Defrosting control method for heat recovery unit and heat recovery unit

Abstract

The application discloses a defrosting control method of a heat recovery unit and the heat recovery unit. The heat recovery unit comprises a compressor unit and a heat exchanger combination. The heat exchanger combination comprises an air conditioner water heat exchanger, a hot water heat exchanger and an outdoor heat exchanger. The compressor unit can be connected with any two heat exchangers in the heat exchanger combination to form a refrigerant circulation loop. The defrosting control method is that when a user needs only a single heating mode, the idle heat exchanger is converted into an evaporator; and when the user needs both heating and hot water, the hot water heat exchanger and the air conditioner water heat exchanger are alternately used as the evaporator. According to the defrosting control method, the evaporator configuration is dynamically adjusted according to the supply demand of the heat recovery unit, the heat capacity of the idle heat exchanger and the working heat exchanger is fully utilized, the temperature fluctuation of the user side caused by defrosting is reduced to the maximum extent, the use experience of the user is improved, and the reliability of the unit is ensured.

Description

Technical Field

[0001] This invention relates to the field of heat pump unit technology, and in particular to a defrosting control method for heat recovery units and heat recovery units. Background Technology

[0002] Heat recovery units, as highly efficient and energy-saving devices, are widely used in hotels, hospitals, swimming pools, and other places requiring a continuous supply of hot water. They heat domestic or process water by recovering the condensation heat generated by the refrigeration system, significantly reducing energy consumption compared to traditional heating methods. However, when the unit operates in low-temperature environments, frost inevitably forms on the evaporator surface, leading to decreased heating efficiency or even system failure. In this case, the unit must enter defrosting mode to restore performance.

[0003] Currently, most mainstream heat recovery units employ defrosting methods such as reverse circulation or hot gas bypass. In heat recovery units with multiple heat exchangers (e.g., including both air conditioning water heat exchangers and hot water heat exchangers), when users require only a single heating mode, one heat exchanger is always idle, resulting in wasted resources due to inefficient utilization of idle capacity. When users require both heating and hot water simultaneously, although both heat exchangers are operational, traditional control strategies still employ a single defrosting path, failing to minimize disruption to the heating side during the defrosting process.

[0004] Furthermore, in combined systems employing plate heat exchangers (air conditioning water heat exchangers) and shell-and-tube heat exchangers (hot water heat exchangers), the refrigerant's counter-current flow during defrosting can easily create liquid pockets within the narrow channels of the heat exchangers. Sudden increases or decreases in localized temperature can lead to freezing and cracking. Existing defrosting controls fail to dynamically adjust the evaporator configuration according to user load demands, resulting in low defrosting efficiency and concentrated risks.

[0005] Therefore, how to design defrosting control methods and heat recovery units that can reduce water temperature fluctuations on the user side while achieving efficient defrosting is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0006] To address the shortcomings of existing heat recovery units, such as low defrosting efficiency and concentrated risks, this invention proposes a defrosting control method and a heat recovery unit. The method dynamically adjusts the evaporator configuration according to the supply demand of the heat recovery unit, making full use of the heat capacity of idle and working heat exchangers, minimizing temperature fluctuations on the user side during defrosting, improving the user experience, and ensuring the reliability of the unit.

[0007] The technical solution adopted in this invention is to design a defrosting control method for a heat recovery unit. The heat recovery unit includes a compressor unit and a heat exchanger assembly. The heat exchanger assembly includes an air conditioning water heat exchanger, a hot water heat exchanger, and an outdoor heat exchanger. The compressor unit can be connected to any two heat exchangers in the heat exchanger assembly to form a refrigerant circulation loop.

[0008] Defrosting control methods include:

[0009] When the heat recovery unit reaches the defrosting entry condition, the refrigerant circulation loop is controlled to enter the refrigeration cycle, and the outdoor heat exchanger is used as the condenser for defrosting. The current supply and demand of the heat recovery unit are analyzed.

[0010] If the heat recovery unit has both heating and hot water requirements, the hot water heat exchanger and the air conditioning water heat exchanger will be used alternately as evaporators in the refrigerant circulation loop.

[0011] If the heat recovery unit has heating needs but no hot water needs, then the hot water heat exchanger and the air conditioning water heat exchanger are connected to the refrigerant circulation loop as evaporators in turn.

[0012] If the heat recovery unit has no heating demand but has a hot water demand, then the air conditioning water heat exchanger and the hot water heat exchanger are connected to the refrigerant circulation loop as evaporators.

[0013] Furthermore, the alternating use of hot water heat exchangers and air conditioning water heat exchangers as evaporators in the refrigerant circulation loop includes:

[0014] If the actual water temperature T1 of the hot water heat exchanger is greater than the set lower limit temperature A1 for hot water production, or the actual water temperature T2 of the air conditioning water heat exchanger is greater than the set lower limit temperature A2 for heating, then the hot water heat exchanger will be switched to an evaporator first. When the actual water temperature T1 is less than or equal to the set lower limit temperature A1 for hot water production, the air conditioning water heat exchanger will be switched to an evaporator.

