Secondary return air conditioning system with reheater and adjustable ratio

Abstract

A secondary return air air conditioning system with an adjustable reheater ratio belongs to the field of air conditioning technology. It includes an air handling unit, a service room, an air supply duct, a return air duct, a fresh air duct, an analog electric regulating valve provided on the primary return air duct, and an electric regulating valve provided on the secondary return air duct. It mainly solves the problems of low dew point and uncontrollable problems existing in traditional secondary return air systems. Its characteristics are that when the heat and humidity ratio of the room served by the air conditioning system decreases, the dew point temperature obtained by the traditional calculation method is low, and the use of conventional cold sources cannot meet the requirements of the lower dew point temperature. The present invention adds a reheater, which can increase the dew point temperature of the system when the heat and humidity ratio of the room is low, so that the conventional cold source can meet the use requirements of the system, and the secondary return air system can be effectively controlled. The present invention can replace the traditional primary return air air conditioning system in the field of clean air conditioning and other constant temperature and humidity air conditioning, and has a very good energy-saving effect.

Description

Technical Field

[0001] The invention belongs to the technical field of air conditioning and is an energy-saving secondary return air treatment method with a reheater and adjustable ratio. Background Art

[0002] Currently, air conditioning systems designed for temperature and humidity control often utilize single-return air systems. These systems require cooling and dehumidification before heating the air to the supply point for delivery to the indoor environment. This cooling-before-heating process results in a cancellation of cooling and heating, leading to significant energy waste. Some designs utilize a single-return air system with a fixed primary-to-secondary return air ratio, which offers improved energy savings. However, the primary and secondary air volumes cannot be adjusted with load fluctuations, preventing maximum energy savings.

[0003] Traditional secondary return air involves mixing outdoor fresh air with a portion of indoor return air, then subjecting it to heat and moisture treatment before mixing it with a portion of indoor return air. This process, called secondary return air, uses the air volume from this second mixing to offset the reheat required for the primary return air, achieving energy savings. Traditional secondary return air systems lack reheaters, requiring adjustments to primary and secondary return air volumes to meet load fluctuations. However, as the heat-humidity ratio decreases during this adjustment process, the dew point temperature drops. Conventional 7 / 12°C cooling sources struggle to meet these low dew point requirements. Therefore, this method struggles to meet load fluctuations and is rarely adopted in real projects due to its inability to effectively control the air flow. Summary of the Invention

[0004] The purpose of the present invention is to provide a secondary return air conditioning system with an adjustable reheater ratio, which can adjust the primary and secondary return air volumes according to changes in indoor load, and can use conventional cold sources to meet the dew point temperature requirements, thereby solving the problem of low and uncontrollable dew point in traditional secondary return air systems.

[0005] To achieve the above object, the present invention provides the following technical solution: a secondary return air conditioning system with an adjustable reheater ratio, characterized in that: Figure 1 , including an air handling unit 1, a service room 2, a supply air duct 3, a return air duct 4, and a fresh air duct 5. The air handling unit includes a primary return air mixing section a, a surface cooling section b, a secondary return air mixing section c, a reheat section d, and a fan section e. The return air duct is respectively connected to the primary return air mixing section and the secondary return air mixing section of the air handling unit. The primary return air duct is provided with an analog electric regulating valve 6, and the secondary return air duct is provided with an analog electric regulating valve 7.

[0006] The air handling process of the above air handling unit in the summer cooling condition with high heat and humidity is as follows: the fresh air at point W is mixed with the indoor primary return air at point N to point C, cooled to point L by the surface cooler, and then mixed with the indoor secondary return air at point N to the air supply state point O and sent into the room. Figure 2 .

[0007] The air handling process of the above-mentioned air handling unit in the summer and transition season cooling condition with low heat and humidity ratio is as follows: the fresh air at point W is mixed with the indoor primary return air at point N to point C, cooled to point L by the surface cooler, and then mixed with the indoor secondary return air at point N to point M, and then heated to the intersection point O with the indoor heat and humidity ratio line, that is, the air supply state point, and then sent into the room. Figure 3 .

