A dehumidification control method for a rotary dehumidification system

Abstract

The present invention relates to a dehumidification control method for a rotary dehumidification system, the method comprising: taking the equivalent temperature difference between the air state at the rotary inlet and the target air state as the basis for feedforward control, fitting the relationship function between the rotation speed and the equivalent temperature difference based on the parameters of the design working condition and the non-design working condition, obtaining the calculation formula of the rotary speed relative to the equivalent temperature difference, and taking it as the basis for the rough adjustment of the rotary speed, so that the rotary speed quickly approaches the rotation speed that can meet the dehumidification amount. According to the deviation between the target humidity and the humidity at the rotary outlet and the rate of change of the deviation, the rotary speed is fine-tuned; based on the size of the humidity deviation from the measurement accuracy of the humidity sensor, different control strategies are set for different deviation ranges, and when the deviation is large, a larger variation range is set to achieve rapid reduction of the deviation; when the deviation is small, a smaller variation range is set to improve the stability of the control. The present invention improves the response speed and stability of the rotary dehumidification control.

Description

Technical Field

[0001] The present invention relates to the field of dehumidification technology, and in particular to a dehumidification control method for a rotary dehumidification system. Background Art

[0002] Rotary dehumidification technology is an efficient and environmentally friendly dehumidification technology that can use solar energy, industrial waste heat, geothermal heat, and ship waste heat for heat-driven dehumidification. It has been widely used in the field of air conditioning. The dehumidification process of the rotary wheel can be divided into a treatment process and a regeneration process, which is essentially the adsorption and desorption process of water vapor in the adsorbent. During the treatment process, the adsorbent in the rotary wheel adsorbs water vapor in the air and releases adsorption heat, causing the air temperature to rise. The presence of adsorption heat will hinder the adsorption process. During the regeneration process, the adsorbent in the rotary wheel absorbs heat from the high-temperature air to obtain desorption heat, and desorbs the water vapor adsorbed during the treatment process from the adsorbent. The presence of desorption heat will hinder the desorption process.

[0003] During the working process, the wheel keeps rotating to keep the treatment process and regeneration process going continuously. The working process of the wheel is affected by many variables, such as the flow rate, temperature and humidity of the treatment air and the regeneration air, which will affect its working performance, and these influences are not linear, and there are even coupling relationships, such as the thermal and mass coupling of the adsorption and desorption processes. In addition, the dehumidification process of the wheel also has the characteristics of time lag. When the working conditions change, the dehumidification wheel that was originally in stable working cannot quickly regain stable working conditions, and sometimes even needs to rotate multiple times before it can obtain stable working conditions. Therefore, it can be seen that the dehumidification process of the wheel has the characteristics of multivariable, nonlinear, strong coupling and large time lag.

[0004] For the dehumidification process of the wheel, conventional control usually adopts simple speed increase and decrease or combines with ordinary PID control. Since the dehumidification process of the wheel has the characteristics of multivariable, nonlinear, strong coupling and large time lag, conventional control often requires a long time and more adjustment processes to obtain matching working conditions, and it is impossible to achieve dehumidification control of the wheel in a short time. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a dehumidification control method for a rotary dehumidification system.

[0006] The specific plan is as follows:

[0007] A dehumidification control method for a rotary dehumidification system comprises the following steps:

[0008] S1: Based on the inlet air temperature, inlet air humidity, target air temperature and target air temperature and humidity corresponding to different working conditions, the equivalent temperature difference between the inlet air and the target air corresponding to each working condition is calculated, and the wheel speed under the equivalent temperature difference is obtained; the different working conditions include design working conditions and multiple groups of non-design working conditions;

[0009] S2: By performing curve fitting on the equivalent temperature difference and the runner speed corresponding to the design working condition and multiple groups of non-design working conditions, a calculation formula for the runner speed relative to the equivalent temperature difference is obtained;

[0010] S3: When performing dehumidification control, first calculate the equivalent temperature difference required to achieve the dehumidification target, and then calculate the corresponding rotor speed as the coarse adjustment speed of the rotor through the calculation formula of step S2;

[0011] S4: Measure the air humidity at the wheel outlet, calculate the humidity deviation between the target air humidity corresponding to the dehumidification target and the measured air humidity and the change of the deviation, and set the fine-tuning speed of the wheel based on the size of the humidity deviation from the measurement accuracy of the humidity sensor, and use the coarse-tuning speed + fine-tuning speed to adjust the speed of the wheel.

