1. Introduction
In foundry workshops, electric furnaces are crucial power – consuming equipment, and their 配套的专用变压器 (supporting dedicated transformers) play a vital role in power conversion. Placing these transformers in a semi – basement structure under the electric furnace platform has become a common layout in modern foundry workshops. This layout not only brings the transformers closer to the load center but also ensures smooth operations of charging and molten iron transportation. However, during operation, transformers generate a substantial amount of heat. Without proper ventilation measures, the accumulated heat can cause the temperature in the transformer room to rise significantly, which may lead to overheating of the transformers. This not only affects the normal operation of the transformers but also shortens their service life and even poses potential safety hazards. Therefore, designing an efficient and energy – saving ventilation system for the electric furnace transformer room is of great significance.
2. Project Overview
2.1 Location – specific Challenges
The foundry workshop under study is located in Changchun, Jilin Province. Changchun has distinct seasonal variations, with cold winters and relatively warm summers. In winter, the outdoor temperature can drop to extremely low levels, while in summer, it can be relatively hot and humid. These climate characteristics pose unique challenges to the design of the ventilation system for the electric furnace transformer room.
2.2 Layout of the Transformer Room
The electric furnace – supporting transformers are placed in a semi – basement structure under the electric furnace platform. This semi – basement layout has its own characteristics in terms of space utilization and air circulation. The limited space and the need to maintain a certain distance from the electric furnace for safety reasons make it necessary to carefully plan the ventilation system to ensure effective heat dissipation.
3. Ventilation Design Basics
3.1 Ventilation Quantity Calculation
Calculating the ventilation volume of the transformer room is the foundation of the ventilation design. The formula for calculating the ventilation volume of the transformer room is , where represents the heat output of the transformer (when operating at full load), is the air density (usually taken as ), is the specific heat of air (), is the exhaust air temperature, and is the supply air temperature.
It is generally stipulated that the temperature around the transformer during normal use should not exceed , so is usually set to . For , it is taken as the calculated outdoor ventilation temperature in summer. In Changchun, this value is . By accurately calculating the ventilation volume based on the actual heat output of the transformer, the design can ensure that the ventilation system can effectively remove the heat generated by the transformer.
| Parameter | Symbol | Value | Unit |
|---|---|---|---|
| Ventilation volume | Calculated value | ||
| Transformer heat output | Specific value (depends on transformer model) | ||
| Air density | |||
| Specific heat of air | |||
| Exhaust air temperature | |||
| Supply air temperature | (Changchun summer) |
3.2 Airflow Organization Design
Airflow organization is a key factor in ensuring the effectiveness of the ventilation system. Through numerical simulation and practical measurements by many scholars and engineers, it has been found that the trench air supply + upper mechanical exhaust air mode can effectively improve the ventilation and heat transfer efficiency. In this mode, fresh air enters the transformer room from the trench at a low speed after being filtered. It then flows through the transformer, absorbing the heat generated during operation, and is finally exhausted from the upper part of the room through mechanical exhaust fans.
This airflow organization not only forms a reasonable air circulation path but also helps to reduce the ventilation volume and the energy consumption of the ventilation system. The air flow direction is from the air supply outlet to the transformer and then to the exhaust outlet, as shown in Figure 1.
[Insert Figure 1: Schematic diagram of the airflow organization in the electric furnace transformer room ventilation system]
3.3 Design of the Supply and Exhaust Air Systems
3.3.1 Trench Air Supply System
The air supply system uses a roof – mounted air supply fan, which is a variable – frequency fan. It is installed in the outdoor green belt. The inlet of the roof – mounted air supply fan is equipped with a G3 coarse – filter screen to filter out dust and impurities in the outdoor air. After filtration, the fresh air is sent into the lower part of the electric furnace transformer room through the air supply trench at a low speed. The air supply volume is basically equivalent to the exhaust volume. This not only reduces the indoor temperature but also makes the indoor pressure slightly positive, reducing the probability of dust entering the transformer room.