[0008] The air handling process of the above-mentioned air handling unit in the summer and transition season cooling condition with low heat and humidity ratio can also be set with the reheater between the surface cooling section and the secondary return air mixing section, that is: the fresh air at point W is mixed with the indoor primary return air at point N to point C, cooled to point L by the surface cooler, and then heated to the intersection point M with the indoor heat and humidity ratio line, and then mixed with the indoor secondary return air to the air supply state point O, and sent into the room, such as Figure 4 .

[0009] The two air treatment methods with relatively small heat and humidity ratios mentioned above have the same function despite different reheater positions. The former has a larger air volume passing through the reheater and a better heat exchange effect. Both methods are within the scope of protection of the present invention.

[0010] The above-mentioned large or small heat and humidity ratio means that the temperature of the intersection of the heat and humidity ratio line and the saturated relative humidity line is TL. When the surface cooling section can cool the air it processes to TL, the heat and humidity ratio is large; when it cannot cool to TL or the heat and humidity ratio line has no intersection with the saturated relative humidity line, the heat and humidity ratio is small.

[0011] The air handling process of the above-mentioned air handling unit in winter heating operation can be designed according to existing methods, and functional sections can be set as needed, such as setting a filtration section, preheating section, humidification section, etc.

[0012] The functional sections of the above-mentioned air treatment process can be arranged uniformly or separately in the air handling unit, both of which are within the protection scope of the present invention.

[0013] The present invention sets a reheater and uses it when the heat-humidity ratio is low in the cooling condition, with the purpose of increasing the dew point temperature so that the secondary return air system can be effectively controlled. The main reason why traditional secondary return air is not applied is that the parameters of this design method are calculated according to the maximum load of the air conditioner design, without fully considering the load changes. During the load changes of the actual project, when the heat-humidity ratio of the room is reduced, the intersection of the heat-humidity ratio line and the saturated relative humidity line on the enthalpy-humidity diagram moves downward, that is, the dew point temperature drops. At this time, the surface cooler using a conventional cold source may not be able to cool to the required dew point temperature. As the heat-humidity ratio continues to decrease, the heat-humidity ratio line and the saturated relative humidity line may not intersect, which makes the traditional secondary return air system uncontrollable. The present invention sets a reheater. When the state point of the mixed air cannot coincide with the heat-humidity ratio line, the state point of the mixed air is heated to the heat-humidity ratio line to meet the needs of load changes. At the same time, analog electric control valves are set in the primary and secondary return air ducts to adjust the air volume according to load changes, thereby maximizing energy savings.

[0014] The present invention provides a secondary return air air conditioning system with an adjustable reheat ratio, which has the following energy-saving effects: it avoids most of the cold and heat offset phenomena of the existing primary return air air conditioning system, can replace the existing primary return air system with a reheater, saves cooling and reheating heat in the cooling operation conditions in summer and transition seasons, and has a good energy-saving effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the present invention.

[0016] Figure 2 This is the air treatment enthalpy-humidity diagram when the heat and humidity ratio is large according to the present invention.

[0017] Figure 3 This is the air treatment enthalpy-humidity diagram when the heat and humidity ratio is small according to the present invention.

[0018] Figure 4 This is the air treatment enthalpy-humidity diagram when the reheater of the present invention is located before the secondary return air mixing section and the heat and humidity are relatively small. DETAILED DESCRIPTION

[0019] In order to make the technical solutions, features and effects of the present invention more clear and easier to implement, the present invention is further described below.

[0020] The secondary return air conditioning system with adjustable reheat ratio is characterized by: Figure 1, including an air handling unit 1, a service room 2, a supply air duct 3, a return air duct 4, and a fresh air duct 5. The air handling unit includes a primary return air mixing section a, a surface cooling section b, a secondary return air mixing section c, a reheat section d, and a fan section e. The return air duct is respectively connected to the primary return air mixing section and the secondary return air mixing section of the air handling unit. The primary return air duct is provided with an analog electric regulating valve 6, and the secondary return air duct is provided with an analog electric regulating valve 7.