[0012] Furthermore, the calculation formula of the equivalent temperature of air is:

[0013]

[0014] in, TT represents the equivalent temperature of air, T Indicates the temperature of the air, H Indicates the humidity of the air. qw represents the adsorption heat of water vapor on the adsorbent, cpa Represents the specific heat of air.

[0015] Furthermore, the operating conditions used for curve fitting include a set of design operating conditions and three sets of non-design operating conditions, and the corresponding fitting function is a cubic equation.

[0016] Furthermore, based on the size of the humidity deviation from the measurement accuracy of the humidity sensor, the method for setting the fine-tuning speed of the rotating wheel is: when the humidity deviation deviates from the measurement accuracy more, the value range of the fine-tuning speed is larger; when the humidity deviation deviates from the measurement accuracy less, the value range of the fine-tuning speed is smaller.

[0017] Furthermore, based on the magnitude of the humidity deviation from the measurement accuracy of the humidity sensor, the fine-tuning speed of the rotor is set to three working conditions:

[0018] Condition 1: Humidity deviation satisfies |△ H |≤|a*e H |, where △ H Indicates humidity deviation, e Hrepresents the measurement accuracy, and a represents the coefficient;

[0019] Condition 2: Humidity deviation satisfies 2*|a*e H |≥|△ H |>|a*e H |;

[0020] Condition 3: Humidity deviation satisfies |△ H |>2*|a*e H |;

[0021] When in working condition 1, the speed is not adjusted; when in working condition 3, the value range of the fine-tuning speed is greater than the value range of the fine-tuning speed in working condition 2.

[0022] Furthermore, when in working condition 2, in addition to considering the deviation △ H In addition, the change of deviation e1 is also considered, which is divided into the following three cases:

[0023] Case 1: △ H >0, e1≥0, at this time, the rotation speed of the runner is adjusted to N-△N0, N represents the coarse adjustment speed of the runner, △N0 is the maximum value within the range of the fine adjustment speed corresponding to working condition 2;

[0024] Case 2: △ H <0, e1≤0, at this time, adjust the rotation speed of the wheel to N+△N0;

[0025] Case 3: △ H ×e1<0, at this time, PID control is used to adjust the speed of the wheel, and the adjustment range is limited to ±△N0.

[0026] Furthermore, when in working condition 3, the rotation speed of the wheel is adjusted to N+1.5△N0 or N-1.5△N0.

[0027] The present invention adopts the above technical solution and a "coarse adjustment" + "fine adjustment" control solution to improve the response speed and stability of the rotary dehumidification control. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Shown is a flow chart of a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0029] To further illustrate various embodiments, the present invention provides drawings. These drawings are part of the disclosure of the present invention, which are mainly used to illustrate the embodiments and can be used in conjunction with the relevant descriptions in the specification to explain the operating principles of the embodiments. With reference to these contents, ordinary technicians in this field should be able to understand other possible implementations and advantages of the present invention.

[0030] The present invention will now be further described with reference to the accompanying drawings and specific implementation methods.

[0031] The embodiment of the present invention provides a dehumidification control method for a rotary dehumidification system, such as Figure 1 As shown, the method comprises the following steps:

[0032] In the rotary dehumidification system, the deviation refers to the difference between the humidity setting value and the air humidity at the outlet of the rotary wheel. Conventional controllers use one or more of the deviation, the change of the deviation and the change of the deviation as input. In order to increase the sensitivity of the control and enable the rotary dehumidification process to quickly obtain a smaller deviation, this embodiment adds a feedforward link, that is, the difference between the air humidity at the inlet of the rotary wheel and the set humidity is used as the feedforward input. However, both the temperature and humidity of the air will affect the dehumidification effect of the rotary wheel. If the air temperature is also used as an input, an input will be added, which will complicate the control. Considering that the adsorption heat generated during the rotary dehumidification is released into the air, the air temperature will rise. Therefore, in this embodiment, the degree of temperature increase is used to estimate the dehumidification effect, and the humidity is converted into temperature. In this way, the temperature and humidity are unified as equivalent temperature to measure the working condition of the rotary wheel.

