Publish Time: 2023-07-03 Origin: Site
In the past, the traditional measures for heating or insulation in winter aquaculture were boiler heating, insulation equipment, etc. In terms of constant temperature in aquaculture, most farmers' equipment is outdated. In winter aquaculture, many farmers still rely solely on boiler coal burning mode, which not only pollutes the environment, but also can only solve the heating problem in winter. When cooling seawater in summer, cooling equipment is also required. The traditional method of extracting groundwater and directly mixing it with seawater to reduce seawater temperature seriously wastes groundwater resources while also damaging the water source environment required for aquaculture.
With the development trend of modern fisheries such as industrialized aquaculture of shrimp, crabs, and fish, industrialized aquaculture requires certain conditions, among which controlling water temperature is a key technology. Shrimp and shellfish breeding, as well as grouper and eel, require a water temperature of around 22 ℃ to 25 ℃. In winter, it is necessary to warm up the aquaculture water, while in summer, it is necessary to cool down the aquaculture water. Controlling the water temperature in a suitable environment can effectively improve the survival rate of aquaculture and greatly increase the density of aquaculture, thereby effectively improving the economic benefits of farmers.
The loss of heat in the pool water (heat dissipation from the surface of the pool to the environment, heat dissipation from the water body to the pool body and walls, and heat load demand from replenishing fresh water) leads to a decrease in water temperature. Therefore, it is necessary to always ensure that the heat provided to the breeding pool meets the heat dissipation from the pool to ensure the constant temperature of the water body. Based on the demand, our system designs a heat pump heating system that provides heat at all times equal to the maximum heat dissipation of the pool.
The temperature difference between the inlet and outlet of the constant temperature pipeline in the pool may be greater than the temperature difference between the supply and return water for stable operation of the heat pump. Therefore, an intermediate water tank is added to the system design to ensure the stability of the inlet and outlet water temperature at constant temperature of the water body.
The factor that affects the selection of heat pump host is the maximum heat dissipation rate of the water body. There are three factors that affect the heat dissipation of the water body: the heat dissipation from the water pool to the environment, the heat dissipation from the water body to the bottom or wall of the pool, and the heat demand brought by supplementing new water. Therefore, for the entire project, it is necessary to pay attention to the insulation of the greenhouse where the pool is located and the insulation of the pool. It is also necessary to control the water exchange rate to control the initial investment cost of the heat pump host.
System application: If the maximum heat dissipation of the water body is calculated as A kw, then the selection of the heat pump host requires that the heating capacity of the host corresponding to the water outlet at 45 ℃ be greater than or equal to A kw. The size of the intermediate insulation water tank is selected based on the size of the constant temperature system. The larger the water body and constant temperature heat, the larger the water tank needs to be configured.
System advantages: The two sides of the insulation water tank are the heat consumption end and the heating end, and the consistent heat supply and demand on both sides can ensure that the water in the water tank is in a stable state of 45-50 degrees. This way, the heat pump host and the water tank can operate in a stable state at constant temperature, and the service life of the host will increase; The heating tube directly heats the water in the pool, reducing intermediate links and maximizing energy.
The application scope of this type of constant temperature method: projects with water temperature requirements below 20 ℃ (such as sea cucumber breeding).
The constant temperature method of the breeding greenhouse is to directly maintain the temperature of the greenhouse environment to indirectly ensure the water temperature. Compared to the heating method of laying heating pipes in the pool, the heating system is simpler, omitting the intermediate insulation water tank and a set of water pumps. The hot water heated by the host directly enters the end fan coil for heating, reducing the heat loss on the side of the insulation water tank; Furthermore, the temperature control at the end is relatively simple and accurate.
The constant temperature method for breeding greenhouses has stricter requirements for the insulation of the greenhouses and the wall of the pool. The heat dissipation of water bodies also includes three parts (heat dissipation from the pool to the environment, heat dissipation from the water body to the bottom or wall of the pool, and heat demand from supplementing new water). However, this system only maintains constant temperature for the environment. Limiting the heat dissipation from the pool to the environment requires proper insulation at the bottom and walls of the pool to reduce heat dissipation. In addition, the frequency of water replacement during use also requires a reasonable and scientific plan to reduce the losses caused by water replacement.
The constant temperature method in the breeding greenhouse is not suitable for all projects that use constant temperature in the greenhouse to maintain a constant water temperature. If the water temperature requirement is too high, this method cannot meet the heat dissipation requirements of the entire water body. The best application of constant temperature method in breeding greenhouses is for projects with water temperature requirements below 20 ℃.
