Since the promulgation and implementation of Building Technical Specification for Hospital Clean Operating Department (GB50333-2002), the construction of clean operating room has entered a standardized track. Clean operating room project is a system engineering, the core of which is clean air conditioning project. In the clean air conditioning system, fresh air has a leading position. This paper mainly introduces the understanding of air conditioning, especially the fresh air of clean air conditioning.
Key word
Clean operating room operating room cleaning system fresh air system clean air conditioning system
Fresh air is the need of breathing in operating room. Maintaining CO2 concentration in a certain range is the need of compensating exhaust air and keeping indoor pressure difference. It is the cold source of lowering indoor temperature in winter, the source of 90% of system particles, and the source of humidification in winter and dehumidification in summer.
I. Fresh air volume required for indoor breathing
With the emission of greenhouse gases, atmospheric CO2 concentration has reached 376 ppm from 315 ppm in the middle of the last century, and increased by nearly 20% in 50 years.
Studies have shown that people feel good when CO2 concentration is 700-1000 ppm; they feel uncomfortable when CO2 concentration reaches 1500 ppm; and headache and other symptoms when CO2 concentration reaches 3000 ppm.
The human body emits about 20L of CO2 per hour. If indoor CO2 concentration is to be maintained at 700-1000ppm, fresh air volume is required:
Q=Q1/(Cv1-Cv2)*1000000
= 0.02/(700-376)*1000000
= 61m3/h
In the formula:
Q - Fresh air volume per person per hour, m3/h;
Q1 - The amount of CO2 discharged by human body per hour, m3/h;
Cv1 - Maintain indoor CO2 concentration, ppm;
Cv2 - fresh air CO2 concentration, ppm.
The above theoretical calculation also proves that it is appropriate to stipulate 60 m3 per person per hour in GB50333-2002 of Technical Specification for Construction of Hospital Clean Surgery Department.
According to the dynamic measurement of CO2 concentration in the operating room of a hospital in Beijing, 800 ppm also shows that the amount of CO2 specified in the specification is more appropriate.
2. Fresh air volume required to compensate exhaust air and maintain indoor pressure difference
The fresh air required to maintain positive indoor pressure is equal to the sum of air leakage and organized exhaust of the whole system (including interior decoration and air conditioning systems), that is, the fresh air supply is equal to the leakage of the system.
(1) Main Components of Air Leakage in Decorative Surface Layer
1. Operating room door
Clean operating rooms are usually equipped with automatic translation doors and manual translation doors (manual translation doors), which should be air-tight doors, but do not need special sealing, because the air escaping from the operating room to the corridors on both sides is clean air, whether in terms of cleanliness or temperature and humidity, it is advantageous.
2. Decoration of medical equipment
For equipment cabinets, gas terminal boxes and power socket boxes connected with ceiling or clamping wall, sealant should be used to ensure complete sealing with ceiling surface, especially for gas terminal boxes and bottom boxes of power socket boxes with pipeline holes, which are particularly easy to miss.
3. Gaps left over from decoration
The decorative surface itself needs to be sealed. The shadowless lamp, suspension tower opening, lamp belt hole, camera opening and speaker hole should be sealed.
4. Fire Fighting Equipment

In clean corridors and corridors, there are many kinds of work with fire protection, water supply and drainage, and their joint surfaces should be sealed, such as the sealing in hydrant box, the sealing of sprinkler head, the sealing of a large number of fire doors in pipe wells, and the sealing of clean windows. In particular, the number of fire doors in pipe wells is large and the air leakage is alarming. Special attention should be paid to them.

(2) Major components of air leakage in air conditioning systems
1. Air duct system
It can be said that the air duct system is a big leak, if the air duct system leaks small, especially closed, positive pressure is easy to adjust; if the air duct system is not closed, it will bring great trouble to debuggers. In the process of air duct operation, the finished air duct shall not have defects such as distortion, distortion, cracking, hole, flange falling off, opening and welding, leakage riveting, etc. Special attention should be paid to the sealing of the air duct bite, especially the sealing of the three-way and four-way joints, which generally adopts internal sealing; in the flanging corner of air duct in France, there are leakage points, which should be applied. Sealant treatment; Core-pulling rivets should be fully sealed and sealed at rivets.