[0015] If the actual water temperature T1 of the hot water heat exchanger is less than or equal to the set lower limit temperature A1 for hot water and the actual water temperature T2 of the air conditioning water heat exchanger is less than or equal to the set lower limit temperature A2 for heating, then the hot water heat exchanger is switched to the evaporator first. When the actual water temperature T1 is less than or equal to the set antifreeze temperature H1 for hot water, the air conditioning water heat exchanger is switched to the evaporator.

[0016] Among them, A1 > H1, A2 > H2.

[0017] Furthermore, hot water heat exchangers and air conditioning water heat exchangers are successively connected as evaporators into the refrigerant circulation loop, including:

[0018] If the actual water temperature T1 of the hot water heat exchanger is greater than the set hot water antifreeze temperature H1, the hot water heat exchanger will be switched to an evaporator first. When the actual water temperature T1 of the hot water heat exchanger is less than or equal to the set hot water antifreeze temperature H1, the air conditioning water heat exchanger will be switched to an evaporator.

[0019] Furthermore, the air conditioning water heat exchanger and hot water heat exchanger are successively connected as evaporators in the refrigerant circulation loop, including:

[0020] If the actual water temperature T2 of the air conditioner water heat exchanger is greater than the set air conditioner water antifreeze temperature H2, the air conditioner water heat exchanger will be switched to an evaporator first. When the actual water temperature T2 is less than or equal to the set air conditioner water antifreeze temperature H2, the hot water heat exchanger will be switched to an evaporator.

[0021] Furthermore, the defrosting entry conditions include power-on defrosting entry conditions and normal defrosting entry conditions;

[0022] Defrosting control methods include:

[0023] Monitor the operating status of the heat recovery unit;

[0024] When the compressor unit of the heat recovery unit is not working and a start command is received, it is determined whether the operating parameters of the heat recovery unit meet the start defrosting conditions. If so, the refrigerant circulation loop is controlled to enter the refrigeration cycle.

[0025] When the compressor unit of the heat recovery unit is in operation, it is determined whether the operating parameters of the heat recovery unit meet the conditions for entering the conventional defrosting cycle. If so, the refrigerant circulation loop is controlled to enter the refrigeration cycle.

[0026] Furthermore, the conditions for starting defrost are that the continuous static time of the compressor unit is greater than or equal to the set standby time N, and the outdoor ambient temperature is less than or equal to the set lower limit temperature M.

[0027] Furthermore, the defrosting control method includes: forcibly discontinuing defrosting when the heat recovery unit reaches the antifreeze withdrawal condition;

[0028] The antifreeze withdrawal condition is that the actual water temperature T1 of the hot water heat exchanger is less than or equal to the set hot water antifreeze temperature H1 and the actual water temperature T2 of the air conditioning water heat exchanger is less than or equal to the set air conditioning water antifreeze temperature H2.

[0029] Furthermore, the defrosting control method also includes: after defrosting the outdoor heat exchanger as a condenser, defrosting is stopped when the heat recovery unit reaches the normal defrosting shutdown conditions;

[0030] The conventional defrosting exit conditions include at least one of the following: defrosting time exit conditions, defrosting temperature exit conditions, and exhaust pressure exit conditions.

[0031] In some embodiments, the hot water heat exchanger is a shell-and-tube heat exchanger or a double-tube heat exchanger, and the air conditioning water heat exchanger is a plate heat exchanger; wherein, H2 > H1.

[0032] The present invention also proposes a heat recovery unit, comprising: a compressor unit and a heat exchanger assembly, the heat exchanger assembly including an air conditioning water heat exchanger, a hot water heat exchanger, and an outdoor heat exchanger, the compressor unit being able to connect to any two heat exchangers in the heat exchanger assembly to form a refrigerant circulation loop; the heat recovery unit adopts the above-mentioned defrosting control method.

[0033] Furthermore, the heat recovery unit also includes: a liquid receiver, the exhaust side of the compressor unit can be switched to connect to the first end of any heat exchanger in the heat exchanger assembly, and the second end of each heat exchanger is connected to the inlet pipe of the liquid receiver through a valve;

[0034] The second end of the air conditioner water heat exchanger is connected to the second end of the outdoor heat exchanger through a throttling pipe. The throttling pipe is connected in series with a first throttling valve and a second throttling valve. The outlet pipe of the liquid receiver is connected between the first throttling valve and the second throttling valve.

[0035] The second end of the hot water heat exchanger is connected between the first throttling valve and the second throttling valve via a defrosting branch. The defrosting branch is equipped with a throttling element and a control valve for switching on and off states.

[0036] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0037] 1. Dynamically adjust the evaporator configuration according to the supply demand of the heat recovery unit, control the order in which the hot water heat exchanger and the air conditioning water heat exchanger are connected to the refrigerant circulation loop, make full use of the heat capacity of idle heat exchangers and working heat exchangers, minimize the temperature fluctuations on the user side during defrosting, improve the user experience, and reduce the risk of heat exchanger freezing damage.

