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As people become more and more concerned about health problems, the level of care in hospitals has improved greatly. The hospital installed HVAC system to improve the comfort of the whole hospital. It also provides a comfortable treatment and rehabilitation environment for hospital workers and patients. Considering the operating cost of the hospital, this paper will start from the HVAC function of the hospital, analyze the unreasonable factors and design principles of hospital HVAC. Then put forward the hospital HVAC system countermeasures, only for reference.

 Part 01  The role of HVAC in hospital 

1、Important measures to prevent cross infection

A hospital is a public place to gather and accommodate all kinds of patients. In addition, the patient's own immunity is relatively low compared to normal people. At the same time, the air in the hospital is filled with various irritant gases such as disinfectant. Medical devices can also produce substances that are harmful to human health. Therefore, hospital buildings should be designed from the source to prevent cross-infection. Especially in this special place, the HVAC system should be segmented according to the actual functions and nature of the hospital. It is necessary to reasonably control the pressure difference according to different functions, control the flow direction of the air, and choose the best air flow organization. For example, the ventilation design of the operating room is positive pressure to ensure that the air flow out of the operating room. In short, the basic principle is to control the pressure difference, allow air circulation, reduce the possibility of cross-infection, and provide the best medical environment.

2、Hospital HVAC is a powerful condition for treatment and rehabilitation

A hospital is a place where medical treatment and care are provided to the sick. There are special needs for the medical treatment and rehabilitation of patients, such as temperature, humidity, etc. These conditions play an important auxiliary role in the recovery of patients. For example, hot, humid temperatures can help burn patients recover more quickly. For heart disease patients with poor physical performance and abnormal heat dissipation, due to insufficient blood circulation, air conditioning will help to help patients dissipate heat. Therefore, hospital HVAC is not only to improve the comfort of the hospital. From the perspective of medical treatment and rehabilitation, the HVAC in the hospital provides a strong guarantee for treatment and rehabilitation.

3、HVAC is an important guarantee for the normal operation of hospital

With the improvement of medical technology, medical equipment and medical management level, a variety of equipment has a large heat dissipation. In the process of operation, it will also release a lot of gases, smoke and other substances, which will bring great difficulties to medical air management. Therefore, the hospital in the management, according to the classification of equipment management. For large equipment to establish an independent machine room. For special equipment, the appropriate temperature and humidity should be set according to the requirements of the equipment to improve the accuracy and stability of the equipment. In addition, some special equipment in the hospital will remove harmful gases. Many equipment in the hospital have special requirements for temperature and humidity. For example: general X-ray room, CT room, MRI machine department and so on. Therefore, HVAC is an important guarantee for the normal operation of the hospital.

 Part 02  Energy-saving design principle of hospital HVAC 

In the process of discussing hospital HVAC energy saving measures, we should have some understanding of hospital HVAC design standards. Especially in the process of modern hospital construction, the energy-saving design principle of hospital HVAC should be strictly followed. Hospital HVAC energy-saving design principles to comply with: low carbon, energy saving, recyclable principles.

a. The principle of low carbon is mainly to reduce carbon dioxide emissions. Reduce carbon dioxide pollution to the air and environment. Therefore, this puts forward higher requirements for the technical personnel of air conditioning design. It is necessary to strictly control the carbon dioxide emission of the air conditioning system, and improve the treatment of the generated carbon dioxide, and improve the exhaust design level.

b. The principle of energy conservation is to reduce the loss of energy while ensuring comfort. To find a balance between comfort and energy saving, the principle of energy saving should be consistently tested in the HVAC construction process.

c. The recyclability principle is primarily a principle. In the design, it is necessary to consider the recovery of the air conditioning unit preheating fresh air and do a good job of heat recovery treatment. All these can reduce the operating cost of air conditioning, reduce energy consumption, and achieve energy saving.

