Discussion on the renovation of heating and cooling stations at universities

Discussion on the renovation of heating and cooling stations at universities
In recent years, as the enrollment scale of universities has continued to expand and the size of schools has increased year by year, it has posed certain difficulties in the planning and renovation of heating and cooling systems.Many universities have not kept pace with the development of their schools. Due to the over-construction and expansion over the years, the heating and cooling system has not formed a sustainable mode of development. Some schools have to change each year, despite investing a large amount of money, without achieving good heating results.This is due to the lack of rigorous verification of the renovation plan, the incomplete scope of the project, and the first issue is the problem of power source renovation. Therefore, this article will propose problems existing in the direction of power source renovation and provide scientific and rigorous heating and cooling renovation plans.

1. Problem of boiler capacity and number.
   As the campus building area continues to increase, many universities have experienced the problem of expanding and renovating boiler rooms just as they have expanded. Small boilers not only increase the area and construction of boiler rooms, but also have many problems, such as low boiler operation efficiency, high auxiliary machine count, high energy consumption, and high maintenance capability.
   The selection of boiler unit capacity should be made as large as possible.
   Firstly, in terms of boiler heat loss, the unit capacity has doubled, but there has been no corresponding doubling in surface area and heat loss. The larger the unit capacity, the higher the efficiency (within certain limits).
   Secondly, as the unit capacity increases, the volume and heating surface of the boiler increase accordingly. There has been no increase in the amount of air burned per unit of fuel, thereby reducing flue gas loss.
   Thirdly, in industry design standards, the flue gas temperature of small boilers is much higher than that of large capacity boilers.This is because in order to reduce the flue gas temperature of small boilers, it is necessary to increase the heating surface of the boiler, which increases the steel consumption, volume, and economic disadvantage. Due to the difference in flue gas temperature, the difference between the two is further increased.
2. Problem of boiler unit capacity.
   Due to the continuous increase of campus building area, many universities have encountered the problem of expanding and renovating boiler rooms when just one has been expanded and put into operation. However, they are now faced with expanding and renovating another boiler room.This small capacity boiler not only increases the area and construction of the boiler room, but also has many problems, such as low boiler operation efficiency, high auxiliary machine count, high energy consumption, and high maintenance capability.
   The selection of boiler unit capacity should be made to maximize the unit's heat loss.
   Firstly, in terms of boiler heat loss, the unit capacity has doubled, but there has been no corresponding doubling in surface area. There has been no increase in heat loss due to the increased surface area of the boiler, which is the maximum heat loss.
   Secondly, with the increase in unit capacity, the volume and heating surface of the boiler also increase accordingly, but the amount of air burned per unit of fuel has not increased. This reduces the flue gas loss.
   Thirdly, in industry design standards, the flue gas temperature of small boilers is much higher than that of large capacity boilers.This is because to lower the flue gas temperature of small boilers, it is necessary to increase the heating surface of the boiler, which increases the steel consumption of the boiler, volume, and economic disadvantage. Due to the difference in flue gas temperature, the difference between the two is further increased.
3. There are many other factors that affect the difference in thermal efficiency between the two.Therefore, when choosing boiler capacity, it is important to choose a large capacity boiler to fully consider the need for stage-based load adjustments.
   In addition, based on the medium- to long-term development plan and current boiler counts in the school, the operating lifespan, and in the overall planning of the boiler room, it is not advocated to reserve too many boiler positions.This is because it is too costly in terms of construction and will lead to long-term idle and waste. It is recommended to reserve the positions.
   The disadvantages of parallel operation of different temperature boilers are that different boilers installed during different stages may have different supply and return water temperature parameters, resulting in a larger temperature difference.If the boiler circulation water is too large, it not only causes water distribution deviations within the boiler, but also affects the internal water circulation inside the boiler. Large temperature difference boilers increase the resistance losses in the system and may have a certain impact on the normal operation of the entire system.Therefore, it is not advocated to parallel operate different temperature boilers.
   If necessary, it is recommended to take the following measures to alleviate their impact: if the parallel arrangement of the boilers is adopted, the boilers with larger temperature differences should be located near the circulating pump.The boiler supply and return water mains should be connected indirectly, allowing the system circulation water to bypass the boiler and circulate through a bypass pipe. The diameter of the bypass pipe should be selected based on the system and boiler resistance. It is not advisable to be too large.It should generally meet the following types: S total = S1 + S2 + S3 + bypass, where S total: the total resistance losses of the boiler supply and return water mains. S1, S2, and S3: the respective resistance losses of the three boilers.S bypass: the resistance losses of the bypass pipe.
   It should be noted that the resistance losses of the boiler after the renovation should be close to the original design value.