Key points to consider in the construction of a constant temperature and humidity laboratory

I. Preliminary Planning

1. Determine Purpose and Requirements
   • Before constructing a constant temperature and humidity laboratory, it is necessary to clarify the purpose of the laboratory. For example, is it for testing electronic components, studying the stability of pharmaceuticals, or calibrating precision instruments? Different purposes have significantly different requirements for temperature and humidity control accuracy and fluctuation ranges.
   • Taking a pharmaceutical stability testing laboratory as an example, according to relevant regulations and the characteristics of the drugs, the temperature is generally required to be controlled at 25°C ± 2°C, and the relative humidity controlled at 60% ± 5%. For an aging testing laboratory for electronic chips, the temperature may need to be precise to 20°C ± 0.5°C, with relative humidity controlled at 40% ± 3%.
2. Site Selection and Spatial Layout
   • The site should be chosen away from heat sources, vibration sources, and pollution sources. Avoid direct sunlight, as the heat from sunlight can affect the stability of indoor temperature and humidity.
   • A reasonable spatial layout is crucial for a constant temperature and humidity laboratory. Different functional areas such as the experimental area, equipment area, and sample storage area should be planned according to the experimental process and equipment size. For example, in a constant temperature and humidity laboratory for material performance testing, a large universal material testing machine should be placed near the power source, while leaving enough space for placing the materials to be tested and storing the tested samples.

II. Building Structure and Enclosure System

1. Walls and Roof
   • Walls and roofs are important components of the laboratory's enclosure structure and need to have good thermal insulation performance. Materials with good insulation properties are usually used, such as expanded polystyrene foam boards (EPS), polyurethane foam boards (PU), or rock wool boards.
   • Taking PU foam boards as an example, they have a very low thermal conductivity, generally between 0.02 - 0.03 W/(m·K), effectively preventing the transfer of heat between indoors and outdoors. The thickness of the walls is determined based on the temperature and humidity requirements of the laboratory and the climate conditions of the area, generally around 100 - 200 mm.
   • The roof also needs to consider waterproofing and drainage design to prevent rainwater infiltration from affecting the indoor environment. A combination of double-layer waterproof membranes and drainage slopes can be used, with a drainage slope generally not less than 3%.
2. Floor
   • The floor should have moisture-proof, thermal insulation, and flat characteristics. A moisture-proof layer, such as polyethylene moisture-proof film, can be laid first, followed by pouring a concrete base, with insulation materials like expanded perlite added to the concrete.
   • For laboratories with special requirements, such as electronic laboratories that need to prevent static electricity, anti-static flooring should also be laid, with the surface resistivity of anti-static flooring generally between 10^6 - 10^9 Ω.

III. Air Conditioning and Ventilation System

1. Constant Temperature and Humidity Air Conditioning Unit
   • This is the core equipment for controlling the temperature and humidity of the laboratory. Choose a suitable air conditioning unit based on the scale of the laboratory and the temperature and humidity requirements. Air conditioning units come in two types: air-cooled and water-cooled.
   • Air-cooled air conditioning units are easy to install and do not require an additional cooling water system, but their cooling efficiency is relatively low. Water-cooled air conditioning units have high cooling efficiency but require auxiliary equipment such as cooling towers and cooling water pumps.
   • The cooling capacity, dehumidification capacity, and other parameters of the air conditioning unit should be calculated based on the thermal and moisture load of the laboratory. The thermal and moisture load includes factors such as equipment heat dissipation, personnel heat dissipation and moisture generation, and heat and moisture generated during experiments. For example, in a computer laboratory with 10 servers, each with a power of 500W, and assuming 5 people with a heat dissipation of 150W/person, along with heat dissipation from lighting and other equipment, the total thermal load can be calculated, and then a suitable cooling capacity air conditioning unit can be selected based on that load.
2. Ventilation System
   • The ventilation system is mainly to ensure the air quality in the laboratory. It can be divided into natural ventilation and mechanical ventilation. Natural ventilation relies on openings such as doors and windows for air exchange, but in a constant temperature and humidity laboratory, natural ventilation may affect the stability of temperature and humidity, so mechanical ventilation is mainly used.
   • The mechanical ventilation system includes air supply fans, exhaust fans, and ventilation ducts. The air supply and exhaust volumes should be determined based on the size of the laboratory space and the ventilation requirements of the experimental equipment. Ventilation ducts should be well insulated to prevent condensation during ventilation.

IV. Temperature and Humidity Monitoring and Control System

1. Sensors
   • Temperature and humidity sensors are key components of the monitoring system. Common temperature and humidity sensors include capacitive, resistive, and hygroscopic types. Capacitive temperature and humidity sensors have high accuracy and fast response, making them suitable for high-precision constant temperature and humidity laboratories.
   • Sensors should be reasonably distributed in various areas of the laboratory, generally installed near workbenches, around equipment, and in corners to accurately monitor the temperature and humidity conditions in different locations indoors.
2. Controller
   • The controller receives signals from the sensors and then controls the operation of the air conditioning unit and other equipment based on the set temperature and humidity parameters. The controller can use a PID (Proportional-Integral-Derivative) controller, which can make precise adjustments based on the deviation of temperature and humidity.
   • For example, when the temperature exceeds the set value, the controller will send a signal to increase the cooling capacity of the air conditioning unit; when the humidity is below the set value, the controller will control the humidifier to turn on. At the same time, the controller can also be connected to upper-level software for remote monitoring and data recording.

V. Power and Lighting System

1. Power System
   • The power system of a constant temperature and humidity laboratory must meet the power needs of the equipment and have sufficient backup power. Calculate the total power load based on the power and quantity of the equipment, and choose suitable distribution boxes and wire specifications.
   • Wires should use fireproof and moisture-proof cables, and grounding protection should be well done. For some equipment with high stability requirements, such as high-precision electronic instruments, an uninterruptible power supply (UPS) should also be configured to prevent sudden power outages from damaging the equipment.
2. Lighting System
   • The lighting system should choose lamps with low heat generation and high luminous efficiency. LED lamps are a relatively ideal choice, as they have high luminous efficiency and generate little heat, which will not significantly affect the indoor temperature and humidity.
   • The brightness of the lighting should meet the requirements of the experimental operation, while also considering the uniformity of the lighting. The uniformity of the lighting can be improved by reasonably arranging the lamps and using reflectors.

6. Interior Decoration and Equipment Installation

1. Interior Decoration
   • The materials used for the interior decoration of the laboratory should be chosen to minimize dust, static electricity, and chemical contamination. The walls can be coated with fireproof and mildew-resistant paint or clean panels, which have a smooth and flat surface, are easy to clean, and possess certain antibacterial properties.
   • The ceiling can use aluminum alloy ceiling panels or clean ceilings, which facilitate the installation of lighting and ventilation equipment. After the floor decoration is completed, a flatness test should be conducted to ensure the stability of equipment installation.
2. Equipment Installation
   • The installation of laboratory equipment should follow the equipment installation manual and the layout plan of the laboratory. For equipment that is sensitive to vibrations, measures should be taken to reduce vibrations, such as installing shock-absorbing pads or supports. After the equipment installation is completed, debugging and calibration should be performed to ensure that the equipment can operate normally in a constant temperature and humidity environment.

Building a constant temperature and humidity laboratory is a complex system project that requires comprehensive consideration of various aspects such as building structure, air conditioning and ventilation, temperature and humidity control, and electrical lighting, to ensure that the laboratory can meet specific temperature and humidity control requirements, providing a stable environment for experimental research and other work.