 Part 03  Energy-saving measures of hospital HVAC system 

1、Choose a reasonable cooling and heat source scheme

As we all know, the various departments of the hospital according to the difference in the flow of people, the time period of high frequency of air conditioning is not the same. In addition to meeting the maximum load, for the minimum load, it is necessary to maintain a high energy efficiency of the heat and cold source. For example, wards, emergency rooms and operating rooms are used more frequently at night. But at night in the transition season, when the minimum load occurs, sometimes only a few operating rooms may be using air conditioning. In general, in this case, the hospital usually uses an independent air source heat pump unit as the cold and heat source of the transition season air conditioning. Therefore, the load rate of equipment such as maximum, minimum and special periods should be reasonably analyzed. Through the overall planning of the analysis results, the hospital HVAC system with high efficiency and strong flexibility is created in line with the characteristics of the hospital.

2、Reasonable fresh air volume regulation

The hospital's HVAC system is designed to prevent cross-infection among the hospital population. Then the intake of fresh air into the air conditioning system is to improve the indoor air quality of the hospital. So how to set the size of the fresh air volume? The premise of regulating the fresh air volume in the new hospital is to meet the relevant health requirements. In the non-crowded or peak time points, the fresh air volume should be appropriately reduced to meet the relevant health requirements, but also to achieve the effect of energy saving and emission reduction. It is necessary to emphasize that the filtration and purification device of the fresh air system should be regularly maintained and replaced to ensure the normal operation of the air conditioning system. Keeping the flow resistance low can reduce the loss of energy consumption and keep the air conditioning equipment working efficiently. In addition, according to the latest small air volume adjustment of civil buildings, the minimum fresh air volume per person in the outpatient and general wards of the hospital is 17m³/h.

3、Reduce energy consumption during air and water transport

Shaft power calculation formula of fan and pump：N=LP/η。

There are three factors that affect power consumption (N) :

a.Flow（L）；

b.Pressure（P）；

c.Efficiency of fan and pump（η）。

It can be done by reducing the flow (L), usually by increasing the air supply and water supply temperature difference. The large temperature difference can not only reduce the energy consumption of the conveying process, but also reduce the section of the pipeline and reduce the cost of the pipeline. Of course, the temperature difference is too large will also affect the performance of the HVAC equipment, so that the cold source energy consumption increases. Therefore, a reasonable temperature difference should be selected among the total energy consumption, conveying energy consumption and cold source energy consumption of the system. To reduce the system resistance (P), low flow rate can be selected.

4、Daily air conditioning system maintenance work

In the process of normal operation of the air conditioner, if the daily maintenance work is not done, the filter device and tuyere of the air conditioner are cleaned on time, which will increase the ventilation resistance, thereby reducing the normal operation efficiency of the air conditioning system. If small damaged parts are found, they should be updated in time to avoid causing greater failures. Therefore, doing a good job of system maintenance management helps to increase the service life of air conditioning systems, and can reduce the failure rate of equipment, save maintenance costs, and ensure the normal operation of equipment. In particular, it should be noted that the design and construction of the air conditioning system in the early stage is perfect, but in the normal work of Nissan, the maintenance work is not carried out in accordance with the equipment maintenance regulations, or the maintenance personnel are not conscientious, and the expected effect of energy saving can not be achieved.

5、Application of renewable energy in HVAC

With the increase of public environmental awareness and attention to environmental problems. If conditions permit, HVAC applications in renewable energy can be selected.

At present, the applications in this area on the market are:

(a) Utilization of solar energy;

(b) The use of natural wind;

(c)  Utilization of groundwater;

(d) Utilization of soil energy;

(e) Utilization of wind and ocean energy.

Hvac system is used more and more widely in hospital. In the actual management process of the hospital, the HVAC system should be designed from the source. In line with the principle of energy saving, emission reduction and environmental protection, various measures should be taken to reduce the operating costs of air conditioning systems. Each hospital should plan the air conditioning supply of each functional area according to its actual situation, and reasonably allocate the air conditioning use during the peak and trough of air conditioning. Consider the multi-energy combination operation mode, and truly achieve energy conservation and emission reduction. To provide a comfortable and healthy environment for hospital workers and patients.