difference. When the terminal load demand is different, the unit operates under large temperature difference cooling conditions and transitional season cooling conditions.

[0033] The refrigerant cycle is as follows: the high-temperature refrigerant at the outlet of the high-temperature evaporator flows into the high-temperature compressor for pressurization and temperature increase. The high-temperature and high-pressure refrigerant passes through the high-temperature condenser, exchanges heat with the cooling water from the cooling tower or other natural cold sources, and is converted into a low-temperature and high-pressure refrigerant. It then passes through the high-temperature throttling device to be converted into a low-pressure refrigerant. Finally, it passes through the high-temperature evaporator to exchange heat with the chilled water, forming a high-temperature refrigeration system refrigerant cycle. Similarly, the high-temperature refrigerant at the outlet of the low-temperature evaporator flows into the low-temperature compressor for pressurization and temperature increase. The high-temperature and high-pressure refrigerant passes through the low-temperature condenser, exchanges heat with the cooling water from the cooling tower or other natural cold sources, and is converted into a low-temperature and high-pressure refrigerant. It then passes through the low-temperature throttling device to be converted into a low-pressure refrigerant. Finally, it passes through the low-temperature evaporator to exchange heat with the chilled water, forming a low-temperature refrigeration system refrigerant cycle.

[0034] Chilled water cycle: The chilled water return water after the end load treatment is sent to the high temperature evaporator through the water collector for heat exchange. The high temperature chilled water return water of 16-23℃ is heat exchanged in the high temperature evaporator to produce high temperature chilled water of 10-17℃, which is directly sent to the low temperature evaporator for heat exchange again. Figure 1 After heat exchange, low-temperature chilled water of 4 to 13°C is generated and sent to the air-conditioning terminal through the water distributor. The chilled water after heat exchange at the air-conditioning terminal returns to the water collector to complete the cycle.

[0035] Cooling water circulation: The 30-40℃ high-temperature cooling water passing through the high-temperature condenser and the low-temperature condenser is transported to the cooling tower or other natural cold sources for cooling to produce 25-35℃ low-temperature cooling water, and then enters the high-temperature condenser or the low-temperature condenser again to complete the cycle.

[0036] Furthermore, according to the control principle of this system, as the terminal load of the water system continuously changes, the pressure differential of the pressure sensor between the supply and return pipes changes. Through the feedback of the pressure differential signal, the opening of the unit's electric valve is controlled. At the same time, the main unit operating conditions are optimized according to the main unit's inlet water temperature and the inlet and outlet water temperature difference, ensuring the main unit's efficient operation. Based on this principle, the air conditioning system of this embodiment can achieve large temperature difference cooling conditions and transitional cooling conditions under different terminal load demands.

[0037] The control strategy for the wide temperature differential cooling condition is as follows: If low-temperature chilled water is required at the terminal, electric two-way valves V1 and V2 are opened, and electric two-way valve V3 is closed, achieving the wide temperature differential cooling condition. The cycle then proceeds as follows: The chilled water return, treated by the terminal load, is transported through the manifold to the high-temperature evaporator for heat exchange. The high-temperature evaporator heats up the 16-23°C high-temperature chilled water, producing high-temperature chilled water at 10-17°C. This water is then directly transported to the low-temperature evaporator for further heat exchange, generating low-temperature chilled water at 4-13°C. This water is then transported to the air conditioner terminal through the manifold. After heat exchange at the air conditioner terminal, the return chilled water enters the manifold, completing the cycle.

[0038] Control Strategy for Transitional Seasonal Cooling Conditions: During the transitional season, the cooling load on the air conditioner is significantly reduced. Therefore, only the electric two-way valve V3 can be opened, while the electric two-way valves V1 and V2 can be closed, achieving "transitional season cooling conditions." The circulation process is as follows: The chilled water return, which has been treated by the terminal load, is transported through the manifold to the high-temperature evaporator for heat exchange. The high-temperature chilled water, at a temperature of 16-23°C, undergoes heat exchange in the high-temperature evaporator, producing high-temperature chilled water at a temperature of 10-17°C. This is then directly transported through a bypass line to the manifold, and then to the air conditioner terminal for cooling. The chilled water return, after heat exchange at the air conditioner terminal, enters the manifold, completing the cycle.

[0039] In addition, the control strategy for the transition season refrigeration condition is also applicable to the operation control when the low temperature evaporator or low temperature refrigeration system fails. Figure 2 、 Figure 3 Accordingly, if the high-temperature evaporator or high-temperature refrigeration system fails, a bypass line and electric two-way valve V4 can be installed between the low-temperature evaporator's chilled water return inlet and the low-temperature evaporator. Opening electric two-way valves V4, V1, and V2, and closing V3 allows the air conditioning system to complete low-temperature cooling. Accordingly, electric connecting valves V5 and V6 are installed on the condenser water inlet pipe to control the cooling water flow of the condenser and shut down the condenser in the event of a fault.

