Abstract
The invention discloses a method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds, belonging to the technical field of air conditioner cooling capacity testing. This method involves a sampling device for measuring dry and wet bulb temperatures at the return air inlet under different wind speeds and includes the following steps:
S1. Measure the air supply parameters, return air parameters, and circulating air volume of the air conditioner using the “enthalpy method.”
S2. Calculate the uncertainty components using the “sensitivity coefficient” and assess the degree of influence of each component on the experimental results from step S1.
S3. Conduct testing simulations on the uncertainty component with the greatest impact.
S4. Use the control variable method to calculate the degree of influence of the influencing factors on the cooling capacity of the tested air conditioner.
S5. Select a reference wind speed and determine the formula to calculate the deviation of the rated cooling capacity of the air conditioner at different wind speeds.
The invention proposes a new calculation method that enables the calculation of the deviation of the rated cooling capacity of air conditioners at different wind speeds, filling a gap in this field.
1.A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds, characterized in that the method includes the following steps:
S1. Use the “enthalpy method” to test the cooling and heating capacity of the air conditioner, measure the air supply parameters, return air parameters, and circulating air volume, and obtain results;
S2. Use the “sensitivity coefficient” to calculate the uncertainty components and assess the degree of influence of each component on the experimental results from step S1;
S3. Based on the uncertainty components obtained in step S2, select the one with the greatest impact, and use the rated cooling condition T1 specified in national standards as the test condition for simulation;
S4. Analyze the data of the uncertainty component with the greatest influence from step S3, and use the control variable method to calculate the impact of this uncertainty component under different wind speed conditions, and calculate its effect on the cooling capacity of the tested air conditioner;
S5. Select a reference wind speed based on relevant documents, and use the data from steps S1 to S4 to determine the formula for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds.
In step S5, analyze the data and conclusions derived from steps S1 to S4 to establish the relationship between the variation of the cooling capacity of the tested air conditioner and its factors, and derive the formula for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds. According to relevant documents, GB/T 7725-2004 “Room Air Conditioners” section C.1.3 requires that “the airflow velocity at the wet bulb thermometer should not be less than 5 m/s”;When the wind speed is below 5 m/s, the formula for calculating the deviation of the rated cooling capacity is:
[ y = 3.5907x^4 – 52.606x^3 + 284.34x^2 – 681.11x + 629.18; ]
When the wind speed is above 5 m/s, the formula for calculating the deviation of the rated cooling capacity is:
[ y = 0.0004x^4 – 0.0159x^3 – 0.0012x^2 + 4.6443x – 20.73. ]
2.A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 1, characterized in that: in step S1, the air supply parameters, return air parameters, and circulating air volume of the air conditioner are measured using the following formulas, and the ability of the air conditioner is determined using the product of the measured airflow and the difference in enthalpy of the supply and return air;
Where ( \phi tc ) is the cooling capacity of the air conditioner, in watts (W); ( qmi ) is the indoor airflow of the air conditioner, in m³/s; ( ha1 ) is the enthalpy of the return air at the indoor side, dry air, in J/kg; ( ha2 ) is the enthalpy of the supply air at the indoor side, dry air, in J/kg; ( V’n ) is the specific volume of moist air at the measuring point, in m³/kg; ( Wn ) is the humidity of the air at the measuring point, in kg/kg (dry air); ( W1 ) is the moisture content of the return air at the indoor side, in kg/kg (dry air); ( dsw1 ) is the saturated moisture content of the return air at the indoor side, in kg/kg (dry air); ( W2 ) is the moisture content of the supply air at the indoor side, in kg/kg (dry air); ( dsw2 ) is the saturated moisture content of the supply air at the indoor side, in kg/kg (dry air); ( t1 ) is the dry bulb temperature of the return air at the indoor side, in °C; ( tw1 ) is the wet bulb temperature of the return air at the indoor side, in °C; ( t2 ) is the dry bulb temperature of the supply air at the indoor side, in °C; ( tw2 ) is the wet bulb temperature of the supply air at the indoor side, in °C.
