Device for determining heat losses of greenhouses

FIELD: agricultural engineering.

SUBSTANCE: invention relates to device for control of microclimate in greenhouses. Proposed device is essentially closed space of greenhouse limited from one side by fragment of guard and by heat insulation from all other sides. Heating and measuring elements are installed inside. To protect measuring element from direct sun rays special screen is used. Control unit provides automatic control of device heating element and forms dc signal at its output corresponding to value of heat losses. Operation of device is based on measuring power of heater placed in closed space limited from one side by fragment of guard and at other sides by heat insulation. Heating element maintains is heated volume constant temperature equal to temperature maintained in zone of location of plants by means of automatic control system arranged in separate unit.

EFFECT: simplified design of device.

2 cl, 7 dwg

 

The invention relates to agricultural equipment and more particularly to devices associated with the climate control in greenhouses. A device for determining heat loss and thermal regulation of the greenhouse (A.S. 990134, class A 01 G 9/26, 1983), contains a potentiometric sensor, an engine which is equipped with flexible ribbon for communication with the plant and the heat-exchange chamber model of the greenhouse is equipped with electric move, and potentiometric sensor connected to the actuator moving the heat exchange chamber through an electric circuit synchronization. The disadvantages of this device is the complexity of operation, a large number of actuators and mechanical linkages.

Closest to the proposed invention is selected as a prototype Device for determining the heat loss of the greenhouseā€¯ (A.S. 403382, class A 01 G 9/26, BI No. 43, 1973), made in the form of greenhouse model, the size of which is determined by the similarity theory for thermal processes. The model is equipped with an electric heater and a supply device supplying and account for equal periods of time calibrated power pulses.

The above device is design complexity, the need for additional space for its installation. It is not the remains of this device can be attributed to the complexity of processing the output signal and the impossibility of use of this device in modern systems of automatic optimization of microclimate greenhouses.

The aim of the invention is to simplify the design of the device, obtaining at the output uniform electric signal proportional to the magnitude of the heat loss. Figure 1 shows the device for determining the heat loss of the greenhouse. figure 2 - structural diagram of the device, where 1 - measuring element (IE), 2 - heating element (ne), 3 - a current sensor ne, 4 - stabilizer temperature, 5 - normalizing Converter output, 6 - voltage regulator ne, 7 - power supply circuits of the device. figure 3 - block diagram of the regulator of the temperature of the heating element of the device, where 1 - measuring element, 2 - element, 3 - a current sensor ne, 4 - unit temperature IE, 5 - PI temperature controller, 6 - amplifier matching (K=1-10), 7 - temperature sensor IE, 8 - impedance amplifier (K=100), 9 - amplifier temperature indicator IE. 4 is a structural diagram normalizing transducer output signal 1 - signal amplifier current sensor, 2 - matching amplifier, 3 - low pass filter, 4 - impedance amplifier output signal. 5 is an electrical diagram normalizing Converter output device, where DA41 - operational amplifier (op-amp) type 140D24 (K=50), DA42 - OS 140YD17A (K=2), DA43 - OS 140D17 (K=1), range rxcx=10-100s. 6 is an electrical diagram of the stabilizer, the temperature of the heating element device, where DA51 - OS 140D24 (K=100), DA52 - OS 140D17A (K=1) diagram of a PI-regulator, DA53 - OS 140YD17A (K=2) scheme switch temperature indicator, DA54 - OS 140YD17A (K=10) diagram of a PI-regulator, DA55 - OS 140D177 diagram of the integrator of the PI-regulator, Rdtthe current sensor ne (R=0.10 OHM), DA56 - OS 140YD17A (K=1-10) diagram of a PI-regulator, VK - sensor t° IE germanium diode, R512 - unit t° IE, Vne- transistor - heating element. Fig.7 - voltage power devices, where DA61 - OS 140YD17A, VT61 - transistor (he=1000-1500, Ikmin=5 (A). Structurally, the device for determining the heat loss of the greenhouse is an enclosed space of the greenhouse (figure 1), limited on one side by a fragment of the fence 1 and the other sides of the insulation 2. Inside the heating element 4, the measuring element 3. To protect the sensor from direct solar radiation is the screen 5. The device 7 is painted on the outer side aluminum paint (silver) and protected with a film screen from exposure to air flow. For automatic control of the heating element of the device and forming at the output of an electrical DC signal corresponding to the magnitude of the heat loss, a control unit, which includes three main units: the voltage regulator (Phi is .7), normalizing Converter (structural scheme - 4, electricity - 5), higher temperature (structural scheme - 3, electrical - 6). The control unit can be located outside the device. This makes sense because the automatic control system operates in a changing set temperature, which is a specialized computer system. Therefore, it is advisable all the elements of the control system to have constructively in the control station. Precision device for the determination of the heat loss depends on the choice of the thickness of the insulation, which is calculated from the condition

