A solar hot air combined drying device and its control method

Abstract

The present invention relates to a solar hot air combined drying device and its control method, comprising a heat collection unit, a water storage unit, a drying unit, and an electric heating unit; the heat collection unit includes a heat collection barrel and solar heat collecting tubes, capable of realizing solar heating; the water storage unit includes a water storage barrel and a heat exchanger, capable of realizing water-air heat exchange; the electric heating unit includes a heating tube and an electric heater, capable of realizing electric heating; the drying unit includes a drying chamber; the heat collection unit, the water storage unit, the drying unit, and the electric heating unit are connected through corresponding pipelines to form a closed-loop air circulation path, so as to introduce hot air into the drying chamber, and can switch between different drying modes according to different irradiation conditions. Thus, it can not only achieve precise temperature control, but also enable effective utilization and storage of thermal energy. Moreover, it can also avoid losses caused by reverse heat input, improving the utilization efficiency of heat.

Description

Technical Field

[0001] The present invention relates to an agricultural device and a control method thereof, in particular to a drying device using solar energy and a control method thereof, specifically a solar hot air combined drying device and a control method thereof. Background Art

[0002] Solar energy has the advantages of being clean, pollution-free, renewable, rich in resources, and widely distributed. It has long been valued by countries around the world and is one of the key research contents in the global research on new energy and renewable energy. China has relatively rich solar energy resources. About 2 / 3 of the country's territory has an annual radiation duration of more than 2200h, and the annual radiation total exceeds 5000MJ / m 2 . Making full use of solar energy resources in the field of material drying can reduce the dependence on conventional energy. Therefore, solar drying technology has become a hot research field at home and abroad.

[0003] At present, solar drying modes can be divided into three types: direct drying, indirect drying, and hybrid drying. In the direct solar drying mode, the materials in the drying chamber directly receive the heat energy from solar radiation. This mode has a simple structure and is easy to operate, but the temperature of the drying medium is not constant, making it difficult to ensure the drying rate and product quality of agricultural products. In the indirect solar drying mode, solar energy is first converted into electrical energy, and then technologies such as hot air, freezing, and infrared drying are used for drying agricultural products. However, this method involves two energy conversions of solar energy, electrical energy, and heat energy, resulting in energy loss and reducing the energy utilization efficiency. Therefore, some solar drying devices with hybrid drying methods have also emerged, such as the existing patents "A solar combined drying system and its operation method 202210901155.7", "A solar drying system capable of drying multiple materials and its usage method 202110056614.1", and "A solar drying system integrating heat absorption, heat storage, and water collection 201910978928.X", etc. Although these patented technologies overcome the defect of a single drying mode, they still have the following deficiencies:

[0004] (1) Under high irradiation intensity, heat utilization and temperature regulation cannot operate synchronously, or when they operate synchronously, the energy cannot be fully utilized. There is a situation where the effective utilization of heat under high irradiation intensity cannot be guaranteed, or the temperature cannot be effectively regulated, affecting the drying quality;

[0005] (2) At night or under low irradiation intensity, various drying modes cannot be effectively switched, resulting in energy loss (such as heating other modules in the reverse direction), making the energy consumption of the entire system more than that of a single drying mode.

[0006] Therefore, further improvement is needed to better meet the market demand. Summary of the Invention

[0007] The object of the present invention is to provide a solar hot air combined drying device and its control method in view of the deficiencies of the prior art, which can make more full use of solar energy and improve the drying efficiency by combining multiple drying modes. Moreover, it can automatically switch between different drying modes and avoid energy loss.

[0008] The technical solution of the present invention is as follows:

[0009] A solar hot air combined drying device includes a heat collection unit, a water storage unit, a drying unit, and an electric heating unit;

[0010] The heat collection unit includes a heat collection barrel; the heat collection barrel is connected to a solar heat collecting pipe and can heat the air passing through the heat collection barrel;

[0011] The water storage unit includes a water storage barrel and a heat exchanger; there is water stored in the water storage barrel; the heat exchanger is a water-air heat exchanger, which is arranged in the water storage barrel and immersed in water;

[0012] The electric heating unit includes a heating pipe; an electric heater is arranged in the heating pipe and can heat the air in the heating pipe;

[0013] The drying unit includes a drying chamber; the drying chamber is in a box shape and can introduce hot air to dry the items stored therein; a moisture exhaust air outlet is arranged on the side wall of the drying chamber;

