A Composition Method of an Agricultural Greenhouse Heat Dissipation System

Abstract

The present invention relates to the technical field of heating, ventilation and air conditioning, and specifically to a composition method of a heat dissipation system for an agricultural greenhouse. The heat dissipation system includes four types of heat dissipation devices: side wall heat dissipation devices, transmission track heat dissipation devices, air handling unit heat dissipation devices, and floor heating heat dissipation devices between crops. The side wall heat dissipation devices and the transmission track heat dissipation devices are directly connected in series to form a first-stage high-temperature heat dissipation subsystem. The air handling unit heat dissipation devices and the floor heating heat dissipation devices between crops are directly connected in series to form a second-stage low-temperature heat dissipation subsystem. The first-stage high-temperature heat dissipation subsystem and the second-stage low-temperature heat dissipation subsystem are connected in series through an intermediate buffer balance tank. In the composition method of this agricultural greenhouse heat dissipation system, by connecting the four types of heat dissipation devices in series at multiple levels, the temperature of the heating medium of the four types of heat dissipation devices shows a gradient decrease. The heat dissipation devices with different temperatures are arranged in different areas of the agricultural greenhouse, which improves the initial temperature of the heating medium, reduces the return water temperature of the heating medium, and reduces the number of heat dissipation devices.

Description

Technical Field

[0001] The present invention relates to the technical field of heating, ventilation and air conditioning (HVAC), and more particularly to a method for constructing a heat dissipation system for an agricultural greenhouse. Background Art

[0002] As an important symbol of modern agriculture, agricultural greenhouses have achieved remarkable development in recent years.

[0003] An agricultural greenhouse, as a type of agricultural greenhouse, refers to a modern intelligent agricultural greenhouse with a steel structure framework and a glass roof for daylighting. An agricultural greenhouse is a closed intelligent system that provides a stable, independent local microclimate environment for crops, free from the influence of the external environment.

[0004] To achieve the above goals, a closed agricultural greenhouse requires precise temperature control to ensure that the crop roots obtain a stable, comfortable growth environment to promote the efficient growth of crops.

[0005] Therefore, all agricultural greenhouses need to be equipped with a heating system. As a subsystem of the heating system, the heat dissipation system has its own particularities different from those of ordinary buildings:

[0006] (1) In an agricultural greenhouse, crops are planted over a large area. If there is a high-temperature heat source around the crops, the heat radiation generated by the high-temperature heat source is not conducive to the growth of crops. Therefore, the temperature of the heating medium in the heat dissipation equipment close to the crops should not be too high.

[0007] (2) To fully utilize the environmental conditions for the efficient growth of crops in an agricultural greenhouse, high-value economic crops are usually planted in agricultural greenhouses. The personnel in the agricultural greenhouse operate frequently. If the temperature of the heating medium in the heat dissipation equipment is too high, it will pose a risk of scalding to the operators.

[0008] (3) In an agricultural greenhouse, crops are planted over a large area. A large number of heat dissipation devices can be installed in the upper space of the crops. In order to direct the hot air exchanged by the heat dissipation devices in the upper space of the crops to the ground, forced ventilation must be used. However, the exchanged hot air is characterized by high temperature and low relative humidity. Blowing this dry hot air on the surface of the crops may cause leaf dehydration.

[0009] (4) A large number of floor heating heat dissipation devices can also be installed in the gaps between crops in an agricultural greenhouse. However, since these floor heating heat dissipation devices are close to the crops, the surface temperature of their heat exchanger interfaces must be strictly controlled.

[0010] (5) The roof of an agricultural greenhouse adopts a glass structure with a steel structure framework, making it difficult to insulate the roof. Therefore, the heat dissipation is large and the heating demand is high.

[0011] For the above reasons, it is very difficult to configure the heat dissipation system for an agricultural greenhouse.

[0012] The calculation formula for the heat dissipation capacity of the heat dissipation device is as follows: Q = KSΔT (1)

[0013] In the formula: Q: The heat dissipation power of the heat dissipation device, unit: KW

[0014] K: The heat transfer constant of the heat dissipation device, unit: KW / (m2·K)

[0015] S: The area of the heat dissipation interface of the heat dissipation device, unit: m2

[0016] ΔT: The temperature difference between the heat transfer media on both sides of the heat dissipation interface of the heat dissipation device, unit: K

[0017] As the heat transfer constant of the heat dissipation device, the value of K primarily depends on the medium state (liquid phase or gas phase), the medium flow mode, and the medium flow velocity of the heat transfer media on both sides of the heat dissipation interface of the heat dissipation device. Secondly, it depends on the material and thickness of the heat dissipation interface of the heat dissipation device.

[0018] The special structure of the agricultural greenhouse determines its characteristics of large heat dissipation and high heat supply demand. The heat supply index of the agricultural greenhouse is 5 to 10 times that of ordinary industrial and civil buildings.

[0019] To achieve high-power heat supply, according to formula (1), by increasing the temperature difference between the heat transfer media on both sides of the heat dissipation interface of the heat dissipation device, the heat dissipation area S can be reduced, thereby reducing the number of heat dissipation devices, which is a priority consideration for high-power heat supply. Increasing the temperature difference between the heat transfer media on both sides of the heat dissipation interface of the heat dissipation device, under the condition that the ambient temperature is determined on the outer side of the heat dissipation interface of the heat dissipation device, it is necessary to increase the temperature of the heat supply medium inside the heat dissipation device. However, the heat radiation generated by the aforementioned heat dissipation device as a high-temperature heat source is not conducive to crop growth and is also prone to the danger of scalding operators, which restricts the use of high-temperature heat supply media.

