Simulation calculation method for refrigerating working conditions of double-cold-source fresh air machine

Abstract

The invention relates to the technical field of fresh air machine refrigeration simulation, and discloses a double-cold-source fresh air machine refrigeration working condition simulation calculation method which comprises the following steps: initialization of input parameters: obtaining initialization parameters of a double-cold-source fresh air machine, parameters of a cooling water system, parameters of air to be processed and air supply design parameters; initial data preparation, pre-cooling coil simulation calculation and fluorine system simulation calculation of simulation calculation are completed; according to the method, actual operation influence factors including various dynamic variables such as cooling water parameters, air parameters and filter screen states are comprehensively considered, so that a simulation result better fits an actual operation scene; the calculation is simplified, the precision is ensured, and through reasonable process simplification and iterative calculation, the accuracy of the simulation result is ensured while the calculation complexity is reduced, and the simulation result is highly consistent with the actual equipment operation condition.

Description

Technical Field

[0001] This invention relates to the field of fresh air system refrigeration simulation technology, specifically a method for simulating and calculating the refrigeration conditions of a dual-cold-source fresh air system. Background Technology

[0002] With the improvement of people's living standards and the increasing demand for comfortable living environments, the five-constant system (constant temperature, constant humidity, constant oxygen, constant cleanliness, and constant quietness), with independent temperature and humidity control as its core and radiant terminals as the main air conditioning terminal equipment, has been widely used. Dual-source fresh air systems, as the core equipment of the five-constant system, are responsible for outdoor air filtration and temperature and humidity regulation, directly ensuring constant humidity and oxygen requirements, and providing technical support for the stable operation and constant temperature of the radiant terminals.

[0003] Dual-source fresh air systems, in cooling and dehumidification mode, deliver outdoor air into the room after filtration, pre-cooling by pre-cooling coils, deep cooling and dehumidification by direct expansion coils, and reheating by reheat coils. Their operating characteristics are highly compatible with five-constant systems, making them the preferred choice for fresh air handling equipment. However, while dual-source fresh air systems are designed and manufactured according to standard operating conditions, actual operating conditions are complex and varied. Experimental testing cannot cover all dynamic conditions and is time-consuming and labor-intensive. Therefore, we propose a simulation calculation method for the cooling operation of dual-source fresh air systems. Summary of the Invention

[0004] The purpose of this invention is to provide a simulation calculation method for the refrigeration operation of a dual-cold-source fresh air system, so as to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a method for simulating the refrigeration conditions of a dual-cold-source fresh air system, comprising the following steps:

[0006] S1. Input parameter initialization: Obtain the initialization parameters of the dual-cold source fresh air unit, cooling water system parameters, air parameters to be processed, and air supply design parameters to complete the initial data preparation for simulation calculation.

[0007] S2. Precooling coil simulation calculation: Based on the input parameter initialization data, the cooling and condensation process of the mixed air in the precooling coil is simulated according to the preset simplification rules, and the temperature of the precooled air, the dew point temperature and the return water temperature of the precooling coil are output.

[0008] S3. Fluorine system simulation calculation: Using the output results of the precooling coil simulation calculation as initial conditions, the operation process of the direct expansion coil, reheat coil and water-side heat exchanger is simulated in a coordinated manner, and the operating parameters and energy consumption data of the dual-cold source fresh air unit are output.

[0009] Optionally, the initialization parameters of the dual-cold-source fresh air unit in S1 include: sensible heat calculation parameters of the precooling coil, latent heat calculation parameters of the precooling coil, the ratio of compressor full-load power to rated air volume, the ratio of compressor rated water volume to rated air volume, the proportion of precooling coil to fan cooling water, the percentage of compressor frequency upper and lower limits, the percentage of reheat coil reheat to compressor total heat exhaust, the linear function parameters of condensing temperature and average water-fluorine plate heat exchanger temperature, the upper limit of compressor condensing temperature, and the ratio of actual system efficiency to theoretical COP of the fluorine system.

[0010] Optionally, the acquisition of the air parameters to be processed in S1 includes:

[0011] The enthalpy of the mixed air is calculated using the fresh air temperature, fresh air dew point temperature, return air temperature, return air dew point temperature, and the proportion of return air to the mixed air.

[0012] The mixed air volume is calculated by adjusting the standard operating air volume according to the actual operating level and the filter clogging, and then combining it with the air density to obtain the total air volume (mass) handled by the fan.

