The rapidly developing subway system in southern China has chosen Vaisala temperature and humidity transmitters for its air conditioning system.

Shenzhen is a city in southern China with nearly 9 million residents. It is located in the north of Hong Kong and has developed from a small border town with a population of only 30000 to a modern metropolis in less than 30 years, becoming one of the developed cities. Today, Shenzhen is an important financial, high-tech, and manufacturing center in the southern inland of China.

Shenzhen has a rapidly developing subway system, owned and operated by Shenzhen Metro Corporation. Its subway was built in 2001, and the first two lines were opened to the public at the end of December 2004, making Shenzhen the fifth city in Chinese Mainland with a subway.

The initial two lines were Line 1 and Line 4, with a total of 19 stations and a total track length of 21.8 kilometers. Afterwards, these two lines were further extended, with a total length of 177 kilometers.

Comfortable environment and optimized energy consumption:

Temperature and humidity transmitters are used in the Building Automation System (BAS) of subway buildings to monitor the environmental and energy consumption status of each station. The measurement results can help control the ventilation and air conditioning conditions, provide passengers with a comfortable riding environment, and provide subway operators with a means to optimize energy consumption.

In Shenzhen Metro, each station is usually equipped with 30 wall mounted transmitters and 15 transmitters installed in pipelines. The equipment room platform uses wall mounted transmitters, while the replacement air conditioning unit (MAU) uses transmitters installed in pipelines. MAU is an air conditioning device that inhales outdoor air and regulates it to maintain its freshness. It can also prevent negative pressure indoors by expelling stale air.

The high humidity climate poses a significant challenge to ventilation conditions

Shenzhen is almost located between longitude 113 ° 46 '-114 ° 37' east and latitude 22 ° 27 '-22 ° 52' north on the Tropic of Cancer.

The climate in Shenzhen is a tropical oceanic monsoon climate, with an average temperature of 24 degrees Celsius and humidity ranging from 40% to 85%. At the highest temperature, the humidity level may exceed 90%. No matter the temperature conditions, people will always feel uncomfortable in high humidity environments

Suitable. When the humidity is too high, condensation may occur on the surface of the cooler, exacerbating the wear and tear of heating and ventilation equipment, especially during the cooling process. Over time, high humidity environments may corrode equipment, thereby increasing maintenance requirements.

Condensation is also a problem for measuring equipment as it can affect measurement stability. Shenzhen Metro initially installed a commercial temperature and humidity transmitter on Line 1 and Line 4, but due to high humidity climate conditions, most of the transmitters were damaged, and the recorded temperature measurement values drifted around 2 degrees Celsius, while the humidity measurement values drifted up to 10% -20%.

Search for accurate and stable measurement values:

In order to improve performance, Shenzhen Metro sought assistance from Vaisala, in addition to other suppliers, to provide samples of temperature and humidity transmitters for testing. Vaisala's products include multiple HUMICAPs ® Relative humidity sensors are capable of recovering from condensation without affecting measurement accuracy or long-term stability.

The Vaisala transmitter operates normally according to its specifications and provides accurate and stable measurement values. In addition, a previous subway project in Guangzhou has also been proven to be a good reference for validation testing based on real experience. Guangzhou and Shenzhen are 120 kilometers apart and have similar weather conditions, so Guangzhou's experience of using Vaisala transmitters in the same application also encourages Shenzhen Metro to continue using this equipment.

Thousands of transmitters are installed in complex systems:

Hundreds of Vaisala INTERCAPs are installed on multiple lines of the Shenzhen Metro ® Temperature and humidity transmitters (specially installed with HMW88 and HMD82). Overall, there are nearly 1500 Vaisala HUMICAPs installed along Line 2 ® Temperature and humidity transmitter.

The number of required transmitters indicates the complexity of the subway construction automation system. Multiple variables need to work seamlessly simultaneously. As part of the overall system, temperature and humidity measurements can help optimize ride conditions and improve passenger comfort. From the perspective of system performance, accurate and stable measurement values can also reduce overall maintenance costs, extend calibration cycles, reduce the frequency of transmitter damage and replacement, and improve operational efficiency through stricter operating conditions.