[0020] In the agricultural greenhouse, personnel operate frequently. The design temperature of the heat supply medium should be based on the safety limit that the surface temperature of the heat dissipation device in the space where contact occurs with the operator does not cause scalding to personnel. According to the temperature requirement that the human body surface skin does not get scalded during instant contact (within one minute), the surface temperature of the heat dissipation device in the space where contact occurs with the operator cannot exceed 60°C. Then, the inner side of the heat dissipation interface of the heat dissipation device, that is, the inlet temperature of the heat transfer medium input into the heat dissipation device cannot be higher than 70°C.

[0021] Taking forced ventilation measures on the surface of the heat dissipation device can greatly increase the value of K, thereby improving the heat transfer efficiency of the heat dissipation device and reducing the number of heat dissipation devices. However, the hot air discharged by forced ventilation heat transfer blows directly on the surface of the crops, and the high-temperature hot air will dehydrate the surface of the crops, seriously affecting crop growth. Therefore, the hot air discharged by forced ventilation heat transfer cannot exceed 35°C. Correspondingly, the average surface temperature of the heat dissipation device cannot exceed 50°C. Then, the inner side of the heat dissipation interface of the heat dissipation device, that is, the inlet temperature of the heat transfer medium input into the heat dissipation device cannot be higher than 55°C.

[0022] If the heat dissipation device adopts a floor heating heat dissipation device arranged between crops, the distance between the heat dissipation device and the crops is very close. Then, the average temperature on the surface of the heat dissipation device must be very low, usually not exceeding 40°C. Therefore, the temperature at the inner side of the heat dissipation interface of the heat dissipation device, that is, the inlet temperature of the heat exchange medium input into the heat dissipation device, cannot be higher than 45°C.

[0023] It can be seen that due to the particularity of the agricultural greenhouse, the surface temperature of the heat dissipation device for heating the agricultural greenhouse is restricted, the temperature difference between the heat exchange media on both sides of the heat dissipation interface of the heat dissipation device cannot be effectively increased, resulting in an increase in heat exchange devices, difficulty in the spatial layout of heat exchange devices, and the inevitable occupation of the crop growth space, an increase in equipment investment, and a reduction in the economic benefits of the agricultural greenhouse. Summary of the Invention

[0024] The purpose of the present invention is to provide a composition method for an agricultural greenhouse heat dissipation system to solve the problems in the above-mentioned background technology, that is, due to the particularity of the agricultural greenhouse, the surface temperature of the heat dissipation device for heating the agricultural greenhouse is restricted, the temperature difference between the heat exchange media on both sides of the heat dissipation interface of the heat dissipation device cannot be effectively increased, resulting in an increase in heat exchange devices, difficulty in the spatial layout of heat exchange devices, the inevitable occupation of the crop growth space, an increase in equipment investment, and a reduction in the economic benefits of the agricultural greenhouse.

[0025] To achieve the above purpose, the present invention provides a composition method for an agricultural greenhouse heat dissipation system, including a heat dissipation system. The heat dissipation system is composed of four types of heat dissipation devices: side wall heat dissipation devices, transmission track heat dissipation devices, air disc heat dissipation devices, and floor heating heat dissipation devices between crops. The side wall heat dissipation device and the transmission track heat dissipation device are directly connected in series to form a first-stage high-temperature heat dissipation subsystem. The air disc heat dissipation device and the floor heating heat dissipation device between crops are directly connected in series to form a second-stage low-temperature heat dissipation subsystem. The first-stage high-temperature heat dissipation subsystem and the second-stage low-temperature heat dissipation subsystem are connected in series through an intermediate buffer balance tank. The specific steps are as follows:

[0026] S1. The highest inlet temperature of the second group of heat dissipation devices in the first-stage high-temperature heat dissipation subsystem, that is, the transmission track heat dissipation device, is set to ≤70°C, that is, the highest outlet temperature of the first group of heat dissipation devices in the first-stage high-temperature heat dissipation subsystem, that is, the side wall heat dissipation device, is ≤70°C;

[0027] S2. Determine the outlet temperature T2 of the heat supply medium of the side wall heat dissipation device according to the requirements of the planting process. According to the structural characteristics of the agricultural greenhouse and the requirements of the planting process, determine the initial temperature T1 of the heat supply medium that can be received. The range of T1 is 70°C - 75°C;

[0028] S3. Set the inlet temperature T2 and the outlet temperature T3 of the heat transfer medium of the transmission track heat dissipation device according to the crop planting conditions, obtain the heat transfer temperature difference of the heat supply medium, ΔT = T2 - T3, and calculate the heat transfer amount that the transmission track heat dissipation device can complete;

[0029] S4. Redistribute and calculate the configuration of other heat exchange devices.

[0030] As a preferred solution of the present invention, in step S2, according to the heat dissipation power Q1 that the side wall heat dissipation device needs to complete, the inlet temperature of the heat supply medium of the side wall heat dissipation device, that is, the initial temperature T1 of the heat supply medium that can be received, is calculated according to the formula Q1 = Kq(T1 - T2), where:

[0031] Q1: The heat dissipation power of the side wall heat dissipation device, unit: KW;

[0032] K: The specific heat capacity of the heat supply medium of the side wall heat dissipation device, unit: Kj / (Kg·K);

[0033] q: The flow rate of the heat supply medium entering the side wall heat dissipation device, unit: Kg / s;

[0034] T1: The temperature of the heat supply medium entering the side wall heat dissipation device, unit: K;

[0035] T2: The temperature of the heat supply medium flowing out of the side wall heat dissipation device, unit: K.