3.A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 1, characterized in that: in step S2, the factors introducing the uncertainty components include the dry bulb temperature ( t1 ) of the return air at the indoor side; the wet bulb temperature ( tw1 ) of the return air at the indoor side; the dry bulb temperature ( t2 ) of the supply air at the indoor side; the wet bulb temperature ( tw2 ) of the supply air at the indoor side; the dry bulb temperature ( t3 ) before the nozzle; atmospheric pressure ( pb ); static pressure ( p2 ) before the nozzle; pressure difference ( \Delta p ) before and after the nozzle; and nozzle diameter ( D ).
4.A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 3, characterized in that: the sensitivity coefficients ( ci ) of the factors introducing the uncertainty components are calculated, where ( i ) represents each factor, and the calculation formula is as follows:
The sensitivity coefficients are calculated through computations.
- A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 4, characterized in that: based on the sensitivity coefficients ( ci ) and the standard uncertainties ( ui ) of each factor, the factors that play an absolute dominant role among the nine influencing factors are determined to be the wet bulb temperatures ( tw1 ) and ( tw2 ).
- A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 1, characterized in that: in step S3, during the testing simulation process, a standard window air conditioner is selected, and the “bs value” of the indoor wet bulb temperature sensor is adjusted for correction using the measurement error of the wet bulb temperature sensor to simulate the situation where environmental humidity deviates due to inaccurate wet bulb temperature measurement.
- A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 6, characterized in that: the wet bulb temperature sensor is wrapped with well-matched gauze, with the excess gauze connected to a water container. The moisture evaporation on the gauze takes away heat from the wet bulb, causing its temperature to be lower than that of the dry bulb. The efficiency of moisture evaporation on the wet bulb gauze directly affects the wet bulb temperature, and it has a functional relationship with wind speed and the moisture content in the surrounding air.
- A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 1, characterized in that: in step S4, the control variable method is used, and the calculation formula is as follows:
Where ( U ) is the environmental relative humidity in %RH; ( t ) is the dry bulb temperature in °C; ( tw ) is the wet bulb temperature in °C; ( ew ) is the saturated vapor pressure at the wet bulb temperature in Pa; ( es ) is the saturated vapor pressure at the dry bulb temperature in Pa; ( A ) is the dry-wet bulb coefficient; ( P ) is the atmospheric pressure in Pa; ( v ) is the wind speed in m/s;
Under conditions where other factors remain unchanged and only the wind speed is varied, the theoretical values of relative humidity at different wind speeds are calculated.
9.A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds according to claim 1, characterized in that: in step S4, the different wind speeds refer to the different wind speeds within the dry and wet bulb temperature sampler at the return air inlet.
A method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds.
Technical Field
[0001] The present invention relates to the technical field of air conditioner cooling capacity testing, specifically to a method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds.
Background Technology
[0002] The cooling capacity is an important indicator of an air conditioner and serves as a reference standard for measuring its functionality; it is essentially the only significant “size” metric aside from appearance. The cooling capacity refers to the total amount of heat removed from a closed space, room, or area during the cooling operation of the air conditioner per unit time, with the legal measurement unit being W (watts).
[0003] After each air conditioner is manufactured, the manufacturer sets the corresponding nameplate to mark the cooling capacity according to national standards. However, in actual use, with changes in the environment and the operating conditions of the air conditioner itself, the actual cooling capacity does not equal the capacity marked on the nameplate, leading to significant deviations.
[0004] Currently, there is no method available that can calculate the deviation of the rated cooling capacity of an air conditioner at different wind speeds, and there are no related calculation methods for the cooling capacity deviation at different wind speeds. Therefore, the present invention proposes a method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds.
Invention Content
[0005] The purpose of the present invention is to provide a method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds to solve the problems mentioned in the background technology.