[0021] The following examples illustrate the implementation manner of the present invention. For example, a clean air-conditioning system is designed as follows: the system includes an air handling unit, a service room (clean room), an air supply duct, a return air duct, and a fresh air duct. The air handling unit section setting includes a fresh air primary return air mixing section, a primary filtration section, a surface cooling and heating section, a secondary return air mixing section, a reheat section, a humidification section, a fan flow equalization section, a medium efficiency filtration section, and an air outlet section. The primary return air duct is provided with an analog electric regulating valve, the secondary return air duct is provided with an analog electric regulating valve, and a high-efficiency filtration air supply outlet is provided at the end of the supply air duct.

[0022] The air treatment process in the summer cooling condition when the heat and humidity are relatively high is as follows: the fresh air is mixed with the indoor primary return air, filtered through the primary filter, cooled by the surface cooler, and then mixed with the indoor secondary return air to the air supply state point, and then sent into the room after medium-efficiency filtration and high-efficiency filtration through the fan.

[0023] The air treatment process for cooling conditions in summer and transitional seasons when the heat and humidity ratio is relatively low is as follows: fresh air is mixed with indoor primary return air, filtered through primary efficiency, cooled by surface cooler, mixed with indoor secondary return air, and then heated to the intersection with the indoor heat and humidity ratio line, and then sent into the room through a fan after medium efficiency filtration and high efficiency filtration.

[0024] The winter air treatment process is as follows: fresh air is mixed with indoor return air, filtered through primary efficiency, heated by heater, humidified by humidifier, filtered through fan and then filtered through medium efficiency and high efficiency before being sent into the room.

[0025] Temperature and humidity sensors are installed indoors or in the return air main pipeline to adjust the opening of the primary and secondary return air electric valves according to the room temperature and humidity to meet the needs of load changes.

[0026] The above example is a specific implementation case of the present invention. There are many implementation plans of the present invention. Any technical solutions that are identical or equivalent to the contents described in the claims of the present invention are within the scope of protection of the present invention.

Claims

1. A secondary return air conditioning system with an adjustable reheater ratio, characterized by: It includes an air handling unit, a service room, an air supply duct, a return air duct, and a fresh air duct. The air handling unit includes a primary return air mixing section, a surface cooling section, a secondary return air mixing section, a reheat section, and a fan section. The return air duct is respectively connected to the primary return air mixing section and the secondary return air mixing section of the air handling unit. The primary return air duct is provided with an analog electric regulating valve, and the secondary return air duct is provided with an analog electric regulating valve. The opening condition of the reheat section heater is that it is turned on when the heat and humidity ratio is small and turned off when the heat and humidity ratio is large; the large or small heat and humidity ratio refers to the intersection temperature of the heat and humidity ratio line and the saturated relative humidity line, T L The surface cooling section can cool the air it processes to T L When the heat and humidity are relatively high, it is impossible to cool to T L Or when the heat-humidity ratio line has no intersection with the saturated relative humidity line, the heat-humidity ratio is small; The air treatment process when the heat and humidity ratio is large is process one, in which the fresh air is mixed with the indoor primary return air, cooled by the surface cooler, and then mixed with the indoor secondary return air to the air supply state point and sent into the room; The air treatment process when the heat and humidity ratio is small is process two or process three. The process two is that the fresh air is mixed with the indoor primary return air, cooled by the surface cooler, mixed with the indoor secondary return air, and then heated to the intersection of the indoor heat and humidity ratio line, that is, the air supply state point, and then sent into the room. The process three is: the fresh air is mixed with the indoor primary return air, cooled by the surface cooler, heated to the intersection of the indoor heat and humidity ratio line, and then mixed with the indoor secondary return air to the air supply state point, and then sent into the room. A temperature and humidity sensor is installed in the service room or in the return air main pipeline, and the opening of the analog electric regulating valve of the primary and secondary return air is adjusted according to the room temperature and humidity to meet the needs of load changes.

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