[0038] 2. Match defrosting conditions according to the operating status of the compressor unit of the heat recovery unit. When the unit is in a low-temperature non-working state for a long time, after receiving the start command, control the refrigerant circulation loop to enter the refrigeration cycle, avoid the compressor unit lacking oil or the oil temperature being too low, reduce the risk of the compressor unit freezing and ensure the reliability of the heat recovery unit. Attached Figure Description

[0039] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:

[0040] Figure 1 This is a schematic diagram of the system connection of the heat recovery unit of the present invention;

[0041] Figure 2 This is a schematic diagram of the flow direction in the hot water mode of the present invention;

[0042] Figure 3 This is a schematic diagram of the flow direction of the heating mode of the present invention;

[0043] Figure 4 This is a schematic diagram of the cooling mode of the present invention;

[0044] Figure 5 This is a schematic diagram of the flow direction of the cooling and heating water mode of the present invention;

[0045] Figure 6 This is a schematic flowchart of the defrosting control method of the present invention;

[0046] Figure 7 This is a schematic diagram of the switching logic of a preferred embodiment of the present invention;

[0047] Figure 8 This is a schematic diagram of the defrosting process according to a preferred embodiment of the present invention;

[0048] Figure 9 This is a schematic diagram of the defrosting flow direction of the hot water heat exchanger used as an evaporator in this invention;

[0049] Figure 10 This is a schematic diagram of the defrosting flow direction of the air conditioner water heat exchanger used as an evaporator in this invention;

[0050] Figure descriptions: 1. Compressor unit; 2. Air conditioning water heat exchanger; 3. Hot water heat exchanger; 4. Outdoor heat exchanger; 5. Liquid receiver; 6. Control valve; 7. First check valve; 8. Second check valve; 9. Third check valve; 10. First throttle valve; 11. Second throttle valve; 12. Throttling element; 13. First four-way valve; 14. Second four-way valve; 15. Variable frequency drive module; 16. Gas-liquid separator; 17. Third four-way valve; 18. Oil separator; 19. Oil return valve. Detailed Implementation

[0051] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0052] like Figure 1 As shown, the defrosting control method proposed in this invention is applicable to heat recovery units. The heat recovery unit includes: a compressor unit 1 and a heat exchanger assembly. The compressor unit 1 includes at least one compressor, and the heat exchanger assembly includes an air conditioning water heat exchanger 2, a hot water heat exchanger 3, and an outdoor heat exchanger 4. The compressor unit 1 can be connected to any two heat exchangers in the heat exchanger assembly to form a refrigerant circulation loop. The working modes of the heat recovery unit include hot water mode, heating mode, heating water heating mode, cooling mode, and cooling water heating mode. The unit switches the working mode according to the user's usage needs.

[0053] like Figures 2 to 5As shown, when only hot water is needed, the heat recovery unit operates in hot water mode, the refrigerant circulation loop enters the heating cycle, the hot water heat exchanger 3 acts as the condenser, and the outdoor heat exchanger 4 acts as the evaporator; when only heating is needed, the heat recovery unit operates in heating mode, the refrigerant circulation loop enters the heating cycle, the air conditioning water heat exchanger 2 acts as the condenser, and the outdoor heat exchanger 4 acts as the evaporator; when both heating and hot water are needed, the heat recovery unit operates in heating and hot water heating mode, prioritizing heating and hot water needs by using either the air conditioning water heat exchanger 2 or the hot water heat exchanger 3 as the condenser, and the outdoor heat exchanger 4 as the evaporator; when only cooling is needed, the heat recovery unit operates in cooling mode, the refrigerant circulation loop enters the cooling cycle, the air conditioning water heat exchanger 2 acts as the evaporator, and the outdoor heat exchanger 4 acts as the condenser; when both cooling and hot water are needed, the heat recovery unit operates in cooling and hot water heating mode, the refrigerant circulation loop enters the cooling cycle, the air conditioning water heat exchanger 2 acts as the evaporator, and the hot water heat exchanger 3 acts as the condenser.

[0054] For applications in low-temperature environments, the common operating modes of heat recovery units are hot water mode, heating mode, and heating water supply mode. After prolonged heating cycles, outdoor heat exchanger 4 will experience frost formation, leading to decreased heating efficiency or even system failure. In this case, the unit must enter defrosting mode to restore performance. Based on this, the defrosting control method proposed in this invention dynamically adjusts the evaporator configuration according to the supply demand of the heat recovery unit, fully utilizing the heat capacity of idle and working heat exchangers, minimizing temperature fluctuations on the user side during defrosting, improving the user experience, and ensuring the reliability of the unit.

[0055] like Figure 6 As shown, specifically, defrosting control methods include:

[0056] When the heat recovery unit reaches the defrosting entry condition, the refrigerant circulation loop is controlled to enter the refrigeration cycle, and the outdoor heat exchanger 4 is used as a condenser for defrosting. The current supply demand of the heat recovery unit is analyzed.

[0057] If the heat recovery unit has heating and hot water needs, it means that both the hot water heat exchanger 3 and the air conditioning water heat exchanger 2 are working heat exchangers that need to supply heat to the user side. The hot water heat exchanger 3 and the air conditioning water heat exchanger 2 are alternately connected to the refrigerant circulation loop as evaporators.