[0014] The air inlet of the heat collection barrel is connected to the air outlet of the drying unit through pipeline I, and its air outlet is connected to the inlet of the heating pipe through pipeline II; the outlet of the heating pipe is connected to the air inlet of the drying unit through pipeline III; the air inlet and air outlet of the heat exchanger are respectively connected to pipeline II through pipeline IV and pipeline V, and controlled control valves I and II are respectively arranged at the connection points; the control valve II is located between the control valve I and the inlet of the heating pipe; a pipeline VI is also included, one end of which is connected to pipeline I and a controlled control valve III is arranged at the connection point, and the other end is connected to the control valve I;

[0015] A circulation fan is arranged at the air outlet of the drying unit;

[0016] Temperature sensors are respectively arranged in the heat collection barrel, at the air outlet of the heat exchanger, and in the drying unit; the temperature sensors are respectively electrically connected to a controller;

[0017] A blind pipe I is arranged at the air inlet of the heat collection barrel; a blind pipe II is arranged at the air inlet of the heat exchanger; a blind pipe III is arranged on pipeline VI; the blind pipe I, blind pipe II, and blind pipe III are all connected to the outside and can be controlled to open and close.

[0018] Further, multiple sets of the heat collection units are connected in series with each other.

[0019] Further, the water storage bucket is vertically arranged in a cylindrical shape, with a water inlet at its upper part, a drain outlet at its lower part, and a heat preservation layer on its outer part; the water inlet is communicated with the water storage bucket; the drain outlet is controlled.

[0020] Further, the heat exchanger is made of "Z"-shaped copper tubes arranged closely and is uniformly arranged along the bottom and the periphery of the water storage bucket.

[0021] Further, symmetric limiting plates are longitudinally arranged inside the drying chamber; limiting grooves are respectively arranged on the side walls of the two limiting plates; a movable material drying supporting tray is horizontally and symmetrically arranged inside the two limiting plates; two temperature and humidity sensors at different heights are arranged on the material drying supporting tray; the temperature and humidity sensors are electrically connected to the controller; an exhaust fan is arranged on the moisture exhaust air outlet.

[0022] A control method for a solar hot air combined drying device includes the following steps:

[0023] Step 1: Before the drying device starts to operate, set the maximum drying temperature max(t) and the minimum drying temperature min(t) according to the characteristics of the material to be dried.

[0024] Step 2: Read the current value s(t) of the temperature of the heat collection unit and the current value q(t) of the temperature of the water storage unit.

[0025] Step 3: Calculate the following values:

[0026] (1) Calculate the maximum difference amount e(t) of the heat collection unit, and the calculation formula is: e(t)=max(t)-s(t);

[0027] (2) Calculate the minimum difference amount d(t) of the heat collection unit, and the calculation formula is: d(t)=s(t)-min(t);

[0028] (3) Calculate the maximum difference amount k(t) of the water storage unit, and the calculation formula is: k(t)=max(t)-q(t);

[0029] (4) Calculate the minimum difference amount f(t) of the water storage unit, and the calculation formula is: f(t)=q(t)-min(t);

[0030] Step 4: Run the drying program according to the following conditions:

[0031] (1) If e(t)<0, execute the second case of the independent drying mode of the heat collection unit;

[0032] (2) If e(t) > 0 and d(t) > 0, execute the first case of the independent drying mode of the heat collection unit;

[0033] (3) If e(t) > 0, d(t) < 0, and k(t) < 0, execute the one-time water transfer from the water storage bucket to the water storage tank;

[0034] (4) If e(t) > 0, d(t) < 0, k(t) > 0, and f(t) > 0, execute the independent drying mode of the water storage unit;

[0035] If e(t) > 0, d(t) < 0, k(t) > 0, and f(t) < 0, execute the independent drying mode of the electric heating unit;

[0036] Step Five: Detect the moisture content of the material. If it is greater than the set target moisture content, continue drying; if it is less than the set target moisture content, end the drying.

[0037] Further, the first case of the independent drying mode of the heat collection unit in Step Four is as follows: Adjust control valve I, control valve II, and control valve III to make pipeline I and pipeline II unobstructed; then, open the port of blind pipe I for several minutes and then close it. External air enters the heat collection barrel, is heated by the solar heat collector tube, and then enters the drying chamber through pipeline II and pipeline III to dry the material therein. Then, it flows back to the heat collection barrel through pipeline I and operates in a cycle; during this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan, and at the same time open the port of blind pipe I to discharge part of the air in the drying chamber and supplement external air; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of blind pipe I at the same time.