[0006] To address the above technical issues, the present invention provides the following technical solution: a method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds, which includes the following steps:
[0007] S1. Use the “enthalpy method” to test the cooling and heating capacity of the air conditioner, measure the air supply parameters, return air parameters, and circulating air volume, and obtain results;
[0008] S2. Use the “sensitivity coefficient” to calculate the uncertainty components and assess the degree of influence of each component on the experimental results from step S1;
[0009] S3. Based on the uncertainty components obtained in step S2, select the one with the greatest impact, and use the rated cooling condition T1 specified in national standards as the test condition for simulation with a standard window air conditioner as the experimental object;
[0010] S4. Analyze the data of the uncertainty component with the greatest influence from step S3, and use the control variable method to calculate the impact of this uncertainty component under different wind speed conditions, and calculate its effect on the cooling capacity of the tested air conditioner;
[0011] S5. Based on relevant documents, select a reference wind speed, and use the data from steps S1 to S4 to determine the formula for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds.
[0012] According to the above technical solution, in step S1, the air supply parameters, return air parameters, and circulating air volume of the air conditioner are measured using the following formulas, and the ability of the air conditioner is determined using the product of the measured airflow and the difference in enthalpy of the supply and return air;
[0018] Where ( \phi tc ) is the cooling capacity of the air conditioner, in watts (W); ( qmi ) is the indoor airflow of the air conditioner, in m³/s; ( ha1 ) is the enthalpy of the return air at the indoor side (dry air), in J/kg; ( ha2 ) is the enthalpy of the supply air at the indoor side (dry air), in J/kg; ( V’n ) is the specific volume of moist air at the measuring point, in m³/kg; ( Wn ) is the humidity of the air at the measuring point, in kg/kg (dry air); ( W1 ) is the moisture content of the return air at the indoor side, in kg/kg (dry air); ( dsw1 ) is the saturated moisture content of the return air at the indoor side, in kg/kg (dry air); ( W2 ) is the moisture content of the supply air at the indoor side, in kg/kg (dry air); ( dsw2 ) is the saturated moisture content of the supply air at the indoor side, in kg/kg (dry air); ( t1 ) is the dry bulb temperature of the return air at the indoor side, in °C; ( tw1 ) is the wet bulb temperature of the return air at the indoor side, in °C; ( t2 ) is the dry bulb temperature of the supply air at the indoor side, in °C; ( tw2 ) is the wet bulb temperature of the supply air at the indoor side, in °C.
[0019] According to the above technical solution, in step S2, the factors introducing the uncertainty components include the dry bulb temperature ( t1 ) of the return air at the indoor side; the wet bulb temperature ( tw1 ) of the return air at the indoor side; the dry bulb temperature ( t2 ) of the supply air at the indoor side; the wet bulb temperature ( tw2 ) of the supply air at the indoor side; the dry bulb temperature ( t3 ) before the nozzle; atmospheric pressure ( pb ); static pressure ( p2 ) before the nozzle; pressure difference ( \Delta p ) before and after the nozzle; and nozzle diameter ( D ).
[0020] According to the above technical solution, the sensitivity coefficients ( ci ) of each factor introducing the uncertainty components are calculated, where ( i ) represents each factor, and the calculation formula is as follows:
[0030] Based on the sensitivity coefficients \( ci \) and the standard uncertainties \( ui \) of each factor, the factors that play an absolute dominant role among the nine influencing factors are determined to be the wet bulb temperatures \( tw1 \) and \( tw2 \).
[0031] According to the above technical solution, in step S3, the rated cooling condition T1 specified in national standards is defined as follows: indoor dry bulb temperature: 27.00°C; indoor wet bulb temperature: 19.00°C; outdoor dry bulb temperature: 35.00°C; outdoor wet bulb temperature: 24.00°C.
[0032] According to the above technical solution, in step S3, during the testing simulation process, a standard window air conditioner is selected, and the “bs value” of the indoor wet bulb temperature sensor is adjusted for correction using the measurement error of the wet bulb temperature sensor to simulate the situation where environmental humidity deviates due to inaccurate wet bulb temperature measurement.