[0058] If the heat recovery unit has heating demand but no hot water demand, it means that the hot water heat exchanger 3 is an idle heat exchanger. The hot water heat exchanger 3 and the air conditioning water heat exchanger 2 are connected to the refrigerant circulation loop as evaporators in turn. Here, the hot water heat exchanger 3 is given priority. The hot water heat exchanger 3 is connected to the refrigerant circulation loop as an evaporator first, and then the air conditioning water heat exchanger 2 is connected to the refrigerant circulation loop as an evaporator.

[0059] If the heat recovery unit has no heating demand but has a hot water demand, it means that the air conditioning water heat exchanger 2 is an idle heat exchanger. The air conditioning water heat exchanger 2 and the hot water heat exchanger 3 are connected to the refrigerant circulation loop as evaporators in turn. Here, the air conditioning water heat exchanger 2 is given priority. The air conditioning water heat exchanger 2 is connected to the refrigerant circulation loop as an evaporator first, and then the hot water heat exchanger 3 is connected to the refrigerant circulation loop as an evaporator.

[0060] Existing defrosting solutions typically employ a single defrosting path, leading to significant fluctuations in water temperature. This new design, however, converts idle heat exchangers into evaporators when the user requires only a single heating mode. This fully utilizes the heat from the idle heat exchanger to defrost the outdoor heat exchanger, reducing water temperature fluctuations on the user's side. When the user needs both heating and hot water simultaneously, the hot water heat exchanger and the air conditioning water heat exchanger are used alternately as evaporators. The cold energy absorbed during defrosting is distributed across both heat exchangers, resulting in a smooth temperature decrease on both the heating and hot water sides, further reducing water temperature fluctuations on the user's side.

[0061] like Figure 7 As shown, in order to optimize energy distribution during the defrosting process, in some preferred embodiments of the present invention, the switching logic between the hot water heat exchanger 3 and the air conditioning water heat exchanger 2 is designed as follows:

[0062] If the actual water temperature T1 of the hot water heat exchanger 3 is greater than the set lower limit temperature A1 for hot water production, or the actual water temperature T2 of the air conditioning water heat exchanger 2 is greater than the set lower limit temperature A2 for heating, it indicates that there is excess heat in the hot water heat exchanger 3 or the air conditioning water heat exchanger 2. First, switch the hot water heat exchanger 3 to the evaporator and use the excess heat of the hot water heat exchanger 3 to defrost the outdoor heat exchanger 4. When the actual water temperature T1 is less than or equal to the set lower limit temperature A1 for hot water production, switch the air conditioning water heat exchanger 2 to the evaporator and use the excess heat of the air conditioning water heat exchanger 2 to defrost the outdoor heat exchanger 4.

[0063] If the actual water temperature T1 of the hot water heat exchanger 3 is less than or equal to the set lower limit temperature A1 for hot water and the actual water temperature T2 of the air conditioning water heat exchanger 2 is less than or equal to the set lower limit temperature A2 for heating, it means that there is no surplus heat in either the hot water heat exchanger 3 or the air conditioning water heat exchanger 2. First, switch the hot water heat exchanger 3 to the evaporator and use the remaining heat of the hot water heat exchanger 3 to defrost the outdoor heat exchanger 4. When the actual water temperature T1 is less than or equal to the set antifreeze temperature H1 for hot water, switch the air conditioning water heat exchanger 2 to the evaporator and use the remaining heat of the air conditioning water heat exchanger 2 to defrost the outdoor heat exchanger 4.

[0064] Among them, A1 > H1, A2 > H2.

[0065] This design prioritizes hot water heat exchanger 3 as the initial evaporator because its target temperature is typically higher, allowing it to store more heat and absorb the cooling energy required for defrosting more efficiently. This reduces compressor unit power consumption and defrosting time, while maximizing system capacity utilization. More importantly, through a tiered temperature design (A1→H1, A2→H2), hot water heat exchanger 3 and air conditioning water heat exchanger 2 are alternately connected to the refrigerant circulation loop. This prevents the water temperature of a single heat exchanger from dropping rapidly in a short period, ensuring that the user-side water temperature fluctuates gradually and gradually during the defrosting process, thus improving the user experience.

[0066] like Figure 7 As shown, to prevent the risk of freezing during the defrosting process, in some preferred embodiments of the present invention, the switching logic between the hot water heat exchanger 3 and the air conditioning water heat exchanger 2 is designed as follows:

[0067] If the actual water temperature T1 of the hot water heat exchanger 3 is greater than the set hot water antifreeze temperature H1, it means that the hot water heat exchanger 3 has no risk of freezing. First, switch the hot water heat exchanger 3 to the evaporator and use the remaining heat of the idle heat exchanger to defrost the outdoor heat exchanger 4. When the actual water temperature T1 of the hot water heat exchanger 3 is less than or equal to the set hot water antifreeze temperature H1, then switch the air conditioner water heat exchanger 2 to the evaporator and use the heat of the air conditioner water heat exchanger 2 to defrost the outdoor heat exchanger 4.