[0036] As a preferred solution of the present invention, in step S2, the heat transfer amount that the transmission track heat dissipation device can complete is calculated according to the formula Q2 = Kq(T2 - T3), where:

[0037] Q2: The heat dissipation power of the transmission track heat dissipation device, unit: KW;

[0038] K: The specific heat capacity of the heat supply medium of the transmission track heat dissipation device, unit: Kj / (Kg·K);

[0039] q: The set flow rate of the heat supply medium entering the transmission track heat dissipation device, unit: Kg / s;

[0040] T2: The temperature of the heat supply medium entering the transmission track heat dissipation device, T2 ≤ 70°C;

[0041] T3: The temperature of the heat supply medium flowing out of the transmission track heat dissipation device, T3 ≤ 55°C.

[0042] As a preferred solution of the present invention, the parallel combination of several of the side wall heat dissipation devices and the parallel combination of several of the transmission track heat dissipation devices are directly connected in series; the parallel combination of several of the side wall heat dissipation devices and the parallel combination of several of the transmission track heat dissipation devices are directly connected in series.

[0043] As a preferred embodiment of the present invention, the number of monomers in the parallel combination of the side wall heat dissipation devices is reasonably combined according to the structural characteristics of the agricultural greenhouse, the distribution mode of the side wall heat dissipation devices, as well as the pipe network diameter and flow velocity conditions. The number of monomers in the parallel combination of the transmission track heat dissipation devices is matched and combined according to the number of monomers in the parallel combination of the transmission track heat dissipation devices.

[0044] As a preferred embodiment of the present invention, the side wall heat dissipation devices are arranged away from the personnel operation area and the crop planting area, close to the gable walls around the agricultural greenhouse, and large-diameter hot-dip galvanized steel pipes with low flow resistance are used as the heat dissipation devices. The diameter of the hot-dip galvanized steel pipes is greater than 50 mm, and the inlet temperature of the heat exchange medium is higher than 70 °C.

[0045] As a preferred embodiment of the present invention, the transmission track heat dissipation devices also use the transportation track and overhead support in the agricultural greenhouse, and medium and small-diameter hot-dip galvanized steel pipes are used. The diameter of the hot-dip galvanized steel pipes is less than 40 mm, and the inlet temperature of the heat exchange medium is controlled to be lower than 70 °C.

[0046] As a preferred embodiment of the present invention, the air disc heat dissipation devices adopt forced ventilation copper tube aluminum fin heat dissipation devices. The air disc heat dissipation devices are suspended or supported by brackets in the space 0.5 to 2 meters above the ground in the greenhouse, and the inlet temperature of the heat exchange medium is controlled to be lower than 55 °C, and the hot air temperature discharged by heat exchange is lower than 35 °C.

[0047] As a preferred embodiment of the present invention, the floor heating heat dissipation devices between crops adopt small-diameter hot-dip galvanized steel pipes. The diameter of the hot-dip galvanized steel pipes is less than 32 mm, and they are evenly distributed between crops, and the inlet temperature of the heat exchange medium is controlled to be lower than 45 °C.

[0048] As a preferred embodiment of the present invention, the intermediate buffer balance tank is an open system communicating with the atmosphere, and the maximum designed buffer volume is the flow rate for 10 - 30 minutes.

[0049] Compared with the prior art, the beneficial effects of the present invention are:

[0050] In the method for constructing the heat dissipation system of the agricultural greenhouse, by connecting four types of heat dissipation devices in multiple stages in series, the temperature of the heating medium (hot water) of the four types of heat dissipation devices shows a gradient decrease. The heat dissipation devices with different temperatures are arranged in different areas of the agricultural greenhouse, which improves the initial temperature of the heating medium (hot water), reduces the return water temperature of the heating medium (hot water), reduces the number of heat dissipation devices, realizes large temperature difference heat dissipation of the heating medium (hot water), reduces the circulation flow rate of the heating medium (hot water), thereby reducing the operating energy consumption, and provides a basis for the high-efficiency operation of the heating system. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the heating medium flow of the heat dissipation process of the present invention;

[0052] Figure 2 Schematic diagram of the heat dissipation device layout of the present invention.

[0053] The meanings of each label in the figure are as follows:

[0054] 1. Side wall heat dissipation device; 2. Transmission track heat dissipation device; 3. Air handling unit heat dissipation device; 4. Floor heating heat dissipation device between crops; 5. Intermediate buffer balance tank. Specific implementation manner