[0013] Optionally, the preset simplification rules in S2 include:

[0014] The process of air mixing in the precooling coil can be simplified into a cooling stage and a condensation stage that occur sequentially. In the cooling stage, only the temperature drops and no condensate is produced. In the condensation stage, the temperature drops and condensate is produced.

[0015] The sensible heat change of the mixed air involves the cooling stage and the condensation stage, while the latent heat change only occurs in the condensation stage. The two are treated independently.

[0016] If a condensation stage is involved, the treated mixed air is saturated air with the same temperature as the dew point temperature and a relative humidity of 100%.

[0017] The heat exchange capacity of the precooling coil is proportional to the 0.8th power of the cooling water flow rate. Latent heat and sensible heat are calculated separately for each independent system.

[0018] The temperature of the treated mixed air should not be lower than the return water temperature of the cooling water.

[0019] Optionally, the specific process of the precooling coil simulation calculation in S2 includes:

[0020] To determine whether the cooling phase can be fully completed in the pre-cooling coil, the following criteria are used: assuming that the air mixture reaches saturation after cooling is completed, calculate the heat released by the air mixture and the return water temperature after the cooling water absorbs the heat. If the return water temperature exceeds the air mixture temperature, then the cooling cannot be completed.

[0021] If cooling cannot be completed, and the temperature of the mixed air after treatment is higher than the dew point temperature, the data converges through iterative calculation.

[0022] If cooling can be completed, assuming the mixed air temperature and dew point temperature after treatment, calculate the latent heat load, sensible heat load, enthalpy of the pre-cooled air, and coil return water temperature, and iterate until the data converges.

[0023] Optionally, the preset limitations and assumptions for the simulation calculation of the fluorine system in S3 include:

[0024] The compressor frequency can be variable from 30% to 90%, and within this range, the actual output of the compressor is linearly related to the frequency.

[0025] The maximum condensing temperature is 50°C; the compressor will automatically reduce its frequency if this limit is exceeded.

[0026] The air before reheating after being treated by the direct expansion coil is saturated air, and its temperature is equal to the dew point temperature.

[0027] Optionally, the simulation calculation of the direct expansion coil in S3 includes the following process:

[0028] The compressor frequency is initialized based on the standard operating conditions, and the compressor frequency is limited to the range of 30%-90% in subsequent calculations;

[0029] The current compressor load is calculated based on the compressor frequency and full-load power, and the enthalpy of the air before reheating is obtained by combining the enthalpy of the pre-cooled air.

[0030] Based on the assumption that the air before reheating is saturated, the dew point of the air before reheating is calculated according to the enthalpy value.

[0031] The evaporation temperature of the fluorine system is calculated based on the dew point temperature before reheat.

[0032] Optionally, the calculation process for the total heat dissipation of the compressor and related parameters in S3 includes:

[0033] Calculate the compressor's electrical power under the current operating conditions based on the compressor's COP, full-load power, and compressor frequency. The COP value is used in the initial calculation.

[0034] Calculate the total heat dissipation of the compressor, which is the sum of the compressor load and the compressor electrical power;

[0035] The required reheat heat is calculated based on the target supply air temperature and the temperature before reheating. The reheat heat is not less than 0 and meets the requirement that the heat exchange heat of the air-side heat exchanger accounts for the total heat exhaust.

[0036] The heat dissipation of the water-side heat exchanger is equal to the total heat dissipation minus the reheat. The average cooling water temperature, return water temperature, and refrigerant system condensation temperature are calculated based on the heat exchanger heat transfer. The COP is then updated in conjunction with the evaporation temperature.

[0037] If the condensing temperature exceeds the limit, the compressor frequency is reduced and the reheat capacity is adjusted to prioritize ensuring that the supply air dew point reaches the target value. The calculation is repeated iteratively until the data converges to an acceptable accuracy range.

[0038] Compared with existing technologies, this invention provides a simulation calculation method for the refrigeration operation of a dual-cold-source fresh air system, which has the following beneficial effects:

[0039] 1. The simulation calculation method for the cooling operation of the dual-cold-source fresh air system comprehensively considers various dynamic variables such as cooling water parameters, air parameters, and filter status, making the simulation results more consistent with the actual operating scenario. It simplifies the calculation while ensuring accuracy. Through reasonable process simplification and iterative calculation, it reduces the computational complexity while ensuring the accuracy of the simulation results, which are highly consistent with the actual equipment operation.

