Double-evaporator and double-compressor type double-cold-source air conditioning system

Abstract

The utility model discloses a double-evaporator and double-compressor type double-cold-source air conditioning system which is characterized by comprising two cold source refrigerant side loops, and a high-temperature refrigerating system is a circulation loop composed of a high-temperature compressor, a condenser, a high-temperature throttling device and a high-temperature evaporator. The low-temperature refrigerating system forms a circulation loop by a low-temperature compressor, a condenser, a low-temperature throttling device and a low-temperature evaporator, and the two refrigerating systems share the condenser; the preparation and application process of the chilled water comprises the steps that the high-temperature chilled water in the high-temperature evaporator is directly conveyed to the low-temperature evaporator for low-temperature heat exchange, and the generated low-temperature chilled water is supplied to the tail end; and the condenser exchanges heat with cooling water from a cooling tower or other natural cold sources. The comprehensive evaporation temperature is increased, the energy consumption of the whole air-conditioning system is greatly reduced, the operation efficiency of a unit is improved, and the energy consumption of a conveying system and the energy consumption of a host of the air-conditioning system are reduced.

Description

Technical Field

[0001] This utility model relates to air conditioning technology, and in particular to a dual-evaporator, dual-compressor dual-cooling-source air conditioning system. Background Technology

[0002] Heating, ventilation, and air conditioning (HVAC) accounts for a large proportion of building energy consumption. Among them, the energy consumption and operating 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 for building energy conservation and consumption reduction.

[0003] Commonly used methods to improve the energy efficiency of chiller units include: (1) improving compressor compression efficiency; (2) improving heat exchanger heat exchange performance; (3) finding new refrigerants; and (4) large temperature difference technology for chilled water. Among these, the first three methods are difficult to break through due to limitations in mechanical and material technologies, while the fourth technology is currently more widely used. Currently, the supply and return water temperatures of air conditioning chilled water sources are generally 7℃ / 12℃, and the temperature difference between the supply and return water of chilled water is 5℃. The coefficient of performance (COP) of air conditioning chilled water sources is generally only 3.8 to 5.6. Public information shows that studies have been conducted on large temperature difference chiller units. Selecting chilled water with large temperature differences such as 8℃ and 10℃ will lead to an increase in evaporation temperature. When the condensation temperature remains unchanged, the unit's COP increases. At the same time, the unit's heat exchange area decreases and the water pump shaft power decreases, which has a certain energy-saving effect. However, after adopting a large temperature difference in chilled water, the cooling and dehumidification capacity of the terminal decreases. In actual engineering, it is difficult to achieve the effect of a large temperature difference system during operation. It merely reduces the energy consumption of transmission to improve transmission efficiency by using a large temperature difference, without achieving the true energy-saving effect of the main unit.

[0004] Chiller units operate according to the reverse Carnot cycle, with their Coefficient of Performance (COP) directly proportional to the evaporation temperature and inversely proportional to the condensation temperature. Typically, a 1°C increase in evaporation temperature raises the COP by approximately 3%, while a 1°C decrease in condensation temperature raises it by approximately 3%. However, the condensing pressure of the condenser limits the condensation temperature. Excessively low condensation temperatures can lead to refrigerant contamination and solution crystallization in lithium bromide absorption chillers, liquid slugging in centrifugal chillers, and oil loss in screw chillers. Furthermore, lowering the condensation temperature increases the energy consumption of cooling tower fans and pumps, making the method of lowering the condensation temperature to increase COP impractical.

[0005] Sensible heat load typically accounts for more than 50% of the total load in an air conditioning system. If only indoor temperature is controlled, high-temperature chilled water at 12–19°C can be used to remove the sensible heat load. However, traditional air conditioning systems generally use a temperature and humidity coupled control method. To achieve dehumidification, low-temperature chilled water at 5–7°C is usually used, resulting in energy waste. Furthermore, for single-source cooling systems, increasing the evaporation temperature leads to an increase in COP, but this is accompanied by a decrease in the system's dehumidification capacity, making it unable to meet indoor temperature and humidity control requirements. Summary of the Invention

[0006] The purpose of this invention is to solve the contradiction between increasing evaporation temperature and controlling indoor temperature and humidity, as well as the problem of preparing high-temperature chilled water, by providing a dual-evaporator, dual-compressor dual-cold-source air conditioning system. This system has the characteristics of increasing the overall evaporation temperature of the air conditioning system and increasing the overall cooling performance coefficient (COP) value of the system.