[0038] Further, the second case of the independent drying mode of the heat collection unit in Step Four is as follows: Adjust control valve I, control valve II, and control valve III to make pipeline I and pipeline II unobstructed, make part of pipeline IV unobstructed, and pipeline V communicate with pipeline II; then, open the port of blind pipe I for several minutes and then close it. At the same time, external air enters the heat collection barrel, is heated by the solar heat collector tube, and part of it flows into the heat exchanger through pipeline IV and exchanges heat with the water in the water storage bucket to reduce the temperature, and then flows back to pipeline II through pipeline V, converges with the original air, and enters the drying chamber after the temperature is reduced to dry the material therein. Then, it flows back to the heat collection barrel through pipeline I and operates in a cycle; during this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of blind pipe I to supplement external air to the circulation pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of blind pipe I at the same time.

[0039] Further, the independent drying mode of the water storage unit in step four is as follows: adjust control valve I, control valve II, and control valve III to make pipeline I communicate with pipeline IV through pipeline VI; at the same time, pipeline V communicates with pipeline II; then, open the port of the blind pipe II for several minutes and then close it. External air enters the heat exchanger, exchanges heat with the water in the water storage bucket and the temperature rises, and then enters the drying chamber through pipeline V, pipeline II, and pipeline III to dry the materials therein. Finally, it flows back to the heat exchanger through pipeline I, pipeline VI, and pipeline IV to form a circulating operation; during this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of the blind pipe II to supplement external air into the circulating pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of the blind pipe II at the same time.

[0040] Further, the independent drying mode of the electric heating unit in step four is as follows: adjust control valve I, control valve II, and control valve III to make pipeline I communicate with pipeline II through pipeline VI; then, turn on the circulating fan, open the port of the blind pipe III for several minutes and then close it. External air enters pipeline VI, then enters the heating pipe through pipeline II, is heated by the electric heater, and then enters the drying chamber through pipeline III to dry the materials therein; then, it flows out of the drying chamber and flows back into pipeline VI through pipeline I to form a cycle; during this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of the blind pipe III to supplement external air into the circulating pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of the blind pipe III at the same time.

[0041] Advantages of the present invention:

[0042] 1. Under high irradiation intensity, the present invention diverts the heated air, with a part entering the drying unit and a part entering the water storage unit. By exchanging heat with the water storage unit, the temperature of the water in the water storage tank can be increased, and the air temperature can be reduced at the same time. After mixing with the air entering the drying unit, the required drying temperature is met. Thus, accurate temperature control can be achieved, and at the same time, heat energy can be effectively utilized and stored.

[0043] 2. When the present invention works under low irradiation intensity or even at night, it can work in an electric energy working mode to ensure continuous drying. At the same time, through the effective switching between the solar energy - electric energy drying methods, the loss caused by the reverse input of heat is avoided, and the heat utilization efficiency is improved.

[0044] 3. The present invention realizes that the thermal energy stored under high irradiation intensity is used to supply heat to the drying chamber under low irradiation intensity. That is, on the one hand, the heat of the water storage unit is used to heat the ambient air entering the system to supplement the air dissipated by the moisture exhaust fan and prevent the air temperature in the system from decreasing. On the other hand, since the water storage unit and the electric heating unit are in relatively independent circulation pipelines, it is possible to avoid the situation where the electric heating unit outputs heat reversely to the water storage unit at low temperatures, thereby improving the energy utilization efficiency. Brief Description of the Drawings

[0045] Figure 1 is a schematic structural diagram of the present invention.

[0046] Figure 2 is a schematic structural diagram of the heat collection unit.

[0047] Figure 3 is an operation schematic diagram of the first case of the independent drying mode of the heat collection unit of the present invention.

[0048] Figure 4 is an operation schematic diagram of the second case of the independent drying mode of the heat collection unit of the present invention.

[0049] Figure 5 is an operation schematic diagram of the independent drying mode of the water storage unit of the present invention.

[0050] Figure 6 is an operation schematic diagram of the independent drying mode of the electric heating unit of the present invention.

[0051] Figure 7 is a schematic diagram of the working process of the present invention.

[0052] Among them, 1 - circulation fan; 2 - moisture exhaust fan; 3 - drying chamber; 4 - pipeline III; 5 - electric heating unit; 6 - control valve III; 7 - blind pipe III; 8 - pipeline I; 9 - blind pipe I; 10 - heat collection unit; 101 - solar heat collection pipe; 102 - manifold; 103 - heat collection barrel; 104 - elbow; 11 - blind pipe II; 12 - water storage barrel; 13 - drain port; 14 - water storage bucket; 15 - pipeline V; 16 - control valve II; 17 - control valve I; 18 - pipeline IV; 19 - heat exchanger; 20 - pipeline II; 21 - pipeline VI. The arrow direction in the figure is the air flow direction. Detailed Embodiments

[0053] The present invention will be further described below in conjunction with the drawings and embodiments. [[ID=4"]]

[0054] As Figure 1 and 2 shown.