[0040] 2. The simulation calculation method for the cooling operation of the dual-cold-source fresh air system can provide data support for the design and development of dual-cold-source fresh air systems. It can also be integrated into the five constant system control system to realize dynamic operation adjustment based on energy consumption indicators. This solves the problems of limited coverage and low efficiency of traditional experimental testing, and has broad practicality and promotion value. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the dual-cold-source fresh air system of the present invention; Figure 2 This is a flowchart illustrating the simulation calculation of the precooling coil of the dual-cold-source fresh air unit of the present invention.

[0042] Figure 1 This is a flowchart illustrating the simulation calculation of the precooling coil of the dual-cold-source fresh air unit of the present invention. Detailed Implementation

[0043] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] like Figures 1-2 As shown, the present invention provides a technical solution: a method for simulating and calculating the refrigeration conditions of a dual-cold-source fresh air system, comprising the following steps:

[0045] S1. Input parameter initialization: Obtain the initialization parameters of the dual-cold source fresh air unit, cooling water system parameters, air parameters to be processed, and air supply design parameters to complete the initial data preparation for simulation calculation.

[0046] S2. Precooling coil simulation calculation: Based on the input parameter initialization data, the cooling and condensation process of the mixed air in the precooling coil is simulated according to the preset simplification rules, and the temperature of the precooled air, the dew point temperature and the return water temperature of the precooling coil are output.

[0047] S3, the fluorine system simulation calculation, takes the output results of the precooling coil simulation calculation as the initial condition, and performs a collaborative simulation of the operation process of the direct expansion coil, reheat coil and water-side heat exchanger, outputting the operating parameters and energy consumption data of the dual-source fresh air unit.

[0048] The initialization parameters for the dual-source fresh air unit include: sensible heat calculation parameters of the precooling coil, latent heat calculation parameters of the precooling coil, the ratio of compressor full-load power to rated air volume, the ratio of compressor rated water volume to rated air volume, the proportion of precooling coil to fan cooling water, the upper and lower limits of compressor frequency, the upper and lower limits of reheat coil reheat heat to compressor total heat exhaust, the linear function parameters of condensing temperature and average temperature of water-fluorine plate heat exchanger, the upper limit of compressor condensing temperature, and the ratio of actual system efficiency to theoretical COP of the fluorine system. The parameters for obtaining the air to be treated include: the mixed air enthalpy value is calculated using fresh air temperature, fresh air dew point temperature, return air temperature, return air dew point temperature, and the proportion of return air to mixed air; the mixed air volume is calculated by correcting the standard operating condition air volume for actual operating gear and filter clogging, combined with air density, to obtain the total air volume handled by the fan.

[0049] In addition, the preset simplification rules include:

[0050] The process of air mixing in the precooling coil can be simplified into a cooling stage and a condensation stage that occur sequentially. In the cooling stage, only the temperature drops and no condensate is produced. In the condensation stage, the temperature drops and condensate is produced.

[0051] The sensible heat change of the mixed air involves the cooling stage and the condensation stage, while the latent heat change only occurs in the condensation stage. The two are treated independently.

[0052] If a condensation stage is involved, the treated mixed air is saturated air with the same temperature as the dew point temperature and a relative humidity of 100%. The heat exchange capacity of the precooling coil is proportional to the 0.8th power of the cooling water flow rate. Latent heat and sensible heat are calculated separately for each independent system. The temperature of the treated mixed air is not lower than the return water temperature of the cooling water.

[0053] The specific process of precooling coil simulation calculation includes:

[0054] To determine whether the cooling phase can be fully completed in the pre-cooling coil, the following criteria are used: assuming that the air mixture reaches saturation after cooling is completed, calculate the heat released by the air mixture and the return water temperature after the cooling water absorbs the heat. If the return water temperature exceeds the air mixture temperature, then the cooling cannot be completed.

[0055] If cooling cannot be completed, and the temperature of the mixed air after treatment is higher than the dew point temperature, the data converges through iterative calculation.

[0056] If cooling can be completed, assuming the mixed air temperature and dew point temperature after treatment, calculate the latent heat load, sensible heat load, enthalpy of the pre-cooled air, and coil return water temperature, and iterate until the data converges.