[0055] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] The present invention provides a method for constructing an agricultural greenhouse heat dissipation system, as Figure 1 - Figure 2 shown, including a heat dissipation system, characterized in that: the heat dissipation system is composed of four types of heat dissipation devices, namely a side wall heat dissipation device 1, a transmission track heat dissipation device 2, an air handling unit heat dissipation device 3, and a floor heating heat dissipation device 4 between crops. The side wall heat dissipation device 1 and the transmission track heat dissipation device 2 are directly connected in series to form a first-stage high-temperature heat dissipation subsystem. The heat exchange temperature difference between the heat exchange medium of this system and the ambient air is large, and the ambient air adopts the natural convection method. Therefore, the K value (equipment heat exchange constant of the heat dissipation device) of the heat exchange equipment in the first-stage high-temperature heat dissipation subsystem is relatively low, usually 10 - 15 W / m2•K. The temperature rise of the ambient air through the heat exchange interface is about 10 °C. The first-stage high-temperature heat dissipation subsystem uses large-diameter steel pipes as heat dissipation devices, with small fluid frictional resistance along the way, and the fluid runs smoothly after cascading. However, the pipe diameter of the second-stage low-temperature heat dissipation subsystem as a heat dissipation device is small, and the fluid frictional resistance along the way is large. Therefore, an open intermediate buffer balance tank 5 is provided between the first stage and the second stage, and the flow between the two is blocked and does not affect each other. The air handling unit heat dissipation device 3 and the floor heating heat dissipation device 4 between crops are directly connected in series to form a second-stage low-temperature heat dissipation subsystem. The first-stage high-temperature heat dissipation subsystem and the second-stage low-temperature heat dissipation subsystem are connected in series through the intermediate buffer balance tank 5. A transfer pump is provided to extract the heat exchange medium from the open intermediate buffer balance tank 5 and pressurize and transport it to the second stage. The buffer capacity (i.e., the effective volume) of the open intermediate buffer balance tank 5 meets the flow rate of the maximum design flow rate for 10 - 30 minutes, preferably 20 minutes. The specific steps are as follows:

[0057] S1. The highest inlet temperature of the second group of heat dissipation devices in the first-stage high-temperature heat dissipation subsystem, that is, the transmission track heat dissipation device 2, is set to ≤ 70 °C, that is, the highest outlet temperature of the first group of heat dissipation devices in the first-stage high-temperature heat dissipation subsystem, that is, the side wall heat dissipation device 1, is ≤ 70 °C;

[0058] S2. Determine the outlet temperature T2 of the heat supply medium of the side wall heat dissipation device 1 according to the requirements of the planting process. According to the structural characteristics of the agricultural greenhouse and the requirements of the planting process, determine the initial temperature T1 of the heat supply medium that can be received, and the range of T1 is 70°C - 75°C;

[0059] S3. Set the inlet temperature T2 and outlet temperature T3 of the heat exchange medium of the transmission track heat dissipation device 2 according to the crop planting conditions, obtain the heat exchange temperature difference of the heat supply medium, ΔT = (T2 - T3), and calculate the heat exchange amount that the transmission track heat dissipation device can complete;

[0060] S4. Redistribute and calculate the configuration of other heat exchange devices.

[0061] In this embodiment, in step S2, according to the heat dissipation power Q1 that the side wall heat dissipation device 1 needs to complete, calculate the inlet temperature of the heat supply medium of the side wall heat dissipation device 1, that is, the initial temperature T1 of the heat supply medium that can be received, according to the formula Q1 = Kq(T1 - T2). In the formula:

[0062] Q1: The heat dissipation power of the side wall heat dissipation device 1, unit: KW;

[0063] K: The specific heat capacity of the heat supply medium of the side wall heat dissipation device 1, unit: Kj / (Kg·K);

[0064] q: The flow rate of the heat supply medium entering the side wall heat dissipation device 1, unit: Kg / s;

[0065] T1: The temperature of the heat supply medium entering the side wall heat dissipation device 1, unit: K;

[0066] T2: The temperature of the heat supply medium flowing out of the side wall heat dissipation device 1, unit: K.

[0067] Specifically, in step S2, calculate the heat exchange amount that the transmission track heat dissipation device can complete according to the formula Q2 = Kq(T2 - T3). In the formula:

[0068] Q2: The heat dissipation power of the transmission track heat dissipation device 2, unit: KW;

[0069] K: The specific heat capacity of the heat supply medium of the transmission track heat dissipation device 2, unit: Kj / (Kg·K);

[0070] q: The set flow rate of the heat supply medium entering the transmission track heat dissipation device 2, unit: Kg / s;

[0071] T2: The temperature of the heat supply medium entering the transmission track heat dissipation device 2, T2 ≤ 70°C;

[0072] T3: The temperature of the heat supply medium flowing out of the transmission track heat dissipation device 2, T3 ≤ 55°C.

[0073] Further, the parallel combination of several side wall heat dissipation devices 1 and the parallel combination of several transmission track heat dissipation devices 2 are directly connected in series; the parallel combination of several side wall heat dissipation devices 1 and the parallel combination of several transmission track heat dissipation devices 2 are directly connected in series.

[0074] Further, the number of monomers in the parallel combination of side wall heat dissipation devices 1 is reasonably combined according to the structural characteristics of the agricultural greenhouse, the distribution method of side wall heat dissipation devices 1, as well as the pipe network diameter and flow velocity conditions. The number of parallel combinations of transmission track heat dissipation devices 2 is matched and combined according to the number of monomers in the parallel combination of transmission track heat dissipation devices 2.

[0075] Further, the side wall heat dissipation devices 1 are arranged away from the personnel operation area and the crop planting area, close to the gable walls around the agricultural greenhouse, and large-diameter hot-dip galvanized steel pipes with low flow resistance are used as heat dissipation devices. The diameter of the hot-dip galvanized steel pipe is greater than 50 mm, and the inlet temperature of the heat exchange medium is higher than 70 °C.

[0076] Further, the transmission track heat dissipation devices 2 also serve as the transportation tracks and overhead supports in the agricultural greenhouse, and medium and small-diameter hot-dip galvanized steel pipes are used. The diameter of the hot-dip galvanized steel pipe is less than 40 mm, and the inlet temperature of the heat exchange medium is controlled to be lower than 70 °C.