[0055] A solar hot air combined drying device includes a heat collection unit 10, a water storage unit, a drying unit, an electric heating unit 5, etc.

[0056] The heat collection unit is similar to a solar water heater and includes a heat collection barrel 103 and solar heat collection tubes 106. The heat collection barrel 103 is in a horizontally placed cylindrical shape, with an air inlet and an air outlet provided at its two ends respectively. There are multiple solar heat collection tubes 101, which are arranged in parallel. The upper ends of them are placed inside the heat collection barrel 103, and are connected through elbow pipes 104 at their upper and lower ports respectively, so that all the solar heat collection tubes form a continuous S-shaped tube. Then, the port of the S-shaped tube close to the air inlet is connected to the air inlet through a manifold 102, and the other port is connected to the heat collection barrel. Thus, after collecting solar energy through the solar heat collection tubes, the air passing through them can be heated. Preferably, there are two or more groups of such heat collection units, which are connected in series to improve the heating efficiency. A temperature sensor is provided at the air outlet to detect the temperature of the air flowing out of the heat collection barrel.

[0057] The water storage unit includes a water storage barrel 12 and a heat exchanger 19. The water storage barrel 12 is in a vertically placed cylindrical shape, in which water can be stored. An insulating layer is provided outside it to prevent the water temperature from quickly dissipating. An inlet is provided at the upper part of the water storage barrel 12, which is connected to the water storage barrel 14, and the water in the water storage barrel can be input into this water storage barrel. A drain port 13 is provided at the lower part of the water storage barrel 12, through which the water in the water storage barrel can be discharged to adjust the water volume in the water storage barrel. The drain port 13 is controllable and can be opened and closed as needed.

[0058] The heat exchanger 19 is a water-air heat exchanger, which is made of closely arranged "Z"-shaped copper tubes and is uniformly arranged along the bottom and the periphery of the water storage barrel 12. The heat exchanger 19 is immersed in water to fully exchange heat between the air therein and the water outside it.

[0059] The electric heating unit 5 includes a heating pipe. An electric heater is provided inside the heating pipe. After the electric heater is powered on, it generates heat and can heat the air inside the heating pipe.

[0060] The drying unit includes a drying chamber 3, which can introduce hot air to dry the items stored therein. The drying chamber 3 is in a box shape, and symmetric limiting plates are longitudinally and fixedly arranged inside it. Limiting grooves are respectively provided on the side walls of the two limiting plates. Horizontally and symmetrically arranged movable material drying trays are provided inside the two limiting plates. Two humidity and temperature sensors at different heights are provided on the material drying trays to detect the humidity at different heights inside the drying chamber, so as to obtain more accurate humidity information inside the drying chamber. The humidity and temperature sensors are electrically connected to the controller to timely send the detected information to the controller.

[0061] The side wall of the drying chamber 3 is provided with a moisture exhaust air vent communicating with the outside, and a moisture exhaust fan 2 is provided on the moisture exhaust air vent. The moisture exhaust fan can be turned on when needed to exhaust the air with higher humidity in the drying chamber.

[0062] The heat collection unit, the water storage unit, the drying unit and the electric heating unit are connected through corresponding pipelines to form a closed-loop air circulation path. Specifically: the air inlet of the heat collection barrel is connected to the air outlet of the drying unit through pipeline I8, and its air outlet is connected to the inlet of the heating pipe through pipeline II20; the outlet of the heating pipe is connected to the air inlet of the drying unit through pipeline III4; the air inlet and the air outlet of the heat exchanger are respectively connected to pipeline II20 through pipeline IV18 and pipeline V15, and controlled control valves I17 and control valves II16 are respectively provided at the connection points. At the same time, the control valve II16 is located between the control valve I17 and the inlet of the heating pipe. It also includes pipeline VI21, one end of which is connected to pipeline I8, and a controlled control valve III6 is provided at the connection point, and the other end is connected to the control valve I17. The control valve I17 and the control valve III6 are both multi-way solenoid valves, and the control valve II16 is a one-way control valve. The control valve I17, the control valve II16 and the control valve III6 are all electrically connected to the controller and can be controlled to act to adjust the on-off of the relevant connection points.

[0063] A circulation fan 1 is provided at the air outlet of the drying unit to provide power for the air circulation path.

[0064] Temperature sensors are respectively provided in the heat collection barrel, at the air outlet of the heat exchanger and in the drying chamber. The temperature sensors are respectively electrically connected to the controller and can detect the temperature in the relevant areas.

