In summer, the ambient temperature in the piggery is high in most areas and heatstroke prevention must be considered. In the southern region, open or windowed structures are usually used, and the temperature within the house is basically controlled by the climate outside the house. Therefore, effective cooling measures should be taken during high temperatures.
1 pig house cooling method
There are many ways to reduce the temperature. The mechanical refrigeration method, because of its high equipment and operating costs, makes it extremely uneconomical and is generally not adopted.
Green shade and awning shading can effectively block solar radiant energy. Shading is a simple and effective cooling method in areas with strong solar radiation and low humidity in summer.
Ventilation is also an effective method of cooling. In summer, the airflow speed of natural ventilation is low, and mechanical ventilation is often used to form a relatively strong airflow for cooling. However, if the air flow rate is too high, it is not very profitable to the pig from the physiological point of view, and the high airflow will make the pig uncomfortable. In addition, ventilation alone can only bring home temperatures close to the outside air temperature, so the effect of simple ventilation is limited. However, according to the big pigs afraid of heat and not afraid of the cold, pigs are afraid of the cold and not afraid of hot features, some people think that piglets can rely on simple ventilation can achieve cooling purposes.
Cold water cooling is a cooling method that uses cold water, which is much lower than the temperature inside the house, to make full contact with the air and exchange heat, thereby reducing the air temperature in the house. This method uses the sensible heat of water to reduce the air temperature in the house. If cold water below the dew point is used, it also has the advantage of dehumidifying cooling. However, the sensible heat of water is relatively small (4.18 kJ/kg C), and the cooling capacity is limited. Therefore, a large amount of low-temperature water is consumed. Except where it is possible to use abundant low-temperature groundwater, cold water cooling is generally not used.
Evaporation is a cooling method suitable for use in piggeries. When water evaporates, it absorbs a large amount of latent heat of evaporation from the surrounding air, thereby lowering the temperature. At a temperature of 25 degrees Celsius, the evaporation heat of water is 2442 kJ/kg. Compared with the cold water cooling method when the temperature of 15°C cold water is raised to 25°C, the evaporative cooling is absorbed from the air at the same water consumption. The heat is 58 times cooler than cold water, so the evaporative cooling efficiency is higher. However, under conditions of high humidity, water does not have much room for evaporation, so the cooling effect is not good.
The soil-air heat exchange cooling is adopted by some pig farms abroad. According to information, 12 wind pipes are buried radially at a depth of 3 meters below the ground, each of which is 30 meters long. One end is connected to a vertical pipe buried in the house, and the other end is a buried pipe with a fan outside the house. Connected. After the fan is started, the air flows through the air duct and the formation heat exchange. Warming in winter and cooling in summer. When the temperature outside the house is -28°C, the temperature of the air entering the house via the underground pipe reaches 1°C. When the outdoor temperature in summer is 35°C, the air can be reduced to 24°C after flowing through the underground air duct. A farm has buried 20 air ducts with a diameter of 18 cm and a length of 35 meters underground. When the air supply volume is 10,000 cubic meters per hour, the air temperature within the premises can be kept between 15-21 degrees Celsius all year round. However, it should be pointed out that this information does not indicate that this device will allow such a cooling effect in a large area of ​​the house.
Drop cooling is another economical and effective method of cooling, which is suitable for single-location boars and farrowing sows. Installed dripping cooling heads above the necks of these pigs, droplets of water dripped intermittently into the pig's neck. The pigs feel particularly cool due to the nerves of the pig's neck. In addition, dripping water spreads on the surface of the pig's back, evaporates, and the pig is endothermically cooled. Dripping water cooling is not to reduce the ambient temperature, but directly reduce the body temperature of pigs.
2 wet curtain-fan cooling system
The wet curtain-fan cooling system is already a kind of production cooling device, which is mainly based on evaporation and cooling, supplemented by ventilation and cooling. It consists of wet curtain (or wet pad), fan, circulating water circuit and control device. Wet curtain cooling system is very obvious in the cooling effect of hot areas. In hot and humid areas, except for some days with high humidity, this is also a feasible cooling device.