[0033] According to the above technical solution, the wet bulb temperature sensor is wrapped with well-matched gauze, with the excess gauze connected to a water container. The moisture evaporation on the gauze takes away heat from the wet bulb, causing its temperature to be lower than that of the dry bulb. The efficiency of moisture evaporation on the wet bulb gauze directly affects the wet bulb temperature, and it has a functional relationship with wind speed and the moisture content in the surrounding air.
[0034] According to the above technical solution, in step S4, the control variable method is used, where the different wind speeds refer to the varying wind speeds within the dry and wet bulb temperature sampler at the return air inlet. The calculation formula is as follows:
[0039] Where \( U \) is the environmental relative humidity in %RH; \( t \) is the dry bulb temperature in °C; \( tw \) is the wet bulb temperature in °C; \( ew \) is the saturated vapor pressure at the wet bulb temperature in Pa; \( es \) is the saturated vapor pressure at the dry bulb temperature in Pa; \( A \) is the dry-wet bulb coefficient; \( P \) is the atmospheric pressure in Pa; \( v \) is the wind speed in m/s;
[0040] Under conditions where other factors remain unchanged and only the wind speed is varied, the theoretical values of relative humidity at different wind speeds are calculated.
[0041] According to the above technical solution, in step S5, the relevant document is GB/T 7725-2004 “Room Air Conditioners,” section C.1.3, which requires that “the airflow velocity at the wet bulb thermometer should not be less than 5 m/s.”
[0042] According to the above technical solution, in step S5, the data and conclusions derived from steps S1 to S4 are analyzed to establish the relationship between the variation in the cooling capacity of the tested air conditioner and its factors, and to derive the formula for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds;
[0043] When the wind speed is below 5 m/s, the formula for calculating the deviation of the rated cooling capacity is:
\[ y = 3.5907x^4 – 52.606x^3 + 284.34x^2 – 681.11x + 629.18; \]
[0044] When the wind speed is above 5 m/s, the formula for calculating the deviation of the rated cooling capacity is:
\[ y = 0.0004x^4 – 0.0159x^3 – 0.0012x^2 + 4.6443x – 20.73. \]
[0045] Compared to existing technologies, the beneficial effects achieved by the present invention are:
[0046] The invention utilizes the air enthalpy method to measure the air supply parameters, return air parameters, and circulating air volume of the air conditioner. The capacity of the air conditioner is determined using the product of the measured airflow and the difference in enthalpy of the supply and return air. Then, in the evaluation of measurement uncertainty for room air conditioners using the air enthalpy method, the uncertainty components are calculated using the “sensitivity coefficient,” which can intuitively present the degree of influence of each component on the experimental results. The factors that play an absolute dominant role are selected for further analysis. The control variable method is used to discuss the accuracy analysis of these influencing factors under different wind speeds, leading to the derivation of formulas for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds, based on extensive data and accurate experiments.The invention proposes a new calculation method that enables the calculation of the deviation of the rated cooling capacity of an air conditioner at different wind speeds, filling a gap in this field.
Description of the Drawings
[0049] The drawings are intended to provide a further understanding of the present invention and constitute part of the specification. They are used to explain the embodiments of the present invention and do not limit the invention. In the drawings:
[0050] Figure 1 is a layout diagram of the testing device for the method of calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds;
[0051] Figure 2 is a graph showing the variation of relative humidity with wind speed for the method of calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds;
[0052] Figure 3 is a schematic diagram showing the deviation of the rated cooling capacity with changes in wind speed (wind speed < 5 m/s) for the method of calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds;
[0053] Figure 4 is a schematic diagram showing the deviation of the rated cooling capacity with changes in wind speed (wind speed > 5 m/s) for the method of calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds;
[0054] Figure 5 is a flowchart illustrating the steps of the method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds;
Specific Embodiment
[0055] The following provides a clear and complete description of the technical solution in the embodiment of the present invention in conjunction with the accompanying drawings. It is evident that the described embodiment is only one part of the embodiments of the present invention and not all embodiments. All other embodiments obtained by those skilled in the art without creative efforts based on the embodiments of the present invention fall within the protection scope of the present invention.