[0068] To prevent the risk of freezing during the defrosting process, in some preferred embodiments of the present invention, the switching logic between the air conditioner water heat exchanger 2 and the hot water heat exchanger 3 is designed as follows:

[0069] If the actual water temperature T2 of the air conditioner water heat exchanger 2 is greater than the set air conditioner water antifreeze temperature H2, it means that the air conditioner water heat exchanger 2 has no risk of freezing. First, switch the air conditioner water heat exchanger 2 to the evaporator and use the remaining heat of the idle heat exchanger to defrost the outdoor heat exchanger 4. When the actual water temperature T2 is less than or equal to the set air conditioner water antifreeze temperature H2, then switch the hot water heat exchanger 3 to the evaporator.

[0070] The switching logic described above compares real-time water temperature with the antifreeze temperature threshold, always prioritizing the use of idle heat exchangers with no risk of freezing for defrosting. Only when the temperature of an idle heat exchanger drops below the antifreeze threshold is the system switched to another heat exchanger. This approach effectively utilizes the residual heat of idle heat exchangers, reducing temperature fluctuations on the user side, prevents heat exchangers from freezing due to overcooling, and enables continuous defrosting through heat exchanger switching, thus improving defrosting efficiency.

[0071] When the unit is idle or shut down for an extended period in a low-temperature environment, the lubricating oil in compressor unit 1 will absorb a large amount of refrigerant, causing the lubricating oil to become diluted and its viscosity to decrease. Simultaneously, the refrigerant itself may also accumulate at the lowest point of the system or in the coldest components (such as the outdoor heat exchanger) due to gravity. If there is a need to start the unit at this time, directly starting the unit into the heating cycle poses a risk of oil shortage in the compressor unit. The diluted lubricating oil cannot effectively lubricate critical components such as the compressor unit bearings. Furthermore, the refrigerant accumulated elsewhere cannot be quickly drawn back into the compressor unit, resulting in the compressor unit being in an oil-deficient state during the initial startup phase. This may lead to accelerated wear, cylinder seizure, or even burnout and other serious malfunctions. Additionally, during shutdown, the surface of the outdoor heat exchanger may have frosted or frozen over. Direct heating can easily lead to problems such as reduced heating capacity and a sudden increase in energy consumption due to excessive frost buildup.

[0072] Based on this, in some preferred embodiments of the present invention, defrosting entry conditions are designed, including power-on defrosting entry conditions and normal defrosting entry conditions.

[0073] like Figure 8 As shown, the defrosting control methods include:

[0074] Monitor the operating status of the heat recovery unit;

[0075] When the compressor unit 1 of the heat recovery unit is not working and receives a start command, it is determined whether the operating parameters of the heat recovery unit meet the start-up defrosting conditions. If so, the refrigerant circulation loop is controlled to enter the refrigeration cycle, quickly recovering refrigerant and lubricating oil to ensure sufficient lubrication of compressor unit 1. At the same time, it melts the initial frost layer that may exist, solving problems such as refrigerant migration, lubricating oil dilution or frost accumulation after long-term shutdown, and preventing compressor unit from lacking oil or being inefficient due to direct start-up.

[0076] When the compressor unit of the heat recovery unit is in operation, it is determined whether the operating parameters of the heat recovery unit meet the normal defrosting entry conditions. If so, the refrigerant circulation loop is controlled to enter the refrigeration cycle to avoid excessive frost during operation, which may lead to decreased heating efficiency, increased energy consumption, or system failure.

[0077] This design distinguishes between the conditions for starting up and the conditions for regular defrosting, and intelligently triggers defrosting based on the compressor unit's status. This fills the gap in the traditional defrosting control during the "start-up phase" and forms a complete closed loop with "regular defrosting during operation." It covers comprehensive defrosting management of the unit from startup to operation, improves unit reliability and energy efficiency, and enhances the user experience.

[0078] Based on the above optimized embodiments, a preferred solution is to set the start-up defrosting conditions to be a continuous idle time of the compressor unit ≥ a set standby time N, and an outdoor ambient temperature ≤ a set lower limit temperature M. The idle time (≥ N) determines whether compressor unit 1 is in a long-term shutdown state (refrigerant may have migrated), and the low-temperature condition (≤ M) confirms the environment with a risk of frost formation. Both constitute a "high-risk start-up" trigger logic, ensuring that defrosting pre-treatment is only initiated when necessary, avoiding unnecessary energy consumption or interference. For example, if N = 6 hours and M = 5°C, if the unit receives a compressor unit start-up command after being shut down for 8 hours in a 0°C environment, it is automatically identified as requiring defrosting pre-treatment. If the compressor unit 1 start-up command is received after only 2 hours of shutdown or when the ambient temperature is 10°C, it directly enters the heating cycle.