[0057] The preset limitations and assumptions for fluorine system simulation calculations include:

[0058] The compressor frequency can be variable from 30% to 90%, and within this range, the actual output of the compressor is linearly related to the frequency.

[0059] The maximum condensing temperature is 50°C; the compressor will automatically reduce its frequency if this limit is exceeded.

[0060] The air before reheating after being treated by the direct expansion coil is saturated air, and its temperature is equal to the dew point temperature.

[0061] The simulation calculation of direct expansion coil includes the following process:

[0062] The compressor frequency is initialized based on the standard operating conditions, and the compressor frequency is limited to the range of 30%-90% in subsequent calculations;

[0063] The current compressor load is calculated based on the compressor frequency and full-load power, and the enthalpy of the air before reheating is obtained by combining the enthalpy of the pre-cooled air.

[0064] Based on the assumption that the air before reheating is saturated, the dew point of the air before reheating is calculated according to the enthalpy value.

[0065] The evaporation temperature of the fluorine system is calculated based on the dew point temperature before reheat.

[0066] The calculation process for the compressor's total heat dissipation and related parameters includes:

[0067] Calculate the compressor's electrical power under the current operating conditions based on the compressor's COP, full-load power, and compressor frequency. The COP value is used in the initial calculation.

[0068] Calculate the total heat dissipation of the compressor, which is the sum of the compressor load and the compressor electrical power;

[0069] The required reheat heat is calculated based on the target supply air temperature and the temperature before reheating. The reheat heat is not less than 0 and meets the requirement that the heat exchange heat of the air-side heat exchanger accounts for the total heat exhaust.

[0070] The heat dissipation of the water-side heat exchanger is equal to the total heat dissipation minus the reheat. The average cooling water temperature, return water temperature, and refrigerant system condensation temperature are calculated based on the heat exchanger heat transfer. The COP is then updated in conjunction with the evaporation temperature.

[0071] If the condensing temperature exceeds the limit, the compressor frequency is reduced and the reheat capacity is adjusted to prioritize ensuring that the supply air dew point reaches the target value. The calculation is repeated iteratively until the data converges to an acceptable accuracy range.

[0072] As one application of this embodiment: This embodiment comprehensively considers various dynamic variables such as actual operating factors, including cooling water parameters, air parameters, and filter status, so the simulation results are more in line with the actual operating scenario; it simplifies calculations and ensures accuracy. Through reasonable process simplification and iterative calculation, it reduces computational complexity while ensuring the accuracy of simulation results, which are highly consistent with the actual equipment operation.

[0073] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A simulation calculation method for the refrigeration operation of a dual-cold-source fresh air system, characterized in that, Includes the following steps: S1. Input parameter initialization: Obtain the initialization parameters of the dual-cold source fresh air unit, cooling water system parameters, air parameters to be processed, and air supply design parameters to complete the initial data preparation for simulation calculation. S2. Precooling coil simulation calculation: Based on the input parameter initialization data, the cooling and condensation process of the mixed air in the precooling coil is simulated according to the preset simplification rules, and the temperature of the precooled air, the dew point temperature and the return water temperature of the precooling coil are output. S3. Fluorine system simulation calculation: Using the output results of the precooling coil simulation calculation as initial conditions, the operation process of the direct expansion coil, reheat coil and water-side heat exchanger is simulated in a coordinated manner, and the operating parameters and energy consumption data of the dual-cold source fresh air unit are output.

2. The method for simulating the refrigeration operation of a dual-cold-source fresh air system according to claim 1, characterized in that, The initialization parameters of the dual-cold-source fresh air unit in S1 include: sensible heat calculation parameters of the precooling coil, latent heat calculation parameters of the precooling coil, the ratio of compressor full-load power to rated air volume, the ratio of compressor rated water volume to rated air volume, the proportion of precooling coil to fan cooling water, the percentage of compressor frequency upper and lower limits, the percentage of reheat coil reheat to compressor total heat exhaust, the linear function parameters of condensing temperature and average water-fluorine plate heat exchanger temperature, the upper limit of compressor condensing temperature, and the ratio of actual system efficiency to theoretical COP of the fluorine system.