[0056] Please refer to Figures 1-4. The present invention provides the following technical solution: a method for calculating the deviation of the rated cooling capacity of an air conditioner at different wind speeds, which includes the following steps:
[0057] S1. Use the “enthalpy method” to test the cooling and heating capacity of the air conditioner, measure the air supply parameters, return air parameters, and circulating air volume, and obtain results;
[0058] S2. Use the “sensitivity coefficient” to calculate the uncertainty components and assess the degree of influence of each component on the experimental results from step S1;
[0059] S3. Based on the uncertainty components obtained in step S2, select the one with the greatest impact, and use the rated cooling condition T1 specified in national standards as the test condition for simulation with a standard window air conditioner as the experimental object;
[0060] S4. Based on the analysis data of the uncertainty component with the greatest influence from step S3, use the control variable method to calculate the impact of this uncertainty component under different wind speed conditions, and calculate its effect on the cooling capacity of the tested air conditioner;
[0061] S5. Based on relevant documents, select a reference wind speed, and use the data from steps S1 to S4 to determine the formula for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds.
[0062] As shown in Figure 1, this is the layout diagram of the testing device for step S1. The airflow measurement device is set up on the indoor side, with the outdoor unit connected to the indoor unit. The outlet of the indoor unit is connected to the airflow measurement device through a mixer, where the dry and wet bulb temperature samplers are set on both sides of the mixer, and the pressure gauge is placed above the outlet. After the air leaves the airflow measurement device, it directly enters the air handling unit, which processes the air to achieve the specified operating conditions. According to the “enthalpy method,” the following formulas are used to measure the air supply parameters, return air parameters, and circulating air volume of the air conditioner, and the capacity of the air conditioner is determined using the product of the measured airflow and the difference in enthalpy of the supply and return air.
[0068] Where \( \phi tc \) is the cooling capacity of the air conditioner, in watts (W); \( qmi \) is the indoor airflow of the air conditioner, in m³/s; \( ha1 \) is the enthalpy of the return air at the indoor side (dry air), in J/kg; \( ha2 \) is the enthalpy of the supply air at the indoor side (dry air), in J/kg; \( V’n \) is the specific volume of moist air at the measuring point, in m³/kg; \( Wn \) is the humidity of the air at the measuring point, in kg/kg (dry air); \( W1 \) is the moisture content of the return air at the indoor side, in kg/kg (dry air); \( dsw1 \) is the saturated moisture content of the return air at the indoor side, in kg/kg (dry air); \( W2 \) is the moisture content of the supply air at the indoor side, in kg/kg (dry air); \( dsw2 \) is the saturated moisture content of the supply air at the indoor side, in kg/kg (dry air); \( t1 \) is the dry bulb temperature of the return air at the indoor side, in °C; \( tw1 \) is the wet bulb temperature of the return air at the indoor side, in °C; \( t2 \) is the dry bulb temperature of the supply air at the indoor side, in °C; \( tw2 \) is the wet bulb temperature of the supply air at the indoor side, in °C.
[0069] In this embodiment, standard window air conditioners with cooling capacities of 2700W, 4470W, and 5122W are selected as experimental subjects. The test conditions adopt the rated cooling condition T1 specified in national standards (indoor dry bulb: 27.00°C; indoor wet bulb: 19.00°C; outdoor dry bulb: 35.00°C; outdoor wet bulb: 24.00°C). According to step S2, the data of the uncertainty components calculated using the “sensitivity coefficient” in the evaluation of measurement uncertainty for room air conditioners using the air enthalpy method are analyzed as follows:
[0070] 1) The uncertainty component introduced by the indoor return dry bulb temperature \( t1 \) is calculated to obtain the sensitivity coefficient.
[0075] According to the calibration certificate and relevant technical data, the standard uncertainty of the return wet bulb temperature is \( u(tw1) = 0.05 \, °C \).
[0076] 3) The uncertainty component introduced by the indoor supply dry bulb temperature \( t2 \) is calculated to obtain the sensitivity coefficient.