[0079] To prevent heat exchangers from freezing and cracking, in some preferred embodiments of the present invention, the defrosting control method includes: forcibly discontinuing defrosting when the heat recovery unit reaches the anti-freeze discontinuation condition; the anti-freeze discontinuation condition is that the actual water temperature T1 of the hot water heat exchanger is ≤ the set hot water anti-freeze temperature H1 and the actual water temperature T2 of the air conditioning water heat exchanger is ≤ the set air conditioning water anti-freeze temperature H2. This design utilizes the anti-freeze discontinuation condition to protect the hot water heat exchanger and the air conditioning water heat exchanger, preventing the heat exchangers from freezing and cracking due to excessive cooling, and enhancing the reliability of the unit.

[0080] It should be understood that after the outdoor heat exchanger 4, acting as a condenser, defrosts the heat recovery unit, in addition to the forced exit from defrosting when the antifreeze exit condition is met, there are also normal defrosting exit conditions designed for normal exit. These normal defrosting exit conditions include at least one of the following: defrosting time exit condition, defrosting temperature exit condition, and exhaust pressure exit condition. For example, for the defrosting time exit condition, a maximum defrosting time (e.g., 10-15 minutes) is set to prevent the defrosting process from becoming too long; for the defrosting temperature exit condition, the surface temperature of the outdoor heat exchanger 4 or the temperature at relevant points (e.g., the evaporation temperature rises to the set value) is monitored to directly determine whether the frost layer has completely melted, ensuring thorough defrosting and restoring heat exchange efficiency; for the exhaust pressure exit condition, a maximum exhaust pressure is set to ensure the stability of the unit system.

[0081] Throughout the defrosting process, the heat recovery unit will exit defrosting when either the antifreeze exit condition or the conventional defrosting exit condition is met. This design ensures the flexibility and safety of the defrosting process through parallel monitoring and arbitrary triggering mechanisms of the antifreeze exit condition and the conventional defrosting exit condition (time, temperature, pressure), reducing unnecessary defrosting delays or risk accumulation.

[0082] It should be noted that the outdoor heat exchanger 4 in the heat recovery unit is usually a finned heat exchanger, while the hot water heat exchanger 3 is usually a shell-and-tube or coaxial heat exchanger. Shell-and-tube / coaxial heat exchangers are suitable for high-temperature and high-pressure conditions. The air conditioning water heat exchanger 2 is usually a plate heat exchanger, which is suitable for medium- and low-temperature conditions. The hot water heat exchanger 3 has better antifreeze capability than the air conditioning water heat exchanger, i.e., H2 > H1. Therefore, during the defrosting process, the hot water heat exchanger 3 should be preferentially connected to the refrigerant circulation loop as an evaporator.

[0083] like Figure 1 As shown, the present invention also proposes a heat recovery unit, including: a compressor unit 1 and a heat exchanger assembly, the heat exchanger assembly including an air conditioning water heat exchanger 2, a hot water heat exchanger 3, and an outdoor heat exchanger 4, the compressor unit 1 can be connected to any two heat exchangers in the heat exchanger assembly to form a refrigerant circulation loop; the heat recovery unit adopts the above-mentioned defrosting control method.

[0084] This defrosting control method dynamically adjusts the evaporator configuration based on the supply demand of the heat recovery unit, controls the order in which the hot water heat exchanger and the air conditioning water heat exchanger are connected to the refrigerant circulation loop, fully utilizes the heat capacity of idle and working heat exchangers, minimizes temperature fluctuations on the user side during defrosting, improves the user experience, and reduces the risk of heat exchanger freezing. Preferably, this defrosting control method also matches the defrosting initiation conditions to the compressor unit's operating status. When the unit is in a low-temperature, inactive state for an extended period, upon receiving a start-up command, it controls the refrigerant circulation loop to enter the refrigeration cycle, preventing compressor oil shortages or excessively low oil temperatures, reducing the risk of compressor freezing, and ensuring the reliability of the heat recovery unit.

[0085] like Figure 1 As shown, in some preferred embodiments of the present invention, the heat recovery unit further includes: a liquid receiver 5, and the frequency conversion drive module 15 of the heat recovery unit is equipped with a heat dissipation pipe. The heat dissipation pipe is connected in series with the inlet pipe of the liquid receiver 5 so that the refrigerant sent to the liquid receiver 5 passes through the heat dissipation pipe.

[0086] For ease of understanding, the three heat exchangers are referred to as air conditioning water heat exchanger 2, hot water heat exchanger 3, and outdoor heat exchanger 4, respectively. The first and second ends of each heat exchanger are marked on the connection diagram of the heat recovery system, with the first end marked as "①" and the second end marked as "②".

[0087] Compressor unit 1 is connected to three heat exchangers via a first four-way valve 13 and a second four-way valve 14, allowing the discharge side of compressor unit 1 to switch between the first end ① of any heat exchanger. The second end ② of each heat exchanger is connected to the inlet pipe of receiver 5 via valves. When compressor unit 1 is connected to the first end ① of a heat exchanger, that heat exchanger acts as a condenser, and the second end ② of the heat exchanger is the condenser outlet side. The refrigerant flowing out from the second end ② can enter receiver 5 through the valves.