3.3.2 Upper Mechanical Exhaust Air System
The exhaust air system uses a box – type centrifugal fan installed on the electric furnace platform. The fan is also a variable – frequency fan and is lined with sound – absorbing perforated plates to reduce noise during operation. The exhaust outlet is a single – layer louvered air outlet, which is set on the upper part opposite the air supply outlet. The exhaust air from the transformer room is led to the workshop roof through the exhaust duct and then discharged outdoors.
In winter, considering the heat utilization, an additional function is added to the exhaust air system. Since there is a partition wall between the electric furnace area and the material storage area in the workshop, and the material track vehicle passes through the partition wall through an electric rolling shutter door. The material storage area has no heating facilities, while the exhaust air from the electric furnace transformer room is hot. Therefore, a branch is added to the exhaust duct of the electric furnace transformer room. Through the switching of the electric air valve, in winter, the exhaust air from the electric furnace transformer room can be connected to the side of the electric rolling shutter door opening in the material storage area. A slit – type air outlet is set on the side of the vertical air duct to form an air curtain effect. This can effectively block the cold air in the material storage area from entering the electric furnace area and at the same time supply heat to the material storage area, achieving waste heat utilization. In other seasons, the exhaust air from the electric furnace transformer room is directly discharged outdoors through the roof.
4. System Operation Control Strategy
4.1 Automatic Control System
The ventilation system of the electric furnace transformer room is equipped with an automatic control system. This system can improve the automation level of the ventilation system, enhance production efficiency, and reduce the operation difficulty for workers in the workshop. The main controlled objects of the automatic control system include the air supply fan, the exhaust air fan, electric air valve A, and electric air valve B.
4.2 Control Objectives
The primary goal of the automatic control system is to ensure that the indoor temperature of the electric furnace transformer room does not exceed . Secondly, it needs to adapt to the climate changes throughout the year, perform working condition conversions, and adjust the air volume. When the heat output of the transformer changes or the outdoor air intake temperature changes, the automatic control system can adjust the operating frequency of the air supply and exhaust fans in a timely manner to adjust the air volume, thereby effectively reducing the energy consumption of the ventilation system.
The start – stop and frequency control of the exhaust fan can be determined according to the instructions of operators, schedules, or signals from the transformer interlock. When the measured indoor temperature is higher than the set value, the fan frequency is increased; when it is lower than the set value, the fan frequency is decreased. The start – stop and frequency control of the air supply fan and the switching of electric air valves A and B are also adjusted according to specific conditions, such as maintaining a certain indoor positive pressure and switching between summer and winter working conditions.
| Controlled Equipment | Control Content | Control Requirements |
|---|---|---|
| Exhaust Fan | Start – stop and frequency | Start – stop command can be determined by operator instructions, schedules, or transformer – related signals. Frequency is adjusted according to the deviation between the measured and set values of the controlled area temperature. When the indoor temperature is higher than the set value, the frequency is increased; when lower, it is decreased. Interlocked with the exhaust fan. |
| Air Supply Fan and Electric Air Valve A | Start – stop and frequency | Adjusted according to the positive pressure requirements. When the measured micro – positive pressure is lower than the set value, the air supply fan frequency is increased; when higher, it is decreased. The switching commands of electric air valves A and B can be determined by operator instructions, schedules, etc. In summer and transitional seasons, electric air valve A is opened and electric air valve B is closed to discharge the exhaust air outdoors through the roof. |
5. Energy – saving and Environmental Protection Considerations
5.1 Energy – saving Measures
The use of variable – frequency fans in the ventilation system is an important energy – saving measure. By adjusting the fan speed according to the actual heat load and temperature requirements, the ventilation volume can be accurately controlled, avoiding unnecessary energy consumption caused by constant – speed operation. In addition, the waste heat utilization in winter is another significant energy – saving measure. By recycling the heat from the exhaust air of the transformer room to heat the material storage area, the energy consumption of heating equipment in the material storage area can be reduced.
5.2 Environmental Protection Significance
Reducing energy consumption in the ventilation system not only saves energy costs for the foundry workshop but also has positive environmental protection implications. Less energy consumption means less use of fossil fuels, which in turn reduces greenhouse gas emissions and contributes to environmental protection. Moreover, by preventing dust from entering the transformer room, the ventilation system helps to maintain a clean working environment and reduces the pollution of the surrounding environment.