[0065] A blind pipe I9 is provided at the air inlet of the heat collection barrel. A blind pipe II11 is provided at the air inlet of the heat exchanger. A blind pipe III7 is provided on the pipeline VI21. The outer ends of the blind pipe I9, the blind pipe II11 and the blind pipe III7 are all communicated with the outside and can be controlled to open and close, and the air circulation path can be communicated with the outside when needed.

[0066] The controller can be an industrial control computer, which can collect the detection information of each sensor, control the action of the solenoid valve, realize the switching of different drying modes, and achieve the maximum efficiency of energy utilization. At the same time, it can also be equipped with an Internet of Things system, which can realize the synchronous data upload of multiple regions and multiple parameters, start and run multiple energy storage type solar hot air combined drying device equipment distributed in different regions at the same time, and can collect remote data under different conditions, obtain the equipment operation and drying state information of the same equipment in different seasons, different external environmental temperature and humidity conditions, different materials, etc. in the same region, and then establish a database in the remote server through neural network operation, providing neural network prediction for further analyzing the equipment performance and processing in different environments and even different materials. The prediction results can provide a basis for further equipment improvement and real-time adjustment of process parameters.

[0067] A control method for a solar hot air combined drying device according to the present invention, as Figure 7 shown, includes the following steps:

[0068] Step 1: Before the drying device starts to run, set the maximum drying temperature max(t) and the minimum drying temperature min(t) according to the characteristics of the material to be dried;

[0069] Step 2: Read the current value s(t) of the relative temperature of the heat collection unit and the current value q(t) of the relative temperature of the water storage unit;

[0070] Step 3: Calculate the following values:

[0071] 1) Calculate the maximum difference amount e(t) of the heat collection unit, and the calculation formula is: e(t)=max(t)-s(t);

[0072] (2) Calculate the minimum difference amount d(t) of the heat collection unit, and the calculation formula is: d(t)=s(t)-min(t);

[0073] (3) Calculate the maximum difference amount k(t) of the water storage unit, and the calculation formula is: k(t)=max(t)-q(t);

[0074] (4) Calculate the minimum difference amount f(t) of the water storage unit, and the calculation formula is: f(t)=q(t)-min(t);

[0075] Step 4: Run the drying program according to the following conditions:

[0076] (1) If e(t)<0, execute the second case of the independent drying mode of the heat collection unit;

[0077] (2) If e(t)>0 and d(t)>0, execute the first case of the independent drying mode of the heat collection unit;

[0078] (3) If e(t) > 0, d(t) < 0, and k(t) < 0, the water storage bucket shall conduct one-time water conveyance to the water storage tank.

[0079] (4) If e(t) > 0, d(t) < 0, k(t) > 0, and f(t) > 0, the independent drying mode of the water storage unit shall be executed.

[0080] (5) If e(t) > 0, d(t) < 0, k(t) > 0, and f(t) < 0, the independent drying mode of the electric heating unit shall be executed.

[0081] Step Five: Detect the water content of the material. If it is greater than the set target moisture content, continue drying; if it is less than the set target moisture content, end drying.

[0082] Specifically,

[0083] As Figure 3 shown, the first case of the independent drying mode of the heat collection unit in Step Four is as follows: Adjust Control Valve I, Control Valve II, and Control Valve III to make Pipeline I and Pipeline II unobstructed; then, open the port of Blind Tube I for 30 minutes and then close it. External air enters the heat collection bucket, is heated by the solar heat collector tube, and then enters the drying chamber through Pipeline II and Pipeline III to dry the material therein. Then, it flows back to the heat collection bucket through Pipeline I and operates in a cycle. During this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of Blind Tube I to supplement external air to the circulation pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of Blind Tube I simultaneously.

[0084] As Figure 4 shown, the second case of the independent drying mode of the heat collection unit in Step Four is as follows: Adjust Control Valve I, Control Valve II, and Control Valve III to make Pipeline I and Pipeline II unobstructed, make a part of Pipeline IV unobstructed, and Pipeline V communicate with Pipeline II; then, open the port of Blind Tube I for 30 minutes and then close it. At the same time, external air enters the heat collection bucket, is heated by the solar heat collector tube, and then flows through Pipeline II to the electric heating tube. A part of the hot air therein flows through Pipeline IV into the heat exchanger and exchanges heat with the water in the water storage tank to reduce the temperature, and then flows back to Pipeline II through Pipeline V, converges with the original air, and then enters the drying chamber after the temperature is reduced to dry the material therein. Then, it flows back to the heat collection bucket through Pipeline I and operates in a cycle. During this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan and open the port of Blind Tube I at the same time to discharge part of the air in the drying chamber and supplement external air; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of Blind Tube I simultaneously.

