Last Updated on October 28, 2021 by Shawn Lee
This hospital is a third-class first-class hospital located in Shanghai. It mainly consists of nine buildings, including ward building, medical technology building, outpatient and emergency building, rehabilitation building and administrative office building. Among them, the air-conditioning system of the ward building, which needs to supply domestic hot water, cool in summer and heat in winter, runs 24 hours a day, and its energy consumption per unit area is high.
Before the renovation, the supply of air conditioning and domestic hot water in the hospital came from oil-fired boilers and steam lithium bromide absorption chillers in the energy center. In summer, the steam generated by the oil-fired boiler is supplied to the lithium bromide chiller for refrigeration, and in winter, the oil-fired boiler provides steam, and after heat exchange, it provides hot water for heating of the air-conditioning system; Steam generated by oil-fired boiler is also used as heat source for domestic hot water throughout the year.
General situation and reconstruction scheme of hospital energy center
The main energy-consuming equipment of the hospital’s energy center are lithium bromide absorption chillers, oil-fired boilers, water pumps, cooling towers and air treatment systems of central air conditioners, etc. The energy consumed is mainly electricity and diesel oil. In recent years, due to the comprehensive influence of fuel price rising year by year, equipment efficiency decreasing and transportation system efficiency decreasing, the operation and maintenance cost of HVAC system has also increased year by year.
To reduce the energy cost of hospital operation. In this hospital, the air conditioning cold and heat source system and domestic hot water system of three buildings A, B and C (all inpatient wards with a total building area of 29,198 m) were reformed:
Two air source heat pump units were used to replace the two steam absorption lithium bromide units in the original A building. Two screw water-cooled chillers in the original B building and one screw water-cooled chiller in the original C building are used as cooling sources in summer. These two air-source heat pump units operate in winter to replace the steam heating of the original oil-fired boiler.
In addition, two air source heat pump hot water units are set up to produce domestic hot water all year round instead of steam heat exchange produced by the original oil-fired boiler to produce hot water.
Application of air source heat pump system
In this energy-saving transformation, two air-source heat pump units are used to provide cooling in summer and heating in winter. The other two air-source heat pump hot water units can not only produce domestic hot water, but also provide cooling capacity for air-conditioning system in summer and transition season.
Table 1 Performance parameters of air source heat pump unit
|Air source heat pump unit||2||1070/1124||206/290|
|Air source heat pump hot water unit||2||366/454||102|
Cold and heat source system for air conditioning
The air source heat pump unit adopts twin-screw compressor, which has the characteristics of small vibration, low noise and high volumetric efficiency, and can adjust the energy output control of the compressor with the change of load. Water-side heat exchanger is a high-efficiency shell-and-tube heat exchanger, which adopts high-efficiency seamless copper tube with internal thread and external spiral to enhance the heat transfer effect The air-side heat exchanger adopts V-shaped coil design, which makes the surface wind speed of the coil uniform, effectively improves the air distribution and improves the heat dissipation efficiency. A plurality of compressors are arranged in parallel, wherein each compressor is provided with an independent refrigerant circuit, which can form an independent refrigeration or heating cycle and improve the reliability of the system.
Heat source system for domestic hot water
Domestic hot water uses air source heat pump hot water unit, which can provide cold water for air conditioning and domestic hot water at the same time in the cooling season. The unit is not equipped with electric heating device, and provides domestic hot water in the outdoor environment temperature range of-5℃ ~ 43℃, which can realize automatic switching of various operation modes
Energy saving monitoring system
The hospital did not install the energy itemized metering system originally, and the key energy-using equipment (two air-source heat pump units and two air-source heat pump hot water units) in this transformation were installed with metering meters, and the relevant departments were responsible for their safe operation. If the equipment runs abnormally, it can give an alarm in time.
- Compared with the form of steam boiler and lithium bromide chiller, the air source heat pump system is used to realize cooling and heating (hot water for air conditioning and domestic use). From the technical and economic point of view, its annual total energy consumption and operating cost are basically within the normal range, so it is feasible and worthy of recognition and promotion; However, it is necessary to design the cooling, heating and hot water supply system of the building as a whole, and calculate the balance of cold and heat.
- The combination of air-source heat pump hot water unit and air-source cold and hot water system is an effective means to realize energy saving, and there is room for optimization of its operation mode.
- When the outdoor temperature exceeds the design, the efficiency of the air source heat pump unit may be unsatisfactory, but it is necessary to comprehensively analyze the distribution of outdoor temperature throughout the year, and analyze and judge the technology and economy of the whole system from the time of cooling and heating (hot water for air conditioning and domestic use) throughout the year. It is not restricted by inefficient operation in local time, so as to realize economic operation throughout the year