[0033] Assume that the specific heat of air is cpa (kJ / (kg*K)), the adsorption heat of water vapor on the adsorbent is qw (kJ / kg); the temperature and humidity of the air are T (℃) and H (g / kg), then the equivalent temperature of the air TT The calculation formula is:

[0034] (1)

[0035] The air temperature and humidity at the rotor inlet (i.e., processed air) are Ten (℃) and Hello (g / kg(da)), the target temperature and humidity of the air are Two (℃) and Ho (g / kg(da)). According to formula (1), the equivalent temperature of the air at the rotor inlet is TTi for:

[0036] (2)

[0037] According to formula (1), the equivalent temperature corresponding to the target air treatment is TTo for:

[0038] (3)

[0039] The difference between the equivalent temperature at the runner inlet and the target equivalent temperature is TT for:

[0040] (4)

[0041] Because TT That is, the equivalent temperature difference between the air state at the rotor inlet and the target air state reflects the size of the dehumidification task, so it is used as the basis for "rough adjustment". TT As one of the inputs for rotary dehumidification control.

[0042] The output of the rotary dehumidification control is the rotation speed of the rotary wheel. In order to obtain the corresponding relationship between the equivalent temperature difference and the rotation speed, a curve fitting method is adopted in this embodiment. The design working condition of the rotary dehumidification air conditioner is used. It is assumed that the rotary inlet air temperature and humidity corresponding to the design working condition are T 1 and H 1. The target air temperature and humidity are T 0 and H 0, the speed that satisfies this working condition is n0. Then under this design working condition, the corresponding equivalent temperature difference △ TT 0 is:

[0043] (5)

[0044] In order to improve the control accuracy, the equivalent temperature difference is taken as b1*△ TT 0, b2*△ TT 0 and b3*△ TT 0, where the range of b1, b2 and b3 is 0~1, and b1>b2>b3, the corresponding speeds are n1, n2 and n3 respectively. Using the above equivalent temperature difference and speed, the data fitting function is:

[0045] n=a0× △TT +a1× △TT 2+a2× △TT 3+a3(6)

[0046] The above equation is a cubic equation, where n represents the wheel speed, △TT Represents the equivalent temperature difference of air, and a0, a1, a2, and a3 are coefficients to be fitted.

[0047] The fitting function can be used to obtain the rough speed of other required working conditions, assuming it is N. After the "rough adjustment" feedforward adjustment, the speed of the wheel has quickly approached the requirements of the dehumidification task, but the wheel speed still needs to be "finely adjusted".

[0048] The parameters used for “fine tuning” in this embodiment include: the deviation of the humidity at the rotor outlet △ Hand the change of deviation e1, fine-tuning the speed based on the humidity deviation △ H The deviation is set based on the measurement accuracy of the humidity sensor.

[0049] Deviation of the humidity at the rotor outlet△ H is defined as:

[0050] (7)

[0051] In the formula, △ Ht The unit of deviation of the humidity at the rotor outlet at the current moment is g / kg; H The target humidity at the rotor outlet is marked in g / kg; Ht It is the humidity at the rotor outlet at the current moment, in g / kg.

[0052] e1 is defined as:

[0053] (8)

[0054] in, e 1t represents the change of the humidity deviation at the wheel outlet at the current moment, and t represents time.

[0055] Assuming that the fine adjustment speed corresponding to "fine adjustment" is represented by △N, the speed of "coarse adjustment" + "fine adjustment" is expressed as: N±△N. The fine adjustment speed △N can be set in a value range according to actual conditions, assuming that its basic value range is ±△N0.

[0056] Assuming that the measurement accuracy of the humidity sensor is ±eH, in order to take into account both the stability of control and the response speed of "fine tuning", this embodiment sets different control strategies for different deviation ranges of the humidity at the wheel outlet.

[0057] Condition 1: When the deviation of the humidity at the runner outlet is |△ H When |≤|a*eH| (a is a coefficient; too large a will result in poor control accuracy, and too small a will result in unstable control), the speed does not change.

[0058] Working condition 2: When 2*|a*eH|≥|△ H |>|a*eH|, at this time, the humidity deviation at the wheel outlet is small. At this time, the value range of fine-tuning the speed is △N2=±△N0.

[0059] Condition 3: When |△ H |>2*|a*eH|, at this time, the deviation of the humidity at the rotor outlet is large, and a larger fine-tuning speed is set to improve the response speed. At this time, the value range of the fine-tuning speed is △N3=±1.5△N0. The value range of the fine-tuning speed in working condition 3 is greater than that in working condition 2.

[0060] When in working condition 3, set the rotation speed of the wheel within the upper and lower limits of its value range N±1.5△N0 (but not exceeding the maximum rotation speed of the wheel). According to the humidity control requirements, increase or decrease the dehumidification amount so that the humidity at the wheel outlet is close to the set humidity until entering working condition 2.