[0085] As Figure 5 shown, the independent drying mode of the water storage unit in Step 4 is as follows: Adjust Control Valve I, Control Valve II, and Control Valve III so that Pipeline I is connected to Pipeline IV through Pipeline VI; at the same time, Pipeline V is connected to Pipeline II; then, open the port of Blind Tube II for several minutes and then close it. External air enters the heat exchanger, exchanges heat with the water in the water storage bucket and its temperature rises, and then enters the drying chamber through Pipeline V, Pipeline II, and Pipeline III to dry the materials therein. Finally, it flows back to the heat exchanger through Pipeline I, Pipeline VI, and Pipeline IV to form a circulating operation; during this period, the air humidity in the drying chamber is detected; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of Blind Tube II to supplement external air into the circulating pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of Blind Tube II at the same time.

[0086] As Figure 6 shown, the independent drying mode of the electric heating unit in Step 4 is as follows: Adjust Control Valve I, Control Valve II, and Control Valve III so that Pipeline I is connected to Pipeline II through Pipeline VI; then, turn on the circulating fan, open the port of Blind Tube III for several minutes and then close it. External air enters Pipeline VI, then enters the heating tube through Pipeline II, is heated by the electric heater, and then enters the drying chamber through Pipeline III to dry the materials therein; then, it flows out of the drying chamber and flows back into Pipeline VI through Pipeline I to form a cycle; during this period, the air humidity in the drying chamber is detected; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of Blind Tube III to supplement external air into the circulating pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of Blind Tube III at the same time.

[0087] In the second case of the independent drying mode of the heat collection unit and the independent drying mode of the water storage unit, the initial water volume in the water storage bucket is equal to the minimum water volume. This initial water storage volume is obtained by multiplying the solar radiation in this quarter of previous years minus the required drying heat by a coefficient. When the water temperature in the water storage bucket exceeds the set temperature, open the water inlet of the water storage bucket, and about 40L of water is transported from the water storage bucket to the water storage bucket to lower its water temperature below the received temperature. Among them, the water delivery volume = the average daily heat radiation in the local area ÷ ((the highest water temperature - the normal water temperature) × the specific heat capacity of water). The volume of the water storage bucket is 400L, which can fully meet the operation requirements.

[0088] A water level alarm device is also provided in the water storage bucket, which can issue an alarm when the water volume in the water storage bucket exceeds the limit. Then, manually open the drain port to drain about 100 L of water to lower the water level in the water storage bucket and avoid excessive water volume affecting the regulation.

[0089] Advantages of the present invention:

[0090] 1. Under high irradiation intensity, the present invention shunts the heated air. One part enters the drying unit, and the other part enters the water storage unit. By exchanging heat with the water storage unit, the temperature of the water in the heat preservation water tank can be increased, and the air temperature can be reduced. After mixing with the air entering the drying unit, the required drying temperature is met. Thus, accurate temperature control can be achieved, and at the same time, thermal energy can be effectively utilized and stored.

[0091] 2. When the present invention works under low irradiation intensity or even at night, it can work in an electric energy mode to ensure continuous drying. At the same time, through the effective switching of the solar-electric drying method, the loss caused by the reverse input of heat is avoided, and the heat utilization efficiency is improved.

[0092] 3. The present invention realizes that the thermal energy stored under high irradiation intensity is used to supply heat to the drying chamber under low irradiation intensity. That is, on the one hand, the heat of the water storage unit is used to heat the ambient air entering the system to supplement the air dissipated by the dehumidification fan and avoid the decrease of the air temperature in the system. On the other hand, since the water storage unit and the electric heating unit are relatively independent circulation pipelines, the situation that the electric heating unit outputs heat reversely to the water storage unit at low temperature can be avoided, and the energy utilization efficiency is improved.

[0093] Parts not involved in the present invention are the same as or can be implemented by the prior art.