The utilization of breeding greenhouses ensures a constant temperature of over 30 degrees Celsius, which almost meets the constant water temperature requirements of all common breeding projects.
As the name suggests, it means changing water to maintain a constant water temperature. In a class of system, the heat pump continuously heats the water in the water storage and insulation tank, heating it to the required temperature within the allowed time, and then centralizing the time for water exchange.
PS: The size of the water tank is the maximum daily water change.
The heat pump heats the water tank to ensure its water temperature, and the water in the tank is then changed to the tank according to the needs of the breeding pool. The entire system design is relatively simple, and the difficulty of construction is also relatively small.
For example: 1000m ⊃3; Water aquaculture projects require 10% fresh water replenishment every day, with seawater as the source of water. During the aquaculture period, the coldest temperature of seawater is 2 ℃, and the aquaculture pool requires a constant temperature of 18 ℃.
1) The maximum daily water change is 1000 × 10%=100m ⊃3;
2)100m ⊃3; The heat of water from 2 ℃ to 18 ℃ is 1.163 × one hundred × (18-2)=1860.8 kW · h. Select a heat pump unit based on the above data, considering minimizing the initial operation of the equipment. The smaller the hourly heating capacity, the smaller the selected unit.
3) The daily water change process takes 2 hours. (Provided by breeding users, different projects, different times). According to the water change time, the daily operating time of the unit can be set to 20 hours (with 2 hours of downtime reserved)
4) The size of the equipment required for water exchange is 1860.8 ÷ 20=93.04kw. Choosing a device with a heating capacity of 93.04kw can meet the constant temperature demand.
There is also a constant temperature method of long running water, which is called long running water mode because the aquaculture water requires continuous replenishment and drainage for 24 hours.
In the constant temperature system with long flowing water, the increase of plate exchange is to recover the heat from the drainage, in order to improve the make-up water entering the heat pump unit and reduce energy consumption.
For example, a long-term aquaculture project requires a constant water temperature of 20 degrees Celsius and a water flow rate of 60m ⊃3;/ h. The temperature of the new water is 15 ℃.
1) The heat required for constant temperature is 1.163 × sixty × (20-15)=349kW
2) Heat recovery by plate exchange: replenish fresh water at 15 ℃ and drain water at 20 ℃. The temperature of the new water after heat exchange is 17 ℃.
3) The heat required for heating the host is 1.163 × sixty × (20-17)=210kW
If the heat recovery by the plate exchange is not increased, a 349kW capable host needs to be selected. If the recovery is selected, a 210kW capable host can be selected. Not only does it reduce initial investment, but it also reduces the cost of later use.
Aquaculture constant temperature method 5: direct heating
Direct heating is often used in recirculating aquaculture water treatment systems.
Direct heating usually involves water entering the host directly. Due to the uncontrollable amount of oxygen and other components in the water, it poses certain risks to the host. Therefore, it is rarely applied in practical cases.
At present, the global large-scale aquaculture mainly includes freshwater aquaculture, seawater aquaculture, and shallow sea aquaculture. The main fish species cultivated include shrimp, carp, eel, tilapia, loach, grouper, bream, etc. In order to address the shortage of local aquaculture water and soil resources and avoid natural disasters, factory systems have been introduced in many regions to promote the development of aquaculture water recycling and reuse.
Faced with this situation, our aquaculture constant temperature heat pump unit utilizes a small amount of electrical energy to obtain heat from the air, which is energy-saving, environmentally friendly, and pollution-free. At the same time, it can complete the heating of winter fish ponds and the cooling of summer fish ponds. The constant temperature heat pump provides a constant water temperature function for factory farming, without the need for dedicated personnel to maintain it. The microcomputer automatically controls it, and when the water temperature exceeds the set temperature, it automatically starts heating or cooling to the set temperature, LED status display, simple operation, effectively solving the problem of water temperature control in aquaculture. The aquaculture constant temperature heat pump profession provides a constant water temperature function for factory aquaculture systems, solving practical problems for farmers, and has a very broad application prospect. Air energy heat pumps are safe and reliable, with high cost-effectiveness. Farmers use air energy heat pumps to heat and cool seawater and freshwater. They are a low energy consumption, pollution-free heating and cooling technology that does not consume groundwater, and meet the basic policies of energy and environmental protection in China and the strategic requirements for sustainable development of the national economy.
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