[0007] The above-mentioned technical problems of this utility model are mainly solved by the following technical solution: a dual-evaporator, dual-compressor dual-cold-source air conditioning system, characterized in that it includes two cold-source refrigerant side loops, wherein the high-temperature refrigeration system consists of a high-temperature compressor, a condenser, a high-temperature throttling device, and a high-temperature evaporator forming a circulation loop, and the low-temperature refrigeration system consists of a low-temperature compressor, a condenser, a low-temperature throttling device, and a low-temperature evaporator forming a circulation loop, and the two refrigeration systems share a condenser; and 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 low-temperature chilled water is generated and supplied to the terminal; the condenser exchanges heat with cooling water from a cooling tower or other natural cold source.

[0008] In the aforementioned dual-evaporator, dual-compressor dual-cold-source air conditioning system, preferably, the high-temperature evaporator produces high-temperature chilled water with an outlet temperature of 10–17°C, and the low-temperature evaporator produces low-temperature chilled water with an outlet temperature of 4–13°C.

[0009] In the aforementioned dual-evaporator, dual-compressor dual-cold-source air conditioning system, preferably, in the chilled water preparation process, the high-temperature chilled water in the high-temperature evaporator can be directly supplied to the terminal via a separate chilled water bypass pipeline through an electric valve V3.

[0010] In the aforementioned dual-evaporator, dual-compressor, dual-cold-source air conditioning system, preferably, the refrigerant circulation is as follows: High-temperature refrigerant from the high-temperature evaporator outlet flows into the high-temperature compressor for pressurization and heating. The high-temperature, high-pressure refrigerant passes through the condenser, exchanges heat with cooling water, and transforms into low-temperature, high-pressure refrigerant. It then passes through a high-temperature throttling device to become low-pressure refrigerant, and finally returns to the high-temperature compressor through heat exchange with chilled water in the high-temperature evaporator, forming a cycle. Similarly, high-temperature refrigerant from the low-temperature evaporator outlet flows into the low-temperature compressor for pressurization and heating. The high-temperature, high-pressure refrigerant passes through the condenser, exchanges heat with cooling water, and transforms into low-temperature, high-pressure refrigerant. It then passes through a low-temperature throttling device to become low-pressure refrigerant, and finally returns to the low-temperature compressor through heat exchange with chilled water in the low-temperature evaporator, forming a cycle.

[0011] In the aforementioned dual-evaporator, dual-compressor dual-cold-source air conditioning system, as a preferred embodiment, the chilled water circulation is as follows: the chilled water return water, after being treated by the terminal load, is sent to the high-temperature evaporator for heat exchange via a water collector.

[0012] In the aforementioned dual-evaporator, dual-compressor dual-cold-source air conditioning system, preferably, the high-temperature chilled water return water after passing through the water collector exchanges heat through the high-temperature evaporator to produce high-temperature chilled water of 10-17°C, which is directly transported to the low-temperature evaporator for further heat exchange, producing low-temperature chilled water of 4-13°C, 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 circulation.

[0013] In the aforementioned dual-evaporator, dual-compressor, dual-cooling-source air conditioning system, as a preferred embodiment, the pressure difference signal feedback is obtained by the pressure sensor between the supply and return water pipes to control the opening of the unit's electric valve. At the same time, based on the main unit's inlet water temperature and the inlet and outlet water temperature difference, the system can complete the operation of cooling under large temperature difference conditions and cooling under transitional season conditions.

[0014] In the aforementioned dual-evaporator, dual-compressor dual-cold-source air conditioning system, preferably, a bypass pipe and a two-way electric valve V4 are provided between the chilled water return inlet of the low-temperature evaporator and the low-temperature evaporator.