6. Comparison with Other Ventilation Systems
6.1 Traditional Ventilation Systems
Traditional ventilation systems for transformer rooms may use simple natural ventilation or mechanical ventilation without considering the characteristics of the workshop environment and the heat load of the transformer. For example, natural ventilation may not be able to effectively remove heat in high – temperature seasons, while traditional mechanical ventilation may consume a large amount of energy due to constant – speed operation and lack of intelligent control.
6.2 Comparison Results
The trench air supply + upper mechanical exhaust air ventilation system proposed in this paper has obvious advantages over traditional ventilation systems. It can achieve better heat dissipation effects through reasonable airflow organization, and the use of variable – frequency fans and waste heat utilization measures can significantly reduce energy consumption. The following table summarizes the comparison results.
| Comparison Items | Traditional Ventilation Systems | Trench Air Supply + Upper Mechanical Exhaust Air System |
|---|---|---|
| Heat Dissipation Effect | Limited in high – temperature seasons | Effective throughout the year |
| Energy Consumption | High, due to constant – speed operation and lack of waste heat utilization | Low, with variable – frequency fans and waste heat utilization |
| Adaptability to Climate Changes | Poor | Good, with working condition conversion and air volume adjustment |
| Indoor Air Quality | Prone to dust entry | Reduced dust entry probability due to positive pressure |
7. Maintenance and Management of the Ventilation System
7.1 Regular Inspection
Regular inspections of the ventilation system are essential to ensure its normal operation. Inspections should include checking the operation status of fans, the tightness of ducts, the cleanliness of filters, and the functionality of electric air valves. Any abnormal conditions should be detected and repaired in a timely manner.
7.2 Filter Replacement
The filters in the air supply system need to be replaced regularly. Clogged filters can reduce the air supply volume and affect the ventilation effect. According to the actual dust concentration in the workshop environment, a reasonable filter replacement cycle should be determined to ensure the normal operation of the ventilation system.
7.3 Fan Maintenance
Fans are the core components of the ventilation system. Regular maintenance of fans, including lubricating bearings, checking the balance of impellers, and inspecting electrical components, can extend the service life of fans and ensure their stable operation.
8. Future Development Trends
8.1 Intelligent Control Upgrade
With the continuous development of technology, the intelligent control of ventilation systems will be further upgraded. Future ventilation systems may be equipped with more advanced sensors and control algorithms, which can more accurately monitor the temperature, humidity, and air quality in the transformer room. The control system can then adjust the ventilation volume and working conditions in real – time, achieving more precise control and better energy – saving effects.
8.2 Energy – saving Technology Innovation
New energy – saving technologies will continue to emerge and be applied to ventilation systems. For example, the use of energy – recovery devices, such as heat – pipe heat exchangers, can further improve the energy – saving efficiency of the ventilation system. These devices can recover the heat from the exhaust air and transfer it to the incoming fresh air, reducing the energy required for heating or cooling the fresh air.
8.3 Integration with Other Systems
In the future, the ventilation system of the electric furnace transformer room may be more closely integrated with other systems in the foundry workshop, such as the power supply system, the cooling water system, and the production management system. This integration can achieve more comprehensive optimization and management, improving the overall efficiency of the workshop.
9. Conclusion
The design of the ventilation system for the electric furnace transformer room in a foundry workshop is a complex but crucial task. By comprehensively considering factors such as ventilation volume calculation, airflow organization, system design, and operation control strategy, an efficient, energy – saving, and environmentally friendly ventilation system can be developed. The trench air supply + upper mechanical exhaust air ventilation system proposed in this paper has demonstrated its superiority in heat dissipation, energy – saving, and adaptability to climate changes. Through continuous improvement and innovation in system design, operation management, and the application of new technologies, the ventilation system can better meet the development needs of foundry workshops and contribute to the sustainable development of the industry.
In addition, with the continuous progress of technology, future ventilation systems will become more intelligent, energy – saving, and integrated. By keeping an eye on these development trends and actively applying new technologies, we can ensure that the ventilation systems of electric furnace transformer rooms in foundry workshops always maintain high – quality performance.