[0040] The above embodiments are intended to illustrate the present invention, not to limit it. The embodiments described are only a portion of the present invention, not all of the embodiments. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

Claims

1. A dual-cooling system with dual cold sources, characterized in that: Under the premise of unchanged condensing temperature, the chiller adopts dual evaporators in series to obtain two different chilled water outlet temperatures, namely low-temperature cold source and high-temperature cold source; the two cold sources are prepared in series through the chilled water pipeline to jointly bear the indoor heat and humidity load to increase the comprehensive evaporation temperature of the air-conditioning system and increase the refrigeration performance coefficient COP value.

2. The dual-cold-source air-conditioning system of the dual-refrigeration system according to claim 1, characterized in that In the air-conditioning system, the cold source refrigerant side is composed of two independent dual refrigeration systems of high temperature and low temperature; the high temperature refrigeration system is composed of a high temperature compressor, a high temperature condenser, a high temperature throttling device and a high temperature evaporator to form a circuit; the low temperature refrigeration system is composed of a low temperature compressor, a low temperature condenser, a low temperature throttling device and a low temperature evaporator to form a circuit.

3. The dual-cold-source air-conditioning system of the dual-refrigeration system according to claim 1, characterized in that: The preparation and application process of chilled water is as follows: the high-temperature chilled water in the high-temperature evaporator is directly transported to the low-temperature evaporator for low-temperature heat exchange, and the low-temperature chilled water is generated and supplied to the end.

4. The dual-cold-source air-conditioning system of the dual-refrigeration system according to claim 3 is characterized in that: The high-temperature chilled water in the high-temperature evaporator can be directly supplied to the end through a separate chilled water bypass pipeline via an electric valve.

5. A dual cold source air conditioning system with a dual refrigeration system according to claim 1, 2 or 3, characterized in that: The high-temperature cold source prepares high-temperature chilled water with a water temperature of 10 to 17°C by a high-temperature evaporator; the low-temperature cold source prepares low-temperature chilled water with a water temperature of 4 to 13°C by a low-temperature evaporator.

6. The dual-cold-source air-conditioning system of the dual-refrigeration system according to claim 2, characterized in that: The refrigeration system where the dual evaporator is located performs heat exchange through a high-temperature condenser and a low-temperature condenser respectively.

7. A dual cold source air conditioning system with a dual refrigeration system according to claim 1 or 2 or 3 or 4 or 6, characterized in that: According to the changes in the system's terminal load, the pressure difference signal feedback from the pressure sensor between the supply and return pipes is used to control the opening of the unit's electric valve. At the same time, the operating conditions of each unit are optimized according to the main unit's inlet water temperature and the inlet and outlet water temperature difference. When the terminal load demand is different, the unit operates through large temperature difference cooling conditions and transitional season cooling conditions.

8. The dual-cold-source air-conditioning system of the dual-refrigeration system according to claim 7, characterized in that: Control strategy for large temperature difference cooling conditions: When the terminal demands low-temperature chilled water, the chilled water return water that has been treated by the terminal load is transported to the high-temperature evaporator through the water collector for heat exchange to obtain high-temperature chilled water. The high-temperature chilled water is directly transported to the low-temperature evaporator for heat exchange again to produce low-temperature chilled water, which is then sent to the air-conditioning terminal through the water distributor. The chilled water return water after heat exchange at the air-conditioning terminal enters the water collector to complete the cycle.

9. The dual-cold-source air-conditioning system of the dual-refrigeration system according to claim 7, characterized in that: Control strategy for cooling conditions in transitional seasons: The cooling load of the air conditioner is greatly reduced. The chilled water return water that has been treated by the terminal load is transported to the high-temperature evaporator through the water collector for heat exchange to form high-temperature chilled water. The high-temperature chilled water is directly transported to the water distributor through the bypass pipeline to cool the air conditioner terminal. The chilled water return water after heat exchange at the air conditioner terminal enters the water collector to complete the cycle.

10. The dual-cold-source air-conditioning system of the dual-refrigeration system according to claim 7, characterized in that: Electric valves V1 and V2 are respectively arranged at both ends of the low-temperature condenser pipeline in the dual evaporator of the chiller, and an electric valve V3 is arranged in the bypass pipeline; an electric valve V4 is arranged on the pipeline from the chilled water return to the low-temperature evaporator; and electric valves V5 and V6 are respectively arranged on the cooling water pipeline for heat exchange with the condenser in the dual refrigeration system.

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