[0015] This technical solution addresses the contradiction between increasing evaporation temperature and controlling indoor temperature and humidity, as well as the problem of preparing high-temperature chilled water. Based on a dual-evaporator, dual-compressor dual-cold-source system, the chiller unit uses a dual-evaporator series connection to achieve two different chilled water outlet temperatures—high-temperature chilled water and low-temperature chilled water—while maintaining a constant condensation temperature. The two cold sources are prepared in series through chilled water pipelines. The two refrigeration systems share a condenser and jointly bear the indoor heat and humidity load, thereby effectively increasing the overall evaporation temperature of the air conditioning system and significantly increasing the overall coefficient of performance (COP), achieving energy saving.

[0016] Compared with the prior art, the beneficial effects of this utility model are:

[0017] 1. Under the same cooling capacity, chilled water undergoes heat exchange between a high-temperature evaporator and a low-temperature evaporator, which increases the overall evaporation temperature compared to traditional air conditioning systems, greatly reducing the energy consumption of the entire air conditioning system and improving the operating efficiency of the unit.

[0018] 2. Under the same cooling capacity, the air conditioning system's flow rate is reduced due to the increased temperature difference between the supply and return water, thereby reducing the energy consumption of the delivery system.

[0019] 3. During the transitional season, when the terminal wet load decreases, the entire air conditioning system can be cooled entirely through the high-temperature evaporator, thereby greatly reducing the energy consumption of the air conditioning system's main unit. Attached Figure Description

[0020] Figure 1 This is a system diagram of this utility model.

[0021] Figure 2 This is an operational diagram of an embodiment of a high-temperature refrigeration fault condition according to this utility model. Detailed Implementation

[0022] The technical solution of this utility model will be further described in detail below through embodiments and in conjunction with the accompanying drawings.

[0023] This embodiment describes a dual-evaporator, dual-compressor, dual-cooling-source air conditioning system, such as... Figure 1 As shown, it includes two refrigerant-side loops for cold sources. The high-temperature refrigeration system consists of a high-temperature compressor, a condenser, a high-temperature throttling device, and a high-temperature evaporator forming a loop; the low-temperature refrigeration system consists of a low-temperature compressor, a condenser, a low-temperature throttling device, and a low-temperature evaporator forming a loop.

[0024] The two refrigeration systems share a condenser.

[0025] The process for preparing and applying 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 low-temperature chilled water is generated and supplied to the end; the condenser exchanges heat with cooling water from the cooling tower or other natural cold sources.

[0026] High-temperature evaporators produce high-temperature chilled water with an outlet temperature of 10–17°C, while low-temperature evaporators produce low-temperature chilled water with an outlet temperature of 4–13°C.

[0027] Under the premise of constant condensing temperature, the dual evaporator series configuration can achieve two different chilled water outlet temperatures. The cold source with a relatively lower outlet temperature is the "low-temperature cold source," typically 4–13°C, with a coefficient of performance (COP) of approximately 3–5. The cold source with a relatively higher outlet temperature is the "high-temperature cold source," typically 10–17°C, with a COP as high as 8–9 or higher. The two cold sources are connected in series through chilled water piping to share the indoor heat and humidity load.

[0028] In the chilled water preparation process, the high-temperature chilled water in the high-temperature evaporator can be directly supplied to the end via a separate chilled water bypass pipeline through the electric valve V3.

[0029] A bypass pipe and a two-way electric valve V4 are installed between the chilled water return inlet of the low-temperature evaporator and the low-temperature evaporator. (See also...) Figure 2 .

[0030] This embodiment uses the pressure difference change of the pressure sensor between the supply and return water pipes to feed back the pressure difference signal, which controls the opening of the unit's electric valve. At the same time, based on the main unit's inlet water temperature and the temperature difference between the inlet and outlet water, it completes the operation of cooling under large temperature difference conditions and cooling under transitional season conditions.