[0077] Further, the water inlet of the air handling unit heat dissipation device 3 is the return water of the first-stage heat dissipation system. The return water temperature T3 of the first-stage heat dissipation system is lower than 55°C, which is the water inlet temperature of the air handling unit heat dissipation device 3. To ensure the low-temperature heat exchange requirements of the second group of heat exchange devices in the second stage, namely the floor heating heat dissipation device 4 in the crop area, the return water temperature T4 of the air handling unit heat dissipation device 3 is controlled between 40°C and 45°C. The air handling unit heat dissipation device 3 adopts a forced ventilation copper tube-aluminum fin heat dissipation device, controlling the inlet temperature of the heat exchange medium to be lower than 55°C, and the hot air temperature discharged from the heat exchange to be lower than 35°C. The addition of aluminum fins greatly increases the heat exchange area, and the aluminum fin area is approximately 20 times that of the copper tube surface area; forced ventilation increases the air passing speed at the heat exchange interface, improves the air passing volume. Usually, the air passing speed at the heat exchange interface is between 1.5 m / s and 9.5 m / s, and the specific wind speed depends on the environmental requirements for wind noise and the blowing effect on the crop surface. High wind speed also increases the K value of the heat exchange device, usually between 30 and 100 W / m2•K, which is 3 to 10 times the K value in the natural ventilation state; the air handling unit heat dissipation device has a high K value, a large heat exchange area, and a large environmental air passing volume. The temperature rise of the air passing through the heat exchanger is approximately between 5°C and 15°C. Controlling the outlet air temperature of the air handling unit heat dissipation device to be lower than 35°C keeps the impact on the plant leaf surface within the allowable range. The air handling unit heat dissipation device 3 is suspended or supported by brackets in the space 0.5 to 2 meters above the ground in the greenhouse. If the height of the device outlet is level with the plants, adjust the air outlet direction upward to avoid directly blowing on the plant leaf surface. If the height of the device outlet is higher than the plants, adjust the air outlet direction downward to avoid the hot air floating upward, reducing the ground heat exchange function and increasing the heat exchange loss of the agricultural greenhouse roof.

[0078] Further, the floor heating heat dissipation device 4 in the crop area adopts small-diameter hot-dip galvanized steel pipes with a diameter less than 32 mm, evenly distributed in the crop area, controlling the inlet temperature of the heat exchange medium to be lower than 45°C. The floor heating heat dissipation device 4 in the crop area is connected in series with the air handling unit heat dissipation device 3 as the fluid connection device in the subsequent stage, and its flow resistance should be greater than or equal to that of the previous-stage device; specifically, after several air handling unit heat dissipation devices 3 are combined in parallel, the total cross-sectional area of the parallel copper tubes should be greater than the total cross-sectional area of the parallel steel pipes after several floor heating heat dissipation devices 4 in the crop area are combined in parallel. The return water of the floor heating heat dissipation device 4 in the crop area returns to the heating system, and the return temperature T5 is controlled between 35°C and 40°C.

[0079] Further, the intermediate buffer balance tank 5 is an open system communicating with the atmosphere, and the maximum designed buffer volume is the flow volume for 10 - 30 minutes.

[0080] Further, the whole system realizes large-temperature-difference heat exchange from the inlet water temperature of 70°C - 75°C to the return water temperature of 35°C - 40°C, reducing the circulation flow rate of the heating medium (hot water), thereby reducing the operating energy consumption and providing a basis for the high-efficiency operation of the heating system.

[0081] As attachedFigure 1 As shown in the schematic diagram of the heat supply medium flow of the heat dissipation process, the heat supply pipe of the heat supply system is connected in parallel with several side wall heat dissipation devices 1. The side wall heat dissipation devices 1 adopt a pipe arrangement structure, and the pipe diameter of the pipes is greater than 50 mm; the side wall heat dissipation devices 1 are the first group of heat dissipation devices at the first stage, and the initial high-temperature hot water temperature input can reach 70 - 75 °C.

[0082] As attached Figure 2 As shown in the schematic diagram of the heat dissipation device layout, the side wall heat dissipation devices 1 are close to the side walls surrounding the agricultural greenhouse and far from the plant planting area, and do not belong to the personnel operation area. The heat radiation generated by the initial high-temperature hot water at 70 - 75 °C has a controllable impact on the plant planting area, and it is not easy for personnel to be scalded far from the personnel operation area.

[0083] As attached Figure 1 As shown in the schematic diagram of the heat supply medium flow of the heat dissipation process, the return water after the side wall heat dissipation devices 1 dissipate heat enters the supply and return water distributor. The supply and return water distributor is also the water inlet mechanism for the next group of heat exchange device transmission track heat dissipation devices 2. The supply and return water distributor is connected in parallel with several transmission track heat dissipation devices 2. The transmission track heat dissipation devices 2 also serve as the transportation track and overhead support in the agricultural greenhouse. These heat dissipation devices are determined by the structural characteristics of the agricultural greenhouse and the requirements of the planting process, that is, the heat dissipation area of this type of heat dissipation device is determined by the planting process rather than the heat dissipation requirement; each single body of the transmission track heat dissipation device 2 is a single-pipe steel pipe serving as the transportation track and overhead support; the hot water input into the transmission track heat dissipation device 2 is the return water of the side wall heat dissipation device, and the water temperature is controlled below 70 °C.