for(tin-tnF≤Δ/qS,

where q is the power density losses through the working enclosure;

S - surface area;

F - area surface of the insulation;

K - heat transfer coefficient of the insulation;

tin- temperatures in the working space of the device is equal to the temperature in the greenhouse;

tn- ambient temperature;

Δ allowable error.

Because the greenhouse complex structure, consisting of surfaces with different orientation in space, to estimate the total heat loss it is necessary to have several such devices. Their number is determined by the design of the greenhouse and can vary from two to six. the ri to determine the total power readings devices should be added with weighting factors, taking into account the fraction of the area of the respective fences.

The principle of the proposed device, the heat loss is based on measuring the power of the heater 4 (figure 1), placed in an enclosed space bounded on one side by a fragment of the fence 1, and with other parties, the insulation 2. In this case the heating element with automatic control system, placed in a separate block, supports in a heated volume of constant temperature equal to the temperature to be maintained in the zone of location of the plants. The temperature control of the heated volume is measuring element 3 (copper coated black)that has a germanium diode (constant current)that is used as a temperature sensor.

The electrical circuit of the stabilizer temperature measuring element (IE) device thermal losses are presented on Fig.6. Here operational amplifiers DA52, DA54, DA55 perform the function of a PI-regulator. The control temperature value IE is analog instrument PIS. As the heating element (ne) is used transistor Vnewith a large he(1000-1500). To power the ne device with constant voltage provides a voltage regulator (circuit - 7). For gaining the high stability of the voltage U pused two-stage parametric stabilizer (VD61, VD62 and precision operational amplifier with setting 0). As a regulating transistor is transistor medium power high hemounted on the cooling radiator.

Electric circuit for normalizing Converter (figure 5) converts the value of electric power consumed by the device to determine heat loss and proportional to their size, into an electrical signal DC voltage 0-10 C. the Output voltage is determined by the amount of electric power consumed by the device when exposed to total physical parameters of meteorological factors. It is 10 In the amount of Joule heat losses technological facilities. Technical and economic effect is achieved by simplifying the structure of the device and increase the accuracy of measurement.

1. Device for determination of the heat loss of the greenhouse, including the element surface fences, insulation, heating element, temperature sensor and automatic power control necessary to ensure a predetermined temperature, characterized in that it is a fragment of a greenhouse, separated from the space of the greenhouse with the insulation layer and having on o the de normalizing Converter, converts a value of electric power consumed by the heating element of the device is proportional to the magnitude of the heat losses in the electrical signal DC.

2. The device according to claim 1, characterized in that the range of change of the output signal is 0-10V.



 

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SUBSTANCE: invention relates to device for control of microclimate in greenhouses. Proposed device is essentially closed space of greenhouse limited from one side by fragment of guard and by heat insulation from all other sides. Heating and measuring elements are installed inside. To protect measuring element from direct sun rays special screen is used. Control unit provides automatic control of device heating element and forms dc signal at its output corresponding to value of heat losses. Operation of device is based on measuring power of heater placed in closed space limited from one side by fragment of guard and at other sides by heat insulation. Heating element maintains is heated volume constant temperature equal to temperature maintained in zone of location of plants by means of automatic control system arranged in separate unit.

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