[0031] The refrigerant cycle of this system is as follows: Figure 1The dashed route illustrates the refrigerant circulation in a high-temperature refrigeration system. High-temperature refrigerant from the high-temperature evaporator outlet flows into the high-temperature compressor for pressurization and heating. This high-temperature, high-pressure refrigerant then passes through the condenser, exchanging heat with cooling water from a cooling tower or other natural cold source, transforming into a low-temperature, high-pressure refrigerant. Subsequently, it passes through a high-temperature throttling device, becoming a low-pressure refrigerant, and finally exchanges heat with chilled water in the high-temperature evaporator, forming the refrigerant cycle in the high-temperature refrigeration system. Similarly, high-temperature refrigerant from the low-temperature evaporator outlet flows into the low-temperature compressor for pressurization and heating. This high-temperature, high-pressure refrigerant then passes through the condenser, exchanging heat with cooling water from a cooling tower or other natural cold source, transforming into a low-temperature, high-pressure refrigerant. Subsequently, it passes through a low-temperature throttling device, becoming a low-pressure refrigerant, and finally exchanges heat with chilled water in the low-temperature evaporator, forming the refrigerant cycle in the low-temperature refrigeration system.

[0032] Chilled water circulation: such as Figure 1 The solid line route shows that the chilled water return, after being treated at the terminal load, is sent to the high-temperature evaporator for heat exchange via a water collector. The high-temperature chilled water return at 16-23°C, after heat exchange in the high-temperature evaporator, produces high-temperature chilled water at 10-17°C, which is directly sent to the low-temperature evaporator for further heat exchange, producing low-temperature chilled water at 4-13°C. This low-temperature chilled water is then sent to the air conditioning terminals via a water distributor. After heat exchange at the air conditioning terminals, the chilled water return enters the water collector, thus completing the cycle.

[0033] Cooling water circulation: such as Figure 1 The circuit shown by the dotted line shows that the 30-40°C high-temperature cooling water passing through the condenser is transported to the cooling tower or other natural cold source to be cooled down to produce low-temperature cooling water of 25-35°C, and then enters the condenser again to complete the cycle.

[0034] The control principle of this system is as follows: As the load at the end of the water system changes, the pressure difference between the pressure sensors in the supply and return water pipes changes. This pressure difference signal is used to control the opening of the unit's electric valves. Simultaneously, based on the inlet water temperature and the temperature difference between the inlet and outlet water, the system optimizes the unit's operating conditions to ensure efficient operation. Based on this principle, this system can operate under conditions of large temperature difference cooling and cooling during transitional seasons, depending on the end-load demand.

[0035] Control strategy for large temperature difference cooling operation: If the terminal requires low-temperature chilled water, open electric two-way valves V1 and V2 and close electric two-way valve V3 to achieve "large temperature difference cooling operation". The circulation process is as follows: The chilled water return water after being processed by the terminal load is transported to the high-temperature evaporator for heat exchange through the water collector. The high-temperature chilled water return water of 16-23°C generates high-temperature chilled water of 10-17°C after heat exchange in the high-temperature evaporator, and is directly transported to the low-temperature evaporator for further heat exchange, generating low-temperature chilled water of 4-13°C. This low-temperature chilled water is then sent to the air conditioning terminal through the water distributor. The chilled water return water after heat exchange in the air conditioning terminal enters the water collector, thus completing the circulation.

[0036] Control strategy for cooling operation during transitional seasons: During the transitional season, the cooling load of the air conditioner is greatly reduced. In this case, only the electric two-way valve V3 can be opened, while electric two-way valves V1 and V2 are closed to achieve "cooling operation during transitional seasons." The circulation process at this time is as follows: The chilled water return water, after being processed by the terminal load, is transported to the high-temperature evaporator through the water collector for heat exchange. The high-temperature chilled water return water (16-23°C) generates high-temperature chilled water (10-17°C) after heat exchange in the high-temperature evaporator. This high-temperature chilled water is directly transported to the water distributor via the bypass pipeline and electric two-way valve V3, and then to the air conditioning terminals for cooling. After heat exchange at the air conditioning terminals, the chilled water return water enters the water collector, thus completing the circulation.