[0084] As attached Figure 2 As shown in the schematic diagram of the heat dissipation device layout, the transmission track heat dissipation devices 2 are arranged on the ground of the personnel operation passage between the plant planting areas, which is an area where personnel operate frequently. The inlet water temperature is controlled below 70 °C. Even if the bare skin of the human body directly touches it, the contact time that can cause scalding can be greater than 1 minute. Therefore, this temperature setting is safe for the operators; the transmission track heat dissipation devices 2 are arranged far from the plant planting area and are single-pipe steel pipes. The heat dissipation power in the arranged area is small, and the output heat energy is low. Although the surface temperature of the single-pipe steel pipe is relatively high, the heat energy radiated and diffused to the plant planting area has little direct impact on the crops.

[0085] As attached Figure 1 As shown in the schematic diagram of the heat supply medium flow of the heat dissipation process, the return water generated from the transmission track heat dissipation devices 2 directly flows back to the open intermediate buffer balance tank 5 connected to the atmosphere. In this way, the heat dissipation system composed of two groups of heat exchange devices in series is fluidly separated from the next-level heat dissipation system and does not affect each other.

[0086] The buffer capacity (i.e., the effective volume) of the open intermediate buffer balance tank 5 meets the flow rate of the maximum design flow rate for 10 - 30 minutes, preferably 20 minutes.

[0087] As shown in Figure 1 the schematic diagram of the heat supply medium flow of the heat dissipation process, the transfer pump extracts the heat exchange medium from the open intermediate buffer balance tank 5 and conveys it to the second stage for pressurized transmission. The first group of heat exchange equipment in the second stage is the air disc heat dissipation equipment 3; the heat supply pipe of the second-stage heat supply system is connected in parallel with a number of air disc heat dissipation equipment 3. The hot water input into the air disc heat dissipation equipment 3 is the return water of the transmission track heat dissipation equipment, and the water temperature is controlled below 55°C.

[0088] As shown in Figure 2 the schematic diagram of the heat dissipation equipment layout, the air disc heat dissipation equipment 3 is suspended or supported by brackets in the space 0.5 meters to 2 meters above the ground in the greenhouse. The air disc heat dissipation equipment 3 can be arranged in the upper space of the crops in the plant planting area or at the edge of the plant planting area. The inlet water temperature of the air disc heat dissipation equipment 3 is below 55°C. The air disc heat dissipation equipment 3 is a forced ventilation high-efficiency heat dissipation equipment. After heat exchange, the temperature of the air forced out of the outlet is below 35°C, which is 10°C - 15°C higher than the ambient temperature. The relative humidity of this hot air is low, and directly blowing on the plant leaves is likely to cause dehydration of the plant leaves. If the height of the equipment outlet is level with the plants, adjust the air outlet direction upward to avoid directly blowing on the plant leaves. If the height of the equipment outlet is higher than the plants, adjust the air outlet direction downward to avoid the hot air floating upward, reducing the ground heat exchange function and increasing the heat exchange loss of the agricultural greenhouse roof. Control the air outlet speed and air volume so that the temperature drop is generated by the mixing of the air on the plant leaves and the ambient air, and the relative humidity is increased to control the impact on the plant leaves within the allowable range.

[0089] As shown in Figure 1 the schematic diagram of the heat supply medium flow of the heat dissipation process, the return water after the air disc heat dissipation equipment 3 dissipates heat enters the supply and return water distributor, which is also the water inlet mechanism of the next group of heat exchange equipment, the under-crop floor heating heat dissipation equipment 4. The supply and return water distributor is connected in parallel with a number of under-crop floor heating heat dissipation equipment 4. The hot water input into the under-crop floor heating heat dissipation equipment 4 is the return water of the air disc heat dissipation equipment, and the water temperature is controlled below 45°C.

[0090] As shown in Figure 2 the schematic diagram of the heat dissipation equipment layout, the second group of heat exchange equipment in the second stage, the under-crop floor heating heat dissipation equipment 4, is distributed in the ground gaps of the crops, that is, the under-crop floor heating heat dissipation equipment 4 is directly arranged in the plant planting area. Although it does not directly contact the crops, the direct distance between the under-crop floor heating heat dissipation equipment 4 and the crops is very close; by controlling the inlet water temperature below 45°C, this low-temperature heat exchange mode can avoid affecting the crops.

[0091] The whole system has achieved large temperature difference heat exchange of the heat supply medium (hot water) from the inlet water temperature of 70°C - 75°C to the return water temperature of 40°C - 45°C, reducing the circulation flow of the heat supply medium (hot water), thereby reducing the operating energy consumption and providing a basis for the high-efficiency operation of the heat supply system.

[0092] Example: For a certain agricultural greenhouse, it is 500 meters in the east-west direction and 200 meters in the north-south direction, with a total area of 100,000 square meters. The designed maximum heating index is 150 W / m², and the maximum heating power is 15,000 KW.

[0093] The composition method of the heat dissipation system for the agricultural greenhouse is as follows:

[0094] Design and calculation of the second group of heat dissipation equipment in the first-stage heat dissipation system, i.e., the heat dissipation equipment 2 for the transmission track

[0095] The single-tube length of the heat dissipation equipment 2 for the transmission track is 720 meters, the number of single tubes is 144, and the calculated total length is 103,680 meters. The single-tube indicators are as follows:

[0096] Name Value Unit Outer diameter of pipe 40 mm Pipe wall 3 mm Inner diameter of pipe 34 mm

[0097] Take the inlet temperature as 70 °C and the outlet temperature as 55 °C, and set the heat exchange medium flow rate to 350 - 400 t / h, then the heat exchange amount is 6400 - 6600 KW.