Claims

1. A solar hot air combined drying device, characterized in that, It includes a heat collection unit, a water storage unit, a drying unit, and an electric heating unit; The heat collection unit includes a heat collection barrel; the heat collection barrel is connected to a solar heat collecting tube and can heat the air passing through the heat collection barrel; The water storage unit includes a water storage barrel and a heat exchanger; there is water stored in the water storage barrel; the heat exchanger is a water-air heat exchanger, which is arranged in the water storage barrel and immersed in water; The electric heating unit includes a heating pipe; an electric heater is arranged in the heating pipe, which can heat the air in the heating pipe; The drying unit includes a drying chamber; the drying chamber is box-shaped and can introduce hot air to dry the items stored therein; a moisture exhaust air vent is arranged on the side wall of the drying chamber; The air inlet of the heat collection barrel is connected to the air outlet of the drying unit through Pipeline I, and its air outlet is connected to the inlet of the heating pipe through Pipeline II; the outlet of the heating pipe is connected to the air inlet of the drying unit through Pipeline III; the air inlet and air outlet of the heat exchanger are respectively connected to Pipeline II through Pipeline IV and Pipeline V, and controlled control valves I and II are respectively arranged at the connection points; the control valve II is located between the control valve I and the inlet of the heating pipe; it also includes Pipeline VI, one end of which is connected to Pipeline I and a controlled control valve III is arranged at the connection point, and the other end is connected to the control valve I; A circulation fan is arranged at the air outlet of the drying unit; Temperature sensors are respectively arranged in the heat collection barrel, at the air outlet of the heat exchanger, and in the drying unit; the temperature sensors are respectively electrically connected to a controller; A blind pipe I is arranged at the air inlet of the heat collection barrel; a blind pipe II is arranged at the air inlet of the heat exchanger; a blind pipe III is arranged on Pipeline VI; the blind pipe I, blind pipe II, and blind pipe III are all connected to the outside and can be controlled to open and close; The water storage barrel is vertically cylindrical, with a water inlet at its upper part, a drain outlet at its lower part, and a heat insulation layer on its outside; the water inlet is connected to a water storage barrel; the drain outlet is controlled; The solar hot air combined drying device can operate the following four closed air circulation circuits: 1) Adjust the control valves I, II, and III to make Pipeline I and Pipeline II communicate; then, open the blind pipe I for a certain period of time, so that the external air is heated by the solar heat collecting tube, and then enters the drying chamber through Pipeline II and Pipeline III to dry the materials therein; then, it flows back to the heat collection barrel through Pipeline I and circulates; 2) Adjust the control valves I, II, and III to make Pipeline I and Pipeline II communicate, and make a part of Pipeline IV communicate, and Pipeline V communicate with Pipeline II; then, open the blind pipe I for a certain period of time, so that the external air is heated by the solar heat collecting tube, and then flows through Pipeline II to the electric heating pipe, and a part of the hot air therein flows through Pipeline IV into the heat exchanger to exchange heat with the water in the water storage barrel to reduce the temperature, and then flows back to Pipeline II through Pipeline V to merge with the original air, and after its temperature is reduced, it enters the drying chamber to dry the materials therein; then, it flows back to the heat collection barrel through Pipeline I and circulates; 3) Adjust control valve I, control valve II, and control valve III to make pipeline I communicate with pipeline IV through pipeline VI; at the same time, make pipeline V communicate with pipeline II; then, open blind pipe II for a certain period of time to allow external air to enter the heat exchanger, exchange heat with the water in the water storage bucket, increase in temperature, and then enter the drying chamber through pipeline V, pipeline II, and pipeline III to dry the materials therein. Then, it flows back to the heat exchanger through pipeline I, pipeline VI, and pipeline IV to form a circulating operation. 4) Adjust control valve I, control valve II, and control valve III to make pipeline I communicate with pipeline II through pipeline VI; then, start the circulating fan and open blind pipe III for a certain period of time to allow external air to enter the heating pipe in sequence through pipeline VI and pipeline II, and then enter the drying chamber through pipeline III after being heated by the electric heater to dry the materials therein; then, it flows out of the drying chamber and flows back into pipeline VI through pipeline I to form a cycle.

2. The solar hot air combined drying device according to claim 1, characterized in that, The heat collection units are multiple groups and are connected in series with each other.

3. The solar hot air combined drying device according to claim 1, characterized in that, The heat exchanger is made of closely arranged "Z"-shaped copper tubes and is uniformly arranged along the bottom and around the water storage bucket.

4. The solar hot air combined drying device according to claim 1, characterized in that, Inside the drying chamber, symmetric limiting plates are longitudinally arranged; limiting grooves are respectively arranged on the side walls of the two limiting plates; movable material drying support trays are horizontally and symmetrically arranged inside the two limiting plates; two humidity and temperature sensors at different heights are arranged on the material drying support tray; the humidity and temperature sensors are electrically connected to the controller; a moisture exhaust fan is arranged on the moisture exhaust air outlet.