3. The method for simulating the refrigeration operation of a dual-cold-source fresh air system according to claim 1, characterized in that, The acquisition of the air parameters to be processed in S1 includes: The enthalpy of the mixed air is calculated using the fresh air temperature, fresh air dew point temperature, return air temperature, return air dew point temperature, and the proportion of return air to the mixed air. The mixed air volume is calculated by adjusting the standard operating air volume according to the actual operating level and the filter clogging, and then combining the air density to obtain the total air volume handled by the fan.

4. The method for simulating the refrigeration operation of a dual-cold-source fresh air system according to claim 1, characterized in that, The preset simplification rules in S2 include: The process of air mixing in the precooling coil can be simplified into a cooling stage and a condensation stage that occur sequentially. In the cooling stage, only the temperature drops and no condensate is produced. In the condensation stage, the temperature drops and condensate is produced. The sensible heat change of the mixed air involves the cooling stage and the condensation stage, while the latent heat change only occurs in the condensation stage. The two are treated independently. If a condensation stage is involved, the treated mixed air is saturated air with the same temperature as the dew point temperature and a relative humidity of 100%. The heat exchange capacity of the precooling coil is proportional to the 0.8th power of the cooling water flow rate. Latent heat and sensible heat are calculated separately for each independent system. The temperature of the treated mixed air should not be lower than the return water temperature of the cooling water.

5. The method for simulating the refrigeration operation of a dual-cold-source fresh air system according to claim 1, characterized in that, The specific process of the precooling coil simulation calculation in S2 includes: To determine whether the cooling phase can be fully completed in the pre-cooling coil, the following criteria are used: assuming that the air mixture reaches saturation after cooling is completed, calculate the heat released by the air mixture and the return water temperature after the cooling water absorbs the heat. If the return water temperature exceeds the air mixture temperature, then the cooling cannot be completed. If cooling cannot be completed, and the temperature of the mixed air after treatment is higher than the dew point temperature, the data converges through iterative calculation. If cooling can be completed, assuming the mixed air temperature and dew point temperature after treatment, calculate the latent heat load, sensible heat load, enthalpy of the pre-cooled air, and coil return water temperature, and iterate until the data converges.

6. The method for simulating the refrigeration operation of a dual-cold-source fresh air system according to claim 1, characterized in that, The preset limitations and assumptions for the simulation calculation of the fluorine system in S3 include: The compressor frequency can be variable from 30% to 90%, and within this range, the actual output of the compressor is linearly related to the frequency. The maximum condensing temperature is 50°C; the compressor will automatically reduce its frequency if this limit is exceeded. The air before reheating after being treated by the direct expansion coil is saturated air, and its temperature is equal to the dew point temperature.

7. The method for simulating the refrigeration operation of a dual-cold-source fresh air system according to claim 1, characterized in that, The simulation calculation of the straight expansion coil in S3 includes the following process: The compressor frequency is initialized based on the standard operating conditions, and the compressor frequency is limited to the range of 30%-90% in subsequent calculations; The current compressor load is calculated based on the compressor frequency and full-load power, and the enthalpy of the air before reheating is obtained by combining the enthalpy of the pre-cooled air. Based on the assumption that the air before reheating is saturated, the dew point of the air before reheating is calculated according to the enthalpy value. The evaporation temperature of the fluorine system is calculated based on the dew point temperature before reheat.

8. The method for simulating the refrigeration operation of a dual-cold-source fresh air system according to claim 1, characterized in that, The calculation process for the total heat dissipation of the compressor and related parameters in S3 includes: Calculate the compressor's electrical power under the current operating conditions based on the compressor's COP, full-load power, and compressor frequency. The COP value is used in the initial calculation. Calculate the total heat dissipation of the compressor, which is the sum of the compressor load and the compressor electrical power; The required reheat heat is calculated based on the target supply air temperature and the temperature before reheating. The reheat heat is not less than 0 and meets the requirement that the heat exchange heat of the air-side heat exchanger accounts for the total heat exhaust. The heat dissipation of the water-side heat exchanger is equal to the total heat dissipation minus the reheat. The average cooling water temperature, return water temperature, and refrigerant system condensation temperature are calculated based on the heat exchanger heat transfer. The COP is then updated in conjunction with the evaporation temperature. If the condensing temperature exceeds the limit, the compressor frequency is reduced and the reheat capacity is adjusted to prioritize ensuring that the supply air dew point reaches the target value. The calculation is repeated iteratively until the data converges to an acceptable accuracy range.

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