[0098] Design and calculation of the first group of heat dissipation equipment in the first-stage heat dissipation system, i.e., the heat dissipation equipment 1 for the side wall

[0099] The single-tube length of the heat dissipation equipment 1 for the side wall is 360 meters, the number of single tubes is 60, and the calculated total length is 21,600 meters. The single-tube indicators are as follows:

[0100] Name Value Unit Outer diameter of pipe 50 mm Pipe wall 3 mm Inner diameter of pipe 44 mm

[0101] From (1), the heat exchange medium flow rate is set to 350 - 400 t / h, the inlet temperature is taken as 74 - 75 °C, and from (1), the outlet temperature is set to 70 °C, then calculate the heat exchange amount: 1800 - 2200 KW.

[0102] Design and calculation of the intermediate buffer balance tank 5

[0103] Set the heat exchange medium flow rate to 350 - 400 t / h, and the flow rate in 20 minutes is 120 - 140 t. Design 4 intermediate buffer balance tanks 5 with a capacity of 30 - 40 tons, that is, divide the whole system into four groups in parallel. Each group is composed of 15 side wall heat dissipation equipment 1 in parallel and 36 transmission track heat dissipation equipment 2 in parallel, which are connected in series as a group and respectively connected to an intermediate buffer balance tank 5.

[0104] Design and calculation of the second group of heat dissipation equipment in the second-stage heat dissipation system, i.e., the heat dissipation equipment 4 between crops

[0105] The heat dissipation equipment 4 between crops is distributed in the ground gaps of the crops. Its arrangement quantity and arrangement interval depend on the crop planting method. Set the single-tube length to 570 meters, the number of single tubes to 300, and the calculated total length to 171,000 meters. The single-tube indicators are as follows:

[0106] Name Value Unit Outer diameter of pipe 32 mm Pipe wall 3 mm Inner diameter of pipe 26 mm

[0107] Set the inlet temperature at 42°C and the outlet temperature at 40°C. Given that the heat exchange medium flow rate is set at 350 - 400 t / h by (1), then the heat transfer amount is 800 - 1000 KW.

[0108] Design and calculation of the first group of heat dissipation equipment in the secondary heat dissipation system, i.e., the air handling unit heat exchange equipment 3

[0109] The total heat transfer amount of the system is 15000 KW. The heat dissipation amount completed by the above three types of heat exchange equipment is 9000 - 9800 KW. The remaining 5200 - 6000 KW needs to be completed by the first group of heat dissipation equipment in the secondary heat dissipation system, i.e., the air handling unit heat exchange equipment.

[0110] Set the inlet temperature of the heating medium (hot water) for the air handling unit heat exchange equipment 3, which is the outlet temperature of the second group of heat dissipation equipment in the primary heat dissipation system, i.e., the transfer track heat dissipation equipment 2. It is set at 55°C by (1). Set the outlet temperature as the inlet temperature of the second group of heat dissipation equipment in the secondary heat dissipation system, i.e., the crop room heat dissipation equipment 4, which is set at 42°C by (4). The heating medium (hot water) flow rate is 350 - 400 t / h. The air handling unit heat exchange equipment 3 is equipped as follows:

[0111] Name Value Unit Single - unit heat transfer area 399 m2 Single - unit windward area 2400*2100 5.04 m2 Designed number of single units 24 Designed inlet air temperature 15 ℃ Designed outlet air temperature 35 ℃ Average low - temperature heat transfer temperature 25 ℃ Set inlet water temperature 55.00 ℃ Set outlet water temperature 42 ℃ Average high - temperature heat transfer temperature 48.500 ℃ Heat transfer temperature difference at the heat transfer interface of the heat exchanger 23.50 ℃ Heat transfer temperature difference of the inlet and outlet heat transfer medium (air) 20.00 ℃ Designed face - on wind speed ≦2.00 m / s Heat transfer temperature difference of the inlet and outlet heat transfer medium (hot water) 13.00 ℃ Designed flow rate of heat transfer medium (hot water) 350～400 t / h

[0112] Similarly, corresponding to the intermediate buffer balance tank 5, 75 crop room heat dissipation equipment 4 in parallel combination and 6 air handling unit heat exchange equipment 3 in parallel combination are connected in series as a group, and each group is connected to an intermediate buffer balance tank 5.