5. A control method for a solar hot air combined drying device according to any one of claims 1-4, characterized in that, It includes the following steps: Step 1: Before the drying device starts to operate, set the maximum drying temperature max(t) and the minimum drying temperature min(t) according to the characteristics of the materials to be dried. Step 2: Read the current value s(t) of the temperature of the heat collection unit and the current value q(t) of the temperature of the water storage unit. Step 3: Calculate the following values: (1) Calculate the maximum difference amount e(t) of the heat collection unit, and the calculation formula is: e(t)=max(t)-s(t); (2) Calculate the minimum difference amount d(t) of the heat collection unit, and the calculation formula is: d(t)=s(t)-min(t); (3) Calculate the maximum difference amount k(t) of the water storage unit, and the calculation formula is: k(t)=max(t)-q(t); (4) Calculate the minimum difference amount f(t) of the water storage unit, and the calculation formula is: f(t)=q(t)-min(t); Step 4: Run the drying program according to the following conditions: (1) If e(t)<0, execute the second case of the independent drying mode of the heat collection unit; (2) If e(t)>0 and d(t)>0, execute the first case of the independent drying mode of the heat collection unit; (3) If e(t)>0 and d(t)<0 and k(t)<0, execute the one-time water transfer from the water storage bucket to the water storage unit; (4) If e(t)>0 and d(t)<0 and k(t)>0 and f(t)>0, execute the independent drying mode of the water storage unit; (5) If e(t)>0 and d(t)<0 and k(t)>0 and f(t)<0, execute the independent drying mode of the electric heating unit; Step 5: Detect the water content of the material. If it is greater than the set target moisture content, continue drying; if it is less than the set target moisture content, end the drying.

6. The control method of the solar hot air combined drying device according to claim 5, characterized in that, The first case of the independent drying mode of the heat collection unit in Step 4 is as follows: Adjust the control valve I, control valve II, and control valve III to make the pipeline I and pipeline II unobstructed; then, open the port of the blind pipe I for several minutes and then close it. External air enters the heat collection barrel, is heated by the solar heat collection pipe, and then enters the drying chamber through pipeline II and pipeline III to dry the material therein. Then, it flows back to the heat collection barrel through pipeline I and operates in a cycle; during this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan, and at the same time open the port of the blind pipe I to discharge part of the air in the drying chamber and supplement external air; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of the blind pipe I at the same time.

7. The control method of the solar hot air combined drying device according to claim 5, characterized in that, The second case of the independent drying mode of the heat collection unit in Step 4 is as follows: Adjust the control valve I, control valve II, and control valve III to make the pipeline I and pipeline II unobstructed, make part of the pipeline IV unobstructed, and pipeline V communicate with pipeline II; then, open the port of the blind pipe I for several minutes and then close it. At the same time, external air enters the heat collection barrel, is heated by the solar heat collection pipe, and part of it flows into the heat exchanger through pipeline IV and exchanges heat with the water in the water storage bucket to reduce the temperature, and then flows back to pipeline II through pipeline V, merges with the original air, and enters the drying chamber after the temperature is reduced to dry the material therein. Then, it flows back to the heat collection barrel through pipeline I and operates in a cycle; during this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of the blind pipe I to supplement external air to the circulation pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of the blind pipe I at the same time.

8. The control method of the solar hot air combined drying device according to claim 5, characterized in that The independent drying mode of the water storage unit in Step 4 is as follows: Adjust the control valve I, control valve II, and control valve III to make pipeline I communicate with pipeline IV through pipeline VI; at the same time, pipeline V communicates with pipeline II; then, open the port of the blind pipe II for several minutes and then close it. External air enters the heat exchanger, exchanges heat with the water in the water storage bucket and the temperature rises, and then enters the drying chamber through pipeline V, pipeline II, and pipeline III to dry the material therein. Finally, it flows back to the heat exchanger through pipeline I, pipeline VI, and pipeline IV to form a cycle operation; during this period, detect the air humidity in the drying chamber; if the air humidity exceeds the set value, turn on the dehumidification fan to discharge the wet air in the drying chamber, and at the same time open the port of the blind pipe II to supplement external air to the circulation pipeline; continue to detect the air humidity in the drying chamber; when the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of the blind pipe II at the same time.

9. The control method of the solar hot air combined drying device according to claim 5, characterized in that, The independent drying mode of the electric heating unit in Step 4 is as follows: Adjust Control Valve I, Control Valve II, and Control Valve III to make Pipeline I communicate with Pipeline II after passing through Pipeline VI. Then, turn on the circulation fan, open the port of Blind Tube III for several minutes and then close it. External air enters Pipeline VI, then enters the heating tube through Pipeline II, is heated by the electric heater, enters the drying chamber through Pipeline III, and dries the materials therein. Then, it flows out of the drying chamber, flows into Pipeline VI again after passing through Pipeline I, forming a cycle. During this period, detect the air humidity in the drying chamber. If the air humidity exceeds the set value, turn on the dehumidification fan to discharge the humid air in the drying chamber. At the same time, open the port of Blind Tube III to supplement external air to the circulation pipeline. Continue to detect the air humidity in the drying chamber. When the air humidity in the drying chamber is lower than the set value, turn off the exhaust fan and the port of Blind Tube III at the same time.

Images