[0088] The second end ② of the air conditioning water heat exchanger 2 is connected to the second end ② of the outdoor heat exchanger 4 through a throttling pipe. The throttling pipe is connected in series with a first throttling valve 10 and a second throttling valve 11. The first throttling valve 10 is close to the air conditioning water heat exchanger 2, and the second throttling valve 11 is close to the outdoor heat exchanger 4. The outlet pipe of the liquid receiver 5 is connected between the first throttling valve 10 and the second throttling valve 11. The refrigerant flowing out of the liquid receiver 5 can enter the air conditioning water heat exchanger 2 through the first throttling valve 10, and the refrigerant flowing out of the main line can also enter the outdoor heat exchanger 4 through the second throttling valve 11. The specific flow direction depends on the working mode of the heat recovery system.

[0089] The second end ② of the hot water heat exchanger 3 is connected between the first throttling valve 10 and the second throttling valve 11 via a defrost branch. Specifically, one end of the defrost branch is connected to the second end of the hot water heat exchanger 3, and the other end is connected between the first throttling valve 10 and the second throttling valve 11. The defrost branch is equipped with a throttling element 12 and a control valve 6, which switches the on / off state of the defrost branch. The control valve 6 is open when the outdoor heat exchanger 4 is used as a condenser and the hot water heat exchanger 3 is used as an evaporator. The first throttling valve 10 and the second throttling valve 11 are both closed when the control valve 6 is open.

[0090] like Figure 9 As shown, when the refrigerant circulation loop enters the refrigeration cycle and the hot water heat exchanger 3 acts as the evaporator, the first end ① of the outdoor heat exchanger 4 is connected to the exhaust side of the compressor unit 1. The outdoor heat exchanger acts as the condenser, and the air conditioning water heat exchanger 2 does not participate in the refrigerant circulation. The flow direction of the refrigerant circulation loop is compressor unit 1 → outdoor heat exchanger 4 → liquid receiver 5 → hot water heat exchanger 3 → back to compressor unit 1.

[0091] like Figure 10 As shown, when the refrigerant circulation loop enters the refrigeration cycle and the air conditioner water heat exchanger 2 acts as the evaporator, the first end ① of the outdoor heat exchanger 4 is connected to the exhaust side of the compressor unit 1. The outdoor heat exchanger 4 acts as the condenser, and the hot water heat exchanger 3 does not participate in the refrigerant circulation. The flow direction of the refrigerant circulation loop is compressor unit 1 → outdoor heat exchanger 4 → liquid receiver 5 → air conditioner water heat exchanger 2 → back to compressor unit 1.

[0092] This design allows for flexible switching of the connection relationship between the three heat exchangers to meet different user needs. The refrigerant distribution status of the three heat exchangers is controlled by the first throttle valve 10 and the second throttle valve 11. While maintaining pipeline simplicity, it achieves high-precision regulation of refrigerant flow rate and direction, making it particularly suitable for heat recovery units with diverse operating modes. The valves mentioned above can be switchable control valves or check valves. The check valve for the air conditioning water heat exchanger 2 is the second check valve 8, the check valve for the hot water heat exchanger 3 is the first check valve 7, and the check valve for the outdoor heat exchanger 4 is the third check valve 9. Utilizing the unidirectional flow characteristic of the check valves, it ensures that the refrigerant can only flow from the heat exchanger to the receiver 5, avoiding reverse refrigerant flow during mode switching that could cause system pressure disturbances or efficiency reduction. No additional electrical control signals are required, reducing the complexity of valve regulation.

[0093] It should be noted that the terminology used above is for describing specific embodiments only and is not intended to limit the exemplary embodiments of the present invention. When the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof. The order of execution of actions, steps, etc., in the apparatus and methods shown in the specification and drawings may be implemented in any order unless a specific express order is specified, and as long as the output of a previous process is not used in a subsequent process. Similar sequential terms used for ease of description do not imply that such an order must be followed.

[0094] Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and apparatus should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as constraints. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0095] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A defrosting control method for a heat recovery unit, wherein the heat recovery unit comprises: A compressor unit and a heat exchanger assembly, wherein the heat exchanger assembly includes an air conditioning water heat exchanger, a hot water heat exchanger, and an outdoor heat exchanger, and the compressor unit can be connected to any two heat exchangers in the heat exchanger assembly to form a refrigerant circulation loop. The defrosting control method is characterized by comprising: When the heat recovery unit reaches the defrosting entry condition, the refrigerant circulation loop is controlled to enter the refrigeration cycle, and the outdoor heat exchanger is used as a condenser for defrosting. The current supply demand of the heat recovery unit is analyzed. If the heat recovery unit has heating and hot water production needs, the hot water heat exchanger and the air conditioning water heat exchanger are alternately connected to the refrigerant circulation loop as evaporators. If the heat recovery unit has heating needs but no hot water needs, then the hot water heat exchanger and the air conditioning water heat exchanger are connected to the refrigerant circulation loop as evaporators in turn. If the heat recovery unit has no heating demand but has a hot water demand, then the air conditioning water heat exchanger and the hot water heat exchanger are connected to the refrigerant circulation loop as evaporators in turn. The hot water heat exchanger and the air conditioning water heat exchanger are alternately connected as evaporators in the refrigerant circulation loop, including: If the actual water temperature T1 of the hot water heat exchanger is greater than the set lower limit temperature A1 for hot water production, or the actual water temperature T2 of the air conditioning water heat exchanger is greater than the set lower limit temperature A2 for heating, then the hot water heat exchanger is first switched to an evaporator. When the actual water temperature T1 is less than or equal to the set lower limit temperature A1 for hot water production, the air conditioning water heat exchanger is then switched to an evaporator. If the actual water temperature T1 of the hot water heat exchanger is less than or equal to the set lower limit temperature A1 for hot water and the actual water temperature T2 of the air conditioning water heat exchanger is less than or equal to the set lower limit temperature A2 for heating, then the hot water heat exchanger is first switched to an evaporator. When the actual water temperature T1 is less than or equal to the set antifreeze temperature H1 for hot water, the air conditioning water heat exchanger is then switched to an evaporator. Among them, A1 > H1, A2 > H2.