[0078] According to the calibration certificate and relevant technical data, the standard uncertainty of the supply dry bulb temperature is:
[0079] ( u(t2) = 0.03 , °C ), resulting in
[0080] 4) The uncertainty component introduced by the indoor supply wet bulb temperature ( tw2 ) is calculated to obtain the sensitivity coefficient.
[0082] According to the calibration certificate and relevant technical data, the standard uncertainty of the supply wet bulb temperature is:
[0083] ( u(tw2) = 0.05 , °C ), resulting in
[0084] 5) The uncertainty component introduced by the dry bulb temperature \( t3 \) before the nozzle is calculated to obtain the sensitivity coefficient.
[0085] According to the calibration certificate and relevant technical data, the standard uncertainty of the dry bulb temperature before the nozzle is:
[0086] \( u(t3) = 0.03 \, °C \), resulting in
[0087] 6) The uncertainty component introduced by the atmospheric pressure \( pb \) is calculated to obtain the sensitivity coefficient \( cpb \);
[0089] According to the calibration certificate and relevant technical data, the standard uncertainty of the barometer is 0.5% FS, with a measurement range of 80 kPa to 110 kPa. The standard uncertainty of the atmospheric pressure \( u(pb) = 0.55 \, kPa \), resulting in
[0090] 7) The uncertainty component introduced by the static pressure \( p2 \) before the nozzle is calculated to obtain the sensitivity coefficient.
[0092] According to the calibration certificate and relevant technical data, the accuracy level of the static pressure \( p \) before the nozzle is level 0.5, with a digital pressure gauge measurement range of 50 Pa to 500 Pa, resulting in a standard uncertainty of 2.5 Pa. Since \( p2 = pb – p \), according to the uncertainty propagation theorem, the standard uncertainty \( u(p2) = 0.5 \, kPa \), resulting in
[0093] 8) The uncertainty component introduced by the pressure difference ( \Delta p ) before and after the nozzle is calculated to obtain the sensitivity coefficient ( c\Delta p );
[0095] According to the calibration certificate and relevant technical data, the accuracy level of the pressure difference \( \Delta p \) before and after the nozzle is level 0.2, with a digital pressure gauge measurement range of 0 Pa to 1000 Pa, resulting in a standard uncertainty of \( u(\Delta p) = 2.0 \, Pa \), leading to \( c\Delta pu(\Delta p) = 8.22 \, W; \)
[0096] 9) The uncertainty component introduced by the nozzle diameter \( D \) is calculated to obtain the sensitivity coefficient \( cD \);
[0098] The vernier caliper used meets the requirements of JJG30-2012, with a measurement error of 0.02 mm, resulting in a standard uncertainty of \( u(D) = 0.00002 \, m \), leading to \( cDu(D) = 1.69 \, W; \)
[0099] Based on the above data, a summary is provided in Table 1,
[0100] **Table 1: Summary of Measurement Uncertainty Components.
[0102] According to the values of \( |ci ui| \) in Table 1, there are many factors that influence the cooling capacity, among which the effects of the wet bulb temperatures \( tw1 \) and \( tw2 \) are particularly prominent, being the largest among the nine influencing factors and playing an absolute dominant role. Under conditions where other factors remain unchanged, if the measurement error of the wet bulb sensor is assumed to be \( 0.03 \, °C \) or \( -0.03 \, °C \), the “bs value” of the indoor wet bulb sensor is adjusted for correction to simulate the situation where environmental humidity deviates due to inaccurate wet bulb temperature measurement. Experimental data shows that for every \( 0.03 \, °C \) deviation in wet bulb temperature, the environmental relative humidity changes by approximately \( 0.2\% \, RH \), and the corresponding cooling capacity of the tested air conditioner changes by about \( 17 \, W \). This indicates that the accuracy of the wet bulb temperature has a significant impact on the ability to test the cooling capacity using the enthalpy method, with specific data shown in Table 2.