2. Manufacturing and Installation of Air Parts
For air components, air leakage can not be ignored. For the sealing of all kinds of valve parts, it should be required when purchasing, the valve body should adopt the product of integral welding surface spraying treatment, the sealing measures should be taken at the valve shaft, the flange of the valve should be flat to ensure no air leakage after the use of sealing gasket; the air leakage of muffler should not be neglected, the main reason is that a lot of air leakage is used in the production. Rivet, there are many possible air leakage points.
3. Purification Air Conditioner
For purification air conditioning units, it is necessary to select special purification air conditioning units with good quality. The sealing degree between panels of special purification air conditioning units is much higher than that of general air conditioning units, and the air leakage rate will certainly be much smaller. Air leakage mainly occurs at the open door plate of the positive pressure section and the coil pipe nozzle of the positive pressure section. Effective sealing should be done.
Air leakage simulation calculation:
(1) Air leakage in decorative parts
Q1 = 3600 F
= 3600 x 0.4 x 0.05 x 3.65
= 57m3/h
In the above formula, the flow system takes 0.4;
Room air leakage area F, door 6m *0.005m, other seams 40m *0.0005m;
The positive pressure value is 8 Pa.
The air density is 1.2.
(2) Air leakage in air conditioning system
According to the specifications, the air leakage of air duct and air conditioning unit is about 2%. If it is a class II operating room, the total air leakage is 4000 m3/h and 160 m3/h.
Total fresh air = total leakage air
= Decoration system air leakage + air conditioning system air leakage + organized exhaust
= 57+160+583
= 800 m3/h
The fresh air quantity in the upper style is the minimum fresh air quantity standard in the Building Technical Specification for Hospital Clean Operating Department (GB50333-2002). The design of fresh air volume is based on the calculation amount of fresh air exchange times, the fresh air volume required to ensure the breathing of personnel and the fresh air required to ensure positive indoor pressure. The maximum of these three values should be taken as the design fresh air volume, but should not be lower than the minimum values of 1000 m3/h in the national standard I operating room, 800 m3/h in the II and III operating room and 600 m3/h in the IV operating room. Ask.
However, in engineering practice, most of the organized displacement of Class II operating room is 200-300 m3/h, not 583 m3/h in the upper style. In the case of obvious decorative air leakage, relatively hidden air leakage may account for a large proportion. If the quality is not paid attention to during construction and the air leakage in ducts is too large to guarantee the positive pressure in the room, it may be compensated by increasing the fresh air volume. Once the fresh air volume increases, a series of energy consumption increases, such as dehumidification in summer, humidification in winter, and the increase of the replacement frequency of filters, etc.
These should arouse our attention.
3. Fresh air is the cold source of reducing indoor temperature in winter
In winter, the whole hospital needs heating, including the operation area. The heating energy consumption is mainly responsible for fresh air and maintenance structure load. For the general ward and office, the main load is maintenance structure. For the operation department, besides the external corridor needs heating, the inner structure load is often very small, plus the fan motor. Conversion heat, operating room medical staff, lighting heat dissipation, medical equipment heat dissipation and so on, the whole system needs cold source to maintain the operating room temperature. At this time, the cold source should be fresh air. If the fresh air volume is insufficient or the preheating degree of fresh air is too high, the fresh air will lose this function. It may be mistaken to think that refrigeration is necessary to ensure indoor temperature in winter. Of course, due to the unreasonable heating coil and control configuration, the indoor temperature rises out of control. There are many reasons for the rise of operating room temperature in winter, but adequate and suitable fresh air at low temperature is the biggest factor to ensure the operating room temperature. So how many degrees is the outdoor temperature suitable in winter?