[0061] When in working condition 2, since it is close to the dehumidification requirement, in order to reduce overshoot, the control strategy is further refined, including the following three cases.

[0062] Case 1: △ H >0, e1≥0, the dehumidification capacity of the system is too large, and the humidity at the wheel outlet decreases, the dehumidification capacity is far from the dehumidification target, and the speed is set to N-△N0, corresponding to the coarse adjustment speed N and the fine adjustment speed-△N0;

[0063] Case 2: △ H <0, e1≤0, the dehumidification capacity of the system is insufficient, and the humidity at the wheel outlet increases, the dehumidification capacity is far from the dehumidification target, and the speed is set to N+△N0, corresponding to the coarse adjustment speed N and the fine adjustment speed △N0;

[0064] Case 3: △ H ×e1<0, at this time, the dehumidification capacity of the system is close to the dehumidification target, and the speed is adjusted using ordinary PID control, and the adjustment range is limited to ±△N0.

[0065] The following is an illustration using a specific case.

[0066] Assume that the adsorption heat of the adsorption process is released into the treated air, resulting in a temperature rise. The constant pressure specific heat capacity of air: cpa = 1.005 kJ / (kg*K); the adsorption heat of water vapor on silica gel: qw = 2650 kJ / kg. Assume that the design working conditions of the runner are the inlet air temperature and humidity: 31.4℃, 22.77 g / kg; the target air temperature and humidity are: 16℃, 8.82 g / kg. Then, according to formula (1), the equivalent temperatures can be calculated as: 91.5℃, 39.28℃ respectively; the equivalent temperature difference between the two is: △ TT 0=52.22℃, measure the speed n0 under the equivalent temperature difference condition.

[0067] The equivalent temperature difference is 0.8△ TT 0, 0.6△ TT 0 and 0.4 △ TT The speeds measured under the working condition of 0 are n1, n2 and n3 respectively.

[0068] Using the data of the above four working conditions, the relationship between the speed and the equivalent temperature difference is fitted, as shown in formula (6).

[0069] Under the working conditions required for actual dehumidification control, the “coarse adjustment” speed N is calculated using the fitting function.

[0070] Assuming that the measurement accuracy of the humidity sensor is ±0.3g / kg, the value of a*eH is limited to 0.5g / kg.

[0071] The basic range of the revolutions △N for “fine tuning” is set to ±2 revolutions / hour.

[0072] Condition 1: When the deviation of the humidity at the runner outlet is |△ H |≤0.5g / kg, the rotation speed does not change.

[0073] Working condition 2: When 1g / kg≥|△ H |>0.5g / kg, at this time, the humidity deviation at the wheel outlet is small, and the value range of fine-tuning the speed is △N2=±2 rpm.

[0074] Condition 3: When |△ H |>1g / kg, at this time, the humidity deviation at the rotor outlet is large, and the value range of the fine-tuning speed is set to △N3=±3 rpm, but not exceeding the maximum speed of the rotor.

[0075] When in working condition 3, set the speed within the upper and lower limits of N±3 (but not exceeding the maximum speed of the wheel). According to the humidity control requirements, increase or decrease the wheel speed so that the humidity at the wheel outlet is close to the set humidity until entering working condition 2.

[0076] When in working condition 2, since it is close to the dehumidification requirement, in order to reduce overshoot, the control strategy is further refined, including the following three cases.

[0077] Case 1: △ H >0, e1≥0, the dehumidification capacity of the system is too large, and the humidity at the wheel outlet decreases, the dehumidification capacity is far from the dehumidification target, and the speed is set to N-2;

[0078] Case 2: △ H <0, e1≤0, the dehumidification capacity of the system is insufficient, and the humidity at the wheel outlet increases, the dehumidification capacity is far from the dehumidification target, and the speed is set to N+2;

[0079] Case 3: △ H ×e1<0, at this time, the dehumidification capacity of the system is close to the dehumidification target, and the speed is adjusted using ordinary PID control, and the adjustment range is limited to ±2 rpm.