[0113] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and the descriptions in the specification are only preferred examples of the present invention and are not used to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A method for constructing a heat dissipation system of an agricultural greenhouse, including a heat dissipation system, characterized in that: The heat dissipation system consists of four types of heat dissipation devices: side wall heat dissipation device (1), transmission track heat dissipation device (2), air handling unit heat dissipation device (3), and floor heating heat dissipation device between crops (4). The side wall heat dissipation device (1) and the transmission track heat dissipation device (2) are directly connected in series to form the first-stage high-temperature heat dissipation subsystem. The air handling unit heat dissipation device (3) and the floor heating heat dissipation device between crops (4) are directly connected in series to form the second-stage low-temperature heat dissipation subsystem. The first-stage high-temperature heat dissipation subsystem and the second-stage low-temperature heat dissipation subsystem are connected in series through an intermediate buffer balance tank (5). The specific steps are as follows: S1. The highest inlet temperature of the second group of heat dissipation devices in the first-stage high-temperature heat dissipation subsystem, that is, the transmission track heat dissipation device (2), is set to ≤70°C, which is the highest outlet temperature of the first group of heat dissipation devices in the first-stage high-temperature heat dissipation subsystem, that is, the side wall heat dissipation device (1) ≤70°C; S2. Determine the outlet temperature T2 of the heating medium of the side wall heat dissipation device (1) according to the requirements of the planting process. According to the structural characteristics of the agricultural greenhouse and the requirements of the planting process, determine the initial temperature T1 of the heating medium that can be received, and the range of T1 is 70°C - 75°C; S3. Set the inlet temperature T2 and the outlet temperature T3 of the heat exchange medium of the transmission track heat dissipation device (2) according to the crop planting conditions, obtain the heat exchange temperature difference of the heating medium, ΔT = T2 - T3, and calculate the heat exchange amount that the transmission track heat dissipation device can complete; S4. Redistribute and calculate the configuration of other heat exchange devices.

2. The composition method of the agricultural greenhouse heat dissipation system according to claim 1, characterized in that: In step S2, according to the heat dissipation power Q1 that the side wall heat dissipation device (1) needs to complete, calculate the inlet temperature of the heating medium of the side wall heat dissipation device (1), that is, the initial temperature T1 of the heating medium that can be received, according to the formula Q1 = Kq(T1 - T2), where: Q1: The heat dissipation power of the side wall heat dissipation device (1), unit: KW; K: The specific heat capacity of the heating medium of the side wall heat dissipation device (1), unit: Kj / (Kg·K); q: The flow rate of the heating medium entering the side wall heat dissipation device (1), unit: Kg / s; T1: The temperature of the heating medium entering the side wall heat dissipation device (1), unit: K; T2: The temperature of the heating medium flowing out of the side wall heat dissipation device (1), unit: K.

3. The composition method of the agricultural greenhouse heat dissipation system according to claim 1, characterized in that: In step S2, calculate the heat exchange amount that the transmission track heat dissipation device can complete according to the formula Q2 = Kq(T2 - T3), where: Q2: The heat dissipation power of the transmission track heat dissipation device (2), unit: KW; K: The specific heat capacity of the heating medium of the transmission track heat dissipation device (2), unit: Kj / (Kg·K); q: The set flow rate of the heating medium entering the transmission track heat dissipation device (2), unit: Kg / s; T2: The temperature of the heating medium entering the transmission track heat dissipation device (2), T2 ≤ 70°C; T3: The temperature of the heating medium flowing out of the transmission track heat dissipation device (2), T3 ≤ 55°C.

4. The method for constructing an agricultural greenhouse heat dissipation system according to claim 1, characterized in that: The parallel combination of several side wall heat dissipation devices (1) and the parallel combination of several transmission track heat dissipation devices (2) are directly connected in series; the parallel combination of several side wall heat dissipation devices (1) and the parallel combination of several transmission track heat dissipation devices (2) are directly connected in series.

5. The method for constructing an agricultural greenhouse heat dissipation system according to claim 4, characterized in that: The number of monomers in the parallel combination of the side wall heat dissipation device (1) is reasonably combined according to the structural characteristics of the agricultural greenhouse, the distribution mode of the side wall heat dissipation device (1), as well as the pipe network diameter and flow velocity conditions. The number of parallel combinations of the transmission track heat dissipation device (2) is matched and combined according to the number of monomers in the parallel combination of the transmission track heat dissipation device (2).

6. The composition method of the agricultural greenhouse heat dissipation system according to claim 1, characterized in that: The side wall heat dissipation device (1) is arranged away from the personnel operation area and the crop planting area, and is close to the gable walls around the agricultural greenhouse. Large-diameter hot-dip galvanized steel pipes with low flow resistance are used as the heat dissipation device. The diameter of the hot-dip galvanized steel pipe is greater than 50 mm, and the inlet temperature of the heat exchange medium is higher than 70 °C.

7. The method for constructing an agricultural greenhouse heat dissipation system according to claim 1, wherein: The transmission track heat dissipation device (2) also uses the transportation track and overhead support in the agricultural greenhouse, and small and medium-diameter hot-dip galvanized steel pipes are used. The diameter of the hot-dip galvanized steel pipe is less than 40 mm, and the inlet temperature of the heat exchange medium is controlled to be lower than 70 °C.

8. The composition method of the agricultural greenhouse heat dissipation system according to claim 1, characterized in that: The air disc heat dissipation device (3) uses a forced ventilation copper tube aluminum fin heat dissipation device. The air disc heat dissipation device (3) is suspended or supported by a bracket in the space 0.5 meters to 2 meters above the ground in the greenhouse. The inlet temperature of the heat exchange medium is controlled to be lower than 55 °C, and the hot air temperature discharged by heat exchange is lower than 35 °C.

9. The method for constructing an agricultural greenhouse heat dissipation system according to claim 1, characterized in that: The floor heating heat dissipation device (4) between crops uses small-diameter hot-dip galvanized steel pipes. The diameter of the hot-dip galvanized steel pipe is less than 32 mm, and it is evenly distributed between crops. The inlet temperature of the heat exchange medium is controlled to be lower than 45 °C.

10. The method for constructing an agricultural greenhouse heat dissipation system according to claim 1, characterized in that: The intermediate buffer balance tank (5) is an open system communicating with the atmosphere, and the maximum designed buffer volume is the flow rate for 10 - 30 minutes.

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