In the wet curtain cooling system, the wet curtains have a great influence on the cooling effect. Relatively speaking, the wet strength paper wet mat made of a resin treated and corrugated honeycomb structure has good cooling effect, low ventilation resistance, stable structure, and convenient installation. , can be used continuously for many years. When its surface wind speed is 1 to 1.5 m/s, the wet pad resistance is 10 to 15 Pa and the cooling efficiency is 80%.
Wet curtains (or wet mats) can also be made from aspen wood shavings, brown silk, porous concrete panels, plastic panels, straw ropes, and the like. When poplar wood shavings are made into a wet pad, if the thickness and density of the shavings pad are increased, the cooling effect can be increased, but the ventilation resistance is also increased. Aspen wood shavings have a density of 25 kg/m3 and a thickness of 8 cm is reasonable. The windward surface wind speed of the shavings wet pad is 0.6-0.8 m/s.
After each use, the pump should be stopped a few minutes earlier than the fan so that the wet pad evaporates and dry, reducing the long pad of the wet pad; in the winter, the outside of the wet curtain should be covered with insulation. Aspen shavings are generally changed once a year. Ripple wet strength paper wet pad has a service life of about 5 years. This is not the strength damage. It is the scale and sphagnum that the surface of the wet pad gathers. It loses its water absorption and shrinks. Overcurrent section. In the process of using, aspen wood shavings will fall down, ripple wet wet paper will also shrink and shrink, this will make the wet curtain gaps cause air flow short circuit, reduce the application effect, should pay attention to fill and adjust at any time.
The wet curtain cooling system can install the wet curtain on one side of the vertical wall, and the fan is installed on the other side of the vertical wall, so that the air flow flows laterally in the house. Wet curtains and fans can also be installed on both sides of the wall, so that the air flow in the vertical flow.
3 spray cooling system
The spray cooling system sprays water into mist particles to rapidly vaporize water and absorb the sensible heat in the pig house. This kind of cooling system is simple in equipment and has a certain cooling effect, but it increases the humidity in the house, so it generally needs intermittent work.
When a drop of water weighing 1 gram is sprayed into granules with a diameter of 0.008-0.01 cm, the total surface area will be expanded by several hundred times, which greatly accelerates the speed of water vaporization. Under normal circumstances, spray is used to exert the cooling effect through several ways: the spray nozzle sprays water into mist particles with a diameter of 0.1 mm or less, and the mist particles vaporize in the air in the pig house when they absorb a large amount of sensible heat; The mist particles can cause local cooling and convection in the air. Part of the water falls on the pigs and directly absorbs the heat on the pigs and vaporizes the pigs.
When the spray cools, the air's moisture content increases as the temperature drops. After a certain period of time (about 1-2 minutes according to the test), the moisture-heat balance is reached and the air vapor content in the room is nearly saturated. In addition, the ground may be wetted by large drops of water. If spraying is continued, the pig house will be too wet to have an adverse effect. The smaller the pig, the greater the impact, and therefore the sprinkler must work intermittently intermittently. This type of cyclical high humidity has a much smaller adverse impact on the home environment. If the internal and external air relative humidity is inherently high and the ventilation conditions are not good, it is not appropriate to perform spray cooling. Spraying with a certain flow rate in the air can increase the cooling effect. The flow of air can make the mist particles evenly distributed, which can accelerate the moisture on the surface and ground of pigs and the vaporization of floating mist particles.
The spray cooling of large-scale pigs is actually not spray cooling air, but the spray head wets the pig's epidermis and direct evaporative cooling. In this case, the size of the mist particles sprayed by the spray head is not high, and the spray head may be provided at the top of each column, and the spray amount of the spray head is 0.0017 meters and 3/10 head points. The shower head is downwardly installed and the fog cone formed is suitable to cover the 3/4 width of the pig bar. The time relay was used to set the spray for 2 minutes, and the spray was sprayed once per hour. The spray pressure is 2.7 kg/cm2, and the nozzle installation height is about 1.8 meters.
To obtain smaller mist particles, special nozzles must be used to increase the spray pressure. At present, the high-pressure micro-mist cooling system used in agricultural buildings is only a few microns in diameter. Such a small amount of mist particles can generally be completely vaporized when the humidity is floated within 2 meters. The cooling effect is very obvious. This cooling system has relatively high equipment costs because the pressure in the pipeline is as high as tens of kilograms per square centimeter. To ensure the safety of high-voltage equipment, professional companies should be asked to make and install it.
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