[0080] According to the characteristics of the rotary dehumidification, the embodiment of the present invention proposes a control strategy of "coarse adjustment" + "fine adjustment" from the perspective of improving the response speed and stability of the control, which has the following advantages:

[0081] ① Taking the equivalent temperature difference between the air state at the runner inlet and the target air state as the basis for feedforward control, the “rough adjustment” of the runner speed is achieved through the relationship between the speed and the equivalent temperature difference fitted at a small number of operating points, so that the runner speed quickly approaches the target speed;

[0082] ② On the basis of “coarse adjustment”, different control strategies are set for different deviation ranges of the humidity at the rotor outlet. When the deviation is large, a larger variation range is set to quickly reduce the deviation; when the deviation is small, PID control is limited to a smaller speed variation range to improve control stability;

[0083] ③The “coarse adjustment” + “fine adjustment” control scheme improves the response speed and stability of the rotary dehumidification control.

[0084] Although the present invention has been specifically shown and described in conjunction with the preferred embodiments, it should be understood by those skilled in the art that various changes may be made to the present invention in form and details without departing from the spirit and scope of the present invention as defined by the appended claims, all of which are within the scope of protection of the present invention.

Claims

1. A dehumidification control method for a rotary dehumidification system, characterized in that: The following steps are involved: S1: Based on the inlet air temperature, inlet air humidity, target air temperature and target air humidity corresponding to different working conditions, the equivalent temperature difference between the inlet air and the target air corresponding to each working condition is calculated, and the wheel speed under the equivalent temperature difference is obtained; different working conditions include design working conditions and multiple groups of non-design working conditions; the calculation formula of the equivalent temperature of air is: in, TT represents the equivalent temperature of air, T Indicates the temperature of the air, H Indicates the humidity of the air. q represents the adsorption heat of water vapor on the adsorbent, cpa represents the specific heat of air; S2: By performing curve fitting on the equivalent temperature difference and the runner speed corresponding to the design working condition and multiple groups of non-design working conditions, a calculation formula for the runner speed relative to the equivalent temperature difference is obtained; S3: When performing dehumidification control, first calculate the equivalent temperature difference required to achieve the dehumidification target, and then calculate the corresponding rotor speed as the coarse adjustment speed of the rotor through the calculation formula of step S2; S4: Measure the air humidity at the wheel outlet, calculate the humidity deviation between the target air humidity corresponding to the dehumidification target and the measured air humidity and the change of the deviation, and set the fine-tuning speed of the wheel based on the size of the humidity deviation from the measurement accuracy of the humidity sensor, and use the coarse-tuning speed + fine-tuning speed to adjust the speed of the wheel.

2. The dehumidification control method for a rotary dehumidification system according to claim 1, characterized in that: The operating conditions used for curve fitting include a set of design conditions and three sets of non-design conditions, and the corresponding fitting function is a cubic equation.

3. The dehumidification control method for a rotary dehumidification system according to claim 1, characterized in that: Based on the size of the humidity deviation from the measurement accuracy of the humidity sensor, the method for setting the fine-tuning speed of the rotating wheel is: when the humidity deviation deviates from the measurement accuracy more, the value range of the fine-tuning speed is larger; when the humidity deviation deviates from the measurement accuracy less, the value range of the fine-tuning speed is smaller.

4. The dehumidification control method for a rotary dehumidification system according to claim 3, characterized in that: Based on the humidity deviation from the measurement accuracy of the humidity sensor, there are three working conditions for setting the fine-tuning speed of the rotor: Condition 1: Humidity deviation satisfies |△ H |≤|a*e H |, where △ H Indicates humidity deviation, e H represents the measurement accuracy, and a represents the coefficient; Condition 2: Humidity deviation satisfies 2*|a*e H |≥|△ H |>|a*e H |; Condition 3: Humidity deviation satisfies |△ H |>2*|a*e H |; When in working condition 1, the speed is not adjusted; when in working condition 3, the value range of the fine-tuning speed is greater than the value range of the fine-tuning speed in working condition 2.

5. The dehumidification control method for a rotary dehumidification system according to claim 4, characterized in that: When in working condition 2, in addition to considering the deviation △ H In addition, the change of deviation e1 is also considered, which is divided into the following three cases: Case 1: △ H >0, e1≥0, at this time, the rotation speed of the runner is adjusted to N-△N0, N represents the coarse adjustment speed of the runner, △N0 is the maximum value within the range of the fine adjustment speed corresponding to working condition 2; Case 2: △ H <0, e1≤0, at this time, adjust the rotation speed of the wheel to N+△N0; Case 3: △ H ×e1<0, at this time, PID control is used to adjust the speed of the wheel, and the adjustment range is limited to ±△N0.

6. The dehumidification control method for a rotary dehumidification system according to claim 5, characterized in that: When in working condition 3, the rotation speed of the wheel is adjusted to N+1.5△N0 or N-1.5△N0.

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