2. The defrosting control method according to claim 1, characterized in that, The hot water heat exchanger and the air conditioning water heat exchanger are successively connected as evaporators into the refrigerant circulation loop, including: If the actual water temperature T1 of the hot water heat exchanger is greater than the set hot water antifreeze temperature H1, the hot water heat exchanger is first switched to an evaporator. When the actual water temperature T1 of the hot water heat exchanger is less than or equal to the set hot water antifreeze temperature H1, the air conditioning water heat exchanger is then switched to an evaporator.

3. The defrosting control method according to claim 1, characterized in that, The process of sequentially connecting the air conditioning water heat exchanger and the hot water heat exchanger as evaporators into the refrigerant circulation loop includes: If the actual water temperature T2 of the air conditioning water heat exchanger is greater than the set air conditioning water antifreeze temperature H2, the air conditioning water heat exchanger is first switched to an evaporator. When the actual water temperature T2 is less than or equal to the set air conditioning water antifreeze temperature H2, the hot water heat exchanger is then switched to an evaporator.

4. The defrosting control method according to claim 1, characterized in that, The defrosting entry conditions include power-on defrosting entry conditions and normal defrosting entry conditions; The defrosting control method includes: Monitor the operating status of the heat recovery unit; When the compressor unit of the heat recovery unit is not working and a start command is received, it is determined whether the operating parameters of the heat recovery unit meet the start-up defrosting conditions. If so, the refrigerant circulation loop is controlled to enter the refrigeration cycle. When the compressor unit of the heat recovery unit is in operation, it is determined whether the operating parameters of the heat recovery unit meet the conditions for entering the conventional defrosting cycle. If so, the refrigerant circulation loop is controlled to enter the refrigeration cycle.

5. The defrosting control method according to claim 4, characterized in that, The conditions for starting up and defrosting are that the continuous static time of the compressor unit is greater than or equal to the set standby time N, and the outdoor ambient temperature is less than or equal to the set lower limit temperature M.

6. The defrosting control method according to claim 1, characterized in that, The defrosting control method includes: forcibly discontinuing defrosting when the heat recovery unit reaches the antifreeze withdrawal condition; The antifreeze withdrawal condition is that the actual water temperature T1 of the hot water heat exchanger is less than or equal to the set hot water antifreeze temperature H1 and the actual water temperature T2 of the air conditioning water heat exchanger is less than or equal to the set air conditioning water antifreeze temperature H2.

7. The defrosting control method according to claim 6, characterized in that, The defrosting control method further includes: discontinuing defrosting when the heat recovery unit reaches the conventional defrosting exit conditions; The conventional defrosting exit conditions include at least one of the following: defrosting time exit condition, defrosting temperature exit condition, and exhaust pressure exit condition.

8. The defrosting control method according to any one of claims 1 to 7, characterized in that, The hot water heat exchanger is a shell-and-tube heat exchanger or a coaxial heat exchanger, and the air conditioning water heat exchanger is a plate heat exchanger; wherein, H2 > H1.

9. Heat recovery unit, including: A compressor unit and a heat exchanger assembly, wherein the heat exchanger assembly includes an air conditioning water heat exchanger, a hot water heat exchanger, and an outdoor heat exchanger, wherein the compressor unit can be connected to any two heat exchangers in the heat exchanger assembly to form a refrigerant circulation loop; characterized in that the heat recovery unit adopts the defrosting control method according to any one of claims 1 to 8.

10. The heat recovery unit according to claim 9, characterized in that, The heat recovery unit also includes a liquid receiver, wherein the exhaust side of the compressor unit can be switched to connect to the first end of any heat exchanger in the heat exchanger assembly, and the second end of each heat exchanger is connected to the inlet pipe of the liquid receiver via a valve. The second end of the air conditioner water heat exchanger is connected to the second end of the outdoor heat exchanger through a throttling pipe. The throttling pipe is connected in series with a first throttling valve and a second throttling valve. The outlet pipe of the liquid receiver is connected between the first throttling valve and the second throttling valve. The second end of the hot water heat exchanger is connected between the first throttling valve and the second throttling valve via a defrosting branch. The defrosting branch is equipped with a throttling element and a control valve for switching on and off states.

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