This article is for the full text original appearance without installing PDF browser users, please download and install the original full text of winter fresh air preheating and how much is related to the system design and configuration. In terms of operating room cooling alone, the lower the temperature, the better. If the outdoor fresh air does not preheat directly into the circulating unit system in winter, it will be well neutralized with the indoor return air, and the indoor temperature control will be free. Whether the fresh air without preheating will threaten the coils in the cooling coils of fresh air meters and circulating units will be a matter to be considered comprehensively.
Generally, when fresh air is one to many, it should be subcooled and dehumidified. At this time, large rows of surface cooling coils are needed in fresh air units. This coil needs to be protected in winter, that is to say, fresh air needs to be preheated. The preheating temperature varies according to the size and grade of the operating room. According to practice, it is more appropriate to control the temperature between 5 and 16 degrees centigrade.
4. Fresh air is the source of 90% of the particles in the system.
According to the research, 90% of the particles in the whole system come from fresh air.
At present, the national average atmospheric dust concentration is about 0.3 mg/m3.
If particulate matter in fresh air can be filtered out at the source, it will bring benefits to the operation of the whole system. The following measures can be taken:
(1) Fresh air must be filtered at three levels
First-class crude effect, second-class intermediate effect and third-class sub-efficiency. And three-stage filtration should be continuously arranged at the fresh air inlet to avoid contamination of pipes and components.
(2) Use of products with automatic cleaning function
In order to solve the problems of easy blockage of fresh air and heavy management work, products with automatic cleaning function have come out. The time of automatic cleaning can be set according to local environmental conditions. It can be done once a day or three days. The filter can be repeatedly cleaned and used, which not only achieves the purpose of cleaning the filter, but also saves the cost. Material, that's too convenient.
Especially the primary filter of fresh air is the most easily polluted. Products with automatic cleaning function should be used to reduce the investment and management cost of replacement materials.
(3) The surface wind speed of fresh air filters at all levels is as low as possible.
That is to say, the filter area is as large as possible. How much is it? According to practice, when the operating air volume is 0.5 times of the rated air volume, that is to say, the filter area is doubled, and the running time will be more than four times of the rated operating time, which greatly prolongs the service life of the filter. It is suggested that the operating air volume of filters at all levels is less than the rated air volume of filters, especially the coarse filter of fresh air.
5. Fresh air is the source of winter humidification in the whole system.
Most areas in China need humidification in winter. Generally, the air vapor content in winter is 1~2g/m3, which is different from the indoor humidity requirement. Therefore, the fresh air in the recharge system needs to be humidified. Generally, 7 g of water is needed for fresh air volume per m3/h. If the fresh air volume is increased, the humidification volume should be increased accordingly.
6. Fresh wind is the source of dehumidification in summer
Except for Xinjiang and other areas, most areas in China need dehumidification in summer.
In order to meet the requirement of humidity in the operating room, the traditional design is to treat the outdoor air on the isoenthalpy line of the indoor state point, then mix it with the indoor state point, and then treat it with the purifying unit at the intersection of the ISOD line and 95% of the supply state point, and then reheat it to reach the supply state point, as shown in Figure 1.
If the outdoor fresh air is directly treated to dew point temperature of 13 C, fresh air bears all indoor heat and humidity loads, and indoor return air is mixed with fresh air. According to specific conditions, it needs heating or not heating to reach the supply air state point, and then it is sent into the indoor, as shown in Figure 2.
The new air volume is L, the return air volume is L, Q1 is the total cooling capacity of the original model, and Q2 is the total cooling capacity of the existing model.
It can be seen from the above that the total cooling capacity of the fresh air supercooling treatment scheme is less than that of the traditional scheme. This part of the cooling capacity is borne by the purification unit, and then heated by the subsequent reheating equipment, resulting in energy offset waste. This part wastes about 35% of the total energy.
Concluding remarks
Fresh air is the source of the whole clean system. To some extent, it bears the great responsibility of whether the clean air-conditioning system can run well for a long time. We should fully understand it, understand it, give full play to it and run it well, so that it can contribute to the whole clean system.