[0037] Furthermore, the control strategy for transitional season refrigeration conditions is also applicable to operation control when the low-temperature evaporator or low-temperature refrigeration system fails. Correspondingly, when the high-temperature evaporator or high-temperature refrigeration system fails, a bypass pipeline and an electric two-way valve V4 can be added between the chilled water return inlet of the low-temperature evaporator and the low-temperature evaporator. See also... Figure 2 Open the electric two-way valve V4 and electric two-way valves V1 and V2, and close the electric two-way valve V3 to enable the air conditioning system to complete low-temperature cooling.

[0038] The above embodiments are illustrative of the present invention and not intended to limit the present invention. The described embodiments are merely some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

Claims

1. A dual-evaporator, dual-compressor dual-cooling-source air conditioning system, characterized in that: It includes two refrigerant-side loops for the cold source. The high-temperature refrigeration system consists of a high-temperature compressor, condenser, high-temperature throttling device, and high-temperature evaporator forming a loop, while the low-temperature refrigeration system consists of a low-temperature compressor, condenser, low-temperature throttling device, and low-temperature evaporator forming a loop. The two refrigeration systems share a condenser. The preparation and application process of chilled water is as follows: high-temperature chilled water in the high-temperature evaporator is directly transported to the low-temperature evaporator for low-temperature heat exchange, producing low-temperature chilled water for supply to the terminal. The condenser exchanges heat with cooling water from a cooling tower or natural cold source. In the chilled water preparation process, the high-temperature chilled water in the high-temperature evaporator can be directly supplied to the end via a separate chilled water bypass pipeline and an electric valve V3; a bypass pipeline and an electric valve V4 are provided between the chilled water return inlet of the low-temperature evaporator and the low-temperature evaporator.

2. The dual-evaporator, dual-compressor, dual-cooling-source air conditioning system according to claim 1, characterized in that, The high-temperature evaporator produces high-temperature chilled water with an outlet temperature of 10–17°C, and the low-temperature evaporator produces low-temperature chilled water with an outlet temperature of 4–13°C.

3. A dual-evaporator, dual-compressor dual-cold-source air conditioning system according to claim 1, characterized in that the refrigerant circulation is as follows: the high-temperature refrigerant from the outlet of the high-temperature evaporator flows into the high-temperature compressor for pressurization and heating; the high-temperature, high-pressure refrigerant passes through the condenser and exchanges heat with the cooling water to become a low-temperature, high-pressure refrigerant; then it passes through the high-temperature throttling device to become a low-pressure refrigerant; finally, it passes through the high-temperature evaporator for heat exchange with the chilled water and returns to the high-temperature compressor to form a cycle; the high-temperature refrigerant from the outlet of the low-temperature evaporator flows into the low-temperature compressor for pressurization and heating; the high-temperature, high-pressure refrigerant passes through the condenser and exchanges heat with the cooling water to become a low-temperature, high-pressure refrigerant; then it passes through the low-temperature throttling device to become a low-pressure refrigerant; finally, it passes through the low-temperature evaporator for heat exchange with the chilled water and returns to the low-temperature compressor to form a cycle.

4. A dual-evaporator, dual-compressor, dual-cooling-source air conditioning system according to claim 1 or 2, characterized in that, Chilled water circulation: The chilled water returned after end-load treatment is sent to the high-temperature evaporator for heat exchange via a water collector.

5. A dual-evaporator, dual-compressor dual-cooling-source air conditioning system according to claim 4, characterized in that, The high-temperature chilled water returning from the water collector is heated by heat exchange in the high-temperature evaporator to produce high-temperature chilled water of 10-17°C. This high-temperature chilled water is then directly transported to the low-temperature evaporator for further heat exchange, producing low-temperature chilled water of 4-13°C. This low-temperature chilled water is then sent to the air conditioning terminals through the water distributor. After heat exchange at the air conditioning terminals, the chilled water returns to the water collector to complete the circulation.

6. The dual-evaporator, dual-compressor dual-cooling-source air conditioning system according to claim 1, characterized in that, The pressure difference signal is fed back by the pressure sensor between the supply and return water pipes to control the opening of the unit's electric valve. At the same time, the unit can operate under large temperature difference cooling conditions and transitional season cooling conditions based on the main unit's inlet water temperature and the temperature difference between the inlet and outlet water.

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