[0103] **Table 2: Cooling Capacity Test Data at Different “bs Value” Settings
[0105] From the above uncertainty analysis and experimental data, it can be seen that accurately measuring the wet bulb temperature and ensuring the accuracy and stability of the environmental relative humidity is crucial. Currently, most laboratories using the air enthalpy method control the relative humidity of the environment using the dry-wet bulb method. This method utilizes dry and wet bulb temperature sensors under the same wind speed conditions to calculate the relative humidity based on their temperature difference. The wet bulb temperature sensor is wrapped in well-matched gauze, with the excess gauze connected to a water container. The moisture evaporation on the gauze takes away heat from the wet bulb, causing its temperature to be lower than that of the dry bulb. The efficiency of moisture evaporation on the wet bulb gauze directly affects the wet bulb temperature, and it has been found that this is a function of wind speed and the moisture content in the surrounding air. In step S4, the control variable method is used, and the calculation formula is as follows:
[0110] Where \( U \) is the environmental relative humidity in %RH; \( t \) is the dry bulb temperature in °C; \( tw \) is the wet bulb temperature in °C; \( ew \) is the saturated vapor pressure at the wet bulb temperature in Pa; \( es \) is the saturated vapor pressure at the dry bulb temperature in Pa; \( A \) is the dry-wet bulb coefficient; \( P \) is the atmospheric pressure in Pa; \( v \) is the wind speed in m/s;
[0111] The theoretical values of relative humidity at different wind speeds are calculated and presented in Table 3.
[0112] **Table 3: Theoretical Values of Relative Humidity at Different Wind Speeds
[0114] Based on the above data, the trend of relative humidity with changes in wind speed is shown in Figure 2.
[0115] According to step S5, GB/T 7725-2004 “Room Air Conditioners,” section C.1.3 requires that “the airflow velocity at the wet bulb thermometer should not be less than 5 m/s.” Therefore, using a wind speed of 5 m/s as the reference point, the corresponding reference point for relative humidity from Table 3 is 46.5% RH. According to experimental data, it is known that “the environmental relative humidity changes by approximately 0.2% RH, and the corresponding cooling capacity of the tested air conditioner changes by about 17 W.” This establishes the relationship between the differences corresponding to wind speed values and reference points in Table 4.
[0116] Table 4: Relationship Between Wind Speed Values and Corresponding Reference Points
[0118] Based on Table 4, the formulas for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds are derived, as shown in Figures 3 and 4. The deviation formulas are as follows:
[0119] When the wind speed is below 5 m/s, the formula for calculating the deviation of the rated cooling capacity is:
[ y = 3.5907x^4 – 52.606x^3 + 284.34x^2 – 681.11x + 629.18; ]
[0120] When the wind speed is above 5 m/s, the formula for calculating the deviation of the rated cooling capacity is:
[ y = 0.0004x^4 – 0.0159x^3 – 0.0012x^2 + 4.6443x – 20.73. ]
[0123] The working principle of the present invention: The invention utilizes the air enthalpy method to measure the air supply parameters, return air parameters, and circulating air volume of the air conditioner. The capacity of the air conditioner is determined using the product of the measured airflow and the difference in enthalpy of the supply and return air. The uncertainty components are calculated using the “sensitivity coefficient,” and the factors that play an absolute dominant role are selected for further analysis. The control variable method is used to discuss the accuracy analysis of these influencing factors under different wind speeds, leading to the derivation of formulas for calculating the deviation of the rated cooling capacity of the air conditioner at different wind speeds. Based on extensive data and accurate experiments, a new calculation method is proposed that enables the calculation of the deviation of the rated cooling capacity of the air conditioner at different wind speeds, filling a gap in this field.
[0124] It should be noted that terms such as “first” and “second” used herein are merely for distinguishing one entity or operation from another and do not necessarily require or imply any actual relationship or sequence between these entities or operations. Furthermore, the terms “include,” “comprise,” or any other variations thereof are intended to cover non-exclusive inclusions, thereby allowing processes, methods, articles, or devices that include a range of elements to not only include those elements but also other elements not explicitly listed, or inherent to such processes, methods, articles, or devices.[0125] Finally, it should be noted that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or make equivalent substitutions of some of the technical features. 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.
