## 4 Temperature and Humidity Control System
### Hardware Components of Temperature and Humidity Control System  
The hardware of temperature and humidity control system includes (Figure 8): (1) constant-temperature water tank; (2) Recirculating heating/refrigerating machine; (3) Humidifier; (4) Recirculating dehumidifier; (5) Heating/cooling water supply (intake) pipes and water return pipes; (6) Heat transfer copper tubes; (7) Humidification/dehumidification steam pipes; (8) Industrial control computer and display; (9) Temperature and humidity transducer (eight transducers are arranged to measure the temperature and humidity distribution in the enclosed chamber); and (10) Temperature and humidity control cabinet. Figure 9 shows a photograph of the control cabinet and devices of the temperature and humidity control system.  
The temperature and humidity control system is in fact associated to some extent with the mechanical structure system, at least with some components, e.g., the heat-conducting inner wall of the enclosed chamber, the heat insulation layer, the heating (cooling) water intake/return pipes, and the heat transfer copper tubes, etc. Of course, theses components can also be classified into temperature and humidity control system. The outer wall of the enclosed chamber is a 4 mm thick steel plate, serving to stabilize and maintain the shape of the enclosed chamber. The inner wall of the enclosed chamber is a 3 mm thick aluminum plate with copper tubes of an inner diameter of 10 mm and a wall thickness of 1 mm laid on its outer surface. Hot (cold) water circulates through these copper tubes to heat (or cool) the inner wall, which in turn affects the air temperature within the enclosed chamber (seeFigure 1). A rubber and plastic aggregate insulation layer of 72 mm thickness is placed between the inner and outer walls to prevent heat leakage.  
The constant-temperature water tank was developed in China. The tank has an operating temperature range of ambient atmospheric (room) temperature to 98 \({}^{\circ}\)C and a temperature control accuracy of \(\pm\)0.3 \({}^{\circ}\)C. The recirculating heating/ refrigerating machine produced by German company JULABO (located at Seelbach, Germany) was selected, which can heat or refrigerate circulating water and has a temperature range of \(-\)35 \({}^{\circ}\)C to 200 \({}^{\circ}\)C and a temperature stability of \(\pm\)0.01 \({}^{\circ}\)C. The RS electrothermal humidifier from Swiss Cond air company (located at Zurich, Switzerland) was adopted, which has a humidity range from10%RH to 90%RH and a stable control accuracy of \(\pm\)3%RH. The dehumidifier is the Air Blue AT400, which was produced by Sweden company SWEGON  
Figure 8: Hardware arrangement of temperature and humidity control system in conception design. 1. Temperature and humidity control cabinet. 2. Constant-temperature water tank. 3. Recirculating heating/refrigerating machine. 4. Humidifier. 5. Recirculating dehumidifier. 6. Water return pipe. 7. Humidification/dehumidification steam pipe. 8. Enclosed chamber. 9. Water intake pipe.  
Figure 9: Control cabinet and devices of temperature and humidity control system. 1. Temperature and humidity control cabinet; 2. Constant-temperature water tank; 3. Recirculating heating/refrigerating machine; 4. Humidifier; 5. Recirculating dehumidifier; 6. Humidification/dehumidification steam pipes; 7. Water intake pipes; 8. Enclosed chamber; 9. Water return pipes.  
and has a working humidity range from 0 to 100%RH with a dehumidification capacity of up to 1.6 kg/h. The temperature and humidity transducer utilized was produced by Beijing HuakongXingye Technology Development Co., Ltd. (located in Beijing, China), it integrates Swiss SENSIRION (located in Staefa, Switzerland) high precision temperature and humidity sensor, has a temperature measurement range from \(-\)40 \({}^{\circ}\)C to 85 \({}^{\circ}\)C, a humidity measurement range from 0 to 100%RH, a temperature measurement accuracy of \(\pm\)0.3 \({}^{\circ}\)C, and a humidity measurement accuracy of \(\pm\)2.0%RH.